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I make a lot of tofu and soy milk from soy beans, leaving me with a lot of okara as a by product.

"Okara, soy pulp, or tofu dregs is a pulp consisting of insoluble parts of the soybean that remain after pureed soybeans are filtered in the production of soy milk and tofu. ... Due to its high moisture and nutrient content, okara is highly prone to putrefaction, and this has limited its commercial use" - Okara - Wikipedia

It's high in protein and other nutrients, so is a shame to leave to waste, but it's not something that can be stored as-is for very long, it starts to go off after a day or so.

The only feasible options for long term storage are freezing, or as I have found - dehydration.

I stick it in the oven spread out on a tray at 100c for a few hours, stirring occasionally. Then blend the resulting clumps into a kind of soy flour.

The resulting flour is useful for all kinds of things - adding to protein shakes, using a 50/50 mix with wheat flour to make bread, adding into oat porridge, etc.

Can I expect to store the flour for just as long as other more common flours such as wheat flour? Do I need to worry about oxidation? (Soy beans are high in oils).

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The safety of the flour will depend on water activity. We cannot know the water activity of the flour produced in your kitchen, but 1) home dehydration is known to generally create shelf-stable products, and 2) if you could create a powder, it is pretty certain that you don't have enough moisture for bacteria to survive. And while molds can survive much lower amounts of water than bacteria, the good news about them is that you will notice dangerous levels of mold itself, while bacteria can be dangerous before you notice rotting. So I would tend to treat it as any dehydrated plant matter and consider it safe.

The oxidation will certainly happen. It does not fall under food safety, but is considered a quality issue. Oxidation is common in flours. Commercial wheat flour is defatted and has antioxidants added, but other types of flour, especially nut flours and nut meals, are eaten oxidized, unless you grind them fresh for every dish. For any quality issues, it is up to you to decide whether they bother you.

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  • Great answer. What about aflatoxin?
    – Karl
    Apr 11 at 10:23

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