Predictive techniques for authenticating and quantifying crude palm oil adulterated with leaf extract and food color − An ultra-violet visible spectrophotometric approach

Abstract

Analytical techniques such as GC-MS and HPLC are benchmarks for determining vegetable oil adulteration but novel methods of oil manipulation have presented new challenges. In addition to the complexities of sorghum leaf and food color adulteration in crude palm oil (CPO), the sophistication, cost and analytical time of these benchmark methods have elicited the search for alternative approaches. Spectroscopy is one of such approaches that have been lauded for non-invasive and rapid analysis but has never been applied to authenticate CPO containing sorghum leaf extract and food color. This study tested the feasibility of using conventional techniques and UV-Vis spectrophotometry and chemometrics to detect CPO containing different concentrations of food colour and sorghum leaf extract. Linear discriminant analysis models were able to classify different concentrations of sorghum leaf dye and food color in crude palm oil with good accuracy. Testing the developed models with samples from 5 different markets revealed a possible adulteration of some market samples after cross-validation. The purity of crude palm oil could be predicted with an R2CV of 0.937, RMSECV of 0.161 g/100 g and RPD of 3.362 after cross-validation using partial least squares regression and testing 18 different mathematical spectral pretreatment methods. The results suggest a potential for rapid detection of concentrations as low as 0.2 g/mL of food color in CPO and color extract from sorghum leaf size 10 cm by 1 cm.