Preparation of activated flavor precursor DFG, N-(1-deoxy-1-fructosylglycine) by combination of vacuum evaporation and closed system heating steps

Amadori rearrangement products are potent "activated flavor precursors". This study describes a stepwise optimization of DFG (1-deoxy-1-fructosylglycine) formation from glycine and glucose, varying temperature, water activity a_w, concentration, and ratio/state of precursor mix. In the solid state reaction at 50 °C for 16 h, yield of DFG increased with decreasing water activity with a peak at a_w = 0.22-0.33. In water the conversion was slower and negatively correlated with water activity in the range a_w = 0.8-1. An industrially applicable 2-step vacuum drying and heating process was explored, which first concentrates precursor solution to a_w = 0.5-0.6 and then continues the heating in a closed vessel for an additional 2-4 h. Over 40 mol% conversion from glucose to DFG was obtained on a multi-gram scale. Fine tuning of conditions will be needed for other amino acid/carbohydrate combinations and may offer new perspectives for tailored product flavor generation under moderate heating.