Influence of heating olive oil on the polyphenolic content

Maslinovo ulje je oduvijek bila važna namirnica u mediteranskoj prehrani te se takav način prehrane povezuje s izrazito rijetkom pojavom koronarnih i malignih bolesti. Maslinovo ulje ima veliku prehrambenu, preventivnu pa i terapeutsku vrijednost i stoga je iznimno važno ispitati njegovu kvalitetu koja je usko povezana sa sadržajem polifenolnih tvari u ulju. Također, maslinovo ulje se koristi u različitim postupcima pripreme hrane koji uključuju termičku obradu te je ispitivanje njegove stabilnosti pri povišenim temperaturama također neophodno. Različite se analitičke tehnike koriste za određivanje sadržaja ukupnih polifenola u maslinovim uljima, a uključuju dva osnovna koraka: ekstrakciju iz uzorka maslinovog ulja i kvantifikaciju. U ovom radu ispitivane su dvije tehnike ekstrakcije, ekstrakcija tekućetekuće (engl. Liquid-Liquid Extraction, LLE) i disperzivna ekstrakcija čvrstom fazom (engl. Dispersive Solid Phase Extraction, dSPE), tj. QuEChERS (engl. Quick, Easy, Cheap, Effective, Rugged, Safe) tehnika. Osim toga, mjerio se i sadržaj ukupnih polifenolnih tvari u ispitivanim maslinovim uljima prije i nakon zagrijavanja na 50 ˚C. Rezultati su pokazali da je ekstrakcija tekuće-tekuće prigodnija za ekstrakciju polifenolnih tvari iz maslinovog ulja zbog nešto većeg prinosa. Udio ukupnih polifenola postupno se smanjivao s vremenom zagrijavanja.Olive oil has always been important part of the Mediterranean diet, associated with an extremely rare occurrence of coronary and malignant diseases. Olive oil has a great nutritive, preventive and therapeutic value and therefore it is very important to examine its quality, which is closely associated with the total polyphenolic content of the oil. Also, olive oil is used in a variety of procedures of food preparation, which includes thermal treatment, and testing its stability at elevated temperatures is also necessary. Different analytical techniques are used to determine the total polyphenolic content in olive oils, and they include two basic steps: extraction from a sample of olive oil and quantification. In this study the two techniques for extraction of polyphenolic compounds from olive oil were used, liquid-liquid extraction (LLE) and solid phase dispersion extraction (DSPE), ie. QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) technique. In addition, the total polyphenolic content was tested before and after heating olive oil samples at 50 °C. The results showed that the liquid-liquid extraction is more appropriate for extraction of polyphenolic compounds because it showed slightly higher yields. Finally, the value of total polyphenolic content gradually decreased with heating time