Abstract We investigated the effect of dry heating (DH) a whey protein powder (water activity 0.24) at pH 3.5, 6.5 and 9.5 for up to 36 h at 100 °C on the structural properties of proteins. Powder browning, particle structures in suspensions reconstituted from the dry-heated powders (DHP), residual native protein content and Maillard reaction markers were studied. The browning index of the DHP rapidly increased after 6–10 h of DH and then levelled off at all pH values. β-Lactoglobulin, α-lactalbumin and bovine serum albumin were denatured by DH at all pH values. In contrast to pH 3.5 and 6.5, DH at pH 9.5 led to abundant production of microparticles. The highly heterogeneous size of these particles was related to the initial powder particle size. One g of DHP in suspension led to 20 g of hydrated microparticles made from 0.5 g of dry material. Maillard reactions at pH 9.5 were probably involved in microparticle formation.

中文翻译：

---

干加热冻干乳清蛋白粉：在 pH 9.5 时形成微粒

摘要 我们研究了在 pH 3.5、6.5 和 9.5 条件下将乳清蛋白粉（水分活度 0.24）在 100 °C 下干燥加热 (DH) 长达 36 小时对蛋白质结构特性的影响。研究了粉末褐变、由干热粉末 (DHP) 重建的悬浮液中的颗粒结构、残留的天然蛋白质含量和美拉德反应标记物。DHP 的褐变指数在 DH 6-10 小时后迅速增加，然后在所有 pH 值下趋于平稳。β-乳球蛋白、α-乳清蛋白和牛血清白蛋白在所有 pH 值下都被 DH 变性。与 pH 3.5 和 6.5 相比，pH 9.5 的 DH 导致大量产生微粒。这些颗粒的高度异质尺寸与初始粉末颗粒尺寸有关。悬浮液中的 1 克 DHP 导致由 0.5 克干材料制成的 20 克水合微粒。