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Changes in Oil Quality and Peroxidase Activity during Germination of Rape Seeds and Mustard Seeds
Vegetable oils are selected by consumers based on the presence of multiple bioactive substances, including polyunsaturated fatty acids, sterols, and tocopherols. Another important factor in oils is their quality. This research involved analyzing the oils quality and quantity of bioactive substances obtained from rape seeds and white mustard seeds that underwent germination. The quality of the oils was compared by determining the acid and peroxide values. Germination lowered the peroxide value by 86.3% and 71.4% for rapeseed oil and mustard oil, respectively. This was due to the germination step of the seed use oxygen, which was the substrate for lipid peroxidation. The activity of peroxidase increased by 95% for rapeseed oil and 94% for mustard oil during germination. An increase in the amount of polyunsaturated fatty acids in mustard oil also was noted during germination.
The Effect of High-Temperature Heating on Amounts of Bioactive Compounds and Antiradical Properties of Refined Rapeseed Oil Blended with Rapeseed, Coriander and Apricot Cold-Pressed Oils
Cold-pressed oils are rich sources of bioactive substances, which may protect triacylglycerols from degradation during frying. Nevertheless, these substances may decompose under high temperature. This work considers the content of bioactive substances in blends and their changes during high-temperature heating. Blends of refined rapeseed oil with 5% or 25% in one of three cold-pressed oils (rapeseed, coriander and apricot) were heated at 170 or 200 °C in a thin layer on a pan. All non-heated blends and cold-pressed oils were tested for fatty acid profile, content and composition of phytosterols, tocochromanols, chlorophyll and radical scavenging activity (RSA) analyzed by 2,2-diphenyl-1-picrylhydrazyl (DPPH), and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays. Moreover, the stability of phytosterols, tocochromanols, DPPH and ABTS values was determined in heated blends. All tocochromanols were lost during the heating process, in particular, at 200 °C. However, there were some differences between homologues. α-Tocopherol and δ-tocopherol were the most thermolabile and the most stable, respectively. Phytosterols were characterized by very high stability at both temperatures. We observed relationships between ABTS and DPPH values and contents of total tocochromanols and α-tocopherol. The obtained results may be useful in designing a new type of fried food with improved health properties and it may be the basis for further research on this topic.
Black Cumin Essential Oil as an Active Stabilization Component of Rapeseed Oil During Deep-Fat Model Heating
The aim of this study was to evaluate the potential of black cumin essential oils to reduce the degradation of rapeseed oil during heating. Rapeseed oil was heated without addition and with the addition of black cumin essential oil (200 ppm, 500 ppm, and 1000 ppm), and with synthetic antioxidant TBHQ (200 ppm). The heating was carried out at 170 °C ± 10 °C for 6 h, in a deep-fat heating model. In all samples, changes in fatty acid profile, lipid-nutritional quality indices (PUFA/SFA ratio, atherogenicity index, thrombogenicity index, and hypocholesterolemic/hypercholesterolemic ratio), tocopherol and phytosterol content, total polar compound content, and triacylglycerol polymers were determined. The heating process led to oil degradation, which depended on the amount and type of additive used. The greatest changes were observed in the control sample (without additives). The addition of TBHQ or 200 ppm of black cumin essential oil reduced the adverse transformations to a similar level. Higher additions of black cumin essential oil led to a significant improvement in the quality of heated oils. The best results were obtained with the addition of 1000 ppm of black cumin essential oil.