Evaluation of sterol and triacylglicerol composition during ripening process of the hazelnuts (Corylus avellana L.) grown in Poland

The composition of the hazelnuts’ lipid fraction changes during maturation. This includes the sterols content and occurrence of different types of triacylglycerol (TAG) molecules. From the nutritional point of view, TAGs and sterols content are extremely important. Both, the dietary and technological features of hazelnut oil depend mainly on TAG composition and principal endogenous antioxidants present in nuts. The principal aim of this research was to investigate both, the quantitative and qualitative changes of TAGs and sterols occurring during ripening of Polish hazelnuts. Investigated hazelnuts (var. Webba Cenny, Syrena) were cultivated in experimental orchard in the south of Poland and had been collected for 5 consecutive weeks (August-September). Preliminary vacuum packed nuts were stored in -18°C until they were analysed. Due to free + esterified phytosterols determination, approximately 0.5 mL of dihydrocholesterol (c = 2.0 mg/mL) was added to 250 mg of fat and further analysis was conducted according to Ciemniewska-Żytkiewicz et al. (2015). TAG analysis was conducted by GC-FID with the injection of 1 L of organic solution (3 mg/mL of sample in hexane). The separation was perfomed with a fused silica capillary column (30 m, 0.25 mm i.d., 0.10 mm film thickness.) with 35% dimethyl, 65% diphenyl polysiloxane and a split ratio set at 1:30. The initial oven temperature of 345°C was raised to 352°C at a rate of 0.5 °C min-1 and kept for 3 min. The injector and detector temperatures were set at 360 °C. Hydrogen was used as a carrier gas at a flow rate of 1.75 mL min -1. The Identification was carried out by comparison with a mixture of standards and quantification was achieved by use of an internal standard (tricaprylin, 0.25 mg mL-1). The methodology for the analysis was based on the separation of classes of hazelnut fat TGs according to the total number of carbon atoms