MOLECULAR-WEIGHT AVERAGES AS CRITERIA FOR QUALITY ASSESSMENT OF HEATED OILS AND FATS

A simple method for quality assessment of heated oils and fats is described. The proposed method involves precise determination of molecular weight averages (MWA) viz., the weight average molecular weight (MwBAR), the number average molecular weight (MnBAR) and the Z-average molecular weight (MzBAR) by high performance size exclusion chromatography (HPSEC) and their quantitative correlation to percent polar material obtained by column chromatography (CC). Change in MWA on heat treatment of fourteen different edible oils and fats at 180-degrees +/- 2-degrees-C for eight 8-hr days is studied. Relative standard deviations and regression coefficients of correlation between MWA and their ratios (MwBAR, MnBAR, MzBAR, MzBAR/MnBAR, MwBAR/MnBAR and MzBAR/MwBAR) vs percent polar material have been reported. Probable discard time was predicted for all the oils based on the above-mentioned correlations and also from the percent of high molecular weight (H. Mwt) species formed. It was observed that the oils which are generally recommended for coronary patients deteriorated faster. A possibility of extending this methodology to the frying oils is suggested.