Faculty of Chemistry, Biotechnology and Food Science (KBM), Norwegian University of Life Sciences (NMBU), Box 5003, N-1433 Ås, Norway.
Faculty of Chemistry, Biotechnology and Food Science (KBM), Norwegian University of Life Sciences (NMBU), Box 5003, N-1433 Ås, Norway; TINE SA R&D, Bedriftsveien 7 Kalbakken, 0901 Oslo, Norway.
J Dairy Sci. 2020 Sep;103(9):7927-7938. doi: 10.3168/jds.2020-18237. Epub 2020 Jul 16.
Cheese made from microfiltration (MF) retentate may suffer from textural defects due to a high Ca concentration. The reduction of colloidal minerals by the acidification of milk before MF at pH below 6.0 has been well documented in the literature. This process, however, creates less valuable side streams to the MF process and induces changes in the casein micelles that negatively affect their coagulation properties. The objective of this study was to determine whether a minor reduction in pH by using different acidifiers in the diafiltration (DF) water could induce changes in composition and renneting properties of the MF retentate. A 2-stage filtration process was used, with the first designed to increase the casein concentration to 8% and the second to slightly reduce the casein concentrate by 0.1 pH unit by DF, without influencing the total protein concentration. Four acidifying agents were tested during DF: lactic acid, hydrochloric acid, citric acid, and carbon dioxide. Diafiltration with water was used as a reference. At the start of DF, the retentates of acid DF had a slightly reduced pH, with an average of 0.09, whereas the pH of the reference retentate increased by an average of 0.07 unit. The reference retentate regained its starting pH by the end of DF. The carbonated retentate gradually increased in pH during processing, whereas the pH of the lactic, hydrochloric, and citric acid retentates remained constant. The permeate from the lactic acid and carbonated treatments had a reduced whey protein content compared with the reference. The total P and inorganic phosphate were lowered in the retentate by using carbonation. The total amount of Mg and Na were lowered in the retentate by using citric acid. The ionic Ca content in the retentate increased with use of lactic or hydrochloric acid. The type of acidifier used reduced the rennet clotting time. Combined acidified diafiltration with a slight reduction affects the permeate composition and improves the retentate clotting time despite the minimal mineral modification.
用微滤（MF）截留物制成的奶酪可能由于钙浓度高而存在质地缺陷。在 MF 之前，通过将牛奶酸化至 pH 低于 6.0 可以很好地去除胶体矿物质，这在文献中已有记载。然而，该过程会给 MF 过程带来价值较低的副产物，并导致酪蛋白胶束发生变化，从而对其凝结特性产生负面影响。本研究的目的是确定在渗滤（DF）水中使用不同酸化剂进行轻微的 pH 值降低是否会引起 MF 截留物组成和凝乳特性的变化。使用两阶段过滤工艺，第一阶段设计用于将酪蛋白浓度增加到 8%，第二阶段通过 DF 略微降低酪蛋白浓缩物 0.1 pH 单位，而不影响总蛋白浓度。在 DF 期间测试了四种酸化剂：乳酸、盐酸、柠檬酸和二氧化碳。用去离子水渗滤作为参考。在 DF 开始时，酸化 DF 的截留物的 pH 值略有降低，平均降低 0.09，而参考截留物的 pH 值平均增加 0.07 个单位。参考截留物在 DF 结束时恢复其起始 pH 值。碳酸化截留物在加工过程中 pH 值逐渐升高，而乳酸、盐酸和柠檬酸截留物的 pH 值保持不变。与参考相比，乳酸和碳酸化处理的渗透物中的乳清蛋白含量降低。碳酸化处理降低了截留物中的总磷和无机磷酸盐。柠檬酸处理降低了截留物中的总镁和钠含量。用乳酸或盐酸处理会增加截留物中的离子钙含量。酸化剂的类型会降低凝乳凝结时间。尽管矿物质的修饰很小，但使用轻微酸化的联合渗滤会影响渗透物的组成并改善截留物的凝结时间。
