The effect of different drying techniques and microwave finish drying on the powder properties of the red pepper powder (Capsicum annuum L.).

Abstract

The objective of this study was to investigate the effects of different drying processes (microwave, freeze, convective hot air, and vacuum drying) and microwave finish drying (FD + MD and CD + MD) on the physical and powder properties of the red pepper powder. The effect of moisture content on the powder properties and the relationship between microwave output power or drying temperature and physical and powder properties were also determined by using most common mathematical models (linear, power, logarithmic, and quadratic). Results showed that an increase in both microwave output power and temperature (for CD and VD) generally resulted in a decrease in drying time, moisture content, and chroma and an increase in bulk and tapped density values. The drying time, moisture content, and water activity values can be significantly decreased, whereas, the color values can be significantly increased by combining FD and CD with microwave finish drying (P < 0.05). The moisture content (y = - 1.94ln(x) + 7.6455, R2 = 0.9905), bulk (y = 54.224ln(x) + 153.71, R2 = 0.9705), tapped (y = 61.7ln(x) + 225.6, R2 = 0.9994) and particle densities (y = - 327.4ln(x) + 2260.5, R2 = 0.9966), and porosity (y = - 3.778ln(x) + 89.806, R2 = 0.9586) values followed a logarithmic trend depending on the increase in the convective hot air drying temperature. The inverse relationship was observed between the moisture content, bulk and tapped densities of the red pepper powders.