A comparative study on the susceptibilities of soybean,sunflower and peanut oils to singlet molecular oxygen photooxidation

The susceptibilities of crude soybean, sunflower and peanut oils to singlet oxygen photooxidation were determined in a kinetic study. The accumulation of photosensitized hydroperoxides, determined spectroscopically, and the quenching of singlet molecular oxygen phosphorescence by the crude oils and their fatty acid methyl esters were compared. The relative tendency to photooxidation for the oils and the methyl esters was soybean ≫ sunflower > peanut. This trend was independent of the method employed in the determination of initial photodamaging. Soybean oil was demonstrated to be the most unstable product, not only due to the presence of highly unsaturated fatty acids, but also due to the absence of natural constituents, capable of providing a protective antioxidant effect. This protection was more effective in sunflower and peanut oils.     

The effects of oxygen diffusion on the surface photooxidation of polystyrene

This paper further illustrates the applicability of multiple internal reflectance infrared spectroscopy to the analysis of near-surface photooxidation. The results are compared with transmission infrared spectra to evaluate compositional gradients resulting from photooxidation and the influence of oxygen diffusion. The sample was a solvent-cast film of atactic, narrow distribution polystyrene, M_w of 100,000, that had been drawn to a ratio of 3.0 at 110°C by solid state coextrusion. Irradiation of these thin films, ～25μm thickness, was performed on exposure to air at 35°C for periods of up to 6 h using a mercury source emitting at 254 nm. On photooxidation, a board peak appears at 3200–3500 cm^?1, attributable to hydroperoxide formation. The most dramatic increase in the infrared spectra is found for a carbonyl band at 1730 cm^?1. It appears to result from an aromatic acid group since it is shifted to 1660 cm^?1 on immersion of the oxidized polystyrene films in aqueous ammonium hydroxide. It is confirmed that the photooxidation of polystyrene occurs preferentially at the surface and that this reaction rate is greatly reduced in the drawn polystyrene film.     

Mechanisms of antioxidant action: The effect of spin traps during the processing and photooxidation of PVC

It is demonstrated by the use of spin traps that during the early stages of thermal processing of PVC considerable concentrations (> 3 × 10^?6 mol g^?1) of free radicals are produced which are primarily responsible for the initial products (hydroperoxides, unsaturation, and hydrogen chloride) previously shown to be formed in the polymer. From a semiquantitative analysis of these products, it is estimated that more than 50% of the radicals are formed from hydroperoxides and the rest by mechanoscission of the polymer chain. The spin traps are effective processing stabilizers in combination with a tin maleate HC1 scavenger. One of them (2-methyl-2-nitroso propane, MNP) has also been shown to be a photoantioxidant.     

Some monomethyl-branched fatty acids from ruminant fats: Open-tubular GLC separations and indications of substitution on even-numbered carbon

Isomeric methyl esters of fatty acids in three groups (C₁₅, C₁₇, C₁₉) have been isolated from ruminant fats. Basic structural analysis by physiochemical techniques indicated that these odd-numbered fatty acids were even chain with a single methyl branch on the chain. High resolution open-tubular gas liquid chromatographic studies indicate that, with the exception of iso acid impurities in these fractions, only even-numbered carbons of the fatty acid chains bear the methyl branch.     

Antioxidants and stabilizers. LXV. Contribution to the investigation of sensitized photooxidation of phenolic antioxidants. Quenching of singlet oxygen with stilbenequinoid compounds

The photooxidation of 2,6-di-tert-butyl-4-methylphenol (I) and 2,2′-methylene-bis(4-methyl-6-tert-butylphenol) (II) sensitized with methylene blue in dichloromethane was investigated. The oxidation of phenol I proceeds at a reduced rate, but otherwise similar to the oxidation in methanol, that is, with the formation of 2,6-di-tert-butyl-4-methyl-4-hydroperoxy-2,5-cyclohexadiene-1-one (III, R = tert-butyl). On the other hand, bisphenol II remains almost unoxidized in dichloromethane. This is due to the formation of stilbenequinoid derivatives of type VI which slow down the oxidation even at insignificant concentrations. The effect approaches that of β-carotene. Phenol I has a much weaker tendency towards the formation of an analogous derivatives, i.e. 3,5,3′,5′-tetra-tert-butylstil-benequinone (VIII), which however is also an active retarder of oxidation. A more detailed study carried out with VIII indicates that the mechanism of its effect is the same as for β-carotene, that is, the quenching of singlet oxygen. Stilbenequinone VIII used in a fourfold concentration has almost the same effect as β-carotene, but unlike the latter it is much more stable towards oxidation. The activity of VI lies between that of stilbenequinone VIII and β-carotene.     

Effect of diffusional resistances on the action pattern of immobilized alpha-amylase

Alpha-amylase from Aspergillus oryzae has been immobilized onto corn grits and porous silica (specific areas 180 and 440 m² g^?1). Kinetic parameters of immobilized enzyme have been determined. Immobilization of alpha-amylase results in the formation of less polymerized products resulting in an apparent decrease in the number of transglycosylation reactions, for both maltotetraose and starch as substrates, when compared with free enzyme. Diffusional limitations for substrate and products have been quantified in the case of the three supports used. External diffusional resistances were important in all cases for the reaction products, whilst they became negligible for the substrate in the case of silica supports. Moreover, internal transfer limitations were identified with silica 180 m²g^?1 support. It was demonstrated that diffusional resistances were in direct relation to the apparent modification of the enzyme action pattern after immobilization.     

Intramolecular effects on the fundamental hydroxyl stretching vibration in derivatives of fats and related compounds

The intramolecular environment of the hydroxyl group in several compounds related to fats has been investigated by infrared measurements of the fundamental stretching vibration, using a lithium fluoride double monochromator and sufficiently low concentrations (.001–.05 M) in carbon tetrachloride to avoid intermolecular effects. In saturated alcohols and saturated hydroxyl derivatives of esters, the OH stretching frequency is found to depend on the number of hydrogen and carbon atoms which form the immediate environment of the OH group. Since this varies with rotational isomerism about the C-O single bond, the infrared hydroxyl band is composite, made up of components whose strengths give information about the relative amount of each rotational isomer present. In unsaturated alcohols and unsaturated hydroxy-esters, rotational isomers permitting hydrogen bonding to π-electrons are stabilized according to the accessibility of the unsaturated link to the hydroxyl group, thus altering the proportions of the rotational isomers. Presented at the AOCS meeting in Toronto, Canada, 1962. Eastern Utiliz. Res. & Dev. Div., ARS, U.S.D.A.     

Polyanhydrides: the effects of ring substitution changes on polymer properties

Summary We synthesized polymers that overcome the processing problems associated with aromatic polyanhydrides. In this paper, we focus on the synthesis and characterization of ortho-substituted polyanhydrides, poly[1,3-bis(o-carboxyphenoxy)propane anhydride] (o-CPP) and poly[1,6-bis(o-carboxyphenoxy)hexane anhydride] (p-CPH). By lengthening the alkyl chain between aryl groups (from propane to hexane) and changing the ring substitution pattern from para- to ortho-, we observed enhanced solubility of aromatic polyanhydrides. Ultimately, these polyanhydrides may be useful as polymer scaffolds for use as functional soft tissue substitutes. Received: 29 July 1998/Revised version: 3 November 1998/Accepted: 6 November 1998     

Antioxidants and the autoxidation of fats IV. Lecithin as an antioxidant

The commercial preparations known as “lecithin” have moderate antixoygenic action on refined cottonseed oil, little effect on lard, and none at all on lard-cod liver oil mixtures. Commercial lecithins contain only small amounts of true lecithin. The antioxygenic agent in these preparations is cephalin. Purified lecithin is not an oxidation inhibitor, but purified cephalin is. There is no quantitative relation between the amount of cephalin used and the prolongation of the induction period. The particular portion of the cephalin molecule responsible for its antioxygenic action is probably the mono-basic phosphoric acid radicle.     

Quantitative effects of dietary polyunsaturated fats on the composition of fatty acids in rat tissues

A method combining data on fatty acid composition into subsets is used to illustrate general relative competitive selectivities in the metabolic and transport events that maintain fatty acid compositions in tissue lipids and to minimize differences among tissues or species in the amount of individual fatty acids. Fatty acid compositions of triglycerides and phospholipids in several tissues of the rat were maintained with simple relationships between the exogenous n−3 and n−6 dietary polyunsaturated fatty acids and the endogenous n−7 and n−9 types of fatty acid. The general pattern of fatty acids in triglycerides was similar for liver, plasma and adipose tissue, averaging about 30% as saturated acids, 67% as 16- and 18-carbon unsaturated acids and only about 2% as 20- and 22-carbon highly unsaturated acids. The tissues maintained a linear relationship between the amount of 18-carbon polyunsaturated fatty acids in the diet and in the tissue triglycerides, with the proportionality constant for 18∶3n−3 being 60% of that for 18∶2n−6. The total phospholipids of liver, plasma and red blood cells maintained about 45% of the fatty acids in the form of saturated fatty acids and 20–30% as 20- and 22-carbon highly unsaturated fatty acids irrespective of very different proportions of n−3, n−6 and n−9 types of fatty acids. In all three tissues, the 20-carbon highly unsaturated fatty acids of the n−3, n−6 and n−9 type were maintained in a competitive hyperbolic relationship with apparent EC₅₀ values for dietary 18∶2n−6 and 18∶3n−3 near 0.1% of dietary calories. The consistent quantitative relationships described in this study illustrate an underlying principle of competition among fatty acids for a limited number of esterification sites. This approach may be useful in predicting the influence of diet upon tissue levels of the substrates and antagonists of eicosanoid biosynthesis.     

Improvement of the light fastness of natural dyes: the action of singlet oxygen quenchers on the photofading of red carthamin

While the contribution of singlet oxygen quenchers to synthetic dyes has been investigated previously by several workers, there have been few studies pertaining to the use of singlet oxygen quenchers as a means of improving the light fastness of natural dyes. In this paper, the influence of various additives on the photofading of carthamin has been examined in cellulose acetate film. The rate of photofading of the colour was remarkably suppressed in the presence of nickel hydroxyarylsulphonates, while the addition of UV absorbers afforded little retardation in the rate of fading.     

Effect of degree of substitution and molecular weight of carboxymethyl chitosan nanoparticles on doxorubicin delivery

The aim of this study was to evaluate the potential of carboxymethyl chitosan (CM‐chitosan) nanoparticles as carriers for the anticancer drug, doxorubicin (DOX). Different kinds of CM‐chitosan with various molecular weight (MW) and degree of substitution (DS) were employed to prepare nanoparticles through ionical gelification with calcium ions. Factors affecting nanoparticles formation in relation to MW and DS of CM‐chitosan were discussed. By the way of dynamic light scattering (DLS), TEM, and atomic force microscopy (AFM), nanoparticles were shown to be around 200–300 nm and in a narrow distribution. FTIR revealed strong electrostatic interactions between carboxyl groups of CM‐chitosan and calcium ions. DOX delivery was affected by the molecular structure of CM‐chitosan. Increasing MWs of CM‐chitosan from 4.50 to 38.9 kDa, DOX entrapment efficiency was enhanced from 10 to 40% and higher DS slightly improved the load of DOX. In vitro release studies showed an initial burst followed by an extended slow release. The DOX release rate was hindered by CM‐chitosan with high MW and DS. These preliminary studies showed the feasibility of CM‐chitosan nanoparticles to entrap DOX and the potential to deliver it as controlled release nanoparticles. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4689–4696, 2006     

The kinship or k-index as an antidote against the toxic effects of h-indices

In a bilingual paper entitled 'Bibliometrics as weapons of mass citation--La bibliométrie comme arme de citation massive', recently translated into English, we have argued that the current fashion of ranking people, papers and journals is anything but harmless. The point was forcefully supported by Richard Ernst in a post-face entitled 'The Follies of Citation Indices and Academic Ranking Lists. We received a surprising number of passionate responses, such as 'It's written out of my heart' (TH); 'Je soutiens cette entreprise courageuse de tout coeur' (VT); 'Impact Faktoren sind ein Marktinstrument gewisser Verlage (FS); 'II y a un combat à mener' (SB). Some thoughtful responses have been incorporated into this Essay, albeit in attenuated form. We suggest that the 'fertility' of individual scientists be appreciated in terms of kinship rather than through personalized indices.     

The effect of photooxidation aging on the cohesion and interfacial adhesion behavior of epoxy asphalt with a composite acidic curing system based on molecular simulation

This paper investigated the cross-linking network structure of epoxy asphalt (EA) with the different ratio of composite curing agents, and further determined the effect of photooxidation aging on the tensile and interfacial adhesion behavior of EA with different cross-linking network structures through molecular simulation. Based on the molecular models of EA and the interface model between EA and aggregate, the crosslinking network structural characteristics and tensile mechanical behavior were determined. The interfacial adhesion behavior and the mechanization were further studied. The results indicate that 20-EA and 6-EA have an epoxy resin cross-linked network with uniform pore structure and phase distribution. 2-EA showed a denser cross-linking network and uneven aggregation phenomenon. Photooxidative aging alleviated the aggregation phenomenon. A dense cross-linking network improved the tensile strength and the ability of tensile performance to resist photooxidation aging. The interface of EA-quartz exhibited higher adhesion strength than EA-calcite due to the closer distance and stronger nonbonding interactions between EA and quartz. The low anhydride content and photooxidation aging made EA approach to the aggregate interface, increasing nonbonding interaction and interfacial adhesion strength. In addition, quartz aggregates were more suitable for application in EA mixtures due to the higher interfacial adhesion strength and lower water sensitivity.     

Heated fats. I. Studies of the effects of heating on the chemical nature of cottonseed oil

When cottonseed oil was heated at 225°C. in the presence of air for long periods of time, nonurea adduct-forming monomers and dimers were formed which were toxic to rats. Analyses showed that the toxic fractions contained moderate amounts of carbonyl and hydroxyl and that they contained unsaturation difficult to remove by hydrogenation. Cyclic structures appeared to be present in the dimer fraction. The production of nonurea adducting monomers and dimers is associated with polymerization and other reactions of linoleic acid. Presented at 52nd annual meeting, American Oil Chemists' Society, Dallas, Tex., April 4–6, 1960.     

Hydrolysis effects on the molecular weight degradation of condensation polymers as estimated from their prior drying condition

A simple model has been developed to evaluate the potential random degradation of hydrolyzable polymers as a function of water remaining after drying but prior to processing. Molecular weight retention was found to be dependent on the initial molecular weight of the polymer as well as the hydrolysis efficiency, but independent of polymer crystallinity. At the same water content and hydrolysis efficiency, the model indicated that higher molecular weight polymers would be expected to yield a more significant molecular weight reduction. The potential degradation of hydrolyzable condensation polymers was also estimated from drying conditions recommended by producer companies. The results calculated from the hydrolysis model were in most instances consistent with producer company recommended drying conditions. A review of the literature also found that while the sensitivity of nylons to hydrolysis decreases with moisture content, nylon 6/6 specifically can sometimes increase in brittleness and viscosity to an unacceptable level after drying below a critical moisture content. Thus nylon 6/6 was found to have a preferred range of moisture content for optimum processing. The need for a test method to evaluate hydrolysis efficiency for hydrolyzable polymers was also discussed. Such a standard could be important in the practical evaluation of new materials developed to minimize hydrolysis susceptibility.     

Recent trends in usage of fats and oils as functional ingredients in the baking industry

Throughout the history of the human race, cereal grains have been a source of staple food throughout this Earth. Except for the rice-eating countries, bread is the principal food and provides more nutrients than any other single food source. In over half of the countries around the world, bread supplies more than 50% of the total caloric intake. Even in one of the wealthiest nations, the United States, cereal grain products supply over 25% of the food energy, ca. 20% of the proteins, 14-18% of fats, and over 40% of carbohydrates.