Molecular-weight distributions of degradation products in selected frying oils

Polar isolates of frying oils used for frying French fries, potato chips, o r French fries/tortilla chips were analyzed for nonvolatile components by h igh-performance size-exclusion chromatography (HPSEC) with viscometric (VIS )/refractometric (RI) detection. The degradation products were separated on three mixed-bed polystyrene/divinylbenzene columns with tetrahydrofuran as eluent. Dual VIS/R1 detection of the column effluent enabled simultaneous determination of analyte molecular weights (MW) and concentrations. MW of i ndividual components were calculated from viscosity data with the use of a universal calibration technique. HPSEC of polar samples obtained from diffe rent oilseed lines yielded triglyceride-derived products in which the corre sponding nonvolatile components had variable MW and compositions. Elevated levels of high-MW components were correlated with the extent of frying oil degradation to serve as indicators for frying oil stability. MW/concentrati on profiles of degradation products varied notably with frying times. The d istribution patterns of degradation products were markedly affected by othe r frying conditions and oil varieties and therefore served as fingerprint p roperties of specific oils. High-oleic sunflower oil (HOSUN) (used for fryi ng French fries) appeared to be more stable than cottonseed oil: at 30 h, t he concentrations of the highest MW components were 0.63 vs. 0.89 mg/100 mg oil. HOSUN (used for frying French fries/tortilia chips) tended to be more stable than sunflower oil (SUN), as the most abundant (at 30 h, 3.99 vs. 4 .34 mg/100 mg oil) species were components 4 (MW = 1385) and 3 (MW = 2055) for HOSUN and SUN, respectively, High-oleic soybean oil (HOSBO) was notably more stable than soybean oil: at 40 h, the concentrations of the highest M W (2980 vs. 6315) components were 0.21 vs. 4.51 mg/100 mg oil.