FTIR estimation of free fatty acid content in crude oils extracted from damaged soybeans

A user-interactive computer-assisted Fourier transform infrared (FTIR) method has been developed for estimation of free fatty acids (FFA) in vegetable oil samples by deconvolution of the infrared (IR) absorbances corresponding to the triglyceride ester and FFA carbonyl bonds. Peak areas were used to determine FFA as a percentage of the total carbonyl areas in weighed standards of refined, bleached, deodorized soybean oil containing from 0 to 5% added oleic acid. These data for percent FFA by FTIR were compared to corresponding FFA data obtained by two titration methods-the AOCS Official Method Ca 5a-40 and the Official Method with a slight modification. Correlation coefficients were 0.999 for the Ca 5a-40, 0.999 for the modified and 0.989 for the FTIR methods. FFA in samples of crude soybean oils extracted from damaged beans (0.5 to 2.1% FFA) were measured by FTIR and compared to data obtained by titration of the same samples (correlation coefficient, 0.869). To whom correspondence should be addressed at National Center for Agricultural Utilization Research, Agriculture Research Service, U.S. Department of Agriculture, 1815 North University Street, Peoria, IL 61604. ¹The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

Relative reduction rates of fatty acid isomers by hydrazine

Mixtures of fatty acids and of hydrocarbons have been reduced by hydrazine in ethyl alcohol solution at 50 C. Samples were removed during reduction for analysis and the relative reduction rates calculated by digital computer.cis-15-Octadecenoic acid is reduced 1.3 times as fast as itscis-9-isomer. No differences were found amongcis-6,9- and -12-octadecenoic acids.cis-3-Octadecene was also reduced 1.3 times as fast as thecis-9-isomer andcis-1-octadecene 8.6 times as fast. Elaidic acid was reduced 1.27 times as fast as oleic. Presented at the AOCS Meeting, Chicago, October 1967. No. Utiliz. Res. Dev. Div., ARS, USDA.     

Flavor and oxidative stability of hydrogenated and unhydrogenated soybean oils: Effects of antioxidants

Flavor and oxidative stabilities were studied by organoleptic evaluation and chemical analysis of three different samples of soybean oil: unhydrogented (I); hydrogenated with nickel catalyst (II); and hydrogenated with copper-chromium catalyst (III). Analyses for these oils were: I II III iodine Value 138 109 113 Linolenate, % 8.3 3.3 0.4 Each oil was deodorized with the addition of either citric acid alone or citric acid plus BHA and BHT antioxidants. Addition of antioxidants did not improve the flavor stabilities of the oils in accelerated storage tests but did improve the flavor stabilities of II and III in light exposure tests. All three oils that received the same additive treatment had equivalent flavor stability in both accelerated storage and light exposure tests. However, both hydrogenation and antioxidant treatment improved oxidative stability as measured by the Active Oxygen Method. There was good correlation between flavor score and the logarithm of the peroxide value determined at the time of tasting. Presented at the AOCS Meeting, New York, May 1977.     

Performance evaluation of hexane-extracted oils from genetically modified soybeans

Soybeans produced by induced mutation breeding and hybridization were cracked, flaked and hexane-extracted, and the recovered crude oils were processed to finished edible oils by laboratory simulations of commercial oil-processing procedures. Three lines yielded oils containing 1.7, 1.9 and 2.5% linolenic acid. These low-linolenic acid oils were evaluated along with oil extracted from the cultivar Hardin, grown at the same time and location, and they were processed at the same time. The oil from Hardin contained 6.5% linolenic acid. Low-linolenic acid oils showed improved flavor stability in accelerated storage tests after 8 d in the dark at 60°C and after 8h at 7500 lux at 30°C, conditions generally considered in stress testing. Room odor testing indicated that the low-linolenic oils showed significantly lower fishy odor after 1 h at 190°C and lower acrid/pungent odor after 5 h. Potatoes were fried in the oils at 190°C after 5, 10 and 15 h of use. Overall flavor quality of the potatoes fried in the low-linolenic oils was good and significantly better after all time periods than that of potatoes fried in the standard oil. No fishy flavors were perceived with potatoes fried in the low-linolenic oils. Total volatile and polar compound content of all heated oils increased with frying hours, with no significant differences observed. After 15 h of frying, the free fatty acid content in all oils remained below 0.3%. Lowering the linolenic acid content of soybean oil by breeding was particularly beneficial for improved oil quality during cooking and frying. Flavor quality of fried foods was enhanced with these low-linolenic acid oils.     

Glyceride structure of vegetable oils by countercurrent distribution. V. Comparison of natural,interesterified, and synthetic cocoa butter

The glyceride structure of cocoa butter is of considerable practical importance and of particular theoretical interest Countereurrent distribution, gas chromatography, and isotopic dilution methods are employed in its study. The observed fractionation of glycerides is acounted for by assuming that palmitie and stearic acids are randomly esterified on the 1 and 3 positions of glycerol and that oleic is on the 2 position, as demonstrated by other workers. Complete randomization of the specifie structure of cocoa butter through the application of interesterification eatalysts greatly alters its physical A glyceride synthesized according to the “1,3 random palmitostearo-2-olein” concept has properties similar to natural cocoa butter. Presented before Division of Agricultural and Food Chemistry, American Chemical Society Meeting, Cleveland, O., April 5–14, 1960. This is a laboratory of the Northern Utilization Research and Development Division, Agricultural Research Service, U.S. Department of Agriculture.     

Odor considerations in the use of frying oils

Odors generated into cooking and serving areas during use of oils in pan frying and deep-fat frying are of concern to home and institutional consumers and, in some respects, to industrial users. Odor considerations are factors in the selection of types of oils to be used in both domestic and foreign markets. Comparative techniques have been developed to evaluate room odor characteristics of frying oils. Evaluation research has been done on various oils and cooking fats for room odors developed during frying. Improved odor characteristics contributed by additives to oils have been studied, as well as relationship between the linolenate content of soybean oil and its characteristic room odor. The nature of the volatile constituents which contribute to room odors during frying is the subject of continuing research efforts. Presented at AOCS meeting, St. Louis, Missouri, May 1978.     

Determination of ultratrace metals in hydrogenated vegetable oils and fats

Ultratrace levels of nickel, chromium, copper and iron occurring in hydrogenated vegetable oil products were estimated by dispersion of the samples in 4 methyl-2-pentanone and atomic absorption analysis by the graphite furnace technique. The principal goals in establishing the analytical methods were improved sensitivity to metals at low levels and applicability to limited amounts of products. Using reproducibility and linearity of response as criteria, optimum oil concentration in solvent and instrument parameters were established. For a series of commercial products, the method of standard addi-tions was adopted to correct for matrix differences between the products and salad oil-based standards. The range for the metals was determined in five cooking oils: Ni, 29–207 ppb; Cr, 1–5 ppb; Cu, 13–37 ppb; and Fe, 138–301 ppb; in recovered oils from five margarines: Ni, 34–70 ppb; Cr, 2–12 ppb; Cu, 26–58 ppb; and Fe, 239–540 ppb; and in five solid shortenings: Ni, 592–2772 ppb; Cr, 8–35 ppb; Cu, 26–108 ppb.     

Double bond position affects metabolism of cis-Octadecenoates

The metabolic fate of cis-positional isomers of octadecenoates has been compared to that of naturally occurring oleic acid (cis-delta9). Radioactive mixtures of tritium-labeled positional octadecenoate isomer and oleic acid-10(-14)C were administered to laying hens, and their eggs were analyzed for the isotopic ratios (3H/14C) incorporated into total egg lipid, triglycerides, and phospholipids. Variations in the isotopic ratios indicated the comparative metabolic utilization of cis-positional isomers delta8 through delta12. Incorporation into egg lipid fractions is as follows: triglycerides: delta9 greater than delta8, delta9 greater than delta10, delta9 greater than delta11, delta9 greater than 12; phospholipid: delta9 greater than delta8, delta9 greater than delta10, delta9 less than delta11, delta9 less than delta12.