Comparative Effects of Oven and Microwave Drying on Nutrient Retention and Consumer Acceptability of Watermelon (Citrullus Lanatus)

Abstract

Background: Watermelon (Citrullus lanatus) is a nutrient-rich fruit with a high moisture content (~92%), making it highly perishable and prone to post-harvest losses. Preservation through drying can reduce spoilage; however, the choice of drying method and pre-treatment may impact nutrient retention and sensory quality. Methods: This study assessed the effects of oven drying at 54°C and microwave drying at 60°C on the proximate composition, mineral content (iron, calcium), vitamin retention (vitamin C, β-carotene), total soluble solids (TSS), and sensory attributes of watermelon slices, both untreated and pre-treated with ascorbic acid solution (3 g/250 ml). Analyses followed AOAC-standardized methods, while sensory evaluation was conducted by a 15-member trained panel using a 9-point hedonic scale. Results: Oven drying retained higher vitamin C (24.53 mg/g) and β-carotene (14.56 mg/g) compared to microwave drying (16.78 mg/g and 8.56 mg/g, respectively) (p < 0.05). Ascorbic acid pre-treatment improved iron retention (1.62 mg/g in oven-dried slices) but reduced vitamin stability. Sensory scores were highest for untreated oven-dried samples, with appearance (8.33), taste (7.87), and overall acceptability (8.00) outperforming other treatments. Microwave drying reduced processing time but increased TSS (88.47°Brix) and negatively affected sensory attributes. Conclusion: Oven drying without chemical pre-treatment is recommended for optimal nutrient preservation and consumer acceptability in dehydrated watermelon products.