C8 - Rice Preparation - completed Flashcards
How many steps in preparing rice before brewing?
four
What are the four stages in preparing rice before brewing?
1 - polishing
2 - washing
3 - soaking
4 - steaming
rice’s moisture level below ?? can be stored for weeks or months safely?
15%
Why rice needs to go through the preparation steps before can be used for brewing?
because rice stored the energy in solid starch form rather than fermentable sugar.
What are the three main objectives in preparing rice?
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
Example of how the rice preparation choices influence the final style of sake?
when targeting a robust and flavoursome style, can use a less polished rice and no need to be precise in water absorption rate.
Why polishing rate is important in grading the sake?
The maximum ratios of polishing rate are defined for most grades.
what are the component in the outer layer of the rice grain important for the growth of koji and the fermentation?
- protein
- lipid
- vitamin
- mineral
what if the non-starch components in the rice grain are too much?
it will accelerate the koji propagation and the fermentation
Also these aromas, flavours and texture are not desired if making ginjo style sake.
briefly, how the rice are polished?
- using a rice polishing machine with high-speed rotating rollers
- the process is slow and gentle
why the polishing process needed to be slow and gentle?
- to avoid the rice dried out and then cracked due to the heat and friction from polishing
When did the polishing machine become widespread and adopted?
- the first half of the 20th century
How brewers do polishing before the polishing machine is available?
by hand or by watermills
What’s the consequence of polishing rice by hand or by watermills?
it’s impossible to reach a very low polishing ratio (seimai-buai) e.g. 60%
When was the first modern vertical rice-polishing machine developed?
around 1930
what was the initial use of the first vertical rice-polishing machine?
making sakes for competition only
When was the vertical rice-polishing machine become popular?
until 1980s
Why the vertical rice-polishing machine became popular in 1980s?
- “ginjo bloom”
- and the required brewing techniques became widespread
describe the structure of a rice polishing machine
- 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
How long it takes to polish 600 kg brown rice to 70% semai-buai?
around 10 hours
How long it takes to polish 600 kg brown rice to 50% semai-buai?
around 45 hours
What’s next after the rice polished to the desired seimai-buai?
rest to cool down and re-absorb the moisture lost during polishing
Why it’s important to rest the rice grains after polished?
cooling down and re-absorbing the moisture can avoid cracking due to sudden temperature change when it’s washed in the next stage.
One of the factors determine when to change the roller layer and polishing speed:
depends on the characteristics of the rice variety.
how long it takes the polished rice to cool down and re-absorb the moisture?
depends on the climate, usually 3-4 weeks
what’s the main purposes (2) of washing?
1 - to remove the dust and remaining undesirable components (nuka)
2 - so all the rice can absorb water evenly in the next stage: soaking.
How the rice washing machine wash the rice?
- it blows fine air bubbles through the water
- which bring all the rice contact with water evenly.
other than hand-wash and machine wash, what’s the other option for mass production like futsu-shu?
large scale washing tanks
what is the main purpose of soaking?
raise the rice’s water content to optimal level.
what is the typical moisture level for soaking?
30 - 35%
what factors affect the desired moisture level for soaking?
- type of rice
- polishing ratio
- will be used for koji or not
What are the potential problems if the moisture level is too high after soaking?
- 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.
what is the typical temperature for soaking?
8 - 15C
what are the considerations when deciding soaking time?
- polishing ration > higher = less time
- temperature > lower = slower
- the initial and target moisture level of the rice
how the brewer calculate the soaking time?
- by trial and adjust with some trial batches
- visually check and measure the moisture level
- until the target level is achieved
why there’s no formula in the ideal soaking time?
the rice and the environment conditions vary by day and by batch.
why rice with 70% polishing ratio do not need precisely managed soaking time?
- 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
why rice with 50% polishing ratio need precisely managed soaking time?
- 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
what techniques the brewer use to control the soaking time?
- soaking the rice in very small batches
- use cold water to slow down the absorption
- use stopwatch to time the soaking.
what the next step right after soaking?
- drain completely
- usually left to rest for several hours or overnight
why the soaked rice need to handle carefully?
it’s more fragile because of high moisture level
how long after soaking, the soaked rice go to steam?
within 24 hours.
what are the main purposes of steaming?
1 - sterilises the rice
2 - change the structure of the starch molecules
how much is the moisture level changed during steaming?
increased from 30% to around 40%
what’s special about rice steaming in the whole brewing schedule?
it’s the first task of the brewing day.
how large brewers steam rice in mass production?
use continuous steamers
how long it take to steam 700 kg of rice?
around 40 - 60 mins
how the rice are separated inside the steamer
by clothes, layer by layer
what’re the benefits of separating the rice in steamer by layer?
- easier to load and unload quickly
- easier to separate the rice for different purpose e.g. making koji
what is the objective of steaming?
- 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
in the steamer, which layer has the lowest moisture level?
the top layer
how will the rice on the top layer be used?
- for making koji
- since koji require lower moisture level
What’s the additional technique to make sure the top layer of the steaming rice has the lowest moisture level?
a thick cloth is placed on top to prevent condensed water drip back onto the rice.
technically why the top layer of steamer has the lowest moisture level?
it’s the furthest from the steam inlets at the bottom
What if the brewer do not want the bottom layer of the steaming rice too moist?
place bags of fake rice (made from polypropylene) at the bottom, to keep the other rice away from the steam inlet
what is the additional techniques used to ensure the moisture level, just before finishing the steaming?
- a special heater to blow hot and dry air, reduce the moisture level of the grain’s outside but keeping the inside soft.
how the continuous steamer for mass production works?
- 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
what’s the advantage of using a continuous steamer which a traditional steamer cannot achieve?
- 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
How the toji check is the rice steamed perfectly?
- by making a rice cake using the steamed rice
- they squeeze or chew the rice cake to check the elasticity
traditionally, how the steamed rice are cool down?
by spreading on mats
when will the cooled rice be sent to the next stage?
Till it has been cooled down to the target temperature
what’s the next stage after the rice are cooled down?
- send to the koji room to make koji
- add to the making of fermentation starter
- or add to the main fermentation
