Effects of Deuterium Oxide on the Oxidative Stability and Change of Headspace Volatiles of Corn Oil

Effects of deuterium oxide and deuterium oxide-free water on the oxidative stability and formation of headspace volatiles were determined for corn oils to evaluate the role of moisture as an active influential factors during lipid oxidation. Mixtures of corn oil and water with different ratios of deuterium oxide were prepared, and the mixtures were stored at 60 °C for 2 days. Headspace oxygen contents, conjugated dienoic acid (CDA) values, and p-anisidine values (p-AV) were analyzed as a measure of oxidative stability, and headspace volatiles were analyzed by solid phase microextraction and a gas chromatography mass selective detector to determine the involvement of deuterium in volatiles. Deuterium oxide accelerated the rate of lipid oxidation in corn oil compared to oils with deuterium-free water based on the results of headspace oxygen content, CDA, p-AV, and total volatile content. Fragmented mass to charge ratios (m/z) of 73.1/72.1 for d ₁-pentane/pentane and 57.0/56.0 for d ₁-2-propenal/2-propenal from samples containing deuterium oxide were significantly higher than those from deuterium oxide-free water, implying that moisture participated to form volatiles in corn oil oxidation under air-tight condition. Deuterium oxide appeared to accelerate the rate of lipid oxidation in corn oils and participated to form volatiles from oils during oxidation.     

Differences in Oxidative Stability,Sensory Properties,and Volatile Compounds of Pepper Aromatized Sunflower Oils Prepared by Different Methods during Accelerated Storage

The study aims to compare the differences in the oxidative stability, sensory properties, and volatile compounds during accelerated storage of pepper aromatized sunflower oil (PASO) samples prepared by maceration method (PASO-M), co-pressing method (PASO-C), and direct addition method (PASO-A), respectively. The results exhibit that their oxidative stability is in the relative order: PASO-A > PASO-C > PASO-M. Meanwhile, the PASO-A sample is the most preferable aromatized sunflower oil by consumers according to sensory analysis. In addition, a total of 83 volatile compounds are identified in the three PASO samples during the storage, and the principal component analysis (PCA) shows that their volatile compounds are quite different at the initial stage of the storage. Still, they are similar among each other from the middle of storage period. As consequence, the aromatized sunflower oil sample prepared by the direct-addition method during the storage possesses better oxidative stability and sensory attributes, and there is not much difference among their volatile compounds, indicating that the aromatized sunflower oil prepared by direct-addition method can be developed as promising aromatized sunflower oil. Practical applications: This study shows that aromatization increases oxidative stability and sensory properties of sunflower oil. By this way some sunflower oils with special sensory properties are obtained: special smell and taste, special color, etc. These peppers aromatized sunflower oils can be used to increase taste and smell in some dishes. For example, they can be used in some salads and some roast meats to give more taste and color.     

Enhancing Oxidative Stability of Sunflower Oil during Convective and Microwave Heating Using Grape Seed Extract

This study was performed to investigate the effectiveness of grape seed extract (GSE) compared to butylated hydroxytoluene (BHT) on retarding lipid oxidation of sunflower oil subjected to convection and microwave heating up to 240 min under simulated frying conditions. The progress of lipid oxidation was assessed in terms of peroxide value (PV), p-anisidine value (p-AV), conjugated dienes and trienes (CD, CT), inhibition of oil oxidation (IO) and TOTOX value. In addition, total phenolic content (TP) was evaluated in samples before and after heating in order to assess the changes in these compounds relative to the extent of lipid oxidation. The results of this study highlight that GSE showed a significantly inhibitory effect on lipid oxidation during both treatments, although to a different extent. This ability was dose-dependent; therefore, the extent of lipid oxidation was inversely related to GSE level. Convective heating, respective microwave exposure for 240 min of samples supplemented by GSE to a level of 1000 ppm, resulted in significant decreases of investigated indices relative to the control values as follows: PV (48%; 30%), p-AV (29%; 40%), CD (45%; 30%), CT (41%; 36%), TOTOX (35%; 37%). GSE to a level of 600-800 ppm inhibited the lipid oxidation in a similar manner to BHT. These results suggested that GSE can be used as a potential natural extract for improving oxidative stability of sunflower oil during thermal applications.     

添加剂对橡胶籽油生物柴油氧化稳定性的改进

测定了橡胶籽油的物化性能及组成. 加入6种抗氧化剂,采用Rancimat法研究了其添加量及复配、温度、0#柴油添加量、金属铜、铁等对橡胶籽油生物柴油氧化稳定性能的影响. 结果表明,橡胶籽油所制生物柴油不饱和脂肪酸含量达82.1%,诱导期为0.81 h,达不到国家标准(6 h). 6种抗氧化剂在添加量为4000′10-6(w)时对橡胶籽油生物柴油的氧化稳定性能均有提升,其中TBHQ效果最好,使其氧化稳定性诱导期达13.09 h,6种抗氧化剂的抗氧化效果为TBHQ>BHT>D-TBHQ>OG>PG>BHA. PG与其他抗氧化剂复配后效果较好,而TBHQ与其他抗氧化剂复配后效果降低. 温度和0#轻柴油添加量对橡胶籽油生物柴油的氧化稳定性能影响很大,随温度升高,诱导期明显缩短,而随0#柴油添加量增大,诱导期增加,添加量较大时诱导期增幅很大. 铁、铜对其氧化稳定性能也有一定影响.     

Comparison of the Rancimat and the ACL Instrument for Measuring the Oxidative Stability of Corn Oil

A comparison was undertaken between two machines that utilise accelerated methods to measure oxidative stability: the Rancimat (Metrohm, Switzerland) and the single channel chemiluminescence instrument (ACL Instruments, Switzerland). The results from the machines showed good correlation for the measurement of the oxidation induction time of corn oil. For the ACL Instrument, the effect of the sample holder material (aluminium or borosilicate glass) was also investigated and clear differences were noted. Finally, a stability study was carried out over a period of 6 months, with corn oil, stored in the dark at three temperatures: ~4, ~27, ~40 °C and it was observed that it was possible to track subtle changes in oxidative stability using chemiluminescence.     

Oxidative Stability and In Vitro Release Properties of Encapsulated Wheat Germ Oil in Saccharomyces cerevisiae Cell-Based Microcapsules

This research aims to evaluate the feasibility of Saccharomyces cerevisiae cell-based microencapsulation for wheat germ oil (WGO) based on oxidative stability and in vitro release properties. Microencapsulation of samples is achieved by freeze-drying WGO-in water emulsions containing alive, non-plasmolyzed, and plasmolyzed yeast cells. The encapsulation efficiency (EE), loading capacity (LC), release characteristics, and oxidative stability of WGO are determined before and after microencapsulation. The amount of β-carotene in the digesta is used to evaluate the release properties. Plasmolyzed yeast cells yield the highest EE (43.1%) and LC (216.5 g kg⁻¹). In cases where alive and non-plasmolyzed yeast cells were used as an encapsulant, a higher release rate was obtained in esophagus-stomach conditions, while higher digestion took place mainly in the duodenum and ileum with plasmolyzed cells. Encapsulation of WGO in plasmolyzed yeast cells provide the lowest peroxide and p-anisidine values and the highest oxidative protection during the accelerated oxidation test at 60 °C for 24 days. This result is also confirmed by Rancimat induction time. Practical Applications: Removing the plasma content by plasmolysis changes the structure of the yeast cell membrane and improves the encapsulation ability and release properties. Encapsulation of WGO with plasmolyzed yeast cells provides superiority in oxidative stability compared to native WGO. The potential value of WGO as an ingredient in the preparation of functional foods could be achieved by yeast cell encapsulation.     

Crude Wax Extracted from Rice Bran Oil Improves Oleogel Properties and Oxidative Stability

Crude wax extracted from rice bran oil (RBO) is used to improve the oleogel properties and oxidative stability of RBO. The effect of crude rice bran wax (CrBW) on the formation characteristics and oxidative stability of oleogels is discussed. The results show that oleogels can be formed with 7.0 wt% CrBW at 20 °C. As the concentration of CrBW increases from 7.0 to 11.0 wt%, the hardness and solid fat content (SFC) of the oleogels increase significantly, and the oleogels are primarily β' crystals. Moreover, oleogel crystals formed with 5 and 7 wt% CrBW are flocculent; when the amount included is 9%, the oleogel crystals are transformed into long dendrites, and the density rises. After 90 days of storage at 20 °C, the peroxide value of oleogels formed with 9.0 wt% CrBW slowly rises from 3.21 to 6.52 mmol kg⁻¹. Practical Applications: Oleogels prepared here by CrBW and RBO are an innovative structural lipid without trans fats. Useful information on the rich fats and nutrients in CrBW is provided, which reduces the production cost and improves the industrial production capacity.     

Hydroperoxide as a Prooxidant in the Oxidative Stability of Soybean Oil

Fifteen milliliters of soybean oil having peroxide value (PV) of 0, 2, 4, 6, 8, or 10 meq/kg oil in a 35 mL serum bottle was sealed air-tight with a Teflon rubber septum and aluminum cap and was stored in a forced-air oven at 50 °C. The oxidative stability of soybean oil was evaluated daily for six days by measuring the headspace oxygen content and volatile compounds in the headspace of a sample bottle by gas chromatography. As the initial PV of the oil increased from 0 to 2, 4, 6, 8 and 10, the headspace oxygen decreased and the volatile compounds increased at p < 0.05. Hydroperoxide accelerated the oxidation of soybean oil. The correlation coefficient (R ²) between the headspace oxygen and the volatile compounds was 0.95. The increase of tertiary butyl hydroquinone (TBHQ) from 0 to 50 ppm for the oil of PV 4 or 8 had a significant effect on the oxidative stability at p < 0.05. The increase from 50 to 100 ppm for the oil of PV 4 or 8 did not significantly increase the stability at p > 0.05. The oxidative stability of PV 8 meq/kg and 50 ppm TBHQ was better than the control with PV 0 and 0 ppm TBHQ at p < 0.05. TBHQ was an effective antioxidant to improve the oxidative stability of soybean oil.     

MCT Oil Coating Improves the Oxidative Stability of Surface Lipids in Corn Extrudates

Lipid‐containing extrudates are highly susceptible to lipid oxidation because of their porous structure and high specific surface area. The objective of this study is to investigate the effect of a low‐oxidizable medium‐chain triglycerides (MCT) coating on the oxidative stability. Therefore, cornmeal is extrusion cooked with commercial vegetable oil and various water contents (10–18% on dry matter) and partially coated with 5% w/w MCT oil. Lipid oxidation in the extrudates is examined during storage at +40 °C by measuring hydroperoxide concentrations in different lipid fractions (surface, inner‐surface, and matrix‐incorporated lipids). Hexanal is analyzed using headspace‐gas chromatography. Coating allocation is studied by fatty acid profiles of the lipid fractions, by fluorescence microscopy, and computerized microtomography. Application of an MCT coating leads to lower hydroperoxide concentrations and significantly reduces hexanal formation during storage. In particular, the surface lipids are stabilized. MCT oil diffuse only to small extent inside the extrudates and its effect on lipid oxidation can be attributed to differenct effects: filling surface microcracks, reducing the release of volatiles, and dilution of oxidizable lipids. This effect is strongest in porous extrudates with low feed‐water content. Practical applications: Inhibition of lipid oxidation of fatty extrudates is of great importance for producers as well as consumers. In this study, we examine whether it is possible to improve the oxidative stability of extrudates by application of a lipid‐based coating. The results of this study suggest that it will be possible in the future to produce extrudates that are protected from oxidation by a thin natural oil film. We expect that especially products such as kibbles could benefit from treatment with a low‐oxidizable lipid‐based coating. In these products, fats are already used in combination with other functional ingredients. The combination of an MCT coating with a palatant or antioxidant is, therefore, an obvious alternative and of high relevance for manufacturers.     

Bioactive Compounds,Antioxidant Activities and Heat Stability of Corn Oil Enriched with Tunisian Citrus aurantium L. Peel Extract

This study was designed to examine physicochemical composition, antioxidant activities and heat stability of corn oil enriched with bitter orange peel. Volatile compounds composition of corn oil flavored with Citrus aurantium peel was investigated. Flavored oil total aroma content (2.6 mg/mg oil) was mainly represented by monoterpene hydrocarbons and limonene was the major one (2.49 mg/mg oil). Flavored oil methanolic extract was characterized by total phenol content of 1.22 mg GAE/kg. Chlorogenic, ferulic and p-coumaric acids were the major phenolic components of the flavored oil extract (34.33, 30.24 and 19.39 %, respectively). It was also characterized by a higher chlorophylls and carotenoids contents than the refined one. Antioxidant activities of methanolic extracts of both samples were determined using four assays: DPPH, reducing power, β-carotene bleaching and metal chelating tests. In β-carotene bleaching and DPPH radical scavenging assays, flavored oil methanolic extract showed higher activities than the control. It was characterized by a total antioxidant activity of 4.08 mg GAE/kg and an EC₅₀ value of 3.14 mg/mg oil. Its concentration providing 50 % inhibition (IC₅₀) was 0.53 mg/mg oil in the DPPH test and 4.08 mg/mg oil in the β-carotene bleaching test. However, refined corn extract showed significantly lower antioxidant activities (p < 0.05). Results of the oxidative stability index showed bitter orange peel effectiveness against thermal oxidation based on the increased induction time observed in flavored oil (5.95).     

一种两亲聚合物稠油降黏剂的制备及性能评价

以卤代烷烃、聚乙烯亚胺（PEI）、丙烯酰胺（AM）、2-丙烯酰胺-2-甲基丙磺酸（AMPS）为原料，采用自由基聚合的方法制备了一种具有耐温抗盐性能的两亲聚合物型稠油降黏剂。利用红外光谱仪、显微镜、旋转滴界面张力仪、哈克流变仪、填砂管驱油实验研究了聚合物对稠油的乳化降黏及驱油能力。结果表明，当聚合降黏剂质量分数为1.00%时，油水质量比7:3条件下，春风油田稠油黏度由4753 mPa?s降至85 mPa?s，降黏率大于98%，油水界面张力由11.59 mN/m降低至0.06 mN/m。经过110℃老化24 h、矿化度1.45?105 mg/L条件下降黏率大于93%，具有较好的耐温耐盐性。在50℃、4.84?104 mg/L条件下，质量分数为0.50%的降黏剂溶液黏度为56 mPa?s，与市售部分水解聚丙烯酰胺HPAM溶液32 mPa?s的黏度相比，该聚合物降黏剂在矿化度条件下具有更好的水相增稠能力。填砂管驱油实验注降黏剂驱能够在水驱基础上提高采收率37.45%，表明该聚合物溶液可以通过降低稠油黏度和扩大波及体积提高稠油的采收率。     

Evaluation of Oxygen-Limitation on Lipid Oxidation and Moisture Content in Corn Oil at Elevated Temperature

The role of oxygen-limitation on lipid oxidation and moisture content were tested in corn oil heated to 60, 100, and 140 °C. The degree of oxidation was determined by analyzing headspace oxygen content, conjugated dienoic acids (CDA), and p-anisidine value (p-AV). The moisture content in bulk oil was analyzed by the Karl Fischer method. Oxygen-limited samples heated to 100 and 140 °C had significantly more lipid oxidation than oxygen-unlimited samples at early timepoints (p < 0.05). After this period, the oxygen-unlimited samples had more lipid oxidation based on CDA and p-AV assays. During those initial periods, oxygen-limited samples had significantly higher moisture content than oxygen-unlimited samples (p < 0.05), which implies that moisture content in oils plays an important role in the rate of lipid oxidation. The increased moisture content in bulk oil under oxygen-limited conditions is due to headspace moisture rather than moisture inside the oil. However, the effects of oxygen-limitation on lipid oxidation were less clear at 60 °C than at 100 or 140 °C.     

Oxidative Stability and Characterization of Quinoa Oil Extracted from Wholemeal and Germ Flours

Quinoa seeds are a source of lipids of great quality, and they highlight the content and composition of fatty acids and the presence of antioxidants such as tocopherols. Solvent extraction of quinoa oils was carried out from two matrices (wholemeal and germ flours), and in both cases, the extraction performance, physical–chemical characteristics, and oxidative stability were determined. Oxidative stability of the oil was assessed using an accelerated aging experiment under storage conditions at 60 °C for 12 days, in which the following parameters were measured: peroxide value, acid value, conjugated dienes and trienes, and scavenging radical capacity. Germ flour showed greater extraction yields (27.30 ± 0.15 g/100 g) compared to wholemeal (5.88 ± 0.02 g/100 g). Both oils presented similar physicochemical parameters, although the tocopherol content was higher in the oil extracted from germ flour (1354 vs. 735 mg/kg oil). At the same time, wholemeal oil showed a superior oxidative stability; hence, the wet milled process produces a minor impact on the compounds responsible for protection against lipid oxidation.     

活性亚甲基化合物的电解偶联

以Ｉ２／Ｉ－—两酮为间接氧化－还原体系，对三种具有活性亚甲基的化合物（ｌａ～３ａ）进行电解偶联反应，生成具有多官能团的１，４－二羰基化合物（１ｂ～３ｂ）。讨论了各种因素对反应的影响，并得到反应的最佳偶联条件。