Effects of microbial transglutaminase treatment on physiochemical properties and emulsifying functionality of faba bean protein isolate

The potential use of microbial transglutaminase (MTG)-treated faba bean protein isolate (FBPI) as emulsifiers to maintain physical and oxidative stability of oil-in-water (O/W) emulsion was investigated. MTG-treated FBPIs (MTG-FBPIs) were prepared by incubating with MTG for 60, 120 or 240 min. O/W emulsions were stabilized by 3% (w/v) of MTG-FBPIs or control-FBPI (treated with inactive MTG) and stored at 37 °C for 7 days. MTG treatments induced cross-linking in FBPI, raised the protein net surface charges by 5%-8%, and increased the emulsion particle size by 19%-135%. MTG treatment for 120 and 240 min but not 60 min induced excessive surface hydrophobicity, resulting in decreased emulsifying activity and physical stability of emulsion. By day 7, all MTG-treated FBPIs showed similar inhibiting effects against lipid oxidation in emulsion, indicated by less conjugated dienes and hexanal production. MTG-FBPIs moderately promoted protein oxidation (120 min > 240 min ≈60 min). Thus, prolonged MTG treatment should be avoided to prevent accelerated protein oxidation and droplets coalescence. MTG treatment for 60 min makes FBPI a potential emulsifier to maintain physical stability while improving lipid oxidative stability in emulsion, potentially attributed to thicker interfacial layer, larger droplet size, and protective effect of protein.