School of Health Sciences, University of Ballarat, Mount Helen, VIC 3353, Australia.
Food Chem. 2013 Nov 15;141(2):702-11. doi: 10.1016/j.foodchem.2013.03.035. Epub 2013 Mar 19.
The extent and nature of denaturation of whey protein isolate (WPI) in convective air drying environments was measured and analysed using single droplet drying. A custom-built, single droplet drying instrument was used for this purpose. Single droplets having 5±0.1μl volume (initial droplet diameter 1.5±0.1mm) containing 10% (w/v) WPI were dried at air temperatures of 45, 65 and 80°C for 600s at constant air velocity of 0.5m/s. The extent and nature of denaturation of WPI in isothermal heat treatment processes was measured at 65 and 80°C for 600s and compared with those obtained from convective air drying. The extent of denaturation of WPI in a high hydrostatic pressure environment (600MPa for 600s) was also determined. The results showed that at the end of 600s of convective drying at 65°C the denaturation of WPI was 68.3%, while it was only 10.8% during isothermal heat treatment at the same medium temperature. When the medium temperature was maintained at 80°C, the denaturation loss of WPI was 90.0% and 68.7% during isothermal heat treatment and convective drying, respectively. The bovine serum albumin (BSA) fraction of WPI was found to be more stable in the convective drying conditions than β-lactoglobulin and α-lactalbumin, especially at longer drying times. The extent of denaturation of WPI in convective air drying (65 and 80°C) and isotheral heat treatment (80°C) for 600s was found to be higher than its denaturation in a high hydrostatic pressure environment at ambient temperature (600MPa for 600s).
采用单液滴干燥法测量和分析了乳清蛋白分离物（WPI）在对流空气干燥环境中的变性程度和性质。为此目的，使用了定制的单液滴干燥仪器。使用体积为 5±0.1μl（初始液滴直径 1.5±0.1mm）、浓度为 10%（w/v）的 WPI 单液滴，在空气温度为 45、65 和 80°C、空气速度为 0.5m/s 的条件下干燥 600s。在 65 和 80°C 下进行 600s 的等温热处理过程中，测量了 WPI 的变性程度，并与对流空气干燥获得的结果进行了比较。还确定了 WPI 在高静水压环境（600MPa 下 600s）中的变性程度。结果表明，在 65°C 下对流干燥 600s 后，WPI 的变性程度为 68.3%，而在相同的中等温度下进行等温热处理时，仅为 10.8%。当介质温度保持在 80°C 时，WPI 的变性损失分别为 90.0%和 68.7%，在等温热处理和对流干燥过程中。发现 WPI 中的牛血清白蛋白（BSA）部分在对流干燥条件下比β-乳球蛋白和α-乳白蛋白更稳定，尤其是在较长的干燥时间内。在对流空气干燥（65 和 80°C）和等温热处理（80°C）条件下，WPI 的变性程度在 600s 内比在室温下（600MPa 下 600s）的高静压环境中的变性程度更高。
