Production of γ-Aminobutyric Acid in Pumpkin Tissue Treated with Freeze-thaw Infusion of L-Glutamic Acid Monosodium Salt

We studied a method for producing high concentrations of γ-aminobutyric acid (GABA) in pumpkin tissue using freeze-thaw infusion. We introduced L-glutamic acid monosodium salt (MSG) into pumpkins by freeze thaw infusion, and observed that high concentrations of GABA were produced due to the action of the glutamate decarboxylase present in the pumpkins. For an enzyme reaction at 3°C, the amount of GABA peaked when the MSG concentration was 1% (w/w) and enzyme reaction time was about 48 h. When a softening enzyme (Macerozyme 2A) was added together with MSG and infusion was performed, a soft pumpkin that contained GABA at high concentrations was obtained. By freeze-thawing with MSG, it is now possible to manufacture functional foods that have two added values, i.e., in addition to enrichment of GABA, their hardness can also be adjusted.