595 Czech J. Food Sci. Vol. 32, 2014, No. 6: 595–600 Degradation of Selected Nutrients in Sunflower Oils during Long-Term Storage Lenka VRBIKOVÁ, Štefan SCHMIDT, František KREPS, Lenka TMÁKOVÁ, Milan ČERTÍK and Stanislav SEKRETÁR Institute of Biotechnology and Food Science, Faculty of Chemical and Food Technology, Slovak University of Technology, Bratislava, Slovak Republic Abstract Vrbiková L., Schmidt Š., Kreps F., Tmáková L., Čertík M., Sekretár S. (2014): Degradation of selected nutrients in sunflower oils during long-term storage. Czech J. Food Sci., 32: 595–600. We investigated the influence of long-term storage (10 months) at an average ambient temperature of 25°C on oxida- tive stability of sunflower oils (made in Slovakia, Czech Republic, Austria, and Hungary) and their nutrients. Chemical properties were determined and changes in oxidative stability monitored. Oil samples were collected and analysed for the content of tocopherols and β-carotene. Degradation of nutrients depends on chemical composition of oils and stor- age conditions. It was found that the concentration of both antioxidants decreased in all the samples with the increase in storage time. According to the results, losses of total tocopherols and β-carotene in refined sunflower oils stored in transparent 5-l PET bottles and exposed to daylight at ambient temperature were found to be 52–64% and 63–65%, re- spectively. The country of origin had no statistically significant impact on the oxidative stability of stored sunflower oils. Keywords: β-carotene; long-term storage; oxidative stability; sunflower oil; tocopherol Lipid oxidation is responsible for a gradual de- crease in nutritional and sensory quality of lipid- containing products (Hrádková et al. 2013). In fact, lipid autoxidation and inadequate storage contrib- ute significantly to the deterioration and reduction of the shelf-life of vegetable oils causing changes in colour, texture, odour and flavour, and loss of vitamins (Milanez & Pontes 2014). Su nflower oil, like most vegetable oils, is composed mainly of triacylglycerols (98–99%) and a small fraction of phospholipids, tocopherols, carotenoids, sterols, and waxes. Regular sunflower oil is characterised by a high concentration of linoleic acid, followed by oleic acid (Grompone 2005). Oxidative stability of sunflower oils depends on their fatty acid composition and presence of antioxidants (Kamal-Eldin 2006). Antioxidants belong to a specific class of chemical compounds that possess the ability to prevent or reduce the rate of oxidative reactions of substrates in food and can thus increase the shelf-life of food products by retarding lipid oxidation (Pokorný & Schmidt 2001). They inhibit oxidation by reacting with free radicals, thus blocking the formation of fatty acid radicals and terminating the chain reaction (Khan et al. 2001). In the reaction, the antioxidant is consumed. When it has been completely consumed, autoxidation starts running as antioxidants are no longer present in the oil (Velíšek 2002a). The important role of vitamin E compounds in food production and commercialisation is preventing lipids and lipid-containing foodstuffs from oxidation during storage, thus extending their stability and shelf-life (Pokorný et al. 2003; Gliszczyńska-Świgło et al. 2007). Their high solubility in oil is caused by a long alkyl side chain (Grompone 2005). Carotenoids are efficient singlet oxygen quenchers, mainly in low concentrations (Kamal-Eldin 2006). β-carotene is an oil-soluble and natural pigment of many oils and Supported by the Slovak Research and Development Agency, Project No. APVV-0850-11, and by the Ministry of Education, Science, Research and Sport, Slovak Republic – VEGA, Grants No. 1/0860/13 and No. 1/0975/12.