Systematic isolation and identification of minor components in heated and unheated fat

Abstract

Although animal studies have shown that the chemical reactions occurring in fats during frying do not make them unsuited for food use, questions continue to arise about the products of these reactions and their significance. The purpose of this work was to identify as many as possible of the monomeric products that form when fats are heated in the air. Cottonseed oil was kept at 182 C for six 8 hr days; then it was converted to methyl esters. The distillable, non-urea-adductabte fraction (DNUA) of the esters was separated into 96 fractions by gradient elution chromatography on silica gel. Each fraction was analyzed by gas liquid chromatography (GLC). One hundred thirty-six components were observed, corresponding to 0.42% of the fat. Many of the components were isolated by preparative GLC. Fiftyone were partially or completely characterized. The most abundant components of the DNUA were octadecenoate and octadecadienoate which had not been removed completely by urea adduction. Esters of alicyclic fatty acids made up 34% of the characterized material. These cyclic materials are probably responsible for the toxic effects that have been seen when DNUA was isolated and fed to rats at high dietary levels. Many of the other components appear to be of little biological interest. No components present in substantial amounts remain uncharacterized.

Cyclic fatty acid monomers from dietary heated fats affect rat liver enzyme activity

“…Liver enlargement with accumulation of lipid was detected in animals fed 0.15% CFAME in their diets. In addition, there are reports in the literature that toxic compounds formed during deep-fat frying may cause deleterious effects on rats when ingested through heated fats (12)(13)(14). The complete isolation and purification of cyclic fatty acid monomers (CFAM) were accomplished by Rojo and Perkins (15,16) as well as Sébédio et al (17).…”

Effects of thermal oxidation on the constitution of butterfat, butterfat fractions and certain vegetable oils

“…A relatlonshlp between the nonvolatile, non-urea-adduct-formlng fraction of therméïly oxidized vegetable ails and various taXIe responses has been suggested by '\ the animal experiments conducted by Crampton et al (1953Crampton et al ( , 1956). The , 0 work of subsequent researchers (Michael et al, 1966;Artman, 1'969;Artman and Smith, 1972;Ohfugi and Kaneda, 197? ) supports these flndlngs and suggests that the nonadductable mono~ers (cyclic monomers) and oXldative dimers ar~ the main source of toxic'ity.…”

The effects of cyclic fatty acid monomers on cultured porcine endothelial cells

“…The formation of these partially degraded lipid products can be attributed to the exposure of the frying medium to water (from food), oxygen, metals (from food or equipment), and the high temperature of the frying process (10,11). Various lipid breakdown products have been identified in frying fats and oils derived from both animal and vegetable sources (12,13) and are absorbed by the fried food (14)(15)(16). If a frying medium has been abused and overused, accumulation of lipid breakdown products can be significant (17,18).…”