Effect of initial slight oxidation on stability of polyunsaturated fatty acid/protein mixtures under controlled atmospheres

A mixture of unsaturated fatty acids (FA), mainly linolenic acid, and bovine serum albumin (BSA) was incubated under several different atmospheres to study the effect of these atmospheres on the stability of FA to oxidation. Four experiments were carried out simultaneously, which consisted of the incubation of the FA/BSA mixture under air, nitrogen, air in the presence of 200 ppm of butylated hydroxytoluene, and air for 6 h and then under nitrogen. The four experiments were tested for lipid oxidation and color changes by measuring absorbances at 234 and 270 nm, formation of thiobarbituric acid-reactive substances, and color differences and yellowness index. The samples that were oxidized with air before storage under nitrogen were the most stable against lipid peroxidation and exhibited the smallest color changes. These results suggest that a slight and controlled lipid oxidation improved the oxidative stability of FA/BSA mixtures.     

Fatty acid composition and oxidation of lipids in Korean catfish

This study determined the lipid content and FA composition of muscle and a mixture of muscle and viscera from Korean catfish as well as lipid oxidation and hydrolysis. Lipid content and FA compositions in Korean catfish, which were purchased every month or two during September 1999–July 2000, were analyzed. Lipid oxidation and hydrolysis were determined as PV, thiobarbituric acid value, and FFA in the muscle and the mixture during storage at 2°C for 12 d and −14°C for 9 wk. Lipid contents of the muscle and the mixture were 3.2 (w/w) and 5.4%, respectively. Oleic acid was the most abundant FA in the catfish lipids, constituting 28.0% (w/w) of total FA in the muscle and 25.6% in the mixture, followed by palmitic acid and linoleic acid, amounting to 20.2 and 12.2%, respectively, in the muscle and 20.2 and 12.5% in the mixture. EPA and DHA were 3.2 and 6.8%, respectively, in the muscle and 3.5 and 8.1% in the mixture. Seasonal variation in lipid contents and FA composition was minimal in catfish. Lipids in minced catfish oxidized and hydrolyzed readily at 2°C. Inclusion of viscera into the muscle increased lipid oxidation and hydrolysis. Frozen storage at −14°C and addition of ascorbic acid both reduced lipid oxidation. Frozen storage retarded lipid hydrolysis in catfish.     

Influence of Drying Conditions on the Hazelnut Quality. I. Lipid Oxidation

The influence of the drying conditions on the oxidation state of the lipidic fraction in hazelnut (Corylus avellana, L.) has been studied. Different hazelnut quality parameters (acidity index, KZI2 index, K270 index and oxidation stability) have been determined in unshelled and shelled hazelnuts dried under six drying air temperatures (30, 40, 50, 60, 70 and 80°). The drying experiments were done with forced air circulation, and two varieties of hazelnut were investigated, Negret and Pauetet. It has been observed that hydrolytic reactions affect dried Negret hazelnut, increasing with drying temperature. Also, drying temperatures higher than 50°C favour an increase of the rate of lipid oxidation in hazelnut, specially in shelled hazelnuts, with a decrease of the oxidation stability.     

Influence of Drying Conditions on the Hazelnut Quality. I. Lipid Oxidation

ABSTRACT

The influence of the drying conditions on the oxidation state of the lipidic fraction in hazelnut (Corylus avellana, L.) has been studied. Different hazelnut quality parameters (acidity index, KZI2 index, K270 index and oxidation stability) have been determined in unshelled and shelled hazelnuts dried under six drying air temperatures (30, 40, 50, 60, 70 and 80°). The drying experiments were done with forced air circulation, and two varieties of hazelnut were investigated, Negret and Pauetet. It has been observed that hydrolytic reactions affect dried Negret hazelnut, increasing with drying temperature. Also, drying temperatures higher than 50°C favour an increase of the rate of lipid oxidation in hazelnut, specially in shelled hazelnuts, with a decrease of the oxidation stability.     

Thermal stability of a novel poly(ether ether Ketone Ketone) (PK99)

The degradation of PK99 was studied by heating the polymer in both isothermal and dynamic conditions under nitrogen flow and in a static air atmosphere. In both environments this polymer's thermal stability exceeded that of PEEK. The dynamic experiments showed that in both nitrogen and air atmospheres the polymer degraded in two stages with formation of the same residue, which was quite stable under nitrogen, while almost completely burned in air. Good agreement was observed with the isothermal experiments. Apparent activation energy values were evaluated. The double linear relationships obtained by the Kissinger equation suggested a complex degradation process.     

Physicochemical Properties,Lipid Oxidation,and Fatty Acid Composition of Sausage Prepared with Meat of Young Nellore Bulls Fed a Diet with Lauric Acid

This study evaluates the quality of sausage obtained from the meat of Nellore cattle fed diets containing different levels (0, 5, 10, and 15 g per kg total DM) of lauric acid (C12:0) from palm kernel cake. A linear reduction (p ≤ 0.05) in lipid oxidation, as reflected by linear decreases in the lightness (L*), yellowness (b*), and saturation (C*) color parameters, is observed on days 7, 14, and 21 of maturation of sausage, and these decreases are accompanied by linear increases in the redness (a*) color and the linoleic (C18:2n–6) and linolenic (C18:3n–3) fatty acid contents. The inclusion of lauric acid in the diet induces linear reductions in the shear force and cooking loss and does not significantly affect various indices, including the centesimal composition, water activity, water holding capacity, composition of most fatty acids (FA), hypocholesterolemic‐to‐hypercholesterolemic FA ratio, atherogenicity, thrombogenicity, and desirable fatty acids. The use of dietary lauric acid from palm kernel cake is recommended at doses up to 15 g per kg because its presence reduces lipid oxidation and improves color parameters, softness, and linoleic and linolenic FA without affecting the FA composition of sausage from Nellore bull's meat. Practical applications : Sausages are products manufactured from chopped or ground meats packaged into animal casings. This product appeared in Brazil through the adaptation of traditional recipes brought by German and Italian immigrant families to weather conditions and the national palate. However, due to its production characteristics, sausage can become a product with lipid characteristics that are undesirable for human consumption. The inclusion of lauric acid (C12:0) in the animal diet might change the biohydrogenation process in the rumen, improve the quality of the deposited FA and reduce lipid oxidation in sausage manufactured from meat. The FA composition and physicochemical properties of sausage predict its acceptance by the consumer market. An optimal advantage would be achieved if these products can be used as not only preservatives but also functional ingredients with antioxidant properties and products for the treatment of metabolic syndrome and cardiovascular diseases through atherogenic action.     

Conjugated linoleic acid reduces hepatic steatosis, improves liver function, and favorably modifies lipid metabolism in obese insulin-resistant rats

CLA has been shown to induce or suppress excess liver lipid accumulation in various animal models. Interestingly, the state of insulin resistance may be an important modulator of this effect. The objective of the current study was to determine how feeding a dietary CLA mixture would affect liver lipid accumulation in insulin-resistant/obese and lean rats in relation to liver function, lipidemia, liver TAG and phospholipid FA composition, and expression of hepatic markers of FA transport, oxidation, and synthesis. Six-week-old fa/fa and lean Zucker rats (n=20/genotype) were fed either a 1.5% CLA mixture or a control diet for 8 wk. CLA supplementation reduced liver lipid concentration of fa/fa rats by 62% in concurrence with improved liver function (lower serum alanine aminotransferase and alkaline phosphatase) and favorable modification of the serum lipoprotein profile (reduced VLDL and LDL and elevated HDL) compared with control-fed fa/fa rats. The fa/fa genotype had two-thirds the amount of CLA (as % total FA) incorporated into liver TAG and phospholipids compared with the lean genotype. In both genotypes, CLA altered the hepatic FA profile (TAG greater than phospholipids) and these changes were explained by a desaturase enzyme index. Liver-FA-binding protein and acyl CoA oxidase, markers of FA transport and oxidation, respectively, were expressed at higher levels in CLA-fed fa/fa rats. In summary, these results illustrate a strong relationship between the state of insulin resistance and liver lipid metabolism and suggest that CLA acts to favorably modify lipid metabolism in fa/fa Zucker rats.     

Release of nitrogen during thermochemical conversion of Shenhua bituminous coal under Ar,CO2, and air atmospheres

Coal thermochemical conversion processes unavoidably generate gaseous pollutants, endangering the environment or influencing synthetic processes downstream. In order to display the differences in release behaviours of nitrogen among different coal thermochemical conversion stages, the nitrogen release characteristics of Shenhua bituminous coal under Ar, CO₂, and air atmospheres were investigated using X-ray photoelectron spectrum (XPS) and thermogravimetry-mass spectrometry (TG-MS). Results indicate that the reaction atmosphere has an important influence on nitrogen release. The total released mass of nitrogen when using 100 g raw coal in the whole experiment under Ar, CO₂, and air atmospheres is 0.54, 0.64, and 0.75 g, respectively. The organic forms of nitrogen in raw coal and coal char are pyridine nitrogen (N-6), pyrrole nitrogen (N-5), quaternary nitrogen (N-Q), and nitrogen oxide (N-X). While in the coal ash, the sub-peaks of N-Q and N-X disappear entirely, leaving only N-5 and N-6 sub-peaks. The released nitrogen-containing gas consists of NH₃, HCN, NO, and NO₂ during experiments in CO₂ and air atmospheres. However, only NH₃ and HCN are detected during experiments in the Ar atmosphere. The revolution characteristics of NH₃ and HCN under Ar and CO₂ atmospheres are similar.     

Porous silicon surface stability: a comparative study of thermal oxidation techniques

In this report, a systematic study is carried out to check the superiority of the oxidation techniques employed for improving the surface stability of Porous Silicon (PS). PS samples were oxidized in three different atmospheres viz. ambient air, oxygen gas and the mixture of oxygen and nitrogen gas. Among them, samples oxidized under O₂ atmosphere proves to be the best yielding excellent stable surface and no degradation observed even after one year. The qualitative analysis of the surface morphology, surface bond termination, and degradation, if any, of the oxidized PS samples were done by scanning electron microscope, micro-Raman, Photoluminescence and Fourier Transform Infrared spectroscopy. Electrical capacitive technique is used to check the ageing effect of the sensor device made from thermally oxidized PS. Ethanol vapor sensing was periodically made in the range of 25–100 ppm for one year, and any noticeable degradation is not observed in its sensing performance.     

XPS and ESR studies of the photodegradation of polyamidoimide and polyimide in O2, O2 + N2, air,N2, and vacuum atmospheres

The photostability of polyamidoimide (PAI) and polyimide (PI) films has been studied. UV irradiation caused a great change in the composition and structure of the film surface. With irradiation in atmospheres such as air, oxygen, and an oxygen—nitrogen mixture, the Cls spectrum had a distinct structure at high binding energy, and the O/C and N/C ratios were considerably increased. On the other hand, in nitrogen and under vacuum, the O/C and N/C ratios remained almost unchanged during an earlier stage of irradiation, but in the latter stage for the nitrogen atmosphere these ratios decreased to a broad minimum and then increased with an increase of irradiation time. UV irradiation also produced free radicals in the polymer films; PAI gave a much stronger ESR signal intensity than PI. The signal intensity vs. irradiation time curve was strongly influenced by irradiation atmospheres. In atmospheres containing oxygen the curve exhibited a broad maximum during an initial stage of irradiation, while under vacuum and in nitrogen the signal intensity increased greatly in the latter stage. The formation of free radicals during an earlier stage of irradiation in atmospheres containing oxygen was promoted by the oxygen incorporated at the film surface, while the radical production under vacuum was considered to be due to rupturing of bonds in the bulk material. The decay of free radicals in the dark after irradiation occurred at a faster speed in oxygen atmospheres than under vacuum.     

OXIDATION-REDUCTION EQUILIBRIA IN GLASS BETWEEN IRON AND SELENIUM IN SEVERAL FURNACE ATMOSPHERES*

This study has been limited to the reactions between iron and selenium in soda-lime and potash-soda-lime glasses melted in atmospheres of air, nitrogen, and carbon monoxide. Glasses containing selenium and iron, together and singly, were melted in the several atmospheres. and their spectral absorption curves between 350 and 1000 mμ were obtained. An analysis of these curves shows that under neutral or slightly oxidizing conditions selenites react with ferrous iron as follows: This reaction leads to an increase in red and brown and a decrease in blue colors. The decolorizing action of selenium may be explained by this reaction because the colorless selenite ion oxidizes the more colored ferrous ion to the less colored ferric ion, arid the increase in the red elemental selenium color physically compensates as a complimentary color for the remaining unoxidized ferrous ion. The results show that it is not necessary to postulate the formation of ferrous selenium to explain the color changes. The results also show that under reducing conditions the principal reaction is      

New epoxy resins. III. Application of fourier transform IR to degradation and interaction studies of epoxy resins and their copolymers

In the Fourier transform infrared (FT–IR) study, diglycidyl ether of bisphenol A (DGEBA) did not show aldehyde or perester absorption when it was normally cured with trimethoxyboroxine (TMB) under a nitrogen atmosphere. Neither alumina nor gold surfaces would cause oxidation of the system. In air, alumina appeared to accelerate the oxidation when compared to gold. The cure of the epoxy in oxygen appeared to cause increased Claisen rearrangement when compared with the same cure in a nitrogen atmosphere. The DGEBA cured with TMB under air or nitrogen atmospheres showed differences in their degradation patterns. The TMB-cured DGEBA and diglycidyl ether of 9,9-bis(4-hydroxyphenyl) fluorene (DGEBF) copolymer had a higher degree of reaction and lower degradation than was shown by the synthetically generated spectra based on the FT–IR summation of the spectra of the respective homopolymers.     

Surface activity of the lipid products hydrolyzed with lipase and phospholipase A-2

We examined thein vitro surface activity, immersional wettability and adhesional wettability shown by aqueous solutions of soy lysophospholipid (SLP)/monoglyceride (MG)/fatty acid (FA), SLP/FA and SLP/MG, and found that many lipid mixtures showed significant surface activity when their MG and FA components consisted of polyunsaturated FA and/or medium chain FA. The more unsaturated the FA, the higher the surface activity. A mixture of SLP/medium chain fatty acid MG (medium chain MG)/medium chain FA showed the highest surface activity, and was comparable to an Aerosol-OT surfactant, the most effective wetting agent. SLP/polyunsaturated FA monoglyceride (polyunsaturated MG)/polyunsaturated FA, SLP/medium chain FA, and SLP/polyunsaturated FA, SLP/medium chain MG, and SLP/polyunsaturated MG also showed a high degree of activity. Wettability decreased rapidly when the amount of saturated, long chain FA moieties increased. It is recognized that the degrees of unsaturation and the chain length of FAs in the lipid mixtures have a decisive influence on surface activities. Higher ratios of MG and FA to SLP gave higher activity; and solubilizers such as bile salts were necessary to dissolve them in water.     

Kinetic study of the thermal degradation of poly(aryl ether ketone)s containing 2,7‐naphthalene moieties

The degradation of poly(aryl ether ketone) containing 2,7‐naphthalene moieties was subjected to dynamic and isothermal thermogravimetry in nitrogen and air. The dynamic experiments showed that the initial degradation temperature, temperature for 5% weight loss, and temperature corresponding to the maximum degradation rate of poly(aryl ether ketone) containing 2,7‐naphthalene moieties were a little higher than those of poly(ether ether ketone) and almost independent of the 2,7‐naphthalene moiety content. The thermal stability of poly(aryl ether ketone) containing 2,7‐naphthalene moieties in air was substantially less than that in nitrogen, and the degradation mechanism was more complex. The results obtained under the isothermal conditions were in agreement with the corresponding results obtained in nitrogen and air under the dynamic conditions. In the dynamic experiments, the apparent activation energies for the degradation processes were 240 and 218 kJ/mol in nitrogen and air for the second reaction stage as the heating rate was higher than 5°C/min. In the isothermal experiments, the apparent activation energies for the degradation processes were 222 and 190 kJ/mol in nitrogen and air, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Behavior of mercury release during thermal decomposition of coals

The mercury release behavior during thermal decomposition of three Chinese coals with different types was studied under nitrogen, carbon dioxide and air at temperatures of 800, 900, 1,000 and 1,100 °C. The thermal treatment experiments were carried out in a quartz tube reactor. Results showed that the release ratio of total mercury during thermal decomposition of coals increases with the increasing temperature. The order of the amount of mercury released under the three atmospheres is nitrogen<carbon dioxide<air for all three coals during thermal decomposition. This indicates that air and carbon dioxide can promote the mercury release due to their reactivity with coal. However, the order of amount of elemental mercury released under the three atmospheres is nitrogen>carbon dioxide>air for all three coals. The release behavior of the total mercury under air is independent of the coal type. Under the other two atmospheres the release behavior is distinguished by the coal type. This work was presented at the 7 ^th China-Korea Workshop on Clean Energy Technology held at Taiyuan, Shanxi, China, June 26–28, 2008.     

阻燃剂聚丙烯酸五溴苄基酯的热分解动力学

用热分析法研究了阻燃剂聚丙烯酸五溴苄基酯在空气和氮气气氛中的热分解动力学。该阻燃剂在空气气氛中为两步分解,在氮气气氛中为一步分解,利用Friedman法求出聚丙烯五溴苄基酯的第一步分解反应的活化能变化趋势,同时利用Satava-Sestak法研究了其热分解机理。结果表明,在0.10至0.90的转化率范围内,聚丙烯酸五溴苄基酯在空气气氛下的活化能为167.35kJ/mol,在氮气气氛下的活化能为171.94kJ/mol,热分解机理均为Avrami-Erofeev方程,随机成核和随后生长,反应级数分别为n=23和n=12。动力学方程分别为G(a)=[-ln(1-a)]23和G(a)=[-ln(1-a)]12。     

Sintering in Nitrogen Atmosphere of Iron-Rich Glass-Ceramics

The sintering and the crystallization of two iron-rich glass compositions (45–75-μm powder fractions) were studied in air and nitrogen atmospheres. The phase formation was evaluated by differential thermal analysis, while the densification, by dilatometry; the crystalline phases were identified by X-ray diffraction and the structure observed by scanning electron microscopy. It was highlighted that, due to the absence of Fe²⁺ oxidation and lower viscosity of the parent and residual glasses, the sintering in nitrogen atmospheres occurs at 100°–200°C lower temperature. In the same time the higher amount of crystal phase, formed during sinter–crystallization in inert atmosphere, improves the mechanical properties. A value of 120 MPa for the bending strength was obtained after 1-h sintering at 960°C in N₂.     

The antioxidant effect of natural substances on lipids during irradiation of chicken legs

Entire fresh chicken legs were subjected to three pretreatments (packaged in air; packaged under vacuum; or marinated in natural plant extracts and packaged in air) followed by irradiation (0, 3, or 5 kGy). The control and irradiated chicken legs were stored at 4°C and analyzed for FA composition and sensory quality at predetermined intervals. Irradiation dose had a significant (P<-0.01) effect on FA derived from phospholipid but less than on FA derived from a neutral lipid. In general, levels of unsaturated FA decreased as the radiation dose increased; however, for marinated chicken legs irradiated with 5 kGy, levels of linoleic acid (C_18∶2) and arachidonic acid (C_20∶4) derived from the phospholipid fraction were significanlty (P≤0.05) higher than those irradiated in air or under vacuum. The concentration of FA also decreased significantly (P≤0.05) as storage time increased. For chicken legs packaged in air or marinated and then packaged in air, significant (P≤0.01) inverse correlations existed between high-carbon-number PUFA and lower-carbon-number (≤17) saturated FA; this relationship was not apparent in samples irradiated under vacuum. A processing combination of marinating and vacuum packaging might better control lipid oxidation and degradation in irradiated chicken. Panelists found no significant difference (P>0.05) in the flavor and oder intensity of cooked irradiated chicken legs and their nonirradiated equivalents.     

Crack Healing by Thermal Treatment in Float Glass: The Effect of Tin

The evolution of radial cracks generated by Vickers indentation on “tin side” of float glass is analyzed when heat treated at 620°C under various atmospheres and results are compared with a previous similar study performed on the “air side” of the same glass. Results evidence that the presence and the oxidation state of tin ions has a strong influence on crack morphological changes. If the oxidation state of tin remains quasi unchanged during the heat treatment, the mechanism responsible of the crack evolution is the spheroidization and there is no strong difference between the crack morphological changes observed on the “air” and “tin side” in this case. For oxidative atmospheres, contrary to what is observed on the “air side”, no crack spheroidization occurs. The cracks stay quasi unchanged for dry air or close for humid air. Increase of the viscosity at the top surface due to Sn oxidation is proposed to explain this spheroidization impediment. It is also shown that in these two cases, there is an efficient blunting and healing of the cracks, as 4‐point bending tests indicate a significant sample strengthening with thermal treatment.     

Stability and Oxidizing Effect of Membraneless Electrolyzed Water

Membraneless electrolyzed water (MLEW) is generated by electrolysis of dilute salt water solution without a membrane separating cathodic and anodic water. The stability of MLEW under different storage temperatures and pHs, as well as its lipid oxidizing effects have not been extensively studied. In this study, three storage temperatures and two pH conditions were used to study the stability of the water. MLEW's lipid degradation potential was investigated using two methods by measuring the degree of oxidation of lipids containing polyunsaturated fatty acids. Lipid oxidation in an emulsion model free of other interferences was conducted with MLEW containing 30, 50 and 100 mg L^?1 free chlorine (FC), and lipid oxidation in a salmon fish fillet was conducted by washing the fillet pieces with MLEW containing 100 mg L^?1 FC. We found that the MLEW was relatively stable in capped containers under both acidic and neutral pH during the 21‐day period. Although there was significant lipid oxidation in the emulsion system, and the extent of oxidation was FC concentration dependent, we did not observe significantly more lipid oxidation in fish treated with MLEW compared to the control (stored under 4 °C for 10 days). Therefore, we conclude that MLEW may be used as a disinfectant in commercial operations without causing significant lipid oxidation and rancidity generation in foods.