In the 2008 paper "Effects of soaking, germination and fermentation on phytic acid, total and in vitro soluble zinc in brown rice", Dr. Robert J. Hamer's group found that soaking alone didn't have much of an effect on phytic acid in brown rice. However, fermentation was highly effective at degrading it. What I didn't realize the first time I read the paper is that they fermented intact brown rice rather than grinding it. This wasn't clear from the description in the methods section but I confirmed it by e-mail with the lead author Dr. Jianfen Liang. She added that the procedure comes from a traditional Chinese recipe for rice noodles. The method they used is very simple:
- Soak brown rice in dechlorinated water for 24 hours at room temperature without changing the water. Reserve 10% of the soaking liquid (should keep for a long time in the fridge). Discard the rest of the soaking liquid; cook the rice in fresh water.
- The next time you make brown rice, use the same procedure as above, but add the soaking liquid you reserved from the last batch to the rest of the soaking water.
- Repeat the cycle. The process will gradually improve until 96% or more of the phytic acid is degraded at 24 hours.
You can probably use the same liquid to soak other grains.