Effect of Different Processing Methods on the Quality Indexes and Enzyme Activities of Rosa Crimson Glory Tea and Correlation Analysis

At present, there are some problems in rose tea on the market, such as single processing method, large loss of aroma after brewing, etc. In this study, with reference to tea processing, fresh rose (Rosa crimson glory) petals were processed into scented tea by four methods: Room temperature-drying, withering-fermentation-drying, fixation-drying and fixation-fermentation-drying respectively. The quality indexes of scented tea such as sensory quality, aroma composition, and content of active substances (total phenols, total flavonoids, and anthocyanins) were compared and analyzed. In addition, the enzymatic activities of polyphenol oxidase and peroxidase in the scented tea were determined. Besides, the correlations between the quality indexes and the activities of the two enzymes were analyzed. The results showed that the total sensory evaluation score of rose tea processed by fixation-fermentation-drying treatment was 75.00±8.30, significantly higher than that of rose tea processed by other methods (P<0.05) and it performed better in all factors of sensory quality. The content of the main aroma components, such as citronellol content, in thr rose tea produced by the fixation-drying and fixation-fermentation-drying methods were 20838.61±63.06 and 28218.71±14.95 μg/kg respectively, which was significantly higher than those obtained by withering-fermentation and room-temperature drying methods (P<0.05). In addition, the content of total phenols (184.17±2.04 mg GAE/100 g DW) and flavonoids (92.63±2.48 mg rutin equivalent/100 g DW) in rose tea processed by fixation-fermentation-drying method was significantly increased compared to other processing methods (P<0.05). However, it was unfavorable to the retention of anthocyanins when processed by withering-fermentation-drying, fixation-drying and fixation-fermentation-drying methods. The correlation between the quality indexes and the enzyme activities of the two enzymes showed that there was a negative correlation between the peroxidase enzyme activity and the aroma components of esters, aldehydes, alcohols, acids and alkanes, while there was a positive correlation between the polyphenol oxidase enzyme and the aldehyde aroma components (r=0.602). There was a negative correlation between the polyphenol oxidase enzyme activity and the content of active substances as total phenols, total flavonoids, anthocyanins, while the peroxidase enzyme was negatively correlated with the content of anthocyanins (r=0.202). The enzyme activity of the two enzymes, especially polyphenol oxygenase activity, could be effectively inhibited by fixation processing. In general, the rose tea produced by the method of fixation possessed a higher score and higher main aroma component contents. The rose tea produced by the method of fixation-fermentation-drying method had the highest content of total phenols and flavonoids. The correlation analysis between the enzyme activities and the quality indexes of rose tea showed that the quality of rose tea could be improved by regulating the enzyme activities through processing methods.