Modelling the Sorption Kinetics and Drying Characteristics of Moringa Leaf Powder Under Different Drying Conditions

Moringa oleifera leaf powder is a nutritionally dense product used in food fortification and dietary supplementation applications across Nigeria, but inadequate drying protocols contribute to product quality variability and nutrient degradation. A comprehensive understanding of sorption kinetics and drying characteristics under different conditions is essential for developing robust industrial drying protocols. This study characterises the drying kinetics of Moringa leaves from plantations in Kogi State (North Central) under forced-air convective drying at 40, 50, and 60 degrees Celsius, and models the moisture sorption behaviour of the resulting powder. Drying kinetics were modelled using the Page, Modified Page, Two-term, and Midilli-Kucuk models, with model selection based on chi-square and root mean square error criteria. Effective moisture diffusivity and activation energy were calculated. Colour (Hunter Lab), chlorophyll content, total phenolic content, vitamin C, and antioxidant activity were measured at each drying temperature to evaluate quality implications. Moisture sorption isotherms of the dried powder were determined at 25, 35, and 45 degrees Celsius using the static gravimetric method, and the Guggenheim-Anderson-De Boer model was fitted. Results showed the Midilli-Kucuk model provided the best fit for all temperatures. Effective moisture diffusivity ranged from 1.8 to 3.9 times 10 to the negative 10 m squared per second. Drying at 50 degrees Celsius balanced drying efficiency with quality retention. The monolayer moisture content was 3.8 percent at 25 degrees Celsius. The study contributes to the food drying engineering literature for African leafy vegetables. Keywords: drying kinetics, Moringa, sorption isotherm, moisture diffusivity, modelling