Effect of pulp layer thickness and drying temperature on the drying kinetics and physicochemical qualityty of tree tomato (Solanum betaceum) powder
Document Type : Original research
Authors
1 Department of Food Science, Nutrition, and Technology, University of Nairobi, Kenya
2 Department of Environmental and Biosystems Engineering, University of Nairobi, Kenya
Abstract
Tree tomato fruits are seasonal and highly nutritious; however, much of the perishable produce is for fresh consumption due to poor preservation techniques. There are no studies that have been conducted on the drying kinetics of Tree tomato pulp. Four different pulp layer thicknesses (2, 4, 6, and 8 mm) were dried using a convective oven at air velocity of 15 m/s 40°C, 50°C, and 60°C and then ground into powder. The quality of the powder, drying curves, and the best fit drying kinetic model to predict the drying behavior were determined. Drying curves across the different temperatures demonstrated that higher temperatures accelerated the drying process for all thicknesses. At 60°C, materials across all thicknesses showed a rapid reduction in moisture ratio (MR), indicating a faster moisture removal rate. Thicker samples had notably higher MRs across all time points than thinner samples, signifying slower drying rates. The inverse relationship between thickness and drying rate was attributed to increased resistance to moisture diffusion in thicker layers, that slowed the internal water movement to the surface of the materials, decreasing the overall drying rate. Water activity for the dried samples was below 0.6, and this showed the product was microbiologically and chemically stable. There was significant difference for vitamin C, Total phenols and hygroscopicity across the drying temperatures (p < 0.05). Samples dried at a temperature of 60°C recorded higher Total Phenols, while the hygroscopicity decreased with increase in temperature. Lower values of vitamin C were recorded at lower drying temperatures.
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