Storage stability of powdered dairy ingredients: a review

Powdered dairy ingredients are added in various food products to impart desired technofunctional properties, improve nutritional values, and sensory characteristics. These ingredients undergo various changes during storage, the extent of these changes is a function of powder composition, processing parameters, and storage conditions. Most of the changes in powder characteristics are associated with the change in free moisture content that occurs due to change in headspace relative humidity and temperature. Uptake of moisture results into various undesirable changes including decrease in Tg, crystallization of lactose, alteration in color (Maillard browning), oxidation of lipids, modifications of protein conformation, changes in surface composition, and particle morphology. These changes adversely affect the physicochemical characteristics, functional properties, and sensory attributes of these ingredients. Crystallization of lactose alters the microstructure and surface chemical composition of powders, induces caking and compromises flowability and solubility. Maillard reactions increase protein-sugar and protein-protein interactions which compromises color and solubility. The composition of powdered dairy ingredients and products, if they are rich in lipids and lactose, are particularly sensitive to changes in headspace RH and temperature. Longer Storage times consolidate the underlying mechanisms driving the undesirable changes mentioned above. This review shows that to preserve the quality of these ingredients during storage, it is essential to design storage parameters (relative humidity, temperature, vapor, and gas barrier of primary packaging) of powdered dairy ingredients and products such a way that crystallization of lactose, lactose-protein interaction, and melting of lipid and migration of lipid to the surface is minimized.