Department of Food Physics and Meat Science, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstrasse 21/25, Stuttgart 70599, Germany.
Department of Soft Matter Science and Dairy Technology, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstrasse 21, Stuttgart 70599, Germany.
Food Res Int. 2019 Feb;116:283-290. doi: 10.1016/j.foodres.2018.08.037. Epub 2018 Aug 18.
Protein solubility in water is a key property of food proteins. The aim of this work was to study the solubility and microstructural properties as a function of pH of both protein fractions (water-soluble (WSPE) and water-insoluble protein extracts (WISPE)) obtained from the microalga Chlorella protothecoides, which is promising for food use. Protein solubility was determined as the ratio of protein concentration in the supernatant after centrifugation to total protein concentration. An unusually high solubility and only slight gravitational separation across a very broad pH-range (2-12) were observed for the WSPE with a minimum protein solubility of 84.3 ± 2.2% at pH 2. The origin of this high pH-independent protein solubility was attributed to a high degree of glycosylation and a high amount of hydrophilic amino acids. In contrast, the WISPE was found to contain strongly aggregated proteins, and these large aggregates separated rapidly from solution by gravitation independent of the pH. This corresponded to their protein solubility, which was overall low in the pH-range of 2-11, and only increased at pH 12 to a maximum solubility of 26.9 ± 2.8%. These results suggest that the WSPE of Chlorella protothecoides may exhibit unique properties for food formulations, allowing for example for both acidified, neutral or slightly alkaline foods to be formulated, whereas WISPE may be more suited for foods where phase separation is rather slow.
蛋白质在水中的溶解度是食品蛋白质的一个关键特性。本工作的目的是研究从微藻原绿球藻中获得的两种蛋白质级分（水溶性（WSPE）和水不溶性蛋白质提取物（WISPE））的溶解度和微观结构性质随 pH 的变化，原绿球藻有望用于食品。蛋白质溶解度是通过离心后上清液中蛋白质浓度与总蛋白质浓度的比值来确定的。WSPE 的溶解度异常高，在非常宽的 pH 范围（2-12）内仅略有重力分离，在 pH 2 时最低蛋白质溶解度为 84.3±2.2%。这种高 pH 不依赖的蛋白质溶解度的起源归因于高度的糖基化和大量的亲水氨基酸。相比之下，WISPE 被发现含有强烈聚集的蛋白质，这些大的聚集体在 pH 无关的情况下通过重力迅速从溶液中分离出来。这与其蛋白质溶解度相对应，其在 pH 2-11 范围内总体上较低，仅在 pH 12 时增加到最大溶解度 26.9±2.8%。这些结果表明，原绿球藻的 WSPE 可能具有独特的食品配方特性，例如可以用于酸化、中性或略碱性食品的配方，而 WISPE 可能更适合于相分离较慢的食品。
