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Review Canola proteins: composition, extraction, functional properties, bioactivity, applications as a food ingredient and allergenicity e A practical and critical review Mohammed Aider a, * and Chockry Barbana b a Department of Food Engineering, Universit e Laval, Qu ebec, Qc, G1K 7P4, Canada (Tel.: D1 418 656 2131x4051; e-mail: [email protected]) b Tecnolog ıa y Bioqu ımica de los Alimentos, Facultad Veterinaria, Universidad de Zaragoza, C/ Miguel Servet 177, 50013 Zaragoza, Spain There is a well-recognized connection between the use of plant proteins in functional foods, nutraceuticals and other natural health products and health promotion and disease risk reduction. Plant proteins are largely used in the food in- dustry, and canola/rapeseed proteins are regarded as potential ingredients that may be used as food additives. In this review, the chemical composition (amino acids and protein fractions), production and isolation techniques, functional properties, al- lergenicity, food applications and potential uses of canola pro- teins for the production of bioactive compounds are highlighted. Introduction Canola/Rapeseed is an important oilseed crop in many countries and is considered to be the second most abundant source of edible oil in the world. Canola is the rapeseed va- riety which was developed in Canada. According to the United States Department of Agriculture, canola production exceeds 40 million metric tons per year (USDA, 2004). Canada is a world leader in the large-scale production of high quality canola varieties, which are characterized by low erucic acid (<2%) and glucosinolate (<30 lmol/g) con- tents (Ghodsvali, Khodaparast, Vosoughi, & Diosady, 2005). Canola seeds contain approximately 40% oil and 17e26% protein (Uppstrom, 1995). Canola meal, which is a by-product of canola oil extraction, is a highly rich raw material and contains up to 50% protein on a dry basis. The major protein constituents of canola meal are napin and cruciferin, which are storage proteins, and oleosin, which is a structural protein associated with the oil fraction (Uppstrom, 1995). This particularity makes canola protein a potential ingredient for use in the food industry. Many characteristics of canola protein are favorable for human nutrition. The amino acid composition of canola meal is well balanced and can be used for human nutrition (Ohlson & Anjou, 1979; Mariscal-Landin, Reis de Souza, Parra, Aguilera, & Mar, 2008). In addition, the protein ef- ficiency ratio of canola meal is 2.64, which is higher than that of soybean (2.19) (Delisle et al., 1984). Canola proteins have shown interesting and promising functional properties and could be potentially used in various food matrices (Khattab & Arntfield, 2009; Xu & Diosady, 1994a, 1994b). Some properties of canola proteins were comparable to those of casein and better than those of other plant proteins, such as soybean, pea, and wheat (Ghodsvali et al., 2005). However, the usefulness of canola protein ex- tracts is limited by the presence of some undesirable com- pounds, such as glucosinolates, phytates, and phenols, which are responsible for the toxic, antinutritional and undesirable coloration capacity of canola proteins. Also, * Corresponding author. 0924-2244/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.tifs.2010.11.002 Trends in Food Science & Technology 22 (2011) 21e39
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Trends in Food Science & Technology 22 (2011) 21e39


* Corresponding author.

0924-2244/$ - see front matter � 2010 Elsevier Ltd. All rights reserved.doi:10.1016/j.tifs.2010.11.002

Canola proteins:


extraction, functional



applications as a food

ingredient and

allergenicity e A

practical and critical


Mohammed Aidera,* and

Chockry Barbanab

aDepartment of Food Engineering, Universit�e Laval,

Qu�ebec, Qc, G1K 7P4, Canada

(Tel.: D1 418 656 2131x4051;e-mail: [email protected])

bTecnolog�ıa y Bioqu�ımica de los Alimentos, Facultad

Veterinaria, Universidad de Zaragoza, C/ Miguel

Servet 177, 50013 Zaragoza, Spain

There is a well-recognized connection between the use of

plant proteins in functional foods, nutraceuticals and other

natural health products and health promotion and disease

risk reduction. Plant proteins are largely used in the food in-

dustry, and canola/rapeseed proteins are regarded as potential

ingredients that may be used as food additives. In this review,

the chemical composition (amino acids and protein fractions),

production and isolation techniques, functional properties, al-

lergenicity, food applications and potential uses of canola pro-

teins for the production of bioactive compounds are


IntroductionCanola/Rapeseed is an important oilseed crop in many

countries and is considered to be the second most abundantsource of edible oil in the world. Canola is the rapeseed va-riety which was developed in Canada. According to theUnited States Department of Agriculture, canola productionexceeds 40 million metric tons per year (USDA, 2004).Canada is a world leader in the large-scale production ofhigh quality canola varieties, which are characterized bylow erucic acid (<2%) and glucosinolate (<30 lmol/g) con-tents (Ghodsvali, Khodaparast, Vosoughi, & Diosady,2005).

Canola seeds contain approximately 40% oil and17e26% protein (Uppstrom, 1995). Canola meal, whichis a by-product of canola oil extraction, is a highly richraw material and contains up to 50% protein on a dry basis.The major protein constituents of canola meal are napinand cruciferin, which are storage proteins, and oleosin,which is a structural protein associated with the oil fraction(Uppstrom, 1995). This particularity makes canola proteina potential ingredient for use in the food industry. Manycharacteristics of canola protein are favorable for humannutrition. The amino acid composition of canola meal iswell balanced and can be used for human nutrition(Ohlson & Anjou, 1979; Mariscal-Landin, Reis de Souza,Parra, Aguilera, & Mar, 2008). In addition, the protein ef-ficiency ratio of canola meal is 2.64, which is higher thanthat of soybean (2.19) (Delisle et al., 1984). Canolaproteins have shown interesting and promising functionalproperties and could be potentially used in various foodmatrices (Khattab & Arntfield, 2009; Xu & Diosady,1994a, 1994b). Some properties of canola proteins werecomparable to those of casein and better than those of otherplant proteins, such as soybean, pea, and wheat (Ghodsvaliet al., 2005). However, the usefulness of canola protein ex-tracts is limited by the presence of some undesirable com-pounds, such as glucosinolates, phytates, and phenols,which are responsible for the toxic, antinutritional andundesirable coloration capacity of canola proteins. Also,

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22 M. Aider, C. Barbana / Trends in Food Science & Technology 22 (2011) 21e39

canola meal contains approximately 20% (w/w) carbohy-drates, including soluble sugars (Lacki & Duvnjak, 1998).However, after protein extraction, the major part of thesesaccharides is eliminated. Efforts are focusing to developcanola protein products for food applications. Recently,Burcon NutraScience Corporation has announced that theDivision of Biotechnology and GRAS Notice Review ofthe Center for Food Safety and Applied Nutrition of theFDA has formally acknowledged receipt of Burcon’sGRAS notification for its canola protein ingredients.

The present review summarizes the chemical and struc-tural compositions of canola proteins, the processes usedfor canola protein extraction, the functional propertiesand examples of canola protein applications in differentfood matrices. The potential of use of canola proteins forthe production of bioactive peptides is also highlighted.

Chemical and structural compositionsAmino acid profile

The amino acid compositions of the canola protein iso-lates have been studied and reported by several researchers;these proteins are well balanced and show high glutamine,glutamic acid, arginine and leucine contents and lowamounts of sulfur-containing amino acids, which are prob-ably altered during the industrial oil extraction process(Table 1). Indeed, the amino acid composition depends onthe process used for protein extraction from the canolameal residue. Usually, up to 30% of the total protein ini-tially present in rapeseed meal is extracted in an alkalinemedium, and large-scale purification of canola proteins

Table 1. Amino acid composition expressed as mass percent of theglobulins isolate and the albumins isolate: from (Chabanon et al.,2007)

Amino acid Albumin isolate Globulin isolate

Asx 5.1 9.5Glx 30.4 20.2Ser 4.1 4.4His 4.7 5.1Gly 1.9 1.7Thr 4.4 4.7Ala 3.4 3.5Arg 8.6 9.8Tyr 3.7 4.5Cys 0.1 0.0Val 4.3 3.3Met 0.5 (0.6)a 1.2 (1.2)a

Phe 3.7 (7.4)b 5.7 (10.2)b

Ile 4.3 5.3Leu 8.5 9.1Lys 6.2 4.7Pro 6.4 6.8Trp n.d. n.d.

*Asx: aspartic acid þ asparagine; Glx: glutamic acid þ glutamine.n.d.: Not determined.a Met þ Cys.b Phe þ Tyr.

significantly affected the final protein composition(Chabanon, Chevalot, Framboisier, Chenu, & Marc, 2007).

The amino acid composition of canola meals was ana-lyzed by Shahidi, Naczk, Hall, and Synowiecki (1992).The authors reported that the canola meals used hada high content of glutamic acid (16.77e18.63% w/w pro-tein). However, they found that tyrosine, methionine andcysteine were present in lower concentrations. In thestudyof Shahidi et al. (1992), a two-phase solvent extraction pro-cess was used, and it was shown that this process did notsignificantly alter the amino acid composition of canola/rapeseed meals. However, a decrease in the proline contentwas observed. Of the essential amino acids, cysteine, me-thionine, isoleucine and leucine were also present at lowconcentrations. The two-phase solvent extraction processslightly increased the cysteine content in meals obtainedfrom some canola varieties. The authors stated that a slightreduction in the concentration of lysine might be due to theformation of lysinoalanine in the alkaline solutions used forprotein extraction. The calculated protein efficiency ratios(PER) of rapeseed meals based on the leucine and prolinecontents or on the leucine and tyrosine contents were2.19e2.64 (Shahidi et al., 1992).

Klockeman, Toledo, and Sims (1997) studied the aminoacid profile of untreated canola meal and found that it wassimilar to the published values for high erucic acid rapeseedprotein extract (Shahidi, 1990) but had lower values for cys-teine and valine. The canola protein isolate (CMPI)reported in the work of Shahidi (1990) contained signifi-cantly more leucine, phenylalanine, arginine, and asparagineand less isoleucine than a high erucic acid canola referenceprotein.When compared to defatted canola meal, CMPI con-tains more isoleucine and arginine and less lysine. The ob-served differences between the CMPI reported byKlockeman et al. (1997) and published values for canola(rapeseed) proteins may indicate that the genetic manipula-tions involved in the development of canola varieties of rape-seed have resulted in changes in seed storage proteins, whichare low in both erucic acid and glucosinolate contents. Fur-thermore, lysine was the only essential amino acid inCMPI and was present in significantly lower amounts com-pared with the crude commercial hexane defatted canolameal. Although there was a decrease in the measured lysine,no significant change in the serine or cysteine contents wasobserved (Klockeman et al., 1997). It is important to notethat in the work of Klockeman et al. (1997), no lysinoalaninewas detected in the studied canola meal protein isolate(CMPI), which follows previous reports of lysinoalaninelevels of <100 ppm in commercial hexane-extracted seeds(Deng, Barefoot, Diosady, Rubin, & Tzeng, 1990). Thelevels of isoleucine, lysine, and aspartic acid present in theCMPI were lower than those in soybean protein isolates(Nehez, 1985). Protein quality was evaluated using the calcu-lated protein digestibility corrected amino acid score(PDCAAS) values. It is well recognized that (PDCAAS)scores<1.00 indicate an amino acid deficiency, while scores

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23M. Aider, C. Barbana / Trends in Food Science & Technology 22 (2011) 21e39

�1.00 are considered to be equivalent when proteins arecompared. All (PDCAAS) scores for the present CMPI basedon the reference values for average infants were<1.00, withthe lowest scores for methionine and cysteine. The essentialamino acid with the lowest (PDCAAS) score based on the re-quirements for 2�5-year-olds was lysine. For comparison,the lowest score found for soybean protein for this age groupwas methionine plus cysteine (Henley & Kuster, 1994). All(PDCAAS) scores calculated for 10�12-year-olds andadults were >1.00. The (PDCAAS) analysis indicates thatCMPI has a lower protein quality than soy protein for averageinfants and 2�5-year-olds. If CMPI is used in products forinfants, blending the CMPI with other proteins will benecessary to balance the amino acid profile. The limitingamino acids in soy protein and CMPI are complementaryfor 2�5-year-olds; the two could be blended for nutritionalsupplements for this age group. Because all (PDCAAS)scores for the canola protein isolate were �1.00 for both10�12-year-olds and adults, this protein extract representsan excellent source of dietary proteins for products formu-lated for both of these age groups. CMPI and soy proteinhave equivalent nutritional qualities for these two agegroups. Compared to egg albumin, the canola albumin frac-tion containsmore histidine, cysteine,methionine, lysine andarginine; however, it contains less phenylalanine, tyrosineand isoleucine (Mieth, Schwenke, Raab, & Bruckner, 1983).

Canola protein fractionsThe canola proteins of interest are mainly storage pro-

teins located in the embryo because they are abundant.They represent approximately 80% of the total protein(Hoglund, Rodin, Larsson, & Rask, 1992; Mieth et al.,1983). Canola proteins can be classified to four groups: al-bumins, which constitute the water soluble fraction; globu-lins, which are soluble in salt solutions; prolamins, which isthe ethanol soluble fraction; and glutelins, which is thefraction that is insoluble in all of the solvents mentionedabove. Canola proteins can be also divided into variousfractions according to the corresponding sedimentation co-efficient in Svedberg units (S). This coefficient indicates thespeed of sedimentation of a macromolecule in a centrifugalfield. For canola proteins, the following fractions have beenreported: 12 S, 7 S and a split 2 S, 1.7 S or 1.8 S. Cruciferinand napin are the two major families of storage proteinsfound in canola/rapeseed. Napin is a 2 S albumin, and cru-ciferin is a 12 S globulin. They constitute 20% and 60% ofthe total protein content of mature seeds, respectively(Hoglund et al., 1992). Napins are low molecular weightproteins (12.5e14.5 kDa) characterized by strong alkalinitythat is mainly due to a high level of amidation of aminoacids. Napin possesses good foaming properties (Schmidtet al., 2004). Cruciferin is a neutral protein with a high mo-lecular weight (300e310 kDa) and several subunits. In itsnative form, cruciferin acts as a gelling agent. Oleosin,the other major type of protein found in canola, is a struc-tural protein associated with oil bodies (Ghodsvali et al.,

2005). Oleosins are low-molecular-weight (15e26 kDa)alkaline proteins and represent about 2e8% of the totalcanola seed proteins (Huang, 1992). Canola meal also con-tains minor proteins, such as thionins, trypsin inhibitors andlipid transfer proteins (LTP) (Berot, Compoint, Larr�e,Malabat, & Gu�eguen, 2005). These different protein frac-tions can be easily separated by chromatography, mem-brane filtration, such as ultrafiltration, and electrophoretictechniques. In canola seeds, the albumin and globulin frac-tions represent the majority of proteins. The molecularweight of the albumin fraction is lower than the globulins.The relative proportions of these fractions in canolaproteins are variable and depend on many factors, such asthe climate environment during maturation and the pres-ence of sulfur compounds. The amount of albumin dependson the contribution of sulfur compounds, which is depen-dent on the cysteine and methionine metabolism of theplant. At the same time, the amount of globulins inthe overall protein composition of canola depends on theamount of non-nitrogenous compounds. The amount ofeach protein fraction in the canola meal depends on theextraction and purification process (Yew-Min, Levente, &Leon, 1988). Generally, the estimated quantities of globulinand albumin are 60% and 40%, respectively (Mieth et al.,1983).

Chung, Lei, and Li-Chan (2005) conducted a study inwhich proteins were extracted from dehulled and defattedflaxseed/canola (NorMan cultivar) and fractionated byanion exchange chromatography to yield a fraction witha molecular weight of 365 kDa, as determined by SephacrylS-300 gel permeation chromatography. According to theirresults, the authors stated that reducing and non-reducingSDS-PAGE revealed three predominant bands of 20, 23and 31 kDa, respectively, and two predominant bands at40 and 48 kDa, respectively. In this study, the isoelectricfocusing technique was used to separate three componentswith isoelectric points (pI ) of 4.7, 5.1, and 5.6, and acidic(pI 4.5, 5.9, 6.1) and basic (pI 9.6) components wereobserved under reducing and denaturing conditions. Themajor fraction of canola had high disulfide but low sulfhy-dryl content, high contents of glutamate (or glutamine) andaspartate (or asparagine), and a low lysine/arginine ratio.According to these properties, the cultivar used in this studyshowed a lower content of the above-mentioned compoundsthan typical canola globulins. Fourier transform Ramanspectroscopy (FT-Raman spectroscopy) also indicateda high b-sheet content and a strong band near 1065 cm�1

that is typical of inter-molecular sheet interactions, whichsupports the oligomeric nature of the protein.

Canola is well recognized as an economically importantfarm-gate crop in many countries, such as Canada and theUSA; to further explore the potential of canola proteins asa value-added food ingredient, a better understanding of thefundamental properties of the two major canola proteins isnecessary (Wu & Muir, 2008). A study was reported inwhich two major protein components, cruciferin and napin,

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24 M. Aider, C. Barbana / Trends in Food Science & Technology 22 (2011) 21e39

were isolated from defatted canola meal by SephacrylS-300 gel filtration chromatography. SDS-PAGE showedthat cruciferin consists of more than 10 polypeptides, andnoncovalent links are more important than disulfide bondsfor stabilization of the structural conformation. Napin con-sists of two polypeptides and is stabilized primarily bydisulfide bonds. Purified cruciferin showed one majorendothermic peak at 91 �C compared with 110 �C for napin(Wu & Muir, 2008).

It has been reported that low molecular weight proteinsmake up 40e50% of the nitrogenous compounds in rape-seed (canola) (Mieth et al., 1983). According to various au-thors, the molecular masses of these compounds range from12 to 18 kDa (Amarowicz, Panasiuk, & Pari, 2003b). Forthe separation of low molecular weight canola proteins,HPLC methods with ion-exchange columns and capillaryelectrophoresis with SDS as a surfactant have been used(Amarowicz, Kolodziejczyk, & Pegg, 2003a).

Canola protein productionIn the United States patent application number

20100063255 (Logie & Milanova, 2008), it was reportedthat in addition to the 12 S and 2 S proteins, the proceduresused for the isolation of canola proteins produce significantquantities of a 7 S fraction, which appears to contain a newprotein. Accordingly, one aspect of the application was theisolation and purification of the 7 S protein of canola. It wasalso found that the relative proportions of the 12 S, 7 S and2 S proteins differ between a protein micellar mass-derivedcanola protein isolate and a supernatant-derived canola pro-tein isolate, which were prepared using industrial proce-dures. These procedures involved a multiple step processof extracting canola oil seed meal using a salt solution, sep-arating the resulting aqueous protein solution from the re-sidual oil seed meal, increasing the protein concentrationof the aqueous solution to at least 20% (w/v) while main-taining a constant ionic strength using a selective mem-brane technique, diluting the resulting concentratedprotein solution into chilled water to induce the formationof protein micelles, settling the protein micelles to forman amorphous, sticky, gelatinous gluten-like protein micel-lar mass (PMM), and recovering the protein-rich proteinmicellar mass from the supernatant. In the US-patent appli-cation number 20100063255 (Logie & Milanova, 2008),the PMM canola protein isolate was characterized by a pro-tein content of 90% (w/w, dry basis) and consisted of about60e98% of the 7 S protein, about 1e15% (w/w) of the 12 Sprotein and 0e25% (w/w) of the 2 S protein. In contrast,the supernatant-derived canola protein isolate was charac-terized by a protein content of 90% (w/w) and consistedof 0e5% (w/w) of the 12 S protein, about 5e40% (w/w)of the 7 S protein and about 60e95% (w/w) of the 2 S pro-tein fraction. Thus, the protein component profiles of thetwo canola protein isolates were very different. In thePMM-derived canola protein isolate, the predominant pro-tein species was the 7 S protein; however, in the

supernatant-derived canola protein isolate, the predominantspecies was the 2 S protein. These differences lead to dif-ferent behaviors in environments where the canola proteinisolates are used because their respective functional proper-ties are different. The different protein content profiles ofcanola protein isolates allow the production of any desired2 S/7 S/12 S protein profile for a specific application usingmixtures of two different canola protein isolates, such asthe PMM-derived isolate and the supernatant-derivedisolate.

Yew-Min, Levente, and Leon (1990) described a processfor the production of canola protein materials by alkalineextraction followed by precipitation and membrane pro-cessing. The process consisted of the extraction of oil-free meal at pH 10.5e12.5, isoelectric precipitation torecover proteins and ultrafiltration followed by diafiltrationto concentrate and purify the remaining acid-solubleproteins. According to the authors, these steps are comple-mentary and yield three products with excellent proteinrecovery. In this process, the isoelectric and soluble proteinisolates contained 87e100% protein (N � 6.25). All pro-tein fractions were free from glucosinolates, and the twotypes of isolates produced were low in phytate, light incolor, and bland in taste. It was reported that the isolateyield depended on the properties of the starting meal. Theprecipitation, ultrafiltration and diafiltration processeswere conducted on hexane-extracted meal (with hulledand dehulled materials), CH3OH/NH3/H2O-hexane-ex-tracted meal and dehulled meal. According to the reportedinformation, the meal was extracted with an aqueous NaOHsolution at solvent/meal ratio R ¼ 18. The hexane-extractedcanola meal and the commercial meal were extracted for30 min, while the CH3OH/NH3/H2O-hexane-extractedmeal was extracted for 2 h. The solutions were maintainedeither at a pH of 11.0 for hexane-extracted canola mealand commercial canola meal or at a pH of 12.0 for theCH3OH/NH3/H2O-hexane-extracted canola meal. In addi-tion, 1% (dry basis) Na2S03 was added to the commercialcanola meal during the aqueous extraction step to preventthe oxidation of phenolic compounds and to produce pro-tein products with a lighter color and better flavor. Aftercentrifugation and filtration of the liquid phase, the ex-tracted meal was washed twice with pH 11.0 or 12.0 waterat water/meal ratio R ¼ 6, and the washings were added tothe original extract. The extracted wet meal was recoveredand freeze-dried to produce a residual meal. The pH of thecanola protein extracts was adjusted to 3.5 by the additionof 6 N HCl. After separation, the protein precipitate waswashed with pH 3.5 or 4.0 water at a water-to-precipitate(wet) ratio of 10. The washed precipitate was then freeze-dried to produce an isoelectric protein isolate. The proteinsolution was first ultrafiltered at a concentration factor(CF) of 10 and then diafiltrated at a diavolume (DV) of5. A 10-kD ultrafiltration membrane was used in both mem-brane processing steps. Finally, the diafiltered retentate wasfreeze-dried to produce the soluble protein isolate.

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Klockeman et al. (1997) reported the isolation and char-acterization of defatted canola meal proteins. According totheir study, canola protein was extracted from defattedcanola meal using 5% (w/v) extraction solution of 0.4%(w/v) NaOH at room temperature on an orbital shaker at180�200 rpm for 60 min. The residual solids were dis-carded following centrifugation at 3000 g for 20 min at5e10 �C. Glacial acetic acid was then added to the proteinextract to adjust the pH to 3.5 for protein precipitation. Af-terward, the precipitated canola protein was separated bycentrifugation at 3000 g for 20 min at 5�10 �C. The proteinprecipitate was washed three times with distilled deionizedwater and centrifuged at 3000 g for 20 min at 5e10 �C be-tween each wash. The final protein isolate obtained wasfreeze-dried. This extraction method is summarized inFig. 1. The reported method consisted of the extractionand isolation of protein from crude commercial hexane-de-fatted canola meal, and the authors stated that this methodhas a significantly increased protein extraction capacity anda higher protein recovery. In their study, a proximate anal-ysis revealed that the hexane-defatted canola meal con-tained 12.3% moisture and 32.1% protein, 8.2% ash,4.4% fat, and 55.4% carbohydrate on a dry weight basis.The majority of the protein was soluble when dispersedin 0.4% NaOH or 5% NaCl. This solubility profile indicatesthat the isolated canola proteins are primarily glutelins andglobulins. Protein extraction in all concentrations of NaOHwas significantly increased if baffled flasks were used;95.2e99.6% of the total protein in the meal was extractedin 0.4% (w/v) NaOH. The maximum protein extraction wasobtained with a 5% (w/v) meal ratio and incubation in 0.4%(w/v) NaOH for 60 min at 180e200 rpm. This representsan increase in protein extraction from defatted canola

Fig. 1. Schematic representation of canola meal protein isolate extrac-tion method (from Klockeman et al., 1997).

meal as reported in the literature (80e95% reported byIsmond & Welsh, 1992; Diosady, Tzeng, & Rubin, 1984;Tzeng, Diosady, & Rubin, 1988a). Protein recovery valuesof 87.5% were obtained as compared to literature values of33e65% (Rohani & Chen, 1993; Xu & Diosady, 1994a,1994b).

Recently, the preparation of canola protein materials us-ing membrane technology and the evaluation of the func-tional properties of meals were reported (Ghodsvali et al.,2005). According to the authors, suitable conditions forthe extraction and precipitation of proteins from Iranian ca-nola (Brassica napus, cv. Quantum, PF, and Hyola) mealswere determined using a membrane-based process, whichconsisted of extraction of hexane-defatted canola meals atpH 9.5e12.0 and precipitation at pH 3.5 and 7.5 to recovera precipitated protein isolate (PPI). An acid-soluble proteinisolate (SPI) was then prepared by ultrafiltration (UF) fol-lowed by diafiltration (DF) and drying. The highest proteinyields were obtained by alkaline extraction at pH 12.0 forall meals investigated. The maximum yield of precipitatedprotein was observed at pH values between 4.5 and 5.5 anddepended on the variety and dehulling treatment. Almost90% of the proteins were recovered in three fractions: thePPI, SPI (81e98% protein, N*6.25), and the meal residue(35% protein). The glucosinolate contents of all mealstested and the protein fractions were low, and some sampleswere below the detection limit for glucosinolates. Both iso-lates were low in phytic acid content. In the work ofGhodsvali et al. (2005), the alkaline extraction was con-ducted by dispersing the canola meal in distilled water atroom temperature for 30 min. The pH of the extraction so-lution was adjusted to a predetermined level and main-tained by the addition of aqueous 5% NaOH as required.The authors reported that an appropriate concentration of1e6 N NaOH solution was selected to avoid excessive di-lution during pH adjustment. A pH range between 9.5 and12.0 was examined in increments of 0.5 pH units. Theslurry was centrifuged at 5000 rpm for 15 min, and the su-pernatant was filtered. The meal residue was washed twicewith an aqueous alkali solution (R ¼ 6) with the same pH asthe extraction solution and oven-dried overnight. Accordingto the authors, pH 12.0 was used in subsequent precipita-tion tests. For the isoelectric precipitation of canola pro-teins from the alkaline extract, the isoelectric points weredetermined. Meals were extracted with 5% NaOH at pH4.5 and a solvent-to-meal ratio of 18. The alkali solutionwas acidified with HCl (6 M) to obtain pH values between3.5 and 7.5 in increments of 0.5 pH units. After centrifuga-tion at 5000 rpm for 20 min, the supernatant was filteredusing filter paper, and the precipitate was washed with wa-ter acidified to the precipitation pH at a water-to-precipitate(wet) ratio of 10, centrifuged again and oven-dried over-night. Membrane separation was conducted in an ultrafiltra-tion unit in the diafiltration mode. A built-in peristalticpump drew the solution from a sample container andpumped it through the hollow fiber cartridge. The

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membrane used had a nominal molecular weight cutoff of10 kDa and a membrane area of 0.1 m2. The obtained per-meate consisted of water and dissolved low-molecularweight components. The retentate was returned to the sam-ple container. A soluble canola protein isolate was preparedwith the same process described by Tzeng et al., (1988b),which consisted of four major operational stages: alkalineextraction and washing, isoelectric precipitation and wash-ing, ultrafiltration and diafiltration. Hexane-extracted mealswere tested, and each meal was extracted at pH 12.0. Theextract was combined with all washes, and CaCl2 (15%,by weight of the starting meal) was added to the protein ex-tract. The pH was then reduced to the isoelectric point bythe addition of 6 N HCl. The pH was maintained for15 min to allow protein aggregation, and then the suspen-sion was centrifuged. The supernatant was filtered, and af-ter separation, the protein precipitate was washed with 10times its weight of distilled water and centrifuged. The su-pernatant and all washes were combined and ultrafiltered ata CF of 10, followed by diafiltration at a DV of 5.

A more attractive approach for the valorization of canola(rapeseed) proteins consists of the production of differentpeptide fractions by enzymatic hydrolysis followed bymembrane filtration (fractionation). In this context, a recentstudy reported the selective separation of peptidescontained in a rapeseed (Brassica campestris L.) proteinhydrolysate using ultrafiltration/nanofiltration (UF/NF)membranes (Tessier, Harscoat-Schiavo, & Marc, 2006). Inthis study, the ability of a charged ultrafiltration (UF) mem-brane to fractionate the small peptides found in a rapeseedprotein enzymatic hydrolysate based on charge characteris-tics was investigated. Because the peptide mixture obtainedafter enzymatic hydrolysis was heterogeneous and difficultto separate, the authors proposed an original approach thatrequired the development of technological alternatives formore efficient separation of the numerous peptide species.In this study, a preliminary step consisted of precipitationfollowed by filtration with a 3-kDa molecular weight cutoff(MWCO) membrane to obtain a concentrated solution ofsmall peptides. The feasibility of fractionating these smallpeptides with a charged 1-kDa MWCO membrane wasalso investigated. According to this study, this approach al-lowed an estimation of the contribution of electrostatic in-teractions during membrane fractionation. Moreover, theeffect of solution pH and ionic strength on peptide trans-mission was studied. The ionic strength contribution wasconsidered by studying its effect on the selectivity of a de-salting step by nanofiltration on a 0.5-kDa MWCO nanofil-tration membrane. It has been reported that peptidetransmission was lower at pH 9 than at pH 4 and the lowestat pH 9 and with low ionic strength. The ionic strength hada significant effect at pH 9 but showed no effect at pH 4.This difference could be attributed to the different ionicspecies that acted as counter-ions during membrane filtra-tion. The amino acid analysis and capillary electrophoresisrevealed that negatively charged (acidic) peptides were

found in lower proportions in the permeate. The oppositetrend was observed for basic peptides, whereas neutralpeptides were found in the same proportion in the retentateand permeate. The authors explained this behavior basedon the Donnan theory and the existence of electrostatic in-teractions (attractive and repulsive forces) at the membra-neesolution interface. Selectivity between basic and acidpeptides was as high as 1.90 at pH 9 and low ionic strength.A membrane-based process was proposed for the fraction-ation of rapeseed peptide mixtures (Tessier et al., 2006).

Canola protein functional propertiesWater absorption capacity (WAC)

Khattab and Arntfield (2009) studied the water absorp-tion capacity of canola proteins and reported that the en-hanced ability of canola meal to absorb and retain waterimproved the water binding capacity of the food product,enhanced its flavor retention, improved its mouthfeel andreduced the moisture of food products. In their study, thewater absorption capacities of raw and treated meals werereported, and it was shown that the treatment of the mealhad a significant effect on the WAC. Canola meal wasable to absorb 390% of its initial weight, and its WACwas higher than soybean meal, which absorbed 303% ofits initial weight, but lower than flaxseed meal. This resultagreed well with Wanasundara and Shahidi (1994), whofound that the WAC of flaxseed meal was considerablyhigher than that of canola. These results agree with thosereported for canola meal by Naczk, Diosady, and Rubin(1985) and Ghodsvali et al. (2005), who showed that thewater absorption capacities of canola meals vary with ca-nola cultivar (variety) and dehulling treatment. For canolameals, values between 218% and 382% have been reported.However, it is important to take in consideration that the ca-nola meals used in the literature contained considerableamounts of fiber, which can enhance the overall water hold-ing capacity, and studies on the water holding capacity ofcanola protein isolates would be more relevant. This agreeswith the information reported by Wanasundara and Shahidi(1994), who stated that the higher water adsorption of sol-vent-extracted oil seed meals may be due to the presence ofhull polysaccharides. Sosulski, Humbert, Bui, and Jones(1976) studied the water absorption properties of rapeseedflours and isolates and reported that the WHC of these in-gredients exceeded 200% and compared favorably withthat of soybean flour. Manamperi, Pryor and Chang(2007) separated and evaluated canola meal and proteinfor industrial bioproducts and found that the water absorp-tion capacity of canola meal exceeded 250%; their resultagrees with values reported for different varieties of canolameal, which ranged from 209% (Ghodsvali et al.., 2005) to382% (Naczk et al., 1985). Mahajan, Dua, and Bhardwaj(2002) reported a study in which dry and swollen canolaseeds were defatted with hexane, and the freeze-dried pow-der was analyzed for the functional properties of the meals.

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The results showed that the water absorption capacity of theswollen rapeseed meal was higher than dry meal.

Oil/fat absorptionThe fat-adsorption capacity of any food compound is

important for food applications because it relies mainlyon its capacity to physically entrap oil by a complex capil-lary-attraction process. In many food applications, such asemulsion-type meat products, the ability of a food compo-nent to entrap oil is an important characteristic because fatacts as a flavor retainer, a consistency trait and an enhancerof mouthfeel (Khattab & Arntfield, 2009). The fat absorp-tion capacity of canola meal was studied and comparedwith those of soy and flaxseed meals (Khattab &Arntfield, 2009). It was reported that significant differencesin the oil absorption capacities were noted among theabove-listed meals and that soy meal had the highest value,which was followed by canola and flaxseed meal, respec-tively. In general, the fat absorption capacity depends onseveral properties, such as powder particle size and surfacetension. In addition, the fat absorption capacity is nega-tively correlated with water absorption capacity. This state-ment agrees with the information reported by Naczk et al.(1985) and Ghodsvali et al. (2005), who reported canolameal oil absorption and water holding capacity values of188e203 and 265.5e281.5%, respectively. The oil absorp-tion capacity can be modulated by different treatments, andit was reported that heat treatments increased the oil ab-sorption capacities of different oil seed meals, including ca-nola. Among heat treatments, boiling was reported toproduce the greatest enhancement. The phenomenon of in-creasing fat absorption after heat treatment has been asso-ciated with the heat dissociation of proteins anddenaturation, which is hypothesized to unmask non-polarresidues in the interior of the protein molecules (Kinsella& Melachouris, 1976, pp. 219e280). In a report byMahajan et al. (2002), dry and 24-h swollen rapeseedswere defatted with hexane, and the freeze-dried powderwas analyzed. It has been reported that the fat absorptioncapacity of swollen rapeseed meal is higher than that ofthe dry meal. Gruener and Ismond (1997) reported the iso-lation of a canola protein concentrate with improved func-tional properties; in their method, the canola 12 S globulinwas isolated by the protein micellar mass procedure (PMM)and modified by acetylation and succinylation. It wasshown that the emulsion stability significantly increasedinitially and then decreased at the highest levels of modifi-cation. Following acylation, the fat absorption capacity wassignificantly elevated.

Protein/nitrogen solubilityFor food applications, protein (nitrogen) solubility is an

important parameter that influences the extent of applica-tions in different food matrices. In some cases, such asbeverages, high protein solubility is a determinant forapplication as a fortification ingredient. In other

applications where a high water holding capacity is re-quired, the situation is quite different because solubility isgenerally negatively correlated with water holding capacity.As reported by Prinyawiwatkul, Beuchat, McWatters, &Phillips (1997), protein solubility can be considered asthe most important property because it affects other proper-ties, such as emulsification ability, foam-forming capacityand gel formation. Recently, Khattab and Arntfield (2009)studied the functional properties of raw and processed ca-nola meals and showed that canola meal had a protein sol-ubility (expressed as nitrogen solubility) of 66.42%. At thesame time, they compared canola meal protein solubilitywith soy and flaxseed meals, which have protein solubilitiesof 74.00% and 56.50%, respectively. The results obtainedin this study were comparable with those reported in the lit-erature (John & Baize, 1999; Madhusudhan & Singh, 1985;Wanasundara & Shahidi, 1994). As reported in Khattab andArntfield (2009), canola meal protein solubility was signif-icantly reduced after heat treatment, which consisted of dryroasting and boiling in water. The two treatments caused29.07% and 25.61% solubility reductions, respectively.The protein solubilities of soy and flaxseed meals were re-duced by 33.69% and 46.27%, respectively, after dry roast-ing treatment and 43.00% and 39.40%, respectively, afterboiling. Protein denaturation during heat treatment couldexplain the solubility reduction. Heat treatment could en-hance the exposure of hydrophobic residues, which contrib-ute to the reduction in the overall protein solubility.Electrostatic repulsion and ionic hydration that occur at dif-ferent pHs can also affect protein solubility (Moure,Sineiro, Dom�ınguez, & Paraj�o, 2006). Klockeman et al.(1997) reported the extraction and isolation of proteinsfrom canola oil processing waste. They showed that canolaproteins had poor solubility between pH 2 and 10 for alldispersion solutions used. The solubility of the protein iso-lates was 60% or less. The low solubility could be attrib-uted to the extraction conditions used. Radwan and Lu(1976) studied the solubility of the proteins of the dehulledand defatted ‘Tower’ variety of rapeseed (canola) in aque-ous solutions at 25, 35, 45, and 55 �C and at pH 1e13. Ac-cording to this study, the minimum solubilities occurred atpH values of 4.5, 4.8, 7.0, and 7.2, respectively, for the fourtemperatures tested. These differences could be attributedto the different pHs that were used to precipitate the differ-ent protein fractions. Paulson and Tung (1989) studied theeffects of succinylation (54% and 84% modification of freeamino groups) in the pH interval of 3.5e11.0 and NaClconcentrations up to 0.7 M on the solubility of a canola pro-tein isolate. According to this study, succinylation mark-edly enhanced the protein solubility at alkaline andslightly acidic pH values, while the effect of NaCl concen-tration depended on the pH value. This might be related tothe effect of succinylation on surface hydrophobicity(Paulson & Marvin, 1987), which decreases as the levelof succinylation increases. This can be confirmed by Zetapotential values, which became more electronegative as

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both succinylation and pH increased but decreased with theaddition of NaCl. Depending on the pH, addition of salt toa protein suspension can affect the net charge density of theproteins and thus modify the solubility by enhancing or re-ducing inter-molecular repulsions. In Gruener and Ismond(1997), the canola 12 S globulin was isolated using the pro-tein micellar mass procedure (PMM) and modified by acet-ylation and succinylation to obtain a canola proteinconcentrate with improved functional properties. It hasbeen shown that protein solubility below the isoelectricpoint of the PMM was impaired, but the solubility at neu-tral to alkaline pH values was greatly enhanced. Based onthe information on canola protein solubility, it is possibleto highlight one parameter that contributes to the solubilityof purified isolates: the predominance of low molecularweight species (Fig. 2).

Emulsifying propertiesIn food applications, such as emulsion-type meat prod-

ucts, salad dressings and mayonnaise, emulsifying proper-ties of canola proteins is an important attribute andlargely defines the extent of use of this ingredient to stabi-lize food systems. Several studies have been conducted inthe past two decades on the feasibility of using canola pro-teins in emulsion-type foods. Recently, Khattab andArntfield (2009) studied the emulsification ability of canolameal using two parameters: emulsifying capacity (EC) andstability (ES). They showed that both properties are func-tions of the protein concentration, pH, and ionic strength.They also related these properties to the viscosity of thesystem, but this parameter (viscosity) was function of thementioned above conditions. Indeed, emulsion is a complexsystem that involves a multitude of chemical and physicalphenomena, which play different roles in the formation,

Fig. 2. SDS-PAGE of canola protein (from Ebrahimi, Nikkhah, Sadeghi.Raisali, 2009). Lane 1 is the standards and Lane 2 is the canola/

rapessed proteins.

stability, and textural properties of a protein-fat-water sys-tem. It is also important to ensure that the technique used toevaluate emulsifying properties is adequate. In the work ofKhattab and Arntfield (2009), the emulsifying capacity ofcanola proteins (meal) was expressed as the maximumamount of oil that the meal solution would emulsify with-out losing its emulsion characteristics. According to thereported results, the investigated canola meal showedsignificantly higher EC values compared with those ofsoy and flaxseed meals. However, they also reported thatroasting and boiling caused significant reductions in theECs of these meals. They explained that that high proteinsolubility (Kinsella & Melachouris, 1976, pp. 219e280)and high fat-adsorption capacity were positively correlatedwith the ability to form and stabilize emulsions. They alsostated that the lower EC values of boiled canola meal mightbe due to its low nitrogen solubility. Similarly, the degree ofheating was also reported to be a determinant for the reduc-tion of the emulsifying capacity of legume proteins in gen-eral (Eke & Akobundu, 1993). Dev and Mukherjee (1986)have reported that rapeseed products generally have loweremulsifying capacities but higher emulsifying stabilitiesthan soy products, although the processing treatment canalter this trend. Isolates tend to have improved emulsifyingproperties as compared to concentrates (McCurdy, 1990).

Recently, a fundamental study examined the emulsifyingproperties of the two major canola proteins cruciferin andnapin. It has been reported that the emulsion preparedwith cruciferin showed a significantly higher specific sur-face area and a lower particle size than that of napin. Thestudy reported by Wu and Muir (2008) indicated that thepresence of napin could detrimentally affect the emulsionstability of canola protein isolates (Wu & Muir, 2008).

The emulsifying ability of canola proteins was studiedin combination with hydrocolloids. A study investigatedthe properties of commercial canola protein isolateehydrocolloid-stabilized emulsions under varied conditions,such as different canola protein isolate concentrations,amounts of salt and hydrocolloid added, pH values of the me-dium and the presence of denaturants (Uruakpa & Arntfield,2005). In this study, the emulsifying activity index (EAI)and emulsion stability (ES) were determined by a turbidimet-ric method. According to the authors, the obtained resultsshowed that under conditions that promote complex formationbetween the proteins and hydrocolloids, which included pH 6and the addition of 1% (w/v) k-carrageenan, the EAI of CPI-stabilized emulsions increased from 162 to 201 m2/g and theES increased from 68% to 95%. Under conditions that pro-mote incompatibility between canola proteins and the hydro-colloid (pH 10), the use of 1% (w/v) guar gum increased theEAI of CPI-stabilized emulsions from 68 to 177 m2/g andthe ES from 66% to 100%. The lower EAI and ES values ob-served in the hydrocolloid-stabilized CPI emulsions treatedwith sodium salts and denaturants support the involvementof hydrophobic interactions, hydrogen bonds and disulfidelinkages in the emulsification of these systems. It was also

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shown that the interfacial properties of CPIehydrocolloidcomplexes were improved by electrostatic complexformation and thermodynamic incompatibility, makingthese systems suitable for stabilizing food emulsions, suchas salad dressings and mayonnaise (Uruakpa & Arntfield,2005).

Foaming propertiesIn many food applications, because the surface area in

the liquid/air interface increases, proteins denature and ag-gregate during whipping. Air entrapment plays a major rolein different food matrices and is important for flours used inmany leavening food products, such as breads, cakes andcookies (Sreerama, Sasikala, & Pratape, 2008). The foam-ing capacity of canola meal was studied and comparedwith soy and flaxseed (Khattab & Arntfield, 2009). Theyshowed that the foam capacities and stabilities of raw andtreated canola meal were higher than those of soy and flax-seed meals. They expressed the foaming capacity as a per-centage and reported values of 56.44%, 44.56% and17.82%, for canola, soy and flaxseed meal, respectively.It was shown that heat treatment significantly reducedboth the foaming capacity and foam stability of the differ-ent meals, including canola meal. The authors explainedthat this reduction was mainly related to protein denatur-ation; this conclusion agrees with the data reported byLin, Humbert, & Sosulski, 1974, who stated that a nativeprotein gives a higher foam stability than a denaturedone. Gruener and Ismond (1997) conducted a study inwhich the canola 12 s globulin was isolated by the proteinPMM and modified by acetylation and succinylation to im-prove the functional properties of the canola protein con-centrate. The PMM foaming capacity was significantlyincreased by acylation, and the foam stability decreasedsignificantly after acylation. They concluded that in generalthe acylated concentrates possessed improved functionalityas compared to the PMM, which makes them more suitableas a food ingredient. Xu and Diosady (2002) studied thefunctional properties of Chinese rapeseed meals and re-ported that Chinese rapeseed meals foams were more stablethan those of the canola meals prepared by Naczk et al.(1985). Moreover, they showed that Chinese rapeseed pro-tein isolates were characterized by excellent whippability.They found that the foaming properties of the soybean iso-late were between those of the rapeseed meals and rapeseedprotein isolates. The difference between a meal and an iso-late is the protein content, which is obviously higher in anisolate. All foams were stable and lasted for more than 2 h.The foaming properties of canola protein were evaluated asa function of degree of protein hydrolysis. Limited canolaprotein hydrolysates ranging from 3.1% to 7.7% hydrolysiswere produced from an isoelectrically precipitated proteinisolate. It has been shown that all canola protein hydroly-sates have lower foam stabilities than those reported inthe literature for other rapeseed protein products(Frokjaer, 1994), and the foam stability decreased as the

degree of hydrolysis (DH) increased. The authors con-cluded that hydrolysates with an increased degree of hydro-lysis are apparently capable of foaming but lack thestrength to maintain the foam as a result of the reductionin protein molecular weight. The foam stability of the pro-tein isolates dropped to 0% after 15 min of hydrolysis(Vioque, S�anchez-Vioque, Clemente, Pedroche, & Mill�an,2000).

Gelling abilityIn general, all proteins can form a gel, but differences

exist in the gel strengths. The ability of proteins to formgels can be measured by the determination of the least ge-lation concentration, which is defined as the minimal pro-tein concentration needed to produce a gel that does notslide down the walls of an inverted tube (Moure et al.,2006). Khattab and Arntfield (2009) studied the least gela-tion concentrations of raw and heat-treated canola mealsand reported that neither roasting nor boiling caused a sig-nificant increase in the least gelation concentration of dif-ferent canola meals. This is supported by reports in thescientific literature, which show that the gelation of proteinsincreases with molecular weight (size) because large mole-cules form extensive networks by cross-linking in threedimensions (Oakenfull, Pearce, & Burley, 1997). Comparedwith soy and flaxseed meals, canola meal required the high-est concentration for gelation regardless of the treatmentused.

To improve the function of canola proteins in gel-likefood systems, different additives can be combined with theseproteins to make convenient gels. In this context, a study hasbeen reported in which the thermogelation properties of a ca-nola protein isolate in amixed systemwith k-carrageenan (k-CAR) were studied using dynamic rheological testing. Thegel properties were evaluated under different conditions,such as pH, NaCl, and k-carrageenan and canola protein iso-late concentrations. The factorial and response surface opti-mization models were used to identify the processingconditions that would result in CPIek-CAR gels with max-imized G0 values (�44,000 Pa) and minimized tan d values(0.01e0.11). According to the results, it was found thatcanola proteinecarrageenan gel formation was stronglypH-, salt (NaCl)- and k-carrageenan concentration-depen-dent (Uruakpa & Arntfield, 2004). The reported results indi-cated that the optimum conditions for CPIek-CAR gelswere pH 6, 0.05 M NaCl, 3% k-CAR and 15% CPI. Samplesprepared at pH 6 showed high G0 (95,465 Pa) and lowtan d (0.15) values. High G0 values indicate stronger inter-molecular networks and increased proteineprotein and pro-teinepolysaccharide interactions, while low tan d valuesindicate a more elastic network. A synergistic behavior be-tween CPI and k-CAR was observed with superior networkstrength (high G0 values) for the mixed gels at temperaturesabove 80 �C. Furthermore, the gels showed improved net-work structure (low tan d values) during the heating andcooling phases. The canola proteinek-carrageenan mixtures

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exhibited very strong and elastic networks, indicating thatCPI can serve as a structuring agent in mixed food systems(Uruakpa & Arntfield, 2004).

Canola proteins have been considered as potential ingre-dients for food applications where a gel-like structure is de-sired. In a recent study, enzymatic modification withtransglutaminase (TG) was used to enhance the gelationof a canola protein isolate and thus improve its potentialas a food ingredient. Different parameters, such as the ef-fects of canola protein isolate concentration, transglutami-nase (TG) concentration, and treatment temperature andtime, have been studied to determine their effects on canolaprotein isolate gelation properties. Different techniques,such as texture analysis, sodium dodecyl sulfate-polyacryl-amide gel electrophoresis (SDS-PAGE) and scanning elec-tron microscopy, were used to characterize the resultingcanola protein isolate networks. It has been reported thatthe protein concentration, amount of transglutaminase(TG), and treatment temperature significant affected gelstrength. According to the authors (Pinterits & Arntfield,2008), gelation was improved by increasing the amountsof protein and TG while keeping the treatment temperatureclose to 40 �C. SDS-PAGE showed that subunit cross-link-ing occurred during TG treatment, which thus explained theincrease in gel strength observed during texture analysis.The above-mentioned effects were also confirmed bymicroscopy (Pinterits & Arntfield, 2008).

Schwenke, Dahme, and Wolter (1998) reported the gel-forming abilities of a rapeseed (canola) protein isolate, whichwas composed of 70% globulin (cruciferin) and 30% albu-min (napin), and their individual protein components. Inthis study, the influence of acetylation upon the gelationproperties was also studied. The highest gel strength (mea-sured as shear modulus) of the isolate was obtained at pHvalues around 9, which is between the isoelectric points ofthe major proteins. Moreover, purified cruciferin gave thehighest shear modulus values, with maxima at pH 6 and 8.Weak and poorly stable gels that exhibited strong hysteresiswere obtained with isolated napin. The authors also reportedthat acetylation resulted in a pH shift of the shear modulusmaximum of the protein isolate to about 6. The gelation tem-perature of the acetylated isolate was more dependent on pHand concentration compared with the other proteins(Schwenke et al., 1998). Because of the increasing demandfor plant proteins in gel-like products, the ability to formgels, which is a key functional property of plant proteins,has been extensively studied in the past two decades. Gilland Tung (1978) first demonstrated the ability of a highlyglycosylated 12 S rapeseed (canola) protein to form gels dur-ing heating at pH> 4. The strongest gels were formed at highpH and ionic strength conditions. The high carbohydratecontents of the canola meal (12.9%) led the authors to pro-pose that proteinecarbohydrate interactions occurred duringgel formation. It was also reported that the viscosity of a hex-ametaphosphate-extracted rapeseed protein isolate heated to80 �C increased, but it did not form a gel (Schwenke et al.,

1998). Paulson and Tung (1989) studied the thermally in-duced gelation of a rapeseed (canola) protein isolate heatedto 72 �C. Gels were formed only at high pH (>9.5). L�egerand Arntfield (1993) studied the gelation of 12 S canola glob-ulin. Gels prepared with 6% protein under alkaline condi-tions were superior to gels prepared from acidic solutions.The effects of pH, salts, and denaturing and reducing agentson the gelation properties led the authors to conclude thathydrophobic forces and electrostatic interactions were re-sponsible for establishing the gel network, while gel stabili-zation and strengthening were attributed to disulfide bonds,electrostatic interactions, and hydrogen bonding. Succinyla-tion was used to improve the gel-forming properties of a can-ola protein isolate by Paulson and Tung (1989). In this study,the pH range of gel formationwas extended from the alkalineregion (pH> 9.5) to slightly acidic pHs (5.0). Although sev-eral studies have analyzed the gelling ability of canolaproteins, it is well recognized that comparison of the gel-forming properties of the different canola protein prepara-tions is difficult. This is principally because there are majordifferences the compositions and purities of the proteins.Therefore, studies in which pure fractions and knowncombinations must be conducted bettering increase theunderstanding of the canola protein behavior in relation togel formation. In this context, the study reported byGruener and Ismond (1997), which the canola 12 S globulinwas isolated by the protein PMMandmodified by acetylationand succinylation, showed that the gelation properties of ca-nola proteins were generally improved by acylation. Further-more, the acylated concentrates were significantly lighter incolor than the original PMM.

Bioactive compounds from canola proteinsThe increase in consumer awareness about healthy foods

has encouraged researchers to identify bioactive naturalcomponents in different products (Murty, Pittaway, &Ball, in press). Canola proteins are considered to be attrac-tive and promising sources of bioactive compounds.Recently, a number of research works have focused onthe investigation of different methods to produce activepeptides from the enzymatic hydrolysis of canola proteins.Angiotensin-I Converting Enzyme (ACE) inhibitory activ-ity, antioxidant activity, bile acid-binding capacity, anti-thrombotic activity and cell growth effects have beenidentified as bioactive characteristics of canola/rapeseedproteins (Table 2).

ACE inhibitory activityBlood pressure is controlled by a regulatory hormonal

mechanism known as the “renin angiotensin system.” Theregulatory mechanism takes place in the kidneys, wherethe hydrolytic enzyme renin is secreted. Hence, plasma an-giotensinogen is hydrolyzed to a decapeptide called Angio-tensin I, which is subsequently hydrolyzed by AngiotensinConverting Enzyme (ACE) to form Angiotensin II, which isa vasoconstricting octapeptide that elevates the blood

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Table 2. Bioactivity of rapeseed proteins and hydrolysates

Bioactivity Rapeseed proteins/hydrolysates References

ACE inhibitory activity Subtisilin hydrolysates of the protein isolate (purification ofrapakinin Arg-Ile-Tyr)

Yamada et al., 2010.

Hydrolysates of the defatted meal obtained by enzymatic treatmentwith: Umamizyme; Proteases A, P, R, M and S Amano; ProleatherFG-F; Alcalase 2.4L; Enzeco alkaline protease L-FG; Enzeconeutral protease NBP-L; Pepsin, Trypsin and Chymotrypsin-TLCK

Wu et al., 2009.

Alcalase 2.4L hydrolysate of the protein isolate Megias et al., 2006,Wu & Muir, 2008.Alcalase 2.4L hydrolysate of the defatted meal (purification of Val-Ser-Val and PheeLeu located in napin and cruciferin, respectively)

Wu et al., 2008

Alcalase 2.4L hydrolysates of the protein isolate, napin andcruciferin

Wu & Muir, 2008.

Protein isolate Yoshie-Stark et al., 2008.Pepsin and Pepsin/Pancreatin hydrolysates of the protein isolate

Antioxidant properties Alcalase/Flavourzyme hydrolysate of the albumin isolate Xue et al., 2009.Alcalase 2.4L hydrolysate of the flour (purification of Pro-Ala-Gly-Pro-Phe corresponding to the sequence 38e42 of napin).

Zhang et al., 2008; Zhang et al., 2009.

Protein isolate Yoshie-Stark et al., 2008.Pepsin and Pepsin/Pancreatin hydrolysates of the protein isolate

Bile acid-binding capacity Protein isolate Yoshie-Stark et al., 2008.Pepsin and pepsin/pancreatin hydrolysates of the protein isolate

Anti-thrombotic activity Alcalase 2.4L hydrolysate of the rapeseed slurry from a wet-milling Zhang et al., 2008Effect on cell growth Alcalase, Esperase, Neutrase, Orientase and Pronase hydrolysates

of the protein isolateChabanon et al., 2008;Farges-Haddani et al., 2006;Farges et al., 2008.

31M. Aider, C. Barbana / Trends in Food Science & Technology 22 (2011) 21e39

pressure (Chen et al., 2009). Furthermore, ACE also con-tributes to vasoconstriction by the degradation of bradyki-nin, a vasodilator. Consequently, the inhibition of ACEcould be an alternative method to lower blood pressure(Chen et al., 2009).

Defatted canola meals from seeds that were processedwith different methods were hydrolyzed by Alcalase to pro-duce hydrolysates that inhibited ACE activity (Megiaset al., 2006; Wu, Aluko, & Muir, 2009). Heat-treated mealsyielded protein hydrolysates with 50% ACE-inhibitory con-centrations of 27.1 and 28.6 mg protein/mL compared with35.7 and 44.3 mg protein/mL for the non-heat treated meals.In this study, separation of the hydrolysate on a SephadexG-15 gel permeation column (GPC) yielded a fractionwith an IC50 value of 2.3 mg protein/mL. From a fundamen-tal point of view of the mechanism of action, amino acidanalysis showed that the GPC fraction contained 45% aro-matic amino acids in comparison to 8.5% in the raw hydro-lysate. In particular, two peptides with the primarycompositions Val-Ser-Val and PheeLeu were purified andlocated in the primary structures of the napin and cruciferinnative proteins. It has thus been suggested that the canolaprotein hydrolysate should be considered as a potential in-gredient for the formulation of hypotensive functionalfoods (Wu et al., 2009). To simplify the method of ACE-in-hibitory peptide production, defatted canola meal was sub-jected to enzymatic proteolysis with different enzymes, andit was found that Alcalase 2.4 L and protease M “Amano”were the most effective enzymes for the production ofACE-inhibitory peptides from canola proteins. The IC50

values of the canola protein hydrolysates ranged from

18.1 to 82.5 mg protein/mL. The differences in the ACE-in-hibitory activities of the various protein hydrolysates re-flected the different enzyme specificities. In this study,ion-exchange chromatography was used to purify specificfractions of canola protein hydrolysate, and this approachyielded an increase in the protein content to more than95% without loss of ACE-inhibitory activity. Accordingto this study, this fraction was resistant to degradation bygastrointestinal enzymes and ACE during in vitro incuba-tion (Wu, Aluko, & Muir, 2008). Specific canola proteinfractions were also used to produce hydrolysates. Cruci-ferin and napin hydrolysis yielded peptide fractions thatshowed potent angiotensin I-converting enzyme inhibitoryactivity in vitro (IC50 0.035 and 0.029 mg/mL, respec-tively), but these activities were weaker than that of the ca-nola protein isolate hydrolysate (IC50 0.015 mg/mL) (Wu &Muir, 2008). This behavior can be attributed to the syner-getic effect of different fractions of raw canola proteinhydrolysate.

On the other hand, the in vivo anti-hypertensive proper-ties of rapeseed proteins have been also reported byYamada et al. (2010). Thus, an ACE-inhibitory peptidecalled rapakinin (Arg-Ile-Tyr), which had an IC50 of28 mM, was isolated from the subtisilin-digested rapeseedproteins. Rapakinin induced vasorelaxation with an EC50

of 5.1 mM in the mesenteric artery of spontaneously hyper-tensive rats (SHRs). Hence, the mechanism of vasorelaxa-tion was elucidated, and it has been suggested that theanti-hypertensive activity of rapakinin might be mediatedby the PGI(2)-IP receptor, followed by CCKeCCK(1)receptor-dependent vasorelaxation.

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Antioxidant propertiesThe production of free radicals leads to many health dis-

orders due to the damage they cause to biological macro-molecules, especially DNA. Therefore, many naturalantioxidants have been used to prevent peroxidation pro-cesses (Kim & Wijesekara, 2010). Xue et al. (2009) inves-tigated the possible conversion of insoluble rapeseed mealprotein into functionally active ingredients for food appli-cations. The rapeseed meal protein isolates were digestedwith Alcalase and Flavourzyme, and the resultant rapeseedcrude hydrolysate (RSCH) exhibited dose-dependent reduc-ing antioxidant activities and hydroxyl radical scavengingabilities. The RSCH also inhibited malonyldialdehyde(MDA) generation by 50% in blood serum at 150 mg/mL. The RSCH was further separated into three fractions(RSP1, RSP2, and RSP3) by Sephadex gel filtration accord-ing to molecular weight. The amino acid compositions andantioxidant potentials of the fractions were assessed, and ithas been reported that all three fractions showed inhibitionof superoxide anion generation to various extents. Theyalso inhibited the autohemolysis of rat red blood cells andMDA formation in a rat liver tissue homogenate (Xueet al., 2009). In another study, the antioxidative capacitywas observed for rapeseed peptides obtained by Alcalasehydrolysis (Zhang, Wang, & Xu, 2008). The median effec-tive dose (ED50) values of the three peptide fractions fora,a-diphenyl-b-picrylhydrazyl (DPPH) radical scavengingactivity were between 41 and 499 mg/mL; for the inhibitionof lipid peroxidation in a liposome model system, the ED50

values were between 4.06 and 4.69 mg/mL, which are com-parable to that of ascorbic acid at 5 mg/mL (Zhang et al.,2008; Zhang, Wang, Xu, & Gao, 2009). Moreover, themost antioxidative peptide was identified by LC-MS/MSas Pro-Ala-Gly-Pro-Phe, which corresponds to amino acidresidues 38e42 of napin (Zhang et al., 2009).

The results suggest that rapeseed protein hydrolysatescould be useful as a human food additive and a source ofbioactive peptides with antioxidant properties (Xue et al.,2009).

Bile acid-binding capacityHypercholesterolemia is characterized by the accumula-

tion of LDL (low-density lipoprotein) cholesterol in theblood vessels and is considered as a major cause of heartdiseases and atherosclerosis (World Health Organization,2009). However, hypercholesterolemia can be preventedby exercise, a healthy diet and the consumption of bileacid sequestrants, which are better known as hypolipidemicagents (Anderson & Siesel, 1990). Plasma cholesterolserves as a substrate for the biosynthesis of the bile acidsin the liver. Hence, the sequestration of the bile acids leadsto degradation of cholesterol, which therefore reduces thelevel of cholesterol in the blood (Anderson & Siesel, 1990).

The in vitro hypocholesterolemic properties of rapeseedproteins have been evaluated through the determination ofthe bile acid-binding capacity. Yoshie-Stark, Wada, and

W€asche (2008) have shown that rapeseed protein isolates,which were obtained either by iso-precipitation or ultrafiltra-tion, and their hydrolysates, which were obtained by pepsinand pepsin/pancreatin digestions, were able to bind to bilesalts. In that study, the concentration of the bile salts usedwas of 1.5 mM, which corresponds to the physiological con-centrations of bile acids in the human body (1.5e7mM). Theresults showed that 5.77%e12.6% of sodium cholate and so-dium deoxycholate were bound by the rapeseed precipitatedprotein isolate and hydrolysates, whereas ultrafiltered rape-seed protein isolate and hydrolysates bound 5.81% to22.8% of the bile salts (Yoshie-Stark et al., 2008). Neverthe-less, neither the sodium cholate- nor the sodium deoxycho-late-binding capacities were significantly affected byhydrolysis with pepsin and pepsin/pancreatin, suggestingthat some large molecular weight protein fractions and undi-gested polypeptides are also able to bind the ligands. A sim-ilar lack of a direct association between hydrolysis and bileacid-binding capacity has been observed in other plantproteins and hydrolysates (Yoshie-Stark & W€asche, 2004;Ma & Xiong, 2009).

Anti-thrombotic activityThrombosis is an anomaly in blood coagulation that is

generally caused by blood hyperviscosity, platelet hyper-re-activity, a high level of hemostatic proteins, such as fibrin-ogen, and defective fibrinolysis. Thus, antithromboticsreduce the risk of thrombosis mainly by the reduction ofplatelet aggregation and the enhancement of fibrinolysis(Erdmann, Cheung, & Schr€oder, 2008).

The anti-thrombotic activity of crude rapeseed peptidefractions prepared from an aqueous extraction of rapeseedproteins digested with Alcalase 2.4 L has been observed(Zhang et al., 2008). The anti-thrombotic peptide fractionswere analyzed in terms of their amino acid content, and theresults showed that they were rich in His, Pro, Trp, Tyr,Met, Cys, and Phe. Furthermore, the rapeseed bioactivepeptide fractions had significant inhibitory activities onthe thrombin-catalyzed coagulation of fibrinogen, whichis considered to be a key step in the formation of fibrin clotsand therefore thrombosis. Although the inhibitory effectwas not dose dependent, 90% inhibition was observedwith peptide concentrations between 30 and 50 mg/mL.However, the anti-thrombotic effects observed were weakerthan that of heparin, which possessed a dose-dependent ef-fect and an ED50 value of 0.07 mg/mL (Zhang et al., 2008).

Effects on cell growthRapeseed protein hydrolysates, which were obtained af-

ter digestion with Alcalase, Esperase, Neutrase, Orientaseand Pronase and characterized by degrees of hydrolysis be-tween 24.7% and 36.3% and contained low molecular sizepeptides (under 1 kDa), have been shown to increase themaximal cell density of Chinese Hamster Ovary (CHO)C5 cells (Chabanon et al., 2008). Cell growth in the pres-ence of hydrolysates reached 120e150% of the reference

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cells (grown in media without supplementation with therapeseed hydrolysates) in serum-free medium, which con-sisted of a simple basal medium supplemented with trans-ferrin, insulin, albumin and trace elements. In addition tothe nutritional effect of the rapeseed protein hydrolysates,which are rich in free amino acids, the presence of peptidesthat affect growth or survival, including anti-apoptotic ac-tivity, have been also suggested to explain the positivegrowth effects of the rapeseed protein hydrolysates(Chabanon et al., 2008; Farges, Chenu, Marc, & Goergen,2008).

A fraction of Alcalase-hydrolyzed rapeseed proteins thatwas purified by ultrafiltration (3 and 1 kDa) and nanofiltra-tion (500 Da), which produced a mixture of both large(500e5000 Da) and small peptides (<500 Da), signifi-cantly stimulated the growth rates of CHO and other animalcells, including NS0, CHO K1 and Vero cells, and a maxi-mal cell density of 1.7� was obtained by addition of 4 g/lof hydrolysate. Moreover, the purified fraction reduced thedeath rate of CHO cells, increased the secretion of g-inter-feron and accelerated cell adaptation to serum-free condi-tions (Farges-Haddani et al., 2006; Farges et al., 2008).

Color of canola protein solutionsLike many plant materials, canola contains a consider-

able quantity of phenolic compounds. Most phenolic com-pounds identified in canola are phenolic acids andcondensed tannins, which are flavonoid-based polymericphenolic compounds. The major phenolic component in ca-nola was reported to be sinapine, the choline ester of si-napic acid. The overall concentration of these compoundsis not negligible; it is estimated to be about 1% (w/w) ofthe meal. Condensed tannins may cause astringency dueto their ability to precipitate proteins in the mouth. Afteroxidation, phenolic compounds induce the developmentof dark colors in canola proteins. Phenolic compoundsare highly reactive molecules, and under alkaline condi-tions, they can undergo enzymatic as well as non-enzymaticoxidation to form quinones, which can react with proteinsand produce dark green or brown colors in canola proteinsolutions (Leung, Fenton, Mueller, & Clandinin, 1979;Xu & Diosady, 2000). In most processes used to producecanola proteins, the color of the isoelectrically precipitatedcanola proteins cannot be washed or enhanced without sig-nificant protein losses and increasing the overall processcost. One of the limiting factors for the use of these proteinsin food applications is related to the presence of undesirablecolors; thus, to produce canola protein concentrates andisolates that can be used in food formulations, these color-ing compounds must be effectively and economically re-moved. The interactions between phenolic compoundsand canola proteins are complex (Rubino, Arntfield,Nadon, & Bernatsky, 1996). It has been established thatthese compounds in canola proteins interact through a vari-ety of mechanisms in aqueous media, including hydrogenbonding, covalent and hydrophobic interactions, and ionic

bonding. Ionic bonding is very strong, and thus the separa-tion of protein/phenolic complexes is extremely difficult. Inthis way, some studies have attempted to understand thetypes of interactions between canola proteins and phenoliccompounds and identify ways to effectively and economi-cally remove these coloring materials. Xu and Diosady(2000) developed a technique for the quantitative character-ization of canola proteinephenolic bonding in aqueous so-lutions. The proposed approach combined chemicaltreatments, which disrupted specific types of proteinephe-nolic bonds, with membrane separation to remove the re-leased phenolic compounds. It has been reported that upto 50% of the extracted phenolic compounds formed com-plexes with canola proteins by different mechanisms of in-teraction, among which ionic bonding accounted for about30%. It is interesting that this kind of interaction is consid-ered to be the strongest among the interaction types. Xu andDiosady (2000) concluded that the amount of phenoliccompounds bound by canola proteins through hydrophobicinteractions, hydrogen bonding, and covalent bonding didnot exceed 10% of the total extractable phenolic com-pounds. A combination of chemical treatments and mem-brane processes is one of the most promising ways toremove the phenolic compounds (Tzeng, Diosady, &Rubin, 1990).

According to the United States Patent 7678392 (Green,Milanova, Segall, & Xu, 2003), a process for the prepara-tion of a canola protein isolate with improved color fromcanola meal was proposed. The process comprises the ex-traction of the canola meal to solubilize canola proteinsin an aqueous solution at pH 5 to 6.8, the separation ofthe canola aqueous protein solution from the residual oilseed meal, the concentration of the obtained canola proteinwhile maintaining a constant ionic strength of the aqueouscanola protein solution by ultrafiltration, diafiltration of theconcentrated canola protein solution until no significantfurther quantities of phenols and color were present in thepermeate, dilution of the diafiltered protein solution intowater chilled to below 15 �C to form discrete canola proteinmicelles, the formation of an amorphous, sticky, gelatinous,gluten-like canola protein micellar mass, and finally the re-covery of the canola protein micellar mass (protein isolate)with a protein content of at least 90% (w/w).

Undesirable compoundsPhenolics are generally considered to be responsible for

the dark color, undesirable flavour and lower nutritionalvalue of rapeseed products. Rapeseed/canola meal containsfree phenolic acids which constitute up to 24% of the totalphenolic acids present in rapeseed/canola meal and flours.These free phenolic acids represent approximately 15% ofthe total phenolics present in rapeseed/canola meals(Krygier, Sosulski, & Hogge, 1982). Rapeseed/canola pro-tein products contain different phenolics acids such as si-napic, p-hydroxybenzoic, vanillic, gentisic, protocatechuic,syringic,p-coumaric, cis- and tran-ferulic, caffeic and

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chlorogenic acids in the free form (Naczk, Amarowicz, &Shahidi, 1998). These phenolic acids are derivatives of ben-zoic and cinnamic acids. It was found that sinapic acid is thepredominant phenolic acid in rapeseed/canola cultivars.Phenolic acids are present in canola protein products in thefree, esterified and bound forms. One of the limiting factorsof the use of canola meal residue and derivatives (proteinconcentrates and isolates) is that the content of phenolicacids in these meals is up to five times higher than in soybeanmeals and the content of phenolic acids in rapeseed/canolaflours is 10e30 times higher than in flours from other oleag-inous seeds such as flaxseed. It has been reported that freeand esterified phenolic acids are the principal contributorsto the undesirable taste of rapeseed/canola products. Allthe followings phenolics are found in rapessed/canola mealsand derivatives: protocatechuic, vanillic, syringic, gallic,p-hydroxybenzoic, p-coumaric, caffeic,ferulic, sinapicacids. Of these phenolics, sinapic acids constitute 70e85%of the total phenolic acids present (Naczk et al., 1998). Onthe other hand, the flavour of phenolic acids was describedas sour, astringent, bitter and phenol-like. This taste is alsofound in canola meals and proteins. Condensed tannins arealso found in rapessed/canola meal residue and proteins ex-tracted from it. They are dimers, oligomers and polymers offlavan-3-ols. The consecutive units of condensed tannins arelinked through inter-flavanoid bonds between C-4 and C-8 orC-6 atoms. Condensed tannins upon acidic hydrolysis pro-duce anthocyanidins and therefore are also known as proan-thocyanidins. Rapeseed/canola meals may contain up to 3%tannins (Clandinin & Heard, 1968; Shahidi & Naczk, 1989).Proteins are macromolecules and may interact with flavour-ing compounds such as phenolics. The character of these in-teractions influences the flavour release and its perception.Phenolic compounds may form soluble and insoluble com-plexes with proteins. The phenol-protein complexes maybe stabilized by covalent bonds, ionic bonds, hydrogen bond-ing and/or hydrophobic interactions (Shahidi & Naczk,1995). Studies on the complexations of polyphenols withproteins mainly concentrated on the evaluation of factorsinfluencing these interactions and on the impact of formationof phenol-protein complexes on nutritive value of proteins.The phenol-protein interactions are affected both by thesize, conformation and charge density (zeta-potential) ofthe proteins and by the size, and flexibility of phenol mole-cule (Hagerman & Butler, 1981; Naczk et al., 1998).

Even if the proximate composition, nutritive value andfunctional properties of rapeseed/canola meal and deriva-tives (protein concentrates and isolates) are comparable tosoybean products, the use of rapeseed/canola protein prod-ucts as food ingredient is limited by the presence of unde-sirable components such as glucosinolates, phytates, andfibres. The composition of rapeseed has been significantlyimproved by developing low glucosinolate and low erucicacid rapeseed/canola cultivars. Glycosinolates upon hydro-lysis produce nitriles, hydroxynitrites, isothiocyanates andthiocyanates which are responsible for goitrogenic effects.

Erucic acid in the oil may cause heart lesion in certain ex-perimental animals. However, even if the new varieties aresignificantly improved, they still contain too high levels ofglucosinolates. Different approaches such as chemicalmodifications, microbial and physical treatments and theircombinations have been used to reduce the content of glu-cosinolates in meals or seeds to negligible levels. Recently,the use of membrane filtration seems to be promising to re-duce the glucosinolates content in canola protein isolates.Another limiting factor is due to the fact that rapeseed/ca-nola proteins contain up to 4% phytates (Naczk, Diosady, &Rubin, 1986). Phytates are responsible for the decrease inthe bioavailability of divalent cations such as Ca, Mg, Zn,Cu and Fe. This is a result complex formation (chelating ef-fect). Phytates are also known to inhibit the digestion ofstarch. Because of this, a number of methods have been de-veloped to remove phytic acid from rapeseed products(Naczk et al., 1998). On the other hand, some recently pub-lished studies indicate that phytates, at low concentrations,may possess antioxidative and anticarcinogenic effects(Rickard & Thompson, 1997). Rapeseed meal contains upto 20e30% indigestible fibres on a dry basis. The rapeseedfibres are low-molecular-weight carbohydrates, polysaccha-rides, pectins, cellulose and lignin. Generally, they are com-plexed to proteins, polyphenols, glucosinolates andminerals. High levels of fibres limit the use of meal asfood ingredient. Dehulling of rapeseed/canola has been pro-posed but it is still not efficient and therefore dehulling isnot a standard practice in canola processing (Naczk et al.,1998).

Food applicationsCanola proteins are characterized by interesting func-

tional properties that allow them to be used as ingredientsin different food formulations. Native and partially hydro-lyzed canola proteins have been extensively studied for po-tentials uses in the food industry to replace classicalingredients, such as milk whey and egg yolk. This approachis mainly justified by economic considerations and possiblewhey/egg allergies in customers. In this context, an alkalineextract of canola meal was hydrolyzed using a protease toobtain protein hydrolysates with 7% and 14% degrees ofhydrolysis (DH), respectively. The protein hydrolysateswere used to replace up to 50% (w/w) of the egg yolk ina model mayonnaise preparation, and the effects on thephysicochemical properties of the end product were deter-mined. It was found that unhydrolyzed canola proteinscould only be substituted in mayonnaise for a maximum15% (w/w) of the egg yolk without emulsion breakdown.According to the authors, at 7% DH, the canola proteincould be used to substitute up to 20% (w/w) of the eggyolk, while at 14% DH, the maximum level of substitutionwas up to 50% (w/w). However, some problems, includingthe dark color of the canola protein solution, still need to besolved before the use of canola protein can be extended tofood formulations. Aluko and McIntosh (2005) reported

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that increasing the level of canola protein products in may-onnaise reduced the whiteness and increased the reddish-brown color. Mayonnaise that was stabilized by only eggyolk had the lowest particle size and highest viscositywhen compared to emulsions stabilized by canola proteins.Stability studies showed that most of the mayonnaise prep-arations retained their physicochemical properties afterstorage for 4 weeks at 4 �C. The results suggest that limitedprotein hydrolysis can be used to increase the incorporationof canola globular proteins into mayonnaise preparations(Aluko & McIntosh, 2005).

Canola protein hydrolysates were also studied as a poten-tial ingredient in meat formulations to enhance some organ-oleptic attributes. Canola hydrolysates were found to beeffective in enhancing the water holding capacity and cook-ing yield in a meat model system. Their capability to im-prove the cooking yield of meat was dependent on theenzyme type. These results suggest that canola protein hy-drolysates can be useful as functional food ingredients andthat their composition determines their functional proper-ties and thus their potential applications in the food industry(Cumby, Zhong, Naczk, & Shahidi, 2008). A canola (rape-seed) protein concentrate was used as an additive to replacecasein in a sausage formulation. The used canola proteinconcentrate was steamed and added to sausage preparationsin place of casein, and a sensory analysis showed that therapeseed protein sausage had improved taste, good textureand a characteristic aroma (Yoshie-Stark, Wada, Schott,& W€asche, 2006). An interesting study reported the gener-ation of meat-like flavorings from enzymatic hydrolysatesof proteins from canola/rapeseed (Brassica sp.) (Guo,Tian, & Small, 2010). It was shown that the control ofpH and temperature is very important during the generationof flavoring following enzymatic hydrolysis of Brassica sp.proteins. The formation of meat aroma compounds was fa-vored under lower pH conditions; at low temperatures, thearoma was similar to that of cooked meat, and at highertemperatures, it was like roasted meat. From the variousconditions studied, the best favored products were gener-ated at 160 �C and pH 4.0, and products with a burntodor were produced at pH 8.0 and 180 �C. GCeMS analy-sis demonstrated that most of the compounds in the reactionproducts occur naturally in foods and have previously beenidentified in model systems. The enzymatic hydrolysates ofBrassica sp. proteins can be used as the primary ingredientfor the production of thermal processing flavors that havemeat-like characteristics (Guo et al., 2010).

Canola proteins and allergenicityCanola/rapeseed is used for edible oil production. Be-

cause it has high protein content, the presence of tracesof protein in the final oil is extremely difficult to prevent.It is well recognized that the role of proteins in the allerge-nicity of edible oils is a growing problem. According to theavailable scientific literature, 5e8% of infants and childrenand 1e2% of adults exhibit food allergies. Eight food

groups account for more than 90% of all IgE-mediatedfood allergies worldwide and include milk, eggs, fish, crus-taceans, peanuts, soybeans, tree nuts, and wheat. At thesame time, it was reported that more than 160 other aller-genic foods are responsible for the other 10% of reactions.Food allergies also include some seeds that are usually usedfor producing edible oils, such as cottonseed, sesame,poppy, and sunflower. The causative agents of food aller-gies are proteins and are naturally occurring. They are gen-erally characterized by high resistance to heat treatmentsand digestion. Among all edible oil sources, it has beenreported that olive and canola are nonallergenic. Othersources, such as corn and coconut, are rarely allergenic.Sunflower, sesame, and cottonseed belong to the group offoods that are less commonly allergenic. And peanuts, soy-beans, and tree nuts belong to the eight groups of com-monly allergenic foods. The problems related to edibleoil allergenicity occurs when oils are extracted from seeds.In this process, some of the allergens pass into the oil, andboth cold pressed and fully refined oils have been shown tocontain allergens. For example, it was found that both cold-pressed and fully refined soybean oil had 56- and 28-kDaallergenic proteins (Hidalgo & Zamora, 2006). However,because the allergens are proteins, it appears premature toconclude that canola/rapeseed proteins are not allergenic.This statement must be confirmed by further studies, andvalid data on the allergenicity of these emerging proteinswill be available only after the consumption levels ofcanola proteins are similar to soy proteins.

Cross-reactivity was studied using sandwich enzyme-linked immunosorbent assay (ELISA) for the detection ofmustard in foods (Lee, Hefle, & Taylor, 2008). Ingredientscommonly found in foods in association with mustard wereanalyzed to further explore the possible matrix effects andto evaluate the specificity of the antisera. These mustardELISAs are specific for the detection of mustard residues,except for rapeseed. A total of 109 common foods andfood ingredients, including foods derived from the Brassi-caceae family, were evaluated and, with the exceptionof rapeseed, showed no reactivity in these ELISAs andresponses equivalent to < 1 ppm of mustard. A rapeseed(canola) sample containing 12 mg/mL of protein displayedstrong cross-reactivity in both the rabbit capture(12300 ppm) and the sheep capture (16900 ppm) mustardELISAs. The cross-reactivity with rapeseed was expectedas it has been reported that the 2 S albumin seed storageproteins in mustard seeds shared 94% sequence similaritywith 2 S albumins from rapeseed/canola (Monsalve et al.,1997, 2001). Because rapeseed/canola and mustard areclosely related plants, similarities would also be expectedbetween other proteins in the 2 species. The sequence sim-ilarity allows for binding of the mustard-specific antisera tothe cross-reactive epitopes on these proteins (Koppelman,2006). This cross-reactivity between mustard and rapeseedwill generally not affect mustard detection in foods becauserapeseed is used mainly in the production of canola oil or

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for animal feed; however, caution must be exercised whendetecting mustard in foods that may have come into contactwith rapeseed. Puumalainen et al. (2006) published a studyin which it was confirmed that Napins, 2 S albumins, aremajor allergens in oilseed rape and turnip rape.

Monsalve, Villalba, and Rodr�ıguez (2001) publisheda study which was aimed for the detection, isolation andcomplete amino acid sequence of an aeroallergenic proteinfrom rapeseed flour.The present study was justified bya fact that seed proteins have been found to cause hypersen-sitivity by ingestion or inhalation. Rapeseed flour wasresponsible for allergic symptoms in a patient, who de-velops into allergy to mustard spice. Thus, according tothis study, it seems that similarities can be found betweenthe allergenicity of mustard and canola/rapeseed. In thisstudy, the main objective was to determine the presenceof allergenic proteins in rapeseed flour, and analyse thestructure of the main component and its cross-reactivitywith the mustard allergens. The methodology followed bythe authors was based on SDS-PAGE (sodium dodecylsulfate-polyacrylamide gel electrophoresis) and subsequentimmunoblotting with a serum from a rapeseed allergicpatient were performed to detect IgE-binding proteins. Pro-teolytic digestions and high performance liquid chromatog-raphy were used to obtain the peptides from the allergenicBnIII napin from rapeseed flour. Automatic Edman degra-dations were carried out to determine their amino acidsequences, which were compared with other sequences innucleotide and amino acid sequence databases. Cross-reac-tivity assays were carried out by ELISA inhibition usingsera from a rapeseed allergic patient and from patients al-lergic to mustard. The obtained results showed that the2 S albumins of rapeseed were recognized by the serumfrom a patient allergic to this seed. The most abundant iso-form of the allergenic napins, was used for structural andimmunological analysis. The protein consists of two differ-ent chains of 9.5 and 4.5 kDa. Their complete amino acidsequences were determined. The protein exhibited struc-tural relationships with other napin-like storage proteinsfrom seeds. IgE and IgG cross-reactivity between rapeseedand mustard allergens was also demonstrated. Consideringthe structural and immunological data, certain polypeptideregions are suggested to be involved in the allergenicity ofthese proteins. In conclusions, the authors stated that rape-seed contains 2 S storage proteins which may cause allergyin hypersensitive individuals. These proteins exhibit greatsequence similarity with 2 S albumins from different seeds.Cross-reactivity between mustard and rapeseed flours canbe explained by sequence homology.

ConclusionThis literature review has highlighted the amino acid

compositions and protein fractions of canola proteins.The examined scientific literature showed that canola pro-teins have good amino acid composition that allows themto be used for the formulation of foods with acceptable

nutrition quality. However, a structured approach couldimprove the nutritive potential of these proteins; a combina-tion of canola proteins with other proteins would compen-sate for the deficiency or lack of certain amino acids. Thefunctional properties of canola proteins were interestingand could be applied to targeted food formulations. Amongthe functional properties of canola proteins, solubility andfoaming ability appear to be the most promising. However,protein modifications seem to improve the emulsifyingcapacity of these proteins, which increases their potentialapplications in food matrices based on an emulsion-typeformula. Canola proteins also have the potential to beused as a source for economical production of bioactivepeptides for nutraceutical applications. This line of investi-gation is relatively unexplored, and research in this direc-tion could lead to interesting discoveries. However, likeall vegetable proteins, canola proteins have deficienciesthat need to be absolutely overcome, including improvingits color and flavor. Successful improvement of these attri-butes would be a crucial key to expand the spectrum ofapplications of canola proteins.


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