Changes in HMF content of honey caused during heating and storage were examined.
(1) Only slight increases in HMF content of honey samples were observed when they were heated at 50°C for 24 hours or at 60°C for 10 hours.
(2) Change in HMF content of honey caused by heating was variable depending on the kind of honey sample. Honey samples of lower pH and weaker buffering action were found to produce more HMF on heating.
(3) When honey samples were stored at a low temperature (below 10°C), no increase of HMF contents was observed. When stored at room temperature (May-November), their HMF contents increased only slightly. When stored at 36°C, however, they showed an appreciable increase in HMF content.
(4) Change in HMF content of honey during storage was also variable depending on the kind and quality of honey sample. Domestic honey from Renge-so (Chinese milk vetch) showed less increase in HMF content during storage than did imported honey samples.
(5) The change of HMF added before storage was investigated during storage. When stored at room temp., the amount of HMF decreased first, and at 36°C, it decreased first followed by a gradual increase.
(6) When citric acid was added to honey samples, their HMF contents increased more markedly than that of the control without added citric acid: at higher temperatures, the effect of added citric acid was more pronounced.
(7) Addition of proline or ferric compound to honey samples showed no effect on their HMF contents during storage.