Carob Fruit Polyphenols Reduce Tocopherol Loss, Triacylglycerol Polymerization and Oxidation in Heated Sunflower Oil

Heated oils may contain potentially toxic altered compounds. A denatured carob fiber, very rich in non-extractable tannins (Exxenterol®), exhibits antioxidant activities in in vitro experiments. The present study was designed to evaluate in sunflower oil (SO) heated to frying temperature, the protective effect on oil thermal oxidation and polymerization of adding 10 mg Exxenterol/kg oil (SO-10) and 50 mg Exxenterol/kg oil (SO-50). After 2, 8 and 16 h at 180 °C, SO displayed a relevant increase in triacylglycerol-derived polar material (PM) and polymer contents and a decrease in α-tocopherol concentrations. Thermal oxidation changes were significantly checked in SO-50 throughout the 16-h heating, while SO-10 only displayed protection from thermal oxidation during the first 2 h of heating. Oil frying-life was doubled because formation of PM and polymers was inhibited by more than 50%. Results clearly show that this non-extractable tannin-rich fiber can be successfully employed as an additive to significantly prolong sunflower oil frying-life, and thus decrease the potential toxicity of the heated oil.The authors acknowledge the Banco de Santander (Brasil) for the fellowship awarded to Daniele Zulim Botega. Financial support for this investigation was provided by the Spanish Ministerio de Educación y Ciencia Project AGL-2008-04892-C03-02, CSIC-EDOCUSA project, and Consolider-Ingenio 2010, reference CSD2007-00016.Peer reviewe