LEVELS AND FORMATION OF OXIDIZED CHOLESTEROLS IN PROCESSED MARINE FOODS

The contents of oxidized cholesterols in uncooked and processed marine products (air-dried sardine, air-dried squid, canned squid, and pickl ed and spiced Alaskan pollack roe) were measured. Raw fish contained e ssentially no oxidized cholesterols, while the processed products exam ined contained 11.0-28.7 mg/100 g of oxidized cholesterols, and 7alpha -hydroxycholesterol (2.7-3.8 mg/100 g), 7beta-hydroxy-cholesterol (2.8 -9.8 mg/100 g), 5alpha-epoxycholesterol (0.2-5.8 mg/100 g), 5beta-epox ycholesterol (0.7-4.9 mg/100 g), and 7-ketocholesterol (1.9-5.3 mg/100 g) were detected. To know the interaction of lipid oxidation with cho lesterol oxidation, cholesterol was heated with or without various fat s (tristearin, beef tallow, triolein, soybean oil, safflower oil, lins eed oil, and sardine oil) at 100-degrees-C for up to 24 h. Cholesterol was stable, and essentially no oxidized cholesterol was produced when it was heated alone. However, when fats were present simultaneously, cholesterol was unstable, in particular when heated with unsaturated f ats; the content of cholesterol was readily reduced, and oxidized chol esterols were generated shortly after heating. The observations indica ted that lipid peroxidation precedes cholesterol oxidation.