Factors influencing the physical and chemical stability of whey permeate powders: A correlational study based on...

Whey permeate is an important co-product of cheese manufacturing, commonly converted into a powder (WPP) through evaporation, lactose crystallization, and spray drying. The composition of whey permeate powders (WPPs) varies and is influenced by the properties of the cheese produced and the processing parameters used during manufacturing. WPPs may undergo physical and chemical changes, including the Maillard reaction and caking, during storage and transportation, thereby impacting the functional and physical properties of the final product. Therefore, this work aims to establish correlations between parameters related to the physical and chemical stability of whey permeate powders (WPPs) and the content of major and minor constituents, including lactose, monosaccharides, organic acids, protein and nitrogen-containing compounds, and minerals. For this purpose, 15 commercial WPPs were collected from 4 different producers in the United States and subjected to compositional analysis and a shelf-life test for 6 mo at T = 25 ± 2°C and a relative humidity (RH) of 50 ± 5% to induce browning. From the compositional analysis of the 15 WPP samples, it was established that their range in composition is representative of literature values for WPPs, allowing us to generalize our results. The observed correlations were analyzed in the form of a correlational heat map and by principal component analysis (PCA). We find that the glass transition temperature (T_g), which serves as a proxy for molecular mobility and which is related to the propensity of powder caking, positively correlates with the lactose content, while it negatively correlates with the content of glucose, galactose, and lactic acid, which are all strong plasticizers. We observe that the color change (ΔE*) during storage, which is used as a proxy for the degree of Maillard browning, negatively correlates with the lactose content, demonstrating the critical impact of molecular mobility on the rate of browning. ΔE* positively correlates with the content of glucose, galactose, and lactic acid. This is expected specifically for glucose and galactose, which are both reducing sugars and strong plasticizers. The protein and peptide content only weakly correlates with both T_g and the degree of browning, while the impact of minerals is more complex, in particular in relation to the physical stability of WPPs. Overall, our results improve the understanding of compositional variability of WPPs and its effect on instability, providing concrete direction for process optimization and reformulation, and constitute a basis for further mechanistic studies.