Esterified propoxylated glycerol soyate, a fat substitute model compound, and soy oil after heating

The changes occurring in two oil samples [EPG-00 soyate (transesterified soybean oil) and soy oil esterified propoxylated glycerol (EPG-08 soyate, a model, fat substitute compound)] were compared after heating at similar to 190 degrees C for 12 h/day. The EPG-00 soyate sample required 48 h of heating to attain a polymer content >20%, while the EPG-08 soyate required only 36 h. After 48 h of heating the EPG-00 soyate sample, the free fatty acid value (FFA) increased from 0.19 to 0.79, the acid value (AV) increased from 0.10 to 1.59, and the p-anisidine value (p-AV) increased from 1.6 to 195.4. In comparison, after only 36 h of heating, the EPG-08 soyate sample had FFA, AV, and p-AV increases from 0.19 to 0.71, from 0.26 to 1.36, and from 1.1 to 191.7, respectively. The triacylglycerol substrate degradation rate for EPG-00 soyate was k = 0.0126 +/- 0.0003 h(-1), while the rate for EPG-08 soyate was k = 0.0166 +/- 0.0017 h(-1). The results suggest that the EPG-00 soyate or transesterified soybean oil is slightly more stable than EPG-08 soyate.