Study On The Preparation Of Nutritional Powder With High γ-Aminobutyric Acid Content From Germinated Brown Rice

Series physiological and biochemical changes occurred in the brown rice (BR) during germination.γ-aminobutyric acid (GABA), which has important physiological functions, was significantly increased after the germination. Previous work in our lab had already established optimized conditions of generating GABA in vitro transformation by adding glutamic acid into germinated brown rice (GBR) slurry. On this basis, the GBR slurry with high level GABA was dried to prepare nutrition powder in the present study. Two indexes, GABA content and GAD activity, was used to screen those of higher varieties among 58 hybrid rice were studied; the changes of the endogenous enzyme activities and GABA conversion capability of brown rice during grain storage period; changes of endogenous enzyme and nutritional ingredient in GBR were investigated in the present study. Furthermore, changes of nutritional ingredients in vitro transformation were assayed. The last part of the present study was that GBR slurry with high GABA content was dried to GBR powder using three different drying modes. This would provide scientific basis for development of GBR food with high level GABA. Main research results were as follows:(1)After brown rice was germinated at 30℃for 72h,the GABA contents and the GAD activities in 58 hybrid rice varieties and other two previously varieties, ZY1X2 and Z944 were determined. Among 58 tested materials, the average GABA level was 141.11 mg/100g, with coefficient of variation equals 21.42%; the average GAD activities was 9.56 U/100g, with coefficient of variation equals 18.38%. Based on a comprehensive analysis, number 10,28,37,48 and 53,were screened for next selection job.In addition, two previous varieties exhibited lower GABA level and GAD activities for relatively longer storage time.(2) Changes of germination qualities of brown rice during grain storage at room temperature. When storage time was prolonged, the germination rate, GAD and phytase activities of germinated brown rice and GABA production significantly decreased. For Z944, grain storage for 14 months at room temperature caused 18.15% decrease of germination rate,6.26% reduction of GAD activity and 20.03% decrease of GABA production after germinated for 72 h. The corresponding indexes have been changed to 55.44%,19.63% and 49.20%, respectively, after the 26 months storage time. When the grain was stored at room temperature more than one year, the BR were unable to meet the requirement of processing and utilization of the GBR food with high level GABA.(3)Changes of endogenous enzyme and nutritional ingredient in BR during germination. Brown rice was germinated at 30℃for 72h,The activities of a-diastase,β--diastase, protease, phytase, GAD and the content of GABA, reducing sugar were increased at a rate of 12.23 fold,6.21 fold,13.89 fold,4.83 fold,6.55 fold,4.22 fold and 11.19 fold respectively, as germination time prolonged, compared with those of the un-germinated ones. However the levels of total sugar, crude protein and fytic acid reduced at a rate of 60.21%、37.60% and 21.92%, respectively. Correlation analysis displayed significant positive correlation between total sugar, reducing sugar level and ofα/β-diastase activities (P<0.01).There was significant negative correlation between crude protein level and protease activity (P<0.01),and positive correlation between free amino acid level and protease activity (P<0.01).The significant negative correlation was found between fytic acid level and phytase activity (P<0.001).(4) Changes of nutritional ingredient in vitro transformation of GBR slurry. The content of GABA maximized at 4h in vitro transformation from 0-8h. The GABA, reducing sugar and free amino acid level of slurry after vitro transformation for 4 h were 549.27mg/100g.3.08mg/g and 500.81μg/g,increased at a rate of 27.87 fold,15.40 fold and 4.09 fold, respectively, compared with those of un-germinated ones; However the content of fytic acid (7.42mg/g) reduced at a rate of 60.48%.(5) Suitable drying mode of GBR slurry with high level GABA. The freeze drying, hot-air drying and microwave drying were used to dried GBR slurry to prepare nutrition powder with high level GABA. Results showed that the less loss of GABA level was found in the freeze drying products. The optimum condition of hot air drying were as follows:temperature 70℃, thickness 2 mm and drying time 60 min, the sensory evaluation of this product was the best. The sensory evaluation of the product prepared from the microwave drying was relative low, for its being easily scorched. The present study established quality standard for GBR powder by reference to the national standard.