Cholesterol oxidation products in kefir from goats' milk during storage

Cholesterol oxidation products were identified in goats' whole fat milk kefir when stored under different light sources (500-590 cd) and luminous flux (90-120 Lm). The total sum of cholesterol oxidation products was 1.75 mg kg−1 fat, which after 4 weeks increased to 6.85 mg kg−1 fat. The largest component among the identified oxysterols was 7β-hydroxycholesterol (0.72 mg kg−1 fat), and secondly 25-hydroxycholesterol (0.41 mg kg−1 fat). The storage time and light intensity influenced the formation of 7-ketocholesterol. After 4 weeks at a light intensity of 450 lx, the amount of 7-ketocholesterol in the kefir was 1.92 mg kg−1 fat, and at an intensity of 80 lx it was 0.98 mg kg−1 fat.