Changes in the initial stages of a glucose-proline Maillard reaction model system influences dairy product quality during thermal processing

The Maillard reaction always occurs during the thermal processing of dairy products, which significantly influences their quality. In the present study, the initial stages of a glucose-proline model system were investigated in water and different types of buffer solutions. Results showed that phosphate buffer accelerated the reversible degradation of the initial stages of the reaction. The proposed catalysis mechanism was that hydrogenous and dihydric phosphate radical anions simultaneously accepted and donated protons for the conversion of the intermediates into N-glycosylamine. The catalysis mechanism was confirmed via testing and no reducing of hydrogenous and dihydric phosphate radical anions was observed during the reaction. Moreover, both N-(1-deoxy-d-fructos-1-yl)proline and its degradation compounds were analyzed. Results showed that degradation of N-(1-deoxy-d-fructos-1-yl)proline to form 5-hydroxymethyl-2-furaldehyde and formic acid was also accelerated by phosphate buffer. An interesting phenomenon was that citrate decreased 5-hydroxymethyl-2-furaldehyde formation, which might be because Strecker-type degradation occurred more easily than 1,2-enolization reaction in citrate buffer solution. However, this hypothesis has not been confirmed, and element label experiments should be carried out in the future.