Abstract Milk protein isolate (MPI) powder is an important food ingredient powder but it has poor wettability and dissolution ability which limit its functional usage. The effect of pH (5.4–8.4) on the wettability and dissolution of MPI powder is evaluated in this study. Contact angle and Washburn methods were used to measure the wetting behaviour of MPI powder. Its dissolution ability was measured by static light scattering in real-time after a pre-mixing step. The results showed that the contact angle of droplets on compacted powder tablets exhibited no significant difference between pH conditions (p > 0.05) and this was supported by the results of the Washburn method. It was found that MPI dissolution was strongly correlated with the appearance of submicron size casein micelles in the solution. During dissolution, higher pH caused an earlier appearance of this casein micelle submicron peak and a higher swelling peak associated with the swelling of casein micelle aggregates. This swelling of casein micelle aggregates indicates greater water penetration and loosening of the aggregate structure at higher pH, which facilitated faster dissolution of MPI powder, especially at a pH of 8.4. This study indicates changing alkaline environment could be potential to apply in MPI rehydration.

中文翻译：

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pH值对乳分离蛋白粉润湿溶解的影响

摘要 乳分离蛋白（MPI）粉是一种重要的食品配料粉，但其润湿性和溶解性差，限制了其功能使用。本研究评估了 pH (5.4-8.4) 对 MPI 粉末润湿性和溶解性的影响。接触角和Washburn方法用于测量MPI粉末的润湿行为。在预混合步骤后，通过静态光散射实时测量其溶解能力。结果表明，压实粉末片剂上液滴的接触角在 pH 条件之间没有显着差异 (p > 0.05)，这得到了 Washburn 方法结果的支持。发现 MPI 溶解与溶液中亚微米级酪蛋白胶束的出现密切相关。在解散过程中，较高的 pH 值导致这种酪蛋白胶束亚微米峰的出现较早，并且与酪蛋白胶束聚集体的溶胀相关的溶胀峰更高。酪蛋白胶束聚集体的这种膨胀表明在较高的 pH 值下有更大的水渗透和聚集体结构的松散，这促进了 MPI 粉末的更快溶解，尤其是在 pH 值为 8.4 时。该研究表明，不断变化的碱性环境可能适用于 MPI 补液。