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When making soy milk, I've understood that you should disable some enzymes and that you do that with boiling heat for minimum of 15 minutes. Since boiling soy milk usually result in a messy boil-over, I'd like to use a lower temperature instead but haven't found any information about what temperature/time to use?

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According to this Lipoxygenase is a crucial enzyme to deactivate.

And in this paper they use 60°C for 30 minutes after soaking the beans. But the pH may also be important. For normal water pH is around 7.

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In the second paper referenced by Jiggunjer, they conclude the highest lipoxygenase inactivation (which will correspond to the lowest "beany" flavor) will be achieved by a 4 hour soak in 50 degree celsius (122 F) water at 8.5 ph, followed by 30 minutes of grinding at 60 C (140 F).

If I am reading their charts correctly, I'd suggest a slightly different recipe with a 5 hour soak at 50 C and 8.5 ph and a 15 minute grind at 60 C. Either way should get you a very low level of "bean"iness.

But, I don't think the soymilk recipe is done at that point, I think you still need to boil it to make some of the proteins digestible (or to break down some of the indigestible proteins). Wikipedia says "to improve its nutritional value by heat inactivating soybean trypsin inhibitor, improve its flavor and to sterilize the product".

So the soak and grind will get rid of the enzyme responsible for the nasty beany/green/grassy flavor you can get in soymilk, but it won't fully prepare the soymilk. You still need a boil or near boil, I think.

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