EFFECTS OF ENZYMES IN FIBER-ENRICHED BAKING

The aim of the present study was to improve the quality of fibre-enric hed wheat breads by enzymic treatment of the fibre fraction. The suita bility of different enzymes in fibre-enriched baking and their effects on the dietary fibre content and the ratio of insoluble:soluble fibre content of the breads were studied. The enzyme preparations used were a hemicellulolytic culture filtrate of Trichoderma reesei, a specific (pI 9) xylanase of T reesei and Fermizyme, an alpha-amylase preparati on containing a standardised level of hemicellulase activity. Rye bran was extracted in water (10% (w/w) suspension) to determine the solubi lities of the beta-glucans and pentosans. Addition of T reesei culture filtrate significantly increased the amount of extractable pentosan o btained from nonautoclaved rye bran. Rye bran supplementation (5%) of wheat hour increased the farinograph absorption and dough development time, but had little or no effect on stability and softening of the do ugh. The added enzymes decreased dough stability and increased softeni ng. Addition of enzymes caused significant differences in the stickine ss of the wheat doughs both with (P < 0.003) and without (P < 0.001) r ye bran. Fermizyme significantly increased the stickiness of wheat dou ghs both with and without rye bran. The baking results of the fibre-en riched breads were improved by the added enzymes. Addition of T reesei culture filtrate increased the specific volume of the wheat breads bo th with and without rye bran by almost 20%. Enzyme mixtures were more efficient than individual xylanase in softening the bread crumb and re ducing the staling rate of wheat breads both with and without rye bran . Incorporation of enzymes reduced the total dietary fibre content of the breads, but at least doubled the amount of soluble pentosan. The p roportions of fluorescent cell walls in the breads were detected by mi croscopical image analysis. Enzyme addition caused the surface area of insoluble cell walls originating from wheat hours to decrease, sugges ting that the enzymes exert more effects on wheat endorsperm cell wall s than on bran particles. (C) 1998 SCI.