Effects of γ-radiation on microbial load and antioxidant proprieties in green tea irradiated with different water activities

• Higher the Aw, lower is the radiation dose to archive microbiology safety.
• The doses up to 10.0 kGy had no effect on antioxidant capacity in all Aw used.
• The recommended dose to irradiated green tea is 5.0 kGy.

The aim of this paper is to study the effect of gamma radiation on green tea irradiated with different water activities. The green tea samples had their Aw adjusted to three values (0.93, 0.65, and 0.17) and were irradiated in 60Co source at doses of 0, 1.0, 1.5, 2.0, 2.5, 5.0, 7.5, and 10.0 kGy. The methods used were: microbiology, total phenolic compounds quantification, antioxidant activity by ORAC, and quantification of the main antioxidants. It was observed that the greater the amount of free water present in the samples, lower was the dose to achieve microbiological control. Despite the irradiation with 5.0 kGy with high water activity has a small decrease in phenolic compounds and in some catechins content, this condition is recommended once was the dose to ensure microbiological safety without interfering in the main catechins and the antioxidant activity.