Effect of Different Air Oven Temperatures on Chemical, Physical, and Microbial Properties of Dried Bio-Yoghurt Product

Abstract

The aim of this study was to compare the physical, chemical, and microbiological features of bio-yoghurt that had been air-oven-dried at three temperatures (40, 50, and 60 °C) to those of fresh bio-yoghurt. The results showed that drying bio-yoghurt at 40–60 °C decreased the number of probiotic starter bacteria in dried yoghurt products compared to fresh bio-yoghurt. The dried yoghurt’s moisture, protein, fat, carbohydrate, and ash contents were 4.16–4.55%, 38.22–40.02%, 1.33–1.43%, 47.94–49.45%, and 6.37–6.55%, respectively. The pH and total acidity levels of dried yoghurt were within acceptable ranges at various temperatures and storage durations. At different temperatures, the viscosity values of the products decreased by 620–550 cp; however, the hygroscopicity values remained constant. During a 90-day storage period, the dried yoghurt product’s physical, chemical, and microbiological characteristics remained within acceptable levels. Using a drying temperature of 40–50 °C kept the number of live bacteria below acceptable ranges during storage periods. Lactobacillus acidophilus counts were 6.75 and 6.70 log CFU/g, respectively, whereas Bifidobacterium bifidum numbers were 6.66 and 6.08 log CFU/g, respectively. In conclusion, drying bio-yoghurt in an air oven at 40–50 °C provided a dried product with a high number of viable probiotic bacteria and satisfactory physicochemical characteristics after 3 months.