Enrichment of gamma-aminobutyric acid in foods: From conventional methods to innovative technologies

Gamma-aminobutyric acid (GABA), a non-protein amino acid, possesses various health benefits and plays a signaling and defensive role in plants. Due to the low content of GABA in plant foods, scientists have made great efforts to enrich GABA in foods using various chemical, physical, and biological methods, including anaerobic treatment, cold, salt treatment, germination, microbial fermentation, crossbreeding, and innovative technologies such as ultrasound, ultraviolet, high pressure, etc. To effectively increase GABA in different foods, it is crucial to understand the underlying mechanisms and the virtues and limitations of different enrichment methods that are suitable for different foods. In this paper, we aimed to comprehensively review the recent progress on both conventional and innovative enrichment methods, the advantages and disadvantages, the associated mechanisms, and the applicable foods of these methods. We also summarized the functions of GABA in plants and microorganisms, the factors influencing GABA enrichment, the patents related to GABA enrichment, and the functional foods rich in GABA. The mechanisms of GABA enrichment mainly include modification of cell microstructure; influencing H+ and Ca2+ concentration and enzyme configuration, thereby activating glutamate decarboxylase; and regulation of gene and protein expression of enzymes involved in GABA biosynthesis and metabolism. This review will provide significant information on the production of GABA-enriched foods.