Comparative Effects of Drying on the Drying Characteristics, Product Quality and Proximate Composition of Some Selected Vegetables

This study investigated the effects of drying on the drying characteristics, product quality and proximate composition of some selected vegetables. The vegetable investigated were Ocimum gratissimum (Scent leaf), Vernonia amygdalina (Bitter leaf), Moringa oleifera and Heinsia crinite (Atama leaf). These vegetables were collected fresh, sorted, oven dried at 50^oC for 12 h and evaluated for drying kinetics, rehydration properties, proximate composition, and total chlorophyll content. The result of drying kinetics indicated that the rate of moisture loss was at its highest in the first and second hour of drying; however the moisture loss was slowed down in the subsequent drying period. The removal of moisture at the end of drying was found to be at a faster rate in the following order: bitter leaf>scent leaf>Moring oleifera leaf>atama leaf. Results of the rehydration properties showed that significantly (p<0.05) higher rehydration ratio and rehydration capacity was obtained in atama leaves (10.56 and 0.223, respectively) while Moringa oleifera recorded the lowest (10.56 and 0.097, respectively). The results revealed that the drying significantly (p<0.05) affected the proximate composition of the dried vegetables with bitter leaf having the highest ash and protein content (11.31% and 29.28%, respectively), atama had the highest fat and carbohydrate content (17.36% and 50.33%, respectively) while Moringa oleifera was highest in crude fibre (19.98%). Total chlorophyll content was higher in the dried vegetables (1.75-3.22mg/100g) than in the fresh vegetable (0.80-1.39mg/100g). In its fresh and dried forms, bitter leaf had the highest chlorophyll content (1.39 and 3.22mg/100g) while chlorophyll retention was highest in scent leaf (67.21%) after drying. This study therefore indicates that drying affects the nutritional composition and product quality of the vegetables differently and that these vegetables in its dried forms are recommended as they supply adequate nutrients.

Keywords: Bitter Leaf, Drying, Moringa oleifera, Scent leaf, atama leaf