The influence of refining process on the polyphenolic compounds of rapeseed oil

Rafinaciju je potrebno provesti kako bi se uklonili sastojci koji umanjuju senzorska svojstva i održivost ulja. No rafinacijom se uklanjaju i neki vrijedni sastojci iz ulja, među kojima su i polifenoli. Cilj ovog rada bio je istražiti utjecaj procesa rafinacije na polifenolni sastav ulja uljane repice. U uzorcima ulja izuzetim iz svake od faza rafinacije određivan je sastav i udjel polifenolnih spojeva pomoću tekućinske kromatografije uz različite metode detekcije. Rezultati su pokazali da je najzastupljeniji polifenolni spoj sirovog ulja uljane repice kanolol, derivat sinapinske kiseline, dok je fenilindan, spoj koji nastaje dimerizacijom kanolola, najzastupljeniji polifenolni spoj jestivog ulja uljane repice. Sirovo ulje uljane repice sadrži značajno više ukupnih polifenola od ostalih analiziranih ulja, čak 10 puta više od jestivog ulja. Do najvećeg gubitka polifenolnih spojeva došlo je u procesima neutralizacije i deodorizacije. U procesu neutralizacije udjel kanolola smanjio se za čak 80%, a dolazi do formiranja fenilindana čime se može djelomično objasniti tako veliki gubitak kanolola. U daljnjim procesima rafinacije uočen je dodatni gubitak polifenola, i to prvenstveno kanolola čiji je udjel u jestivom ulju zanemarivo nizak. Može se zaključiti da je fenilindan, zbog puno manjeg gubitka, stabilniji spoj.Refining is conducted to eliminate components that reduce organoleptic properties and stability of oil. On the other hand, refining can remove some valuable components on oil, such as polyphenols. The aim of this study was to investigate influence of the refining process on polyphenolic composition of rapeseed oil. Polyphenolic composition of crude rapeseed oil and oil obtained after each stage of refining were determined using liquid chromatography with various detection methods. Results showed that dominant polyphenolic compound of the crude rapeseed oil was canolol, derivate of sinapic acid, while phenylindane, dimere of canolol, was dominant polyphenolic compound of the edible rapeseed oil. Crude rapeseed oil contains significantly more total polyphenols than other oil samples, even 10 times more than edible rapeseed oil. The greatest loss of polyphenolic compounds was observed in the processes of neutralization and deodorization. The content of canolol in the process of neutralization declined 80% which can partially be explained by formation of phenylindane. Bleaching and deodorization further reduce the content of polyphenols in rapeseed oil, especially of canolol whose content in the edible oil is negligible. Because of much lower loss of phenylindane in processes of bleaching and deodorization, one could conclude that phenylindane is more stable compound