Effect of Storage of Skim Milk Powder, Nonfat Dry Milk and Milk Protein Concentrate on Functional Properties

The physicochemical changes during the storage of high protein powders, such as skim milk powder (SMP), nonfat dry milk (NDM), and milk protein concentrates (MPC), can result in a variation in the functional properties of the powders. The objective of this study was to evaluate the effects of the storage of various milk powders (SMP, NDM, MPC40, and MPC70) on their functional properties. Three different lots of the powders were collected from US manufacturers and were analyzed for functional properties after 3, 9, and 15 months of storage at 25 °C. Additionally, this study also evaluated the effects of seasonal variation on the functionality of SMP and NDM. Functional properties, such as solubility, emulsification ability index (EAI), foaming, and surface hydrophobicity index (SHI), were evaluated at each storage time point. The solubility of MPC70 and the foam overrun of SMP, MPC40, and MPC70 decreased significantly (p < 0.05) with an increase in the storage time. The emulsification properties of MPC70 were significantly higher than other powders. Except for foam drainage, there was no effect of the season on the SMP and NDM functional properties. The storage of milk powders has an impact on some functional properties, and a proper selection of powders based on end-use is recommended.