Investigating different gel structures formed by bovine casein micelles, goat casein micelles, and reassembled casein micelles.

This proposal describes a new approach to making animal-free dairy products by producing casein from microorganisms and then assembling them into casein micelles. The gelation of casein micelles is an essential step towards dairy products such as yoghurt and cheese. To investigate the possibility of making dairy products with this approach, we would like to compare the gel structure formed by native casein micelles (extracted from milk) with reassembled casein micelles (made with lab-purified caseins). Small-angle X-ray and neutron scattering have been shown to be a suitable method to describe the internal structure of casein micelles. However, after acidification or renneting, casein micelles tend to aggregate, and the aggregated structures are too big for small-angle scattering. Spin-echo small-angle neutron scattering (SESANS) has been shown to be a powerful tool for investigating milk gels (Tromp & Bouwman, 2007). Therefore, we would like to apply SESANS measurement on native casein micelles (NCMs) and reassembled casein micelles (RCMs) gels to investigate their gel structures. We will prepare 5 types of micelles including NCMs from bovine and goat milk, RCMs made with bovine and goat casein composition and RCMs with increased beta-casein content. We will also apply a heat treatment on those micelles. With this experiment, we expect to gain important knowledge on how casein micelles source, casein composition and heat treatment affect the gel structure formation.

本提案介绍了一种无动物乳制品的全新制备方案：通过微生物发酵生产酪蛋白，再将其组装为酪蛋白胶束（casein micelles）。酪蛋白胶束的凝胶化是制备酸奶、奶酪等乳制品的核心必要步骤。为探究该路径制备乳制品的可行性，我们计划对比天然酪蛋白胶束（从牛乳中提取）与重组酪蛋白胶束（由实验室纯化酪蛋白制备而成）所形成的凝胶结构。小角X射线散射与中子散射已被证实为表征酪蛋白胶束内部结构的有效手段，但经酸化或凝乳酶处理后，酪蛋白胶束易发生聚集，此时聚集产物的尺寸过大，无法通过小角散射进行表征。自旋回波小角中子散射（Spin-echo small-angle neutron scattering, SESANS）已被证明是研究乳凝胶的有力工具（Tromp & Bouwman, 2007）。因此，我们拟对天然酪蛋白胶束（native casein micelles, NCMs）与重组酪蛋白胶束（reassembled casein micelles, RCMs）形成的凝胶开展SESANS测量，以探究其凝胶结构。我们将制备五类胶束样品：牛乳与山羊乳来源的天然酪蛋白胶束，基于牛、山羊酪蛋白组分制备的重组酪蛋白胶束，以及β-酪蛋白含量提升的重组酪蛋白胶束；同时将对上述所有胶束样品进行热处理。通过本实验，我们期望阐明酪蛋白胶束来源、酪蛋白组分及热处理方式对凝胶结构形成的影响机制，获取关键研究数据与认知。