MODELING DRYING CHARACTERISTICS OF MORINGA Moringa oleifera) AND FLUTED PUMPKIN (Telfairia occidentalis) LEAVES

Abstract

Moringa oleifera leaves and pumkin leaves have been known for their nutritive and medicinal values as almost every part of the plant can be used for food, medicine, or other beneficial applications. In this study, drying characteristics of Moringa oleifera and Pumpkin (Telfairia occidentalis) leaves were investigated using three different drying systems: Direct sun drying, Indirect Solar dryer and a Mechanical Convective Cabinet dryer (for a temperature range of 45, 55, 65 and 75°C at constant air velocity, 0.9 m/s). For the Pumpkin leaves, two forms were utilised: the whole unsliced pumpkin leaves and sliced pumpkin leaves. Proximate composition and phytochemical content of the fresh and dried samples of each system were carried out to determine the effect of the drying systems used on the quality of the materials. Results of proximate composition and phytochemical content were analysed using statistical analysis (SPSS). Thirteen (13) Mathematical models were fitted to the experimental data and the performance of these models was evaluated by comparing the coefficient of determination (R2), the Root Mean Square Error (RSME) and reduced chi-square (χ2) between the observed and predicted moisture ratio for all the conditions of drying. Also, the effective moisture diffusivity and activation energy were determined for each experimental material. Results indicated that drying took place in the falling rate period for both materials as there was only a very short or no constant rate period in the drying curves. Also, there was a reduction in drying time and an increase in drying rate as the drying air temperature increased. It was also observed that the sun dried samples dried faster than those dried under the indirect solar dryer due to a better exposure to environmental conditions. Proximate composition of Moringa oleifera and Pumpkin leaves revealed the presence of fat, crude protein, crude fibre, ash and carbohydrates in varying compositions. For both materials, fat content, crude protein, ash and carbohydrate content decreased in value as the temperature increased. Phytochemical analysis also showed the presence of tannin, phytate, flavonoids, vitamin C, oxalate, saponin and alkaloids. It was revealed that oxalate, flavonoids, tannins, Vitamin C and saponins content decreased in value as the drying air temperature increases. This was the same case for both Moringa oleifera and Pumpkin leaves. Mathematical modeling of the drying characteristics showed that Page model was the best model for sun and solar drying of Moringa oleifera, as well as for the mechanical drying of sliced pumpkin leaves at 45, 55, and 75oC. The diffusion model also proved best for mechanically dried Moringa oleifera samples at 45 and 55oC as well as sun dried unsliced pumpkin samples and mechanically dried 65oC sliced pumpkin sample. The Simplified Fick’s (SFFD) diffusion was the best model for solar drying of pumpkin (sliced and unsliced) , for sun dried sliced pumpkin sample and mechanically dried Moringa oleifera leaves at 75oC. The effective diffusivity coefficient was estimated to be between 4.63526 x 10-09 and 5.32406 × 10-9 m2/s for Moringa oleifera and 5.6685 × 10-9 and 7.0015 × 10-9 m2/s for sliced and unsliced pumpkin leaves respectively at the given temperature range. Activation energy for Moringa Oleifera, was 153.65 kJ/mol while that Pumpkin leaves gave activation energy of 37.83 kJ/mol. From this study, we discover that drying air temperature is a significant factor in drying of Moringa Oleifera and Pumpkin leaves. Also, the quality of the dried product was found to be best when the Moringa and pumpkin were dried at 55 °C. The dried vegetables can be rehydrated and used in ready to eat foods.