Journal of the Turkish Chemical Society Section B: Chemical Engineering (May 2020)
DRYING AND VITAMIN C LOSSES OF PINEAPPLE, KIWI AND AVOCADO FRUITS
Abstract
In this study, kiwi, pineapple and avocado fruits were dried at different temperatures and different types of dryers and Vitamin C detection was performed prior to and after drying. In order to determine the impact of the geometric shape of the fruit on drying, drying experiments were performed using fruits cut in cubic (1x1x1 cm), rectangular prism (1×1×2.5 cm) and spherical (1 cm diameter) shapes. The drying behaviours of 3 different fruits have been observed in tray dryer setting at 1.5 m/s air velocity, 45oC and 55oC temperature and infrared dryer. An examination of the data obtained at the end of the drying procedures, at 55°C drying temperature, drying occurred without any change in the colour of samples. In the experiments made for pineapple, it has been observed that drying took an average of 420 minutes, that the velocity of moisture loss was highest with cubic shape, followed by rectangular and spherical shapes; as for the experiments made with kiwi, it has been observed that drying took 360 minutes on average and the velocity of moisture loss was highest with cubic shape, followed by rectangular and spherical shapes. When it comes to avocado fruit, the drying took 400 minutes on average and its geometrical behaviour is similar to the other fruits. The effective parameter for fruits both in straight flow and in infrared drying is heat. The drying periods of pineapple, kiwi, and avocado in infrared dryer are 400, 240 and 390 minutes, respectively. Among the examined fruits, pineapple and kiwi are rich in vitamin C. At the end of the conducted experiments, ascorbic acid amount has been found as 485, 1002 and 75 mg/kg, respectively. After the drying procedure, vitamin C values were detected as 187, 25.9 and 385,4 mg/kg. These results show that 60-65% of vitamin C is lost during drying procedure. Page, Henderson & Pabis and Logarithmic thin layer drying models, available in the literature were used to evaluate the experimental data. All the models were compared according to statistical parameters; i.e. model efficiency (R2), chi-square (χ2) and root mean square error (RMSE). It was observed that Modified Page model among the models used is best mathematical model represented the drying behavior of tropical fruits.
