Classification model for detection and discrimination of inedible plastic adulterated palm cooking oil using atr-ftir spectroscopy combined with principal component analysis

Abstract

Adulteration of edible oil by replacing or admixing cheaper or waste oil is an irresponsible act motivated by profiteering. A more sinister act of dissolving inedible plastic materials in hot oil during frying to enhance the crispiness and prolong the shelf life of deep-fried snacks has been alleged. In this study, a protocol using ATR-FTIR spectroscopy combined with principal component analysis (PCA) for detection of inedible plastic materials in palm cooking oil is presented. To achieve this, palm cooking oil samples purchased from convenience stores were heated and adulterated either with low-density polyethylene (LDPE), high-density polyethylene (HDPE) or polypropylene (PP). The resultant spectra from 4000-600 cm-1 were subjected to direct visual examinations prior to PCA. Detection of plastic materials in the samples from direct visual examinations of the resultant spectra was difficult as all samples revealed similar spectra dominated by major absorption bands at 2922 cm-1, 2853 cm-1, 1740 cm-1, 1465 cm-1, 1377 cm-1 and 721 cm-1, which were typical of triacylglycerols. Despite the similarities, the detection was possible when the resultant spectra were subjected to PCA. The results demonstrated the potential of ATR-FTIR spectroscopy combined with PCA for the detection of inedible plastic adulterated palm cooking oil.