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WSET 3 -saké > chapter 10: Water & Yeast > Flashcards

chapter 10: Water & Yeast Flashcards

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1
Q

Was access to good quality water a problem in Japan?

A

No, enough rainfall

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2
Q

Which sources of water can be used for sake?

A

-subsoil sources
-filtered tap water (for consistency)

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3
Q

There are strict limits on 2 things in water, name them

A

-on the permitted levels of organic substances
-level of iron (way less than permitted in tap water)

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4
Q

What happens if the water contains too much iron for sake?

A

-reddish brown colour
-spoils aroma and taste

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5
Q

Water hardness and softness refers to…

A

Level of calcium and magnesium dissolved in the water, not really a defined charateristic of water when discussing sake

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6
Q

Why is magnesium in water important?

A

-Enhances the metabolism of yeast
-also: potassium and phosphorus aid the healthy growth of yeast and koji mould

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7
Q

Why was mineral rich water preferred which was high in yeast nutrients, magnesium, potassium and phosphorus?

A

-for a fast, stable fermentation
-less risk that fermentation becomes contaminated or stopped as a result of weak of starving yeast

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8
Q

Where can mineral rich water be found?

A

-Miya-Mizu water of the Nada area near Kobe (Hyogo prefacture)
-due to this, this area largest producer of sake

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9
Q

Is mineral rich water good for ginjo style?

A

-No not really, restricts the floral ginjo aromas, leading to more restrained and drier styles of sake

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10
Q

Where can lower mineral content sources of water be found? what does this mean?

A

-Fushimi water near Kyoto
-less vigorous fermentations and softer style of Kyoto sake’s

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11
Q

How is it possible to have a successful fermentation with water which has a low mineral content?

A

-Because magnesium,potassium and phosphorus are also present in rice, sufficient enough levels to meet the nutrients that yeast and koji mould need

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12
Q

When are yeast nutrients available?

A

-When the rice breaks up during fermentation

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13
Q

What can brewers do when there is a risk of contamination or of the yeast running out of nutrients? Why?

A

-Use so-haze koji
-The release of larger quantity enzymes result in the rice breaking up more quickly = yeast have enough nutrients

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14
Q

What is another thing the brewer can do to limit contamination or yeast running out of nutrients? When is this done?

A

-Adjust the mineral content of the water
-Done when making ginjo styles using tsuki haze koji with water with low mineral content

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15
Q

Is the influence of water very big?

A

-No, although it is the base of sake fermentation, the development of strong yeast strains and koji mouild strains helps to ensure the yeast have the correct amount of nutrients (even with low mineral water)

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16
Q

What are the 3 important roles of yeast ?

A

-They make ethanol from fermentable sugars
-Create aroma compounds and precursors to aroma comnpounds
-Organic compounds, such as acids

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17
Q

How does yeast affect the style of sake?

A

-different yeast strains lead to differences in aromas
-can also affect the texture and acidity of sake

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18
Q

With which temperatures can sake yeast stop working?

A

3 - 5 degrees celcius, but they can become active again when temperature rises

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19
Q

How did brewers in the past get their yeasts?

A

-Used ambient yeast available at the brewery
-Would take yeast from the foam of a successful fermentation to inoculate the next fermentation
-but: inconsistency, more chance of contamination or mutations
-contains many strains of yeast, ratio changes in successive fermentation

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20
Q

how do brewers get their yeast now?

A

-Isolate individual strains of yeast
-able to propagate batch after batch of yeast from the same original strain and avoid problems caused by mutations = consistency
-Most brewers choose from a small range of yeast strains bought from suppliers (such as; brewing society of Japan)

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21
Q

How has the brewing society of Japan (BrewSoc) become a reliable source for yeast?

A

-They manage the multiplication of yeast so that the brewing characteristics of the strains are retained

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22
Q

How is contamination avoided at the BrewSoc?

A

-Yeasts are numbered and packed in ampoules (soort afgesloten buisjes)

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23
Q

Which numbers of yeast strains are considered as reliable fermenters?

A

Number 6 (akita prefacture) &7 (nagano prefacture)

24
Q

What are the features yeast strain 6&7 share?

A

-Very reliable and strong
-produce more acidity than newly developed strains
-Produce less intense flavours

25
Q

Which yeast strain is considered to be more attractive (more fruity&floral), 6 or 7?

A

7

26
Q

Which yeast strain has become the industry standard? For what styles is it often used?

A

-number 7
-futsu-shu
-sometimes honjozo and junmai
-sometimes for ginjo, if not too heavy ginjo aromas are desired

27
Q

What are the characteristics op number 11? For what styles is it often used?

A

-a variant bred from number 7
-smae characteristics but good at fermenting through to dryness in high alcoholic conditions
-ideal for dry, non aromatic sakes

28
Q

Which yeast strains are especially suitable for ginjo style sake? (in the past)

A

-Number 9 (kumamoto prefacture) and 10 (ibaraki prefacture)
-Produce a higher level of acidity than more recently developed yeast
-development already started in 1911 to perform well in the annual sake awards

29
Q

although early ginjo yeast already existed, new yeasts strains were developed, why?

A

-For pronounced ginjo aromas and low acidity

30
Q

What are the yeast strains for low acid ginjo yeast?

A

-14 (ishikawa prefacture released in 1995)
-1801 (crossing of 9 and 1601, released in 2006)
-referred to modern yeast instead of classic yeast (6,7,9,10)

31
Q

For which styles are low acid ginjo yeasts used?

A

-commercial junmai ginjo and junmai daiginjo
-also ginjo and daiginjo

32
Q

What is the criticism of ‘modern’ yeast?

A

-That they can be bitter on the palate
-higher glucose levels to balance bitterness

33
Q

Which aromas does number 14 create compared to 1801?

A

-14: pear, banana
-1801: apple, melon

34
Q

which 2 directions are the BrewSoc exploring?

A

-yeast that create high levels of malic acid to give a more wine like balance
-red pigmented yeast that can contribute to a pink colour to sake if made in nigori style

35
Q

Why are low foaming yeasts developed?

A

-Wine and Beer also have some foam on top but not as much as sake
-lots of foam is sticky and yeasty which take up a lot of space in the tank which means bigger tanks were needed to avoid the sake to overflow
-lots of foam also more difficult to clean, can lead to contamination

36
Q

How is low foaming yeast developed?

A

-using beer or wine yeast not possible, because yeast is not adapted to high alcohol & low temperatures
-some of mutated yeast cells remain in fermenting liquid
-by repeating the process of removing the foam and keeping the yeast strains in the liquid, low foaming versions of existing strains can be isolated
-Then tested to ensure that the sake has desirable characteristics of the original strain

37
Q

How can a number be recognized for low foaming yeast?

A

-the original foaming version is added by ‘1’
-thus 9 is the foaming original version, 901 is the low foaming version
-Some new strains are per definition low foaming= 1501 and 1901

38
Q

What are the other 3 options of yeast outside of BrewSoc?

A

-Ambient yeast
-Proprietary yeast
-prefectural and regional yeast

39
Q

Why would a brewer choose for ambient yeast?

A
  • to show the expression on the raw materials
    -ambient/wild yeast is the same as with wine
40
Q

Is using ambient yeast risky? Why (not)?

A

-Yes, way more risky than with wine because in wine the natural high acidity can protect the juice from microbial contamination
-sake fermentations have little protection in the early stages

41
Q

What is proprietary yeast?

A

-yeast samples that are collected by brewers from successsful sake fermentations of other nature soucres such as flowers/trees
-leads to development of brewer-specific versions of more widely available strains or even new strains

42
Q

What is prefectural and regional yeast?

A

-Yeast that is isolated by a specific brewer but shared or sold to other brewers
-can contribute to a regional style e.g.: shizuoka prefecture with yeast prodyucing banana aromas with soft textures and low acidity

43
Q

name 3 successful prefectural yeast

A

-Shizuoka
-Akita
-Hiroshima

44
Q

Explain the characteristics of Shizuoka yeast strains

A

-Isoamyl acetate driven banana like aromas
-lower acidity

45
Q

Explain the characteristics of Akita yeast

A

-in 1990, medal winning
-long low temperature fermentations
-low levels of acidity
-pronounced ginjo aromas

46
Q

Explain the characteristics of Hiroshima yeast

A

-in 2013
-for highly aromatic sakes

47
Q

When yeast is bought with Brewsoc, how many ampoules are needed tor 100 kg of polished rice?

A

-between 2 and 5 ampoules

48
Q

What is another option to use yeast?

A

-first mutiply the yeast population in glass flasks containing a nutrient rich liquid created by dissolving koji in water before adding the contents of the flask to the shubo

49
Q

What is the shelf life of sealed ampoule yeast?

A

-50 days
-after multiplying in flasks, the yeast starts dying

50
Q

What does the shelf life of ampoules mean for the brewer?

A

Constantly need to purchase fresh supplies of ampoules

51
Q

Is it possible to buy already multiplied populations of fresh yeast? How does this work?

A

-Yes
-in plastic 500 ml bottles and brewers add one bottle per 150 kg of polished rice

52
Q

Does dry yeast have a long shelf life, when does a brewer choose for dry yeast?

A

-Yes, one year
-cost effective option, brewer skips shubo and a fermentation batch can be completed in 2 weeks
-ampoule yeast cannot be exported outside Japan, so then the only option for sake breweries is dry yeast

53
Q

Is dry yeast low or high foaming?

A

Low foaming

54
Q

Can yeast also be cultivated at the brewery? If so, how?

A

-Yes
-Can do a screening of the yeast population from their nutrient rich jelly in a petri dish
-Can then select particular colonies to transfer to test tubes containing nutrient-rich jelly
-Metal scrapers used to transfer yeast from the test tubes into nutrient rich liquid created by dissolving koji in water
-yeast mutate nsturally over a small number of generations = characteristics of pure stains cannot be perfectly retained

55
Q

When will a brewer choose to blend yeast?

A

-If he wants to combine features that already exist
-e.g. brewer might seek aromatic advantges of modern yeast (1801) while using classic yeast strain, such as 901 to fill out the palate and reduce the level of bitterness

56
Q

What are the 3 options to multiple yeast in one sake?

A

-Add a mix of yeast strains to the fermentation starter
-Create multiple fermentation starters, each with different single yeast strain, then combine these when starting the main ferment
-Create multiple batches of sake, each using a single strain of yeast, and blend these at some stage after the fermentations are completed

WSET 3 -saké (9 decks)

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