Interaction of Light and Temperature on Tocopherols During Oxidation of Sunflower Oil

Influences of Illumination Pretreatment on Soybean Oil Activated Clay Bleaching Effects and Soybean Oil Quality Evaluation

Visible light has been widely studied for possible applications in food industry as being a kind of clean energy. Presently, the influences of illumination pretreatment on soybean oil quality followed by conventional activated clay bleaching, including the oil color, fatty acid composition, oxidation stability, and micronutrient content, were investigated. Results demonstrated that the illumination pretreatment increased the color differences between the non-illuminated and illuminated soybean oils, which indicated that the light exposure could improve the decoloring effects. The fatty acids composition and the peroxide value (POV) and oxidation stability index (OSI) of the soybean oils showed little changes during this process. Although the illumination pretreatment affected the content of lipid-soluble micronutrients, including phytosterols and tocopherols, no significant differences could be observed (p > 0.05). Moreover, it showed that the illumination pretreatment showed significant effects for decreasing the following activated clay bleaching temperature, indicating the energy saving potential of this novel soybean oil decoloring process. The present study might provide new insights for developing eco-friendly and efficient vegetable oil bleaching technology.

Evaluation of the Efficacy and Synergistic Effect of α- and δ-Tocopherol as Natural Antioxidants in the Stabilization of Sunflower Oil and Olive Pomace Oil during Storage Conditions

Tocopherols are natural bioactive compounds with several health benefits. This study evaluated the effect of different ratios of α- and δ- tocopherol homologs to protect sunflower oil (SO) and olive pomace oil (OPO) against oxidation. A synergistic effect was recorded when the two tocopherols were combined at a ratio of 7:1 (α-T/δ-T). The oil samples were exposed to accelerated oxidation conditions using a Rancimat (90 °C and airflow of 15 L/h for 24 h) and protection from tocopherols was compared with that from butylated hydroxytoluene (BHT). Assessment of oil stability was examined using well-known parameters such as peroxide value (PV), thiobarbituric acid reactive substances (TBARS), p-anisidine value (p-AV), conjugated dienes (CD) and trienes (CT), and total oxidation (Totox) value, which were all significantly reduced when tocopherols were added at a ratio of 7:1 α-T/δ-T. Primary oxidative compounds measured according to PV were only reduced in SO samples (6.11%). Off-flavor compounds measured via TBARS assay in SO samples were reduced by above 20%, while p-AV was also reduced. CDvalue was correlated with PV in SO samples, while the 7:1 mixture was more effective than BHT for CTvalue. Total oxidation values in SO samples and OPO samples were reduced by 6.02% and 12.62%, respectively. These values in SO samples also provided a remarkable correlation (R2 > 0.95) with incubation time. Moreover, the synergistic effect was not only effective in reducing the oxidation values of oil samples, but also in lowering the degradation rate of tocopherols. Protective effects from tocopherols were mainly observed in SO samples, as OPO samples were more resistant to oxidation processes. This effect was even observed in fatty acid analysis, where the 7:1 mixture provided better results than BHT-spiked samples. Thus, it is suggested that tocopherol mixtures might be used as a natural preservative in the food industry to restrain lipid oxidation processes.

The effect of temperature on the phenolic content and oxidative stability of o/w emulsions enriched with natural extracts from Satureja thymbra

Sunflower oil-in-water emulsions were enriched with two Satureja thymbra extracts - obtained by ethyl acetate (EAcs) or ethanol (Es), rosmarinic acid (RA), or quercetin (Que), and the effect of storage temperature (5-40 °C) on the emulsions' phenolic content and oxidative stability was studied. HPLC analysis of the extracts indicated RA as the main component. The phenolic content of the emulsions decreased during storage, following first-order kinetics, with a temperature-dependent rate. RA was the main compound that decreased, Que followed a slower decrease and the rest flavonoids remained almost constant. The additives protected the emulsion against oxidation according to the order Es > Que > EAcs > RA. The protection factor ranged from 73 to 81% at 5 °C, but decreased to around 53% for Que and Es, 33% for EAcs, and 22% for RA at 40 °C. Emulsions enriched with extracts from S. thymbra retain their phenolic content and oxidative stability at refrigeration temperatures.

Thermo-Oxidation of Phytosterol Molecules in Rapeseed Oil during Heating: The Impact of Unsaturation Level of the Oil

Phytosterols are naturally occurring substances in foods of plant origin that have positive effects on the human body. Their consumption can reduce the level of low density lipoprotein (LDL) cholesterol. The presence of unsaturated bonds in their structure leads to their oxidation during production, storage, and thermal processes. The aim of the study was to determine how the degree of unsaturation of rapeseed oil affects the oxidation of phytosterols in oil during 48 h of heating. In all not-heated oils, the dominant groups of oxyphytosterols were 7α- and 7β-hydroxy sterols. During 48 h of heating, the rapid decrease of phytosterols' levels and the increase of the content of oxyphytosterols were observed. The main dominant group in heated samples was hydroxy and epoxy sterols. Despite differences in fatty acid composition and content and composition of single phytosterols in unheated oils samples, the total content of oxyphytosterols after finishing of heating was on a similar level for each of the tested oils. This showed that the fatty acid composition of oil is not the only factor that affects the oxidation of phytosterols in foods during heating.

Effect of black cumin oil on the oxidative stability and sensory characteristics of mayonnaise

Mayonnaise is one of the most commonly used sauces all over the world but it is vulnerable to oxidation because of its high oil content. Using natural antioxidants instead of synthetic ones is a popular and promising topic in the food industry. The aim of this study was to increase the oxidative stability of mayonnaise using cold-pressed black cumin oil (BCO), which has high antioxidant activity due to its phenolic content. Four different mayonnaise formulations were used: Mayo-Control, Mayo-5% BCO, Mayo-10% BCO, and Mayo-20% BCO, which refer to a 0 (control), 5, 10, and 20% BCO replacement of total sunflower oil content, respectively. Thymoquinone content of the mayonnaises including BCO increased with the increasing BCO ratios. At the end of the storage for 4 weeks at 20 °C, peroxide values of Mayo-Control, Mayo-5% BCO, Mayo-10% BCO, and Mayo-20% BCO samples were recorded as 36.07 ± 1.51, 26.76 ± 0.67, 25.60 ± 0.57, and 17.66 ± 1.93 meq O₂/kg oil, respectively. The conjugated diene and triene values of the mayonnaises prepared by adding BCO were lower than those of the control group during storage. Overall acceptability of Mayo-5% BCO in sensory analysis was higher than that of Mayo-Control. Using BCO in mayonnaise improved its oxidative stability and flavor.

Effect of tocopherols, tocotrienols, β-carotene, and chlorophyll on the photo-oxidative stability of red palm oil

Effect of tocols, β-carotene, and chlorophyll on photo-oxidative stability of red palm oil (RPO) were studied. Model systems of triacylglycerols+tocols, triacylglycerols+β-carotene, triacylglycerols +tocols+β-carotene, and triacylglycerols+tocols+β-carotene+chlorophyll were exposed to fluorescent light at intensities of 5,000, 10,000, and 15,000 lux for 7 h at 30±2°C. Changes in concentrations of tocopherols, tocotrienols, β-carotene, chlorophyll, and peroxide values were evaluated every hour. Light intensity accelerated degradation of tocols in the triacylglycerols+tocols system and β-carotene in the triacylglycerols+β-carotene system. Gamma-tocotrienol showed the highest degradation rate and β-carotene was the most sensitive compound to changes in light intensity, indicated by the lowest light intensity coefficient (zi) value. The presence of tocols and β-carotene together showed protective effects for the photo-oxidative stability of RPO. The presence of chlorophyll increased the rate of photo-oxidation at high light intensities. Interactions between tocols and β-carotene contributed to the photo-oxidative stability of RPO.