The present study was conducted to investigate the ability of black tea theaflavins to inhibit the off-odor formation from citral under acidic aqueous conditions. Acidic buffer solutions (pH 3.0) containing citral (10 mg/L) and an inhibitor (0-5 mg/L) were stored at 40°C for 2 weeks. The formation of possible off-odorants p-cresol and p-methylacetophenone in the citral solutions was monitored by high-performance liquid chromatography. A mixture of the theaflavins showed inhibitory effects on the formation of both p-cresol and p-methylacetophenone with 50% inhibitory concentrations (IC50) of 0.18 and 0.10 mg/L, respectively. Individual theaflavins and a structurally related compound, purpurogallin, also inhibited the formation of both off-odorants, with the lowest IC50 values for theaflavin 3,3′-digallate (0.17 and 0.06 mg/L for p-cresol and p-methylacetophenone, respectively). On the other hand, a mixture of green tea catechins and its major constituent, (-)-epigallocatechin gallate, showed relatively high IC 50 values for the formation of p-methylacetophenone (1.29 and 1.28 mg/L, respectively) and showed no inhibitory effect on the formation of p-cresol. The results of the sensory evaluation showed that the off-odor intensity of the stored citral solution was significantly decreased by the addition of the theaflavin mixture at concentrations of 0.5 mg/L and above. In addition, the calculation of the odor activity values (OAVs) for the volatile compounds detected by a gas chromatographic analysis indicated that the total OAVs of the major volatile compounds in the citral solution were significantly decreased by the addition of the theaflavins.
All Science Journal Classification (ASJC) codes
- Agricultural and Biological Sciences(all)
- Black tea
- Odor activity values