Determination of the Direct Activity of the Maltogenic Amylase from Geobacillus stearothermophilus in White Bread

Abstract

Abstract An assay-based method was developed to determine the residual activity of the maltogenic amylase from Geobacillus stearothermophilus in white bread. It was found that the important step for amylase extraction from the bread matrix was the addition of 10% (w/v) maltodextrin in the extraction buffer. The endogenous amylase activity in dough was investigated, and its inactivation during bread baking was proven. Thus, all amylase activities measured after baking have an exogenous origin. The amylase activities in the loaf of self-baked white bread containing defined dosages of exogenous amylase (10–100 μg per g flour) were reproducibly determined with 17.8 ± 1.24% residual activity. Moreover, an amylase activity of 369 ± 34.3 pkat g bread −1 was determined in three batches of a commercial white bread. The real temperature impact on the amylase during bread baking was investigated. The highest temperature in the crumb was 97 °C and, therefore, is significantly lower than the oven temperature (230 °C).