Effect of spray drying parameters on survival rate of lactic acid bacteria and physical properties of lychee yogurt powder

The objective of this study was to explore the influencing regularities of spray drying parameters on the survival rate of microencapsulated lactic acid bacteria in lychee yoghurt powder and its physical properties.Effects of feed concentration, inlet temperature, feeding rate on survival rate of lactic acid bacteria, moisture content and yield of lychee yoghurt powder microencapsulated by spray drying were investigated. Under the better spray drying condition, the influences of trehalose on production quality were further investigated. The results showed that with 25% ~ 30% feed concentration, 140 ℃ inlet air temperature, 6.5¹0.0 m L/min pump rate, the lychee yoghurt powder illustrated the high survival rate of lactic acid bacteria and yield ( > 50%) , and the low moisture content ( 4.66% ~ 4.79%) . Under this condition, the survival rate of lactic acid bacteria, moisture content and yield reached 73.94% ( 6.34 × 10⁸CFU/g) , 4.72% and 37.79% respectively with 6% trehalose added.Scanning electron microscopy ( SEM) photographs showed that the addition of 6% ( w/w) trehalose made particles more rounded surfaces and smaller cracks than the control. The probiotic powder was further analyzed using differential scanning calorimetry ( DSC) , the glass transition temperature Tg = 71.61 ℃.