Performance Improvement of Microbial and Rheological Characteristics of Dehydrated Cow-goat Yogurt Powder Based on Their Combination and Drying Methods

Abstract

Yogurt powder is dehydrated products producing by one of drying methods based on removal moisture or reduces water activity of finally product, which increase the shelf life of food. Rehydration is an importance part in viability of bacteria cells (lactic acid bacteria) in the product of powder fermented. This study is aimed to treatment cow and goat yogurt powder with rehydrate processing to provide suitable rehydration method. Methods of Ibrahim and Pestana were employed to make yogurt and drying by freeze-dryer and spry-dryer, whilst Indonesia National Standards (SNI) with Association of Official Analytical Chemistry International (A O A C), used to analysed the parameters of rehydrated yogurt. T-test were performed to evaluate the difference between data by Microsoft Excel Version 13, and separate between means used Multiple Duncan Test. The rehydration conditions consider was; powder to water ratio (1:3, 1:4, and 1:5), respectively. These results shown there was significant different between rehydrated freeze-dried and spray-dried yogurt on viscosity, pH, titratable acidity and survival bacteria cells, whilst the water to powder ratio had significant effect on features properties of rehydrated yogurt. The study results established that the rehydration water ratio 1:3 by freeze-dryer gave generally better quality compared to fresh yogurt.