Chemical, Sensory and Microbiological Properties of Fleshy Tomatoes, Orange-fleshed, and Sweet Potatoes dried by Different Techniques

Fresh tomatoes and sweet potatoes are highly perishable and have a relatively short shelf life due to their high moisture content, causing a great loss during transportation, distribution, and storage. Therefore, the aim of this study was to evaluate the effect of different drying techniques on the chemical composition, sensory properties and microbiological quality of dried fleshy tomatoes and orange-fleshed sweet potatoes. The raw materials were prepared and cut into slices with thicknesses of 7±2 and 5±2 mm, respectively. Three drying techniques, namely open sun-drying, conventional hot-air drying (50±2°C) and swell-drying were adopted in this study. The conditions of the treatment by instant controlled pressure drop (DIC) were saturated steam pressure of 0.4 MPa and processing time of 15 s. The obtained results showed that the chemical composition, the sensory properties and the microbiological quality mainly depended on the drying technique used as well as the drying conditions applied. The drying of Tomato and sweet potato by DIC results in better retention of phenolics (56.49 ± 0.83and 109.23 ± 5.20mg/100 g db), antioxidant activity (101.5 ± 1.32 and87.59± 2.02 %) and Vit C (21.293 ± 0.04 and 17.67 ± 0.18 mg/100 g db) , lycopene(52.04 ± 1.60),and Beta-carotene(52.31 ± 0.87 ) respectively . Swell-dried fleshy tomatoes and orange-fleshed sweet potatoes had the highest overall acceptability with sensory characteristics superior to those of sun-dried and conventionally hot-air-dried products. Besides, swell-drying significantly inactivated or destroyed all The microorganisms studied showed no growth of total bacteria, fungi and yeasts, coliforms, E. coli and total mesophilic. Similarly, the conventional hot-air drying caused decrease in value observed, in total bacterial, fungi and yeasts, coliforms and total mesophilic were 0.4×102 cfu/g 0.5×10 ˡ cfu/g , Nd and 0.1 ×10 ˡ cfu/g, and 6.5 ×10 cfu/g , 8cfu/g ,10 cfu/g and 12 cfu /g respectively for dried fleshy tomatoes and orange-fleshed sweet potatoes.