Temperature, water content, and polishing effects on koji #6
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| Of course, the researchers know that growing koji for a fixed time at different temperatures would not be a fair comparison. At different temperatures, the koji's growth rate (μ, measured in h<sup>-1</sup>) is also different. Thus, enzyme activity was compared at two points different points: | ||
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| 1. When the koji reaches 10mL oxygen/g dry weight of koji, and; |
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yea this line - I don't know what "10mL oxygen/g dry weight of koji" represents
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Agreed I worded it confusingly.
10mL oxygen consumed per gram of koji (dry weight basis)
Let me think of a better way to word this ; maybe
"When the koji has consumed 10mL of oxygen per gram of koji (dry weight basis)"
| Another parameter they tested is the **steamed rice water absorption rate**, which is defined as follows: | ||
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| \text{Steamed rice water absorption rate (%)} = \frac{\text{Steamed rice weight} - \text{White rice weight}}{\text{White rice weight} } \times 100\% |
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Thoughts on "Dry rice weight" instead of "White rice weight"?
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Maybe: uncooked rice weight?
Agreed white rice weight is confusing. The key is that it is the weight of "raw" rice i.e. straight out of the bag
I want to avoid "dry rice weight" which may be confused with "dry weight" (0% moisture)
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| *Conclusion:* although wetter rice will grow koji faster, it yields less enzymes in total (both amylase and proteases). | ||
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| Koji makers already knew that overly wet rice yielded weak koji. Another researcher found that wet rice lead to the over-accumulation of glucose, which inhibits enzyme production. In practice, the water content actually changes throughout the koji production period as some of the water vapour is released from the rice. Typical operations start at 35-40% steamed rice water absorption rate, and finish at 24 - 28% (mirin) down to 17-19% (sake). |
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Another researcher found that wet rice lead to the over-accumulation of glucose, which inhibits enzyme production.
sounds like a case of "positive transcription control", similar to what happens under Can we affect the amount of lactase produced? here: https://controlledmold.com/why-does-koji-make-lactase-anyways/
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Absolutely this is internal feedback inhibition
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| As an aside, this was the experimental set-up: | ||
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| {:.responsive .center} |
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this image is excellent, btw
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Thanks - this will be the header image
| 1. When the koji reaches 10mL oxygen/g dry weight of koji, and; | ||
| 2. When the koji reaches a maximum cell mass | ||
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| *Conclusion:* in general, higher temperatures favour amylases, and lower temperatures favour proteases and peptidases. |
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Any thoughts on a mechanism? That is, why does temperature have this effect?
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I can only guess - but I'll see if any researcher proposed a reason. Maybe an evolutionary adaptation from aspergillus? High temps means more carbs are present = make more amylase? That would be my guess.
Temp control ... minor edits
…ld.github.io into temp-control * 'temp-control' of github.com:ControlledMold/ControlledMold.github.io: Update 2020-10-10-temperature-water-content-and-polishing-effects-on-koji.md Update 2020-10-10-temperature-water-content-and-polishing-effects-on-koji.md Update 2020-10-10-temperature-water-content-and-polishing-effects-on-koji.md
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Looks good to me! Okay with a Monday morning publish time (we can always make changes before and after, too)? As mentioned previously, do you want to share on Reddit? |
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Sounds good for Monday morning, and sure I'll post it to reddit. |
cc @daizu27 here's your latest blog post.
BTW, I've added you as a contributor to this repository: you can pull and push to branches & master just like me (ex: you should be able to edit this branch). You may have to delete your local repo and reclone to get that access though - not sure. Let me know if I can help.
Todo: