Improvement of the rheological properties of dough using transglutaminase and asparaginase enzymes, whey powder and inulin

A mixture of wheat flour, water, salt, yeast and other optional ingredients such as preservatives, enzymes, whey powder, surfactants, sugar, fibres and improvers form bread dough. Enrichment of dough and bakery products by dietary fibres such as wheat bran and resistant starch, beta-glucans and inulin has been reported (Peressini, & Sensidoni, 2009; Hager, Ryan, Schwab, Gänzle, O’Doherty, &Arendt, 2011; Wang, Rosell, Barber, 2002; Angioloni, Collar, 2008). Whey has many applications in food and dairy industries due to its high quality of nutrients and functional properties. It possesses essential amino acids (Mann, 1998; Sharma, & Bhatia, 1999). There are other alternatives such as transglutaminase and asparaginase enzymes as innovative ingredients, which are recognized as safe in the food technology. The microbial transglutaminase enzyme (MTG) catalyzes the reaction between a ε-amino group of lysine residues and a β-carboxyamide group of glutamine residues, which causes to make covalent cross-linking of proteins (Yokoyama, Nio, & Kikuchi, 2004). Asparaginase (ASP) can catalyze the hydrolysis of asparagines, as a key factor for acrylamide formation, into aspartic acid and ammonia (Ciesarova, Kukurova, &Benesova, 2010). The present work was undertaken to study the influence of whey powder, inulin, asparaginase and transglutaminase enzymes on farinograph and extensograph properties of wheat flour dough using a D-optimal design.

Two types of wheat as insect damaged (50% insected) and sound hard red wheat (imported variety), milled into two types of flour by traditional mill. The characteristics of the flours such as moisture, ash, protein, falling number, wet gluten and Zeleny-value were determined using AACC methods (2000) in three replicates. Enzymes included MTG and ASP and other applied additives such as inulin (Frutafit-HD) and whey powder used at different levels based on flour weight in dough formulation. Effect of enzymes, additives and wheat flour types (WFT) on farinograph and extensograph characteristics were conducted according to the constant flour weight procedure of AACC (2000). D-optimal design was used to determine the effects of five independent variables including MTG, ASP, whey powder, inulin, and flour type on farinograph and extensograph properties. Response data were used to fit the second-order polynomial equation. Normal probability was used for separation of significant effects from noise or random effects. The significance of each coefficient in the regression model was determined using p-value lower than 0.05. Adequacy of models for regression were estimated using coefficient of determination (R2) and adjust R2 (adj-R2).

According to chemical and physical analysis of flour, it is obvious that in spite of having nearly the same amount of protein and wet gluten, the two types of flour had prominent difference in dough and gluten quality as indicated by gluten index and farino-extensograph tests. Due to this fact, the wheat flours with gluten index of 5.43±4.31 and 76.93±5.87 were named as weak and strong flours, respectively. Analytical data of farinograph properties were fitted to regression models. Analysis of variance of lack-of-fit test showed that the water absorption model is adequate with a non-significant lack of fit (p=0.267) and a satisfactory adj-R2 (97.53%). Among the different additives, strong wheat flour had positive effect and inulin and whey powder had negative effect on water absorption. According to half-normal plot and regression model coefficients, wheat flour type, inulin and whey powder significantly affected dough development time (DT) and stability (S). The models of DT and S had R2 values of 88.58%, 98.45% and non-significant lack of fits p=0.087 and p=0.018, respectively. DT and S increased with an increase in inulin and whey powder level using strong wheat flour. The regression model for degree of softening as a function of different ingredients was significant at a p-value less than 0.0001. Based on analysis of variance, the model appeared to be adequate with a non-significant lack of fit p=0.017 and a R2 value of 97.57%. Among the investigated factors, wheat flour showed the greatest positive effect on the degree of softening followed by inulin. The degree of softening was decreased by addition of inulin and whey powder. Among the interaction terms, a negative interaction effect on degree of softening was found between MTG and ASP (p<0.05). The regression model for farinograph quality number (f.q.n) possessed a good fitness with experimental data, with a high R2 value (98.59%) and non-significant lack of fit. Interaction effect between wheat flour type and inulin on the f.q.n was significant at a p-value less than 0.0001. Usage of inulin, whey powder and strong wheat flour improved and elevated f.q.n. The regression model for energy value as a function of different ingredients was significant at a p-value less than 0.0001 with an R2 value of 94.22%. Among the investigated factors, inulin and MTG had significant single positive effect on energy value. The energy value increased with the addition of whey powder to dough formula. This increase was more evident in the strong flour samples. Regression analysis revealed that interaction between wheat flour type and MTG had the most pronounced effect on dough resistance to extension (R) followed by inulin. A progressive increase in this parameter was observed with increasing MTG dosage especially along with strong wheat flour. Inulin and whey powder had also positive effect on it.

The model for extensibility (Ex.) had an R2 value of 86.29% and non significant lack of fit (p=0.124). Among the investigated factors, flour type showed the most pronounced positive effect followed by inulin on extensibility. Dough extensibility was increased by adding whey powder. The regression model for R/Ex. ratio as a functional of different ingredients was significant at a p-value of < 0.0001 with an R2 value of 81.73%. Among the applied factors, the flour type and MTG had pronounced influence on R/Ex. ratio.