Relative content of gallic acid over 5-galloylquinic acid as an index for the baking intensity of oolong teas

J Food Drug Anal. 2018 Apr;26(2):609-619. doi: 10.1016/j.jfda.2017.07.015. Epub 2017 Aug 18.

Abstract

Phenolic compounds in a series of old oolong teas prepared by baking annually were monitored and compared. The results showed that the relative content of gallic acid over 5-galloylquinic acid was subsequently elevated during this preparatory process. To reveal the effect was mainly resulted from baking or aging, two sets of oolong teas were collected and examined; one set was generated from fresh oolong tea via continually daily baking and the other set was composed of aged oolong teas with no or light baking in the storage period. The relative content of gallic acid over 5-galloylquinic acid was observed to be subsequently elevated when oolong tea was continually baked at 90, 100, 110, and 120 °C for 8 h day after day. In contrast, the relative contents of gallic acid over 5-galloylquinic acid in aged oolong teas with no or light baking were found to be similar to or slightly higher than that in fresh oolong tea. The results suggest that the relative content of gallic acid over 5-galloylquinic acid seems to be a suitable index for the baking intensity of oolong tea in different preparations.

Keywords: 5-Galloylquinic acid; Aging; Baking; Gallic acid; Oolong tea.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Camellia sinensis / chemistry*
  • Cooking
  • Gallic Acid / analysis*
  • Hot Temperature
  • Phenols / analysis
  • Plant Leaves / chemistry*
  • Quinic Acid / analysis*

Substances

  • 5-galloylquinic acid
  • Phenols
  • Quinic Acid
  • Gallic Acid

Grants and funding

The work was supported by grants from the Ministry of Science and Technology, Taiwan, ROC (MOST 105-2622-8-005-002-TB1 and MOST 104-2622-B-005-005 to JTC Tzen).