Effect of Different Drying Methods on Physical Properties of Sweet Potato Leaf Powder
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Abstract:
The effect of three different drying methods (hot-air drying, vacuum freeze-drying, and spray drying) on the physicochemical properties of sweet potato leaf powder from five cultivars (Ningzi No.1, Xu 053601, LangShu 7-12, Fushu No.2, and Jishu 65) were compared. Physicochemical quality evaluation indices for the powder samples were selected by principal component analysis. The results showed that the drying methods had significant influences on bulk density, water absorption, oil-holding capacity, and swelling capacity of sweet potato leaf powder. The highest bulk density was found in hot-air drying method and the values were in the range of 0.54 to 0.67 g/cm3. Spray-dried sweet potato leaf powder showed a higher water absorption index and oil-holding capacity, which were in the range of 13.73 to 17.40 and 3.0 to 5.0 g/g, respectively. However, the swelling capacity (only 0.58 to 3.64 mL/g) of spray-dried sweet potato leaf powder was significantly lower than that for the other two drying methods. The typical physicochemical quality evaluation indices for sweet potato leaf powder screened out by principal component analysis were oil-holding capacity, emulsifying activity, emulsion stability, and water absorption index. Xu 053601 was considered as the most suitable cultivar for preparing sweet potato leaf powder. In conclusion, spray drying was found to be the best method to prepare sweet potato leaf powder from those analyzed in this study.
