Monitoring chemical interesterification

Abstract

Chemical interesterification has long been used to modify oils and fats into functional products. Many chemical compounds can be used as the catalysts, such as sodium metal and sodium methoxide. With addition of the catalyst, the oil turns a well documented distinctive reddish brown. Many believe that this color compound may be the real catalyst in interesterification. The spectral changes of an oil undergoing interesterification were examined in the visible and ultraviolet wavelength ranges. An absorbance peak was found from 320–450 nm. Because this range is the wavelength of blue light, this absorption gives the oil a reddish brown color, the compensated color of blue light. The peak increases as the amount of sodium methoxide increases. To initiate and complete interesterification, the oil absorbance must reach levels of 0.4 and 1.0 at 374 nm, respectively. Controlled partial interesterification is now also possible by controlling the absorbance between 0.4 and 1.0. A novel patent-pending technology, based on this observation, was developed to monitor the progress of interesterification on-line using fiber optic technology. The reaction time and the dosage of sodium methoxide used for randomization have been significantly reduced on bench-scale when using this new tool. Furthermore, the oils interesterified with monitoring have higher oxidative stability and tocopherol contents compared to those by conventional randomization.