Boucha (Kaga boucha)
ingredient / ingredient-boucha
棒茶
Boucha (Kaga boucha) is a kind of hojicha made by roasting tea stems, drunk mainly in Kanazawa, Ishikawa Prefecture. It is also called Kaga boucha or Kanazawa boucha.
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Reading the bitterness
Boucha is a kind of hojicha made by roasting tea stems, also called Kaga boucha or Kanazawa boucha. In an aroma analysis of commercial products, pyrazines ranked among the leading aroma components. Pyrazines are described as compounds associated with roasting and roasted aromas, offering a clue for thinking about the aroma of boucha.
An analysis comparing stems and leaves from the same tea plant showed a tendency for pyrazines, geraniol, and linalool to be higher in boucha. This is a comparison of peak intensity, not a measurement of the absolute amount of the compounds. Before roasting, the stems contained more amino acids than the leaves, and the authors consider this a contributing factor in the greater formation of pyrazines through reaction with sugars.
There is an analysis showing that the tea stems used as the raw material for boucha contain about half as much tannin and caffeine as the leaves, and twice as much amino acids. Based on the low tannin content, the paper inferred that the stems have little astringency and a bland taste. Another study that examined roasted stems recorded the aroma of a medium-roast stem as "Bitter aroma, burnt roasted aroma", and rated a lightly roasted sample as "Preferable roasted aroma". This was an experiment using raw material from Mie Prefecture, not boucha itself from Ishikawa Prefecture.
Sources for this overview
Checked for this overview: Matched the AEDA analysis's ranking of aroma components, in which pyrazines ranked among the leading ones. / Matched the tendency for three compounds to be higher in boucha in the stem-versus-leaf comparison, and the limitation that this is a peak-intensity comparison. / Matched the amino-acid content of the stems before roasting and the authors' discussion of the reaction process.
Comparison of Flavor Components between Kukicha (Stalk Green Tea) and Sencha (Green Tea)
Checked for this overview: Used for the stem's tannin, caffeine, and amino-acid content and the inference of little astringency
Checked for this overview: Used for the difference in aroma description by roasting intensity (e.g., Bitter aroma) and the regional limitation of the sample
Other names: 加賀棒茶 (ja)
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Boucha (Kaga boucha) →is a type of→ Hojicha
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Composition and content (4)
Scope: Stems (for boucha) and leaves (for leaf hojicha) from the same tea plant, plus 10 commercial boucha samples and 6 leaf-hojicha samples (mean price around 500 yen/100 g).
Note: Comparison of GC-MS peak intensities, using SPME for the comparison of commercial products.
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ingredient-boucha —has_composition→ "When stems and leaves from the same tea plant were roasted separately and compared, the peak intensity of 2-ethyl-3,5-dimethylpyrazine (area ratio to the internal standard cyclohexanol) was 0.61 in boucha (stems) and 0.42 in leaf hojicha, about 1.4 times higher in boucha. Other pyrazines were also present at about 1.5 times the level in boucha. Geraniol was about 4 times higher in boucha than in leaf hojicha, and linalool, another terpene compound, was about 4 times higher as well. A comparison of 10 commercial boucha samples and 6 leaf-hojicha samples also confirmed a similar tendency for both 2-ethyl-3,5-dimethylpyrazine and geraniol to be higher in boucha."Scope: Stems and leaves from the same tea plant, before roasting.
Note: Fig. 10 compares bars in a graph. Only the ratio explicitly stated in the text (about 1.5 times) is included; no numerical values were estimated visually from the graph.
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ingredient-boucha —has_composition→ "Tea stems before roasting contained about 1.5 times more amino acids than leaves (Fig. 10). Pyrazines are known to form through Maillard reactions between amino acids and sugars. The authors consider the difference in amino-acid content a contributing factor to the greater formation of pyrazines in boucha (stems) than in leaf hojicha."Note: Based on the definition at the beginning of a paper that hojicha made by roasting stems is called 「棒茶」 (in translation: "Boucha").
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ingredient-boucha —is_a_type_of→ ingredient-hojichaScope: Commercial stem tea (1991, a commercial product at 300 yen per 100 g) compared against mid-grade sencha as a control (500 yen for the same amount); comparison of taste components by 13C-NMR
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ingredient-boucha —has_composition→ "The tea stems used as boucha material contain about half the tannin and caffeine of leaves, while containing twice the amino acids. Because the stems are low in tannin, it was inferred that they are lacking in astringency and that the taste becomes plain."Sensory (2)
Scope: Commercial boucha collected from Japanese-tea specialty shops in Ishikawa Prefecture.
Note: Aroma adsorption with a PDMS-coated stir bar, followed by GC-MS/AEDA analysis; FD factors were determined by sniffing the odor.
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ingredient-boucha —has_sensory_attribute→ "An aroma analysis of commercially sold boucha using GC-MS and AEDA (Aroma Extract Dilution Analysis) found that 2-ethyl-3,5-dimethylpyrazine had the highest FD factor (4096), an indicator of aroma strength defined as the greatest dilution at which AEDA can still detect the aroma. It was followed by 2-ethyl-3,6-dimethylpyrazine (1024), 2,3,5-trimethylpyrazine (256), geraniol (256), linalool (64), and furaneol (64). Pyrazines are described as associated with roasted aromas, geraniol and linalool with floral aromas, and furaneol with caramel aroma."Scope: Ooishida stems from Mizusawa, Mie Prefecture, roasted with a Morita-type automatic continuous hojicha roaster; sample descriptions from Table I
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ingredient-boucha —has_sensory_attribute→ "A medium-roast sample of ooishida stems from Mizusawa, Mie Prefecture, roasted at 150°C for 12 minutes, was described in the paper's aroma evaluation as "Bitter aroma, burnt roasted aroma". A light-roast sample of the same material roasted at 130°C for 10 minutes was evaluated as "Preferable roasted aroma", and the crude tea (aracha) before roasting was "Fresh greenish, toasted laver-like"."Culture (1)
Scope: Kanazawa, Ishikawa Prefecture.
Note: This historical account is based on the authors’ reference to Kiroku Yonezawa, 『加賀茶業の流れ』 (in translation: "The Course of Kaga Tea Production"), 1976, Hokkoku Publishing. The primary source itself was not checked in this investigation; the account is secondhand.
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ingredient-boucha —has_historical_origin→ "Boucha is described as originating around Meiji 35, when Hayashiya Shinbee of Kanazawa studied how to use stems sorted out during the finishing of crude tea and conceived of roasting and selling these stems, which gave a weak infusion and little yield. In Shōwa 58, Maruhachi Tea Factory Co., Ltd. is described as having presented boucha to the Shōwa Emperor; this is described as prompting the sale of premium boucha."