Evaluation of Chinese tea by the electronic nose and gas chromatography–mass spectrometry: Correlation with sensory properties and classification according to grade level

Flavor profiles of high, middle and low grades of Chinese green and black teas were comparatively analyzed by electronic nose, gas chromatography–mass spectrometry (GC–MS) and quantitative descriptive analysis (QDA) in this study. Sensory analysis showed marked differences among different grades of tea, demonstrating it agreed well with the market price in tea grade classification. The high grade of tea samples got the highest score of pleasant aroma properties (pure and persistent, malty, sweet, citrus, fruity, floral flavor, refreshing, and seaweed). A total of 37 volatile compounds in three grades of green and black teas were identified and hexanal, α-terpinol, methyl salicylate, geraniol, linalool and its oxides were the most abundant compounds in both varieties of Chinese tea. Differences in the composition of volatile components from three grades were observed. In general, high grade tea had more volatiles than low grade tea. The results of electronic nose indicated that it could clearly and rapidly distinguish the difference among different grade teas. The relationship between sensory profiles, the GC–MS data and electronic nose responses of different grades of Chinese green and black teas was modeled by partial least squares regression (PLSR).