The thermal transitions of spray-dried (SD) and freeze-dried (FD) egg whites containing unfreezable water (i.e., lower water contents) and freezable water (i.e., higher water contents) were measured by differential scanning calorimetry (DSC). For the SD and FD samples containing unfreezable water (0.039–0.282 and 0.043–0.206 g water/g sample (w.b.) in SD and FD samples), the denaturation temperatures (T_d) of ovotransferrin and ovalbumin were observed in both the SD and FD samples. However, it was difficult to identify the glass transition temperature (T_g) of the egg whites. The T_g was only detected in SD egg whites with low water contents (0.039–0.093 g water/g sample (w.b.)). For the SD and FD samples containing freezable water (0.32–0.72 and 0.31–0.73 g water/g sample (w.b.) in SD and FD samples), the glass transitions were not detected, and only the freezing points (T_F) and the end point of freezing (T_m′) were observed. The unfreezable water content and the corresponding characteristic end point of freezing (T_m′)_u of the SD samples were both greater than those of the FD samples. The heat denaturation of egg white proteins and different protein solubility (water-binding capacity) may cause the different thermal transitions between SD and FD egg whites. But the Guggenheim-Anderson-de Boer (GAB) monolayer water contents of the SD and FD egg white powders were similar. The results are useful for selecting the optimal process and storage conditions for dried and frozen egg whites.

通过差示扫描量热法（DSC）测量了包含不可冻结的水（即，较低的水含量）和不可冻结的水（即，较高的水含量）的喷雾干燥（SD）和冷冻干燥（FD）蛋白的热转变。对于含有不可冻结水的SD和FD样品（SD和FD样品中的水为0.039-0.282和0.043-0.206 g水/ g样品（wb）），在SD和FD中均观察到卵转铁蛋白和卵清蛋白的变性温度（T _d）。 FD样本。但是，难以确定蛋白的玻璃化转变温度（T _g）。的Ť_克仅在水含量低（0.039–0.093 g水/ g样品（wb））的SD蛋清中检测到。对于含有可冻结水的SD和FD样品（SD和FD样品中的水为0.32-0.72和0.31-0.73 g水/ g样品（wb）），未检测到玻璃化转变，仅检测到冰点（T _F）和冰点。观察到冷冻终点（T _m ′）。所述unfreezable水含量和冷冻（对应的特征终点Ť_米'）_ÜSD样本的百分比均大于FD样本的百分比。蛋清蛋白的热变性和不同的蛋白溶解度（水结合能力）可能会导致SD和FD蛋清之间的热转变不同。但是SD和FD蛋白粉的Guggenheim-Anderson-de Boer（GAB）单层水含量相似。结果对于选择干燥和冷冻蛋白的最佳工艺和储存条件很有用。