ORIGINAL PAPER Changes in Tocochromanol Content in Seeds of Brassica napus L. During Adverse Conditions of Storage Marzena Gawrysiak-Witulska • Aleksander Siger • Jolanta Wawrzyniak • Malgorzata Nogala-Kalucka Received: 26 November 2010 / Revised: 24 February 2011 / Accepted: 28 February 2011 / Published online: 17 March 2011 Ó AOCS 2011 Abstract Tocopherols and plastochromanol-8 were evaluated in seeds of Brassica napus L. during adverse conditions of storage at different temperatures (25 and 30 °C) and moisture levels (10, 12.5 and 15.5%). Both temperature and moisture content of seeds had a significant effect on the hydrolysis of triacylglycerols in rapeseed oil and on the contents of tocopherols and PC-8. The biggest losses of tocopherols (a drop by 14.4% after 18 days) were recorded for seeds with a moisture content of 15.5% and stored at a temperature of 30 °C. Losses of the a-T homologue were bigger than those of c-T. The loss of PC-8 ranged from 4 to 24% depending on storage conditions and it was almost two times bigger than the loss of tocopherols. Keywords Rapeseed  Tocopherol  Plastochromanol-8  Degradation of tocopherols  Postharvest Introduction Rapeseed oil is considered to be one of the most valuable plant fats. It is a rich source of mono- and polyenoic acids [1] and natural antioxidants—tocopherols, plastochro- manol-8 (PC-8), phenolic compounds and sterols [2]. Tocochromanols and PC-8 determine lipid stability in stored seeds [3]. Oxidation of edible oils containing poly- enoic fatty acids is a considerable problem for the food industry due to the direct relationship with economic, nutritional, flavor, and storage factors. Oxidation products formed in the course of this process (free radicals, lipid peroxides, aldehydes, ketones, etc.) affect human health [4]. Types and amounts of individual oxidation products in oils depend on the fatty acid composition, storage condi- tions, particularly temperature, availability of oxygen, and light. The main factor limiting lipid oxidation is the pres- ence of natural antioxidants [5, 6]. An important group of native antioxidants found in rapeseed comprises tocopherols. Four homologues, i.e., a-, b-, c- and d-, of tocopherol (T) are present in rapeseed, but a-T and c-T contents amount to 800 mg/kg oil, while the other two are found in trace amounts [7, 8]. Antioxidant properties of tocochromanols depend on their concentra- tion, type of substrate, solvent, light and temperature as well as other chemical compounds exhibiting a pro- oxidation action (ions of transition metals) and synergistic action (phospholipids, ascorbic acid, polyphenols) [9]. This has been shown by numerous studies conducted using different fat substrates under different conditions (temper- ature, light, oxygen) [10–12]. Gopalakrishnan et al. [13] investigated the effect of storage (room temperature and cold room) on chemical changes in lipids, including contents of tocopherols in comminuted rapeseeds. Gawrysiak-Witulska et al. [14] in their studies determined the effect of post-harvest proce- dures (near-ambient drying) on changes in tocopherol contents and plastochromanol-8 in rapeseeds. In turn, Goffman and Mo ¨llers [15] investigated the effect of tem- perature (5, 20 and 40 °C) and availability of oxygen during storage on contents of tocopherols and plastochromanol-8 in intact rapeseeds and in oil pressed from these seeds. M. Gawrysiak-Witulska (&)  J. Wawrzyniak Institute of Technology of Plant Origin Food, Poznan University of Life Sciences, Wojska Polskiego 31, 60-637 Poznan, Poland e-mail: wima@up.poznan.pl A. Siger  M. Nogala-Kalucka Department of Food Biochemistry and Analysis, Poznan University of Life Sciences, Poznan, Poland 123 J Am Oil Chem Soc (2011) 88:1379–1385 DOI 10.1007/s11746-011-1793-0