Gary R. List

Hydrolysis of soybean oil. in a subcritical water flow reactor

Subcritical water has been recently demonstrated to be a viable medium for conducting hydrolysis reactions on a variety of organic compounds. In this study, the hydrolysis of triglycerides in soybean oil to their respective free fatty acids has been affected using a flow reactor. The flow reactor permits hydrolysis to be accomplished without the need of a catalyst but requires higher temperatures than previously used in a static system to attain >97% product conversion. Using a high pressure view cell as a diagnostic aid, it was found that the oil miscibility with water is crucial to attaining a high conversion to the free fatty acids. Water to oil ratios of 2.5∶1–5∶1 were found to optimal for high conversions as well as residence time between 10–15 minutes in the open tubular reactor. Such rapid hydrolysis times contrast with multi-hour conversions utilized industrially to achieve a 96–98% fatty acid yield. Although conversion of the all natural cis forms of the fatty acids to some trans form occurred, the isolated products were clear and free of degradation products, unlike previous results reported for the reaction run in a closed vessel under static conditions at these elevated temperatures (>300 °C). Determination of the trans fatty acid content of aqueous hydrolyzed oils has not been previously reported, however they are of minor importance since the produced fatty acid mixtures are primarily intended for industrial utilization and not for food consumption.

Physical Properties of Interesterified Fat Blends

Fat blends, formulated by mixing fully hydrogenated soybean oil with nine different commonly used vegetable oils in a ratio of 1:1 (w/w), were subjected to interesterification (also commonly referred to as rearrangement or randomization) with sodium methoxide catalyst. Fatty acid composition and triacylglycerol molecular species of each fat blend and the interesterified product were determined and correlated with the following physical properties: melting, crystallization characteristics and solid fat content. The differences in the endothermic and exothermic peak temperatures, total heat of fusion and crystallization (β and β′ crystalline content) and solid fat content among the fat blends clearly showed the effect of the composition of each oil on the physical properties. Oils that contained a considerable amount of palmitic acid had a favorable influence on the crystallization and polymorphic form of interesterified fat blends.

Determination of oil content in oilseeds by analytical supercritical fluid extraction

The total oil content of soyflakes, canola seed and wetmilled corn germ were determined by analytical supercritical fluid extraction (SFE) with carbon dioxide as the extraction solvent. Results obtained by SFE were in excellent agreement with those obtained by a conventional Soxhlet technique with organic solvents. The analytical-scale SFE technique yielded average means within one standard deviation of the means derived from the organic solvent-based methodology. Matrices containing both high and low oil content were successfully extracted with carbon dioxide at comparable precision to that obtained with the standard procedure. The supercritical fluid-based technique appears to be a suitable replacement for traditional extraction methods with organic solvents, thereby potentially eliminating the costs associated with solvent disposal and exposure of laboratory personnel to toxic and flammable solvents.

Supercritical CO2 degumming and physical refining of soybean oil

A hexane-extracted crude soybean oil was degummed in a reactor by counter-currently contacting the oil with supercritical CO2 at 55 MPa at 70°C. The phosphorus content of the crude oil was reduced from 620 ppm to less than 5 ppm. Degummed feedstocks were fed (without further processing,i.e., bleaching) directly to a batch physical refining step consisting of simultaneous deacidification/deodorization (1 h @ 260°C and 1–3 mm Hg) with and without 100 ppm citric acid. Flavor and oxidative stability of the oils was evaluated on freshly deodorized oils both after accelerated storage at 60°C and after exposure to fluorescent light at 7500 lux. Supercritical CO2-processed oils were compared with a commercially refined/bleached soybean oil that was deodorized under the same conditions.Flavor evaluations made on noncitrated oils showed that uncomplexed iron lowered initial flavor scores of both the unaged commercial control and the CO2-processed oils. Oils treated with .01% (100 ppm) citric acid had an initial flavor score about 1 unit higher and were more stable in accelerated storage tests than their uncitrated counterparts. Supercritical CO2-processed oil had equivalent flavor scores, both initially and after 60°C aging and light exposure as compared to the control soybean oil. Results showed that bleaching with absorbent clays may be eliminated by the supercritical CO2 counter-current processing step because considerable heat bleaching was observed during deacidification/deodorization. Colors of salad oils produced under above conditions typically ran 3Y 0.7R.

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).

Factors promoting the formation of nonhydratable soybean phosphatides

Whole, cracked and flaked soybeans were stored under a variety of conditions. After extraction with hexane, the crude oils were degummed in the laboratory, and the nonhydratable phospholipid (NHP) content was estimated from the phosphorus content of the degummed oil. Results showed that four interrelated factors promote NHP formation. These include (i) moisture content of beans or flakes entering the extraction process; (ii) phospholipase D activity; (iii) heat applied to beans or flakes prior to, and during, extraction; (iv) disruption of the cellular structure by cracking and/or flaking. Results from this study suggest that NHP formation can be minimized by control of the moisture of beans and/or flakes entering the extraction process, inactivation of phospholipase D enzyme, and optimizing temperatures during the conditioning of cracked beans or flakes.

Triacylglycerol structures of food fats high in saturated acids by HPLC and mass spectrometry

Triacylglycerol (TAG) compositions by area percent were obtained by reverse-phase high-performance liquid chromatography (RP-HPLC) coupled with atmospheric pressure chemical ionization mass spectrometry (APCI-MS) of highly saturated fatty acid fats, such as coconut, cocoa butter, palm, randomized palm, palm olein, and randomized palm olein oils. Accurate identification and quantitation of these TAG compositions were obtained and proved by comparison of the fatty acid composition calculated from the TAG composition obtained by APCI-MS with the fatty acid composition obtained by gas chromatography of the methyl esters of the transmethylated oils. Also, APCI-MS accuracy was proved by comparison of the experimental TAG composition with the predicted TAG composition for randomized oils. Average absolute errors, with respect to TAG quantitation and identification, were less than 1%. Our study identified and quantitated these TAGs present at greater than 0.1% (oil, number of TAGs): coconut, 99; palm, 27; randomized palm, 28; palm olein, 28; randomized palm olein, 29, and cocoa butter, 19. Concentrations of UUU, UUS, USS, and SSS TAGs, which can be determined accurately from RP-HPLC/APCI-MS of the actual TAG species, affected the physical properties of food formulation fats.

Analyses of Vegetable Oil Triacylglycerols by Silver Ion High Performance Liquid Chromatography with Flame Ionization Detection

Abstract Silver ion high performance liquid chromatography with a commercially available column with a simple isocratic mobile phase of acetonitrile in hexane and flame ionization detection was employed to separate and quantitate triacylglycerol species of vegetable oils. Coconut, palm, cottonseed, olive, safflower, sunflower, corn, pumpkinseed, linseed, soybean, and canola oils were analyzed, as well as randomized corn and soybean oils, and the blends and interesterified products of corn and soybean oil with cottonseed oil stearine. Fractionated triacylglycerol species were identified by gas chromatography of their methyl esters. Triacylglycerol composition was obtained by reversed phase and silver ion high performance liquid chromatography of the same oil. Oil fatty acid composition was determined by gas chromatography of the transmethylated oil and correlated with that calculated from the triacylglycerol composition by silver ion chromatography of the same oil. The triacylglycerol separation was mostly...

Supercritical carbon dioxide extraction of spent bleaching clays

Abstract The disposal of spent bleaching clay generated in the vegetable oil processing industry is a potential problem of environmental concern, due to the pyrophoric nature of the residual oil/clay mixture in land-fills. This study describes the use of SC-CO2 for processing both neutral and acidic clays used in the refining of soybean oil. Rapid extractions of spent bleaching clay can be affected at 10,000–12,000 psig by proper preparation of the clay substrate. Experiments utilizing both laboratory and pilot-plant extractors have yielded almost 100% of the adsorbed oil. Extraction of the clay can be facilitated by crossblending the clay with a diatomaceous earth-based dispersant. The oils recovered by the supercritical fluid extraction (SFE) process have properties (free fatty acid content, Lovibond color ratio, and phosphorus content) similar to those found for degummed-bleached oils.

Preparation of Spread Oils Meeting U.S. Food and Drug Administration Labeling Requirements for Trans Fatty Acids via Pressure-Controlled Hydrogenation

On July 11, 2003, the U.S. Food and Drug Administration (FDA) announced final regulations for trans fatty acid (TFA) labeling. By January 1, 2006, the TFA content of foods must be labeled as a separate line on the Nutrition Facts label. Products containing <0.5 g of TFA/14 g serving may be declared as zero. This paper describes technologies allowing compliance with TFA labeling requirements. Soybean oil was hydrogenated in a 2-L vessel at temperatures ranging from 120 to 170 degrees C at a hydrogen pressure of 200 psi. A commercial nickel-supported catalyst (25% Ni) was used at 0.02% Ni by weight of oil. The hydrogenated oils were characterized for fatty acid composition, solid fat content, and melting point. Compared to commercially processed soybean oil basestocks that typically contain approximately 40% TFA, those obtained at lower temperatures and higher pressures contain >56% less TFA. Basestocks prepared in the laboratory when blended with liquid soybean oil will yield spread oils meeting FDA labeling requirements for zero TFA, that is, <0.5 g of TFA/serving.