Accumulation and Degradation of Two Functional Constituents, GABA and .BETA.-Glucan, and Their Varietal Differences in Germinated Barley Grains

Abstract

The changes in the contents of two functional constituents, γ-aminobutyric acid (GABA) and (1→3)(1→4)-β-D-glucans (β-glucan), during germination were investigated in two malting barley varieties in order to determine the optimal conditions for accumulation and degradation of these constituents in dried barley grains after germination treatment. A time-course analysis during germination treatment revealed that the content of GABA remarkably increased in the 48 hour imbibition process and decreased in the subsequent germination process. On the other hand, β-glucan, which is known to be decomposed during malting, did not undergo substantial degradation after the 48 hour imbibition process. These findings thus indicated that it is possible to produce germinated barley grains containing these functional constituents at high levels by optimal germination treatment. A total of 43 barley varieties were surveyed for the GABA and β-glucan contents in germinated grains. Our results also indicated that there were varietal differences in the content of each ingredient. A waxy starch variety in which the contents of both β-glucan and GABA were higher than those in the other barley varieties tested, could become a promising source of the two functional constituents.

Sequential hydration with anaerobic and heat treatment increases GABA (γ-aminobutyric acid) content in wheat

“…In addition, the germination process activates many enzymes in raw seeds. Enzyme activities do not change by the imbibition process, but are rapidly increased during germination (Kihara, Okada, Iimure, & Ito, 2007). This is especially true for glutamate decarboxylase (GAD) enzyme activity, which catalyses L-glutamic acid to GABA (Iimure et al, 2009;Jannoey et al, 2010;Oh, 2003).…”

A metabolite profiling approach to follow the sprouting process of mung beans (Vigna radiata)

“…The precursor of GABA, glutamic acid was also significantly increased during the sprouting process. Increased levels of GABA have also been reported for germinated cereals like barley (Kihara et al 2007) and wheat (Nagaoka 2005). Enhanced contents of GABA in sprouts for human nutrition are of special interest because of its health-promoting impact (Ito 2004).…”

A method for production of γ-amino butyric acid (GABA) using barley bran supplemented with glutamate

“…Liu et al (2005) and Saikusa et al (1994a) revealed that the accumulation of GABA in rice grain during water soaking is related to the activity of GAD, which is the rate-limiting enzyme for GABA synthesis. It was also suggested that the GABA content in germinated barley grain was higher than those in germinated wheat and rice grain (Ito, 2004;Kihara et al, 2007). In this study we did not examine GAD activity, but the activity might be higher in barley bran than those in wheat and rice brans.…”

“…Matured or germinated barley grain contains GABA (Kihara, Okada, Iimure, & Ito, 2007). The activity of glutamate decarboxylase (GAD) that converts glutamate to GABA in one step remains in matured barley seed (Inatomi & Slaughter, 1975).…”