Impact of different vacuum oven drying temperature on the chemical, physical, and microbial characteristics of a dried probiotic yogurt product during cold storage

Abstract

The objective of this research was to prolong the storage life of probiotic yogurt and facilitate its handling and transportation, in addition to preserving the physicochemical characteristics and vitality of probiotic bacteria within the permissible ranges, during storage periods. The results showed the possibility of preserving probiotic yogurt dried at three different temperatures of 40, 50, and 60 °C and pressures of 0.5 millibars to maintain its physical and chemical characteristics within acceptable ranges. The number of bacteria decreased during the storage period, but the number of bacteria that enabled them to perform their therapeutic function remained maintained. The moisture, protein, fat, carbohydrate, ash contents, pH levels, and total acidity of probiotic yogurt of 4 %, 30.01%, 1.4%,5 4.68%, 7.89%, 4.2, and 1.1%, respectively, were within acceptable ranges at different temperatures and storage periods. Several tests were conducted on dried yogurt samples, including X-ray diffraction, electron microscopy, and thermal analysis. This demonstrated the extent of the effect of temperature and the drying process on the structure of dried probiotic yogurt after reconstitution and the extent of its effect on the bonding of the yogurt components with each other.