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Minor constituents in high quality tall oil fatty acids have been isolated successfully by liquid column chromatography, using silicic acid as the adsorbent. The minor constituents contained two types of compounds: those which were noneffective and those which were effective in causing the darkening of tall oil fatty acids during heating. The former consisted oftrans-3,5-dimethoxystilbene and rosin acids. The latter was separated into numerous fractions by the combination of chemical methods, silicic acid column chromatography, and low temperature fractional crystallization. The fractions were characterized by functional group analyses, chemical reactions, and UV and IR spectrometric methods. Most of the fractions contained two-three times as much oxygen in the molecule as the original sample and were highly oxidized fatty acids. They had mol wt ranging 300–551 and contained double bonds, carbonyl, ester, peroxide, and hydroxyl groups. The effect of these minor constituents upon the color stability of tall oil fatty acids during heating was postulated as being due to the hydroxyl groups located in the α-position to the double bond in the molecule.

The stability of a northern sunflower oil was evaluated against a corn oil. The sunflower oil was tested before and after winteriza-tion, as well as with and without the addition of methyl silicone and antioxidants. The corn oil was tested after winterization with and without the addition of methyl silicone and antioxidants. Under normal use conditions at room temperature and 35 C, in the pres-ence of air in the headspace gas, sunflower oil samples developed peroxides more rapidly than corn oil. However, these higher perox-ide numbers did not seem to affect their organoleptic scores. Starch chunks, deep-fat fried in corn oil, had better flavor stability than those fried in sunflower oil. The peroxide values of the corn-oil-fried starch chunks were consistently lower than the sunflower-oil-fried starch chunks at various stages of aging. The chemical and physical changes of the corn oil and sunflower oil samples during simulated deep-fat frying were compared. The stability of the corn oil was approximately the same as that of the sunflower oil.

Commercial oleic acid has a tendency to develop a dark color during heating. It has been found that this discoloration is partially due to oxidation and partially due to the presence of minor constituents. Their characterization as oxidized and polymerized fatty acids will be reported in a separate paper. The effects of the two factors are synergistic to each other and thus accentuate the darkening of the commercial oleic acid when it is heated under air. Removal of the minor constituents from commercial oleic acid by silicic acid treatment drastically improved its color stability. The generally acknowledged concept that the higher the polyunsaturated fatty acid content in the commercial oleic acid, the lower its color stability, is not correct. The color stability of commercial oleic acid is more predominantly dependent upon the content of minor constituents than that of polyunsaturated fatty acid.

Triolein was heated under simulated deep-fat frying conditions at 185 C for 74 hr. The thermally oxidized triolein was converted into methyl esters and then fractionated by urea exclusion. The urea adduct-forming ester (89.2%) was found to be methyl oleate unchanged by the frying treatment. The nonurea adduct-forming esters (10.8%) were further fractionated by silicic acid column chromatography into nine fractions with molecular weights ranging from 304 to 742. Physical and chemical analyses of the fractions indicated that some of them contained oxygen atoms which could not be accounted for by ordinary functional group analyses. The polymers isolated were formed by both carbon-to-carbon and carbon-to-oxygen linkages. The nonpolar dimers were further purified by thin layer and gas chromatography. Structure elucidation revealed that they consisted of a noncyclic dimer and a noncyclic dimer containing a carbonyl group, each of which amounted to 1.36% of the triolein originally used. The polar polymers were studied by depolymerization and the analysis of the depolymerized products. It was estimated that the triolein used for simulated deep fat frying contained 1.1% trimers formed through carbon-to-carbon linkages, 1.9% dimers and trimers joined through carbon-to-carbon linkages, and 3.1% dimers and trimers joined through carbon-to-oxygen or carbon-to-carbon linkages in the same molecule and also dimers and trimers in which all the monomeric units were joined through carbon-to-oxygen linkages. The precise form of the oxygen linkages are not known. However, the fact that it is not cleavaged by HC1 and HI suggests ether linkages.

Deep-fat frying is one of the most commonly used procedures for the preparation and manufacture of foods in the world. During deep-fat frying, oxidative and thermal decompositions may take place with the formation of volatile and nonvolatile decomposition products, some of which in excessive amounts are harmful to human health. A limited survey of frying fats used in commercial operations indicated that some were maintained at good quality and others were overused or abused. The volatile decomposition products produced by corn oil, hydrogenated cotton-seed oil, trilinolein, and triolein, under simulated commercial frying conditions, were collected, fractionated, and identified. A total of 211 compounds were identified. The nonvolatile decomposition products produced by trilinolein, triolein, and tristearin under simulated commercial frying conditions were collected and characterized. After being treated under deep-fat frying conditions at 185 C for 74 hr, trilinolein yielded 26.3% non-urea-adduct-forming esters, triolein yielded 10.8%, and tristearin also yielded 4.2%.

cis- andtrans-2-(2-Pentenyl)furans were synthesized and structures were confirmed by infrared, nuclear magnetic resonance and mass spectroscopy. Preliminary organoleptic evaluation of oil solutions of the compounds indicated that thecis isomer had a flavor threshold of ca. 0.25 ppm. with odor and flavor descriptions of beany, grassy and buttery at 0.50 ppm; and that thetrans isomer had a flavor threshold of ca. 0.50 ppm with odor and flavor descriptions of beany, grassy and buttery at 1 ppm and strong painty and metallic at 4 ppm. These compounds, if found in soybean oil through the autoxidation of linolenate, may contribute to the characteristic reversion flavor.

The volatile flavor compounds in a reverted soybean oil with a peroxide number of 6.0 meq/kg were isolated by semicontinuous countercurrent vacuum steam distillation. Based upon the gas Chromatographic retention times and mass spectra of the four synthesized 2-pentenylfurans, it was found that cis- and trans-2-(l-pentenyl)furans and a mixture of cis- and trans-2-(2-pentenyl)-furans are present in reverted soybean oil. At least the greater portion of 2-(2-pentenyl)furans identified was cis-isomer. These compounds may contribute to the reversion flavor of soybean oil.

A novel antioxidant compound has been isolated and identified from the leaves of theRosmarinus officinalis L. The compound, named rosmaridiphenol, is a diphenolic diterpene. When tested in lard, the antioxidant activity of this compound was superior to BHA. Structural elucidation of rosmaridiphenol was accomplished by infrared spectroscopy (IR), mass spectroscopy (MS),1H-NMR (nuclear magnetic resonance) and13C-NMR spectroscopy.

The acidic and nonacidic volatile decomposition products (VDP) produced by pure trilinolein maintained at 185 C with periodic injection of steam were collected, fractionated, and identified. One hundred thirty-three volatile compounds were positively or tentatively identified. The compounds identified included a number of new and interesting compounds, some with valuable organoleptic properties, such as the unsaturated lactones.

A natural antioxidant extract with activity greater than BHA and equal to BHT was isolated from rosemary leaves. The extract was separated into 7 primary fractions with liquid chromatography, using silicic acid as an adsorbent followed by gradient elution. Each fraction was rechromatographed to yield a total of 16 subfractions. Two compounds, carnosol and ursolic acid, were identified by infrared, mass and nuclear magnetic resonance spectrometry. Carnosol was shown to be one of the active antioxidant components in rosemary. Ursolic acid was not an effective antioxidant. Further fractionation of the most active antioxidant subfractions by high performance liquid chromatography and the elucidation of the chemical structures of these fractions are now in progress.

Five oils and a fat were subjected to simulated deep fat frying using moist cotton balls. The used oils were evaluated by an expert organoleptic panel. Statistically significant differences were found in the odors and flavors of the used oils. Volatile decomposition products of the used oils were quantitatively isolated by high vacuum cryogenic entrainment and then analyzed by gas-liquid chromatography. The volatiles from each used oil yielded a gas chromatogram which was qualitatively and quantitatively different from the others. A statistical analysis was used to correlate the organoleptic scores with the profile gas chromatograms from the used oils. Excellent correlations between gas chromatographic peak areas and organoleptic scores were established. However, limitations in the number of samples tested and limitations in the statistical design do not permit drawing conclusions of cause and effect.

A total of nine acidic and 83 basic compounds was identified in the roasted and unroasted cocoa butter samples. Forty seven of the compounds identified are being reported for the first time in cocoa. The higher concentration of short chain fatty acids in the unroasted cocoa butter is responsible for its acidic aroma characteristics. The roasted cocoa butter generally contained greater numbers and higher concentrations of compounds whose formations would be favored by thermal processing. These compounds included pyrazines, thiazoles, oxazoles and pyridines. The aromas of many of these compounds are characteristic of the aroma differences between the two cocoa butters and contribute to the cocoa aroma of roasted cocoa butter.

Minor constituents were isolated from a mixture of commercial oleic acid manufactured from beef tallow by 10 different companies. Silicic acid was used as an adsorbent to isolate the minor constituents. They were first separated into acidic and nonacidic fractions. Each fraction was then separated into numerous subfractions by stepwise gradient elution liquid chromatography, using silicic acid as the adsorbent. The subfractions which had an adverse effect on the color stability of oleic acid during heating were characterized with functional group analysis, elemental analysis and IR spectrophotometry. The minor constituents amounted to ca. 1.18% of the commercial oleic acid. They were complex mixtures with multiple functional groups. Some of the subfractions contained 2\s-3 times as much oxygen in the molecule as oleic acid. They had molecular weights ranging from 308 to 830 which are from monomers to trimers of oxidized oleic acid. These minor components contained carbonyl, ester and hydroxyl groups and double bonds. Some of the nonacidic minor constituents may contain amide groups. Most of the acidic subfractions were dark red, viscous liquids and the nonacidic subfractions were dark green or greenish-brown, semisolid substances. A relationship was established that the greater the polarity of the minor constituents, the greater is its adverse effect on the color stability of oleic acid during heating.

Volatile compounds were isolated from 150 lb of commercial oil-free soybean lecithin by vacuum distillation. The isolated volatile compounds were subjected to extensive gas chromatographic fractionation, and the pure fractions thus obtained were identified by mass spectrometry. A total of 79 compounds have been identified. Most of the compounds identified can be postulated as autoxidative decomposition products of unsaturated fatty acids of phospholipids. Isophorone, an acetone-derived compound, was shown to be predominantly responsible for the undesirable flavor of oil-free soybean lecithin. Several nitrogen-containing compounds, e.g., nitriles, acetoxime and 4,5-dimethylisoxazole, were identified as unique volatile compounds from phospholipids.

The acidic and nonacidic volatile decomposition products (VDP) pro-duced by pure triolein maintained at 185 C with periodic injection of steam were collected, fractionated and identified. A total of 93 compounds were positively or tentatively identified. A number of the compounds found were identified for the first time in fats or oil VDP. Among these newly identified compounds are: unsaturated acids, keto-substituted unsaturated acids, ω-enals, unsaturated esters and an unsaturated γ-lactone.

Fatty acids were prepared from beef tallow in the laboratory by alkalization and acidification under a nitrogen atmosphere at temperatures below 100 C. The minor constituents in the beef tallow fatty acids were isolated by the silicic acid method as described previously. They were fractionated by silicic acid liquid column chromatography and characterized by chemical functional group analyses, elemental analyses and infrared spectrophotometric methods. The results suggest that the minor constituents in commercial fatty acids were partly present in the original raw material of beef tallow and were partly formed as artifacts during the manufacturing process.

The acidic volatile decomposition products (VDP) produced by a hydrogenated cottonseed oil maintained at 185C with periodic frying of moist cotton balls and with periodic additon of fresh fat to replenish the fat lost due to evaporation, decomposition, and adsorption by the cotton balls were collected, fractionated and characterized. A total of 38 acidic compounds were identified. They consisted of 13 saturated acids, 11 unsaturated acids, five aldehydo acids, two hydroxy acids, two keto acids, and five dicarboxylic acids. The similarities and differences between the acidic VDP produced by a more unsaturated corn oil and a more saturated hydrogenated cottonseed oil under simulated commerical deep fat frying conditions are discussed.

A laboratory apparatus has been designed which can be used to quantitatively collect the volatile decomposition products produced during deep fat frying under simulated restaurant conditions. In order to study the chemical reactions of frying fat without any inter-reaction with the food fried, moist cotton balls were fried in corn oil.

Twenty-one mono-carbonyl compounds were identified in a reverted but not rancid soybean oil with a peroxide number of 2.7 meq/kg and a flavor score of 6.0. Six of the carbonyl compounds were saturated methyl ketones, ten were saturated aldehydes and five were 2-enals. The amount of 2,4-dienals in the reverted soybean oil was too small to be fractionated and identified. One fraction of the 2,4-dinitrophenylhydrazones of mono-carbonyl compounds obtained was different in chemical properties from those of the four known classes of compounds; viz. saturated aldehydes, saturated ketones, 2-enals, and 2,4-dienals. The chemical identity of this fraction has not been completely established.

Chemical identification of the volatile decomposition products (VDP) produced by fats and oils under conditions of deep fat frying is important for the elucidation of the mechanisms of thermal oxidation, for the study of their effects upon human nutrition, and for their contribution to the deep fat fried flavor of foods. The acidic VDP produced by corn oil maintained at 185C for 30 hr with periodic frying of moist cotton balls and with addition of fresh oil to replenish the oil lost due to evaporation, decomposition, and adsorption by the cotton balls were fractionated by repeated gas chromatography. The gas chromatographic fractions were identified by IR and mass spectrometry. A total of 30 acids were characterized. They consisted of 12 n-aliphatic saturated acids, seven 2-enoic acids, one 3-enoic acid, three keto acids, two hydroxy acids, four dicarboxylic acid and one aromatic acid. It is suggested that the effects of some of these acids upon human nutrition be studied.

A laboratory apparatus that could be used to treat pure triglycerides under simulated deep fat frying conditions was designed and built. By the use of this apparatus, the volatile decomposition products produced during frying could be quantitatively collected at the same time. Pure trilinolein was treated in this apparatus at 185 C for 74 hr. The volatile decomposition products were collected quantitatively. Their fractionation and identification will be reported in a subsequent paper. The nonvolatile decomposition products were isolated from the treated trilinolein as the non-urea-adduct-forming methyl esters. They constituted 26.3% of the treated trilinolein and were separated into seven fractions by repeated liquid column chromatography. Chemical and physical analyses of these fractions indicated that the chemical reactions taking place under simulated deep fat frying conditions were not entirely the same as those during simple heating under air. One of the seven fractions was further purified by thin layer chromatography and then identified as a cyclic carbon to carbon linked dimer which amounted to 4.9% of the treated trilinolein. Another fraction was further purified by thin layer chromatography, followed by gas chromatography, and then identified as noncyclic hydroxy dimers formed through carbon to carbon linkages. The noncyclic dimers constituted 2.8% of the treated trilinolein. The other four fractions were depolymerized by hydroiodic acid. The depolymerization products were fractionated by thin layer chromatography and then analyzed. It was estimated that the treated trilinolein contained 8.4% of trimers formed through carbon to carbon linkages, and 4.9% of dimers and trimers joined through carbon to carbon or carbon to oxygen linkages in the same molecule and also trimers, in which all the three monomeric units were joined through carbon to oxygen linkages.

The volatile flavor compounds in a reverted soybean oil with a peroxide number of 4.3 meq/kg were isolated by a semicontinuous counter-current vacuum steam-distillation process, fractionated by repeated gas chromatography, and identified by infrared and mass spectrometry. A total of 71 compounds were identified, which included 19 acids, 39 nonacidic compounds, and 13 tentatively identified compounds. The acids consisted of eight normal saturated acids, nine α,β-unsaturated acids, a branch-chain acid, one hydroxy acid, two keto acids, three lactones, and one aromatic acid. The nonacidic compounds consisted of two esters, eight normal saturated aldehydes, two branched-chain aldehydes, five 2-enals, three dienals, eight ketones, eight alcohols, six hydrocarbons, and four aromatic compounds. The mechanism of formation of the identified compounds indicated that they were mostly primary or secondary autoxidation products of the hydroperoxides of the unsaturated fatty esters. Since many of the identified compounds were produced from oleic and linoleic acids, it is doubtful that linolenic acid was solely responsible for the reversion flavor. Of the compounds identified two are of unusual interest. They are 1-decyne and 2-pentyl furan. The former is the first acetylenic compound reported as the autoxidation products of unsaturated fatty esters which contained only double bonds. The latter imparts to an oil at concentrations of 5–10 ppm a beany and grassy flavor reminiscent of that of a reverted soybean oil. Since this compound is postulated as being produced by the autoxidation of linolenic acid, it is suggested that the presence of linolenic acid catalyzes the autoxidation of linoleic acid and possibly alters the decomposition pattern of its hydroperoxides.

Two distinct types of hydrogenation flavor may originate from catalytic hydrogenation of fats and oils. One is the characteristic flavor developed during hydrogenation. After it is removed by deodorization, the second type of hydrogenation flavor may develop during the storage of the bland deodorized hydrogenated fat.

The gas chromatogram of the isolated volatile by-products I, which were produced during catalytic hydrogenation of soybean oil is quite different from that of the isolated volatile byproducts II, which were produced by a duplicate sample of the same oil subjected to the same conditions of hydrogenation with no nickel catalyst. Many of the peaks on these two gas chromatograms had different retention times. Furthermore, catalytic hydrogenation of I did not alter its gas chromatogram to equal that of II. The side reactions which may take place when an oil is treated under hydrogenation conditions are, therefore, affected by the presence of nickel catalys.

A new diterpene, named rosmariquinone, was isolated from the leaves ofRosmarinus officinalis L. The leaves were first extracted using methanol and, upon further purification, this extract yielded rosmariquinone. Structure elucidation of the antioxidant was done using IR, MS,1H-NMR and13C-NMR.

The nonacidic volatile decomposition products (VDP) produced by a deodorized hydrogenated cottonseed oil maintained at 185C with periodic frying of moist cotton balls and with periodic addition of fresh fat to replenish the fat lost due to evaporation, decomposition, and adsorption by the cotton balls were collected, fractionated and characterized. A total, of 61 compounds were identified. They consisted of 17 hydrocarbons, eight alcohols, two esters, three lactones, 22 aldehydes, seven ketones, and two aromatic compounds.

trans-3,5-Dimethoxystilbene has been isolated from high quality tall oil fatty acids (unsaponifiables 1.5% maximum, rosin acids 1.5% maximum), using liquid column chromatography and low temperature solvent fractional crystallization. The structure of this compound was determined with the aid of IR, mass and NMR spectrometry. Thetrans-3,5-dimethyoxystilbene was found to be responsible for the development of a red color during the epoxidation of the tall oil fatty acids.

Gas chromatography of the volatile by-products produced during the catalytic hydrogenation of an autoxidized soybean oil with a peroxide number of 11.2 meq/kg yielded approx 41 peaks. Twenty-one of the gas chromatographic fractions were collected and rechromatographed, and their chemical identity studied with micro-iR and mass spectrophotometry. These volatile by-products, according to peak area of gas chromatogram, showed a predominance of hydrocarbons and alcohols. The fractions which have been identified aren-octane,n-nonane,n-decane,n-heptadecane,n-hexanol,n-heptanol,n-decanol,n-hexanal,n-decanal and 3-nonanone. Among the gas chromatographic fractions collected,n-decanol has an odor most reminiscent of that of catalytic hydrogenation.

The minor constituents from a high quality commercial oleic acid (SCOA) were isolated and fractionated by liquid column chromatography. They were chemically characterized and their effects on the color stability of oleic acid during heating were determined. The results were compared qualitatively and quantitatively with those from a mixture of commercial oleic acids (MCOA) manufactured by 10 companies. It was found that, qualitatively, SCOA and MCOA contained the same type of minor constituents. However, quantitatively, the MCOA contained 1.18% of minor constituents whereas the SCOA contained only 0.81% of minor constituents. The amount of effective minor constituents which had an adverse effect on the color stability of oleic acid during heating was 0.09% for SCOA vs 0.45% for MCOA.