Survival of Lactic Acid Bacteria during Spray Drying of Plain Yogurt

Abstract
Survival of Streptococcus salivarius subsp. thermophilus and Lactobacillus debrueckii subsp. bulgaricus was determined under various processing conditions for spray drying. Numbers of both microorganisms decreased with increased outlet or inlet air temperature, and atomizing air pressure. Outlet air temperature was a major parameter affecting number of survivors. Suitable conditions were inlet air 160°C, outlet air 60°C, atomizing air pressure 98 kPa, hot air flow 0.28 m3/ min, and feed temperature 30°C. Spray‐dried yogurt powder showed lower survival for S. thermophilus and similar survival for L. bulgaricus as compared to freeze‐dried powder.