Flavor binding property of coconut protein affected by protein-glutaminase: Vanillin-coconut protein model

Flavor compounds added to food products can interact with protein and may result in a reduction in flavor intensity. The objective of this study was to study the effect of enzymatic deamidation by protein-glutaminase (PG) on the flavor-binding potential of coconut protein (CP) using a vanillin flavor model. Vanillin was allowed to interact with either 3 g/100 mL of untreated or deamidated CP (DCP) suspended in 0.05 mol/L phosphate buffer. The results showed that deamidation by PG decreased overall flavor-binding affinity of vanillin to the protein from 586 to 985 ( × 10⁴) L/mol to 435–803 ( × 10⁴) L/mol. Thermodynamic parameters indicated that the vanillin-protein interactions were spontaneous and the interactions were driven by enthalpy. Beside Schiff-base formation, van der Waals forces or hydrogen bonding were suggested to be involved in the binding mechanism. The lower binding affinity for vanillin for DCP than for CP was confirmed by a sensory threshold study, which showed that vanillin had about a 2 fold lower odor detection threshold in DCP solution than in CP solution.