Reasons for the High Proportion of Pheophytin in Edible Plant Oils

Abstract

To reduce the pheopytin (Phy) level in oils, it is necessary to understand the reasons of the high proportion of Phy in refined edible oils. In this investigation, the compositional changes in chlorophyll (Chl) and Phy during extraction and some refining processes were evaluted by photofluorometric analysis.The composition of Chl pigments in crude oils was examined when Canola seed oil was extracted with 6 kinds of organic solvents. The proportion of Phy was found to be the highest (97%) in oil extracted with n-hexane, but 38% in hexane-ethanol (3 : 1) extracts, and 13 % in chloroform-methanol (2 : 1) extracts. Especially, when the residue following extraction with n-hexane was further extracted with chloroform-methanol (2 : 1), the proportion was only 3%. From these results, it is concluded that the use of n-hexane as a solvent reduces the extraction of Chl from oil seeds.Next, Canola seed oil was extracted with n-hexane for different extraction times and at different temperatures. Moreover, the changes in Chl during acid treatment of the crude oil were investigated in a model system. A portion of the Chl was converted into Phy during heat or acid treatments. However, in our previous study, a relatively constant compositional ratio between Chl pigments was observed in rapeseed oils throughout the process of mass production. The conversion of Chl to Phy during heat or acid treatment in model experiments may thus be assumed insignificant in practical refining for mass production.