READ · COMPARE · EXPLAIN
Kōshū: Fermentation using skins and maturation using lees
Here we interpret Kōshū, which has been cultivated in Yamanashi for a long time, from the perspective of training methods and winemaking. Whites, orange wine, and sur lie are compared along the winemaking process.
Questions for this course
With the same Koshu grape, what changes depending on how skins and lees are used?
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To applied practice using the material ↓
To explanation task notes ↓Koshu / Learn by grape variety
Also known as / Alternative names: Kōshū
Update date: 2026-09-23
Colored skins and white wine
Kōshū is a grape with a grayish-pink skin. It has long been cultivated in Yamanashi and used for white wine. The color of the finished wine does not depend only on the skin color. By reading whether the must is pressed to separate the juice, or whether it is fermented in contact with the skins, you can trace why different styles are produced from the same variety.
Pergola training and summer rain
Koshu traditionally shows the use of elevated pergola training, also considering adaptation to summer rain. Koshu of Japan introduces trials with vertical trellising as well as techniques for managing yields and foliage. Rather than deciding quality simply as a choice between pergola and trellis, check where the grape clusters are positioned and how rain and sunlight are managed. Training is a viticultural choice that should be read together with vineyard conditions.
Fermentation on skins and maturation on lees
Château Mercian produces both Koshu Gris de Gris, which is fermented together with grape skins and seeds, and a Sur Lie style, where the wine is aged on lees after fermentation. The former extracts components from grape skins and solids, while the latter uses yeast-derived lees for maturation. The main difference lies in what the wine is in contact with, and when this occurs. Since the two are separate processes, the existence of one cannot be determined solely from a mention of the other; always check the entire process.
What to align and what to compare.
Raw material
- Conditions to standardize
- Grayish-pink skin
- Conditions for comparison.
- Pressing and skin contact.
- Additional points to confirm
- Grape skin color and wine color.
Vineyard
- Conditions to standardize
- Yamanashi Kōshū
- Conditions for comparison.
- Pergola, vertical trellis, leaf management
- Additional points to confirm
- Responses to rain and sunlight
Winemaking
- Conditions to standardize
- The same Koshu
- Conditions for comparison.
- Timing of contact between skins and lees
- Additional points to confirm
- Clarify subject and order.
Order of reading and key points to consider in each article
0 / 4 articles completed
Next article →Progress is recorded as the completion of reading articles. This does not include completion of explanatory assignments.
- 1↗
Japan
Broaden the range of varieties from Koshu and Bailey A
Organize Kōshū and other Japanese grape varieties.
- 2↗
Japan
Yamanashi: Differentiating Koshu from the Kofu Basin
Read both the basin vineyards and the regional indication.
- 3↗
Japan
Kōshū Sur Lie: Interpreting contact with lees
Verify whether maturation on lees is used.
- 4↗
Japan
Measures for rain: canopies and vineyard drainage
Read about viticultural techniques for coping with rain.
READ · HYPOTHESIZE · RECONSIDER
Reading material on Kōshū: Fermentation using skins and maturation using lees.
In the imaginary Koshu winemaking record, differentiate contact with grape skins from contact with lees.
This is a fictitious example created for study purposes. It is not a reproduction of the methods used by any particular producer or product.
| Item | A | B |
|---|---|---|
| Grapes | Koshu | Koshu |
| Fermentation | Fermenting juice separated by pressing. | Fermenting together with the skins |
| After fermentation. | Matured with fine lees contact | Skins removed; lees treatment not described |
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Read the explanation for each question
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Which notes correspond to sur lie?
Sur lie refers to an aging process in which wine is kept in contact with its lees after fermentation. The skin fermentation of B involves different materials and timing, so cannot be described by the same term.
What is used during fermentation in B?
The table indicates fermentation of Kōshū with skin contact. This method extracts color and flavor compounds from the skins and should be distinguished from lees aging after fermentation.
Can you conclude that B does not undergo lees aging?
The table does not specify how lees are handled for B. Skin contact and lees aging are separate steps, so you cannot assume one is omitted based only on the record for the other.
Basis and sources for the exercise
Practice exercises in comparison
In the imaginary Koshu winemaking record, differentiate contact with grape skins from contact with lees.
Read examples of organizing comparisons
| Conditions for Comparison | Fermentation with the skins | Sur lie |
|---|---|---|
| What is coming into contact | Grape skins and seeds | Lees originating from yeast. |
| Main period | During alcoholic fermentation | Aging after fermentation. |
| Information for Comparison | Handling of skins and contact period | Lees handling, container, duration |
This is an organized study tool based on the designated articles for this course. You can check specific facts and sources in each article.
Explain in your own words
List what comes into contact and when in A and B, and explain what is overlooked if both are simply called 'long maceration methods'.
Check after writing
- Was a distinction made between skins and lees derived from yeast?
- Did you indicate the sequence of during and after fermentation?
- Are you supplementing undocumented processes?
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