Effects of pH and heat treatment on the stability of γ‐aminobutyric acid (GABA) in germinated soymilk

The effects of food processing on gamma-aminobutyric acid (GABA) losses in GABA solution and germinated soymilk (GSM) were investigated. The different processing steps included variation in pH (2.0-8.0), temperature (70 and 90 degrees C), storage (8 days), and sugar addition (0% and 5%). Results showed that no significant effects of temperature and sugar addition were observed on the GABA content in a GABA solution in a wide pH range (2.0-8.0). However, the temperature caused the loss of GABA in GSM when no sugar was added in a pH range of 4.0-8.0, but this was not observed in GSM with 5% of sugar added at pH 6.5. GSM without sugar addition can be stored at 4 degrees C for 8 days without a decrease in the GABA content. Similarly, GABA was almost stable in the experiment imitating the digestion in stomach in which GSM was adjusted to pH 2 and incubated for 2 hr at 37 degrees C. Practical applications Germinated soymilk is a healthy beverage rich in GABA content. The loss of GABA during heat treatment is inevitable due to the interaction between GABA with other soymilk components. Results of this research revealed that the stability of GABA is different in GABA solution and food matrices.