Optimization of process conditions to improve the quality properties of healthy watermelon snacks developed by hot-air drying

Watermelon is a valuable source of nutrients and antioxidants that are beneficial for human health, but it is a seasonal and easily perishable fruit. Appropriate drying conditions should be considered to maintain the quality and nutritional attributes of watermelons after hot-air drying. This study aimed to investigate the effect of drying temperature and air velocity on some quality characteristics by response surface methodology. The drying trials were performed at temperatures of 55, 65, and 75 °C and air velocity of 1, 1.5, and 2 m/s employing a face-centered composite design. Some physical (a* value and browning index) and chemical (total polyphenols, the ferric reducing/antioxidant power, total anthocyanin, ascorbic acid, sucrose, total sugar, lycopene, total carotenoid, 5-HMF, and non-enzymatic browning) properties of dried watermelons were determined. The results indicated that the effect of drying temperature on the analyzed attributes was more significant than air velocity in general. Polynomial models with high R 2 values were generated to predict the responses. The optimum drying conditions obtained (65.425 °C and 1.025 m/s) were experimentally validated. The proposed conditions provided better preservation of the quality characteristics (physical and chemical) studied for the commercialization of dried watermelons as a snack.