QUALITY And shelf life evaluation of instant green tea powder and green tea GRANULES DURING STORAGE

Since  a considerable lapse of time passes before the tea arrives at the blender, packer and consumer, it has to be stored and dispatched under conditions that leave their keeping qualities unimpaired. The present study was carried out with an objective of determining the various changes taking place during accelerated storage conditions for instant green tea powder and green tea granules and also to determine the shelf life of these products. Instant green tea              powder (IT) prepared by freeze drying of the expressed juice from fresh tea shoots and tea                granules (TG) obtained from air drying of pressed leaf residue after juice extraction were                  subjected to accelerated storage (90 + 1% RH and 38 + 2°C) for 90 days. The results showed that moisture content of IT after 70 days of storage was 10.5% (db) and the same for TG after 90 days was 13.4% (db). The water activity increased from 0.354 to 0.495 for IT and from 0.33 to 0.67 for TG, during 90 days of storage. Total polyphenols and caffeine contents decreased significantly during the storage for both the products. Color of brew changed from yellowish green to brownish tinge. Shelf life was also determined theoretically based on the initial and critical moisture contents and the values so obtained were 74 days for IT and 96 days for TG.