Direct discrimination of palm oil as an adulterant in edible oils using a portable Raman spectrometer

Abstract

The common adulteration process in oils involves mixing low-cost and high-cost edible oils. Palm oil has been widely used as an adulterant in the Indian market. In the present work, different ratios of palm oil were mixed with high-cost edible oils such as sunflower, groundnut, coconut, and gingelly. Raman peak intensity for all edible oils individually and after mixing palm oil as an adulterant was studied using a portable Raman spectrometer. The peaks at 838 cm−1, 868 cm−1, 973 cm−1, 1077 cm−1, 1262 cm−1,1300cm−1, 1438 cm−1, 1655 cm-1, and 1745 cm−1 represent vibration due to the (C–C) stretching, (CH) wagging from cis (–CH = CH–), δ(=CH), skeletal C–C stretching, (CH) deformation of (CH2), scissoring vibration of CH2 group, (C=C) stretching from cis –(CH=CH–), and (C=O) stretching vibration from (RC=OOR) for sunflower oil, groundnut oil, gingelly oil, and coconut oil. An attempt has been made to detect 12.5 mL of palm oil in 100 mL of high-cost edible oil. Raman peaks disappeared while adding more than 12.5 mL of adulterate oil. The disappearance of peaks in edible oils, 973 cm−1 for sunflower oil, 970 cm−1 for groundnut oil, 1122 cm−1 for coconut oil, and 1745 cm−1 for gingelly oil respectively. The obtained results will be used for futuristic data analysis to directly detect adulterants in the oils.