Applied ultraviolet spectrophotometry of fats and oils

Beadle, B. W.

doi:10.1007/bf02640960

Cited by 22 publications

(6 citation statements)

References 12 publications

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“…The concentration of alkali is very important. Potter and Kummerow (6) showed that k~6 for arachidonic acid was 27.7 whereas Beadle et al (7) reported a value of 22.6. However the former used 12.5% KOH-glycol, the latter only 6.6% KOH-glyeol.…”

Section: Specific Extinction Coefficients and Alkali-isomerizationmentioning

confidence: 99%

Isolation of eicosapentaenoic and docosapentaenoic acids from natural sources as their methyl esters by adsorption and distillation techniques

Herb

Witnauer

Riemenschneider

1951

J Americ Oil Chem Soc

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T HE isolation of pure linoleie, linolenic, and arachidonic acids from natural sources by physical rather than by chemical methods has been described in recent publications (1, 2) from this laboratory. The importance of geometrical configuration of the polyunsaturated acids in relation to the alkali-isomerization spectrophotometric method of analysis has also been discussed. New constants determined on these pure "natural" acids were proposed (3) for use in this method.In the course of the work on isolation of araehidonic acid (as its methyl ester) from adrenal lipids, fractions of greater unsaturation than that of methyl arachidonate were obtained (2). Preliminary examination of this material indicated the presence of methyl eicosapentaenoate. After alkali-isomerization the product had characteristic absorption maxima at 346 and 328 m~ in addition to the principal maxima at 315, 301, 268, and 233 millimicrons.This highly unsaturated material has now been subjected to further fractionation on silicic acid adsorption columns and by high-vacuum distillations. Eieosapentaenoic and doeosapentaenoie acids as their methyl esters were isolated and their specific extinction coefficients determined after isomerization with alkali. Further evidence of their identity was obtained by iodine values, refractive indices, and by melting points, saponification equivalents, and X-ray diffraction measurements on hydrogenated portions. The results permit an extension of the spectrophotometric method to the analysis of highly unsaturated lipids, such as are found in nearly all glandular fats and specialized tissues. Experimental and DiscussionStarting Materials. All fractions of methyl esters having iodine values greater than the theoretical value (318.8) for methyl arachidonate, which were obtained in the adsorption fractionation of adrenal lipid methyl esters (2), served as starting material. In all 11.6 g. were obtained from this previous work. The average iodine value was 359.0. The specific extinction 3 coefficients of this concentrate after isomerization in 11% for 45 minutes at 180~ under nitrogen were : k233 = 49.8 ; k26 s -~-35.0 ; ka~ = 21.8 ; k3~6 ~ 8.7. No absorption maximum was found above 346 rag.Adsorption Fractionation on Silicic Acid. Essentially the sama technique as described in previous work (1, 2) was followed except that the glass columns were packed by introducing a pre-heated slurry of the silieic acid-filter aid mixture in petroleum ether.

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Section: Specific Extinction Coefficients and Alkali-isomerizationmentioning

confidence: 99%

Isolation of eicosapentaenoic and docosapentaenoic acids from natural sources as their methyl esters by adsorption and distillation techniques

Herb

Witnauer

Riemenschneider

1951

J Americ Oil Chem Soc

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“…Other methods, with variations in procedure designed primarily to effect improvements in sensitivity. Typical applications of spectrophotometric methods have been discussed by Beadle (14). (I2), and others.…”

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confidence: 99%

Standardization of spectrophotometric methods for determination of polyunsaturated fatty acids using pure natural acids

Brice

Swain

Herb

et al. 1952

J Americ Oil Chem Soc

114

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Summary Spectrophotometric methods of analysis for the polyunsaturated constituents of oils and fats have been carefully restandardized for several conditions of alkali‐isomerization, using purified methyl esters of linoleic, linolenic, and arachidonic acids prepared by physical rather than by chemical means. A number of vegetable oil and animal fat samples were subjected to spectrophotometric analysis, and the results based on natural and on bromination‐debromination fatty acid standards were compared. The natural fatty acid standards lead to significantly higher accuracy and their use in the spectrophotometric analysis of natural fatty materials is strongly recommended. Results obtained under different conditions of isomerization were in satisfactory agreement. An isomerization time of 45 minutes is recommended rather than 25 or 30 minutes. The glycerol‐air technique is preferred for general use because of its simplicity and high precision. The ethylene‐glycol‐nitrogen technique is a close second choice because of the greater transparency of reagent blanks.

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“…The percent con jugated diene acids increased slightly during pasteurization while that of linoleic decreased. This possibly is evidence of slight oxidation (1,6).…”

Section: Resultsmentioning

confidence: 95%

Changes in the Lipid Fraction of Valencia Orange Juice During Pasteurization

Huskins

Swift

1953

Journal of Food Science

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Earlier investigations at this laboratory (3,5) demonstrated that changes occur in the lipid fraction of pasteurized orange juice during storage, but did not show whether any of these vere due to pasteurization. Since pasteurization is a time-temperature treatment like storage, although employing a higher temperature for a shorter time, it might conceivably produce similar effects. One of the possible explanations of differences in the flavor of pasteurized as compared to the flavor of fresh orange juice might be compositional changes in the juice lipids-probably in combination with loss o r change in the volatile flavoring constituents during heating; caramelizatioii of the sugars ; reactions involving sugars, acids, amino acids, ascorbic acid, and proteins.The purpose of this paper is to compare analytical data on the compo-&ion of the lipids from fresh orange juice and from the same juice almost immediately after pasteurization. EXPERIMENTAL Preparation of lipids. The fresh Valencia orange juice was obtained from a local processing plant during the 1950 season. In the laboratory, it was mixed and divided into 2 equal batches. One batch was pasteurized at 90.4"C., canned, cooled quickly, and placed in storage at 2-5°C. for 2 days until the lipid could be extracted. The fresh juice was processed promptly.Lipids were extracted from the batch of fresh juice and later from the pasteurized juice using the procedure described by Huskins, Swift, and Veldhuis (3). The juice was passed through an Oliverb filter and the lipids were extracted from the material retained in the filter cake with acetone. This solvent was then removed by evaporation and the lipid taken up in petroleum ether. This step eliminated the water that had been extracted from the damp filter cake. The petroleum ether solution of the lipids was placed in a 3-necked flask equipped with a stirrer and condenser. After most of t h e petroleum ether had been distilled at atmospheric pressure, the flask was immersed in cold water, the stirrer was started, and vacuum connected. The water bath was heated slowly (45 minutes) to boiling and f o r 15 minutes thereafter. During this time t h e lipid was stirred continuously and the vacuum was maintained at 10 mm. of mercury. Ice water was circulated through the condenser and a dry ice t r a p was placed in t h e line between the vacuum pump and the condenser. During this vacuum process of drying the lipid, a small amount of fragrant volatile liquid was retained in the dry ice trap. This substance was only slightly soluble in water and had a spectral absorption maximum of 244 mp. It was not identified.Analytical methods. Samples of the lipids were saponified and the unsaponifiable matter was determined according to the Eerr-Sorber method. The f a t t y acids were extracted from the acidified aqueous residue with petroleum ether. Aliquots of the aqueous solution remaining were used for the determination of the resin acids, referred t o b y "One of the laboratories of the Bureau of Agricultural and Industrial Chemist...

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Applied ultraviolet spectrophotometry of fats and oils

Cited by 22 publications

References 12 publications

Isolation of eicosapentaenoic and docosapentaenoic acids from natural sources as their methyl esters by adsorption and distillation techniques

Isolation of eicosapentaenoic and docosapentaenoic acids from natural sources as their methyl esters by adsorption and distillation techniques

Standardization of spectrophotometric methods for determination of polyunsaturated fatty acids using pure natural acids

Changes in the Lipid Fraction of Valencia Orange Juice During Pasteurization

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