Physicochemical characteristics of osmotically dehydrated tomato (Lycopersicon esculentum) under different common drying methods

Abstract

This study investigated the effect of different common drying methods on the chemical composition of osmotically dehydrated tomato. The quality of dehydrated tomato is often poor as a result of: collapse of structure, discoloration, tough texture and loss of nutritional values. In this study, osmotic dehydration was combined with other drying methods with a view to investigating the method that will produce high quality product. Combination of sucrose and salt solution was used to soak tomato at 400 Brix for 4hours. The osmotically dehydrated samples were subjected to open air (sun), solar cabinet, hot air cabinet and oven drying methods. The proximate composition, colour and vitamin C of the dried samples were determined. The proximate composition showed that the raw tomato contained fat 1.75%, Ash 27.97%, crude fiber 0.18%, Protein 28.95% and Carbohydrate 41.15% while the Sun dried sample contained fat 1.25%, Ash 42.71%, Crude fiber 0.19%, protein 15.74% and carbohydrate 40.11%. Solar cabinet dried sample contained fat 1.29%, Ash 42.88%, crude fiber 0.26%, protein 15.78% and carbohydrate 35.79%. Hot air cabinet dried sample contained fat 1.17%, Ash 33.95%, crude fiber 0.25%, protein 14.48% and carbohydrate 1.17%. Oven dried sample contained, fat 1.15%, Ash 49.34%, crude fiber 0.26%, protein 13.22% and carbohydrate 36.03%. The vitamin C and colour measurement for raw, sun dried, solar cabinet dried, hot air cabinet dried and oven dried are 156.7 mg/100 g and 600 nm, 79.2 mg/100 g and 610 nm, 67.4 mg/100 g and 610 nm, 66.6 mg/100 g and 615 nm and 50 mg/100 g and 620 nm respectively which indicate the level of red pigmentation. Osmotically dehydrated tomato subjected to solar cabinet drying and sun drying yielded the best quality product based on
their proximate and vitamin C compositions.