J. C. Cowan

Polyamides from polymeric fat acids

SummaryThe preparation and properties of various polyamides, copolyamides, and modified polyamides, of polymeric fat acids have been described. These polymers are of interest because of their unusual properties and because of the unsaturation and relatively high molecular weight of the polybasic acids involved. Despite the presence of tribasic acids in polymeric fat acids, ungelled polymers having molecular weights of 3,000 to 5,000 are obtainable. A brief discussion has been given concerning the application of theoretical principles of polymerization to the preparation of these polymers. Possible industrial uses for the polyamides are indicated.

Oxidation and quality of soybean oil: a preliminary study of the anisidine test

The anisidine test, a measure of secondary oxidation products in glyceride oils, was applied to a number of soybean salad oils processed from sound and damaged soybeans. A highly significant correlation (−0.68) was found between the anisidine values of salad oils from sound soybeans and their flavor scores. Multiple correlations between flavor scores, anisidine, and peroxide values yielded a correlation of 0.81 and provided a method for predicting the initial flavor scores of sound soybean salad oils. Similar data for oils from damaged beans gave a highly significant, but lower, correlation (−0.65). Comparative studies indicated that sound crude oils usually contain lower levels of oxidation products than damaged crude. Oxidation in both sound and damaged crudes increased roughly in proportion to iron content. Reproducibility of the test and the effects of hydrogenation, accelerated storage, and fluorescent light on anisidine values were studied. Analysis of damaged oils before and after deodorization showed that little, if any, reduction of anisidine value occurred. Deodorization of sound oils, however, lowered anisidine values. In comparison with damaged oils, the anisidine values of sound oils were lower at comparable stages of processing. The poor quality of damaged soybean oil was substantiated by organoleptic evaluations. Flavor scores of oils given special processing treatments increased as anisidine values decreased.

Analyses of lipids and oxidation products by partition chromatography. Dimeric and polymeric products

A liquid-partition chromatographic method was developed to determine dimers in fats. Silicie acid treated with 20% methanol in benzene served as the immobile phase. A mixture of 2% methanol in benzene was the mobile solvent. Chromatographic separation of free fatty acids from oxidized-deodorized oils gave three well-isolated fractions composed of unoxidized acids, dimeric or polymeric fatty acids, and polar fraction (ethyl ether eluate). Recovery of acidic materials from the column was essentially quantitative (96–100%), reproducibility was good, and the standard error of regression was ±0.26.A linear relationship exists between the dimer content of deodorized soybean oil and the peroxide value of the oil before deodorization. An increase of 1% in dimer concentration corresponds to an increase in peroxide value of approximately 40. Dimer content of different vegetable oils varied from 1 to 3%.The chromatographic method can be used to estimate the degree of oxidation that an oil has received before deodorization and to follow various phases of fat oxidation, polymerization, and processing.

The flavor problem of soybean oil. IV. Structure of compounds counteracting the effect of prooxidant metals

SummaryA study has been made of the effectiveness of various polycarboxylic acids and polyhydric alcohols in improving the stability of soybean oil. Certain observations have been made regarding the structural groups required and the possible mechanism of reaction. Since salts and esters of organic acids are inactive, free carboxyl groups are required. Among the four carbon atom dicarboxylic acids activity increases with the number of hydroxyl groups. Within the polyalcohols activity increases with the increase in number of hydroxyl groups. Steric immobility and loss of hydroxyl groups by dehydration reduces activity. Evidence is presented which attributes to citric acid and certain polyhydric alcohols the role of metal scavenger. For example, it has been demonstrated that the addition of citric acid and sorbitol to soybean oil containing prooxidant metallic salts effectively increases the oxidative and flavor stability of the oil. By using a sample of treated soybean oil with no detectable tocopherols, in order to eliminate synergistic effects of citric acid, it has been shown that the prooxidant effect of iron stearate is counteracted by the presence of citric acid. The demonstration that polyhydric alcohols increase the flavor and oxidative stability is compatible with their known metal complexing properties. Evidence is presented which indicates a relationship between flavor stability and oxidative stability.

Long term storage of soybean and cottonseed salad oils

Commercially prepared and packaged soybean and cottonseed salad oils from several different processors were evaluated periodically during storage for 12 months. Partially hydrogenated and winterized soybean oils, as well as unhydrogenated soybean salad oils, were stored in bottles and cans at 78 and 100 F. Control samples of all oils were held at 0 F during the entire test. Some lots in bottles and cans were packaged under nitrogen to improve storage stability. Agreement was good between organoleptic and oxidative evaluation of aged oils. After 26 weeks of storage at 100 F, the flavor of partially hydrogenated-winterized oils packaged under nitrogen showed a minimum loss. These same oils did not exhibit much, if any, reduction in their oxidative stability as indicated by storage peroxide values (active oxygen method). Soybean oil not protected with nitrogen demonstrated progressive flavor deterioration at 100 F. After 10 weeks of storage, the deterioration became marked and the flavor score was below 5. From limited observations, bottled oils appear to have a better stability than oils packaged in screw-cap tin cans. Hydrogenated oils packaged under nitrogen in cans had good oxidative stability, but some lowering of the flavor score was observed. Nonhydrogenated soybean oils packaged in tin cans not under nitrogen exhibited the most rapid flavor deterioration of all lots of oil investigated.

A LIGHT TEST TO MEASURE STABILITY OF EDIBLE OILS.

The effect of light on the flavor of edible oils and of various fat-containing foods is reviewed to show its importance in food studies and the need for a method of evaluation. Such a test, in which fluorescent light is used in an easily assembled unit, has been developed, and the parameters for its use have been determined. Identical samples of soybean oil exposed on 10 different days and organoleptically evaluated show the method to be reproducible with a standard deviation of 0.79 with a scoring system of 1–10. This method was then applied to soybean, cottonseed, safflower and hydrogenated-winterized soybean oils, and a light-exposure value was determined for each oil based on a comparison with accelerated storage procedures ordinarily used. Advantages of this light test over current procedures are the short time required for completion, the reduction of variation by a controlled light source, reproducibility of results and its adaptability to related food products.

Reactions of carbon monoxide with unsaturated fatty acids and derivatives: A review

The important reactions of carbon monoxide with unsaturated fatty derivatives that are reviewed in this paper include hydroformylation (the oxo reaction), Koch carboxylation and Reppe carbonylation. With oleic acid as a substrate, the products are C19 bifunctional compounds e.g., formyl- or carboxy-stearic acid. Double bond isomerization before carbon monoxide addition is characteristic of these catalytic reactions; additionally, rearrangement to introduce methyl branching occurs in the Koch carboxylation. Isomerization does not occur when a rhodium-triphenylphosphine catalyst replaces cobalt in the oxo reaction. Properties of the C19 dicarboxylic acids differ and depend upon method of preparation: Many areas of application have been reported for C19 compounds-lubricants, plasticizers, polyurethanes, epoxy resins, leather and other coatings, unsaturated polyester resins and transparent polyamide plastics.

Thermal dimerization of fatty ester hypdroperoxides

SummaryWhen autoxidized fatty esters and purified fatty hydroperoxides were decomposed in the absence of oxygen at 210°C., the principal reaction was dimerization of the fatty acid chains with elimination of the hydroperoxide groups. Dimers isolated by molecular distillation (60 to 90% of the polymer) have approximately 1 mole hydroxyl, 0.5 mole carbonyl, and two double bonds per mole of dimer. Diene conjugation in the dimers from polyunsaturated fat hydroperoxides varied from 10 to 23%. The infrared spectra of the dimers were similar to those of the original fatty esters except for one striking band at 2.9 μ, which is attributed to the secondary hydroxyl group. Thecis-trans diene in the polyunsaturated hydroperoxides was isomerized to thetrans-trans configuration on dimerization. The methyl oleate hydroperoxide dimer showed only absorption for isolatedtrans double bond. The dimer was not split either by catalytic hydrogenation or by hydrogen iodide, indicating a carbon-carbon bond between the monomer units. On oxidation with permanganate and periodate, the dimeric acids behaved like a monounsaturated mixture containing double bonds in the C6, C7, C8, C9, and C10 positions in the oleate dimer and in the C8, C9, and C10 positions in the safflower ester dimer. Although the dimers showed no peroxidic oxygen iodometrically with potassium iodide, a reduction occurred with hydriodic acid that may indicate the presence of intramolecular peroxide groups and/or allylic alcohol or carbonyl groups. Bromination with N-bromosuc-cinimide and dehydrobromination with N,N-dimethyl aniline produced no aromatization. Subsequent oxidation of the dehydrobrominated dimer yielded 2.6% residue, which was not aromatic. This evidence indicates that the dimer does not have a six-membered cyclic structure. Dimerization of the hydroperoxides is suggested as occurring through alkyl or alkoxy hydroperoxide radicals to give carbon-carbon linked fatty acid dimers and some higher polymeric units.

Polyester amides from linseed oil for protective coatings

The sodium alkoxide-catalyzed reaction of linseed oil or linseed methyl esters with diethanolamine produces almost exclusively linseed diethanolamides. Reaction conditions, e.g., temperature, amount of excess diethanolamine and mode of adding reactants, are reported. The best conditions for producing diethanolamide directly from linseed oil (1 mole) required adding oil to the sodium alkoxide in diethanolamine (6 moles) and heating at 110–115C for 35 min. The linseed diethanolamide isolated in 93–95% yield was an amber oil. Progress of the reaction, followed by thin-layer chromatography, showed only trace amounts of byproducts.Polyester amides were prepared by heating linseed diethanolamide in refluxing xylene with dibasic acids or anhydrides, e.g., azelaic, maleic, fumaric, phthalic, terephthalic, itaconic, brassylic and dimer acids. Molecular weight, viscosity and film properties (air-dried and baked) of the polyester amides were determined.

Ozonization of soybean oil. The preparation and some properties of aldehyde oils

A polyaldehydie product called aldehyde oil was prepared by the ozonization of soybean oil, followed by reductive decomposition of the ozonolysis products. Reductive decomposition by chemical means gave 85–90% yields of carbonyl in the aldehyde oil. Catalytic reduction gave 75–80% yields. Partially-hydrogenated soybean oil gave more efficient results than did unhydrogenated oil. The polyfunctional aldehyde oil was found to undergo condensation reactions with phenolic compounds, urea, amines, and polyols to give cross-linked polymers.