Cholesterol oxidation in butter and dairy spread during storage.

In a dairy spread (800 g lipid/kg, 10 g salt/kg) based on 750 g milk fat/kg and 250 g rapeseed oil/kg fat in 15 g extruded catering packaging, there was a more significant accumulation of cholesterol oxidation products than in butter (minimum 800 g lipid/kg, 12 g salt/kg) in 10 g extruded catering packaging when stored at 4 or at 20 degrees C. There was a lag phase of 7 weeks in cholesterol oxidation in dairy spread stored at 4 degrees C, while no lag phase was observed for storage at 20 degrees C. Total concentrations of oxysterols were, however, very similar for dairy spread stored at 4 and 20 degrees C after 13 weeks storage (approximately 12 micrograms/g milk lipid); storage at -18 degrees C almost prevented cholesterol oxidation (approximately 4 micrograms/g milk lipid). For butter, cholesterol oxidation was less pronounced at 4 degrees C (<3 micrograms/g milk lipid) than at -18 degrees C (approximately 4 micrograms/g milk lipid) and 20 degrees C (approximately 7 micrograms/g milk lipid). 7-Ketocholesterol was the dominant oxidation product, with 1.3 and 5.7 micrograms/g milk lipid in butter and dairy spread respectively after 13 weeks storage at 4 degrees C.