Purification process for cod liver oil polyunsaturated fatty acids

The polyunsaturated fatty acids (PUFA) eicosapentaenoic acid (EPA, 20∶5n−3) and docosahexaenoic acid (DHA, 22∶6n−3), which have several pharmaceutical properties, have been purified from cod liver oil. The process consisted of four main steps: (i) saponification of the oil, (ii) use of urea inclusion adducts method to obtain PUFA, (iii) PUFA methylation, and (iv) argentation silica gel column chromatography of the methylated PUFA. Argentation silica gel chromatography yielded highly pure DHA in the process (100% purity, 64% yiild). For EPA, the recovery in the combined process was 29.6%, and the final purity was 90.6%, owing to the simultaneous elution of other polyunsaturated fatty esters. The recovery in the urea inclusion method was strongly enhanced by application of orbital agitation during the crystallization process, in which EPA yield increased from 60–70% without agitation to 90–97% at 800 rpm; stearidonic acid (18∶4n−3) yield ranged from 60–75% without agitation to 87–95% at 800 rpm, and DHA yield varied from 53–73% without agitation to 85–99% at 800 rpm     

Autoxidation of cod liver oil with tocopherol and ascorbyl palmitate

Cod liver oil (CLO) with no added antioxidants (REF), 200 mg/kg ascorbyl palmitate (AP), and/or 800 mg/kg tocopherol concentrate (TOH) were stored in sealed bottles with a small headspace of air at 25°C in the dark. A binary mix of TOH +AP affected the sensory perception of CLO by leading to a more grass/cucumber-like and less herring oil-like impression, whereas TOH alone had no effect. This was caused by the different influence of the antioxidants with regard to formation of volatile oxidation products. TOH+AP promoted formation of, e.g., hexanal, 2-hexenal, and 2,6-nonadienal and inhibited formation of, e.g., 2,4-heptadienal. TOH affected the proportions of trans, cis-and trans,trans-2,4-heptadienal that were formed and inhibited formation of, e.g., 1-penten-3-ol, whereas formation of acetic acid and some other volatiles was inhibited by both antioxidants. The total amount of volatiles increased during the experiment, and with REF were significantly higher (P<0.05) than with TOH. The PV increased during the first 2 wk of storage. PV levels were in the order of TOH>REF>TOH+AP. The observed effects could partly be explained by hydrogen donation from TOH to peroxyl radicals, but the mode of action for AP was unclear.     

Evaluation of antioxidants for cod liver oil by chemiluminescence and the rancimat method

Commercial blends of natural antioxidants,viz., tocopherol concentrates, rosemary extracts, sage extracts, and lecithins, were tested for their ability to stabilize cod liver oil. The antioxidants were tested by using the Rancimat apparatus at 80°C and by a method based on hypochlorite-activated chemiluminescence analysis of samples stored at 35°C for 24 h in light. In addition, a stability study at 5°C in the dark for 8 wk, under conditions realistic for normal consumption of cod liver oil was carried out. A low correlation (r=0.339) was found between Rancimat induction times and chemiluminescence data for the sixteen antioxidant systems tested, probably due to temperature differences, and different ways of detecting oxidation products. Based on Rancimat induction times, δ-tocopherol-rich antioxidants and lecithin had the best stabilizing effect. However, based on the chemiluminescence method, the tocopherols acted as prooxidants, while tocopherols with lecithin increased the stability. Both Racimat and chemiluminescence data showed stabilizing effects with rosemary and sage extracts, but no synergistic effect between the herbal extracts and lecithin or tocopherol was observed. Analyses of oil aged at 5°C for 8 wk showed the highest stability for cod liver oil containing rose-mary extracts. The tocopherol mixtures showed only a minor effect on the stability. Ranking of antioxidants varied considerably depending on the method used, and increasing the temperature seemed to decrease the usefulness of the method. Antioxidant evaluation has to be done by using as many evaluation methods as possible under conditions relevant for normal storage and use.     

Behaviour of cod liver oil during the autoxidation process

Prostaglandin‐like compounds, called isoprostanes, are generated by free enzyme‐independent radical peroxidation of the acids arachidonic (AA), eicosapentaenoic (EPA) and docosahexaenoic (DHA). Up to now, isoprostanes have been largely studied only in men and biological systems, but never in food. In this research, cod liver oil was used as a model system to study the oxidation mechanism in food containing high amounts of EPA and DHA. For comparison, under similar oxidation conditions, also the behaviour of a sunflower seed oil and an n‐3 long‐chain polyunsaturated fatty acid capsule supplement oil were studied. It was ascertained that EPA‐ and DHA‐derived compounds were formed during oxidation. These compounds were polar and easily isolatable by methanol from oxidised transmethylated oil. EPA and DHA oxidation derivatives showed maximal absorbance at 200 nm and were very potent pro‐oxidants at high temperatures. In oxidised sunflower oil, similar compounds did not form. Unfortunately, the chemical structures of the EPA and DHA oxidation derivatives were not discovered, but it is a realistic hypothesis that they could be isoprostane‐like compounds.     

Lipase-catalyzed alcoholysis of cod liver oil in supercritical carbon dioxide

Enzymatic alcoholysis of cod liver oil, with an immobilized lipase, was carried out in supercritical carbon dioxide. The enzyme was catalytically active under the experimental conditions used. The reaction medium was investigated to preferentially extract ethyl esters, synthesized during the course of the experiment, from the unconverted cod liver oil substrate and side-products. The effect of pressure changes on the amount of tri-, di-, and monoglycerides and ethyl esters, present in both the extract and the remaining lipid residue, was determined. Furthermore, the fatty acid compositions of the lipid classes were analyzed, and the relative amounts of both eicosapentaenoic acid and docosahexaenoic acid to palmitic acid were determined. The results show that it is possible to preferentially extract the synthesized ethyl esters at low pressures. The extract collected at 9 MPa contained 64 g ethyl esters/100 g extract, while the total amount of all other lipid classes detected was 19 g/100 g extract. As the pressure was increased, the relative amount of the other lipid classes detected in the extract, especially triglycerides, was enhanced. The relative amounts of both eicosapentaenoic acid and docosahexaenoic acid to palmitic acid increased for some lipid classes in the extract. This increase was most pronounced for the monoglyceride lipid class. The integration of biocatalysis and product fractionation, applied in this study, suggests that the potential for biocatalysis in industrial processes is considerably wider than had been thought.     

The effect of glycine in the production of toxic volatile aldehydes from heated corn oil

The fatty aldehydes generated from heated corn oil and from several corn oil/glycine mixtures were collected by a dynamic headspace sampling method and subsequently reacted with cysteamine to yield corresponding thiazolidines. Derivatized aldehydes were analyzed by a capillary gas chromatograph with flame photometric detector. Six fatty aldehydes, including formaldehyde and acetaldehyde, decreased in concentration in relation to increasing amounts of glycine in the oil.     

Concentration and purification of stearidonic,eicosapentaenoic, and docosahexaenoic acids from cod liver oil and the marine microalgaIsochrysis galbana

n-3 Polyunsaturated fatty acids (n-3 PUFA) from the marine microalgaIsochrysis galbana were concentrated and purified by a two-step process—formation of urea inclusion compounds followed by preparative high-performance liquid chromatography. These methods had been developed previously with fatty acids from cod liver oil. By the urea inclusion compounds method, a mixture that contained 94% (w/w) stearidonic (SA), eicosapentaenoic (EPA), plus docosahexaenoic (DHA) acids (4:1 urea/fatty acid ratio and 4°C crystallization final temperature) was obtained from cod liver oil fatty acids. Further purification of SA, EPA, and DHA was achieved with reverse-phase C₁₈ columns. These isolations were scaled up to a semi-preparative column. A PUFA concentrate was isolated fromI. galbana with methanol/water (80:20, w/w) or ethanol/water (70:30, w/w). With methanol/water, a 96% EPA fraction with 100% yield was obtained, as well as a 94% pure DHA fraction with a 94% yield. With ethanol/water as the mobile phase, EPA and DHA fractions obtained were 92% pure with yields of 84 and 88%, respectively.     

Concentration of squalene from shark liver oil by short‐path distillation

Investigations on the concentration of squalene from shark liver oil using short‐path distillation are presented and compared to alternative techniques. Aspects of chemical composition analysis are discussed as well as physical and sensory properties. A product is obtained with squalene purities above 97% at feed flows of up to 7 kg/h and temperatures between 185 and 230 °C. In order to assure product quality, a simple refractive method is applied. Based on the presented study, scale‐up to industrial production is performed taking into account the complete process for obtaining an acceptable product with a neutral odor.     

Formation of 4-hydroxynonenal, a toxic aldehyde, in soybean oil at frying temperature

The formation of 4-hydroxy-2-trans-nonenal (HNE), a mutagenic and cytotoxic product of the peroxidation of linoleic acid, was monitored in soybean oil that was heated at 185°C for 2, 4, 6, 8, and 10 h. Unheated soybean oil contained no HNE and a relatively low concentration of polar lipophilic secondary oxidation products (aldehydes and related carbonyl compounds), measured as 2,4-dinitrophenylhydrazine derivatives by HPLC. An increase in the concentration of both HNE and total lipophilic polar oxidation products was observed with increased exposure to frying temperature. A considerable concentration of HNE had already formed at 2 h and the concentration continued to increase at 4 and 6 h of heating. After 6 h the concentration of HNE decreased, possibly due to degradation of the aldehyde with further exposure to high temperature. The loss of endogenous tocopherols was also monitored in the heated oil, and the tocopherol concentration decreased as the secondary lipid oxidation products increased.     

Quantitation of flavor volatiles in oxidized soybean oil by dynamic headspace analysis

A dynamic headspace procedure was developed for isolating the volatiles from oxidized soybean oil and trapping them on an adsorbent under conditions that gave minimal decomposition of hydroperoxides (50°C for 30 min at a helium flow of 75 mL/min). The volatiles were desorbed from the adsorbent and separated by gas chromatography (GC) on a methyl silicone capillary column. Equations were derived from theoretical considerations that allowed the actual concentration of each flavor component in the oxidized oil to be calculated from the area of the GC peaks. The reliability of the method and calculations was demonstrated by recovery experiments. The concentration of 2-heptanone in a mineral oil emulsion, equivalent in flavor intensity to each component, was calculated and summed to estimate the overall flavor intensity of the samples. The overall estimations were compared with the concentrations of 2-heptanone observed to be equivalent in flavor intensity to the oxidized oil samples when these were tasted in emulsion. The concentrations of individual components calculated from the headspace volatiles data were all present at concentrations below their flavor thresholds, and the simple sum of the intensities of their flavors generally accounted for less than half of the flavor intensities of the oil samples. The differences in the headspace and sensory analyses might be attributed to the flavor of the unoxidized oil, synergistic interactions, and/or the presence of unmeasured flavors components.     

Increasing n-3 polyunsaturated fatty acid content of fish oil by temperature control of lipase-catalyzed acidolysis

An attempt was made to further increase the content of n-3 polyunsaturated fatty acid (n-3 PUFA) of fish oil by lipase-catalyzed acidolysis (reaction between fish oil and n-3 PUFA-enriched free fatty acid) without solvent. A bioreactor system was constructed composed of a water-jacketed packed-bed column and a substrate reservoir with a circulation pipeline between the packed-bed column and the reservoir. By keeping the temperature of the reservoir at −10°C (for the first 20 h), followed by −20°C (for the subsequent 40 h) during the batch acidolysis, crystals of free fatty acid appeared, which were removed intermittently by a cotton plug packed in the tip of the outlet pipe in the reservoir. The n-3 PUFA content of the triacylglycerol fraction increased a further 10% by the reduced temperature of the reservoir. Bioreactors for Enzymatic Reaction of Fats and Fatty Acid derivatives, Part XV.     

Simultaneous determination of lipophilic aldehydes by high-performance liquid chromatography in vegetable oil

A very sensitive high-performance liquid chromatography (HPLC) method was developed for the simultaneous separation and measurement of nonpolar and polar lipophilic secondary lipid peroxidation products in vegetable oil. Seventeen nonpolar and 13 polar lipophilic aldehydes and related carbonyl compounds, derived from thermally oxidized soybean oil as 2,4-dinitrophenyl hydrazones, were separated simultaneously by reversed-phase HPLC. Detection limit for the individual compounds is 1 ng. Thirteen of the nonpolar carbonyl compounds were identified as: butanal, 2-butanone, pentanal, 2-pentanone, hexenal, hexanal, 2,4-heptadienal, 2-heptenal, octanal, 2-nonenal, 2,4-decadienal, decanal, and undecanal. Three of the polar carbonyl compounds were identified as: 4-hydroxy-2-hexenal, 4-hydroxy-2-octenal, and 4-hydroxy-2-nonenal. The detection of the toxic 4-hydroxy-2-nonenal, a major compound, and 4-hydroxy-2-hexenal, a minor compound, in heated soybean oil is of particular importance because these toxic compounds have been shown to be absorbed from the diet.     

固态紫外光谱法在炼油催化剂表征中的应用

总结了有关固态紫外光谱法在炼油催化剂表征中的应用，包括载体与催化剂的吸附、金属界面、金属中心、孔道结构、负载型过渡金属催化剂及杂多型分子筛等，并对其应用方法和技术进行了评述。     

用紫外分光光度法测定水和废水中矿物油类的方法

本文以CJ267-91为依据研究了溶剂、标准品的制备及波长三方面对测定矿物油类的影响,从而选择适宜的条件,提高了测定结果的准确度。     

Role of minor constituents in the photooxidation of virgin olive oil

Virgin olive oil was photooxidized at 2 and 40°C and at fluorescent light intensities of 0, 620, 2710, and 5340 lux. As expected, higher fluorescent light intensities induced higher peroxide formation in the oil. The thiobarbituric acid reactive substances (TBARS) were found to be good indicators of photooxidation during the early stage of the reaction. Pheophytin A and β-carotene were light- and temperature-sensitive, whereas α-tocopherol and total polyphenols were mostly affected by light. Pheophytin A functioned as a photosensitizer, resulting in rapid oxidation of the oil. β-Carotene was a strong natural inhibitor of photooxidation for all light intensities at 2°C, suggesting quenching properties for singlet oxygen. However, β-carotene antioxidant activity was reduced at 40°C because of its rapid destruction.     

无机盐存在下微波辐射超稠原油脱水研究

由于超稠油粘度高、密度大，胶质、沥青质含量高，油水界面膜强度大，常规化学沉降脱水法以及电化学脱水法难以达到理想的脱水效果。采用添加无机盐的微波辐射法脱水，脱水效果大大提高。微波辐射3min，系统压强0．1MPa，辐射功率225W，静置沉降1min，研究了氯化钠、碘化钠、醋酸钠、硝酸钠、碳酸钠、硫酸钠6种钠盐以及氯化钠、氯化钾、氯化钙、氯化钡、氯化镁、氯化铝6种氯化物对微波辐射超稠原油脱水率以及对脱出水的透光率的影响，简要分析了无机盐作用下W／O型乳状液吸收微波的机理。结果表明，极少量的无机盐能大大提高原油的微波破乳效果，尤其是在醋酸钠的存在下，脱水率达到了99．43％。阳离子对微波破乳的影响与阳离子的极化力有关，阴离子对微波破乳的影响与阴离子半径大小有关。     

Enzymatic acidolysis in hexane to produce n−3 or n−6 FA-enriched structured lipids from coconut oil: Optimization of reactions by response surface methodology

Response surface methodology is a statistical design that helps one to determine optimal conditions for an enzyme-catalyzed reaction by performing a minimal number of experiments. This methodology was adapted for modifying coconut oil TAG by using lipase-catalyzed acidolysis in hexane to incorporate n−3 or n−6 PUFA. FFA obtained after hydrolysis of cod liver oil and safflower oil were used as acyl donors. Immobilized lipase, Lipozyme IM60, from Rhizomucor miehei was used for catalyzing the reaction. The reaction conditions—substrate molar ratio, incubation time, and temperature—were optimized. The experimental data were fitted to a response function based on the central composite rotatable design. The optimal conditions generated from models indicated that maximal incorporation of n−3 PUFA occurred at a 1∶4 molar ratio of TAG/FFA when incubation was carried out for 34 h at 54°C. Similarly, maximal incorporation of n−6 FA was predicted at a 1∶3 molar ratio of TAG/FFA when incubated for 48.5 h at 39°C. Experiments conducted at optimized conditions predicted by the equation obtained from response surface methodology yielded structured lipids with 13.65 and 45.5% of n−3 and n−6 FA, respectively. These values agreed well with that predicted by the model. The reactions were also scaled up to 100 g levels in batch reactors with the incorporation level of n−3 and n−6 fatty acids agreeing closely with that observed when the reactions were carried out at lab scale (100 mg). These studies indicated that response surface methodology is a useful tool in predicting the conditions for incorporating desired levels of specific FA during the synthesis of structured lipids.     

丘陵油田三间房组自然电位异常水淹层判别方法

丘陵油田经多年注水开发,目前已进入中高期含水阶段。受注入水影响,储层形成多压力系统。由于低矿化度注入水的影响,水淹层的扩散吸附电位发生不同程度变异;因加密调整井泥浆密度较高,过滤电位对自然电位的影响不能忽略。过滤电位和变异的扩散吸附电位叠加造成自然电位异常,会影响储层解释结果的正确性。统计所有自然电位异常层的试油情况,分析试油结果与测井响应特征关系,提出判别自然电位异常储层含油性的方法。     

Iron accumulation in oil during the deep-fat frying of meat

Iron accumulation in oil is a potential problem when frying food containing substantial amounts of iron. Selected meat products (skinless chicken breast, beef liver, and lean beef) were ground and fried (ca. 2-cm spheres, ca. 10 g/sphere) in partially hydrogenated soybean oil (PHSBO). Samples (450 g) of ground meat were fried 3 times/h for 8 h/d for 3 d. Oil samples were collected for analysis for iron (every 8 h) and oil degradation (every 4 h) and replaced with fresh oil. The iron contents of oil samples after 3 d of frying were approximately 0.11, 0.48, and 4.01 mg of iron/kg of PHSBO for the oil used to fry chicken, beef, and liver, respectively. There was a notable darkening in color and an increased tendency to foam for the beef liver oil sample compared with the other samples. After frying, the acid values were 0.9, 1.1, and 1.4 for the oil samples for chicken, beef, and liver, respectively. After frying, the p-anisidine values were 11.5, 12.8, and 32.6 for the oil samples for chicken, beef, and liver, respectively; the food oil sensor values were 0.96, 0.96, and 0.83 for the oil samples for chicken, beef, and liver, respectively.