Application of microwave energy for Poly Phenol Oxidase inactivation in green tea processing

The use of microwaves for heating in food industry is known as a safe alternative. In this study, microwave energy at different times and powers for fresh green leaf enzyme inactivation in green tea production was used. In the first stage, the blanching times (30, 60, 90 and 120 s) in the highest power (900 w) of the microwave were applied on green leaves; and in the second stage different microwave powers (500, 600, 700, 800 and 900 w) in the best time of blanching were used on green leaves. Quality characteristics including total polyphenol, antioxidant activity, chlorophyll and sensory evaluation were determined. The data were analyzed in a completely randomized design with four treatments (in first part) and five treatments (in second part) in three replications. The results showed increasing the blanching time (90 and 120 s), caused increasing in antioxidant activity and improved the sensory properties of green tea. Green tea treated in 90 and 120 s blanching did not show a significant decrease in quality after one year of storage. As the oven power for green leaf blanching increased, the taste, aroma and total sensory scores of green tea clearly increased. The amount of chlorophyll, polyphenols and sensory properties such as taste, aroma and total sensory scores of green tea treated in 500 w power was less than that in other treats. Green leaf blanching in 120 s with a power of at least 700 w showed the best result in terms of quality characteristics of green tea and its storage properties.