Rancid Flavor of Edible Oils. II. Relationship between Rancidity and Fatty Acid Composition

This study aims at to elucidate the nature and chemical component of rancid flavor of oils which are differently oxidized and also to discuss the effect on such rancidities by the different fatty acid composition of oils and by the different extent of the oxidation. The flavors of rancid soybean, corn and olive oil were evaluated by the organoleptic method and the natures of their flavors were described. Although the difference in the quality of rancid flavor in these oils was small, the flavor of each oil was rather characteristic; namely the "green" and "fishy" flavor were predominant in rancid soybean oil , "haylike" flavor in rancid corn oil, and socalled "heavy" flavor in rancid olive oil. The chromatographic analyses on the volatile components of these rancid oils showed that these fractions were mainly composed of the degradation products of linoleic acid. A considerable amount of the decomposition products of linolenic acid were seen in the volatiles of rancid soybean oil, while a small amount of the decomposition products of oleic acid, which were scarcely found in other oils, were detected in the volatiles of rancid olive oil. Slight difference in rancid flavor of these oils appears to depend on the difference in the quantity of volatile compounds and also on the difference in the fatty acid composition of original oils. The intensity of rancid flavor in these oils seems to correlate with their peroxide value and is independent of their fatty acid composition.