C8 - Rice Preparation - completed Flashcards

1
Q

How many steps in preparing rice before brewing?

A

four

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2
Q

What are the four stages in preparing rice before brewing?

A

1 - polishing
2 - washing
3 - soaking
4 - steaming

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3
Q

rice’s moisture level below ?? can be stored for weeks or months safely?

A

15%

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4
Q

Why rice needs to go through the preparation steps before can be used for brewing?

A

because rice stored the energy in solid starch form rather than fermentable sugar.

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5
Q

What are the three main objectives in preparing rice?

A

1 - reduce the levels of proteins, lipids, vitamins and minerals in the rice grain

2 - adjust the moisture level of the rice grain, suitable for making koji and fermentation

3 - gelatinise the starch to allow koji enzymes to break it down into sugar

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6
Q

Example of how the rice preparation choices influence the final style of sake?

A

when targeting a robust and flavoursome style, can use a less polished rice and no need to be precise in water absorption rate.

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7
Q

Why polishing rate is important in grading the sake?

A

The maximum ratios of polishing rate are defined for most grades.

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8
Q

what are the component in the outer layer of the rice grain important for the growth of koji and the fermentation?

A
  • protein
  • lipid
  • vitamin
  • mineral
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9
Q

what if the non-starch components in the rice grain are too much?

A

it will accelerate the koji propagation and the fermentation

Also these aromas, flavours and texture are not desired if making ginjo style sake.

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10
Q

briefly, how the rice are polished?

A
  • using a rice polishing machine with high-speed rotating rollers
  • the process is slow and gentle
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11
Q

why the polishing process needed to be slow and gentle?

A
  • to avoid the rice dried out and then cracked due to the heat and friction from polishing
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12
Q

When did the polishing machine become widespread and adopted?

A
  • the first half of the 20th century
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13
Q

How brewers do polishing before the polishing machine is available?

A

by hand or by watermills

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14
Q

What’s the consequence of polishing rice by hand or by watermills?

A

it’s impossible to reach a very low polishing ratio (seimai-buai) e.g. 60%

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15
Q

When was the first modern vertical rice-polishing machine developed?

A

around 1930

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16
Q

what was the initial use of the first vertical rice-polishing machine?

A

making sakes for competition only

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17
Q

When was the vertical rice-polishing machine become popular?

A

until 1980s

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18
Q

Why the vertical rice-polishing machine became popular in 1980s?

A
  • “ginjo bloom”
  • and the required brewing techniques became widespread
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19
Q

describe the structure of a rice polishing machine

A
  • rice tank on the top
  • rice drop into the polishing column
  • it has a vertical barrel
  • with an whetstone roller inside
  • a screen below the polishing column to filter the rice powder (nuka) removed
  • polished rice grains are transferred back to the top tank to repeat the polishing
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20
Q

How long does it takes to polish 600 kg brown rice to 70% semai-buai?

A

around 10 hours

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21
Q

How long it takes to polish 600 kg brown rice to 50% semai-buai?

A

around 45 hours

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22
Q

What’s next after the rice polished to the desired seimai-buai?

A

rest to cool down and re-absorb the moisture lost during polishing

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23
Q

Why it’s important to rest the rice grains after polished?

A

cooling down and re-absorbing the moisture can avoid cracking due to sudden temperature change when it’s washed in the next stage.

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24
Q

One of the factors determine when to change the roller layer and polishing speed:

A

depends on the characteristics of the rice variety.

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25
Q

How long does it take for the polished rice to cool down and re-absorb the moisture?

A

depends on the climate, usually 3-4 weeks

26
Q

what’s the main purposes (2) of washing?

A

1 - to remove the dust and remaining undesirable components (nuka)

2 - so all the rice can absorb water evenly in the next stage: soaking.

27
Q

How the rice washing machine wash the rice?

A
  • it blows fine air bubbles through the water
  • which bring all the rice contact with water evenly.
28
Q

other than hand-wash and machine wash, what’s the other option for mass production like futsu-shu?

A

large scale washing tanks

29
Q

what is the main purpose of soaking?

A

raise the rice’s water content to optimal level.

30
Q

what is the typical moisture level for soaking?

A

30 - 35%

31
Q

what factors affect the desired moisture level for soaking?

A
  • type of rice
  • polishing ratio
  • will be used for koji or not
32
Q

What are the potential problems if the moisture level is too high after soaking?

A
  • the koji mould will grow too quickly without appropriate enzymes
  • the rice will breaks up too quickly during fermentation, produce too much sugar
  • the yeasts will ferment too fast because of the excess supply of sugar
  • the final sake will not have the flavours and aromas produced especially in the case of ginjo and daiginjo.
33
Q

what is the typical temperature for soaking?

A

8 - 15C

34
Q

what are the considerations when deciding soaking time?

A
  • polishing ration > higher = less time
  • temperature > lower = slower
  • the initial and target moisture level of the rice
35
Q

how the brewer calculate the soaking time?

A
  • by trial and adjust with some trial batches
  • visually check and measure the moisture level
  • until the target level is achieved
36
Q

why there’s no formula in the ideal soaking time?

A

the rice and the environment conditions vary by day and by batch.

37
Q

why rice with 70% polishing ratio do not need precisely managed soaking time?

A
  • less polished rice have higher moisture level
  • which is slower in absorbing water
  • when the moisture level reached 30%, it hardly increase the moisture level
38
Q

why rice with 50% polishing ratio need precisely managed soaking time?

A
  • the rice is drier, easier and faster in absorbing water
  • if not managed precisely, it’ll easier go beyond the 30% moisture level
  • ginjo style sake needs precision in moisture level and distribution
39
Q

what techniques the brewer use to control the soaking time?

A
  • soaking the rice in very small batches
  • use cold water to slow down the absorption
  • use stopwatch to time the soaking.
40
Q

what the next step right after soaking?

A
  • drain completely
  • usually left to rest for several hours or overnight
41
Q

why the soaked rice need to handle carefully?

A

it’s more fragile because of high moisture level

42
Q

how long after soaking, the soaked rice go to steam?

A

within 24 hours.

43
Q

what are the main purposes of steaming?

A

1 - sterilises the rice

2 - change the structure of the starch molecules

44
Q

how much is the moisture level changed during steaming?

A

increased from 30% to around 40%

45
Q

what’s special about rice steaming in the whole brewing schedule?

A

it’s the first task of the brewing day.

46
Q

how large brewers steam rice in mass production?

A

use continuous steamers

47
Q

how long does it take to steam 700 kg of rice?

A

around 40 - 60 mins

48
Q

how is the rice separated inside the steamer

A

by clothes, layer by layer

49
Q

what’re the benefits of separating the rice in steamer by layer?

A
  • easier to load and unload quickly
  • easier to separate the rice for different purpose e.g. making koji
50
Q

what is the objective of steaming?

A
  • make sure all the rice grain are evenly cooked
  • all rice grain need to be firm outside but soft inside
  • target moisture level depends on the purpose of the steamed rice e.g. koji or kake-mai
51
Q

in the steamer, which layer has the lowest moisture level?

A

the top layer

52
Q

how will the rice on the top layer be used?

A
  • for making koji
  • since koji require lower moisture level
53
Q

What’s the additional technique to make sure the top layer of the steaming rice has the lowest moisture level?

A

a thick cloth is placed on top to prevent condensed water drip back onto the rice.

54
Q

technically why the top layer of steamer has the lowest moisture level?

A

it’s the furthest from the steam inlets at the bottom

55
Q

What if the brewer do not want the bottom layer of the steaming rice too moist?

A

place bags of fake rice (made from polypropylene) at the bottom, to keep the other rice away from the steam inlet

56
Q

what is the additional techniques used to ensure the moisture level, just before finishing the steaming?

A
  • a special heater to blow hot and dry air, reduce the moisture level of the grain’s outside but keeping the inside soft.
57
Q

how the continuous steamer for mass production works?

A
  • it has a conveyer, rice inlet at one end, exit for steamed rice the other end
  • nozzles blow high-pressure steam to the rice from below
  • rice are cooled in the next part
58
Q

what’s the advantage of using a continuous steamer which a traditional steamer cannot achieve?

A
  • precise controlled amount of steam to the rice, immediately when the rice enter the steaming chamber
  • take only 30 - 40 minutes from steam to cool down
  • can process tonnes of rice in a day
59
Q

How the toji check if the rice is steamed perfectly?

A
  • by making a rice cake using the steamed rice
  • they squeeze or chew the rice cake to check the elasticity
60
Q

traditionally, how the steamed rice are cool down?

A

by spreading on mats

61
Q

when will the cooled rice be sent to the next stage?

A

Till it has been cooled down to the target temperature

62
Q

what’s the next stage after the rice are cooled down?

A
  • send to the koji room to make koji
  • add to the making of fermentation starter
  • or add to the main fermentation