Effects of protein variation on starch cystallinity and bread staling

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1 2011 Interntionl Conference on Food Engineering nd Biotechnology IPCBEE vol.9 (2011) (2011)IACSIT Press, Singpoore Effects of protein vrition on strch cystllinity nd red stling M. Slehifr 1 ABSTRACT. Three flours with proteins of 9.4, 11.6 nd 13.5% were prepred nd Flt reds were ked ccording to formultion. Whet strch crystllinity ws studied using differentil scnning clorimetery (DSC). The crystlliztion enthlpy, pek temperture (T p ) nd onset point tempertures (T o ) of the DSC thermogrms were nlyzed during storge in reds. Bred strips were sumitted to Krmer sher test, nd firming of reds were determined during storge. Results indicted tht high protein reds showed lower extent of retrogrdtion. Study showed tht low protein flours stled fster due to high concentrtion of strch nd low wter sorption. Keywords: Flt red, protein, strch crystllinity, stling 1. Introduction Strch is key fctor in the stling phenomenon. Ntive strch is present s semi crystlline grnules (Fergestd,2000). During the strch geltiniztion, the grnules swell nd lose their moleculr order. (Crce, 1996). During the king, the strch is geltinized, nd the semi crystlline structure chnged to morphous structure. During cooling nd storge of the red, the strch crystlline structure is recovered limitedly which cused significnt chnges in the mechnicl properties of the red. (Primo mrtin, 2007). Generlly the consumer cceptility of red depends in prt on its mechnicl properties such s firming nd stling. It ws suggested tht strch retrogrdtion, is lso implicted in stling (Mrtin 1991). Gluten nd its interctions with strch my hve role in the stling process (Armero 1998 nd Ro 1992). Studies showed tht the mechnism of stling, dels with the interctions etween strch grnules nd proteins nd it ws indicted tht stling rte cn y delyed y incresing the mount of DSC(Differentil Scnning Clorimetery) ws recently used to investigte the crystlliztion nd retrogrdtion of strch (Ad krim,2000). In this study the crystllinity of strch nd the stling, in reds which were produced y three different flours vried in protein contents, ws studied. 2. Mteril nd Methods 2.1. Chemicl Anlysis of flours Three flours with proteins of 9.4. (t 1 ), 11.6 (t 2 ) nd 13.5% (t 3 ) were prepred nd the protein, sh nd moisture content nd frinogrph test were determined ccording to AACC procedures 46-12,08-01, A, nd respectively (AACC, 2000) Bred king Flt reds were prepred t the king l using: whet flour, dry yest (0.4%), slt (1.5%) (Primo mrtin, 2007). Ingredients were lended for 1.5 min t low speed (150 rpm).wter ws dded nd mixed t medium speed ( rpm) for 6 min until finl dough prepred. The dough ws llowed to rest for 45 min 1 Acdemic memer of Islmic Azd University, Food Science nd Technology deprtment, shhriyr- shhre ghods rnch. Tel( ), Fx( ) Emil ddress: M_slehi1978@yhoo.com 300

2 nd ws then divided nd rounded nd rest gin for 12 min. Proofing ws performed t C nd 80% RH until fixed volume of gs ws produced. Breds were ked t 330 C for 75 sec, llowed to cool t mient temperture (25) C nd pcked in seled polyethylene films nd stored in 25 C Differentil Scnning Clorimetery (DSC) 30±5 mg of smples were weighted in hermeticlly seled luminum pn nd nlyzed. Smples were heted t C nd the rte of 5 C/min. The onset (T o ) nd pek (T p ) tempertures nd the trnsition enthlpy (J/g) of recrystlliztion were clculted (AACC 2000) Bred stling Bred strips (6 7.5 cm 2 ) were sumitted to Krmer sher test on n Instron universl Testing mchine ccording to AACC 74-09, lod cell: 500 N, extension rnge: 25 mm, test end point: 12 mm,test speed: 120 mm/minute nd mximum point in curves ws red nd firming of reds were determined in 1,3,5,7 dys of storge. (AACC., 2000) Sttisticl nlysis The significnce of ech tretments in smples ws nlyzed using nlysis of vrince (ANOVA), nd if ANOVA ws significnt, Tukey test were used. SPSS V.13 performed t 95% confidence level. 3. Results nd discussion Generl composition nlysis of whet flours showed in Tle 1. Ash content of flours hd no significnt differences nd vritions in moisture content ws just for different environment humidity conditions nd ws not ffect the flour specifictions, ut differences in protein content were detectle nd ffect flour chrcteristics. Tle 1. composition nlysis of flours. smple Chemicl Anlysis Moisture (%) Ash (%) Protein (%) t c The reltive recrystlliztion of strch in reds ws shown in Tle 2. The DSC thermogrms cquired in 1 dy storge nd 3 dys storge showed tht whet strch recrystlliztion enthlpy incresed during storge time which ws due to the retrogrdtion of strch. Fig 1 Shows the effect of storge on retrogrdtion, indicted the incresing in retrogrdtion during red stling (Riott, 2007). Tle2. Enthlpy vritions during storge. Smple Storge time Enthlphy (J/g) Bred 1 dy storge 3 dys storge During storge, crystls hve time to recovered nd regin their crystllinity. So y incresing the storge time, there could e much more recovered crystls which need high energy for melting. (Jocos., 1998). 301

3 Enthlphy (J/gr ) 0 t3 1 3 dys storg dy storge ge Fig 1. Effect of red storge on retrogrdtion. Tle 3 showed pek temperture nd onset point tempertures in B 2 nd B 3 reds. Tle 3. Pek nd onset point tempertures of reds during storge time. Bred 1 dy storge T p (c) 3 dys storge T o (c) T p (c) T o (c) Tp: pek temperture, T o : onset point Temperture All vlues were mens of three replictes. Typicl DSC thermogrms of strch-wter mixture showed three endothermic peks (Fukuok., 2002). The first pek (55-60C) corresponds to geltiniztion of strch crystllites. Second pek (out C) is the melting of remining crystllites nd the third pek (out l00c) hs een ttriuted to dissocition of mylse- lipid complex. Bred thermogrms, showed single pek t out l00c which ws due to dissocition of recovered crystls (recrystls). The sencee of first nd second pek nd presence of third pek t the tempertures out l00c indicted tht strch hd completely geltinized during king. DSC thermogrms of the flours showed geltiniztion pek t out C while DSC thermogrms of red showed the melting of remining crystlss (which hve higher melting tempertures nd could not e geltinized during king) or the melting of recrystlls (tht need the highest melting tempertures). Breds hd high pek nd onset point tempertures which showed tht due to the longer time of king, more strch grnules geltinized so during storge most crystls were recovered crystls which were stronger nd hd higher melting tempertures, reflecting in high pek nd onset point tempertures. The effect of protein on the extent of retrogrdtion ws studied y DSC. Tle 4. Tle 4. Enthlpy vritions in reds produced y flours of different protein contents during storge. Enthlpy (J/g) 1 dy storge 3 dys storge t t t * In ech column verges with the sme chrcters (,,..) hve no significnt differences t 5%level Tle 4 Shows the effect of red stling on enthlpy or retrogrdtion, indicted the ncresing in enthlpy during red stling (Riott, 2007). During storge, crystlss hve time to recovered nd regin their crystllinity. So y incresing the storge time, theree could e much more recovered crystls whichh need high energy for melting (Jcos., 1998). It ws found tht the recrystlliztion enthlpy of strch s mesured y DSC, decresed with incresing levels of protein (Elisson., 1995). This ws explined y the distriution of wter within the mixed system( see tle 5). 302

4 Tle 5. Frinogrph results. Wter sorption (%) Frinogrph prmeters Dough development time (min) Dough resistncy (min) Dough softening (20 min) t c c 110 As cn e seen, incresing protein content of flours cused increse the wter sorption of flour. Protein could lter the mount of wter ville to the strch. (Elisson.,1997, Osell., 2007). It cn e suggested tht this ws due to the dilution of strch y incresing protein, nd so the retrogrdtion decresed (Ottenhof., 2004). Wter sorption in flour with protein content of 9.5% ws 64.05% compred with flour t3 with 13.5%, protein ws 74.5% which showed significnt difference. p2 nd p3 with the sme protein qulity, showed different wter sorption, round nd 74.5% respectively. Differences in the wter sorptions of nd t3 were due to the different protein contents. Studies showed tht higher protein quntity, ffect dough rheologicl prmeters. Dough development time nd softening in nd t3 flours hd no significnt difference ut dough resistnce showed detectle difference, which ws 3.62 nd 4.5 respectively. Tle 6 showed tht the minimum nd mximum Enthlpy (retrogrdtion) ws oserved in reds produced y t 3 nd t 1 flours respectively. tle 6. Ttl Enthlpy vrition of reds produced y flours of different proteins Totl Enthlpy (J/g) Bred t c t t firmness(n) storge time(dy) 5 7 t3 Fig 2. The rte of stling in reds with different proteins Fig 2 sowed the lower rte of stling nd firming in the reds with higher protein. Fesss showed tht one of the resons for decresing in the perceived firmness of reds with higher protein during storge must e due to the dilution of strch tht delyed retrogrdtion, ut there is positive eltionship etween protein content nd wter sorption (Fesss, 1998). s with higher protein content hve more wter sorption. 303

5 Stling nd firming of reds is supposed to depend on the moisture content, nd in reds richer in wter, stling ws delyed (sclon,2000). 4. Conclusion DSC results indicted lower recrystliztion enthlpy (retrogrdtion) in reds with higher protein contents. Results showed tht proteins ffect dough frinogrph prmeters, red firmness nd stling. Higher protein content cused flours to hve more wter sorption. Studied showed tht more protein reduce firming nd stling of red during storge. Breds with higher protein content stled lter thn lower ones due to higher wter sorption nd strch dilution. 5. Acknowledgements We re grteful to Cerel Reserch Center, Tehrn Irn, for their lortory support. 6. REFERENCES [1] E.M. Fergestd, nd E.M, Mgnus. Interreltionship of protein composition, protein level, king process nd chrcteristics of Herth nd Pn red. J. Cerel. Sci. 2000, 31: [2] M.,Crce, nd D.Schofield. Protein- lipid interctions in whet gluten: Ressessment of the occurnce of lipidmedited ggregtion of protein in glidin frction. J. Cerel. Sci. 1996, 24: [3] C.Primo-Mrtin, N.H.Vn Nicuwenhuijzen, R.J.Hmer, nd T.Vn Vliet, Crystllinity chnges in whet strch during the red mking process: strch cristllinity in the red crust. J. Cerel. Sci. 2007, 45: [4] M.L. Mrtin, K.J. Zeleznk,, nd R.C. Hoseney. A mechnism of red firming. I. Role of strch swelling. Cerel Chem , 68: [5] E. Armero, nd C. Collr. Crum firming kinetic of whet reds with nti-stling dditives. J. Cerel. Sci. 1998, 28: [6] P.A. Ro. A.Nosiniwitch, nd P.Chinchotti, Effect of selected surfctnts on mylopectin recrystlliztion nd on recoverility of red crum during storge. Cerel Chem. 1992, 69: [7] A.Ad Krim, M.H.Norzoh, nd C. Seow. Methods for study of strch retrogrdtion. Food Chem. 2000, 71: [8] AACC. Approved methods of Anlysis of the Americn Assocition of Cerel Chemists. 10th ed. St. the Americn Assocition of Cerel Chemists. St: Pul. MN, 2000 [9] P.D.Riott. Thermo-physicl ssessment of red during stling. LWT. 2007, 40: [10] H. Jcos, J.A. Delcour. Hydrotherml modifictions of grnulr strch, with retention of grnulr strch: A review. J. Agric. Food Chem. 1998, 46: [11] M. Fukouok, K.I.Oht. H.Wtne. Determintion of the therminl extent of strch geltiniztion in limited wter system y DSC. J. Food. Engineering , 53: [12] A.C.Elisson, M.Gudmundsson, G.Svensson,. Therml ehviour of whet strch in flour reltion to flour qulity. Food Sci & Tech. 1995, 28(2): [13] C.A. Osell, H.D.Snchez,, C.R.Crrr, M.A.De l Torre, M.P. Buer,. Wter redistriution nd structurl chnges of strch during storge of gluten free red. Strch. 2005, 57: [14] M.A.Ottenhof, nd I.A.Frht, The effect of gluten on the retrogrdtion of whet strch. J. Cerel Sci. 2004, 40: [15] D.Fesss, A. Schirldi,. Texture nd stling of whet red crum: Effect of wter extrctle proteins nd pentosns. Thermochemic Act. 1998, 323: [16] M.G. Sclon, H.D. Spirstein, nd D.Fhloul. Mechnicl properties of red crum prepre from flours of different dough strength. J. Cerel. Sci. 2000, 32: