Effect of pre-fermentation treatments and fermentation conditions of red beans on γ-aminobutyric acid (GABA) production by lactic acid bacteria
Date Issued
2009
Date
2009
Author(s)
Liao, Wan-Chug
Abstract
The Adzuki bean Kaohsiung 8 was applied to produce fermented functional beverage. The pretreatments/fermentation processes of Adzuki bean Kaohsiung 8 in enrichment of GABA were investigated. The methods for qualitative and quantitative analyses of GABA by HPLC were established. The GABA was extracted from fermented broth or red bean with 70% cold EtOH, derivatized to PICT-GABA with PICT, and then was subsequently separated with C18 separation column (Alltima C18 5U, 250 × 4.6 nm). The content of GABA was determined with UV absorbance detector at 254 nm. Under the condition described above, the HPLC separation gave a well-resolved and symmetrical PITC-GABA peak. The retention time was 11 min and reproducible. Peak area values showed good reproducibility with relative standard deviation (RSD) values at 1.77%. The calibration curve for PITC-GABA was calculated by linear least-squares squares regression. The regression equation was Y = 600000000X + 103248 (R2 = 0.9996) when the initial GABA concentration in the range 0~0.0075 mg/ml. The result indicated that the method described was specific and useful for the determination of GABA in the red bean sample and fermented broth. The GABA content in Adzuki bean Kaohsiung 8 could be enriched effectively by following three pre-fermentation treatments：immersing, germinating and cold shock. The highest GABA content, 201.23 mg/100 g was obtained by immersing red bean in water at 35℃ for 24 h, freezing at -20℃ for 24 h, and then thawing at 30℃ for 24 h. The GABA content of red bean increased 150 fold by this cold shock treament compared to non-treated red bean. The optimum fermentation bacterial seed culture was 2% mixture of Lactococcus lactis subsp. lactis and Lactobacillus rhamnosus GG. The optimum medium constitution was as follows: sucrose 4% (w/v), yeast extract 4% (w/v); and the fermentation condition were as follows: initial pH 6.8, temperature 30℃, fermentation time 24 h. The yield of GABA after optimization reached 65.77 mg/100 ml that increased by 19-fold compared to non-optimization. The GABA contents in improved fermented red bean had little changed between the day 0 and day 28 stored at 4℃: It increased gently in first 12 days. The GABA content of fermented red bean (68.21 mg/100 ml) increased 20 fold by this improved red bean substrate and condition compared to non fermented red bean.
Subjects
red bean
γ-Aminobutyric acid (GABA)
Lactococcus lactis
Lactobacillus rhamnosus
pre-fermentation treatments
cold shock method
fermentation condition
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