Acid Stable α-Amylase Supplementation in Sourdough Enhanced Lactic Acid Bacterial Performance and the Quality of Bread

Abstract

The effects of an acid-stable α-amylase AmyE from Aspergillus niger on the growth and fermentative ability of sourdough-fermenting Lactobacillus plantarum (LP) were studied and the accompanying changes in the dough rheological properties, specific volume of bread, crumb texture, and the microstructure of dough and bread were analyzed. Addition of acid-stable α-amylase AmyE in the sourdough at a concentration of 15 U/g significantly increased population of LP to 11.61 log CFU/g and accelerated acidification process compared to the commercial α-amylase supplemented sourdough and the control (non-amylase treated) during 24 h fermentation. Tensile test showed that adding AmyE induced an increase in maximal dough resistance to stretching and a decrease in extended distance. From scanning electron microscopy (SEM) images, the microstructure of dough displayed an advanced stage of granules swelling and much more deformation with increasing levels of α-amylase. The microstructure of breads prepared with AmyE was more homogeneous with increasing number of gas cells and resulted in improvement of specific volume and softness of bread crumbs. Given the aforementioned benefits of AmyE for lactic acid bacterial performance and bread quality, this acid-stable α-amylase AmyE has the potential as an improved enzyme additive for sourdough bread production.