Study On Effects Of Germination On The Content Of GABA And Edible Quality Of Brown Rice

γ-aminobutyric acid (GABA) is produced by the decarboxylation of glutamic acid underthe catalyzing of glutamic acid decarboxylase (GAD). It is an inhibitory neurotransmitterwhich widely exists in the brain and spinal cord of mammals, and it has lots of importantphysiological functions. In this paper, the brown rice (BR) was taken as experimental material,and the enzymology characteristics of GAD in BR, the best condition for the enrichment ofGABA and the edible properties of germinated brown rice (GBR) was studied. The mainresults are listed as follows:First, investigated the variation of the enzyme activity as the germination time added,and comprehensively researched the effects of different factors on the stability and activity ofGAD in GBR. The activity of GAD increased as the germination time increased. GADreached its maximum activity at40℃and pH5.5, and GAD had relatively high activity in therange of35-45℃and pH5.0-6.0. When the temperature was above60℃, GAD lackedstability and its relative activity decreased below50%. The enzyme was inactivatedcompletely when it was disposed at70℃for1h or80℃for0.5h. GAD was stable at pH4.0-7.0. Effects of2mmol/L metal ions and chemicals on the activity of GAD are as follows:Mg2+、Al3+、Zn2+、Mn2+、EDTA had no significant effect on the activity of GAD. Na+、K+had slight inhibitive effect, and SDS had strong inhibitive effect. Ca2+could promote GADactivity.Second, the experiment of single factor test was used to investigate the effects ofgermination condition and nutrient solution on the content of GABA in GBR. Effects ofdifferent conditions on the content of GABA in GBR were optimized by the experiment oforthogonal test, and the germinated condition that achieved the highest content of GABA wasdetermined. After soaking for12h, the water absorption of brown rice almost reached thesaturation. When the soaking temperature was30℃, moisture was imbibed quickly by theBR and the sensory quality of BR was not affected. The optimum GABA enrichmentcondition of BR: the germination temperature was30℃, the germination time was24h, pHwas5.5, the concentration of MSG was12mmol/L and the concentration of Ca2+was0.5%.Under this condition, the content of GABA in GBR soared to63.34mg/100g. The wholeprocess was suitable for industrialization. Third, compared the cooking properties of different rice, investigated the effects ofsoaking temperature and time on the cooking properties of GBR, and compared the ediblequality of different rice by sensory analysis. Compared with BR, the cooking properties(cooking time, volume expansion ratio, water uptake ratio and gruel solid loss) of GBR had acertain degree of improvement. After soaking for45min, the values of volume expansionratio and water uptake ratio reached the maximum, and the BR did not fragment. As thesoaking temperature raised, the volume expansion ratio, water uptake ratio and gruel solidloss of GBR also increased, and increased rapidly in the range of20-40℃and slowly in therange of40-60℃. The edible quality of GBR was better than that of BR. After soaking at thebest condition, the edible quality of GBR was improved further more, and approximate to theedible quality of white rice.