Even simple water immersion prior to germination may have
the effect of raising the GABA content. Roohinejad et al. (2012)
observed changes in GABA content in eighteen rice varieties with
72 h immersion in distilled water (30 C) and reported that all rice
samples tested demonstrated increases in GABA content, although
the increase in GABA content widely differed among rice varieties.
Saikusa, Horino, and Mori (1994) studied the effect of soaking with
rice germs (8 varieties of japonica and 2 hybrid varieties of indica)
and observed similar GABA-enhancing trends, displaying nearly 8
times increase. The GABA content of a soaked germ of Hokkai
269 was more than 3 times that of the representative GABA-rich
tea. The authors explained that this trend in raising GABA content
through water immersion was closely related to the activation
of enzymes involved in GABA synthesis (e.g., GAD), glutamate
production, and GABA-decomposition (e.g., GABA-pyruvate
transaminase).