Influence of high‐pressure processing on the generation of γ ‐aminobutyric acid and microbiological safety in coffee beans

BACKGROUND The aim of this study was to investigate the influence of high‐pressure processing (HPP) on γ ‐aminobutyric acid (GABA) content, glutamic acid (Glu) content, glutamate decarboxylase (GAD) activity, growth of Aspergillus fresenii , and accumulated ochratoxin A (OTA) content in coffee beans. RESULTS The results indicated that coffee beans subjected to HPP at pressures ≥50 MPa for 5 min increased GAD activity and promoted the conversion of Glu to GABA, and showed a significantly doubling of GABA content compared with unprocessed coffee beans. Additionally, investigation of the influence of HPP on A. fresenii growth on coffee beans showed that application ≥400 MPa reduced A. fresenii concentrations to <1 log. Furthermore, during a 50‐day storage period, we observed that a processing pressure of 600 MPa completely inhibited A. fresenii growth, and on day 50 the OTA content of coffee beans subjected to processing pressures of 600 MPa was 0.0066 μg g −1 , which was significantly lower than the OTA content of 0.1143 μg g −1 in the control group. CONCLUSION This study shows that HPP treatment can simultaneously increase GABA content and inhibit the growth of A. fresenii , thereby effectively reducing the production and accumulation of OTA and maintaining the microbiological safety of coffee beans. © 2018 Society of Chemical Industry