Abstract Dry heating (DH) at 100 °C of a whey protein isolate powder conditioned at pH 9.5 leads to the formation of stable, large and porous whey protein microparticles (WPM), resulting from crosslinking of proteins in the powder. The Maillard reaction (MR) is probably involved in the formation of these WPM. To confirm the role played by the MR and understand the protein changes occurring during particle formation, we analyzed the properties of the powders (such as their water activity (aw) and color) and characterized the WPM formed after 3 and 36 h of DH in powders with increasing amounts of added lactose. Adding lactose and prolonging the time of DH increased the extent of protein denaturation and the rate of formation of WPM and the yield of conversion of powder into WPM, but led to decreases in their water content. Addition of lactose also altered the kinetics of the MR, the increase in aw and the formation of WPM. The MR, as followed by powder browning, was complete within 3 h of DH irrespective of the amount of added lactose. In contrast, the increase in aw, thought to be due to progress of the MR, continued to increase from 3 to 36 h of DH. Formation of WPM went on increasing from 3 to 36 h of DH at low to medium levels of lactose, but was complete by 3 h of DH at high levels of lactose. In conclusion, the formation of WPM was not simply related to the MR and needs further investigation.

中文翻译：

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乳糖对碱性pH下干加热乳清蛋白微粒形成的影响

摘要 在 100 °C 下干燥加热 (DH) 在 pH 9.5 条件下的乳清分离蛋白粉末会导致形成稳定、大且多孔的乳清蛋白微粒 (WPM)，这是由粉末中蛋白质的交联产生的。美拉德反应 (MR) 可能与这些 WPM 的形成有关。为了确认 MR 的作用并了解颗粒形成过程中发生的蛋白质变化，我们分析了粉末的特性（例如它们的水分活度 (aw) 和颜色）并表征了 DH 3 和 36 小时后形成的 WPM。添加乳糖的粉末。添加乳糖和延长DH的时间增加了蛋白质变性程度和WPM的形成速度以及粉末转化为WPM的产率，但导致其含水量降低。添加乳糖还改变了 MR 的动力学、aw 的增加和 WPM 的形成。无论添加多少乳糖，在 DH 后 3 小时内完成 MR，然后是粉末褐变。相比之下，被认为是由于 MR 进展导致的 aw 增加从 DH 的 3 小时持续增加到 36 小时。WPM 的形成在低至中等乳糖水平下从 DH 3 小时增加到 36 小时，但在高乳糖水平下形成 3 小时 DH。综上所述，WPM 的形成不仅与 MR 相关，还需要进一步研究。DH 从 3 小时持续增加到 36 小时。WPM 的形成在低至中等乳糖水平下从 DH 3 小时增加到 36 小时，但在高乳糖水平下形成 3 小时 DH。综上所述，WPM 的形成不仅与 MR 相关，还需要进一步研究。DH 从 3 小时持续增加到 36 小时。WPM 的形成在低至中等乳糖水平下从 DH 3 小时增加到 36 小时，但在高乳糖水平下形成 3 小时 DH。综上所述，WPM 的形成不仅与 MR 相关，还需要进一步研究。