Milk, microbes, modern science and technology: Comparative advances in ultra-high temperature and microwave heating pasteurization techniques in the production of yoghurt

This study compares the ultra-high temperature (UHT) and microwave heating pasteurization techniques. Pasteurization is one of the critical processing steps in the diary industries for the production of wide range of products including pasteurized liquid (instant, skimmed, UHT) milk, fermented milk (yoghurt, kefir, labneh), cheeses, butter, cream, ghee, condensed and evaporated milk, milk powders, and so on. It is considered as the backbone of the diary industry that safeguard and ensure products are safe, qualitative, and enjoyable. It was observed that yoghurt product quality is governed by supressing protein degradation kinetics, and inhibition of microbial activity over the storage regimes with refrigeration consistently ensuring retention and predictability for the two (2) pasteurization methods. The distributions of quality performance indicators, pH (biochemical properties) and viscosity (mechanistic features) demonstrate that UHT pasteurized product gives a wider pH distributions, approximately 68% of samples exhibited pH values between 4.288 and 4.546 (±1 SD), indicating slightly more variability in acidity whereas microwave pasteurized products show a narrower distributions, approximately 68% of samples ranged between 4.260 and 4.418 (±1 SD) for a stricter criterion, suggesting greater stability and consistency in acidity under refrigeration over the storage regimes. However, UHT-pasteurized yoghurt shows a narrower and maintain a moderate viscosity distributions, approximately 68% fell within 1,685.99–1,717.41 mPa·s (±1 SD), reflecting greater uniformity and stability, which may correspond to a smoother, lighter mouthfeel. On the other hand, microwave-pasteurized yoghurt exhibits a broader and higher spread of viscosity, approximately 68% of products ranged between 2,060.64 and 2,460.36 mPa·s (±1 SD) for a stricter criterion, indicating higher variability in texture, and suggesting a thicker and more creamier texture that could appeal to certain consumer preferences.