Dept. of Food Technology, Faculty of agriculture, Univ. of Kafrelsheikh, Kafrelsheikh, Egypt.
Div. of Food Technology, Inst. of Human Nutrition and Food Science, Kiel University, 24118, Kiel, Germany.
J Food Sci. 2018 Aug;83(8):2092-2100. doi: 10.1111/1750-3841.14222. Epub 2018 Jul 14.
The covalent interactions between whey protein isolate (WPI) and rosmarinic acid (RosA) at two different conditions, alkaline (pH 9) and enzymatic (in the presence of tyrosinase, PPO), at room temperature with free atmospheric air were studied. The conjugates formed between WPI and RosA were characterized in terms of their physicochemical and functional properties. The changes in protein structure were analyzed by intrinsic fluorescence and binding of 8-anilino-1-naphthalenesulfonic acid. The findings show that the covalent interactions caused a decrease in free amino and thiol groups and tryptophan content at both conditions. The decrease at enzymatic conditions was lower than at alkaline conditions. In addition, modified WPI at alkaline conditions exhibited higher antioxidative capacity compared to the modification at enzymatic conditions. However, WPI modified at enzymatic condition showed mild antimicrobial activity against Staphylococcus aureus LMG 10147 and MU50 compared to WPI modified at alkaline conditions and unmodified WPI (control). The modified WPI can be used as multifunctional ingredient into various food products with an additional health promoting effect of the bound phenolic compounds.
在碱性（pH 9）和酶促（存在酪氨酸酶、PPO）两种不同条件下，于室温下在自由大气空气中研究了乳清蛋白分离物（WPI）与迷迭香酸（RosA）之间的共价相互作用。根据其物理化学和功能特性对 WPI 和 RosA 之间形成的缀合物进行了表征。通过内源荧光和 8-苯胺-1-萘磺酸结合分析了蛋白质结构的变化。结果表明，在两种条件下，共价相互作用导致游离氨基和巯基以及色氨酸含量减少。酶促条件下的减少低于碱性条件下的减少。此外，与酶促条件下的修饰相比，碱性条件下修饰的 WPI 表现出更高的抗氧化能力。然而，与碱性条件下修饰的 WPI 和未修饰的 WPI（对照）相比，在酶促条件下修饰的 WPI 对金黄色葡萄球菌 LMG 10147 和 MU50 具有温和的抗菌活性。修饰的 WPI 可用作多功能成分添加到各种食品产品中，从而具有结合的酚类化合物的额外促进健康的作用。
