Drying of Capsicum annum (Kashmiri Long 1): Effect of pre-treatments and drying temperatures on quality parameters, colour and drying kinetics

Abstract

Kashmiri chillies, renowned for their vibrant red hue and distinctive flavor, offer a plethora of health benefits. Rich in capsaicin, the compound responsible for their characteristic heat, Kashmiri chillies possess potent antioxidant and anti-inflammatory properties. Consumption of these chillies has been associated with enhanced metabolism and appetite regulation, making them a valuable addition to weight management regimens. An investigation was conducted about the drying kinetics and physico-chemical composition of Kashmir Long-1 chillies in a cabinet dryer with an air velocity of 1.2m/s. The study examined temperatures of 45 °C, 55 °C, and 65 °C, revealing a notable decline in drying efficiency as temperatures increased. Among various pre-treatments, T7 (consisting of 2.5% potassium carbonate, 1% ground nut oil, 0.1% gum acacia, and 0.001% BHA per liter for 15 minutes) proved most effective in preserving capsaicin, capsanthin, and color values (L*, a*, b*, c, h, ∆E). Capsaicin content ranged from 0.615% db at 65 °C to 1.094% db at 45 °C. Notably, capsanthin retention (127.72 ASTA units) was highest when chillies were dried at 45 °C with pre-treatment T7. A positive correlation between drying air temperature and rate was observed. The decrease in moisture content from 451.572% to 47.82% db during 45 °C drying can be attributed to changes in water molecule availability, orientation, and bonding within the sample. Heat absorption initially facilitates evaporation of surface moisture, followed by diffusion-driven removal of internal moisture. Experimental data for whole chillies were fitted to three drying models, with the Page equation emerging as the most accurate predictor of moisture content.