Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Avenue, St. Paul, Minnesota 55108, USA.
J Agric Food Chem. 2012 Oct 24;60(42):10625-33. doi: 10.1021/jf302402k. Epub 2012 Oct 11.
In recent years, the intermediate-moisture foods (IMF), such as nutrition and energy bars, are a rapidly growing segment of the global food market. However, due to moisture-induced protein aggregation, commercial high protein nutrition bars generally become harder over time, thus losing product acceptability. In this study, the objectives were to investigate the moisture-induced protein aggregation in a hen egg white proteins/water dough model system (water activity (a(w)): 0.95) and to evaluate its molecular mechanisms and controlling factors. During storage at three different temperatures (23, 35, and 45 °C) for 70 days, four selected physicochemical changes of the dough system were analyzed: the a(w), the color (L* value), the fluorescent Maillard compounds (fluorescence intensity (FI) value), and the remaining free amino groups. Overall, the physicochemical changes of egg white proteins in the dough system are closely related to the glass transition temperature (T(g)). The effect of moisture content on both the L* and FI values occurred as a function of storage time at 45 °C due to the Maillard reaction. The change of the remaining free amino groups at different temperatures was derived from the coaction of both the Maillard reaction and enzymatic hydrolysis from molds. Additionally, through analyzing the buffer-soluble egg white proteins using gel electrophoresis, our results showed that moisture-induced aggregates were produced by two chemical reactions during storage: the disulfide interaction and the Maillard reaction. Furthermore, the effect of two processes during manufacturing, desugarization and dry-heat pasteurization, on the physicochemical changes of the egg white proteins was elucidated. In order to prevent or reduce moisture-induced protein aggregation during product storage and distribution, two potential solutions were also discussed.
近年来，中间水分食品（IMF），如营养能量棒，是全球食品市场增长最快的部分。然而，由于水分引起的蛋白质聚集，商业高蛋白营养棒通常会随着时间的推移变得越来越硬，从而失去产品的可接受性。本研究旨在研究蛋清蛋白/水面团模型体系（水分活度（a w ）：0.95）中水分诱导的蛋白质聚集，并评估其分子机制和控制因素。在 23、35 和 45°C 下储存 70 天期间，分析了面团体系的四个选定的物理化学变化：a w 、颜色（L值）、荧光美拉德化合物（荧光强度（FI）值）和剩余游离氨基。总体而言，面团体系中蛋清蛋白的物理化学变化与玻璃化转变温度（T g ）密切相关。在 45°C 下，由于美拉德反应，水分含量对 L和 FI 值的影响是随储存时间变化的。不同温度下剩余游离氨基的变化是由美拉德反应和霉菌酶解的共同作用引起的。此外，通过凝胶电泳分析缓冲可溶蛋清蛋白，结果表明，水分诱导的聚集是在储存过程中由两种化学反应产生的：二硫键相互作用和美拉德反应。此外，还阐明了脱糖和干热巴氏杀菌这两个在制造过程中的两个过程对蛋清蛋白物理化学变化的影响。为了防止或减少产品储存和分销过程中水分诱导的蛋白质聚集，还讨论了两种潜在的解决方案。
