Changes in Maillard reaction products in ghee during storage

Ghee (milkfat from heat clarification) was made using direct cream (DC), cream butter (CB) or pre-stratification (PS) methods and stored at 60 °C, in air, for at least two weeks. Milkfat degradation, particularly oxidation, occurred in all types of ghee, resulting in increases in aldehydes and free fatty acids. However, there was little difference in fat degradation rates in each type of ghee. DC and CB ghee contained volatile Maillard reaction products, whereas PS ghee did not. The concentrations of 3,4-dihydroxy-3-hexen-2,5-dione (DHHD) and 2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one (pyranone), Maillard reaction products found in DC and CB ghee, rapidly decreased during storage, associated with increases in acetic acid. This work suggests hydration of both DHHD and pyranone, during storage, could form reactive 1-deoxy-d-erythro-hexo-2,3-diulose (1-deoxyglucosone) that degrades mostly to acetic acid. Thus, the Maillard reaction cascade appears to continue in food, in the absence of proteins and sugars, long after cooking has ceased.