Low vs high field ¹h NMR spectroscopy for the detection of adulteration of cold pressed rapeseed oil with refined oils

Cold pressed rapeseed oil (CPRO) is a relatively recent development in rapeseed processing, which produces a quality product with a high market value. High field NMR (400 MHz) is a well-established tool in food analysis, while low-field NMR (60 MHz) is much less studied. This study aims to establish the effectiveness of both techniques in identifying binary adulteration in CPRO. Three adulteration scenarios were investigated: a) CPRO and refined rapeseed oil (RRO); b) CPRO and refined sunflower oil (RSO); and c) CPRO and RRO or RSO. A range of classification techniques were trialled as well as partial least squares regression to gauge predictive quantification performance. The 400 MHz NMR achieved classification rates of 100% in the scenarios with a single adulterant, and 93% in the multiple adulterant scenario. The 60 MHz NMR produced lower but still encouraging classification rates (RSO 92%; RRO 85%; both RRO and RSO 87%).