Milk, microbes, modern science and technology: High temperature short time microwave heating pasteurization technique in the production of yoghurt

In this study, the production of yoghurt products was investigated from powdered milk through high temperature short time (HTST) microwave pasteurization at 75 oC for 10 minutes as an innovative alternative technique to conventional thermal treatments. Moreover, the influence of storage conditions was studied on the viscosity, pH, and microbial growth of these microwave pasteurized yoghurt products. The investigations were examined under both ambient and refrigeration conditions with and without preservatives over the storage regimes. The results demonstrated that refrigeration consistently preserved viscosity more effectively than shelf storage, reflecting reduced microbial proliferation, slower enzymatic degradation, and minimized syneresis. In the absence of preservatives, viscosity declined rapidly under shelf storage, underscoring the critical importance of cold-chain logistics for maintaining product quality. However, the inclusion of preservatives significantly enhanced the product stability, inhibiting microbial growth and proteolysis. The viscosity of the products with preservatives under refrigeration was synergistically kept and maintained nearly unchanged, while under ambient was gradually declined and could not prevent its loss over the storage regimes. The observed differences can be mechanistically attributed to the interplay of protein degradation during the longer holding time pasteurization, the suppressing of microbial growth by preservatives, and the dominant effects of refrigeration through syneresis control.