Influence of solvent nature on L-asparagine – L-arabinose molecular complexes formation under Maillard reaction condition

The study of Maillard reaction mechanisms remains an important problem in food chemistry, one of the aspects of which is the influence of the medium nature on the non-enzymatic browning dynamics. Despite of experimental studies devoted to the influence of solvent nature on the melanoidin formation kinetics, no generalizing patterns have been proposed link-ing the rate of formation of Maillard reaction products with the medium parameters. In this paper, an approach based on the study of molecular conjugation at the initial stages of sugar-amine interactions is proposed: the studies were performed on the model system of L-asparagine – L-arabinose in aqueous, aqueous-ethanol and ethanol media. Using IR-spectroscopy and additional melting pointing estimation, it was shown that conjugation of an amino acid with a carbohy-drate at 50°C for 1 hour with the formation of a molecular complex is realized only in an aqueous medium. Mechanical mixture is isolated from the aqueous-ethanol (1:1) medium under the same conditions, whereas two solid phases crystal-lize from the ethanol solution – ethanol-soluble and ethanol-insoluble, indicating the complete absence of the compo-nent’s interaction. The effect described is probably due to the higher polarity of water (compared to ethanol), which con-tributes to the intensification of intermolecular interactions involving ionic forms of asparagine. Modeling of the Maillard reaction in amino acid–carbohydrate–solvent systems of the same composition at 90°C (1.5 h) shows an increase in the optical density of the studied solutions at 420 nm (increased browning) in the water – water-ethanol – ethanol series. Based on the data obtained, it is concluded that the molecular complex formed in the aquatic environment stabilizes the L-asparagine–L-arabinose system, which prevents the Maillard reaction occurring and the formation of colored products. A detailed analysis of the isolated sugar-amine molecular complex IR spectra shows the involvement of the NH3+-groups of asparagine and the C1-OH anomeric center of arabinose in conjugation, which suggests the universality of the molecular complexation effect of α-amino acids with reducing sugars on the Maillard reaction initial stages: the latter is confirmed experimentally in systems with other reducing carbohydrates (glucose and lactose).