Chemical composition of sesame (SEO), rice bran (RBO) and bene hull (BHO) oils was determined. During oven test, peroxide value on day 8 (PV 8 , meq/kg) and carbonyl value on day 6 (CV 6 , mmol/g) were considered as measures of resistance to the formation of primary and secondary oxidation products, respectively. The SEO and BHO showed statistically the same PV 8 (381.4 and 359.8, respectively) and CV 6 (25.2 and 25.8, respectively), and their stabilizing effect was significantly better than that of the RBO (455.5 and 32.7, respectively). The unsaponifiable matters (USM) fraction of the BHO (443.7 and 26.8, respectively) had an antioxidative effect higher than those of the SEO (478.0 and 38.6, respectively) and RBO (482.4 and 37.4, respectively). There was a good correlation (R 2 ¼ 0.972) between the PV 8 and CV 6 throughout oxidation period. On the basis of the oxidative stability index (OSI, h) of Rancimat test, the best carry-through properties belonged to the SEO (6.92 h), followed by the RBO (6.12 h) and BHO (5.0 h), and also a similar order was observed for the USM fractions (5.89, 5.28 and 4.50 h, respectively). There was no correlation between the results of Rancimat and oven tests, showing that the powerful antioxidative agents under oven test conditions were lack of appropriate carry-through properties. The highest significant reducing power (mmol/L) belonged to the SEO (258.1), followed by the RBO (218.7) and BHO (152.4), whereas the USM fraction of the SEO indicated the least significant quantity among the USM fractions (89.3 vs. 216.6 and 158.0 for the RBO and BHO, respectively).
A primary Fourier transform infrared (FTIR) method was developed to determine the hydroxyl value (OHV) of polyols produced from edible oils. The method is a modification of American Society for Testing and Materials 1899-08, using toluene as the solvent to dissolve the sample and to carry the reactive reagent p-toluenesulfonyl isocyanate (TSI). TSI reacts with OH groups to produce a carbamate, a functional group that can be measured spectrally between *1780 and 1690 cm -1 in the differential spectrum that is obtained from spectra collected before and after the reaction. Commercially available 1-nonanol, which has a defined OHV, is used to develop a calibration. The OHV for a variety of 1°and 2°alcohols, as well as petrochemical and lipidbased polyols, were then measured to evaluate the performance of the method and to assess the effects of moisture on the results. The FTIR OHV were in accord with the results obtained by AOCS method Cd 13-60 and were demonstrated to be unaffected by the presence of moisture in the sample. The new TSI-FTIR method is simpler, much faster (*10 min), and more reproducible and accurate than the AOCS OHV titrimetric methods and is not affected by carboxylic acids, amines or moisture.
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