The influence of reducing and oxidising agents on rheology of wheat flour dough

ACTA UNIVERSITATIS AGRICULTURAE ET SILVICULTURAE MENDELIANAE BRUNENSIS SBORNIK MENDELOVY ZEMEDELSKE ALESNICKE UNIVERZITY VBRNE Number 5,2008 gen and non-covalent ionic bonds and hydrophobic interactions (Popineau et ai., 1994; Shewry et al., 1994; Shewry and Tatham, 1997;Belton, 1999;Lindsay and Skerrit, 1999). Recognition and understanding of the relationship between viscoelastic properties of gluten and both density and distribution of cross-links forming the three-dimensionalgluten structure still remain the main objectives of cereal biochemistry and rheology (Bloksma, 1990; Cornee et aI., 1994;Shewryet aI., 1994;Janssen et aI., 1996; Shewry and Tatham, 1997;Belton, 1999;Lindsay and Skerrit, 1999;Lefebvre etai.,2003). Additives bring an improvement in the machine abilityof dough as well as the quality and other sensory attributes of the finished product. The use of additives helps not onlyimprove but also maintain the quality of bakery products. Some additives are used by the milling industry and others are used by the bakery industry. Additives can be divided into oxidants and reductants. Cole (1973) reported thatoxidants promote formationofdisulphide bonds among the extendedgluten 22 163 Abstract Received:July 31,2008 P. Pecivova, V. Pavlinek, J. Hrabe, S. Kracmar INFLUENCE OF REDUCING AND OXIDISING AGENTS ON RHEOLOGY OF WHEAT FLOUR DOUGH aornnve.dough, gluten, amino acid, rheology classes are based on hardness, colour and season of wheat varieties. Hard wheat has protein content than soft wheat and is used for yeast-raised products. Soft wheat is used chemicallyleavenedproducts. 'iscoetasuc properties of a gluten protein maafundamental impact on the rheological of wheat bread dough. When the dough mixing, gluten proteins form a conviscoelastic network mznout the dough embedding discrete rigid starch granules. This quasi-solid structure lUU.U>l'-''-'- into aqueous phase composed of soluolysaccharides, proteins and emulsified lipids, adough liquor, and closes dispersed gas phase rm of air bubbles. Therefore, wheat gluten can tmsidered a simplified model of a viscoelastic ton of dough. Essentially; wheatgluten is comaofpolymerised glutenins and gliadins, which recently been referred to as wheat prolamins et al., 1994; Shewry and Tatham, 1997). ~.hree-dilne][1S10n:al structure of gluten matrix by covalent (disulfide) bonds, hydroPECIVOV A, P.,PAVLINEK, v., HRABE, J., KAACMAR,S.:The influence of reducing and oxidising agents on therheoIogyofwheatflourdough.Acta univ. agric. etsilvic. Mendel. Brun., 2008, LVI,No.5, pp.163-170 The effects of a reducing agent (L-cysteine hydrochloride monohydrate), oxidising agents (inactivated dry yeast, L-tyrosine) and other two amino acids (L-threonine and L-tryptophan) on the rheologicalcharacteristics ofwheatflour dough and its qualitywerestudied. The addition of oxidisingagents increases the values such as tenacity and decreases extensibilitywhichwere measured on the alveograph. From the consistographvalues,weakeningof the dough also decreases.Whilereducingagents increase the extensibility and weakeningof the dough, they decrease its deformation energy.The addition ofL-tryptophancausedahigherincreasein tenacityof the dough but on the other hand alarger decrease in extensibility and deformation energy. L-tryptophan caused better stabilityof the dough. t-... "'.rn ...-i......" was found to be an oxidising agent. The dough with L-threonine weakened rapidly and Y'\"'~'Y'\,., ... "t-i A ...... of the dough isnecessary. It meansthat the timeofmixing and dough prooVolumeLVI L-threonine L-tyrosine OH O~ ~OH Wheat flour White wheat flour (moisture 14.3%,gluten in dry matter 36.4%, Falling number 339 s) provided by Penam,Kromeffz, CzechRepublic, sodium chloride and redistilledwaterwere used in the study. Additives Amino acids L-tyrosine, L-threonine, L-tryptophan (Merck KGaA, Darmstadt, Germany); L-cysteine hydrochloride monohydrate, inactivated dry yeast (Ireks GmbH, Eppelbom, Germany) were used for wheat flour modification within the concentration range of 0.08-0.14 wt.% (calculated on the amount of flourin dough composition). Chemical formulas are shown in Fig. 1. Totally 24 samples were prepared and analysed. a slow oxidising agent (e.g. potassium bromate) to increase gluten breakdown early in the process and glutenreformationlaterin the process. The aim of the study was to compare two amino acids such as L-threonine and L-tryptophan against three known amino acids already used in flour modification (L-cysteine hydrochloride monohydrate, inactivated dry yeast and L-tyrosine). Considering chemical structure, it was investigated whether the addition of L-threonine and L-tryptophan leads to gluten networking by uncovalent disulphide bonds and hence oxidation effects. These amino acids were added at increasing concentrations and their influence on the rheological properties of wheatflour dough was evaluated. MATERIAL AND METHODS P. PeCivovd, v Pavl{nek, J Hrabe, S. Krdcmar OH 0, NH l hl / II y".V,o OVI~NH~ NH2SH glutathione L-tryptophan OH Lcvstelne 1: Structure of aminoacids 164 molecules and thus impart gas-retaining and doughstrengtheningproperties to glutenfilms. Moss (1974) reported that oxidising agents make the dough stiffer as a result of cross-linking of protein molecules, whereas reducing agents weaken the dough as a result of splitting of disulfide bonds, resultingin areductionin molecularsize. It isalso reported that the main reactionofoxidants is oxidation of afree sulphidegroupinto disulphide moieties; gluten proteins of flour are thought to be the main target ofthis oxidation and the desirable effects of oxidants are marked strengthening or an increase in dough elasticity,improvedmachine ability and an increased volume of the final loaf (Stauffer, 1990b). Reducing agents (like L-cysteine or gluthathione) belongto dough conditioner used to reduce mixing time and improve extensibility. They are added to bread to increase bakery throughput and adjustfor flour variation, and in a number of other yeast and chemically leavened applications. Disulfide bonds in gluten are broken mechanically during mixing but they can be broken chemically by cysteine or glutathionereactions. Cysteine is a protein amino acid that has a sulfhydryl group at the end of the molecule. Cysteine is important to dough reduction chemistrybecause it occurs in gluten protein from flour, in tripeptide glutathionefromyeast, and in afree amino acid form as asyntheticreducingagent. During mixing, gluten in flour is stretched and pulled. It meansthatit can be reformedduring proofing and bakingtoprovide the strength and structure needed. Oxidising and reducing agents can be used separately.Moreover, areducing agent can be used with L - extensibility, P /L -configurationratio, Gdough swelling, W-deformationenergy The influenceof reducing and oxidisingagents on rheologyofwheatflour dough 165 TprMax as the time to reach maximum pressure in seconds, Tol (Tolerance, stability) as the time in seconds where the pressure is higher than PrMaxminus 20%,dropin pressureat250 secondfromPrMax minus 20% (D250) and drop in pressure at 450 second from PrMax minus 20%(D450). RESULTS AND DISCUSSION Figures2 and 3illustrate the effectof the individual oxidising or reducing agents where only the highest concentrations of the amino acids investigated are shown while Tables I and II summarize the results for all dough samples. The same concentrations of the individualamino acids were used in dough comConcentration(10-2 %) P L P/L GW (mm) (mm) (em") (10-4J) Control dough 95 89 1.06 21.0 287 L-cysteine hydrochloride monohydrate 1.3 53 55 0.96 16.5 74 1.5 51 52 0.98 16.0 66 46 43 1.07 14.5 53 93 93 1.01 21.4 291 92 91 1.01 21.2 280 92 93 0.99 21.4 286 93 92 1.01 21.3 288 93 91 1.02 21.3 288 107 86 1.24 20.7 315 106 91 1.16 21.2 320 95 95 1.00 21.7 303 96 86 1.12 20.6 289 96 89 1.07 21.0 295 113 74 1.54 19.1 309 112 74 1.51 19.2 307 114 70 1.62 18.7 305 97 86 1.13 20.7 294 97 82 1.19 20.2 286 98 81 1.21 20.0 282 97 79 1.23 19.8 275 98 83 1.18 20.2 285 98 82 1.19 20.1 284 98 89 1.11 21.0 304 I11P{)/J'I",1hh characteristics of investigated doughs Rheologicalcharacteristics The rheological characteristics of wheat flour dough were measured using Alveoconsistograph (Chopin -Tripette &Renauld, France) according to the methods AACC 54-30A and 54-50, respectively. The bread-making quality was estimated using parameters such as tenacity (P),taken as the height of the curve which measures the initialresistanceto extension (forming the bubble); the lengthof the curve (L),whichis an index of dough extensibility; the P /L ratio,which indicates the balance of the viscoelastic components of dough; and the deformation energy (W), whichindicates dough strength. Consistograph parameters evaluatedwere the folmaximum pressure in millibars (PrMax), II: Consistograph characteristics o/investigated doughs *PrMaxmaximum pressure, TPrMaxtime to reach maximum pressure, Toltime thatpressureis higher than PrMAX minus 20%, D 250 - the drop in pressure at 250 seconds from PrMax minus 20%, D 450 - the dropin pressureat 450secondsfromPrMax minus 20%. *mb (millibar) - the device is calibratedon values mb Concentration (102 %) PrMax TPrMax Tol D250 D450 (mb) (s) (s) (mb) (mb) Control dough 2237 173 241 197 742 Lscysteine hydrochloride monohydrate 1.3 2169 87 104 1257 1513 1.5 2150 83 95 1372 1607 1.8 2142 80 94 1405 1636 Inactivated dry yeast 1.3 2249 164 242 204 711 1.5 2257 158 242 220 742 1.8 2157 155 294 136 638 3.0 2157 160 264 160 663 5.0 2286 160 268 188 711 10.0 2165 168 277 117 628 14.0 2218 164 278 124 652 L-tryptophan 1.3 2240 166 279 141 690 1.5 2299 138 280 321 792 1.8 2199 164 274 129 652 5.0 2240 168 297 89 666 10.0 2254 149 304 173 693 14.0 2243 186 275 101 662 Lsthreonlne 1.3 2208 151 280 199 708 1.5 2281 172 266 141 708 1.8 2237 145 268 212 745 3.0 2240 158 258 220 722 L-tyrosine 1.3 2264 142 282 170 692 1.5 2163 154 278 155 651 1.8 2206 162 261 188 719 values. This effect is causedby the abilityof cysteine to break disulphidic bonds and disturb the structure of gluten causing increased impalpability and stickiness of dough, which becomes less cohesive and worse in processing. Previous studies [Moss, 1974; Bloksma, 1990] showed reducing influence of cysteine on disulphidic bonds. L-cysteine hydrochloridemonohydrateis astrongreducingagent and thereforeonlyasmall amount canbe addedtodough. It is suitablefor modificationof strongflours. P. Peeivovd, v.- Pavl£nek, J Hrabe, S. Krdcmar 166 position. However, where the influence of amino acid on the rheologicalproperties of dough samples was not evidentat low concentrations, ahigher concentrationwas applied. The addition of L-cysteine hydrochloride monohydrate into wheat flour dough causes a decrease in its tenacity and extensibility compared to control dough (Table I). The higher the concentration, the larger the decrease ofpropertiesobserved.However, Table II shows deterioration of dough stability and faster weakening indicated by D250 and D450 3000 ,...------------------....., 500400 crease in tenacity and adecrease in extensibility can be seen (TableI). From the results summarised in Table II, one can notice higher stability of the dough with the addition of L-tryptophan and slower softening compared to the dough with the addition of inactivated dry yeast. Very interesting results can be seen in the modification of dough with 0.014 wt.% of L-threonine -greater strength but lower extensibility than the dough with L-tryptophan or inactivated dry yeast (Table I). At the same time, its stabilityis higher than that of inactivated dry yeast but lower than that of L-tryptophan (Table II). D250 and D450 stabilityvalues indicate the fastest softeningof dough with L-threonine. Therefore L-tryptophan was found to be the strongest oxidative agent, followed by inactivated dry east and L-threonine.Faster softening of dough with L-threonine can be eliminated by rapid processing and reduction of mixing and fermentation times. The last amino acid investigated (L-tyrosine) exhibits a weak oxidative effect on gluten structure. L-tyrosineis ableto reinforce the gluten network and the dough becomes cohesive and more elastic. Similar information about ability of L-tyrosine to create and strengthen gluten bonds was mentioned by authors [Bradyet al., 1996; Pefiaet al., 2006]. All oxidative agents were found to be suitable additives for wheat flours. Thanks to their ability to create gluten bonds, the doughs havegreater strength and elasticity. Stronger oxidative additives cause a stronger dough structure and improved cohesion. nine, shorter processing time, i.e. reduced mixing and fermentation time, should "be used. L-tyrosine can be used as an oxidising additive as well, but its instability in dough prevents serious practical application. Oxidants are able to strengthen the gluten network and thus increase the elasticityof dough, as a result of which bakery products have an increased volume and better porosity 100 100 af c 01L------'----'-----'-----'-------1 o 50 l(mm) 3: Consistograph curves forthe control dough (a) and dough with the highest used concentration of particular additives L-cysteine hydrochloride monohydrate (b), inactivated dry yeast (c), L-tryptophan (d), L-threonine (e) and L-tyrosine (f). o 100 E g50 ::r:: The influence of reducing and oxidisingagents on rheology of wheat flour dough 167 ~ 2000 1---+rF-,~~---=:::::~~.",._-------l e! ~ en en e 0. 1000 CONCLUSION results showed that from the five amino acids estigated, only L-cysteine hydrochloride monorate is a reductant while the others are stronger eaker oxidants. L-tryptophan was found to be most suitable oxidising agent, followed by inacfed dry yeast and L-threonine. However, in order iminatefast softeningof the dough with L-threo2: Alveograph curves forthe control dough (a) and dough with the highest used concentration ofparticular additives L-cysteine hydrochloride monohydrate (b), inactivated dry yeast (c), L-tryptophan (d), Lthreonine (e) and L-tyrosine (f). three amino acids investigated, I.e. inactiyeast, L-tryptophan and L-threonine, exmuch less oxidative activity. The strongest ffect is observed for L-tryptophan where, within econcentrationrange of 0.1-0.14wt.%, a higher in- přísada, těsto, gluten, aminokyselina, reologie This work was kindly supported by a project of Czech Ministryof Education, Youth and Sports(Grant No. MSM 7088352101). SOUHRN vliv redukčních a oxidačních činidel na reologii pšeničného těsta Aminokyseliny jsou stavebními bloky bílkovin a proteinů. Mají široké rozpětí užití v potravinář ských procesech a manipulacích snutrienty, dietními doplňky, obohacovači vůně, náhražkami soli, zabarvovači, antioxidanty, konzervovadly, tvarovačí, posilovači a kypřidly na těsto. Je známo, že kvalita tvorby pšeničného těsta záleží jak na kvantitě, tak na kvalitě jeho glutenovýchbílkovin. Gluten je viskoelastický bílkovinný komplex mající jak elastické, tak viskózní vlastnosti. Gluten obsahuje dva hlavní typy bílkovin, a to glutenin, který hlavně přispívá kelastickým vlastnostem glutenu, zatímco gliadin k viskózním vlastnostemglutenu. 'TYto vlastnostise ale právě přídavkem oxidačních či redukčních činidel dají ovlivnit, a to tak, že jednotlivé aminokyselinyreagujís glutenovou sítí, se kterou jsou schopny tvořit vazby, a tak více posilovat tuto síť (funkce oxídovadel), či naopak rozbíjet tuto glutenovou síť, jak je tomu např. u námi zmiňovaného L-cysteinu hydrochloridu monohydrátu. 'TYto redukční či oxidační činidla lze samozřejmě také vhodně kombinovat, a tak docílit požadovaných viskoelastickýchvlastností těst. Byly studovány účinky redukčních činidel (L-cystein hydrochlorid monohydrát), oxidačních činidel (inaktivovanédroždí,L-tyrosin) adalších dvou aminokyselin L-threoninu aL-tryptofanu na reologické vlastnosti těsta a jeho kvalitu. Přídavek oxidačních činidel zvyšuje hodnoty jako je pevnost asnižoval tažnost naměřené na alveografu, a z konzistografických hodnot snižoval měknutí těsta; zatímco redukční činidla zvyšovala tažnost a měkkost těsta, snižovala deformační energii těsta. Přídavek L-tryptofanu zvýšil pevnost těsta, ale na druhé straně více snížil tažnost a deformační energii těsta. L-tryptofandává těstu lepší stabilitu. L-threonin byl oxidačním činidlem. Těsto s L-threoninemrychleji měklo, proto rychlá příprava těsta je nezbytná. Což znamená, že čas míchání a kynutí musí být zkrácen. P. Pečivovd, v.- Pavlínek, J Hrabě, S. Krdčmar function perspectives. Trends in Food Science & Technology, 10:247-253. MOSS, R., 1974: Dough microstructure as effected by the addition of cysteine, potassium bromate and ascorbic acid. Cereal Science Today, 19: 557. PENA, E., BERNARDa, A., SOLER, C., N., 2006: Do tyrosine crosslinks contribute to the mation of the gluten network in common (Triticum aestivum L.) dough? Journal of Cereal Science, 44: 144-153. POPINEAU, Y.,CORNEC, M., LEFEBVRE, J., CHYLO, B., 1994: Physical-chemical cnaractensa tion of glutens and glutensubfractions of genic lines of wheat "Sicco": influence of glutenin subunits on the glutenin porvmensanon and on rheological properties of CTl11ltpYl" Cereal Science, 19:231-241. SHEWRY,P.R., MILES, M. J.,TATHAM, A. S., The prolamin storage proteins of wheat and ed cereals. Progress in Biophysics 61: 37-59. SHEWR~ P. R., TATHAM, A. S., 1997: bonds in wheat gluten proteins. Journal of Science, 25: 207-227. STAUFFER, C. E., 1990a: Reductants and mix reducers. In Functional Additives for Foods (C. E. Stauffer ed.),Van Nostrand .L'\.'-'JL~~U'-'J NewYork, ~ 41-67. STAUFFER, C. E., 1990b: Oxidants. In l-11y,{'Tl,rYr Additives for BakeryFoods (C.E. Stauffer Nostrand Reinhold,NewYork,NY,1-35. 168 REFERENCES ABD ELMONEIM, o. E., and ABDULLAHI, H. E., 2002:. Effect of cysteine on bakery products from wheat-sorghum blends. Food Chemistry, 77: 133-137. BELTON, P.S., 1999: On the elasticity of wheat gluten. Journal of Cereal Science, 19:103-107. BLOKSMA, A. H., 1990: Rheology of the breadmaking process. Cereal Foods World, 35: 228-236, 959-960. BRADY, J. D.,SADLER, 1.H., FRY, S.C., 1996: Di-isodityrosine, a novel tetramericderivative oftyrosine in plant cell wall proteins: a new potential crosslinko Biochemical Journal, 315: 323-327. COLE, M. S., 1973: An overview of modem dough conditioners. Bakers Digest,47: 21-23, 64. CORNEC, M., POPINEAU, Y., LEFEBVRE, J.,1994: Characterization of gluten subfractions by SEHPLC and dynamic rheological analysis in shear. Journal of Cereal Science, 19: 131-139. JANSSEN, A. M., van VLIET, T.,VEREIJKEN, J. M., 1996: Rheological behaviour of wheat glutens at small and large deformations. Effect of gluten composition. Journal of Cereal Science, 23: 33-42. LEFEBVRE,J.,PRUSKA-KEDZIOR,A.,KEDZIOR, Z., LAVENANT,L., 2003: A phenomenological analysis of wheat glutenvíscoelastíc responsein retardation and in dynamic experiments over a large time scale. JournalofCereal Science, 38:257-267. LINDSA~ M. P. and SKERRIT, J. H., 1999: The gluten macropolymer of wheat flour doughs: structure- The influence of reducing and oxidisingagents on rheology of wheat flour dough 169 Address Pecivova, doc. Dr. Ing, Vladimir Pavlfnek, Centrum polymernich materialu, doc. Ing, Jan Hrabe, Ing, StanislavKracmar,DrSc., Ustav potravinafskehoInzenyrstvf,Fakultatechnologicka, UniverziBative Zlfne, nam, T.G.Masaryka275, 762 72 Zlm, Ceskarepublika. e-mail: peclvovagft.utb.cz.