Oxidative decomposition of cholesterol in fish products

Cholesterol oxides in fish products popular in Japan, including salted and dried, boiled and dried and smoked products, were qualitatively and quantitatively determined as trimethylsilyl ether derivatives by gas-liquid chromatography and mass spectrometry. The level of total cholesterol oxides ranged widely between 8.3 ppm in boiled and dried shrimp and 188.0 ppm in boiled and dried anchovy. 7β-Hydroxycholesterol and 7-ketocholesterol were the most prominent oxidative decomposition products of cholesterol. The levels of epimeric epoxides, cholestane triol and 25-hydroxycholesterol were relatively low. To elucidate a mechanism of cholesterol oxidation proceeding during fish processing and subsequent preservation, four model systems, consisting of a mixture of purified cod liver triglycerides plus cholesterol, of a mixture of authentic triolein plus cholesterol, of triolein alone and of cholesterol alone, were stored separately at 25°C in dry air for up to 104 d. The residual fatty acids of the triglycerides, and the cholesterol oxides produced, were recovered and determined. Oxygen uptake remained almost unchanged for the mixture of triolein plus cholesterol. No detectable amount of cholesterol oxides was produced, and the fatty acid content of the residual oleic acid, measured by an internal standard, remained almost unchanged. For the mixture of cod liver triglycerides plus cholesterol, a remarkable increase in oxygen uptake was observed. A continuous increase in the amount of cholesterol oxides was observed, accompanied by a remarkable concurrent decrease in polyunsaturated fatty acid residues, as well as of the oleic acid naturally present. These results strongly suggest that cholesterol oxidation in fish products proceeds in conjunction with oxidative decomposition of the coexisting polyunsaturated fatty acids of fish oils.     

Clinical application of C18 and C20 chain length polyunsaturated fatty acids and their biotechnological production in plants

A potential revolution in FA therapies is on the horizon. In recent years, the full magnitude of various FA treatments and their overall importance to health has become increasingly apparent. Fetal and infant nutrition studies have clearly shown that FA status at birth can have life-long health implications affecting eye and brain function, insulin resistance, and blood pressure control. As well, nutrition studies have identified dietary imbalances and deficiencies that have the potential to alter the health of future generations severely and to promote progression of age-related degenerative disorders. Mixtures of naturally occurring FA have shown promise as therapeutic agents for a diverse range of health conditions including atopic eczema, rheumatoid arthritis, cardiovascular disease, and neurological problems. Through the 1990s, the creation of technologies to concentrate and formulate pharmacologically active individual FA components as well as tailored combinations propelled development of this new drug category. However, high production costs and government regulatory encumbrance limited the expansion of this emerging pharmaceutical sector. Fortunately, many countries are now creating regulatory frameworks that are better suited for product evaluation and control of the manufacturing FA products than historical drug models, and hence expansion in this area is now anticipated.     

Enzymatic modification of triacylglycerols of high eicosapentaenoic and docosahexaenoic acids content to produce structured lipids

Immobilized lipase, IM60, from Rhizomucor miehei was used as a biocatalyst for the incorporation of capric acid (C10:0) into fish oil originally containing 40.9 mol% eicosapentaenoic (20:5n-3) and 33.0 mol% docosahexaenoic (22:6n-3) acid. Acidolysis was performed with and without organic solvent. Pancreatic lipase-catalyzed sn-2 positional analysis was performed after enzymatic modification. Tocopherol analysis was performed before and after enzymatic modification. Products were analyzed by gas-liquid chromatography. After a 24-h incubation in hexane, there was an average of 43.0±1.6 mol% incorporation of C10:0 into fish oil, while 20:5 and 22:6 decreased to 27.8±2.2 and 23.5±1.3 mol%, respectively. The solvent-free reaction produced an average of 31.8±8.5 mol% C10:0 incorporation, while 20:5 and 22:6 decreased to 33.2±3.3 and 28.3±3.9 mol%, respectively. The effect of incubation time, substrate molar ratio, enzyme load, and added water were also studied. In general, as the enzyme load, molar ratio, and incubation time increased, mol% C10:0 incorporation also increased. The optimal mol% C10:0 incorporation was 41.2% at 48 h for the reaction in hexane and 46.4% at 72 h for the solvent-free reaction. The highest C10:0 incorporation (65.4 mol%) occurred at a molar ratio of 1:8 (fish oil triacylglycerols/capric acid) in hexane. For the solvent-free reaction, the optimal mol% C10:0 incorporation (56.1 mol%) occurred at a molar ratio of 1:6. An enzyme load of 10% gave the highest mol% C10:0 incorporation (41.4 mol%) in hexane; the highest incorporation (38.3 mol%) for the solvent-free reaction occurred at 15% enzyme load. Mol% incorporation of C10:0 declined with increasing amounts of added water. The optimal mol% C10:0 incorporation occurred at 1% added water (47.9 mol%) for the reaction in hexane, and at zero added water for the solvent-free reaction (21.8 mol%). Fish oil containing capric acid was successfully produced and may be nutritionally more beneficial than unmodified oil.     

The effect of randomization on the stability of blends of trioleoylglycerol and linseed oil

The effect of fatty acid arrangement on triacylglycerols was determined by assessing the stability of mixtures of trioleoylglycerol (consisting of a comparatively stable fatty acid) and linseed oil (containing a high amount of unstable fatty acids in the form of linoleic and linolenic acids) in the ratios of 90:10, 85:15, 80:20, 70:30 and 60:40 (w/w), respectively, before and after enzymatic randomization. Randomization resulted in increased stability; however, increasing the content of the unstable triacylglycerol resulted in a decrease in this effect. Based on these results, it was concluded that randomization of triacylglycerols can have a positive effect on the oxidative stability of an oil if the content of autoxidatively unstable triacylglycerols is low in the original blend. This results in substantial dilution of unstable fatty acids among the more stable triacylglycerols upon randomization.     

Effects of frying and storage on cholesterol oxidation in minced meat products

The presence of cholesterol oxidation products (COP) in the diet is a health concern for their various known adverse effects. It is important that the generation of COP be assessed during different stages of production, handling, and storage of meats and meat products so that relevant measures can be taken to minimize the production of COP. In a preliminary study, we investigated the content of COP in the lipids of raw meatballs (50% prok+50% beef), prefried meatballs (50% pork +50% beef), raw hamburger (100% beef), and prefried burger (50% pork+50% beef). Six of the common COP, viz 7α- and 7β-hydroxycholesterol, 7-ketocholesterol, 5α,6α-epoxycholestanol, 5β,6β-epoxycholestanol, and cholestanetriol, were analyzed by gas chromatography (GC) and GC-mass spectroscopy. The total content of these COP was in the range of 7 to 10 μg/g lipids in raw meatballs, prefried meat balls, and raw hamburger, after frying these samples for consumption. The prefried hamburger had ca. 8μg/g lipids of the total COP before frying, and this amount increased to 29 μg/g lipids after frying. During the storage of this fried sample, the total COP increased to 42 and 50 μg/g lipids, after 1 and 2 wk of storage, respectively. The results of this study show that freshly prepared meat products are a minor source of COP in the diet. However, if semiprepared frozen meat products are fried once and then stored for future consumption, the levels of COP can increase considerably, and this may be of concern for certain groups of consumers. Presented in part as a poster at the 88th AOCS Annual Meeting and Exposeattle, WA, May 11–14, 1997.     

Autoxidation of the furan fatty acid ester, methyl 9,12-epoxyoctadeca-9,11-dienoate

The objective of this study was to identify autoxidation products of methyl 9,12-epoxyoctadeca-9,11-dienoate (F_9,12). Previous work has shown that F_9,12 is a product both of autoxidation and singlet oxygen oxidation of the methyl ester derivative of conjugated linoleic acid (CLA). F_9,12, 95% pure, was synthesized from methyl ricinoleate. The synthetic F_9,12 was heated at 50°C in sealed tubes containing air. Each tube contained 6 mg F_9,12 and 1 mg methyl stearate as an internal standard. Samples were taken at 4.5, 7, 23, 46.5, 69.5, and 93 h. The oxidized F_9,12 was dissolved in isooctane and analyzed by gas chromatography (GC), GC-direct deposition-Fourier transform infrared spectroscopy, and GC-electron ionization mass spectrometry. CLA methyl ester was oxidized in a similar manner. Under these conditions, the half-lives of CLA and F_9,12 were 40 and 35 h, respectively. Oxidation products of F_9,12 that were identified included: 5-hexyl-2-furaldehyde (I), methyl 8-oxooctanoate (II), methyl 13-oxo-9,12-epoxytrideca-9,11-dienoate (III), methyl 8-oxo-9,12-epoxy-9,11-octadecadienoate (IV), and methyl 13-oxo-9,12-epoxy-9,11-octadecadienoate (V).     

Supercritical fluid chromatographic analysis of fish oils

Various natural and processed fish oil triglyceride mixtures have been analyzed by capillary supercritical fluid chromatography (SFC). The analyses were performed on nonpolar columns to separate the components by lipid class and by the number of carbon atoms. The compounds separated included free fatty acids, squalene, α-tocopherol, cholesterol, wax esters, cholesteryl esters, di- and triglycerides. This kind of analysis is not possible by gas chromatography or high-performance liquid chromatography methods without prior treatment of the fish oil, making SFC superior for this application. Applications of SFC to fish oils are given, including a control analysis of the various process steps in the refining of a fish oil, analysis of a lipase-catalyzed transesterification of a fish oil and the detection of polymeric artifacts.     

Effect of chlorine dioxide treatment on lipid oxidation and fatty acid composition in salmon and red grouper fillets

Chlorine dioxide (CIO₂) has been explored as a potential substitute for aqueous chlorine to clean seafood products. In an attempt to understand the interaction of CIO₂ with organic compounds, duplicate fillets of Atlantic salmon (Salmo salar) and red grouper (Epinephelus morio) were treated for 5 min with freshly prepared aqueous CIO₂ at 20, 40, 100, and 200 ppm total available CIO₂ in 3.5% brine. Thiobarbituric acid (TBA) values and fatty acid composition were determined. CIO₂-treated salmon and red grouper showed a dose-related increase in TBA; the 100 and 200 ppm groups had significantly (P<0.05) greater TBA values than controls and the 20 ppm group. Treated red grouper and salmon did not differ in percentage monounsaturated and polyunsaturated fatty acids compared to controls, although differences occurred with some individual fatty acids. Thus, CIO₂ treatment did not greatly affect fatty acid composition of treated fillets.     

Dose-Dependent Effects of Docosahexaenoic Acid Supplementation on Blood Lipids in Statin-Treated Hyperlipidaemic Subjects

The objective of the study was to evaluate potential benefits of docosahexaenoic acid (DHA) rich fish oil supplementation as an adjunct to statin therapy for hyperlipidaemia. A total of 45 hyperlipidaemic patients on stable statin therapy with persistent elevation of plasma triglycerides (averaging 2.2 mmol/L) were randomised to take 4 g/day (n = 15) or 8 g/day (n = 15) of tuna oil or olive oil (placebo, n = 15) for 6 months. Plasma lipids, blood pressure and arterial compliance were assessed initially and after 3 and 6 months in 40 subjects who completed the trial. Plasma triglycerides were reduced 27% by 8 g/day DHA-rich fish oil (P < 0.05) but not by 4 g/day when compared with the placebo and this reduction was achieved by 3 months and was sustained at 6 months. Even though total cholesterol was already well controlled by the statin treatment (mean initial level 4.5 mmol/L), there was a further dose-dependent reduction with fish oil supplementation (r = −0.344, P < 0.05). The extent of total cholesterol reduction correlated (r = −0.44) with the initial total cholesterol levels (P < 0.005). In the subset with initial plasma cholesterol above 3.8 mmol/L, plasma very low density lipoprotein (VLDL), intermediate-density lipoprotein (IDL) and low-density lipoprotein (LDL) were isolated and assayed for cholesterol and apolipoprotein B (apoB) at the commencement of the trial and at 3 months of intervention. Fish oil tended to lower cholesterol and apoB in VLDL and raise both in LDL. There were no changes in IDL cholesterol, IDL apoB and high-density lipoprotein cholesterol. The results demonstrate that DHA-rich fish oil supplementation (2.16 g DHA/day) can improve plasma lipids in a dose-dependent manner in patients taking statins and these changes were achieved by 3 months. Fish oil in addition to statin therapy may be preferable to drug combinations for the treatment of combined hyperlipidaemia.     

Effect of synthetic antioxidants on cholesterol stability during the thermal-induced oxidation of a polyunsaturated vegetable oil

As a molecule with an unsaturated bond, cholesterol is prone to oxidation. Cholesterol oxidation products (COP) are found in many common foods and have been shown to be atherogenic, cytotoxic, mutagenic, and possibly carcinogenic. Efforts to reduce the formation of oxidation products are considered important during the manufacture and processing of foods. The effect of synthetic antioxidants on cholesterol oxidation has not been extensively studied. We assayed the effect of five commonly used antioxidants—BHT, BHA, the n-propyl ester of 3,4,5-trihydroxy benzoic acid (PG), TBHQ, and 6-ethoxy-1,2-dihydro-2,4-trimethylquinoline (EQ)—on cholesterol stability when oxidation is induced in a Rancimat 679 instrument by bubbling air through the sample at 150°C. The sample consisted of 200 mg cholesterol dispersed in 100 g of a polyunsaturated vegetable oil (soybean oil). Formation of six COP was measured at the induction period, and at the 50 and 100 μS conductivity values. Under the experimental conditions, BHT and TBHQ were the most effective inhibitors of cholesterol oxidation. BHA and EQ were less effective, and PG was unable to prevent cholesterol oxidation. Synthetic antioxidants were more effective in preventing COP formation at the nucleus of the cholesterol structure than at the lateral chain.     

Effect of triacylglycerol structures on the thermal oxidative stability of edible oil

Different molecular species of TAG were assessed to determine the influence of TAG structure on the thermal oxidative stability of edible oil. TAG containing palmitic acid (16∶0, P) as saturated FA (SFA) and oleic acid (18∶1, O), linoleic acid (18∶2, L), or linolenic acid (18∶3, Ln) as unsaturated FA (UFA) were chemically synthesized and then heated at 180 or 150°C. Thermal oxidative stability of TAG was determined by evaluating the resultant UFA, polar compound, FFA, carbonyl compound, polymerized compound, and tocopherol contents. When TAG containing 16∶0 and 18∶2 in the ratio of 2∶1 (mol/mol) were heated at 180°C, a 2∶1 (mol/mol) mixture of saturated TAG (PPP) and unsaturated TAG (LLL) was found to be more susceptible to thermal oxidation than PPP/PLL (1∶1) and PPL. Similarly, a 2∶1 mixture of PPP and OOO or LnLnLn was more unstable toward thermal oxidation than PPO or PPLn, respectively. Thermal oxidative stability of TAG containing SFA and UFA (2∶1) was negatively correlated with the moles of UFA in a single TAG molecule. This tendency was also observed at 150°C. From these results, it is suggested that the TAG structure could be one of the factors determining the thermal oxidative stability of edible oil.     

Effects of the molecular weight and the degree of deacetylation of chitosan oligosaccharides on antitumor activity

Effects of the degree of deacetylation (DDA) and the molecular mass of chitosan oligosaccharides (CTS-OS), obtained from the enzymatic hydrolysis of high molecular weight chitosan (HMWC), on antitumor activity was explored. The DDA and molecular weights of CTS-OS were determined by matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-TOF MS) analysis. The CTS-OS were found to be a mixture of mainly dimers (18.8%), trimers (24.8%), tetramers (24.9%), pentamers (17.7%), hexamers (7.1%), heptamers (3.3%), and octamers (3.4%). The CTS-OS were further fractionated by gel-filtration chromatography into two major fractions: (1) COS, consisting of glucosamine (GlcN)(n), n = 3-5 with DDA 100%; and (2) HOS, consisting of (GlcN)(5) as the minimum residues and varying number of N-acetylglucosamine (GlcNAc)(n), n = 1-2 with DDA about 87.5% in random order. The cytotoxicities, expressed as the concentration needed for 50% cell death (CC(50)), of CTS-OS, COS, and HOS against PC3 (prostate cancer cell), A549 (lung cancer cell), and HepG2 (hepatoma cell), were determined to be 25 μg·mL(-1), 25 μg·mL(-1), and 50 μg·mL(-1), respectively. The HMWC was approximately 50% less effective than both CTS-OS and COS. These results demonstrate that the molecular weight and DDA of chitosan oligosaccharides are important factors for suppressing cancer cell growth.     

镍基催化剂加氢还原氯代硝基苯时脱氯机制的研究

Ni-B/SiO2非晶态合金对一系列氯代芳烃硝基化合物进行加氢,脱氯顺序依次为:2-氯-5-硝基甲苯>邻氯硝基苯>间氯硝基苯=对氯硝基苯>2,5-二氯硝基苯。将Ni-B/SiO2非晶态合金和Raney Ni催化加氢邻氯硝基苯进行了对比,发现在—NO2转化成—NH2的反应终了之前,用非晶态镍催化剂的脱氯速度小于用Raney Ni催化剂的脱氯速度,但加氢反应终了之后,在非晶态镍催化剂上的脱氯速度大于Raney Ni催化剂上的脱氯速度。镍基催化剂的软硬度是催化剂选择性好坏的主要原因,镍基催化剂软度大有利于催化剂选择性的提高。     

Effect of degree of deacetylation of chitosan on the kinetics of ultrasonic degradation of chitosan

The objective of the study was to explore the effect of the degree of deacetylation (DD) of the chitosan used on the degradation rate and rate constant during ultrasonic degradation. Chitin was extracted from red shrimp process waste. Four different DD chitosans were prepared from chitin by alkali deacetylation. Those chitosans were degraded by ultrasonic radiation to different molecular weights. Changes of the molecular weight were determined by light scattering, and data of molecular weight changes were used to calculate the degradation rate and rate constant. The results were as follows: The molecular weight of chitosans decreased with an increasing ultrasonication time. The curves of the molecular weight versus the ultrasonication time were broken at 1‐h treatment. The degradation rate and rate constant of sonolysis decreased with an increasing ultrasonication time. This may be because the chances of being attacked by the cavitation energy increased with an increasing molecular weight species and may be because smaller molecular weight species have shorter relaxation times and, thus, can alleviate the sonication stress easier. However, the degradation rate and rate constant of sonolysis increased with an increasing DD of the chitosan used. This may be because the flexibilitier molecules of higher DD chitosans are more susceptible to the shear force of elongation flow generated by the cavitation field or due to the bond energy difference of acetamido and β‐1,4‐glucoside linkage or hydrogen bonds. Breakage of the β‐1,4‐glucoside linkage will result in lower molecular weight and an increasing reaction rate and rate constant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3526–3531, 2003     

4种炭素材料的抗氧化性能研究

在熔炼炉中对电极石墨、模压石墨、挤压石墨、等静压石墨4种炭素材料从室温逐渐加热至700℃,并在一定温度下保温1h,测其质量,绘制材料质量变化曲线图,以质量变化表征其抗氧化性的强弱.通过SEM、XRD等手段分析这几种炭素材料抗氧化性差异的本质原因.研究表明,这4种炭素材料的抗氧化性强弱顺序为等静压石墨、电极石墨、挤压石墨、模压石墨,影响石墨材料的抗氧化性能主要因素有石墨材料的石墨化程度、晶体结构缺陷、体积密度及杂质含量等.     

Catalytic oxidation of CO on CuOx revisited: Impact of the surface state on the apparent kinetic parameters

Analysis of kinetic features of the copper oxides reduction by CO pulses as related to mechanism of CO catalytic oxidation by oxygen combined with monitoring the state of the surface by an electrochemical technique using a solid electrolyte—Pyrex glass and high resolution TEM data on the defect structure of CuO allowed us to suggest a partially “flexible” model of CuO surface. This model, with a due regard for the data of FTIR spectroscopy of adsorbed CO test molecules, assigns the most active surface sites able to coordinate highly reactive CO and O forms to clusters of Cu⁺ cations located at outlets of extended defects (dislocations, twins). Variation of the number, size and structure of these clusters under the reaction medium effect allows explaining the difference between quasi-steady and true steady states of copper oxides in catalytic CO oxidation reaction as well as the difference between kinetic parameters of reaction estimated at quasi-steady and constant states of the surface following Boreskov's approach. Kinetic features of the reaction agree with the Langmuir–Hinshelwood reaction mechanism operating for clustered defect centers of CuO.     

Water‐soluble sulfonated phenolic resins. III. Effects of degree of sulfonation and molecular weight on concrete workability

The effects of the degree of sulfonation (DS) and molecular weight (MW) of sulfonated phenolic resins (SPF) on the flow properties of cementitious materials were investigated. SPF resin was prepared from phenol, formaldehyde, and sodium bisulfite through a four‐step reaction. It was found that an increase in either DS or MW would enhance the dispersion effects in the system. The results indicate that the fluidity of cement pastes and the workability of concrete increased with higher DS until the resin was fully sulfonated. For resins with sufficient sulfonation, the performance of cementitious materials would increase with increasing MW. Apparently, resins with MW of about 3 × 10⁴ are most effective in promoting concrete properties in terms of workability and compressive strength. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1762–1766, 2000     

聚合物水解度对有机铬交联剂成胶性能的影响

通过聚合物水解度对成胶性能的影响研究,认为聚合物在低浓度下都有最佳的水解度范围,为现场交联剂聚合物驱工业化应用筛选聚合物水解度提供依据,从而最大限度的降低成本,充分发挥交联聚合物驱的效果。     

Effect of tocopherols on the frying stability of regular and modified canola oils

A study was conducted to compare the relationship between frying stability and levels and degradation rates of tocopherols in regular and three modified canola oils. Oils were heated at 175 ± 2°C for a total of 72 h, with french fries fried intermittently. Frying stability was compared based on the rates of formation of free fatty acids (FFA) and total polar compounds (TPC). Significant differences (P<0.05) were identified between oils using analysis of covariance and t-tests for multiple comparisons. No significant differences were observed in the rates of FFA formation among the canola oils during frying. Nevertheless, regular canola (RCO) and high-oleic, low-linolenic acid canola (HOLLCO) oils produced less FFA compared to higholeic LLCO and HOCO both had significantly (P<0.05) faster rates of TPC formation compared to HOLLCO or RCO. HOLLCO with the highest level of tocopherols (893 mg/kg) exhibited a slow rate of degradation which accounted for a halflife of 48–60 h of frying. RCO, with a lower level of tocopherols (565 mg/kg), however, had the slowest degradation rate with a half-liofe of >72 h. In contrast, HOCO and LLCO with 601 and 468 mg/kg tocopherols, respectively, both exhibited a half-life for tocopherols of 3–6 h of frying. An inverse relatioship was observed between TPC formation and the reduction of tocopherol. Thus, the greater frying stability of RCO and HOLLCO appears to be affected far more by the rate of tocopherol degradation than by any changes in fatty acid composition.     

Studies on the effect of substitution degree on the liquid crystalline behavior of cyanoethyl chitosan

An alkali–chitosan method was employed to prepare cyanoethyl chitosan (CNCS) with different degrees of substitution (DS) from chitosan by controlling the reaction time. The effect of the DS (from 0.36 to 1.21) on the liquid crystalline behaviors of CNCS was investigated. The critical concentration and texture of CNCS liquid crystalline in dichloroacetic acid and formic acid showed no obvious dependence on the DS. However, increase of the DS could enhance the birefringence of liquid crystalline solutions under a polarized microscope, which implied improved liquid crystallinity. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 2057–2061, 2000