The optimum conditions for the formation of chickpea dhal protein film and the characteristics of the

films were studied. Optimum yield of protein films was obtained form chickpea dhal at bean: water

ratios of 1:5 to 1: 7 and in the pH range of 9.0 to 10. O. The chickpea protein films were darker

and more brittle than soybean protein films

Abdullah, Norlia

Mohamed, Suhaila

Universiti Putra Malaysia Institutional Repository

Pertanika 11(2), 327-331 (1988) •COMMUNICATION IIIFormation of Protein Film from Chickpea Dha)ABSTRACTThe optimum conditions for the formation of chickpea dhal protein film and the characteristics of thefilms were studied. Optimum yield of protein films was obtained form chickpea dhal at bean: waterratios of 1:5 to 1: 7 and in the pH range of 9.0 to 10. O. The chickpea protein films were darkerand more brittle than soybean protein films.ABSTRAKKeadaan optimum pembentukan selaput protein dan ciri-ciri selaput protein yang terbentuk daripadakacang kuda telah dikaji. Hasil selaput protein yang paling baik didapati daripada dhal kacang kudadengan nisbah kekacang dan air 1:5 hingga 1:7 dalam julat nilai pH antara 9.0 hingga 10. O.Selaputprotein kecang kuda lebih gelap dan rapuh daripada selaput protein kacang soya (fucuk).INTRODUCTIONThe production of protein mm from legumesnot only increases legume utilisation but alsoresults in a highly nutritious, versatile food. Themm can be used in soups, vegetable or meatdishes and as an edible wrapping mm. Proteinfl1rns have been made from soy milk, and soyprotein isolates (Watanabe et al., 1975), peanutmilk (Aboagye and Stanley, 1985), cotton seedmilk, skimmed milk, whey proteins, caseins(Wu and Bates, 1973), keratin (Okamoto, 1978;Anker, 1972), and winged bean milk (SolehaIshak, 1985). The mm formation is believedto be an endothermic polymerisation of heatdenatured protein, simultaneous with surfacedehydration (Wu and Bates, 1972).Chickpea ranks among the world's threemost important pulse crops with a total annualproduction of round 7 million tonnes of dryseed from an area of about 10 million hectares(Summerfield & Roberts, 1985). Chickpeashave the advantage of a higher fat content thanmost pulses, which not only gives a higher energyconcentration but imparts a smoother textureand makes very palatable products (Aykroyd,1982). The present work attempts to study theformation of protein films from chickpea dhal.MATERIALS AND MEmODSDried dehulled chickpea (dhal) wereobtained from the retail shops at Sri Serdang.The beans were hand sorted to remove foreignmaterial, weighed, washed and soaked in excesswater overnight. The beans were rinsed andblended in water for about 3 minutes. The amountof water used for extraction was varied to deter-mine the optimum bean-to-water ratio to providethe maximum mm yield. The slurry obtainedwas converted to a milk by fJJ.tration using anextractor and a hydraulic press.To study the best pH for optimum fl1rnformation, the milk was adjusted to the desiredpH value (using 1M NaOH), within the rangeof pH of 8.0 to 11.0, since no chickpea proteinfl1rn could form below pH 8.0.The protein fl1rn was formed by the irrever-sible insolubilisation of dhal milk during eva}»ration at 850 C from 600 rn1 milk in a shallowtray (24 cm x 14 cm x 5 cm). Films wereharvested at 20 minutes intervals by loosening thefl1rn from the edges of the tray and picking it upwith a slender glass rod. Film formation wascontinued until fl1rn could ·no longer form. Atthis moment 100 rn1 of distilled water was addedto the milk to reduce its viscosity and fJJ.rn for-SUHAILA MOHAMED AND ORLIA ABDULLAH62 3 4prOle-in film numbero pH 11.0 .. pH 10.0 ~pH 9.0 6.pH 8.0Figure 2: Yellowness of protein film madeformed at different pH values20.,.-------------------....,1918~ 17~16~ ISE 14;. 135 12c!II~ 10·987-l------r---.,...---==l----,.-----1Iis attributed to the enhanced protein unfoldingunder alkaline conditions and the changed surfacecharge distribution which affected the relativeattractions of proteins to the liquid surface, mani-fested by a decrease in surface tension. The filmsformed at high pH tended to be staighter with lessintramoleculer elasticity. At alkaline pH theextracted milk was more viscus, indicating thatthe protein molecules in solution were morelinear and less globular. Alkaline conditions mayalso cause protein peptidization and thus mayeffect alkali labile amino acids which decrease thebiological value of the protein. Thus, the generalcharacteristic of the protein mm was more favou-rable at higher pH, even though the product wasdarker in colour.The film brittleness may be explained bythe low protein and cysteine of chickpea com-pared to soybean. Hence the formation of lessintermolecular disulphide bonds and the lowerbreaking point (yield stress). The brittlenesscould also partly be due to the interference of astrong protein-protein interaction by the higheramount of carbohydrate that may have beenincorporated into the mm, since chickpea has amuch higher carbohydrate content than soybean.Wu and Bates (1973) reported that mmsformed from soya protein isolate (SPI) in the pre-sence of added lipid or carhohydrate are smootherand of a more evp.n texture than those formedfrom SPI alone, which tended to from crackedfilms. Their studies indicated that the presenceof secondary components is essential for goodftlms formation of improved quality, but thatpH 11.0 pH 10.0 pH 9.C). pH '.0Figure 1: Lightness of protein film."-.- --...::'or:;;mcd:.:.:;..-=di:;::"":.::..;.:'o;,;.H..:;'.',:;;...:...-.. -.,lO....A'..A$..AJAlA'40J9]I"J6)$,.)>-J------,---.....---;::...-..--.-T---~•ptOirin film numbnRESULTS AND DISCUSSIONChickpea dhal protein ftlm was darker in colourand more brittle than soybean protein mm. Thedarker colour could be due to the high lysineand carbohydrate content of chickpea whichprovides conditions favourable for non-enzymicbrowning (Maillard reaction) at the hightemperature and alkaline conditions for mmformation.The colour of chickpea protein becamedarker as the pH of the milk was increased abovethe neutral pH (Figs. 1, 2 and 3), indicated bythe decrease in L (Lightness) and b (Yellowness)values.Although alkaline pH favours more completeprotein extraction, it promotes the Maillardreaction between the free amino groups with thecarbohydrate present, to form brown nitrogenouspolymers and copolymers (melanoidins) (Lee,1977). The surface of the mm became lesswrinkled and smoother with increasing pH. Similarobservations were reported by Aboagye andStanley (1985) on peanut protein lipid mms. Thismation was continued. The mms were hung inair to dry at room temperature for 24 hours andthe colour and weight of each film was recorded.Colour was determined using the HunterTristimulus Colorimeter for L, a, and b values(lightness, redness and yellowness) using theyellow tile (L= 77.5, a= 3.5, b= 23.0) asstandard. The protein content of each mm wasdetermined using the micro Kjeldahl method(pearson, 1976). Values presented are the averagereadings of 6 different trials.328 PERTANIKA VOL. 11 NO.2, )988FORMATION OF PROTEIN FILM FROM CHICKPEA DHAL2bean to water ratio was decreased below 1:7.Bean to water ratios below 1:5 resulted in in-complete protein extraction from the dhal, whiletoo great a dilution hindered f11m formation. Dataon the protein yield in each f11m (Table 1) showsthat there is an increase in protein yield in thesecond ftlm with decreasing protein yield there-after.The protein f11m could form only in alkalinepH, and the optimum yield (g of film) wasobtained at pH 9.0 (Table 2), indicating theimportant role of electrostatic repulsion forchickpea protein denaturation. Between pH 8and pH 9, most of the alfa amino groups beginto lose their positive charges hence causing a slightchange in the net negative charge in the proteinmolecules. The intramolecular repulsion and hightemperature favours unfolding of the proteinmolecules and exposure of the hydrophobicside chains. In aqueous solutions, the hydrophobicside chains would either interact with each otherto form hydrophobic bonds or be pushed to theair/water interface. This phenomena together withthe evaporation of water at the surface, helpedproduce a high protein concentration at theair/water interface which promotes intermolecularinteraction of the unfolded protein, and thisresults in ftlm formation. Above pH 9.5, othercharged side chains such as the epsilon groupof lysine, the hydroxyl group of tyrosine andthe SH group of cysteine began to lose theircharges causing a drastic change in the net negativecharge on the protein molecule, which not onlyresulted in intramolecular r~ulsion but alsointermolecular repulsion, thus hindering mmformation. However the relative rates of thesereactions not only depend on the severity of the1.5+:=:::....---,----,...----,----.-----...formed at diff....nt pH values6-r-----------=--------....S.S2 3 4 5 6protein film numbela pH 11.0 + pH 10.0 O"pH 9.0 6 pH 8.0Figure 3: Redness of protein filmexcessive amounts of such components weredetrimental.Work by Okamoto (1978) showed thatthe soybean protein f11ms had greater tensilestrength when the f11ms were formed on a waterpermeable solid/liquid interface rather than agas/liquid interface. The water permeable solidswhich were successfully tested were cellophaneand acetyl cellulose. The same method can pro-bably be applied to improve and increase thetensile strength of chickpea protein f11ms. Theformation of chickpea protein f11ms in thepresence of solubilised wheat gluten or keratinmight also increase the strength of chickpeaprotein films, since gluten and keratin formedvery strong pliable f11ms on their own (Okamoto,1978).The protein film yield was maximum whenthe bean: water ratio was between 1:5 and 1:7(Table 1). Fig. 4 shows the protein content offilms made with different bean to water ratios,indicating a reduced protein content when the...~ 4.S.. 4l;C;. 3.S~ 3t'" 2.STABLE 1Effect of bean: water ratio on the protein content (g) of each chickpea protein fIlm~no. 1 2 3 4 5 6b:w1 : 5 1.77± .01 2.28±.02 1.7 ±O.oI l.21±.01 0.91±.01 0.38±.011 : 6 1.77±.02 2.27±.05 1.25± .03 1.0 ±.04 0.5 ±.03 0.07±.011 : 7 l.55± .01 1.82±.04 1.16± .04 1.0 ±.02 1.63±.01 l.20±.011 : 8 o.71±.OI 0.99±.01 0.49± .01 0.36±.01 0.21±.01PERTANlKA VOL. 11 NO.2, 1988 329there was a slower rate of film formation at pH10 and 11, without a significant increase in thetotal yield,Table 3 shows the protein content of thefUms formed at different pH values, The fIlmsformed at pH 8,0 had the highest protein contentprobably because it had the least moisturecontent. Proteins at pH 8.0 had the least netcharge compared to proteins at pH 9;0, 10.0 or11.0, and therefore will be able to hold the leastamount of moisture compared to the others. Filmsformed at pH 11.0 also had a relatively highprotein content, probably because at that pH theincorporation of starch into the fUm was minimal.Although protein fIlms consists mainly of proteinmembranes, lipids and carbohydrate incorporatedSUHAILA MOHAMED AND NORLIA ABDULLAHof different bean: water ratio74-.==:;;;::::=::e::::::~~~=':"'=:::::"":::::::"_----'7372'11 ....... -:70(fl68_ &7~rsc 64~ 63g 62v 61.~ 60<5 59a 585756555453..J.1---"'!"2----:.3----;4---t---~6prolein film numbero bow 1:5 ... b:w 1:6 Qb:w 1:7 Ab:w 1:8Figure 4: Protein content in chickpea filmsconditions but also on the type of protein undertreatment, and results which are severe for oneprotein may not be for another. For chickpea,TABLE 2Yield of protein film (g) at different pHTime of harvest (mins) Total wt. % yieldpH g g/100 g20 40 60 80 100 120 beans11.0 19 2.1 2.1 1.6 0.6 0.2 8.5 10.0(1.9) (4.0) (6.1) (7.7) (8.3) (8.5)10.0 1.9 2.4 1.7 1.2 0.9 8.1 9.5(1.9) (4.3) (6.0) (7.2) (8.0)9.0 2.5 2.3 1.9 1.3 8.0 9.4(2.5) (4.8) (6.7) (8.0)8.0 1.8 1.8 1.1 0.8 5.5 6.4(1.8) (3.6) (4.7) (5.5)(Values in brackets are the total yield at any given time).TABLE 3Effect of pH on the protein content (g) of each chickpea protein filmFilm No.pH 2 3 4 5 68 72.2 71.9 71.7 69.3(1.3) (2.59) (3.38) (3.93)9 68.3 67.2 66.7 60.9(1.71) (3.26) (4.53) (5.32)10 68.9 67.9 67.0 66.5 61(1.31) (2.94) (4.08) (4.88) (5.43)11 70.7 71.6 68.9 66.1 66.1 63.6(1.34) (2.84) (4.29) (5.35) (5.75) (5.88)(Values in brackets are the total protein yield at any given time).330 PERTANIKA VOL. 11 NO.2, 1988FORMATION OF PROTEIN FILM FROM CHICKPEA DHALTABLE 4Composition of chickpea compared to soybean (g/100 g seed) (Aykroyd, 1982)Legume H2O Protein Fat Sugar Starch CHO* Fibre M C T W VChickpea 9.9 20.6*** 5.6 10.0 40.0 50.0 15.0 80 90 240 50 240Soyabean 7.0 36.8** 23.5 11.2 12.3 23.5 11.9 80 100 240 80 30CHO*= Total carbohydrate; ** N x 5.71 ***N x 6.25;Fibre = Total Fibre; M methionine; C cysteine;T threonine, W = tryptophan; V = valine;into it during ftlm formation contribute signi-ficantly to the flavour and physical properties ofthe film (Watanabe etal., 1975).The total weight of protein film whichcan be obtained from 100 g soybean was between22 g to 31 g. This is about 2 to 3 times higher thanthat obtained from the same weight of chickpea(Table 2). The reason for the lower yield ofprotein film from chickpea is the lower proteincontent of chickpea (about 20%) compared toprotein content of soybean (about 40%) and thepossible interference of protein film formationby the high carbohydrate content in chickpea(Table 4).Further work on determination of thecharacteristics of the chickpea protein film needto be done before its commercial potential canbe assessed. The characteristics include sensoryevaluation (acceptability); permeability tomoisture or oxygen for use as edible barrier;_and the possibility of forming other shapes egocylinders (for sausage casings) using cellophaneor acetyl cellulose as the water permeable solidiliquid interface mould, while helping to increasethe tensile strength of the ftlm.ACKNOWLEDGEMENTThe authors thank UPM for fmancing the research,Norhayati Salamudin for the typing and othermembers in the Faculty for their cooperation.SUHAILA MOHAMEDNORLIA ABDULLAHDepartment ofFood ScienceFaculty ofFood Science &Biotechnology43400 Serdang, Selangor, Malaysia.REFERENCESABOAGYE Y. and D.Y. STANLEY (1985): Texturisationof peanut protein by surface fIlm formationI & II. Canada Inst. Food Sci. Technol. J. 19(1)12-28.ANKER C.A. (1972): Keratin food coatings; UnitedStates Patent J.642-698.AYKROYD, W.R. (1982): In Aykroyd W.R., DoughtyJ. and Walker A. (eds). Legumes in HumanNutrition. Paper No. 20, Rome FAOLEE F.A. (1977). Basic Food Ozemistry 2nd edn. TheAVI publishing Co. Inc. Westport, Connecticut.OKAMOTO S., (1978): FactoIS affecting film formation.Cereal Food World. 23(5), p 256-262.PEARSON D. (1976). The Chemical Analysis of Food.7th ed. Churchill Livingstone, p. 11.SOLEHA ISHAK (1985). Formation of protein lipidf'ilm from winged bean. Ph. D. Thesis, UniversitiKebangsaan Malaysia.SUMMERFIELD, R.J. and E.H. ROBERTS, (1985):In Halevy, A.H. (ed.) A Handbook of flowering,Florida: CRC press.WATANABE K., T. WATANABE and S. OKAMOTO(1975). On the contribution of lipid to the pr()operties of yuba f'ilm. J. of lap. Soc. of Food Sci.and Technol., 22: '143.WU L.C. and BATES R.P. (1972): Soy protein lipidf'ilms 1. Studies on the f'ilms formation phen()omenon. J. Food Sci. . 37: 36.WU L.C. and R.P. BATES (1973): Influence ofingredients upon edible protein lipid from f'ilmcharacteristics. J. Food Sci., 38: 783-787.(Received 29 September, 1987)PERTANlKA VOL. 11 NO.2, 1988 331

Formation of Protein Film from Chickpea Dha)

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Formation of Protein Film from Chickpea Dha)

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