Combination of enzymes and oxidants in the optimization of wheat-soy bread

ROCCIA, P.; RIBOTTA, P. D.; PÉREZ, G. T.; LEÓN, A. E.

Santiago

Congreso; II Conferencia Latinoamericana de Cereales ICC; 2011

icc

Incorporation of soy flour to wheat bread increases its nutritional value. However, the acceptability of the final product is deteriorated. Enzymes and oxidants are commonly used in bakery to compensate flour quality deficiencies and to preserve freshness and bread properties. Best combinations of these additives could be used to improve the functionality of wheat flour mixed with soy flour. The statistical technique known as response surface methodology (RSM) is an alternative method that can be used to determine the optimal proportion of additives. The aim of this work was to apply the RSM to determine the best possible combination of the enzymes xylanase (XYL) and glucose oxidase (GOX), and the oxidant azodicarbonamide (ADA) to overcome the detrimental effect of soy flour addition on bread quality. Wheat-soy breads were prepared (IRAM, 1996) using 85:15 wheat:soy flours. The independent variable ranges were 0.005–0.025 g/100 g flour of XYL, 0.001–0.013 g/100 g flour of GOX and 0.001–0.005 g/100 g flour of ADA. A rotable central composite RSM with three factors and five levels was used (Statgraphics plus 5.0). Response variables were specific volume (SLV), firmness at 1 and 7 days of storage (F1 and F7, respectively), crumb structural parameters (grain uniformity U, cell total number TN, mean cell area MA, and cell fraction CF), and  crust lightness (L*). Five replicates were made at the center point of design to allow the estimation of the pure error as the sum of the square. The results were analyzed by a multiple regression method. The quality of the models’ fitness was evaluated by ANOVA (Statgraphics plus 5.0). Calculation of the optimal processing conditions was performed using a multiple response method called desirability. The results suggested that the RSM was an efficient statistical tool able to model the influence of XYL, GOX and ADA on wheat-soy bread properties. A positive quadratic effect was observed for SLV with XIL addition, whereas a linear negative effect was obtained for this response variable by GOX and ADA incorporation. These results indicated that an optimum level of XYL was necessary to improve SLV, while high GOX and ADA doses decreased it. A high negative correlation was observed between SLV and bread firmness, this result suggested a negative effect of both additives with oxidant activity, GOX and ADA, in bread staling. However, a positive effect was obtained for crumb structural characteristics from GOX and ADA incorporation. The multiple response variable optimization produced an increment between 20 and 30% in SLV and a decrease of 40% in firmness. Also, crumb uniformity and crust lightness were increased.