Black and green tea decontamination by cold plasma

Abstract

This experimental study is the first study conducted to black tea and green tea decontamination by cold atmospheric pressure plasma jet. This study shows that the plasma jet system is effective in inactivation of the pathogenic microorganisms of black and green tea and the inactivation of the considered strains were greatly affected by treatment time, initial concentration and kind of microorganisms. Treatment of 3 and 5 min led to complete inactivation of E. coli and coliform cells on black tea and complete decontamination of mold and yeast was achieved after 7 min plasma jet treatment time while complete reduction of E. coli and coliform cells of green tea were achieved after 4 and 5 min cold plasma treatment, respectively. Yeast and mold were completely inactivated after 7 min cold plasma treatment. In order to determine quality changes of tea samples during plasma treatment, the effect of plasma jet on caffeine, color and total phenolic content of black and green tea were evaluated. There were no significant changes in caffeine of both tea samples after 7 min plasma jet treatment. The initial total phenolic content of black tea and green tea was 10.84 and 14.94 g GAE/100 g, respectively. In both tea samples, total phenolic content was slightly increased after 5 min plasma treatment. In both tea samples 7 min plasma treatment had no significant effect in the L* (darkness to lightness), a* (green to red) and b* (yellow to blue) value of tea samples.