Analytical, Nutritional and Clinical Methods MIR spectroscopy and partial least-squares regression for determination of phospholipids in rapeseed oils at various stages of technological process Aleksandra Szydłowska-Czerniak * Faculty of Chemistry, Nicholas Copernicus University, ul. Gagarina 7, 87-100 Torun ´ , Poland Received 18 October 2006; received in revised form 29 January 2007; accepted 16 February 2007 Abstract Fourier transform-mid infrared spectroscopy (FT-MIR) and partial least-square (PLS) regression were used for determination of phospholipids (PL) in rapeseed oils at various stages of technological process. The standard error of calibration (SEC) and the standard error of prediction (SEP) were calculated for evaluation of the calibration models. The chemometric calibration model was prepared in spectral region 1760–860 cm 1 for standard PL solutions (1.5–120 mg/mL). Obtained mean concentrations of PL in rapeseed oils at dif- ferent stages of conventional technological operations varied from 22,710 to 224.6 mg/kg. Satisfactory values of precision (RSD = 0.23– 0.73%) and accuracy (recovery – 96.1–101.9%), demonstrate the benefit of the proposed MIR-PLS method in the routine analysis of PL in vegetable oils. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Phospholipids determinations; Fourier transform-mid infrared spectroscopy; Partial least-square regression; Rapeseed oils 1. Introduction The quality of fully refined rapeseed oil is influenced by the quality of crude oil and rapeseeds from which the oil is pressed or extracted. Crude rapeseed oils are constituted mainly of triacylglycerols (TAG) but contain some minor components such as phospholipids (PL), free fatty acids (FFA), sterols, tocopherols, pigments. Besides, trace amounts of metals, flavonoids, and glycolipids may also be present (Gunstone, Harwood, & Padley, 1994). PL have moderate antioxidant activity especially in the presence of phenolic antioxidants and/or acidic synergists. They improve the oxidative stability by chelating trace of heavy metals and by decomposing hydroperoxides (Kourimska, Pokorny, & Reblova, 1994). Moreover, PL have therapeu- tic properties, and they were used to improve human phys- iological and mental performance, lowering cholesterol levels, and treating neurological disorders (Hidalgo & Zamora, 2006). Nevertheless, PL in rapeseed oil are consid- ered as undesirable impurities causing refining problems, oil losses due to the formation of emulsions during the alkali treatment. Therefore, they must be removed from the crude oil at various steps (degumming, neutralization, washing, drying, bleaching, filtration and deodorization) in conventional chemical refining process. There are two chemically different sources of phosphorus: inorganic phos- phates and PL in edible oils. Crude rapeseed oils contain two types of PL: hydratable (HPL) and non-hydratable (NHPL). NHPL, unlike HPL, are phospholipids which during the degumming of crude oil do not hydrate with water, swell, form gels or precipitate from oil and are not separated by centrifugation. Therefore, the PL amounts in crude and refined rapeseed oils must be determined. PL in vegetable oils most often were analyzed by the chromatographic techniques with different methods of sample preparation by solid-phase extraction (SPE) or pre-concentration achieved by column chromatography 0308-8146/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2007.02.038 * Tel.: +48 56 6114786; fax: +48 56 6542477. E-mail address: olasz@umk.pl www.elsevier.com/locate/foodchem Food Chemistry 105 (2007) 1179–1187 Food Chemistry