Optimization of Vacuum Freeze-Drying Technology of yam Powder by Response Surface Methodology

In order to optimize the vacuum freeze-drying technology of yam powder, the single factor test was carried out with the retention rate of polysaccharide as the index. On this basis, the response surface method was used to investigate the comprehensive effects of drying pressure, sublimation heating temperature and analytical heating temperature on the protein retention rate, polysaccharide retention rate and water content of yam powder. The comprehensive score of normalization treatment of multiple indicators was used as the response value to determine the optimal process of vacuum freeze-drying of yam powder. At the same time, the microscopic morphology of yam powder was observed by scanning electron microscope（SEM）and laser confocal scanning microscope（CLSM）. The results showed that each factor had a very significant effect on the comprehensive score （P＜0.01）, followed by drying pressure＞sublimation heating temperature＞analytical heating temperature. The optimum process parameters of vacuum freeze-drying of yam powder were as follows: drying pressure of 43 Pa, sublimation heating temperature of 45℃ and desorption heating temperature of 68℃. The yam powder prepared under this condition retained a complete honeycomb porous structure without obvious collapse or deformation. This study can provide theoretical basis and practical reference for the industrial production of high-quality yam powder.