Comparison of Physicochemical Properties of Spinach Powder Using Different Drying Methods
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Abstract:
Spinach powder was prepared by hot air drying, solar drying, vacuum freeze drying and spray drying. The effects of different drying methods on the color, antioxidant activity, microstructure and other physicochemical properties of spinach powder were investigated. The results showed that the L* value of spray drying was 33.28 and the a* value was -5.86, which had little effect on the color of spinach powder. Compared with the fresh control, the contents of chlorophyll ascorbic acid total phenols and total flavonoids and antioxidant activity of spinach powder prepared by four drying methods were decreased, and the four drying methods had a greater effect on the antioxidant activity of spinach powder, spray drying had the highest antioxidant activity, and hot air drying had the lowest antioxidant activity. Correlation analysis showed that the total phenols, flavonoids and ascorbic acid of spinach powder were significantly positively correlated with their antioxidant activity (p<0.05). Through particle size distribution analyzer and SEM analysis, the median particle size DX(50) of spinach powder prepared by spray drying decreased to 17.76 μm, the specific surface area increased to 228.3 m2/kg, and the span value decreased to 2.87. Spinach powder was a short round rod-shaped or spherical, the particles were small and evenly distributed, part of the surface was round, the cell structure was better maintained compared with the other three drying methods. Based on the comprehensive analysis, spray drying was the best drying method for preparing spinach powder, which was more suitable for industrial production of spinach powder with high antioxidant activity, and provided scientific basis for the deep processing of spinach powder products.