Goesaert Hans, Leman Pedro, Bijttebier Annabel, Delcour Jan A
Laboratory of Food Chemistry and Biochemistry and Leuven Food Science and Nutrition Research Centre (LFoRCe), Katholieke Universiteit Leuven, Leuven, Belgium.
J Agric Food Chem. 2009 Mar 25;57(6):2346-55. doi: 10.1021/jf803058v.
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.
在直接法面包制作中评估了面包瓤中淀粉酶的抗固化特性，并将其与经淀粉酶改性的淀粉结构相关联。淀粉酶的特性和作用机制决定了面包中的淀粉结构，进而决定了在面包制作和储存过程中支链淀粉重结晶、淀粉网络形成、水分重新分布以及水分流动性的发生方式。一种细菌内切α-淀粉酶主要在内部水解较长的淀粉聚合物链。因此，它减少了淀粉网络中微晶之间的连接数量，从而使面包瓤更柔软。然而，由于该酶对外层支链淀粉链的影响很小，支链淀粉重结晶以及随之而来的水分固定可能并未受到阻碍。重结晶导致的增塑水损失可能会降低面筋网络的柔韧性，并导致面包瓤弹性不佳。相比之下，在面包制作中，嗜热脂肪芽孢杆菌麦芽ogenicα-淀粉酶作为一种外切淀粉酶，在较高温度下具有更明显的内切作用。这种酶导致可结晶支链淀粉侧链大量降解，从而在储存期间限制了支链淀粉重结晶和网络形成。结果，它阻止了水分掺入支链淀粉微晶中。通过这种方式，不同的淀粉和面筋网络保持了它们的柔韧性，从而产生了具有良好弹性的更柔软的面包瓤。
