Postharvest Quality Evaluation of Pineapple during Drying

Abstract

Drying is one of the most widely used preservation methods in the food industry since it enhances the shelf life of food products by prohibiting the growth of microorganisms and enzyme activity. This study aims to investigate the influence of a traditional tray dryer and a self-designed vacuum dryer at different temperatures on the quality of pineapple. Experiments with tray and vacuum drying were performed at temperatures of 50 and 60 °C. Results of each drying method in terms of processing time, final moisture content of the samples, rehydration capacity, color change, firmness, and water activity were compared and discussed. The results showed that the vacuum dryer takes less drying time to achieve moisture content lower than 0.12 g water/g of dry solid compared to the tray dryer. Furthermore, it has been observed that the samples dried in a vacuum dryer at 50 °C had better rehydration ability and retained more color and textural properties than those dried by a tray dryer at temperatures of 50 and 60 °C. Hence, vacuum drying was found to be the better condition for preserving pineapple quality at a temperature of 50 °C. At last, the microstructure of the dried samples was also analyzed by confocal laser scanning microscopy. Results showed that vacuum drying retained the microstructure of the cells. However, the cells were found to be smaller in size compared to the fresh samples. However, tray drying distorted the cell structure.