CORRELATION BETWEEN NMR PROTON RELAXATION-TIME AND FREE FATTY-ACIDS AND TOTAL POLAR MATERIALS OF DEGRADED SOYBEAN OILS

The objective of this study was to determine if a correlation exists b etween NMR proton relaxation times and the increase in free fatty acid s and polar materials in soybean oil as it is degraded. Soybean oil wa s degraded by heating only and by frying corn tortilla dough for 10 mi n/h up to 50 h. Samples were collected every 10 h. Both analytical che mistry methods and nuclear magnetic resonance techniques were used to determine the extent of oil degradation. Results showed that free fatt y acids (FFA) and total polar materials (TPM) increased as heating rim e increased, The longitudinal relaxation time (T-1) and the transverse relaxation time (T-2) decreased as oil degradation increased. There w as a linear relationship between NMR measurements and analytical chemi stry measurements. As the prices of NMR equipment decrease, NMR techni que could be a promising tool for on-line oil quality control in deep fat frying processes.