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WSET 3 -saké > Chapter 9: preparing koji > Flashcards

Chapter 9: preparing koji Flashcards

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1
Q

How many % of rice for sake is treated with koji?

A

+/- 20%
- At least 15% by law for premium sake

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2
Q

What is the main purpose of koji?

A

To provide enzymes that break down rice starches into fermentable glucose sugars

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3
Q

Why do sake brewers need to use other sources for the required enzymes than other cereal grains?

A
  • It is possible to malt rice using germintation to activate the rice own enzymes but this would require unpolished rice grains and the flavours are undesirable in sake
  • Gelatinisation temperature for rice starch is so high that the steaming would destroy enzymes
    -Polishing removes the germ, so polished rice cannot be malted
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4
Q

What is the Japanese term for koji mould?

A

Koji-kin

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5
Q

What do the koji spores exist of? what does it need to thrive?

A

-Seeds from which the mould grows
-requires: warm temperature + high levels of water in grains of steamed rice
-too cold and too little water content? Mould stops to grow

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6
Q

What are the differences between wooden koji rooms and steel rooms?

A

-wooden: absorb and release humidity and atmosphere changes more smoothly, downside: the Japanase red cedar (sugi) is expensive and difficult to maintain
-stainless steel: lack buffering effect of wood, more changes. Need to use precise systems to control temperature and humidity. +: easier to keep clean and conditions can be controlled and altered quickly when needed

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7
Q

How does the mould grow into the rice grain? What happens then?

A

-By sending hyphae (feeding tubes that are part of the mould’s body) into the rice grain
- these hyphae enzymes break down the rice starches and proteins resulting in amino acids and glucose which then is absorbed into the hyphae and supports further growth

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8
Q

What is a compound produced by koji giving sake its colour?

A

Flavins

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9
Q

Why are amino acids important?

A

Important yeast nutrient and contributes to umami and a bit to acidity

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10
Q

Why are vitamins important?

A

Yeast nutrients

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11
Q

What are amylases?

A

Enzymes that break starch molecules into smaller parts (glucose , limit dextrins) thus from starch to sugar

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12
Q

What are proteases?

A

Enzymes that break down proteins into peptides and amino acids.

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13
Q

What happens with the sake if large quantities of proteases are present in the main fermentation? How can this be controlled?

A

-Increases amino acids in sake, too high levels are undesirable
- can be controlled by limiting the levels of proteases and minimising yeast death

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14
Q

How can a brewer control proteases enzymes?

A

-They are produced most rapidly at 34-37 degrees
- if low levels of umami are desired, pass quickly through this temperature
-if higher levels of umami are desired, can linger longer on this temperature

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15
Q

What are the 3 major koji strains?

A

Yellow, black and white

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16
Q

Which strain is mostly used for koji? Why?

A

-Yellow
-Produce low levels of citric acid compared with black and white koji mould
-Now also black and white used for shochu (spirit) or brewers experiment to create a sake with structure and balance

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17
Q

What are the 2 formats of koji mould? Explain

A

-Powdered: mould spores used for automated koji making
-Granulated: is rice with koij mould with spored growing on it

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18
Q

Which type of koji do large scale breweries mostly use? Why?

A

-Powdered koji mould
-no rice grain so suitable to inoculate at a constant density of spores by automated machines

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19
Q

Which type of koji do small scale breweries mostly use? Why?

A

-Granulated, especially for ginjo
-fewer spores available compared to the amount of rice = easier to achieve a light, even covering of spores over the rice

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20
Q

What are the 2 names of desirable mould growth patterns?

A

-So-haze
-Tsuki-haze

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21
Q

How does the koji mould grows with So- haze? How is this encouraged?

A

-Mould covers entire rice grains and sends many hyphae into the centre of the rice grain
-encouraged by inoculating high quantity of mould spores and using rice grains with a higher moisture content (not too high for uneven growth)

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22
Q

Does so-haze has low or high levels of enzymes, vitamins, sugars, amino acids, fatty acids and peptides?

A

High levels because with so-haze high levels of enzymes, causing a more rapid starch to sugar conversion + vitamins and other nutrients to support faster fermentation

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23
Q

For what style of sake is So-haze typically used?

A

-For sake with warmer fermentation for more body and flavour in final sake
-more fatty acids thus decreased ginjo aroma’s
-ideal for futsu shu to boost flavour intensity and compensate for some of the dilution when jozo alcohol is added
-also Premium sake with intense flavour, full body, high acidity and high umami

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24
Q

How does the koji mould grows with tsuki-haze?

A
  • In a lightly spotted pattern over the rice grain
    -Some grains have hyphae and others do not
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25
Q

How is the tsuki-haze mould growth encouraged by the brewer?

A
  • The amount of koji mould spores used, is restricted
    -The level of moisture in the grains is controlled and kept at low level
    -koji room is warm and less humid
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26
Q

Why and what does the brewer need to do to achieve high levels of ester in their sake ?

A

-Why: fatty acids too high? can inhibit formation of isoamyl acetate which is the main ester contributing to ginjo aromas
- Want high levels of esters? inhibit fungal growth to keep lipids at low level

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27
Q

What can minimise the development of proteases?

A

-Higher temperatures and drier conditions in the later stages of koji making
-leading to more delicate and lighter style of sake

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28
Q

For which type of sake is Tsuki Haze preferred?

A

-ideal for very slow, controlled cold fermentation and for ginjo aromas
-ideal for (dai)ginjo: pure,delicate, low acidity & umami
-Honjozo with lean texture

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29
Q

If a brewer wants a sweet daiginjo sake and low acidity and umami, what kind of koji strain will he use? what are options he is likely to use for brewing?

A

-One that produces higher glucoamylase + tsuki haze style
- higher temperature to increase amylase and to minimise the development of proteases = higher sugar levels (glucose) and lower umami (amino acids)

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30
Q

What would be a reason to use a partially automated koji machine?

A

To achieve more consistent production while improving the quality potential in long-term by collecting and compiling databases

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31
Q

What are the 7 steps of koji making?

A

-Bringing in
-Spreading the spores
-Re-breaking up
-Mounding
-Middle work
-Final work
-Sending out

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32
Q

When the koji is brought in, to what temperature is it chilled?

A

Between 32-35 degrees celcius

33
Q

How is cooling down executed with hand-made koji?

A

On mats outside of the koji room, thus in the cooler conditions of the brewery

34
Q

What is the large shallow bed called where the koji is put on in the koji room?

A

Toko

35
Q

How is koji chilled with fully automated machines for koji making?

A

On a cooling conveyor linked to a continuous steamer from where the grains are transferred by tubes or conveyors to the koji making machine

36
Q

How many hours after the koji is brought in are the spores spread out?

A

Between 1-3 hours

37
Q

How long does the initial mould growth last?

A

Between 10-12 hours, temperature rises up to 33-35 degrees

38
Q

What is the aim of spreading the spores?

A

-To inoculate the rice grains with koji spores and encourage mould germination and growth
-To ensure that the spores spread as evenly as possible

39
Q

What is used to spread the koji spores?

A

Hand shakers, depends on brewer how he shakes, some high and some low. Some fast and some slow

40
Q

Will a brewer add a greater or lesser quantity of spores to a so-haze style?

A

More

41
Q

What happens after inoculation?

A

Covered in blankets to retain warmth and moisture to encourage the mould to germinate and grow for around 8-12 hours

42
Q

What does mould create? Does this need to be monitored?

A

-Heat
-A brewer monitors the temperature so that he can intervene if it falls too low or too high

43
Q

How is koji inoculated with fully automated machines?

A

-Spraying them with spores while they are transferred by a pipe from the steamer ton the koji making machine
-Often a large rotating drum, rice is laid out to cover the base.
-A rotating roller moves the rice
-Temp & humidity can be controlled -> creates high temp & humidity ro mimic the effect of the blanket to promote growth of mould

44
Q

What happens temperature wise with the re-breaking up of koji?

A

-The rice has risen up to 33 degrees, reduced to 31 degrees and then rises back up after few hours to 33 degrees

45
Q

What is the aim of re-breaking up?

A

To ensure even mould growth and avoid hot spots occurring

46
Q

What happens during re-breaking up?

A

-Mould has started to grow, some with uneven patches
-Mould has created heat so temp. rises to 33 degrees, with some cooler and hotter parts
-Re-breaking up helps to ensure mould growth happens evenly throughout the rice
-Also allows heat to escape from any warm spots with the risk that the fungus will grow too much

47
Q

How is re-breaking up carried out if the koji is hand made?

A

-brewer unwraps rice, spreads it back out over the bed and breaks up any clumps of rice
-After this: wrapped up again, ambient temperature and humidity in koji room helps mould to continue to grow for another 8-12 hours

48
Q

How is re-breaking up carried out with koji machines?

A

-Rice is broken up by rotating rollers and temperature and humidity are set high enough to keep on encouraging the growth of the mould

49
Q

What is the aim of mounding?

A

To manage the level and distribution of the mould growth, and start the drying process instead of encouraging the mould growth

50
Q

What is determined during mounding?

A

The growth pattern within each individual grain: so-haze, tsuki-haze or in between rather than the whole mass of rice

51
Q

What are 3 main options of mounding (handmade koji)?

A

-Bed Koji
-Box Koji
-Tray Koji

52
Q

Explain bed koji

A
  • on a bed (toko), same as used during other stages
    -big batches of koji: 100-300 kg compared to other mounding options
    -precise control of koji mould growth not possible
    -suitable for futsu-shu, honjozo, junmai and sometimes ginjo
53
Q

Explain box koji

A

-medium sized boxes: 15-40 kg
-with divider so the brewer can slide the rice from one half to the other to allow accurate control of mould growth
-too labour intensive for futsu-shu, used for daiginjo

54
Q

How much rice can fit into a tray koji?

A

1.5 kg to 2.5 kg = very small

55
Q

What is the benefit of tray koji?

A

-It is very small, allowing precise control of temperature and water content in the rice

56
Q

Is tray koji labour intensive? why or why not?

A

-Yes, because brewers need to keep re-stacking up the trays to avoid the different layers creating inconsistencies in temperature
-And thus suitable for daiginjo although sometimes difficulties with consistency

57
Q

Why are trays or boxes regularly checked during mounding stage?

A

-checked and rearranged every few hours to avoid differences in mould growth occuring between the trays/boxes at the top (warmer) and the bottom (where it’s cooler)

58
Q

Does the checking of trays and boxes have to be manual? Explain

A

-No, can also be put in racks and rearranged mechanically in an enclosed space where a computer controls the temperature and humidity.
-now also possible to make tsuki-haze this way, so it doesnt effect quality

59
Q

What happens during mounding for fully machine made koji?

A

Rice remains in the drums. The level and pattern of mould growth are determined by adjusting the temperature and humidity
-Also use rollers to move the rice around
-not possible for high quality tsuki-haze

60
Q

What is the aim of middle work?

A

-To encourage release of heat and the drying out of the rice grain

61
Q

What happens with the temperature during middle work?

A

-Reduced from 36 to 33 degrees and than rise again to about 38 degrees

62
Q

How should middle work be completed with koji for ginjo styles?

A

-Should be completed quickly because when koji passes through 34-37 degrees, protease enzymes are most actively produced (and low levels of umami is desired in ginjo style)

63
Q

What happens with the position of the rice compared to mounding? why?

A

-Its surface area becomes larger by flattening the shape of the mound and drwaing patterns into the surface
-The larger surface area helps heat to escape and water to evaporate from the surface of the rice grains

64
Q

Why is it important during middle work that heat and water evaporates?

A

Because after mounding the koji growth is most vigorous, thus most heat is generated and excess of heat can kill the mould (mould growth stops at an earlier stage than desired by brewer)

65
Q

What kind of aromas does dying koji produce?

A

-undesirable aromas and flavours = sweaty and taint

66
Q

How is the surface area during middle and final work made with box & tray koji compared to bed koji?

A

-box&tray= starts as a mound (bergje) and then spread out as widely as possible within the box/tray by hand, also patterns decided by brewer
-bed koji = wooden plough which is as large as the bed, to plough the rice from one side to another

67
Q

How is middle work carried out with machine made koji?

A

-Rotating rollers steadily distribute the rice and draw patterns to allow the heat and water to escape
-temperature and water content inside remain high enough that koji on the surface is not cooler or drier than the koji in the centre

68
Q

What is the temperature during the final work?

A

higher than 38 degrees to reach the highest temperature of the koji making process (not higher than 43, otherwise stress for koji)

69
Q

What is the aim of the final work?

A

-To continue drying out the rice grains and to continue releasing the heat created by koji mould activity
-to achieve good tsuki-haze

70
Q

What does koji releases during the final work?

A

-roasted chestnut aroma and slightly sweet taste

71
Q

To what does the focus shift during final work?

A

From removing heat to removing moisture

72
Q

What is done with machine made koji during the final work?

A

-The rotating roller continues to reshape the rice to increase the surface area
-The temperature and humidity inside are managed to encourage evaporation

73
Q

When is sending out carried out?

A

-44 to 50 hours after the koji is brought in

74
Q

What happens with the temperature when koji is send out?

A

-significantly reduced from 38-45 to 10-15

75
Q

What is the purpose of sending out?

A

To stop koji mould growth by cooling down and drying out the grains

76
Q

Why is koji not heated to stop them from creating more enzymes but chilled and dried?

A

-With heating the mould would be killed but create off-flavours
-Chilling and Drying, stops the mould from growing without killing it and without creating off-flavours

77
Q

How is the koji manually chilled and dried?

A

By moving the vessels (tray,bed or boxes) out of the koji room to a cool and dry location with fans that speed the cooling process by blowing cool air

78
Q

How is machine made koji chilled and dried?

A

The temperature and moisture inside the drum are automatically reduced

79
Q

When is frozen koji used? What are disadvantages?

A

-Option for breweries that make sake throughout the year
-lactic acid bacteria can be harmed when koji is frozen and the resulting loss of these bacteria can be problematic to make a kimoto/yamahai
-Lactic acid bacteria are not killed by instant freezing but can be damaged if it is frozen and defrosted again (several times)

WSET 3 -saké (9 decks)

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