Effect of pretreatment on physicochemical quality characteristics of a dried tomato (Lycopersicon esculentum)

Tomato is highly perishable and drying is a convenient method of extending its shelf life and minimizing postharvest loses. During drying, some nutrients may degrade and thus affect general quality characteristics of the dried tomato. The effect of pretreatment in enhancing drying and product quality of dried tomato was investigated in this study. Slices of tomato were treated by dipping in (a) A solution containing 0.5% sodium metabisulphite for 10 min and (b) 0.1% ascorbic acid + 0.1% citric acid solution for 10 min (1:1) and (c) distilled water for 10 min (control). Convection dehydration was carried out on tomato slices using an electric dehydrator at 55°C for 6 h. Pretreatment of tomato affected some quality attributes such as total solids, lycopene, dehydration ratio, rehydration ratio and colour. Pretreatment with sodium metabisulphite recorded the least lycopene degradation, highest dehydration ratio (19.40 ± 1.03) and also facilitated the drying of tomato better than the other treatments. All the pretreated dried tomato samples produced good visual and exhibited a desirable red colour (a* values ranging between 24.49 ± 0.44-28.34 ± 0.03) which is characteristic of dried tomato products. Pretreatment with sodium metabisulphite before convection drying can enhance the lycopene content which is a desirable quality attribute for dried tomato.