Changes in properties of palm sugar syrup produced by an open pan and a vacuum evaporator during storage.

The aim of this study was to monitor the changes in the properties of palm sugar syrup produced by an open pan and a vacuum evaporator at 70°C and 80°C during storage under 4°C and room temperature (30°C) for 12 months at monthly intervals. During storage, Maillard reaction took place in samples stored under 4°C lower than those stored under 30°C. This was shown by lower a* values, intermediate browning products (IBP), browning intensity (BI) and HMF content, and higher L* values, fructose, glucose and free amino group contents during storage for 12 months. HMF, a possible mutagen formed by nonenzymatic browning during the heating and storage of sugar based products, seems of particular interest and concern. Only the sample produced by an open pan and stored under 30°C contained HMF content (50.58 mg/kg) higher than the permitted maximum limit (40 mg/kg as recommended by the Codex Alimentarious). However, other samples still contained HMF in agreement with this standard. In addition, the microbiological quality and total soluble solids of all samples complied with Thai legislation standards for palm sugar syrup during 12 months of storage.