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Evolution in dough ingredientsThe migration of water, theinfluence of water content andthe increase in temperatureduring dough formation havebeen the subject of a number ofstudies in recent years.Some testing has examineddoughs with a range of mois-ture content which were thenheated by conventional meansto various temperatures. Watercontent was monitored with aprobe throughout the conven-tional heating in three points:at the centre of the samples,midway between the centreand surface layer and on thesurface layer.The rheology of the samplessubjected to heat treatment wasmeasured using stress tests, themicrostructure of the sampleswas evaluated using CLSM(Confocal laser scanning micros-copy), while microstructuralparameters were evaluatedusing image analysis.
The most significant resultsshowed that there was abso-lutely no water migrationwithin the dough up to an inter-nal sample temperature of 80°C;clear confirmation also exists toindicate that water content andheating range have a bearing onthe rheologic and structuralproperties of the dough.In dough samples with highmoisture levels, the formationof the gluten lattice structure ismore pronounced and reducesthe hydration capacity of thestarch particles; similarly, lowmoisture levels produce a looserprotein lattice structure thatfacilitates starch hydration.At higher temperature, starchparticles have less time toabsorb water, thus causing anincrease in the swelling temper-ature.Rapid heating subjects the pastato increased structural deforma-tion and leads to the formationof smaller pores; it could be that
the size of the pores has a bear-ing on the sample’s capacity toresist stress before breaking.Low moisture samples havesmaller-sized pores. The energyrequired to obtain breaks in therapidly-heated dough is higherthan that in samples heatedslowly (Thorvaldsson, K. et al.,1999).Evaluation of the variation ingluten strength, rheologic prop-erties and cooking quality ofspaghetti has shown increasedinvolvement of the protein frac-tion of hard wheat not soluble inwater. The viscosity of thedissolved gluten in a suitablebuffer is strictly correlated to theamino acid balance of theproteins, with the strength ofthe protein lattice structure thatis formed and the cooking qual-ity of the spaghetti (Dexter, J.E.et al., 1980).Pasta quality is influenced notonly by the protein content, butalso the properties of the
IS PASTA AS GOOD AS IT USED TO BE? SOME SUGGESTIONS
FOR A “NEW” PRODUCT WITH 2000 YEARS OF HISTORY
Alessio Marchesani - Ilaria Soncini
Food industry research continues tobear new fruit. To bring ourselvesup-to-date, we undertook a surveyof leading international publica-tions and what follows is oursummary of the technical and tech-nology-related informationcontained in the articles, edited tomake it more accessible. We areconfident that a close study willprovide the basis for a wealth of newideas as well as new applications fortechnologies already in use.
starch. As a matter of fact,although gluten remains theprimary agent involved on anultra-structural level, starch isalso involved, since glutenforms a protein network thatretains it and lends body andstructure to the product. Thesecharacteristics, together withthe hydration capacity of thestarch and its gelatinizationproperties, are the principlequality attributes in pasta(Delcour, J.A. et al., 2000).The removal of surface proteinsand lipids from starch particlesclearly influences both rheologicand structural properties, butnot interaction with othercomponents. Lipids andproteins present on the surfaceof starch particles do not influ-ence the latter’s interactionwith gluten which is primarilyconnected with phenomena ofphysical inclusion of theamylaceous particles by thegluten lattice structure. Highdrying temperatures promoteformation of the protein latticestructure that renders starchparticles less educible andlimits their gelatinization and
swelling during cooking. As aconsequence, the quality andquantity of this lattice structureare correlated to the physicalproperties of the cooked pasta(Vansteelandt, J. et al., 1998).
Starch and GlutenDuring kneading, the hydro-gen and hydrophobic sulfidebonds that affect the proteinsare partially split and the mainresult is a change in solubility,which generally increases. Thisis caused by the decrease in thesize of the protein compoundsfollowing the disaggregationand depolymerization of thegluteninic sub-units of heavymolecular weight.During the extrusion phase, theproteins are denatured and thechemical bonds are weakened asa result of the rise in temperatureand the mechanical action of thescrew conveyor and die on thedough. The primary result is areduction in protein solubility.The changes encounteredduring the kneading phase canbe more evident than thedifferences normally encoun-tered between various types of
wheat. Lamination reducesgluten content and increasesprotein gel. This could becaused by the increase intemperature during lamination(as a result of the mechanicalenergy provided) that dena-tures the proteins (Hayta, M. etal., 2001).In soft and hard wheat, starchgelatinization is not completedwithin a temperature range of60°C and 100°C; the final degreeof gelatinization (FDG) of softwheat starch is higher, both inthe lab and on-site, and theprocess kinetics are higher.These differences are due to thevariation in structure andtexture of the two types ofwheat.The aspects mentioned formthe basis of the different waysthe two types of wheat behaveduring pasta making. As amatter of fact, during produc-tion of dry pasta, gelatinizationis quite undesirable because itnoticeably reduces pasta qual-ity during cooking by makingits texture less resilient to cook-ing and promoting the loss ofstarch part ic les from the
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protein lattice struc-ture, making the prod-uct sticky (Turhan, M.et al., 2002).During the first doughdrying phase, thestarch particles (espe-cial ly the smallerones), become lesseducible, probablydue to the interactionwith the gluten andphysical/structuralincorporation. Thesechanges are not tied toeither the amylosecontent or the struc-tural variations intheir alignment withinthe dough, given thefact that the environ-mental temperatureand humidity do notpromote these varia-tions.The majority of thechanges observedregarding starchbehaviour are seenduring the first dryingphase even if, in real-ity, they should also beevident during otherphases of pastadrying. As a result ofthe changes under-gone by the starch,there should be areduction in viscosityand gelatinizationtemperature and anincrease in swellingand solubility.In particular, hightemperature dryingtreatments provokemost changes in thechemica l -phys ica lcharacterist ics ofstarch, with a conse-quent hardening of
the structure and decrease in the solubility andswelling capacity of the particle. This leads moregenerally to a loss in permeability and a reductionin amylose loss during the product cooking phase(Vansteelandt, J. et al., 1998).In terms of gluten, drying at high temperaturescauses a reduction in its content with consequentformation of protein gel and increase in its latticestructure.At low temperatures, starch undergoes verydifferent types of change. At moisture levels ofover 30%, it takes on a definite regular lamellarstructure. During freezing, the expansion of thefree water outside the lamellae causes thesemi-crystal lamellar structure in the particles tocompress; contrariwise, the more rigid crystallinefraction remains predominantly unaltered. Thisis because the unformed lamellae themselves actas cushions to absorb the compression pressure,thus protecting the crystal structure. Once maxi-mum compression has been reached (with areduction in volume of up to one-third the initialvalue), if further stress is applied, the lamellae arebent out of shape losing their perpendicularalignment, and a wavy structure is created withinthe semi-crystal growth rings.This occurs above all in starches with a low percent-age of amylose (i.e., corn), that are therefore moresensitive to freezing. From this it can be deducedthat amylose is critical in response to applied stress.An initial hypothesis would suggest that the pres-ence of amylose within the unformed lamellaecould limit the amount of compression possible to acertain degree; the entanglements between thelinear amylose chains and amylopectin helixescould react as a type of temporary physicalcross-link, rendering the unformed lamellae fairly
rigid and incapable ofbeing compressed.A second hypothesisconcerns the presenceof amylose withinunformed particle areaswhich could act as“diluent”, reducing thecoupling between theamylopectin branchesin the neighbouringlamellae, as well as thetransmission of stressthrough the particle.More generally, itcould be stated thatlow temperatures donot cause significantdamage to the starchpart ic le structure.Those changes that dooccur are completelyreversible followingheating. Even follow-ing a freezing/thaw-ing cycle, no signifi-cant damage is noted(Perry, P.A. et al. ,2000).Following thawing,complex foodstuffspreserved at lowtemperatures couldundergo structuraldamage, underminingproduct integrality.Temperature fluctua-tions during storagelead to re-crystal-lization that has drasticeffects on producttexture.The ice crystals formedgradually increase insize and create internalrupturing. Starch gel,like other gels withhigh water content, areparticularly susceptibleto this type of damage.
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The evolution of the phasesthat make up the freezingprocess (nucleation, crystalpropagation, maturation) isinfluenced by the ingredientsin food products.Hydrocolloids are frequentlyused as additives to control thetexture and stability of frozenfoods. Polysaccharides, espe-cially, could cause a significantreduction in the presence ofgrowth of ice crystals, but theexact mechanism involved isnot known. Polysaccharidesolutions increase the viscosityof the system, although thisdoes not seem to be the deter-mining factor in the growth ofice crystals. In fact, it has beennoted that there is a reducedcorrelation between viscosityand crystal development,while their steric hindrance issignificant. As they expand,they are trapped within thepolymeric chains, the result ofwhich is the formation of poly-mer gel that reduces crystalliza-tion in relation to the level ofbranching and gel strength.Polysaccharides of variousorigins and shapes, such asxanthane (complex, hel i-cal-shaped polymer) andgalactomannan (with linearstructure and galactose sidechains), do not gelatinizeexcept when used simulta-neously, influencing ice crys-tallization using differentmechanisms. Therefore, thepresence of polysaccharideadditives can influence freez-ing stability of starch gel to agreater or lesser degree,depending on its origin andinteractions produced (Lo, C.T.et al., 2000).
Microscopic analysis andstructural evaluationThe microscope is the mostuseful instrument for studyingthe structure and changes instarch particles. Non-invasivestudy of particles using polar-ized light is the simplest andmost useful for monitoring theinternal changes that take placeduring the growth, storage andprocessing of the kernel.Following prolonged contactbetween starch and a liquidmedium, surface exudationfrom the inside towards theoutside of the medium can benoted. This could be importantfor its behaviour in varioustransformation stages: swell-ing, agglomeration and main-tenance of granular appear-ance of the processed product.Illumination of the starch parti-cles using polarized light andlaser rays perpendicular to thepolarized light ray guaranteesthat exudation can be observedthrough an optical microscope(Starzyk, F. et al., 2001).Recently, a fairly new tech-nique, CLSM microscopy, hasbeen introduced for the struc-tural analysis of biological andalimentary material. Unlike theoptical microscope, the lightsource is replaced by a laserwith a scanning unit and suit-ably-sized hole in the rear focalplane that improves the limitedfocusing depth. This systemhas proved useful for obtainingthree-dimensional informationon the structure of tuber paren-chyma and the properties ofprotein and amylose lattices inwheat-based products. It mayalso be used to study the surfaceproperties of pasta through“reflectometric” examination(Durrenberger, M.B. et al., 2001).
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The high resolution electron microscope mayalso be utilized to study the microstructure ofdry or cooked pasta if a sample is preparedthrough freezing and fracturing.Pasta represents an interesting water-starch-protein system in which, during processing andcooking phases, competition over water iscreated between the starch and protein thatgives rise to structural changes and two-wayinteraction. Understanding of these phenom-ena can be enhanced by studying the “fine”structure of pasta. In this case, it has been shownthat the “freeze-fracturing” method mentionedabove is one of the most effective methods forobserving the heat-induced modifications onthe starch ultrastructure in systems with lowwater content. These are not easily observableusing other electron microscopy methods (Lo,C.T. et al., 2000).
Microwave heatingAnalysis of various microwave-treated samplesreveals an inverse correlation between thefrequency utilized and the sample temperature.This occurs because radiation penetration andenergy absorption are more efficient at lowfrequencies (e.g., 900 mHz). However, on an
industrial level, higher frequency levels arepreferred because it is easier to control thetemperature within the food matrix.When using microwaves, the shape (size andsymmetry) of the sample and the direction of therays are of fundamental importance and boththese variables have a direct bearing on uniformenergy distribution. The presence of a highcontent of ionic solutes influences heating effi-ciency: given the same sample and parity ofconditions, high concentrations produce highertemperatures.Of special interest is the diffusion of heat withinthe sample. If the sample is fairly large, heat isdiffused slowly from the surface towards theinterior, while if it is small, heating occurs moreevenly.Axial rotation of the samples and productionsystem with on/off cycles represents a techno-logical improvement (Oliveira, M.E.C. et al.,2002).Given the high kinetics, heated amylose prod-ucts have lower starch gelatinization. Micro-wave heating of moist solid products creates apositive flow of water towards the outside andcauses an increase in internal steam pressurewhich also enhances surface evaporation(Sumnu, G., 2001).Recently, microwave technology has also beenintroduced into the pasteurizat ion ofpre-packaged, ready-to-serve products. This hasproven to be an excellent solution because thevolumetric transfer of heat assures rapid heatingof the package contents, thus avoidingprolonged autoclave treatment that is moreharmful for heat-sensitive substances (nutrientsor organoleptic components).
High pressureA number of different products may be treated,but they must possess some common character-istics: minimum water content, not be overly-porous (given temporary deformation duringtreatment) and must be packed in flexible pack-aging materials. This technique makes it possi-ble to treat semi-processed products inlarge-size packages as well as consumer foods. Italso has very low environmental impact becauseno polluting emissions are produced.There is significant published research onlow-acid foods sanitized using high pressure
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and low temperatures. However, the problem ofmicrobial spores cannot be solved through theuse of high pressure alone - high temperaturesmust also be employed.Data is available regarding the destruction ofBacillus stearothermophilus (one of the mostheat-resistant bacteria) in the range of 6 decimalpoints with a treatment at 600 MPa (approx. 6000atm) and temperature of 70°C for 5 minutes,repeated 5 times (Hayakawa, I. et al., 1994).Other methods (Pulsed High Pressure, PHP)make use of initially low pressure cycles (60MPa) that subsequently increase (500 MPa), at atemperature of 70°C. If the cycle is repeatedapprox. 10 times, any spores present are alsoeliminated because they germinate betweencycles and are deactivated by the succeedingcycle (Sojka, B. et al., 1997).In recent studies, thanks to significant testing,the exact ideal conditions for obtaining sanitiza-tion of certain products such as macaroni andcheese have been identified.Strains of Clostridium sporogenes and Bacilluscereus were used as indicators of successful treat-ment, with significant attention given to theinitial spore level, treatment times and tempera-tures as well as number of cycles.With the use of fairly low temperatures, it isobvious that final product quality is enhanced.However, this also depends on the quality of thepackaging (suitably designed and adapted tothe chemical/physical features of the product)and the fluid used to exert pressure (Meyer, R.S.et al., 2000).In terms of starch, treatment at a few hundredMPa causes the gelatinization with characteris-tics quite different from that obtained throughheating. In particular, the particle structure -completely destroyed by heat - remains intact.In the pasta industry, this type of treatmentcould be used for “mild” pasteurizing of pack-aged fresh pasta or ready-to-serve pasta disheswhose organoleptic qualities are stronglyaffected by higher temperatures.
Modified atmosphereThe chemical/physical principles on whichmodified atmosphere packaging (MAP) is basedcall for the replacement of the atmospheresurrounding the product with a special mix ofgas, in conjunction with refrigeration. The
results that can be obtained through this packag-ing technology are a reduction in the rate of manybiochemical processes that cause product deteri-oration and, more generally, the inhibition of thegrowth of contaminating micro-organisms. Thepreserving action of the gas is enhanced byrefrigeration that reduces the speed of microbeproliferation and enzymatic reactions ingeneral, the primary causes of organolepticdecrease of the product. Through study of“balanced” dishes, it has been verified that, froma nutritional standpoint, initial product charac-teristics remain substantially unchanged withMAP.A number of tests performed on ready-to-servepasta dishes show that the fatty acids (and peroxyacids) in the event the pasta was prepared withanimal fats, remains unchanged, whereas vege-table pasta reveals a higher level of peroxides,probably due to a residual oxidative-type enzy-matic reactivity. Failure to blanch fresh vegeta-bles and the mild way they are cooked couldexplain the continued presence of an oxidativeprocess and, therefore, the high number ofperoxides found in this type of product.To evaluate suitability and trends in preserva-
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tion technology, oxidation
reactions for β-carotene andvitamin E were monitored. Thedata collected confirms that themaintenance of samples inoptimal condition throughouttheir shelf-life does not alterthese quality indices.Comparing freezing technol-ogy with MAP, the percentageof resistant starch formed dueto retrogradation was also eval-uated. The results obtained donot show any differencesbetween the two preservationmethods.Overall, the results of the anal-yses performed on samplesshowed that, for the nutritionalprinciples evaluated, a combi-nation of modified atmosphereand refrigeration technologiesis capable of conserving the
nutritional value of a productfor over three weeks. The use ofpositive temperature MAP toavoid the formation of ice crys-tals, results in a product withbetter texture and flavour thanthe same product when frozen.On the other hand, it must beconsidered that the efficacy ofMAP in guaranteeing the qual-ity of both a single productcategory and a prepared dishdepends on the quality of theraw materials and preservationmethod (Simpson, M.V. et al.,1994).
Hygienic quality and shelf-lifeof fresh pastaFilled fresh pasta is often modi-fied atmosphere packaged. Inthis type of product, primarilybacillus-type bacteria have
been isolated, but no patho-genic bacteria.As a result of the variety incomposition and heat treat-ments which the samples pres-ent on the market have beensubjected to during produc-tion, shelf-life at 4°C variedgreatly, from less than 3 days toapproximately 30. The resultsobtained suggest that theshelf-life for this product cate-gory is not just influenced bythe number of bacteria cellsthat have survived heat treat-ment, but also by themicro-structural and texturechanges caused by the treat-ment itself. Through testing, itwas seen that Staphylococcusaureus cel ls reproduce attemperatures over 7°C, espe-cially if the water activity valueis greater than 0.97 (ChavesLopez, C. et al., 1998).From the findings of a particu-lar study on the parameters (awand pH) that influence micro-bial proliferation in filled pastaand gnocchi, it emerged thatsome products available on themarket have values that wouldallow the germination ofClostridium botulinum spores.This microbial development isclearly favoured only in modi-fied atmosphere packagedproducts since this is strictly ananaerobic pathogen. This givesrise to the need for enhancedmonitoring of the aboveparameters, as well as storagetemperature (not to exceed4°C), in order to guarantee highlevel product safety (Schebor,C. et al., 2000).
Technology and qualityFor an evaluation of the effectof high pasta drying tempera-tures, an analysis of pasta cook-
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ing quality and starch proper-ties was made. The most signifi-cant results indicate that betterf inal product quali ty isobtained using the VHT (VeryHigh Temperature) methodrather than the HT (HighTemperature) method. It isimportant to stress that it is thechanges in starch particleshape during drying that influ-ence, above all, the pasta’scooking properties, reducingthe levels of starch loss (Güler,S. et al., 2002).Unfortunately, these dryingtreatments promote theunwanted formation of Maillardcompounds.At temperatures lessthan 120°C it is very low, while at150°C it increases seven-fold. Thecoloured molecules with lowmolecular weight are trapped inthe lattice formed by the glutenprotein with high molecularweight, giving the product abrownish tint (Fogliano, V. et al.,1999).Knowledge of redox phenom-ena caused by oxygen reductaseand mechanisms of this reactionduring dough making isextremely important.The study of peroxidase,p o l y p h e n o l o x i d a s e ,l ipoxigenase and catalaseenzyme activity has made itpossible to better understandthe productive phases in whichtheir effects become importantin light of some special qualita-tive characteristics of pasta,such as colour and cookingquality. Polyunsaturated fattyacids are easily oxidizable andproduce a negative evolutionnot only in organoleptic qual-ity, but above all in structure,negatively impacting onvisco-elasticity and stickiness(fundamental characteristics in
the cooking phase). Just asimportant would be an exami-nation of the effect of redoxphenomena on the structuralproperties of the gluten, on theevolution of phenolic compoundsand carotenoid pigmentswhich lead to a loss in colour(yellow) and “gloss” of thefinished product (Icard, C. etal., 1997).In fatty flour extrusion technol-ogy, the use of additives influ-ences the loss of the product’slipidic fraction. If the lipidiccontent is high, there is a highand unwanted reduction in fatsduring the extrusion and toast-ing phases. Using electricalconductivity analysis, it hasbeen shown that lecithin (asopposed to gum arabic andguar) is the best additive forpreventing the loss of fat inoil/water emulsions.A pilot production of extrudedflakes from pre-gelatinizedrice, wheat and almond flourswith added soy lecithin,subjected to rheologic, chemi-cal and physical tests, as well assensory analysis, has shown, inaddition to lecithin as an addi-tive, wheat flour is the best basefor the production of almondsnacks (De Pilli, T. et al., 2001).
A
Acids (polyunsaturated fatty)
Fatty acids that possess more than one double bond
between carbon atoms within a hydrocarbon chain.
They are generally of vegetable origin and have
greater resistance to oxidation than saturated fats
thanks to the double bond between them.
Amylopectin
Main component of cereal and tuber starch, formed
by branching glucose chains.
Amylose
Portion of the starch composed of long linear glucose
chains; comprises approx. 20% of cereal starch.
Amino acid
Organic compounds which, through special chemi-
cal bonds, form the basis of protein structures.
C
Catalase
Enzyme* that promotes the decomposition of hydro-
gen peroxide with the production of oxygen gas.
Catalyst
Substance that increases the speed of a chemical
reaction without undergoing transformation or any
other type of chemical change.
CLSM (Confocal Laser Scanning Microscopy)
New microscopy technology that makes it possible to
produce an optic section of a sample through the use
of a laser beam. The progressive shift of the focal
plane towards the interior of the sample makes it
possible to obtain complete 3-dimensional images
of the product.
Cooking quality
When referring to pasta, all those characteristics that
give cooked pasta the best appearance and texture.
It may be quantified through measuring such param-
eters as elasticity, bite, surface stickiness, water
absorption, cooking resistance, amount of swelling,
etc.
D
Dough
Product obtained by the mixture of raw materials (for
example, water and semolina) in the correct propor-
tions. Correct preparation, fundamental to obtain-
ing a quality product, requires uniform hydration of
the solid particles (semolina, flour) with subsequent
gluten formation.
E
Enzyme
Protein that acts as a catalyst* in biochemical reac-
tions; each enzyme is specific to a given reaction or
group of similar actions.
F
Freezing (crystal nucleation, propagation,
maturation)
Method of conservation at low temperatures (no
higher than -18°C). There are three different phases
in freezing. Nucleation begins with the appearance
of pointed ice crystals, normally around 0°C to -7°C;
propagation increases ice nuclei through the addi-
tion of new small crystals; maturation is attained
when most of the water has been frozen.
G
Galactomannan
Polymer of galactose and mannose present, in
particular, between legume glucides and yeasts.
Galactose
Simple sugar, it has the same chemical formula as
glucose, but with a different atomic arrangement.
Gelatinization
Surface modification of the amylaceous seed
through the combined effect of heat and moisture. A
gelatinized starch takes on new chemical/physical
properties; an impermeable film forms on the prod-
uct surface that reduces the loss of hydro-soluble
nutrients during soaking or cooking in water.
Gluten (gluten lattice)
Gluten is a protein compound comprised of gliadin
and glutenin*, protein fractions present within the
wheat kernel. In flour and semolina, these proteins
are separated, but in the presence of water (knead-
ing phase) they become hydrated, creating a
complex structure. The gliadins take on a fibril shape
(dough extendibility), while the glutenins become
more compact in structure. Together they form a
lattice that captures the starch particles present in
the flour to form the dough.
Glutenin (gluteninic sub-unit)
Proteins with a distinct tendency to combine, primar-
ily through hydrogen bonds, sulfide bridges and
hydrophobic* interaction. Following the severing of
sulfide bridges in the presence of a reducer, a
number of sub-units with different molecular weight
and characteristics are formed. Together with
gliadin, makes up gluten.
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GLOSSARY
H
Humidity
Absolute amount of water contained in the atmo-
sphere.
Hydrocolloids
High molecular weight polysaccharides with hydro-
phobic and hydrophilic areas; this guarantees their
emulsifying and thickening properties on localized
elements in the aqueous phase of a food product.
These products (natural or man-made) are used as
additives to lend viscosity or gelification to a food
product.
Hydrogen bond
Type of electrostatic interaction between molecules
with hydrogen atoms bonded to other atoms such as
fluorine, nitrogen and oxygen.
Hydrophilic
Substance with an affinity for water, rendering it
soluble in water.
Hydroperoxide
Product of the oxidation of a fatty acid.
Hydrophobic
Substance with little (or no) affinity for water because
of its molecular structure, rendering it insoluble in
water.
I
Ionic solutes
Substances dissolved within a matrix in the form of
ions (molecules or atoms with an electrical charge).
L
Lamination (of the dough)
The dough* may be laminated by passing through
rollers set variable distances apart. Through this
operation, the pasta is stretched to reduce sheet
thickness. Passage through a series of rollers that are
increasingly close together creates the desired
dough thickness. A series of passes instead of just
one is used to avoid the dough being subjected to
excessive compression.
Light polarization
Process by which the vibrations of the electrical
vector of the light waves are forced along a single
direction.
Lipoxygenase
Enzyme* of vegetable and microbial origin, respon-
sible for the oxidation of polyunsaturated essential
fatty acids to produce hydroperoxides*.
Lipoxygenase action provokes the destruction of
oxidizable liposoluble vitamins.
M
Maillard Reaction, Compounds
Reaction that takes place between an amino acid*
and a sugar during prolonged heating (or at very
high temperatures) of a food. Among the final prod-
ucts of this reaction are dark compounds responsible
for the non-enzymatic browning of the food surface
and volatile compounds responsible for aroma. In
general, the intensity of the reaction is proportional
to the amount of heat, increases as pH increases and
is at its maximum at a relative humidity of between
40% and 70%. It should be stressed that in some
products it is undesirable (for example, in dry pasta),
while in others it is an essential aspect of the product
itself (e.g., bread).
Mannose
Simple sugar, it has the same chemical formula as
glucose, but with a different atomic arrangement.
Microbial spores
Forms of resistance developed by certain types of
micro-organisms in order to survive in unfavourable
environments. They are very resistant to external
agents, heat in particular, and are capable of
re-germinating once conditions optimal to them
have been restored.
Microwave heating
Electromagnetic energy, absorbed primarily by
water, causes friction on a molecular level that is
translated into heat loss. The microwaves heat the
food from the centre, not from the surface. Biochem-
ical effects seem comparable to those observed
using traditional methods.
“Mild” pasteurization
Pasteurization is utilized to obtain a hygieni-
cally-safe product. Its purpose is to destroy the
saprophyte and pathogenic microbial level present
in a food, generally through a heat treatment. The
adjective “mild” indicates the use of technologies
that do not impair the nutritional and organoleptic
characteristics of a food (as do microwaves or high
pressure, for example).
Modified atmosphere packaging (MAP)
Packing technology used for perishable products to
extend shelf-life. Consists of the elimination of air
within a package and its substitution with a mixture
of inert gases (normally carbon dioxide and nitro-
gen). The function of the gases is to block the prolif-
eration of certain micro-organisms (does not affect
Gram positive bacteria) and certain enzymes, but
without altering the food product. The packaging
utilized must be impervious to gas and water in order
to avoid exchange with the outside environment.
MAP products must be refrigerated to guarantee a
level of stability over time. However, much of
shelf-life depends on the initial characteristics of the
food product (pH, quality of ingredients, initial level
of contamination).
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P
Peroxidase
Enzyme that promotes substrate oxidation in the
presence of hydrogen peroxide and peroxides.
Polarized light
Light beam that behaves differently in all directions
around the propagation beam. Polarized light is
differentiated from natural light by the fact that its
vibrations, instead of being directed in all directions
perpendicular to the propagation vibrations, follow
defined trajectories.
Polymer
Substance made up of giant molecules formed by
smaller, repeating structural units.
Polypeptides, polypeptide chains
Organic compounds which, organized in complex
structures, form the basis of complex proteins. They
are comprised of chains of 10 or more amino acids*
joined together.
Polyphenoloxidase
Enzymatic system whose function is to oxidize mono-
and polyphenols. These are the cause behind the
enzymatic darkening seen in a number of vegetable
products.
Polisaccharide
Compound comprised of long chains of simple
sugars (monosaccharides).
Protein depolymerization/denaturation
Partial or complete development of the complex
structure of polypeptide chains* that leads to the loss
of specific protein functions.
R
Redox phenomena
Phenomena connected to oxidation-reduction reac-
tions of biological matrices or compounds. They are
catalyzed by specific enzymes and are effected
through the transfer of electrons from one substrate
to another.
Relative humidity
Amount of water present in the atmosphere calcu-
lated on the basis of the relationship between the
water present in a cubic metre of free air, and that
which should be contained in a cubic metre of air
saturated with vapour at a given temperature.
Rheology (rheologic properties)
Studies the motion and deformation of natural
bodies with special emphasis on fluids without
consistency and include, as extreme cases, purely
viscous (newtonian) fluids and elastic solids. There-
fore, the unique characteristic of rheology is the
study of the behaviour of substances that are both
elastic and viscous.
S
Sanitization
Series of cleaning and disinfecting operations
performed periodically on equipment and the produc-
tion environment; also used in reference to tech-
niques utilized to prevent or combat the presence of
micro-organisms in the product.
Shelf-life
In reference to a food product, it means how long a
product can stay on the shelf. It is the length of time the
organoleptic, nutritional and hygienic characteristics of
a food are maintained unaltered. It refers to commercial
stability and is not the same as product deterioration.
Stabilization
Series of operations that allow a food to reach a
condition of equilibrium from a chemical, physical
and microbiological standpoint (sterilization, drying,
addition of preservatives-stabilizers, etc.).
Starch retrogradation
Physical phenomenon comprised of a return to the
innate, crystalline structure of a starch which had previ-
ously undergone gelatinization* during heating and
whose linear amylose chains tend to return to their
initial structure. Starch retrogradation may be hindered
by the use of chemical agents (texture agents) that
prevent amylose returning to its innate configuration by
inserting itself between the starch chains separated by
gelatinization. In pasta, this is a negative factor that
creates stickiness and problems during cooking.
Steric hindrance
Effect by which a chemical reaction is slowed or
hindered because of the presence in a reagent of
large-size groups that make it impossible for another
reagent molecule to approach.
Sulfide bridge
Bond between two sulphur atoms within a complex
molecule.
T
Texture
All those physical, mechanical and rheologic proper-
ties of a food product perceived by the sense organs.
V
Viscosity
Physical magnitude that describes the attrition within a
fluid, i.e. the tendency of a fluid layer in motion to pull
other, immediately-adjacent, layers along with it.
X
Xanthane
Polysaccharide of microbial origin comprised of glucose
chains; used as a texture agent in the food industry
because of its hydrocolloid* properties.
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