Drying Kinetics of Tomato Slices Dried by Using Solar Cabinet, Poly House Dryer and Open Sun Drying

Abstract

This study evaluated the drying performance and quality retention of tomato (Lycopersicon esculentum) slices processed using three drying techniques, namely solar cabinet drying, polyhouse drying, and conventional open sun drying. Uniformly sliced (8 mm thickness) fully ripened tomatoes of a local cultivar were pretreated with a 10% sodium chloride solution followed by 5% potassium metabisulphite (KMS) to reduce enzymatic browning and oxidative degradation prior to drying. The pretreated slices were dried under respective conditions and subsequently milled into powder using a Willey mill for physicochemical and nutritional analyses, including lycopene content, reducing sugars, ascorbic acid, total soluble solids (TSS), pH, and total carbohydrates. The results indicated significant variation in drying duration, with polyhouse drying requiring the least time (65 h), followed by solar cabinet drying (90 h), while open sun drying exhibited the longest drying period (110 h). Despite a longer drying time than polyhouse drying, solar cabinet drying resulted in superior retention of ascorbic acid, TSS, reducing sugars, and total carbohydrates, attributable to more controlled thermal conditions and reduced exposure to environmental factors. These findings demonstrate that solar cabinet drying represents an effective technological improvement over traditional open sun drying, yielding nutritionally superior and higher-quality tomato powder, thereby offering a viable and sustainable drying method for enhancing product quality, reducing post-harvest losses, and supporting food security in the processing of horticultural crops such as tomatoes and peppers.