Study on the Physicochemical Properties, Antioxidant Properties and Aroma Components of Cold Brewing Green Tea in Negative Oxidation-reduction Potential Electrolyzed Water

The effects of electrolyzing water-cooled green tea with negative redox potential on the quality of tea soup was studied by comparing the bottled natural water-cooled green tea and conventional hot bubble green tea, in order to provide a new choice for the processing water of cold bubble green tea with high content of active ingredient and strong antioxidant activity. Electrolyzing drinking water by adjusting the electrolysis time to generate electrolytic water samples 1 and 2 with different negative redox potentials. The basic physicochemical indexes, main active ingredient, antioxidant activity, sensory quality and aroma components of electrolyzed water with negative redox potential, bottled natural water-cooled green tea and conventional hot bubble green tea were determined and compared by UV spectrophotometry, high performance liquid chromatography, headspace solid-phase microextraction and gas chromatography-mass spectrometry. The results showed that the pH of electrolytic water-cooled green tea soup was weak alkaline, the redox potential was negative, the content of soluble solids and the extraction rate of tea soup were significantly higher than those of bottled natural water-cooled green tea (P<0.05), and were equivalent to standard hot tea. The color of tea soup prepared by electrolyzing water with negative redox potential was yellow green and bright, and the color quality of tea soup was high. The polyphenol content of tea infusion was significantly higher than that of bottled drinking natural water cold soaking, and electrolyzed water sample 2 was significantly higher than conventional hot soaking (P<0.05), and the total amount of free amino acids was significantly higher than bottled drinking natural water cold soaking and conventional hot soaking (P<0.05), the content of caffeine was lower than the conventional hot brew, and the content of catechins was higher than that of bottled drinking natural water cold brew, except for EGCG and EGC, all higher than the conventional hot brew. The antioxidant activity of tea soup was significantly higher than that of the other two kinds of green tea soup (P<0.05). The sensory score of tea soup was the highest, and the aroma components of tea soup were the most abundant and mellow. The experiment preliminarily verified the feasibility of using the electrolyzed water with negative redox potential as the water for cold brewing green tea processing, and screened out the electrolyzed water sample 2 cold brewing green tea soup had high biochemical components, strong antioxidant activity, high sensory evaluation and lasting aroma, which was more suitable for cold brewing green tea processing.