Researchers at the Nagoya Institute of Technology have identified that the type of glaze used on ceramic tea sets plays a critical role in maintaining the levels of catechin flavonoids in tea.
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Ceramic glazes have a noticeable effect on reducing catechin levels, which in turn modifies the tea’s taste, scent, and potential health advantages.
Since its initial introduction as a therapeutic beverage around 2700 B.C., tea has ascended to become one of the most widely consumed drinks globally. One contributing factor to its widespread appeal is its rich composition of flavonoids and polyphenols, which endow the tea with antioxidant properties, as well as distinctive flavor and aroma. These bioactive compounds are drawn out from the tea leaves during the brewing process, and their presence can be affected by various elements, including the water’s temperature, the duration of brewing, and the materials used to make the tea preparation containers.
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Recent Academic Discoveries
A recent study by the Nagoya Institute of Technology (NITech) in Japan disclosed that the selection of ceramic glaze is crucial for the retention of catechin flavonoids in tea. The study, recently published in the journal Scientific Reports, was conducted by Associate Professor Takashi Shirai, along with Dr. Yunzi Xin, Mr. Sota Shido, and Dr. Kunihiko Kato of NITech’s Advanced Ceramics Research Center. They investigated the effects of four prevalent Japanese commercial glazes—Oribe, Namako, Irabo, and Toumei—on catechin concentrations, the primary flavonoid in green tea.
Ceramic glazes tend to reduce catechins in tea through an oxidation process, which subsequently alters the tea’s flavor, aroma, and health-promoting properties. Credit: Dr. Takashi Shirai, NITech, Japan.
Characteristics and Composition of Ceramic Glazes
While the primary constituents of ceramic glazes are feldspar minerals, including silicon, aluminum, sodium, and calcium oxides, they also include distinct metal oxides that give each ceramic piece its individual look and texture. For instance, Oribe glaze mainly contains copper (Cu) oxides that give it a striking green hue, whereas Namako glaze consists of cobalt (Co) oxides resulting in a dark blue shade. Irabo glaze includes iron (Fe) oxides providing orange tones, and Toumei glaze features a high titanium (Ti) content, rendering a transparent finish.
Research Methodology and Observations
To evaluate the glazes’ impact on catechin levels, the researchers prepared a green tea brew using ion-exchanged water heated to 80°C (176°F) and let it steep for three minutes. Following the removal of tea leaves, the remaining liquid was mixed with glaze powders adhered to ceramic tiles. This mixture was left to react for six hours before the glaze powder was eliminated via centrifugation and filtration.
The scientists noted that the original tea solution possessed a vivid yellow color, which altered to a brownish-yellow hue after six hours. Conversely, teas mixed with different glazes changed to darker shades of black or brown. In essence, the degree of color transformation was notably dependent on the glaze type utilized.
In addition, the researchers observed a selective decrease in altered catechins. Teas mixed with Oribe, Namako, and Irabo glazes displayed markedly lower concentrations of specific catechins, while Toumei glaze affected only one particular catechin. This reduction can be attributed to the catechins undergoing an oxidation process, resulting in the formation of brown thearubigins and reddish-orange theaflavins and their oxide pigments.
Scientific Interpretation and Implications
Dr. Shirai elaborates that metal oxides in the glazes act as Lewis acid catalysts, accelerating the oxidation of catechin molecules into ortho-quinones, which then further react to form thearubigins and/or theaflavins. “Interestingly, these are the primary components of fermented teas like black tea, implying that green tea could transform into black tea when brewed with specific ceramic sets,” he said.
To conclude, this research underscores the significant impact of ceramic glaze selection on the levels of beneficial compounds such as catechins in tea. “Understanding the specific roles of ceramic glazes in catechin degradation not only offers valuable insights for material design and development but also has broader implications for daily tea consumption and long-term health,” Dr. Shirai states.
Reference
The study titled “Glazes Induced Degradation of Tea Catechins,” authored by Yunzi Xin, Sota Shido, Kunihiko Kato, and Takashi Shirai, was published on June 28, 2023, in Scientific Reports. DOI: 10.1038/s41598-023-37480-8
Acknowledgments are extended to Mizuno Kagaku Kogyo Co., Ltd for providing the ceramic glazes used in the study.
Frequently Asked Questions (FAQs) about Ceramic Glaze and Tea Quality
What is the main focus of the research conducted by the Nagoya Institute of Technology?
The main focus of the research is to explore how the type of ceramic glaze used on tea sets influences the retention of catechin flavonoids in tea. This, in turn, affects the tea’s taste, aroma, and potential health benefits.
Who conducted the research and where was it published?
The research was conducted by a team led by Associate Professor Takashi Shirai at the Nagoya Institute of Technology in Japan. It was published in the journal Scientific Reports.
What are catechin flavonoids and why are they important?
Catechin flavonoids are bioactive compounds primarily found in green tea. They contribute to the antioxidant properties, flavor, and aroma of the tea and offer various potential health benefits.
How does ceramic glaze affect catechin levels in tea?
Ceramic glazes, depending on their chemical composition, can significantly reduce catechin levels through an oxidation process. This alters the tea’s flavor, aroma, and potential health benefits.
What types of ceramic glazes were examined in the study?
The study examined four prevalent Japanese commercial glazes: Oribe, Namako, Irabo, and Toumei. Each has a unique chemical composition that affects catechin levels in different ways.
What was the methodology used in the study?
The researchers brewed green tea using ion-exchanged water at 80°C for three minutes. They then mixed the liquid with glaze powders coated on ceramic tiles and allowed the mixture to react for six hours before conducting analysis.
What are the broader implications of the study’s findings?
The findings highlight that the choice of ceramic glaze can have far-reaching effects on the nutritional and sensory quality of tea. The research not only offers insights for material design but also has implications for daily tea consumption and long-term health.
Who provided the ceramic glazes used in the research?
The ceramic glazes used in the research were provided by Mizuno Kagaku Kogyo Co., Ltd.
More about Ceramic Glaze and Tea Quality
- Nagoya Institute of Technology Official Website
- Scientific Reports Journal
- Overview of Catechins in Green Tea
- Health Benefits of Flavonoids
- Mizuno Kagaku Kogyo Co., Ltd Official Website
- Chemistry of Ceramic Glazes
- Impact of Brewing Parameters on Tea Quality
7 comments
Well, what’s next? Is my teaspoon going to change the tea as well? But seriously, good to know. Science finds a way to surprise us every day.
whoa, so my Oribe-glazed set is messing with my green tea? Gotta reconsider my tea rituals now, man.
Wow, never thought my teacup’s glaze could actually affect the tea’s taste and health benefits. Science is amazing!
I knew there was a reason my tea tasted different at home compared to when I drink it at my grandma’s! she’s got those old-school ceramic sets.
This is eye-opening! I am definitely going to pay attention to this when buying tea sets. gotta read that scientific report tho.
All these years we’ve been focussed on the type of tea leaves, and it turns out the ceramic plays a role too. Mind-blowing.
This is so interesting. i always thought the ceramic was just for aesthetics. Will definitely think twice before buying my next tea set.