EFFECTS OF STORAGE OR HEAT-TREATMENT ON O XYSTEROLS FORMATION IN DAIRY-PRODUCTS

Effects of some processing and storage conditions and cooking treatmen t on oxidation of cholesterol in commercial dairy products were invest igated. No or only low traces of oxysterols were detected in fresh che eses, butter oil and milk powder or after storage at low temperature b y avoiding Eight and oxygen. Melting of cheeses (raclette) does nor pr oduce oxysterols, but heating butter oil for 30 min at 170-175 degrees C or more than 10 min at 205-210 degrees C generated some oxysterols. Exposure of cheeses to fluorescent light for 2-4 months at 6 degrees C (cool white) and storage of milk powder with an a(w)-value of 0.11 i n a oxygen containing atmosphere (660 mL/L) for one year at 30 degrees C oxidized 10 to 15% of their cholesterol. Consequently, the present work confirmed the good stability of cholesterol in dairy products und er correct conditions of storage or heat treatment. The harsh conditio ns considered in this study correspond to those of accelerated tests.