Unpleasant Odors of Rapeseed Oil Heated to Frying Temperatures

Abstract

Sensory studies by seven to nine trained judges, using a linear scale, indicated that rapeseed oil (RSO) heated to 190C and subsequently smelled at 50C was significantly stronger in odor than sunflower, corn and safflower oils treated with the same heating conditions. The odor of heated soybean oil (SBO) was intermediate in strength. Both RSO odor intensity value (OIV) and thiobarbituric acid (TBA) values increased as the heating time was extended from 0 to 40 minutes. Hydrogénation of RSO sharply reduced TBA values of progressively heated oils and effected some decrease in the development of the odor, however, hydrogénation did not eliminate the odor problem. The OIV's of heated low glucosinolate RSO were more similar to heated SBO odor than were the heated OIV's of high glucosinolate RSO. High and low erucic acid RSO varieties from three processors were compared with chemical odor standards for buttery, sweet, sulfurous, painty and fishy odors. High erucic acid RSO's were significantly lower than low erucic acid RSO's in fishy odor (P < 0.01) and tended to be lower in painty (P < 0.10) and sulfurous odor (P < 0.10). The oils from one processor were consistently, but not significantly, lower in all odor parameters than the oils from the other two processors.