Antifirming effects of starch degrading enzymes in bread crumb.

Antifirming properties of amylases in bread crumb were evaluated in straight dough breadmaking and related to the amylolytically modified starch structure. Amylase properties and action mechanisms determine starch structure in the breads and, hence, how amylopectin recrystallization, starch network formation, water redistribution, and water mobility occur during breadmaking and storage. A bacterial endo-alpha-amylase mainly hydrolyzed the longer starch polymer chains internally. It thus reduced the number of connections between the crystallites in the starch networks, resulting in a softer bread crumb. However, because the enzyme had only little impact on the outer amylopectin chains, amylopectin recrystallization and the concomitant water immobilization presumably were not hindered. The loss of plasticizing water as a result of recrystallization presumably reduces the flexibility of the gluten network and results in poor crumb resilience. In contrast, in breadmaking, the Bacillus stearothermophilus maltogenic alpha-amylase acted as an exoacting amylase with more pronounced endoaction at higher temperatures. This enzyme caused extensive degradation of the crystallizable amylopectin side chains and thus limited amylopectin recrystallization and network formation during storage. As a result, it prevented the incorporation of water in the amylopectin crystallites. In this way, the different starch and gluten networks kept their flexibility, resulting in a softer crumb with good resilience.