Oil Oxidation Products Research Articles

Oxidation of Cod Liver Oil during Gastrointestinal in Vitro Digestion

Oxidation of cod liver oil rich in long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) was investigated during a gastrointestinal (GI) in vitro digestion. The digestion stimulated TBA-reactive substances (TBARS) formation in both the gastric and intestinal steps, whereas levels of lipid hydroperoxides remained nearly constant. The presence of digestive compounds was decisive for the TBARS development because TBARS did not change when the cod liver oil was subjected only to the temperature and pH gradient of the GI model. Preformed oxidation products in the cod liver oil resulted in further elevated TBARS levels during the digestion. Addition of hemoglobin (11.5 μM) to emulsified cod liver oil dramatically increased TBARS and lipid hydroperoxide levels during GI digestion, whereas 1 mg α-tocopherol/g oil did not show any protection against oxidation. Specific concern thus needs to be taken in the design of foods containing LC n-3 PUFA to preserve these lipids and avoid harmful oxidation, both before and after consumption.

Transglutaminase Catalyzed Cross-Linking of Sodium Caseinate Improves Oxidative Stability of Flaxseed Oil Emulsion

Sodium caseinate was modified by transglutaminase catalyzed cross-linking reaction prior to the emulsification process in order to study the effect of cross-linking on the oxidative stability of protein stabilized emulsions. The extent of the cross-linking catalyzed by different dosages of transglutaminase was investigated by following the ammonia production during the reaction and using SDS-PAGE gel. O/W emulsions prepared with the cross-linked and non-cross-linked sodium caseinates were stored for 30 days under the same conditions. Peroxide value measurement, oxygen consumption measurement, and headspace gas chromatography analysis were used to study the oxidative stability of the emulsions. The emulsion made of the cross-linked sodium caseinate showed an improved oxidative stability with reduced formation of fatty acid hydroperoxides and volatiles and a longer period of low rate oxygen consumption. The improving effect of transglutaminase catalyzed cross-linking could be most likely attributed to the enhanced physical stability of the interfacial protein layer against competitive adsorption by oil oxidation products.

Fish oil sensory properties can be predicted using key oxidative volatiles

AbstractThe high level of PUFA in fish oil, primarily eicosapentaenoic acid (EPA) and DHA result in rapid oxidation of the oil. Current methods used to assess oxidation have little correlation with sensory properties of fish oils. Here we describe an alternative method using solid phase microextraction (SPME) combined with GC‐MS to monitor volatile oxidation products. Stepwise discriminant function analysis (DFA) was used to classify oils characterized as acceptable or unacceptable based on sensory analysis; a cross‐validated success rate of 100% was achieved with the function. The classification function was also successfully validated with tasted samples that were not used to create the method. A total of 14 variables, primarily aldehydes and ketones, were identified as significant discriminators in the classification function. This method will be useful as a quality control method for fish oil manufacturers.Practical applications: This paper describes an analytical method that can be used by fish oil manufacturers for quality control purposes. Solid phase microextraction and GC‐MS were used to monitor volatile oxidation products in fish oil. These data, combined with results of analyses by a sensory panel, were used to create a function that classified fish oil samples as acceptable or unacceptable. The volatile oxidation products used to in the function were primarily aldehydes and ketones. This method can be used by fish oil manufacturers as an alternative to expensive sensory panels.

213 メンブランパッチの色によるタービン油の酸化劣化診断法の開発(セッション7 設備診断技術)

Lubricating oil is used in various machines and devices. However, lubricating oil is degraded with operating time or usage environment. Degradation causes of the lubricating oil are roughly classified into two types, one is caused by solid particle and other is caused by oil oxidation products. Diagnosis methods for solid particles in lubricating oils have many standards and researches. However, there are few diagnosis methods for oil oxidation products. Furthermore, oxidation degradation of the turbine basis oil becomes a serious problem in power generation plants recently. Therefore, on-site degradation diagnosis method which can detect the early stage of oxidation degradation of lubricating oil is desired for the proactive maintenance. In this study, we have developed degradation diagnosis method of lubrication oil which paid to the attention to coloration of the membrane patch with contamination. We prepared sample oils which were degraded by oxidation in the laboratory. We measured color parameters of membrane patches produced from sample oils using the colorimetric patch analyzer. As a result, we found that this method could detect the early stage of oxidation degradation of lubricating oil by measuring color parameters of membrane patch using the colorimetric patch analyzer.

Conductometric Sensors for Monitoring Degradation of Automotive Engine Oil

Conductometric sensors have been fabricated by applying imprinted polymers as receptors for monitoring engine oil quality. Titania and silica layers are synthesized via the sol-gel technique and used as recognition materials for acidic components present in used lubricating oil. Thin-film gold electrodes forming an interdigitated structure are used as transducers to measure the conductance of polymer coatings. Optimization of layer composition is carried out by varying the precursors, e.g., dimethylaminopropyltrimethoxysilane (DMAPTMS), and aminopropyl-triethoxysilane (APTES). Characterization of these sensitive materials is performed by testing against oil oxidation products, e.g., carbonic acids. The results depict that imprinted aminopropyltriethoxysilane (APTES) polymer is a promising candidate for detecting the age of used lubricating oil. In the next strategy, polyurethane-nanotubes composite as sensitive material is synthesized, producing appreciable differentiation pattern between fresh and used oils at elevated temperature with enhanced sensitivity.

Effects of Roasting Conditions on the Physicochemical Properties and Volatile Distribution in Perilla Oils (Perilla frutescens var. japonica)

Perilla seeds have more than 60% of α-linolenic acid, one of omega-3 essential fatty acids. Headspace volatiles and physicochemical properties including color, fluorescence intensity, and the oxidation products in perilla oil (PO) from perilla seeds roasted at different conditions were analyzed. Roasting temperature was 150, 170, 190, and 210°C, and roasting time was 15 and 30 min at each roasting temperature. PO from higher roasting temperature and longer roasting time had lower L* values, higher a*, b*, and chroma values, more brown pigments and fluorescence intensity, and more conjugated dienoic acids. Pyrazines were major volatiles in PO, and furans, sulfur-containing compounds, and hydrocarbons were also detected by a solid phase microextraction gas chromatography/mass spectrometry. In PO, 2,5-Dimethylpyrazine and 2-furancarboxaldehyde were 2 major volatiles. The principal component analysis of volatiles showed the 1st principal component (PC1) and the 2nd principal component (PC2) express 56.64% and 22.72% of the volatile variability in PO, respectively, which can differentiate PO prepared from roasting conditions clearly. Some physicochemical properties especially brown pigment and volatiles were positively correlated with each other in PO. Perilla oil (PO) from perilla seeds possesses more than 60% of α-linolenic acid, one of omega-3 fatty acids. Roasting process has been used to extract oil from perilla seeds. Understanding physicochemical properties of PO from diverse roasting conditions are important steps to produce PO in food industry. Roasting process induces darkening of color, increase of fluorescence intensity, and brown pigments in PO. Pyrazines and furans are major headspace volatiles in PO roasted above 170°C. The results of this study can help to produce PO in industrial scales with desired headspace volatiles, colors, and oxidative state.

Optimization of Oil Oxidation by Response Surface Methodology and the Application of this Model to Evaluate Antioxidants

AbstractThe oxidative stability of oils is a complex process influenced by several factors, making the evaluation of antioxidant effects of new compounds difficult. Thus, the objective of this study was to apply a factorial design to obtain the combination of factors that maximizes the formation of oil oxidation products, and use this model to evaluate the antioxidant activity of different compounds. Temperature, Fe2+ and ascorbyl palmitate were evaluated in two full‐factorial designs (23 and 32). The validated optimized oxidation model was obtained by adding 1.47 mmol/L of Fe2+ and 1.54 mmol/L of ascorbyl palmitate to flaxseed oil stripped of tocopherol kept at 40 °C for 8 days. Antioxidant activities of six compounds were evaluated using this model. All antioxidant samples were statistically different (p < 0.001) at 200 ppm concentration, indicating the efficiency of the optimized model to evaluate the antioxidant action of natural and synthetic compounds.

Determination of thermal oxidation and oxidation products of β-carotene in corn oil triacylglycerols

A reversed phase HPLC-DAD coupled to APCI-MS method is reported for the determination of the degradation of β-carotene and characterization of the oxidation products in corn oil. Corn oil containing β-carotene was oxidized in the Rancimat at 110°C from 1 to 14h. A significant degradation of β-carotene was observed in corn oil during accelerated thermal oxidation. A total of eight different oxidized products of β-carotene were identified, which includes 8′-apo-β-carotenal, 6′-apo-β-carotenal, 5,6-epoxy-8′-apo-β-carotenal, β-carotene-2,2′-dione, 13-Z-5,6,5′,6′-diepoxy-β-carotene, all-E-5,8-epoxy-β-carotene, all-E-5,6-epoxy-β-carotene, and 15-Z-5,6-epoxy-β-carotene. Corn oil triacylglycerols (TAGs) oxidation products were also identified using isocratic HPLC–ESI-MS. It was found that β-carotene promoted oxidation of TAGs especially at longer exposure times. For the first time two new classes of oxidized TAGs have been identified in corn oil, which were epidioxy bis-hydroperoxides and hydroxy bis-hydroperoxides. Other oxidation products of TAGs were mono-epoxides, mono-hydroperoxides, and epoxy hydroperoxides. It was found that complementing the HPLC-DAD method for β-carotene with ESI-MS method for TAGs oxidation provides a comprehensive set of analytical tools to characterize carotenoids and triacylglycerols oxidation and degradation in edible oils.

210 潤滑油の劣化診断技術の開発(セッション8 プラント・設備診断)

Lubricating oil is used in various machines and devices. However, lubricating oil is degraded with operating time or usage environment. Degradation causes of the lubrication oil are roughly classified into two types, one is caused by solid particle and other is caused by oil oxidation products. Diagnosis methods for solid particles in lubricating oils have many standards and researches. However, there are few diagnosis methods for oil oxidation products. In this study, we investigated to establish the relationship between the color of contaminants trapped on a filter after filtering degraded oil and properties of the lubricating oil, and developed diagnosis method of the lubricating oils using the colorimetric analysis which paid to the attention to the color of contaminants. These results suggested the feasibility of new diagnosis method of the lubricating oils by the colorimetric analysis.

Determination of lipid oxidation products in vegetable oils and marine omega-3 supplements

Background: There is convincing evidence that replacing dietary saturated fats with polyunsaturated fats (PUFA) decreases risk of cardiovascular diseases. Therefore, PUFA rich foods such as vegetable oils, fatty fish, and marine omega-3 supplements are recommended. However, PUFA are easily oxidizable and there is concern about possible negative health effects from intake of oxidized lipids. Little is known about the degree of lipid oxidation in such products.Objective: To assess the content of lipid oxidation products in a large selection of vegetable oils and marine omega-3 supplements available in Norway. Both fresh and heated vegetable oils were studied.Design: A large selection of commercially available vegetable oils and marine omega-3 supplements was purchased from grocery stores, pharmacies, and health food stores in Norway. The content of lipid oxidation products were measured as peroxide value and alkenal concentration. Twelve different vegetable oils were heated for a temperature (225°C) and time (25 minutes) resembling conditions typically used during cooking.Results: The peroxide values were in the range 1.04–10.38 meq/kg for omega-3 supplements and in the range 0.60–5.33 meq/kg for fresh vegetable oils. The concentration range of alkenals was 158.23–932.19 nmol/mL for omega-3 supplements and 33.24–119.04 nmol/mL for vegetable oils. After heating, a 2.9–11.2 fold increase in alkenal concentration was observed for vegetable oils.Conclusions: The contents of hydroperoxides and alkenals in omega-3 supplements are higher than in vegetable oils. After heating vegetable oils, a large increase in alkenal concentration was observed.

HPLC–ESI-MS investigation of tyrosol and hydroxytyrosol oxidation products in virgin olive oil

The aim of this research is the characterisation of the oxidation products of several hydrophilic phenols of virgin olive oil (VOO), such as hydroxytyrosol (3,4-DHPEA) and tyrosol ( p-HPEA) and, their identification in the product during storage. This work is aimed at finding analytical indicators that can be used both as molecular markers of VOO “freshness” and for the evaluation of the shelf life of the product itself. Two oxidation systems were examined for the oxidation of p-HPEA and 3,4-DHPEA: enzymatic oxidation and Fenton oxidation. Reaction products were different for the two systems and were identified as quinones, dimers, and acids. During the autoxidation process, Fenton reaction oxidation products, but not enzymatic oxidation products, were found in VOO.

Antioxidative Activity of 5-n-Pentadecyl-2-tert-butylphenol Stabilizers in Mineral Lubricant Oil

This work shows the synthesis, characterization, and thermo-oxidative study of 5-n-pentadecyl-2-tert-butylphenol [alkylphenol (AP)] before and after its incorporation into mineral lubricant oil. AP was synthesized by alkylation of hydrogenated cardanol. For this study, we employed thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), and differential thermal analysis (DTA) techniques. Mineral lubricant oil was submitted to an accelerated oxidation test in the presence and absence of AP according to the modified ASTM D-2440 method. The addition of 1% AP to the oil has reduced the carbonyl and peroxide band areas: 1.00−1.00 (without AP) and 0.35−0.32, ROOH; 0.53−0.59, C═O (with AP), respectively. The results showed that AP significantly reduced the formation of oxidation products in the lubricant oil analyzed. TG−DTG curves showed that 5-n-pentadecyl-2-tert-butylphenol is more stable than 2,6-di-t-butyl-4-methylphenol (BHT), 158 against 87 °C for BHT. According t...

Storage stability of traditional Tunisian butter oil produced from spontaneous fermentation of cow’s milk

Physicochemical characteristics of traditional Tunisian butter (TTB) and thermal stability of the butter oil were studied. Thermal stability of samples was estimated by using the accelerated shelf life testing method. Effect of heating on some quality characteristics of traditional Tunisian butter oil (TTBO) was investigated and compared at different temperatures (60°C, 100°C and 130°C). Induction period of sample heated at 60°C was important compared to that at 100°C and 130°C. This result may indicate the sensitivity of TTBO to elevated temperature. Absorption at 232 and 270 nm, acidity and PV increased rapidly after reaching the oxidation induction time. The temperature had a significant effect on the formation of oxidation products in traditional butter oil (TTBO). Fatty acid composition of TTBO was also changed after heating. This may explain the observed modification on some quality characteristics of TTBO such as viscosity, hardness, cohesiveness and colour. As a consequence, heat treatment produced alterations in the oxidative status of the butter oil that could affect the shelf life.

109 メンブランパッチの色による油の状態監視法(セッション2 状態監視(1))

Degradation of oils is roughly classified into two types, one is caused by solid particles and the other is caused by oil oxidation products. Diagnosis methods for solid particles in oils have many standards and researches. However, there are few diagnosis methods for the oil oxidation products. In the present study, two themes were examined. At first, the filtration mechanism by a membrane filter was discussed using oxidized oils which were prepared in laboratory. Secondly, the transmittance of lights through the membrane patch was discussed using oxidized oils. As a result, we found that the color properties of reverse side of the membrane patch was different by the amount of the oil oxidation products, and we also found that the transmittance of lights through the membrane patch can distinguished the difference of a light color by deterioration level of the oil. They seem that these two new methods can evaluate the deterioration level of used oils. Furthermore, we developed new equipment for diagnosis of membrane patch color based on these results.

108 レーザ光を用いたオイルスラッジ生成判定方法の開発(セッション2 状態監視(1))

Lubricating oil and hydraulic fluid deteriorate for the oxidation and contaminations from outside. The oil oxidation products repeat polycondensation and form oil-sludge including contaminations. But, the general oil analysis cannot analyze the situation of oil-sludge generation definitely. In this study, it was clarified that the judging oil-sludge generation was possible by using the separation oil-sludge from base oil by centrifugation and the comparison of laser transmittance before and after centrifugation.

Use of some agricultural waste hull ashes for the regeneration of fried sunflower oil

SummaryThe present study was aimed at improving the quality of fried sunflower oil. Synthetic (Magnesol XL), natural (diatomaceous earth) and hull ashes of rice, wheat and barley (agriculture plant wastes) were used to adsorb the oxidation products of fried sunflower oil. The mineral pattern (Si, Mg, Ca, Fe, Al, Mn and Cu) of the aforementioned substances were determined. The physico‐chemical properties [refractive index, viscosity, colour, smoke point, acid value, peroxide value, thiobarbituric acid (TBA) value, conjugated dienes and trienes, polar content, polymer content and oxidised fatty acids] of non‐fried, fried and fried‐treated sunflower oil were determined. The frying process was carried out at 180 °C ± 5 °C for 20 h, 4 h heating cycle per day for five consecutive days. The fried sunflower oil was treated with synthetic, natural and agricultural hull ashes at 105 °C for 15 min. The results indicate that Magnesol XL, diatomaceous earth, rice hull ash, wheat hull ash and barley hull ash contained Si + Mg + Mn, Si + Mn + Ca, Si + Mn, Si +Mn and Mn + Si as the basic metals, respectively. Frying of sunflower oil led to significant increase in refractive index, viscosity, colour, smoke point, acid value, peroxide value, TBA value, conjugated dienes and trienes, polar content, polymer content, and oxidised fatty acids and decrease in iodine value. Treatments of fried sunflower oil with the aforementioned substances greatly improved the quality of fried oil. Under the present experimental conditions all adsorbing substances performed similarly in removing the fried sunflower oil oxidation products.

Quality of Crude Oil Extracted from Aging Walleye Pollock (Theragra chalcogramma) Byproducts

AbstractThe quality of crude oil was examined as a function of the temperature and delay time between collecting and processing the fish byproducts from a commercial cannery into crude oil. Extracts from pollock byproducts stored at 6 and 15 °C for up to 4 and 10 days was examined. Longer storage of byproducts resulted in higher free fatty acid (FFA) and an increase in retinol levels in the extracted crude oils. Primary and secondary oxidation assays consisting of peroxide value and thiobarbituric acid‐reactive substances increased initially with storage time on day 1 followed by an unexpected decrease with storage time. Higher storage temperature resulted in greater FFA and retinol levels, but lower oxidation products in the crude oils. The tocopherol levels decreased with storage time of the byproducts with no differences between the storage temperatures. Eicosapentaenoic acid, docosahexaenoic acid and polyunsaturated fatty acids percentage remained similar in the extracted oils with the respective storage time or temperature treatments.

Contaminants in Used Oils and Their Behavior

Abstract Either particle count or gravimetric analysis is commonly used for assessing oil cleanliness. These analytical methods are useful and practical. However, the former provides the particle number of defined size groups and the latter the gross weight of the contaminants in a certain volume of oil, but they cannot inform us of the characteristics of contamination. To solve hydraulic and lubrication problems due to oil contamination, it is imperative to know the characteristics of contamination. Solvent extraction methods have been used to separate contaminants from used oils. Solvent extraction analysis showed that the majority of contaminants in used oils were polymerized oil oxidation products, which were not soluble in oil. Recently, problems of varnish formation in gas turbines has been of great interest. Varnish is the polymerized oil oxidation product. Such polymerized oil oxidation products have polarity, although base mineral oils are non-polar. Polar and non-polar materials are basically incompatible with each other. Polar materials behave independently in oils. The molecular weight of oil oxidation products was determined by GPC, and it was found that they were good for lubrication when they were soluble in oil but harmful when they became insoluble. However, contaminants must be considered on the level of molecular size in order to solve hydraulic and lubrication problems. This paper discusses the behavior of oil oxidation products in oils.

Relative contribution of compositional parameters to the primary and secondary oxidation of canola oil

The content of primary (PO) and secondary (SO) oxidation products of canola oil was measured, and a good correlation obtained between them ( R 2 = 0.991). Peroxide value showed the highest contribution (53.69%) to the PO, whereas its contribution to the SO was much less significant (0.36%). Acid value contribution to the production of hydroperoxides and carbonyls was 12.75% and 29.82%, respectively. Polyene index showed a relatively low contribution to the PO (6.71%) but contributed highly to the SO (21.82%). Tocopherols were more effective to prevent the production of hydroperoxides (14.77%) than of carbonyls (4.36%). In contrast, phenolics were found to be better than tocopherols to resist off-flavours production (11.64% vs. 3.36%). Total polar compounds had a pronounced contribution to creation of off-flavours (32.00%) as well as a marked effect on the PO (8.72%).

The influence of natural antioxidants on the oxidative stability of iodine-fortified sunflower oil in the process of storage

The task of obtaining oils with heightened antioxidative properties by incorporating natural antioxidative spice plant components into the receipt composition has been solved in order to decrease the intensity of possible oxidative reactions and increase the shelf life of iodine-fortified sunflower oil. It has been shown that natural antioxidants exert an effective influence on the stabilization of the investigated oils; i.e., the intensity of accumulation of primary and secondary oil oxidation products is inhibited.