Study of enzymes addition on wheat-soy bread quality

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

Madrid, Spain

Congreso; 13th ICC Cereal and Bread Congress. Cereals in the 21st century: present and future; 2008

ICC International

The use of soy flour improves the nutritional value and health benefits of the traditional bread. However, incorporation of high levels of soy protein depresses loaf volume, gives poor crumb characteristics and decreases acceptability. Incorporation of enzymes can be of great help in overcoming these problems. Pentosanases (Pn) acts by cleaving the backbone of arabinoxylans (AX) modifying their functionality, thus improves the gluten elasticity, volume and bread softness (Courtin and Delcour, 2002). Glucose oxidase (Gox) and Transglutaminase (TG) are enzymes that increase the dough strength. The Gox mechanism of action is not completely understood; various theories include the gelative oxidation of pentosans and the strengthening of the protein crosslinking mechanism via the disulfide network (García et al 2002). TG action produces the formation of new covalent bonds between proteins reinforcing gluten structure (Larré et al., 2000). The objective of this study was to determine the effect of pentosanase, glucose oxidase and transglutaminase on the rheological properties of wheat-soy dough and the bread quality. The formulation included: 680 g wheat flour, 120 g defatted soy flour, water, 24 g of yeast, 17.6 g of NaCl, and enzymes (0.006% and 0.012% of Pn; 0.001% and 0.01% of Gox; 0.05% and 0.3% of TG) (flour basis). Dough rheological properties were evaluated by micro-extension procedure and CO2 retention capacity. Specific bread volume, crust color of breads and texture profile analysis were determined. Enzyme incorporation influenced the micro-extension properties of wheat-soy dough. Pn increased the extensibility and decreased slightly the resistance. Gox and the highest TG dose incremented significantly the resistance and decreased the extensibility, these results may be due to the effect of Gox and TG in the S-S formation and/or AX crosslinking. Compared to the control (without enzyme), Pn-bread gave the highest bread volume while the highest dose of TG decreased it. The CO2 retention capacity of dough showed the same tendency that bread volume. Texture parameters showed an inverse relationship with bread volume. Pn addition decreased crumb firmness whatever the storage period thus improving the crumb characteristics while TG (0.3%) increased crumb firmness. Gox and the lowest level of TG decreased crumb firmness after storage for 3 days indicating that, at these levels, enzymes retard crumb texture deterioration. Only breads with TG addition showed a lower intensity of crust color than the control. Pentosanase, glucose oxidase and low doses of transglutaminase had a positive effect on soy-wheat bread quality, but high dose of transglutaminase was detrimental.