Development of γ-aminobutyric acid (GABA)-rich yoghurt using Tetragenococcus halophilus strain KBC isolated from a commercial soy sauce moromi

Abstract

γ-aminobutyric acid (GABA) has been increasingly incorporated in fermented foods to generate "Superfood". Recently, soy sauce moromi has been proven to contain a microbial strain that can produce an immunostimulatory compound, GABA. In this research, Tetragenococcus halophilus strain KBC (THSKBC) was utilised to ferment milk and enhance GABA production in simplified yoghurt fermentation. Yoghurt fermentation was performed on milk inoculated with THSKBC (F1), yoghurt starter (F2), and THSKBC and yoghurt starter (F3), respectively. The fermentation period of F1 was averaged at 21 hrs compared to both F2 and F3, which was complete after 8 hrs. A spectral HPLC analysis verified that the GABA content of three formulations and yoghurt produced from F3 had the highest GABA concentration of 205.17 mg/L (p <0.05) compared to F1 and F2, which were 78.95 mg/L and 70.31 mg/L, respectively. Thirty panellists were selected for sensory analysis to assess the appearance, colour, odour, taste, texture, and overall acceptability of GABA-yoghurts. The general acceptance of GABA-yoghurts shows F1 and F2 are insignificant (p > 0.05), but F3 was significantly different from commercial yoghurt (p < 0.05). Therefore, this study proved the potential of THSKBC isolated from soy sauce moromi in fermenting milk for GABA-rich yoghurt as future food.