Determination of drying characteristics and shelf life of organic eggplant and zucchini in different drying conditions

In doctoral thesis study, organic eggplant and zucchini samples were dried by three different drying methods consisting of sun drying, convective drying and infrared assisted convective drying. A drying system consisting of solar collectors and carbon fiber IR (infrared) heaters was used for convective drying and infrared assisted convective drying processes. Drying experiments in dryers were carried out at air velocity of 5 m/s and three different drying temperatures (40, 50, 60 °C). Drying kinetics, specific energy consumption, coefficient of shrinkage, ratio of rehydration, color parameters, chemical and textural properties of eggplant and zucchini samples dried were examined. During the drying processes, drying time of the samples showed reduction with increasing air temperature. As a result of analyses, it was determined that the highest loss of ascorbic acid was in the eggplant and zucchini samples dried at 60 °C. The biggest total color difference was observed in samples dried by sun drying. The lowest specific energy consumption of eggplant and zucchini samples were found during infrared assisted convective drying at 40°C. Using of convective drying method at temperature of 40°C in drying of eggplant samples and drying with infrared assisted convective drying method which carbon fiber infrared heaters was used at temperature of 40°C of zucchini samples gave the best results. Therefore, convective drying method carried out at 40°C and infrared assisted convective drying method carried out at 40°C were determined as optimum drying methods for eggplant and zucchini samples. Eggplant and zucchini samples dried by optimum methods determined were packaged in modified and normal atmosphere and stored for six months. As a result of analyses carried out during storage, it was determined that there was not a significant change in quality properties of eggplant samples, however apparent loss of quality occurred in zucchini samples packaged in normal atmosphere after 150 days of storage. It was concluded that after drying eggplant samples could be stored in normal atmosphere for six months, however zucchini samples need to be stored in modified atmosphere absolutely for the same time.