Effects of ultrasound on pH, intermediate products, browning, glycin and glucose contents, reducing power, and antioxidant activity of a glycin-glucose solution were examined. Results showed that the ultrasonic treatment at the intensity of 17.83 W/cm 2 for 50 min resulted in the increases of the solution's absorbance at 294 and 420 nm and the antioxidant activity from approximately 0% to 2.40%, 1.19%, and 18.62%, respectively. At the same time, 21% reduction in glycin and 92% in glucose were observed. Gas chromatography/mass spectrum analysis showed that the ultrasonic treatment induced a Maillard reaction in the model system producing substances including 2,5-dimethyl-pyrazine, trimethyl-pyrazine, (Z)-9-octadecenamide, 1,2-benzenedicarboxylic acid, and mono (2-ethylhexyl) ester. This study indicated that ultrasound, especially at higher intensities, could potentially be employed as a means to promote the Maillard reaction in the glycin-glucose solution.

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The formation and degradation of N-(1-Deoxy-d-xylulos-1-yl)glycine and N-(1-Deoxy-d-xylulos-1-yl)proline, derived from the secondary amine Maillard reaction in xylose-amino acid model solutions, were detailed in this study. The identification and quantitative analysis of N-(1-Deoxy-d-xylulos-1-yl)glycine and N-(1-Deoxy-d-xylulos-1-yl)proline were carried out using high-performance anion-exchange chromatography and high-performance liquid chromatography. The formation of intermediate and advanced products derived from N-(1-Deoxy-d-xylulos-1-yl)glycine and N-(1-Deoxy-d-xylulos-1-yl)proline was also tested using an UVVis spectrophotometer to gain a better comparing of the degradation process of the two important Maillard reaction products using thermal treatment. Results showed that the degradation of N-(1-Deoxy-d-xylulos-1-yl)glycine was more significant than N-(1-Deoxy-d-xylulos-1-yl)proline. Moreover, xylose was tested in the degradation products of both N-(1-Deoxy-d-xylulos-1-yl)glycine and N-(1-Deoxy-d-xylulos-1-yl)proline, which indicated that the degradation of N-substituted 1-amino-1-deoxyketoses was a reversible reaction to form reducing sugar.

The content of the intermediate products, browning intensity and amount of 5-hydroxymethyl-2-furaldehyde (HMF) increased with increasing inlet temperature and decreasing pH. Therefore, the amount of sucrose degradation and the change in pH can be used to evaluate caramel properties in the spray drying process. © 2015 Society of Chemical Industry.

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