Storage-induced solubility loss in plant-based emulsion powders

Developing plant-based milk powder alternatives with similar nutritional profiles and functionalities to dairy powders poses significant challenges, particularly related to their rehydration and dispersion properties. In this first-of-its-kind study, factors affecting the solubility of plant-based emulsion powders during storage were investigated. To examine the impact of material properties and processing, model emulsions with varying protein sources (pea, soy), protein content (2.4%, 20%), lipid type (sunflower, MCT), and processing conditions were spray-dried and stored under controlled conditions for 16 weeks. For the first time, storage-induced insolubility was shown to occur in plant-based emulsion powders, resulting in final powder insolubility from 7 to 51%, depending on the formulation. Storage further decreased protein solubility and free fat extractability in most samples. Protein content and the presence of lipids were found to be the most relevant factors influencing plant powder solubility during storage, while processing conditions and protein source were determined not to have a relevant impact. It is suggested that changes in protein conformation and enhanced protein-protein interactions due to oxidation and glycation contribute to the formation of an insoluble protein micro-gel network during storage, dramatically decreasing solubility. In addition, oxidative polymerization of unsaturated lipids like sunflower oil increased powder hydrophobicity, inhibiting wetting properties and the extractability of free fat. The current findings offer valuable insights into the structural changes occurring in plant-based emulsion powders during storage, highlighting the intricacies of protein-protein and protein-lipid interactions. • Storage induced insolubility in soy- and pea stabilized emulsion powders. • Protein denaturation during storage lead to the formation of an insoluble network. • Polymerization of free lipids lead to increase in hydrophobicity.