Mathematical Modeling of Thin-Layer Pineapple Drying

Abstract

The drying kinetics of pineapple was studied, and the model that best describes it was selected. Pineapple slices were dried in a hot-air oven at temperatures of 50, 60 and 70C; microwave power levels of 385, 540 and 700 W, respectively; and under direct sunlight. Drying time decreased with increase in drying temperature and power level. Drying took place entirely in the falling rate-drying period. Seven mathematical models were fitted into the experimental data. The goodness of fit was determined using the coefficient of determination (R2), reduced chi-square (χ2), root mean square error and sum square error. The two-term, parabolic and Page model best explained the hot-air, microwave and sun-drying behavior of the pineapple. The effective moisture diffusivity increased from 6.89 × 10−10 to 5.1 × 10−08 m2/s while the activation energy was 12.46 KJ/mol for oven drying and 1.54 W/g for microwave drying. Practical Applications Pineapple as a fruit is a very rich source of minerals and vitamins including potassium, manganese, copper, magnesium, vitamin C and B6, thiamine, foliate, and also dietary fiber. These mineral and vitamins are essential for proper human growth and development especially for people who live on low income in tropical developing countries. The high moisture content of pineapple, which makes it highly perishable, and its abundance during periods of harvest, gives rise to postharvest losses with attendant reduction in the availability of its minerals and vitamins. Drying, a common preservative method, can be used to reduce these postharvest losses and thus make shelf-stable products last longer. The knowledge of the drying kinetics and subsequently the selection of an appropriate thin-layer drying model can be used to predict drying times and subsequently optimize the drying process for greater efficiency.