Effect of spray drying temperature of yoghurt on the survival of starter cultures, moisture content and sensoric properties of yoghurt powder

Abstract

A synergistic set of the strains Lactobacillus delbrueckii subsp. bulgaricus 151 and Streptococcus thermophilus MK-10 was preserved with the method of spray drying. Studies were performed on the effect of outlet air temperature in range of 60–80°C upon the survival of yoghurt cultures, as well as the moisture content and sensoric properties of yoghurt powder. Survival of yoghurt cultures was the highest at 60 and 65°C, but excessive moisture (10.2%) of yoghurt powder had a negative effect on its texture. Moisture content of the powder was low at 80°C (4.4%( unfortunately sensoric faults appeared at this temperature, and survival of bacteria cultures decreased considerably. Temperatures within the range 70–75°C ensured satisfactory survival of yoghurt cultures (L. delbrueckii subsp. bulgaricus – 13.7–15.8%; S. thermophilus – 51.6–54.7%( maintained proportion of the strains (L : S–1 : 3( satisfactory moisutre content (5.1–6.3%( and good sensoric properties of yoghurt powder.