Analysis on the Difference of Quality and Mineral Elements Among Jinmudan Oolong Tea

The sensory evaluation scores, quality indexes (tea polyphenols, caffeine, 8 catechins, soluble sugars, free amino acids, theanine, water extracts and total flavonoids) and 8 mineral elements of different grades of Jinmudan Oolong tea were determined. The results showed that the higher the grade, the higher the water extract content of Jinmudan Oolong tea, and the water extract content of Grand Prize was 1.07% and 1.75% higher than that of first prize and quality prize, respectively, and the differences all reached a significant level (P<0.05). Caffeine, soluble sugar and total flavonoid contents were all significantly higher for low-grade Jinmudan Oolong tea than high-grade (P<0.05). There was no significant difference in tea polyphenol content among the three levels (P>0.05). The ratio of phenol to ammonia was significantly lower in the grand prize than in the first prize and the quality prize (P<0.05). The theanine content was significantly lower in the quality award than in the grand prize and the first prize (P<0.05). Linear regression analysis showed that free amino acids and total flavonoids were significantly negatively correlated with the evaluation score (P<0.05), soluble sugar was significantly negatively correlated with the evaluation score (P<0.01), while water extracts was significantly positively correlated with the evaluation score (P<0.01). There was no significant difference between most mineral elements of different grades of Jinmudan Oolong tea, except for Mn and Fe (P>0.05). The restricted principal coordinates analysis showed that the quality indexes combined with restricted principal coordinates analysis could well distinguish the grade differences of Jinmudan Oolong tea with an R value of 1.00. However, the mineral elements combined with restricted principal coordinates analysis did not well distinguish the quality differences of different grades of Jinmudan Oolong tea. These results could provide a certain reference for the quality judgment of Jinmudan Oolong tea.