Effect of Fertilizer and Storage Period on Oxidative Stability and Color of Rapeseed Oils

Abstract

We analysed physical and chemical properties of seeds and oils from different cultivars of winter rapeseeds ('Markus', 'Bios' and 'Feliks') that were cultivated using bio-gas natural manure (digestate) or with a commercially accessible Yara NPK 5014-28 (NPK) fertilizer, both of which were analyzed for element content. Seeds produced without use of fertilizers were taken as control. Prior to cold-pressing of oils, seeds were analyzed for fatty acid content. Cultivar 'Bios' breed with use of digestate showed a lower amount of oleic acid (C18:1), while the 'Feliks' cultivar had higher content of this fatty acid and lower amounts of linoleic acid (C18:2) as compared to respective controls. In the case of the application of NPK fertilizer, the increase in C18:1 was observed for the cultivars 'Markus' and 'Feliks'. In the latter the decrease in the content of C18:2 was observed as compared to control. The oils were analyzed monthly for photosynthetic pigment content and oxidative stability as well as color during a storage period of three months. Oils contained similar amounts of chlorophylls and carotenoids. Oils derived from seeds produced with the use of commercial NPK fertilizer were characterized with higher oxidation stability (induction time) as compared to digestate. Gradual darkening of the oils was observed. Statistical analysis (p<0.05) showed significant correlation between all the color parameters and term of measurements as well as with the applied fertilizer.

Impact of the Type of Fertilization and the Addition of Glycerol on the Quality of Spring Rape Straw Pellets

“…The obtained values were 0.119, 0.12 and 5.37 g•dm −1 for nitrogen, phosphorous and potassium, respectively ( Table 1). The content of heavy metals was within the acceptable range, which confirms the usability of the digestate as a crop fertilizer [39,40]. It is also important to note that the elemental analysis of the digestate was comparable to results reported by other authors [41].…”

The Influence of Storage Conditions of Cold-Pressed Rapeseed Oil on Its Quality Parameters

“…Moreover, increases in the parameters a* (redness) and b* (yellowness) were observed. According to Kachel-Jakubowska [16], this may be related to the decomposition of natural dyes. The increase in the a* parameter was solely associated with the breakdown of chlorophylls, which decompose under the influence of UV radiation.…”

“…Almost imperceptible changes in the color of the cold-pressed oil may indicate a deterioration of its quality. Therefore, vegetable oils must be stored in appropriate conditions to protect them against unfavorable factors (i.e., temperature, UV radiation, and oxygen) that could lead to deterioration [15,16]. Vegetable oils are stored in packaging that differs in volume and the material from which it is made.…”