are antioxidants that are found in tea. These antioxidants are beneficial for human health, as they can help reduce the risk of cardiovascular disease, cancer, and other illnesses. Ceramic tea sets can retain the antioxidants in tea longer than other types of tea sets, making them a healthier choice for tea drinkers.
These valuable compounds are extracted from tea leaves during brewing, and their presence can be influenced by various factors, including water temperature, brewing duration, and the materials used in tea preparation vessels (1✔ ✔Trusted Source
Glazes induced degradation of tea catechins
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).
Role of Ceramic Glazes in Catechin Retention
Recent research conducted by scientists at the Nagoya Institute of Technology (NITech) in Japan has shed light on a previously unexplored aspect of tea preparation: the role of ceramic glazes in catechin flavonoid retention. Published online in the journal Scientific Reports on June 28, 2023, this study, led by Associate Professor Takashi Shirai and his team, including Dr. Yunzi Xin, Mr. Sota Shido, and Dr. Kunihiko Kato from NITech’s Advanced Ceramics Research Center, delves into how four distinct Japanese commercial glazesOribe, Namako, Irabo, and Toumeiaffect the levels of catechins, the most abundant flavonoid present in green tea.
Glaze and its Unique Characteristics
Ceramic glazes primarily consist of feldspar minerals, encompassing silicon, aluminum, sodium, and calcium oxides. However, they also incorporate specific metal oxide species that impart distinctive appearances and textures to the ceramic vessels
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Oribe glaze, for instance, is rich in copper (Cu) oxides, lending it a vibrant green hue, while Namako glaze features cobalt (Co) oxides, resulting in a deep blue finish. Irabo glaze, with its iron (Fe) oxides, creates orange tones, while Toumei glaze boasts a high titanium (Ti) content, offering a transparent appearance.
Uncovering the Impact of Glazes on Tea Catechins
To investigate the influence of glaze types on tea catechins, the researchers initiated a green tea solution brewed with ion-exchanged water at 80°C, steeping for three minutes.
After separating the tea leaves, they mixed the supernatant with glaze powders applied to ceramic tiles. The glaze-tea mixture underwent a six-hour reaction period, followed by the removal of glaze powder via centrifugation and filtration.
The results were striking. While the initial tea solution displayed a bright yellow color, six hours of degradation transformed it into a yellowish-brown hue. Notably, the color change extent varied significantly based on the type of glaze used.
In addition to the observable color shifts, the researchers identified a selective reduction in altered catechins within the tea.
Tea solutions combined with Oribe, Namako, and Irabo glazes exhibited notably lower concentrations of epicatechin, epicatechin gallate, epigallocatechin, and epigallocatechin gallate. In contrast, Toumei glaze led to the selective degradation of epigallocatechin gallate. This reduction in catechin concentration and the ensuing color alteration stemmed from the catechins’ oxidation process, which generated brownish thearubigins and reddish-orange theaflavin and its oxide pigments.
Boost your brew by Ceramic Glazing
Dr. Shirai explains, “During the degradation process, Cu-, Co-, Fe-, and Ti-oxides in glaze powders can act as a Lewis acid catalyst and promote the oxidation of catechin molecules to ortho-quinones, followed by further reaction to form thearubigins and/or theaflavin and its oxides.
Another oxidation route is through the polymerization of intermediate free radical catechins. It is very interesting that thearubigins and theaflavins are the main components of fermented tea like black tea. In other words, green tea brewed by specific ceramic tea sets can be turned into black tea.”
This research underscores the crucial role of glaze materials used in ceramic tea sets in shaping the concentration of valuable compounds like catechins in tea. This discovery not only provides essential insights for the design and development of functional materials but also carries implications for daily tea consumption and long-term health outcomes.
Dr. Shirai concludes, “The specific function of glazes on the degradation of catechins not only provides principal information for the design and development of functional materials but can also impact daily tea drinking and long-term human health-related issues.”
Reference :
- Glazes induced degradation of tea catechins – (https:www.nature.com/articles/s41598-023-37480-8.epdf)
Source: Medindia
