Temperature dependence of the autoxidation and antioxidants of soybean, sunflower, and olive oil

Effects of temperature on the autoxidation and antioxidants changes of soybean, sunflower, and olive oils were studied. The oils were oxidized in the dark at 25, 40, 60, and 80 °C. The oil oxidation was determined by peroxide (POV) and p-anisidine values (PAV). Polyphenols and tocopherols in the oils were also monitored. The oxidation of oils increased with the oxidation time and temperature. Induction period decreased with the oxidation temperature; 87 and 3.6 days at 25 and 60 °C, respectively, for sunflower oil. The activation energies for the autoxidation of soybean, sunflower, and olive oils were 17.6, 19.0, and 12.5 kcal/mol, respectively. Olive oil contained polyphenols at 180.8 ppm, and tocopherols were present at 687, 290, and 104 ppm in soybean, sunflower, and olive oils, respectively. Antioxidants were degraded during the oil autoxidation and the degradation rates increased with the oxidation temperature of oils; for tocopherols, 2.1 × 10⁻³ and 8.9 × 10⁻²%/day at 25 and 60 °C, respectively, in soybean oil.     

Oxidative stability of potato chips: effect of frying oil type,temperature and antioxidants

The effect of type of frying oil and temperature on the oxidative stability of potato chips during storage was studied. Cottonseed oil, soybean oil, olive kernel oil and palmolein were used as frying media. The chips were packaged in metallized cellophane bags and incubated at 63 °C. At definite time intervals the absorbed oil was extracted and analyzed for peroxide value, Totox number and conjugated diene content. Olive kernel oil and palmolein absorbed into the chips showed better stability, whereas soybean oil presented the higher oxidation rate. Frying temperature (170, 180 or 190 °C) did not affect the oxidation rate during storage, with the exception of conjugated diene formation which was greater for chips fried at 190 °C. Ground oregano or oregano extract, obtained by petroleum ether extraction, were added to the chips as antioxidants. Both retarded significantly the oxidation rate of the oil absorbed into the chips, with results comparable to tertiary butylhydroquinone (TBHQ) during storage at 63 °C for 7 days; however TBHQ proved significantly more effective after that time. © 1999 Society of Chemical Industry     

Effect of temperature on oxidation kinetics of walnut and grape seed oil

The effects of temperature on the oxidation of walnut oil (WO) and grape seed oil (GSO) were investigated. Both oils were stored at 25, 40, 60, and 80°C for 60, 30, 12, and 6 day, respectively. Degree of oxidation was measured in terms of peroxide value (POV), conjugated dienoic acid (CDA) value, and p-anisidine value (p-AV). The rates of increase in POV, CDA, and p-AV in both oils were strongly dependent on storage temperature. The induction period (IP) decreased gradually with increasing storage temperature in both oils. WO showed shorter IPs (23.0, 9.2, and 1.0 day at 25, 40, and 60°C, respectively) than those of GSO (41.5, 12.0, and 1.8 day at 25, 40, and 60°C, respectively), indicating the higher susceptibility of WO to oxidation. The activation energy (Ea) for the IP of WO and GSO autoxidation was similar (75.87 and 75.66 kJ/mol, respectively), revealing similar temperature dependence for autoxidation in WO and GSO.

     

常温储存和干热处理对豆粕蛋白质氧化的影响

研究常温储存和干热处理对豆粕中蛋白质氧化的影响。取新鲜豆粕200 g装入自封袋,置于室温下保存不同时间(1、10、20、30和60 d);另取豆粕20 g于烘箱中100℃加热不同时间(0、1、2、4和8 h),测定分析2种处理方式对豆粕中的蛋白质羰基、巯基、总巯基基团及氨基酸含量的影响。结果表明,与新鲜豆粕(对照)相比,室温储存和干热处理不同时间后蛋白质羰基含量均显著增加(P0.05);随储存和干热处理时间的增加,豆粕蛋白质巯基和总巯基基团含量均逐渐降低,蛋白质巯基被氧化成非二硫键的含硫化合物,导致蛋白质巯基和总巯基与二硫键含量均降低;随加热时间的延长豆粕中苏氨酸、酪氨酸、赖氨酸及组氨酸含量在数值上逐渐降低。结果提示,蛋白质羰基、巯基及氨基酸含量的变化与蛋白质氧化密切相关,室温储存和干热处理均会导致豆粕中蛋白质发生氧化。     

Effects of storage conditions on oxidative stability of soybean oil

Soybean oil in the presence or absence of 200 µg g^?1 tert‐butyl hydroquinone (TBHQ) was subjected to accelerated oxidative storage at 60 °C for 10 days or stored at room temperature for 12 months. Tocopherol contents of the oil decreased, whereas the headspace volatiles and peroxide values (PV) increased as the storage time increased. During accelerated storage, TBHQ was effective in retarding the formation of hydroperoxides and headspace volatiles in the oil. TBHQ also protected tocopherols, especially α‐tocopherol, from oxidation. During long‐term room‐temperature (LTRT) storage, the changes in PV between the oils with and without TBHQ were similar, but the oil with TBHQ had lower headspace volatile contents than that without TBHQ. Headspace volatile analysis was more suitable than PV measurement for predicting the oxidative stability of soybean oil during LTRT storage. The contents of hexanal or (E)‐2‐heptenal in the oil at 1–5 days of accelerated storage could be used to predict those of the corresponding compound in the oil at 0–4 weeks of LTRT storage. Copyright © 2005 Society of Chemical Industry     

Oxidative stability,shelf-life and stir-frying application of Torreya grandis seed oil

Torreya grandis seed oil, with a feature of Δ5-sciadonic acid (SA, 20:3 Δ5, 11, 14 ω-6), is an attractive woody oil as its potential health benefits in lowering blood and hepatic lipids and anti-inflammatory properties. In the present study, its oxidative stabilities at both room temperature and heating conditions were investigated by analysing oxidation stability index (OSI), shelf-life, changes of fatty acids, acid value and peroxide value during stir-frying tests. Also, its effects on the sensory qualities of stir-fried shredded potatoes were evaluated. The OSI of T. grandis seed oil was 2.97 h at 120 °C, which was 11.24% higher than that of the control soybean oil, contributing to a longer predicted shelf-life of 135–195 d for T. grandis seed oil than 127–180 d for soybean oil. T. grandis seed oil also exhibited superior thermal stability compared to soybean oil. The feature fatty acid, SA, only lost 2.48–5.73% (decreasing from 14.14 to 13.33–13.79%) under the optimised stir-frying conditions at 140–180 °C for 3–5 min. For the stir-frying shredded potatoes, T. grandis seed oil made it more pleasing in colour, odour and palatability. Due to its desirable oxidative stability at room temperature and stir-frying performance at high temperature, T. grandis seed oil is suitable for use as a domestic cooking oil.     

Factors Influencing the Production and Activity of a Streptococcus thermophilus Lipase

The cells from 32 strains were disrupted by pressure. All the strains except two showed lipase activity. Optimum temperature for lipase production was 44°C. Production of lipase was inhibited by addition of butter oil (29%), milk (41%) and casein (12%) and stimulated by soybean oil (39%), cream (27%) and corn oil (21%) to the medium. The enzyme was stable when stored at 37°C and 45°C for 1 wk. The enzyme was partially inactivated by pasteurization treatment (65°C/30 min). Optimum temperature and pH for lipase activity was 45°C and 9.0, respectively. The enzyme was relatively more active toward tributryin than toward natural lipids.     

Oil Bodies Extracted from High‐Fat and Low‐Fat Soybeans: Stability and Composition During Storage

Soybeans contain oil bodies (OBs) that encapsulate triacylglycerols (TAGs) with a phospholipid monolayer carrying scattered proteins. In nature, soybean OBs can form natural emulsions in aqueous media and may serve as natural, minimally processed, stable, and pre‐emulsified oil for addition into appropriate food systems. In this study, OBs were obtained by aqueous extraction from the mature seeds of 2 soybean crop cultivars, high‐fat soybean and low‐fat soybeans. The compositions of the extracted OBs were analyzed during storage at room temperature up to 14 d (pH = 7). The oxidative stability of these OBs, stored at 60 °C, was evaluated by measuring the presence of primary (lipid hydroperoxides) and secondary lipid oxidation products (malondialdehyde) by determining the standard peroxide value (PV) and thiobarbituric acid‐reactive substances (TBARS) value. During storage, the contents of unsaturated fatty acids, phospholipids, and tocopherols declined in both OBs, while their mean particle diameters (d₃₂) and ζ‐potentials increased. The changes in PV and TBARS values exhibited a similar trend for both OBs, but the OBs from low‐fat soybeans had significantly lower PV and higher TBARS values than the OBs from high‐fat soybean cultivars (P < 0.05). Overall, the OBs from both soybean cultivars had good stability during storage.     

不同储存条件下核桃油的氧化稳定性研究

为了研究合适的核桃油储存方式,以温度、光照、氧气、水分四个因素为自变量,酸价、过氧化值为指标研究氧化规律。Rancimat法和60℃烘箱加速氧化法预测货架期,以常温储存核桃油为对照组,比较两种方法的可靠性。结果表明:效果最好为冷藏组,储存超过60 d,最短为敞口组和摇晃组,不足14 d,添加0. 1%～0.3%水分组,21 d开始酸败,避光组储存期为49 d。Rancimat法预测货架期为212 d,烘箱加速法预测为48～80 d。常温储存49 d酸败,烘箱加速法预测货架期更可靠。建议核桃油低温储存,同时可避光存放,尽量选用与空气接触面积小的储油容器,并减少油的重复使用。     

加速氧化条件对大豆油氧化稳定性的影响

本研究采用同批油料提取的水酶法大豆油、溶剂浸提大豆油与一级大豆油进行室内储藏实验。不同温度（25⁸0℃）下储存一定天数（0⁶0d）测定样品过氧化值、共轭二烯值、共轭三稀值、p-茴香胺值以及脂肪酸组成。实验结果表明:在相同温度条件下,3种植物油的过氧化值有显著区别,一级大豆油的过氧化值显著高于水酶法大豆油和溶剂浸提大豆油;对于同一油脂在不同温度下,温度越高,氧化反应的活化能越小,大豆油氧化越快;油脂储藏稳定性为溶剂浸提大豆油>水酶法大豆油>一级大豆油。      

The effects of stabilised extracts of sage and oregano on the oxidation of salad dressings

The antioxidative activity of sage and oregano either dissolved in ethanol or homogenised with olive oil as a carrier was evaluated in salad dressings. These samples were stored in the dark at ambient temperature and at 40 °C, and with light exposure at ambient temperature. Sage and oregano extracts were encapsulated in liposomes by ultrasonification or microfluidisation, and their structures confirmed by microscopic examination and dye-marker carboxyfluorescein. The antioxidant effect of these preparations was evaluated in salad dressings during storage in the dark at ambient temperature, at 40 °C and at 60 °C. The oxidation process was followed by measuring the formation of conjugated diene hydroperoxides as primary and hexanal as secondary oxidation products, as well as changes in the compositions of fatty acids and tocopherols. Oregano and sage extracts homogenised with olive oil as a carrier showed higher antioxidative effects than these extracts dissolved in ethanol during storage in the dark at ambient temperature and at 40 °C. Exposure of salad dressings to light changed the antioxidative effect of plant extracts into a pro-oxidative effect. The preparation of liposomes by microfluidisation showed higher encapsulation efficiency and more homogeneous vesicles than liposomes prepared by ultrasonification. Sage liposomes prepared by micofluidisation showed high antioxidative effects similar to butylated hydroxytoluene liposomes in salad dressings during storage in the dark at ambient temperature and at 40 °C.     

Use of a spouted bed to improve the storage stability of wheat germ followed in paper and polyethlyene packages

Stabilization of wheat germ by heating in a spouted bed for 180–540 s with air at 140–200 °C was studied. The lipase activity decreased by 6–65%. Wheat germ processed at 200 °C for 360 s was ranked highest in sensory evaluation, described as having ‘a golden color’ and ‘nutty flavor’, and its lipoxygenase activity had decreased by 91.2%. This product and raw wheat germ were stored in paper, polyethylene and vacuum‐packed polyethylene pouches at 5 °C, room temperature (18–26 °C) and 40 °C, and the moisture contents, water activities, free fatty acid contents and peroxide values were followed for 20 weeks. The increases were faster in paper pouches than in the polyethylene ones; vacuum packaging in polyethylene did not bring about significant improvement. The peroxide values of raw samples exceeded 10 meq O₂ kg^?1 oil after 3–23 days while those of the processed samples stored at room temperature or 5 °C were still less than 10 after 20 weeks. The free fatty acid content and peroxide value changes were expressed by zero order kinetics, resulting in similar activation energies for the raw and processed samples. Copyright © 2005 Society of Chemical Industry     

A new pyrogallol coated oxygen scavenging film and their effect on oxidative stability of soybean oil under different storage conditions

The current study investigates the oxidative stability of soybean oil packaged with an oxygen scavenging film prepared by pyrogallol coating with concentrations of 5, 10, and 20% at 5, 23, and 60 °C and 95 ± 2% RH respectively. The oil stability was evaluated in terms of peroxide, thiobarbituric acid, and p-anisidine then compared with oil packed without the oxygen scavenging film. The results showed that the LDPE/PG 10 and 20% were efficient in the stabilization of soybean oil, even at high temperature. Peroxide, Thiobarbituric acid, and p-anisidine values, the oil samples packed with LDPE/PG films delayed the oil oxidation. The synergetic effect of LDPE/PG films, which can scavenge oxygen from the packaged product thereby slowing the oxidation of fats, was established in the study. The present study confirmed that active packaging could be introduced as a worthy replacement for direct addition of artificial antioxidants to the soybean oil.     

Effect of lipid oxidation and frozen storage on muscle proteins of Atlantic mackerel (Scomber scombrus)

The effect of storage on the lipids and proteins in Atlantic mackerel stored for up to 24 months at ?20 and ?30 °C was studied. Traditional methods including the peroxide value, thiobarbituric acid‐reactive substances (TBARS) and a reverse phase HPLC method were used to determine the primary and secondary lipid oxidation products. All tests showed an increase in lipid oxidation products with storage time and at a higher storage temperature of ?20 °C compared with samples stored at ?30 °C. Antioxidants had a significant effect (P < 0.01) on the inhibition of lipid oxidation, as shown by the reduction in peroxide value and hydroxides, and malondialdehyde formation. Similarly, deterioration of protein structure and functionality in mackerel stored for 3, 6, 12 and 24 months was greater at ?20 than ?30 °C. ATPase activity in the myosin extract of Atlantic mackerel showed a significant decrease (P < 0.01) with progressive frozen storage. Protein solubility in high salt concentration (0.6 M NaCl) decreased (P < 0.01) during storage at both ?20 and ?30 °C but was greater at ?20 °C. Interestingly, antioxidants BHT, vitamin C and vitamin E protected the proteins against complete loss of ATPase activity and protein solubility to a significant level (P < 0.01) for up to 1 year at ?20 °C compared with samples stored without antioxidants. This study confirms the deleterious effect of lipid oxidation products on protein structure and function in frozen fatty fish. © 2002 Society of Chemical Industry     

Fluorescence due to interactions of oxidizing soybean oil and soy proteins

Soy proteins with soybean oil (9:1,w/w) were stored at 60°C to investigate the changes in intrinsic fluorescence during oxidation. The front-surface fluorescence of the oxidized samples showed excitation and emission maxima at 355 and 440 nm respectively. The fluorescent compounds were soluble in the organic layer of the chloroform–methanol (2:1,v/v). The solution fluorescence showed an excitation maximum at 365 nm and an emission maximum at 450 nm, and the intensity increased during storage. The interactions of oxidizing soybean oil and soy proteins also resulted in decreases of protein solubility, soluble protein hydrophobicity, and free amino groups of proteins. With an antioxidant (BHT) addition, the changes in fluorescence and in protein properties were inhibited. The intensity of the solution fluorescence showed high correlation with TBA value (r=0.968) and protein solubility (r=−0.979), which could serve as an indicator for oxidative deterioration of soy proteins and soybean oil systems.     

Physical Properties and Oxidation Rates of Unrefined Menhaden Oil (Brevoortia patronus)

ABSTRACT: Unrefined menhaden oil was evaluated for thermal and rheological properties and its temperature-dependent viscosity and lipid oxidation rate were determined. Peroxide value, free fatty acids, density, specific gravity, water activity, moisture content, and enthalpy of the unrefined menhaden oil were 5.70 meq/kg, 3.80%, 0.93 g/mL, 0.93%, 0.52%, 0.15%, and 20.2 kJ/kg, respectively. The melting point range of unrefined menhaden oil was found to be −69.5 to 27.21 °C. The menhaden oil exhibited non-Newtonian fluid behavior at lower temperatures (5 to 25 °C), while it behaved like a Newtonian fluid at 30 °C. The oil apparent viscosity at 5 °C (0.22 Pa.s) was significantly higher (P < 0.05) than that at 30 °C (0.033 Pa.s). The average magnitude of activation energy for viscosity of the unrefined menhaden oil was 50.37 kJ/mol. The predicted apparent viscosity agreed (R²= 0.9837) satisfactorily with the experimental apparent viscosity. The minimal lipid oxidation rate of the oil was found at 25 and 35 °C for 6 h, higher lipid oxidation rates were observed when the oil was heated for 6 h at 45 to 85 °C. The rate of lipid oxidation for unrefined menhaden oil was temperature dependent (R²= 0.9425). This study showed that the magnitude of the apparent viscosity and oxidation rate of the unrefined menhaden oil was greatly influenced by temperature.     

DHA藻油脂质体制备及性质的研究

以大豆卵磷脂、胆固醇、吐温-80、DHA藻油为原料,探讨了薄膜超声法制备DHA藻油脂质体的工艺条件;分析了原料配比、温度、pH、超声时间、超声功率等因素对藻油脂质体包封率、粒径、电位的影响,对其氧化稳定性进行了初探,并研究其体外模拟消化行为。结果表明,藻油脂质体的最佳制备条件为:大豆卵磷脂与胆固醇比为3∶1(g/g)、大豆卵磷脂与藻油比为5∶1(g/g)、水化温度为40℃、pH为7.4、超声时间为120 s、超声功率350 W,在此条件下,所制备的脂质体呈椭圆球形,包封率为(91.55±0.4)%,粒径为(224.5±0.21)nm,PDI为0.224±0.003,电位(-32.4±0.03) mV;体外模拟小肠消化性能良好;室温放置一周后脂质体氧化稳定性良好。     

奇亚籽油储藏稳定性研究及货架期预测

为研究奇亚籽油储藏稳定性,以液压法制备的奇亚籽油为原料,探讨储藏温度、氧气和光照条件对奇亚籽油过氧化值、酸价、K₂₃₂、K₂₆₈和TBA的影响,并应用一级动力学模型结合Arrhenius方程建立过氧化值、酸价两个氧化指标随储藏温度、储藏时间变化的货架期预测模型,预测奇亚籽油货架期。结果表明：奇亚籽油的氧化稳定性受光照、氧气和温度的影响,在避光、密封、低温的储藏条件下能有效降低过氧化值、酸价等的增长速率,延长储藏时间;通过模型推算得出密封、避光条件下奇亚籽油在25℃条件下的货架期为94 d。     

Effects of monoacylglycerols on the oxidative stability of olive oil

BACKGROUND: The study of pro‐ and anti‐oxidant compounds is important for their influence on the shelf‐life and nutritional value of food. The aim of this research was to evaluate the activity of monoacylglycerols (MAG), obtained by partial saponification of a purified olive oil, added in increasing amounts to the same oil and submitted to the Rancimat test and oven test at 60 °C. Besides routine analyses, high‐performance size exclusion chromatography analysis of polar compounds was performed. RESULTS: The addition of MAG led in all cases to a significant slowdown of the oxidative processes. These trends were more evident as the oxidation went on. The purified oil added with 30 g kg^?1 of MAG after 9 days of oven test at 60 °C presented a level of oxidative degradation significantly lower than the control after only 4 days. CONCLUSION: The data showed a marked antioxidant effect of MAG in purified olive oil, contrary to what has been observed by other authors, who noticed either a pro‐oxidant or a non‐antioxidant activity of these compounds in soybean oil. A different behaviour of MAG during oxidation could depend on the different fatty acid composition of the oil matter they are added to. Copyright © 2010 Society of Chemical Industry     

Anti‐radical power gives insight into early lipid oxidation events during frying

The aim of this research was to use anti‐radical power (ARP) to study early lipid oxidation events during frying. The 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH?) test was used to determine the ARP. As oil does not dissolve completely in methanol, which is generally used for the DPPH? test, butanol was used instead. Changing the solvent did not influence the value of the ARP. The decrease of the ARP highly correlated with the increase of the peroxide value for soybean oil heated at 110 °C (R² = 0.99). Sensory analysis showed that rancidity of soybean oil and frying oil, heated at 180 °C, was perceived before the ARP decreased. Once the oil was perceived as rancid, the intensity of rancidity did not change significantly upon further heating. The ARP of soybean oil was found to decrease faster at 110 °C than at 180 °C, suggesting different mechanisms of radical formation. The total polar compounds of frying oil in which French fries were fried did not differ significantly from frying oil that was heated alone. However, frying of French fries caused more hydrolysis of the oil, while the ARP decreased faster when the oil was heated alone. Copyright © 2006 Society of Chemical Industry