Effects of Freeze-Drying Process on Antioxidant and Some Physical Properties of Cherry Laurel and Kiwi Fruits

Abstract

Freeze-drying is a trend method for the preservation
 of thermosensitive and nutritive food products. In this study, two different fruits,
 kiwi fruit with high ascorbic acid content and cherry laurel fruit with high phenolic
 content, were selected to study the freeze-drying effect on these compounds.
 Ascorbic acid content, total phenolic content and antioxidant capacity of kiwi
 and cherry laurel fruits were determined before and after freeze-drying
 process. Ascorbic acid content of kiwi and cherry laurel fruit were 205.14±21.33
 and 3.00±1.02
 mg/100 g dry matter, respectively. Total phenolic content of kiwi and cherry
 laurel fruits were 262.66±19.97
 and 1056.78±90.73 mg GAE/100 g dry matter, respectively. Ascorbic acid contents
 did not change, while antioxidant capacities increased by freeze-drying process
 for both fruits. The total phenolic content of cherry laurel fruits increased significantly
 after freeze-drying in contrast to the total phenolic content of kiwi fruits.
 Color values changed with freeze-drying, the lightness and yellowness values
 increased significantly for both fruits (p<0.05). The rehydration ratios of
 freeze-dried kiwi and cherry laurel fruits were found similar at 25 and 40°C. The rehydration ratio in water at 40°C increased more quickly in the beginning of
 immersion than the ratio at 25°C. The
 results of this study showed that freeze-drying method is highly recommended
 for the preservation of nutritive values of these fruits and off-season
 products.