Kadas Erika, Oduola Abass, Rubinelli Peter M, Atungulu Griffiths G, Acuff Jennifer C
Department of Food Science, Center for Food Safety, University of Arkansas System Division of Agriculture, Fayetteville, AR 72704.
JDS Commun. 2025 Jun 3;6(5):629-634. doi: 10.3168/jdsc.2024-0683. eCollection 2025 Sep.
The water activity of milk powders is a critical parameter for predicting quality and safety, but some retailers in the supply chain may be limited to measuring moisture content, which can be easier and more affordable. Moisture sorption isotherms relate moisture content to the corresponding water activity. In this study, moisture adsorption and desorption isotherms were determined for nonfat dry milk (NFDM) and milk protein concentrate (MPC-85) powder samples at ambient and elevated temperatures via the modernized dynamic dewpoint isotherm (DDI) method. Previously cited models (with coefficients determined through linear regression) were also fit to the data for predictive applications of determining shelf life and the potential changes to quality that thermal treatments or elevated storage temperatures could cause. The adsorption isotherms of NFDM were type II, whereas MPC-85 adsorption isotherms were type III. Both NFDM and MPC-85 exhibited type III desorption isotherms, likely due to crystalline components. Temperature significantly affected the adsorption and desorption isotherms of both NFDM and MPC-85. Hysteresis was observed between the adsorption and desorption isotherms for both powders at all temperatures, but the magnitude was greater for MPC-85. The modified Oswin, modified Chung-Pfost, and Guggenheim, Anderson, de Boer models best described NFDM and MPC-85 adsorption and desorption to different degrees, highlighting that treatment and storage of the powders are influenced by both composition and temperature. These findings provide tools for prediction and assessment of quality of 2 vastly different milk powders, which inform handling, processing, and storing milk powders with different protein and lactose concentrations.
奶粉的水分活度是预测质量和安全性的关键参数，但供应链中的一些零售商可能仅限于测量水分含量，因为这更容易且成本更低。水分吸附等温线将水分含量与相应的水分活度联系起来。在本研究中，通过现代化的动态露点等温线（DDI）方法，测定了脱脂奶粉（NFDM）和浓缩乳蛋白（MPC - 85）粉末样品在环境温度和高温下的水分吸附和解吸等温线。先前引用的模型（通过线性回归确定系数）也拟合了数据，用于预测保质期以及热处理或升高储存温度可能导致的质量潜在变化。NFDM的吸附等温线为II型，而MPC - 85的吸附等温线为III型。NFDM和MPC - 85均表现出III型解吸等温线，可能是由于结晶成分。温度显著影响NFDM和MPC - 85的吸附和解吸等温线。在所有温度下，两种粉末的吸附和解吸等温线之间均观察到滞后现象，但MPC - 85的滞后程度更大。改进的奥斯温模型、改进的钟 - 普福斯特模型以及古根海姆 - 安德森 - 德布尔模型在不同程度上对NFDM和MPC - 85的吸附和解吸进行了最佳描述，突出表明粉末的处理和储存受成分和温度两者的影响。这些发现为预测和评估两种截然不同的奶粉质量提供了工具，有助于指导不同蛋白质和乳糖浓度奶粉的处理、加工和储存。
