Effects of prior freezing conditions on the performance of the freeze drying process of blueberry

Blueberry fruit contains many nutrients involved in flavor and aroma which may be reduced during storage or processing, particularly under high temperature conditions. Freeze drying process with low temperature in all processing steps is the appropriate drying method to dry blueberries. Northern highbush blueberry cultivars 'Dixi', 'Darrow', 'Elliot' and rabbiteye 'Tifblue' harvested from the University orchard during the 2015 harvest season were used as test materials. In this research the prior freezing was incorporated into a process of the freeze drying. Freezing speed in the prior freezing process was controlled by changing the temperature of a freezer tray at four different temperatures of -20, -40, -60 and -80°C. Volatile aroma compounds as measured by GC-MS from the liquid collected in a condenser trap were lost from blueberry during the sublimation process of freeze drying.