Evaluation of the synergism among volatile compounds in Oolong tea infusion by odour threshold with sensory analysis and E-nose.

Twenty-four kinds of representative aroma compounds in Oolong tea were selected to evaluate the interactions by the variation in the threshold values of these compounds before, and after, they were mixed. Result demonstrated that the ratios of the referenced threshold values of heptanal, β-damascenone, and methional to their determined thresholds were larger, namely, 5, 3.85, and 2.5, respectively. On the other hand, the mixed compounds with similar structure and aroma mainly presented a synergistic effect and additive action. Moreover, a masking effect was found among compounds with different structures. (E)-2-hexenal was added to tea infusion at a concentration below its threshold level to investigate whether, or not, the sub-threshold compounds affected the overall odour sensation of Oolong tea by sensory analysis and electronic nose (E-nose). The result indicated that the aroma of the tea infusion with added (E)-2-hexenal had changed before, and after, they were mixed.