The caffeine content of tea is not determined by the type of leaf alone. Here, we will introduce how it can be controlled through cultivation and processing, and most importantly, through the brewing methods you can practice at home.
The Influence of Cultivation and Processing: Harvest Time and Production Methods
The cultivation and processing steps that define a tea's flavor and aroma also affect its caffeine levels. This information is based less on national data and more on the scientific knowledge and principles from the front lines of tea production.
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Influence of Harvest Time: "Ichibancha" (First Flush) is Rich in Caffeine For the tea plant, caffeine acts as a natural defense mechanism to protect new buds from insects. Therefore, the energetic young buds of the first harvest ("Ichibancha") contain the most caffeine. Levels tend to decrease in the tougher, more mature leaves of later harvests ("Nibancha," "Bancha," etc.). This is why higher-grade Sencha is often said to have more caffeine.
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Influence of Processing (1): The "Steaming" of Sencha While Sencha can be classified as lightly steamed (Asamushi), normally steamed (Chumushi), or deeply steamed (Fukamushi), the steaming time itself does not change the caffeine content of the tea leaves. However, because the leaf structure of deep-steamed tea is finer, its components infuse more easily into water. As a result, when brewed for the same amount of time, deep-steamed tea tends to yield more caffeine.
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Influence of Processing (2): "Roasting" and "Blending" "Hojicha" and "Genmaicha" are popular for their low caffeine content. The reason lies in their processing.
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Hojicha (Roasted Green Tea): During the high-temperature roasting process, some of the caffeine in the tea leaves turns to vapor (sublimates) and is reduced.
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Genmaicha (Green Tea with Roasted Rice): By blending green tea with roasted brown rice, the relative amount of tea leaves in a serving is lower, which in turn reduces the caffeine content per cup.
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The Art of Brewing: The Final Step in Caffeine Control
This is the most important point. By making small adjustments to your brewing technique at home, you can significantly control the amount of caffeine in your cup.
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The Key is Water Temperature Caffeine has the property of dissolving more readily in hot water. Conversely, by using cooler water, you can greatly suppress the extraction of caffeine.
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For when you want a caffeine boost (before work or study): Brewing with hot water (80°C / 176°F or higher) will efficiently extract caffeine and yield a crisp, sharp flavor.
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For when you want to limit caffeine (before bed): We recommend using lukewarm water (below 70°C / 158°F) or trying "Mizudashi" (cold brewing). It is said that cold brewing can reduce the extracted caffeine to about half or even a quarter of that from a hot brew.
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The Relationship Between Umami and Caffeine Theanine, the umami component of tea, infuses slowly and thoroughly even at low temperatures. This means that brewing at a lower temperature to suppress caffeine is also the ideal method for maximizing the tea's mellow umami. The practice of brewing high-quality Gyokuro with lukewarm water below 60°C (140°F) is a piece of wisdom from our ancestors, designed to savor its supreme umami while limiting the extraction of excess caffeine.
We believe that by understanding the characteristics of each tea and by adjusting your brewing method, you can freely enjoy tea in a way that suits your body and mood. We sincerely hope this guide helps you further enjoy the profound world of Japanese tea.
