Effect of Synergistic Fermentation of Different Beneficial Microorganisms on the Aroma Substances of Pu’er Tea

Ripened Pu’er tea was made from the sun-dried leave of large-leaf tea (Camellia sinensis (Linn.) var. assamica (Masters) Kitamura) by natural fermentation, pure culture fermentation with Rhizopus arrhizus, or mixed culture fermentation with Saccharomyces cerevisiae, R. arrhizus and Aspergillus niger in proportions of 2:1:2, 2:2:2 and 2:3:2. The composition and content of aroma substances in Pu’er tea were analyzed by simultaneous distillation extraction (SDE) coupled with gas chromatography-mass spectrometry (GC-MS). The results showed that there were significant differences in the types and relative contents of aroma substances among all tea samples. The relative contents of terpenols in the three co-fermented Pu’er tea samples were higher than that in the naturally or R. arrhizus fermented ones, and had unique flowery, fruity and caramel-like aromas. The relative content of alcohols in the co-fermented Pu’er tea with yeast, R. arrhizus and A. niger in a ratio of 2:1:2 was 47.32%, which was significantly higher than that in the other samples (P < 0.05). The relative content of methoxybenzene in Pu’er tea obtained by natural fermentation and pure culture fermentation, having an aged aroma, were higher than that obtained by the three collaborative fermentation methods. The relative content of methoxybenzene in Pu’er tea fermented with pure R. arrhizus was as high as 31.24%, which was significantly higher than that obtained by the other fermentation methods (P < 0.05). Therefore, co-fermentation with beneficial microorganisms can improve the quality of Pu’er tea and endow it with unique flowery and fruity aromas.