Water and Yeast

Question 1

Where do brewers source their water?

Answer 1

It varies from brewery to brewery.

• natural subsoil sources
• filtered tap water for consistancy

Whatever the source, brewers can filter and alter the mineral and acid content of their water

Question 2

What are the standards that water for sake production must meet?

Answer 2

• food manufacture standards
• upper limits on organic substances
• the level of iron permitted is less than 10% of what is allowed for tap water

Question 3

Why is a low iron content a requirement of sake water?

Answer 3

Too much iron and the sake will be a reddish-brown colour and spoil aroma and flavour.

Question 4

What does ‘hardness’ and ‘softness’ of water refer to?

Answer 4

The dissolved magnesium and calcium in the water

• calcium is the dominant metal
• magnesium enhances the metabolism of the yeast

Potassium and phosphorous also aid healthy yeast and kōji growth but are not discussed when water hardness is measured.

Question 5

What role does magnesium play in sake production?

Answer 5

Higher levels of magnesium in the water enhances the metabolism of the yeast

Question 6

Is Japan’s water generally hard or soft, from an international perspective?

Answer 6

Soft

Question 7

What style of sake do mineral-rich waters high in potassium, phosphorous and magnesium produce?

Answer 7

Fast, stable fermentation that produces a restrained and dry style.

Most famous from the Nada area of Kōbe

Question 8

What is the water from the Nada area of Kōbe in Hyōgo prefecture called?

Answer 8

Miya-mizu

‘Miracle water’

Question 9

Where is miya-mizu water found?

Answer 9

Nada area of Kōbe in Hyōgo prefecture

‘Miracle water’ high in minerals

Question 10

Which area of Kyōto famous for sake has low mineral content in the water and produces soft-style sake?

Answer 10

Fushimi

Question 11

Why are sake from Fushimi in Kyōto produced in a softer style?

Answer 11

Low mineral content in the water

Question 12

What is the benefit of using sō-haze kōji in a sake made from low mineral water?

Answer 12

The large quantity of enzymes results in the rice breaking up quickly which provides nutrient for the yeast and a healthy ferment.

If tsuki-haze was used with soft water, it would take time for the yeast colony to multiply and there is a risk of contamination or running out of nutrient. For the production of ginjō sake in a soft water area, the brewer would adjust the mineral content of the water.

Question 13

How can a brewer produce a ginjō sake using tsuki-haze in a soft water site?

Answer 13

By adjusting the mineral content of the water, he can provide more nutrient fo r the kōji and yeast.

Question 14

What are the three roles of yeast in sake production?

Answer 14

• convert sugar to alcohol
• create aroma compounds
• create organic compounds including acids

Question 15

Which has more impact on the style of sake produced - rice, yeast or kōji?

Answer 15

Yeast.
Rice and kōji only have a subtle effect.
Yeast impacts aroma, texture and acidity

Question 16

What impact does yeast have on the style of a sake?

Answer 16

Aroma
Texture
Acidity

Question 17

Which yeast species is used for making sake?

Answer 17

Saccharomyces cerevisiae

Question 18

Why does Saccharomyces cerevisiae continue to work in a sake fermentation when it is killed at similar alcohol levels in beer or wine production?

Answer 18

Mutated yeasts that can operate at high alcohol levels have been selected by brewers.

Question 19

What is the upper permitted legal abv % for sake?

Answer 19

22%

Above 22%, it ceases to be legally sake

Question 20

Who is the main supplier of yeasts to the sake industry?

Answer 20

Brewing Society of Japan

Question 21

When did the Brewing Society of Japan begin to distribute sake yeast?

Answer 21

1906

Question 22

Name two yeasts that are known for reliable fermentations.

Answer 22

#6
#7

Question 23

Name two yeasts that are referred to as ‘early ginjō’ yeast and were developed in the pursuit of better aromas.

Answer 23

#9
#10

Question 24

Sake yeasts #1 - #8 were released between 1916 and 1963. What was their intent?

Answer 24

• brewers wanted reliable fermentations, so no batches were lost
• sake was a valuable tax revenue stream for the Japanese government so reliability was important from this perspective

Question 25

Which yeast was isolated at Aramasa brewery in Akita and released in 1935?

Answer 25

6

Question 26

In which year was #6 yeast released, after being isolated at which brewery?

Answer 26

1935

Aramasa in Akita prefecture

Question 27

Which yeast was isolated at Miyasaka brewery in Suwa city and released in 1946?

Answer 27

7

Question 28

In which year was #7 yeast released, after being isolated at which brewery?

Answer 28

1946

Miyasaka brewery in Suwa city

Question 29

Which yeast is the ‘industry standard’, used for much futsū-shu?

Answer 29

7

Question 30

What is the character of yeast #6?

Answer 30

• reliable fermentation
• produce more acidity than more recently isolated yeasts
• muted aromas (pre-dates the ginjō boom)
• less fruity than #7

Question 31

What is the character of yeast #7?

Answer 31

• reliable fermentation
• produce more acidity than more recently isolated yeasts
• muted aromas (pre-dates the ginjō boom)
• sweeter and more fruity than #6
• the industry standard, used for futsū-shu as well as hon-jōzō, junmai and occasionally ginjō

Question 32

How are yeasts #7 and #11 comparable?

Answer 32

Yeast #11 was bred from #7 and they have similar characteristics.
Yeast #11 is especially good at fermenting through to dryness in high alcohol conditions, so useful for dry and non-aromatic sake.