Effect and mechanism of the structure of amino acids and sugar alcohols on browning reaction
The coexistence system of amino acids and sugar alcohols undergoes color browning after long-term storage.However,the relationship between the substrate structure and color change as well as the corresponding mechanism,has not been clarified.This study analyzed the effect of representative amino acid and sugar alcohol species on the browning index in a thermal reaction system(120 ℃,2 h).The accumulation of key intermediates for melanoidin formation was traced with the aid of fluorescence spectroscopy,high-pressure ion chromatography,and liquid chromatograph-mass spectrometer.The reasons for browning differences due to the substrate structure were explored.The results indicated that the browning degree in the system after the reaction of sorbitol with three representative amino acids was greater than that of mannitol.The browning index of sorbitol-lysine was approximately 1.5 times higher than that of mannitol-lysine.It was related to the fact that the carbon atom at the C2 position of sorbitol was located in a more active position and exhibited higher hydro-philicity.Compared with glycine and trimethylglycine,lysine with two amino groups at the ε position not only facilitated the conversion of sorbitol into higher amounts of glucose and fructose,but also led to the accumulation of higher concentrations of colorless intermediates of the Maillard reaction,fluorescent substances,and important precursors of melanoidin such as glyoxal(56.61 mg/L)and methylglyoxal(1.16 mg/L).This study provides a scientific basis for the rational formulation design of products containing sugar alcohols and amino acids.
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