MONITORING THE OXIDATION OF EDIBLE OILS BY FOURIER-TRANSFORM INFRARED-SPECTROSCOPY

Edible fats and oils in their neat form are ideal candidates for Fouri er transform infrared (FTIR) analysis, in either the attenuated total reflectance or the transmission mode. FTIR spectroscopy provides a sim ple and rapid means of following complex changes that take place as li pids oxidize. Safflower and cottonseed oils were oxidized under variou s conditions, and their spectral changes were recorded and interpreted . The critical absorption bands associated with common oxidation end p roducts were identified by relating them to those of spectroscopically representative reference compounds. The power and utilty of FTIR spec troscopy to follow oxidative changes was demonstrated through the use of ''real-time oxidation plots.'' A quantitative approach is proposed in which standards are used that are spectroscopically representative of oxidative end products and by which the oxidative state of an oil c an be defined in terms of percent hydroperoxides, percent alcohols and total carbonyl content. By using either relative absorption as a basi s or calibrating on representative standards, FTIR analysis provides a rapid means of evaluating the oxidative state of an oil or of monitor ing changes in oils undergoing thermal stress.