Glazes induced degradation of tea catechins

Area of Science:

• Materials Science
• Food Chemistry
• Analytical Chemistry

Background:

• Tea catechins are key antioxidants with health benefits.
• Ceramic glazes are commonly used for tea-ware.
• The interaction between tea catechins and glazes is not well understood.

Purpose of the Study:

• To investigate the degradation of tea catechins on various commercial Japanese glazes.
• To understand the role of glaze composition, specifically metal oxides, in catechin degradation.
• To identify the degradation products and their relationship to glaze properties.

Main Methods:

• Four types of Japanese commercial glaze powders (Oribe, Namako, Irabo, Toumei) were prepared and deposited on ceramic tiles.
• Green tea solution was prepared at 80°C to mimic daily tea drinking conditions.
• Degradation of tea catechins (epigallocatechin, epicatechin, epigallocatechin gallate, epicatechin gallate) was analyzed in the presence of different glazes.

Main Results:

• Glaze composition significantly influences tea catechin degradation.
• Glazes containing Fe, Cu, or Mg oxides promoted the degradation of most tea catechins.
• A Ti-oxide-containing glaze selectively degraded epigallocatechin gallate.
• Degradation resulted in the formation of colored pigments, presumed to be oxytheotannins, theaflavins, and thearubigins.

Conclusions:

• The chemical structure of glazes, particularly the presence of specific metal oxides, dictates the degradation pathways of tea catechins.
• The formation of colored pigments is a glaze-dependent phenomenon.
• Understanding these interactions is crucial for designing functional ceramic materials and has implications for tea consumption and health.