Physicochemical, Thermal, Morphological and Pasting Properties of Starches from some Indian Black...

Narpinder Singha

Maninder Kaura

Kawaljit Singh Sandhua

Harmeet Singh Gurayab

a Department of Food Scienceand Technology,Guru Nanak Dev University,Amritsar, India

b USDA ARS Southern RegionalResearch Center,New Orleans, LA, USA

Physicochemical, Thermal, Morphological andPasting Properties of Starches from some IndianBlack Gram (Phaseolus mungo L.) Cultivars*

The starches separated from thirteen different black gram cultivars were investigatedfor physicochemical, thermal, morphological and pasting properties. Amylose content,swelling power, solubility and water binding capacity of starches ranged between30.2–34.6%, 16.0–22.3 g/g, 14.8–17.3% and 73.5–84.5%, respectively. The diameterof starch granules, measured using a laser-light scattering particle-size analyzer, variedfrom 12.8 to 14.3 mm in all black gram starches. The shape of starch granules variedfrom oval to elliptical. The transition temperatures (To, Tp and Tc) and enthalpy of gela-tinization (DHgel) determined using differential scanning calorimetry, ranged between66.1–71.3, 71.0–76.2, 75.9–80.47C and 6.7–9.4 J/g, respectively. Pasting properties ofstarches measured using the Rapid Visco Analyser (RVA) also differed significantly.Pasting temperature, peak viscosity, trough, breakdown, final viscosity and setbackwere between 75.8–80.37C, 422–514, 180–311, 134–212, 400–439 and 102–151 RapidVisco Units (RVU), respectively. Turbidity values of gelatinized starch pastes increasedduring refrigerated storage. The relationships between different properties were alsodetermined using Pearson correlation coefficients. Amylose content showed a positivecorrelation with swelling power, turbidity and granule diameter. Swelling powershowed a negative correlation with solubility and setback. To, Tp and Tc showed posi-tive correlation with turbidity, pasting temperature and were negatively correlated topeak and breakdown viscosity.

Keywords: Black gram starch; Differential scanning calorimeter; Rapid Visco Analyser;Amylose; Granule size

1 Introduction

Legume seeds are the most important source of proteinand calories for large segments of the population mainlyin underdeveloped countries [1]. India is the largest pro-ducer of legumes in the world (136106 t), the total worldproduction being 546106 t [2]. Starch, the principal car-bohydrate constituent of a majority of plant materials,merits a detailed investigation to understand better itsbiochemical and functional characteristics as well as var-iations [3]. Hoover and Sosulski [4] reported that starch(when present) is the most abundant carbohydrate in thelegume seed (22–45%). Starch is a very versatile rawmaterial with a wide field of applications. The growingdemand of starches for the modern food industry hascreated interest for new sources of this polysaccharide[5]. Applications of starch in food systems are primarilygoverned by gelatinization, gelation, pasting, solubility,swelling and digestibility properties [6].

Starch from legumes has been reported to be more vis-cous than that from cereals indicating high resistance toswelling and rupture [7]. Schoch and Maywald [8] report-ed that the separation of pure starch from certain legumeswas difficult because of the presence of a highly hydratedfine fiber fraction and insoluble protein. The fine fiberspresumably come from the cell walls enclosing the starchgranules. Various workers [7, 9–12] have studied the sizeand characteristics of legume starch granule. Mostlegume starches exhibit a ‘C’-type diffraction pattern,which is intermediate between the A-type (cereal) and theB-type (tuber). Legume starches, such as those from pea,have been found to contain both A- and B-type crystal-lites [13]. Bogracheva et al. [14] and Buleon et al. [15]reported that all granules from wild pea starches containboth A- and B- polymorphs and that the B-polymorphsare arranged centrally with the A-polymorph located per-ipherally within the granules.

Correspondence: Narpinder Singh, Department of FoodScience and Technology, Guru Nanak Dev University, Amritsar-143005, India. e-mail: [email protected].

Starch/Stärke 56 (2004) 535–544 535

* The mention of firm names or trade products does not implythat they are endorsed or recommended by the U.S. Depart-ment of Agriculture over other firms or similar products notmentioned

2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.starch-journal.de

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DOI 10.1002/star.200400290

536 N. Singh et al. Starch/Stärke 56 (2004) 535–544

Black gram is an important legume crop throughout alarge part of the tropics. It contains on average 10.9%moisture, 24% protein, 1.4% fat, 0.9% fiber and 59.6%carbohydrate as main component [16]. Srinivasa Rao [17]has reported the starch content of black gram to be47.9% with amylose content of 43.8% (starch wt basis).The variations in starch composition and properties be-tween black gram cultivars have not been the subject of adetailed study. Difference in starch physicochemicalproperties between cultivars will affect the functionalproperties of starch and its suitability for specific end use[18]. Therefore the present investigation was undertakento examine the physicochemical, morphological, thermaland pasting properties of starches from various blackgram cultivars.

2 Materials and Methods

2.1 Materials

Representative samples of 13 improved black gram cul-tivars viz. UG-414, UG-218, UG-909, UG-1017, UG-1093,UG-841, UG-916, UG-902, UG-562, UG-920, UG-1008,UL-338 and KU-3 from 2002 harvest were obtained fromthe Regional Research Center, Gurdaspur, Punjab, India.All the samples were grown in a single environment andcome from the same part of the state.

2.2 Starch isolation

Starch isolation was carried out using the procedure out-lined in our earlier publication [6]. Seeds of black gram(300 g) were steeped in water containing 0.16% sodiumhydrogensulfite for 12 h at 507C. The steep water wasdrained off, and grains were ground in a laboratory blen-der. The ground slurry was screened through nylon cloth(100 mesh). The filtrate slurry was allowed to stand for 1 h.The supernatant was removed by suction and the settledstarch layer was resuspended in distilled water and cen-trifuged in wide-mouthed cups at 28006g for 5 min. Theupper non-white layer was scraped off. Starch was thencollected and dried in an oven at 407C for 12 h. All furthertests were done in three replicates.

2.3 Chemical analysis

Starch samples were estimated for their moisture, ash,fat, and protein content according to the AOAC officialprocedures (methods 925.09, 923.03, 920.39, 954.01,respectively) [19]. Amylose content was determined usingthe method of Williams et al. [20].

2.4 Physicochemical properties

Swelling and solubility determinations were carried out at907C using the method of Leach et al. [21]. A 1% aque-ous suspension of starch (100 mL) was heated in a waterbath at 907C for 1 h with constant stirring. The suspen-sion was cooled for half an hour at 307C. Samples werethen poured into preweighed centrifuge tubes, cen-trifuged at 30006g for 10 min and weight of sedimentsdetermined. For the measurement of solubility, thesupernatants were poured into aluminum dishes andevaporated at 1107C for 12 h and weight of dry solidswas determined.

Water binding capacity (WBC) was determined using themethod described by Yamazaki [22] as modified by Med-calf and Gilles [23]. A suspension of 5 g starch (dry weight)in 75 mL distilled water was agitated for 1 h and cen-trifuged (3,0006g) for 10 min. The free water wasremoved from the wet starch, the wet starch drained for10 min and weighed.

Turbidity was determined using the method described byPerera and Hoover [24]. A 1% aqueous suspension ofstarch was heated in a water bath at 907C for 1 h withconstant stirring. The suspension was cooled for 1 h at307C. The samples were stored for five days at 47C in arefrigerator and turbidity was determined every 24 h bymeasuring absorbance at 640 nm against a water blankwith a Shimadzu UV-1601 spectrophotometer (ShimadzuCorporation, Kyoto, Japan).

For the measurement of syneresis, a starch suspension(2%, w/v) was heated at 857C for 30 min in a temperaturecontrolled water bath, followed by rapid cooling in an ice-water bath to room temperature. The starch sampleswere stored for 24, 48 and 120 h at 47C. Syneresis wasmeasured as the percentage of water released after cen-trifugation at 3,2006g for 15 min.

2.5 Thermal properties

Thermal characteristics were studied by using the differ-ential scanning calorimeter-821e (Mettler Toledo, Grei-fensee, Switzerland) equipped with a thermal analysisdata station. Starch (3.5 mg, dry weight) was loaded into a40 mL capacity aluminum pan (Mettler, ME-27331) anddistilled water was added with the help of a Hamiltonmicrosyringe to achieve a starch-water suspension con-taining 70% water. Samples were hermetically sealed,allowed to stand for 1 h at room temperature andreweighed before heating in the DSC. The DSC analyzerwas calibrated using indium, and an empty aluminum panwas used as reference. Sample pans were heated at arate of 107C/min from 20 to 1007C. Onset (To), peak (Tp),


Starch/Stärke 56 (2004) 535–544 Starch properties of Indian Black Gram (Phaseolus mungo L.) 537

conclusion temperature (Tc) and enthalpy of gelatinization(DHgel) were calculated automatically. The gelatinizationtemperature range (R) was computed as (Tc–To) asdescribed by Vasanthan and Bhatty [25]. Enthalpies werecalculated on a dry starch basis. The peak height index(PHI) was calculated as the ratio DHgel/(Tp–To) as describ-ed by Krueger et al. [26].

2.6 Granule morphology

Scanning electron micrographs of isolated starches weretaken by a JEOL JSM-6100 scanning electron micro-scope (JEOL Ltd, Tokyo, Japan). Samples were sus-pended in ethanol to obtain a 1% suspension. One dropof the starch/ethanol solution was applied on an alumi-num stub using double-sided adhesive tape and thestarch was coated with gold/palladium (60:40). Anaccelerating potential of 5 kV was used during micro-scopy. Starch granule diameter was determined usingCoulter small volume module model LS 230 laser lightscattering particle size analyzer. Starch (0.25 g) wascombined with 3 mL of distilled water in a small glass vialand vortexed followed by sonication for 1 h. The driedsample was completely deagglomerated after approxi-mately 10 min of sonication at 407C. The sample wasvortexed and approximately ten drops were added intothe sample port until the instrument read 45% PIDS(Polarization Intensity Differential Scattering) or 10–14%obscuration. Isopropanol was used as the suspensionfluid within the instrument. The sample was allowed toequilibrate the isopropanol for 15 min before starting theanalysis.

2.7 Pasting properties

Pasting properties were studied using the Rapid ViscoAnalyser (Newport Scientific Pty Ltd, Warriewood NSW2102, Australia). Starch was sonicated in water for 1 hbefore being loaded in the RVA. This was done to deag-glomerate the starch granules, which were adhering toeach other. Viscosity profiles were recorded using starchsuspensions (6%, w/w; 25 g total weight). The tempera-ture-time conditions included a heating step from 50 to957C at 67C/min (after an equilibration time of 1 min at507C), a holding phase at 957C for 1.5 min, a cooling stepfrom 95 to 507C at 6 7C/min and a holding phase at 507Cfor 2 min.

2.8 Statistical analysis

The data reported in all tables were subjected to one-wayanalysis of variance (ANOVA). Pearson correlation coeffi-cients (r) for the relationships between all properties werealso calculated using Minitab Statistical Software version13 (Minitab Inc, State College, PA, USA).

3 Results and Discussion

3.1 Chemical composition

The isolated starches were characterized by low lipid(0.08–0.14%) and protein contents (0.62–0.94%). The ashcontent, reflecting contamination by fine fiber, rangedbetween 0.17–0.26% (Tab. 1). The yield of starch from

Tab. 1. Chemical composition and functional properties of black gram starchesa, b.

Black gramcultivars

Ash[%]

Fat[%]

Protein[%]

Amylosecontent [%]

Swellingpower [g/g]

Solubility[%]

Water bindingcapacity [%]

UG-414 0.18 6 0.02a 0.08 6 0.01a 0.86 6 0.04bc 32.6 6 0.4ab 19.7 6 1.5b 15.1 6 0.9a 77.3 6 2.1bUG-218 0.24 6 0.03ab 0.09 6 0.01a 0.93 6 0.03c 31.1 6 0.4ab 20.3 6 1.4bc 15.9 6 0.8ab 76.6 6 1.9abUG-909 0.23 6 0.03 ab 0.13 6 0.03b 0.92 6 0.06c 32.8 6 0.5ab 20.3 6 1.2bc 15.5 6 1.0ab 74.2 6 2.0aUG-1017 0.26 6 0.04b 0.12 6 0.03ab 0.87 6 0.05bc 31.1 6 0.4ab 20.0 6 1.3bc 15.3 6 1.1a 76.6 6 1.6abUG-1093 0.18 6 0.02a 0.13 6 0.01 b 0.86 6 0.04bc 32.9 6 0.3ab 20.6 6 1.3bc 15.6 6 1.1ab 82.4 6 2.1cUG-841 0.22 6 0.04ab 0.08 6 0.02a 0.89 6 0.06bc 31.7 6 0.5ab 20.5 6 1.0bc 15.7 6 1.2ab 76.0 6 1.4abUG-916 0.21 6 0.02ab 0.09 6 0.02ab 0.94 6 0.07c 34.6 6 0.3b 22.3 6 1.4c 14.8 6 1.08a 78.4 6 2.2bUG-902 0.19 6 0.02ab 0.14 6 0.03 b 0.91 6 0.06bc 33.4 6 0.3b 20.7 6 1.2bc 15.6 6 1.1ab 78.5 6 1.2bUG-562 0.25 6 0.03b 0.12 6 0.04ab 0.69 6 0.03ab 30.2 6 0.4a 20.1 6 1.3bc 16.5 6 0.9ab 76.1 6 1.9abUG-920 0.23 6 0.01ab 0.10 6 0.01ab 0.74 6 0.07b 32.5 6 0.4ab 19.3 6 1.2b 16.4 6 0.6ab 74.0 6 1.8aUG-1008 0.26 6 0.04b 0.11 6 0.01 ab 0.71 6 0.06ab 33.0 6 0.3ab 19.8 6 1.1b 17.3 6 0.9b 84.5 6 1.7cUL-338 0.19 6 0.02ab 0.09 6 0.02a 0.69 6 0.05ab 30.7 6 0.4a 16.0 6 1.2a 17.1 6 0.8b 76.3 6 1.6abKU-3 0.17 6 0.01a 0.08 6 0.03a 0.62 6 0.05a 32.0 6 0.3ab 20.2 6 1.2bc 15.4 6 0.9a 73.5 6 1.8a

a Values followed by the same letter within a column do not differ significantly (P,0.05).b Mean (6 = standard error) of triplicate analyses.



black gram cultivars was lowest for UG-562 (19%) andhighest for KU-3 cultivar (25%), which was within therange (18–45%) reported for most legume starches [1, 3,27–28]. Starch yield of 47.9 and 45% from black gram hasbeen reported earlier [17, 29]. Schoch and Maywald [8]reported starch yields of 27, 38 and 37% from navy bean,lentil and mung bean seeds, respectively.

Amylose content of black gram starches is presented inTab. 1. Highest amylose content was observed for UG-916 (34.6%) and lowest for UG-562 (30.2%) starch. Theresults corroborated well with those reported earlier byother investigators for legume starches. Non-mutantlegume starches have been reported to be characterizedby a higher amylose content than cereal starches, often inthe range of 30–40%, for example 30% in chickpea [7],31–32% in faba bean [7, 30], 34% in pea [30] and 38% inlentil [30]. Sathe et al. [29] reported an amylose content of26.65% in black gram starch.

3.2 Physicochemical properties

Swelling power and solubility provide evidence of thestrength of interaction between starch chains within theamorphous and crystalline domains [31]. Black gramstarches showed swelling power and solubility between16.0–22.3 g/g and 14.8–17.3%, respectively (Tab. 1). Anegative correlation of swelling power with solubility (r =20.664) was observed. Hoover and Sosulski [4] reportedswelling power and solubility in the range of 11–26 g/g

and 8–25%, respectively, for legume starches at 907C.Schoch and Maywald [8] reported swelling powers in therange of 16–20 g/g for yellow pea, navy bean, lentil, andgarbanzo bean starches. Swelling power of starch isaffected by the presence of lipids [32]. These may have noor little effect on swelling power in our study, as traces oflipid content in legume starches have been reported [33].It has been proposed that bonding forces within thegranules of starch affect the swelling power. Conse-quently, highly associated starch granules, with anextensive and strongly bonded micellar structure, shoulddisplay relatively greater resistance to swelling [21]. Apositive correlation of amylose content with swellingpower was observed (Tab. 4).

Water binding capacity was lowest for KU-3 (73.5%) andhighest for UG-1008 (84.5%) starch (Tab. 1). WBC of 90%in faba bean [30], 98% in lentil [30], 78.2% in mung bean[34] and 82% in field pea [30] starches has been reported.

The turbidity values of gelatinized starch suspensions aredepicted in Fig. 1. UG-920 starch paste showed lowestwhile UG-902 and UG-909 starch pastes showed highestturbidity values. Turbidity development in starches duringstorage has been attributed to various factors such asgranule swelling, granule remnants, leached amylose andamylopectin, amylose and amylopectin chain length,intra- or intermolecular bonding, lipid and cross-linkingsubstitution [35]. A positive correlation of amylose con-tent with turbidity was observed in the present study.Turbidity values of all starch suspensions increased dur-

Fig 1. Effect of storage duration on turbidity (absorbance at 640 nm) of black gram starches.



ing storage. Legume starches have been reported tocontain varying amounts of phosphate monoester sub-stituents, which may also have contributed to variation inpaste turbidity among different black gram starches [33].

The syneresis of gels prepared from starches was meas-ured as amount of water released from gels during stor-age (up to 120 h) at 47C (Fig. 2). UG-1008 starch had thehighest while UG-1017 starch showed the lowest syner-esis rate during the 120 h of storage at 47C. Highersyneresis levels of 11.3 mL/50 mL in adzuki bean starch[36] and 9.6 mL/50 mL in lima bean starch [5] for gelsformed at 47C with concentrations of 7%, as compared toblack gram starches has been reported. This may be at-tributed to the differences in starch concentration or cen-trifugal forces between starches. Lower syneresis sug-gests that interactions between starch chains during lowtemperature storage occurred slowly or were of muchlower order of magnitude. Starch gels are metastable andnon-equilibrium systems. Therefore, they undergo struc-tural changes during storage [37]. Syneresis of starchpastes increased with the increase in storage duration.Miles et al. [38] and Ring et al. [39] attributed the initial gelfirmness during gelation to the formation of an amylosematrix gel and the subsequent slow increase in gel firm-ness to amylopectin crystallization.

3.3 Thermal properties

Starch, when heated in the presence of excess water,undergoes an order to disorder phase-transition calledgelatinization over a temperature range characteristic of

the starch source [31]. The gelatinization temperatures(onset, To, peak, Tp and conclusion, Tc), enthalpies ofgelatinization (DHgel), peak height index (PHI) and gelati-nization range (Tc–To) for the starches investigated arepresented in Tab. 2. Significant differences (p,0.05) wereobserved in To, Tp and Tc among the starches. UG-562starch showed lowest To (66.17C) and Tp (71.07C) whileUG-909 starch had highest values of both. The conclu-sion temperature (Tc) was observed to be highest for UG-414 (80.47C) and lowest for UG-1017 (75.97C) starch.DHgel was observed to be highest (9.4 J/g) for KU-3starch, whereas UG-414 starch showed the lowest (6.7 J/g). DHgel reflected the loss of double helical rather thancrystalline order [40]. The high DHgel of a starch suggeststhat the double helices (formed by the outer branches ofadjacent amylopectin chains) that unravel and melt duringgelatinization are strongly associated within the nativegranule [41]. The difference in To, Tp, Tc and DHgel in blackgram starches may be attributed to the differences in theiramylose content and granular structure. Noda et al. [42]postulated that a low To, Tp, Tc and DHgel reflect the pres-ence of abundant short amylopectin chains in a starch.Gelatinization temperature range (R) was found to belowest for UG-902 (6.9) and highest for KU-3 (10.3). A highrange suggests the presence of crystallites of varyingstability within the crystalline domains of the granule of aparticular starch [41]. PHI is the ratio of DHgel for gelatini-zation to the gelatinization temperature range and is ameasure of uniformity in gelatinization. PHI was found tobe lowest for UG-920 (1.4), whereas UG-218 starchshowed highest PHI (2.4). An interrelation among DSCparameters was also observed. To was positively corre-

Fig 2. Effect of storage duration on syneresis (%) of black gram starches.



Tab. 2. Gelatinization parameters of black gram starchesa, b.

Black gramcultivars

To[7C] Tp[7C] Tc[7C] DHgel [J/g] PHI R

UG-414 70.9 6 0.3c 75.5 6 0.6bc 80.4 6 0.5c 6.7 6 0.2a 1.5 6 0.14a 9.5 6 0.5abUG-218 69.2 6 0.4b 72.9 6 0.8ab 78.1 6 0.7b 8.8 6 0.5ab 2.4 6 0.13b 9.0 6 0.5abUG-909 71.3 6 0.5c 76.2 6 0.6c 80.2 6 0.9c 7.1 6 0.3ab 1.4 6 0.14a 9.0 6 0.4abUG-1017 67.1 6 0.5ab 71.9 6 0.5ab 75.9 6 0.9a 7.5 6 0.2ab 1.7 6 0.15ab 8.8 6 0.6abUG-1093 67.4 6 0.7ab 72.4 6 0.4ab 77.1 6 0.8ab 8.2 6 0.2ab 1.6 6 0.2ab 9.7 6 0.4abUG-841 69.3 6 0.6b 73.3 6 0.3ab 78.6 6 0.2bc 9.2 6 0.4b 2.3 6 0.13b 9.3 6 0.3abUG-916 70.1 6 0.8b 74.1 6 0.5b 79.1 6 0.4bc 8.3 6 0.3ab 2.1 6 0.12b 9.0 6 0.4abUG-902 71.1 6 0.5c 74.5 6 0.5b 78.0 6 0.6b 7.7 6 0.3ab 2.3 6 0.10b 6.9 6 0.2aUG-562 66.1 6 0.4a 71.0 6 0.8a 76.0 6 0.5a 8.3 6 0.3ab 1.7 6 0.15ab 9.9 6 0.5bUG-920 67.1 6 0.2ab 72.2 6 0.8ab 76.8 6 0.4ab 7.0 6 0.5a 1.4 6 0.2a 9.7 6 0.3abUG-1008 68.1 6 0.3ab 72.7 6 0.7ab 77.7 6 0.3ab 8.8 6 0.4ab 1.9 6 0.15ab 9.6 6 0.2abUL-338 69.9 6 0.4b 74.5 6 0.6b 79.2 6 0.2bc 7.7 6 0.5ab 1.7 6 0.3ab 9.2 6 0.3abKU-3 67.6 6 0.5ab 72.6 6 0.6ab 77.9 6 0.8b 9.4 6 0.5b 1.9 6 0.1ab 10.3 6 0.2b

To = onset temperature, Tp = peak temperature, Tc = conclusion temperature, R = gelatinization range(Tc–To); DHgel = Enthalpy of gelatinization (dwb, based on starch weight), PHI = peak height indexDHgel/(Tp–To).a Values followed by the same letter within a column do not differ significantly (P,0.05).b Mean (6 = standard error) of triplicate analyses.

lated to Tp, Tc and negatively correlated to range (Tab. 4).DHgel was positively correlated to PHI. Among the transi-tion temperatures, Tp showed significant correlation withDHgel, however, at a higher P-value (P,0.05).

3.4 Granule diameter and microscopicappearance

The range in granule diameter of isolated starches isshown in Fig. 3 and their shape is illustrated in Fig. 4.Black gram starch granules were morphologically similarto other legume starch granules [4, 34]. The shape ofstarch granules was variable, ranging from oval to ellip-tical. Legume starches have been reported to have gran-ule sizes in the range of 18–23 mm [29]. Black gram star-ches are relatively small as compared to other legumestarches; with characteristic granule diameter in therange between 12.8–14.3 mm. Scanning electron micro-scopic observations indicated the surface of the gramstarch granules to be smooth with no evidence of scars asreported by Sathe et al. [29] for black gram starches.

3.5 Pasting properties

Changes in the viscosity of starch suspensions as theresult of temperature changes were measured with RVA.The results of Rapid Visco Analysis are summarized inTab. 3. Black gram starch behaved like a non-waxy typeof starch with a high setback. Pasting temperature (tem-

perature at the onset of rise in viscosity) ranged between75.8–80.37C. Pasting temperatures of 667C for faba beanand 717C for mung bean starch has been reported byNaivikul and D’Appolonia [34]. Lineback and Ke [7]observed pasting temperatures of 68.57C for chickpeaand 677C for horse bean starch. The high pasting tem-perature for black gram starches indicated their higherresistance towards swelling. All the starch samplesshowed gradual increase in viscosity with the increase intemperature. Granule swelling is accompanied by leach-ing of granular constituents, predominantly amylose, intothe external matrix resulting in a dispersion of swollengranules in a continuous matrix [21, 43]. Peak viscosity ofstarches ranged from 422 to 514 RVU, whereas break-down viscosity (measure of the susceptibility of cookedstarch to disintegration) ranged between 134–212 RVU.Final viscosity (indicates the ability of starch to form aviscous paste) and setback viscosity (measure of syner-esis of starch upon cooling of cooked starch pastes)ranged between 400–439 and 102–151 RVU, respectively.The isolated starches were characterized with stable hotpaste viscosities and high setback values. Interrelation-ship of pasting properties with other parameters wasobserved. Pasting temperature was positively correlatedwith To, Tp (Fig. 5a) and Tc and negatively correlated withpeak viscosity, breakdown viscosity, DHgel and range (Fig.5b). Peak viscosity was negatively correlated to To, Tp, Tc

(Fig. 5c) and positively correlated to breakdown viscosityand granule diameter. Breakdown viscosity was nega-tively correlated to transition temperatures (P,0.01), final



Fig 3. Granule diameter (mm) of black gram starches.

Tab. 3. Pasting properties of black gram starchesa, b.

Black gramcultivars

Pasting tem-perature [7C]

Peak viscosity[RVU]

Trough viscosity[RVU]

Breakdownviscosity [RVU]

Final viscosity[RVU]

Setback[RVU]

UG-414 79.5 6 0.07bc 450 6 7.30bc 293 6 1.00b 156 6 4.31b 424 6 0.77ab 130 6 1.24bcUG-218 77.9 6 0.02ab 445 6 3.77b 280 6 0.88b 165 6 4.66bc 407 6 4.97ab 127 6 5.85bUG-909 80.3 6 0.04c 449 6 5.03bc 300 6 6.13bc 149 6 5.89ab 425 6 5.25ab 124 6 4.38bUG-1017 76.8 6 0.01ab 494 6 8.16c 304 6 2.76bc 183 6 3.73c 431 6 6.03ab 125 6 3.84bUG-1093 76.7 6 0.04ab 494 6 5.54c 311 6 0.35c 182 6 5.19c 418 6 9.72ab 106 6 2.37aUG-841 78.5 6 0.07b 466 6 7.13bc 304 6 6.01bc 161 6 6.13bc 412 6 2.06ab 108 6 3.95abUG-916 78.7 6 0.16b 459 6 0.71bc 300 6 1.77bc 157 6 3.18b 439 6 2.47b 134 6 6.36bcUG-902 79.6 6 0.02bc 475 6 1.71bc 308 6 1.41c 167 6 3.13bc 414 6 5.71ab 105 6 7.13aUG-562 75.8 6 0.25a 514 6 8.03d 310 6 4.24c 212 6 5.80d 407 6 2.77ab 106 6 1.47aUG-920 77.4 6 0.11ab 494 6 7.26c 180 6 6.89a 184 6 5.37c 432 6 5.37ab 122 6 1.53abUG-1008 77.4 6 0.03ab 498 6 6.96cd 305 6 1.12bc 193 6 8.84cd 424 6 8.49ab 119 6 3.37abUL-338 79.3 6 0.14bc 422 6 5.43a 287 6 4.19b 134 6 7.25a 439 6 4.18b 151 6 0.23cKU-3 76.3 6 0.02ab 497 6 0.41cd 298 6 0.06bc 199 6 0.41cd 400 6 2.59a 102 6 0.59a

a Values followed by the same letter within a column do not differ significantly (P,0.05).b Mean (6 = standard error) of triplicate analyses.

Tab. 4. Pearson correlation coefficient between different physicochemical, thermal, morphological and pasting propertiesof black gram starches.

Swellingpower

Amylose Pastingtempera-ture

Peakviscosity

Break-downviscosity

Finalviscosity

Set-back

To Tp DHgel

Amylose 0.449*Breakdown viscosity 0.289 0.183 20.884** 0.951**Final viscosity 20.281 20.249 0.393 20.358 20.508*Setback 20.516* 20.466* 0.488* 20.732** 20.698** 0.777**Granule diameter 0.408 0.624** 20.093 0.498* 0.411 20.443*To 0.006 0.207 0.961** 20.794** 20.835** 0.232 0.391Tp 20.097 0.187 0.949** 20.768** 20.822** 0.320 0.445* 0.951**Tc 20.093 0.055 0.847** 20.801** 20.784** 0.210 0.450* 0.882** 0.927**DHgel 0.253 20.182 20.471* 0.240 0.357 20.568** 20.432* 20.320 20.464*PHI 0.360 0.009 0.047 20.134 20.074 20.401 20.236 0.203 20.086 0.695**

*P, 0.05. **P, 0.01.



Fig 4. Scanning electron micrographs of black gramstarches A, UL-338; B, UG-218, C, KU-3, D, UG-414.

Fig 5a. Relationship between pasting temperature and Tp

of black gram starches.

Fig 5b. Relationship between pasting temperature andgelatinization temperature range of black gram starches.

Fig 5c. Relationship between peak viscosity and Tc ofblack gram starches.

viscosity (P,0.01) and setback (P,0.01). Final viscositywas negatively correlated to DHgel and granule diameter.Setback was positively correlated to final viscosity, Tp andTc. A negative correlation of setback with DHgel and gran-ule diameter (Fig. 5d) was observed.

Fig 5d. Relationship between setback and granule di-ameter of black gram starches.

4 Conclusions

The isolated starches showed ash, protein, lipid andamylose contents ranging between 0.17–0.26%, 0.62–0.94%, 0.08–0.14%, and 30.2–34.6%, respectively. Theirswelling power and solubility at 907C was in the rangebetween 16.0–22.3 g/g and 14.8–17.3%, characteristic ofother legume starches. The starches showed granuleswith predominantly oval shapes, having granule diameterin the range of 12.8–14.3 mm. Several significant correla-tions of thermal properties with functional and pastingproperties were observed. These starches had a stabi-lized viscosity pattern possessing granules that resistswelling to yield a cooking viscosity pattern similar to



cross-bonded starches. The high setback values shownby these starches make them unsuitable for food appli-cations where low syneresis rate is required such as infrozen or refrigerated foods.

Acknowledgements

We are thankful to Dr. S. S. Pal, Regional Research Cen-ter, Gurdaspur, for providing us seeds of different blackgram varieties.

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(Received: February 26, 2004)(Revised: May 25, 2004)(Accepted: June 28, 2004)


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Physicochemical, Thermal, Morphological and Pasting Properties of Starches from some Indian Black...

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