Abstract:

The purpose of this work was to obtain Chinese yam powder with better solubility and reconstituability through
enzymatic hydrolysis followed by spray drying. The optimization of spray drying parameters for improved drying efficiency
was carried out by using response surface methodology (RSM), where the effects of air-inlet temperature, hot air flux and
feed flow rate on the powder yield of dried yam were analyzed. Proximate composition and properties of the power product
were determined. Results showed that the total soluble solids content of yam hydrolysate was 82.79% when the hydrolysis
was performed using 0.2% α-amylase for 45 min at 70 ℃ and initial pH 7.0; after subsequent vacuum concentration to
17%, the hydrolysate was spray dried at an air-inlet temperature of 180 ℃, air flow rate of 28.60 m3/h, and feeding rate of
1 060 mL/h, resulting in a powder yield of 37.59% with good solubility, color and flavor, water content smaller than 5%, and
high suitability for long-term storage. Therefore, the combination of enzymatic hydrolysis and spray drying method allows
the production of higher-quality Chinese yam powder.

Key words: Chinese yam, enzymatic hydrolysis, spray drying, response surface methodology (RSM)