Midwest Dairy Foods Research Center, Department of Dairy Science, South Dakota State University, Brookings 57007-0647.
Midwest Dairy Foods Research Center, Department of Dairy Science, South Dakota State University, Brookings 57007-0647.
J Dairy Sci. 2018 Mar;101(3):1864-1871. doi: 10.3168/jds.2017-13670. Epub 2018 Jan 10.
Innovative clean label processes employed in the manufacture of acid gels are targeted to modify the structure of proteins that contribute to rheological properties. In the present study, CO-treated milk protein concentrate powder with 80% protein in dry matter (TMPC80) was mixed with nonfat dry milk (NDM) in different ratios for the manufacture of acid gels. Dispersions of NDM and TMPC80 that provided 100, 90, 70, and 40% of protein from NDM were reconstituted to 4.0% (wt/wt) protein and 12.0% (wt/wt) total solids. Dispersions were adjusted to pH 6.5, followed by heat treatment at 90°C for 10 min. Glucono-δ-lactone was added and samples were incubated at 30°C, reaching pH 4.5 ± 0.05 after 4 h of incubation. Glucono-δ-lactone levels were adjusted to compensate for the lower buffering capacity of samples with higher proportions of TMPC80, which is attributable to the depletion of buffering minerals from both the serum and micellar phase during preparation of TMPC80. Sodium dodecyl sulfate-PAGE analysis indicated a higher amount of caseins in the supernatant of unheated suspensions with increasing proportions of CO-treated TMPC80, attributable to the partial disruption of casein micelles in TMPC80. Heat treatment reduced the level of whey proteins in the supernatant due to the heat-induced association of whey proteins with casein micelles, the extent of which was larger in samples containing more micellar casein (i.e., samples with a lower proportion of TMPC80). Particle size analysis showed only small differences between nonheated and heated dispersions. Gelation pH increased from ˜5.1 to ˜5.3, and the storage modulus of the gels at pH 4.5 increased from ˜300 to ˜420 Pa when the proportion of protein contributed by TMPC80 increased from 0 to 60%. Water-holding capacity also increased and gel porosity decreased with increasing proportion of protein contributed by TMPC80. The observed gel properties were in line with microstructural observations by confocal microscopy, wherein sample gels containing increasing levels of TMPC80 exhibited smaller, well-connected aggregates with uniform, homogeneous pore sizes. We concluded that TMPC80 can be used to partially replace NDM as a protein source to improve rheological and water-holding properties in acid gels. The resultant gels also exhibited decreased buffering, which can improve the productive capacity of yogurt manufacturing plants. Overall, the process can be leveraged to reduce the amount of hydrocolloids added to improve yogurt consistency and water-holding capacity, thus providing a path to meet consumer expectations of clean label products.
在制造酸性凝胶时采用的创新清洁标签工艺旨在改变对流变性能有贡献的蛋白质结构。在本研究中，将 CO 处理的浓缩乳蛋白（TMPC80）与不同比例的脱脂乳粉（NDM）混合，用于制造酸性凝胶。将 NDM 和 TMPC80 的分散体配制成提供 100、90、70 和 40%NDM 蛋白的分散体，其蛋白质浓度为 4.0%（wt/wt），总固体浓度为 12.0%（wt/wt）。将分散体调节至 pH6.5，然后在 90°C 下热处理 10 分钟。添加葡萄糖酸-δ-内酯，将样品在 30°C 下孵育，孵育 4 小时后 pH 达到 4.5±0.05。调整葡萄糖酸-δ-内酯水平以补偿具有较高 TMPC80 比例的样品较低的缓冲能力，这归因于 TMPC80 制备过程中血清和胶束相缓冲矿物质的消耗。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析表明，随着 CO 处理的 TMPC80 比例的增加，未经热处理的悬浮液上清液中的酪蛋白含量增加，这归因于 TMPC80 中酪蛋白胶束的部分破坏。热处理由于乳清蛋白与酪蛋白胶束的热诱导缔合，降低了上清液中乳清蛋白的水平，在含有更多胶束酪蛋白的样品（即含有较低比例 TMPC80 的样品）中，这种缔合程度更大。粒度分析表明未经热处理和热处理的分散体之间只有很小的差异。凝胶化 pH 从约 5.1 增加到约 5.3，当 TMPC80 贡献的蛋白质比例从 0 增加到 60%时，在 pH4.5 下凝胶的储能模量从约 300 增加到约 420Pa。保水性也增加，凝胶孔隙率随 TMPC80 贡献的蛋白质比例增加而降低。观察到的凝胶性质与共聚焦显微镜的微观结构观察结果一致，其中含有不同水平 TMPC80 的样品凝胶显示出较小的、连接良好的聚集体，具有均匀、均匀的孔径。我们得出结论，TMPC80 可以部分替代 NDM 作为蛋白质来源，以改善酸性凝胶的流变学和保水性。所得凝胶的缓冲能力也降低，这可以提高酸奶生产厂的生产能力。总体而言，该工艺可用于减少添加的水胶体量，以改善酸奶的一致性和保水性，从而为满足消费者对清洁标签产品的期望提供途径。
