Faculty of Life and Environmental Sciences, Shimane University, 1060, Nishikawatsu, Matsue, Shimane, 690-8504, Japan.
Institute for Biomedical Sciences, Iwate Medical University, 1-1-1 Idai-dori, Yahaba-cho, Shiwa-gun, Iwate, 028-3694, Japan.
Sci Rep. 2022 Sep 9;12(1):15253. doi: 10.1038/s41598-022-17911-8.
Basket clam soup, a popular Asian dish, is prepared by boiling clams in hot water. The soup is generally cloudy, and it is considered that increased cloudiness enhances taste. However, the composition of the whitening ingredients and their association with taste enhancement remains unclear. In this study, we aimed to identify the components contributing to the white colour of the boiled soup. The white component upon precipitation with trichloroacetic acid reacted positively with ninhydrin, indicating the presence of proteins. The separation of proteins using sodium dodecyl sulphate-polyacrylamide gel electrophoresis revealed an intense band of size 33 kDa. Peptide mass fingerprinting of the identified protein using matrix-assisted laser desorption/ionisation-time-of-flight tandem mass spectrometry revealed the protein as tropomyosin. To validate the involvement of tropomyosin in the turbidity of the soup, tropomyosin was expressed and extracted from Escherichia coli. As expected, the purified protein suspended in water resulted in turbid appearance. To determine whether lipids have any association with the observed cloudiness of the soup, the amounts of fatty acids were measured. The proportion of estimated fatty acids was very low compared to that of proteins. Overall, we identified the major component contributing to soup cloudiness as tropomyosin forming micelles.
文蛤汤是一道流行的亚洲菜肴，通过将蛤在热水中煮沸来制作。这种汤通常是混浊的，人们认为增加混浊度可以提高口感。然而，增白成分的组成及其与口感增强的关系尚不清楚。在这项研究中，我们旨在确定导致煮出的汤呈白色的成分。用三氯乙酸沉淀得到的白色成分与茚三酮反应呈阳性，表明存在蛋白质。用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分离蛋白质时，发现一条 33 kDa 的强烈条带。基质辅助激光解吸/电离-飞行时间串联质谱法对鉴定出的蛋白质进行肽质量指纹图谱分析表明，该蛋白质为原肌球蛋白。为了验证原肌球蛋白在汤浑浊度中的作用，从大肠杆菌中表达和提取了原肌球蛋白。不出所料，纯化的蛋白质悬浮在水中会呈现混浊外观。为了确定脂肪是否与汤的混浊度有关，我们测量了脂肪酸的含量。与蛋白质相比，估计脂肪酸的比例非常低。总的来说，我们确定了导致汤混浊的主要成分是形成胶束的原肌球蛋白。
