Measurement of degradation of the lipid fraction in margarines

The aim of this investigation was to measure the extent of oxidative and hydrolytic degradation of commonly marketed margarines by separating and determining the polar compounds of the fat fraction and evaluating the classes of substances they contained. The analytical techniques used were silica gel chromatography for the polar compound separation and high-performance size-exclusion chromatography (HPSEC) for the determination of the single classes of substances forming them. Routine analyses were also carried out, and the fatty acid composition and trans isomer contents determined to provide a more comprehensive characterisation. The results obtained showed a considerable variability in the fatty acid composition due to the use of fats and oils from different vegetable sources and the different hardening processes used for the vegetable fat stock in manufacturing the margarines. The results of the analyses sometimes showed a high trans isomer content with values exceeding 25%. The overall level of lipid degradation in the margarines was estimated by determining the polar compounds. The HPSEC analyses of the polar compounds provided measurements of triglyceride oligopolymers, oxidised triglycerides and diglycerides, which are considered to be reliable parameters for evaluating the quality of edible fats and oils