Effects of processing on quality of soybean oil

The fate of major and minor components of soybean oil is examined at each stage of processing. Relationships are then drawn upon the effect on the quality of finished oil. General topics covered are (a) triglycerides and polyunsaturated fatty acids, (b) free fatty acids, (c) mono- and diglycerides, (d) phospholipids, (e) minor constituents, such as tocopherols, color bodies, and metal ions, (f) rearrangement and decomposition products, (g) foreign or toxic compounds not native to soya and (h) other additives, such as refining aids.     

Nephelometric determination of phosphorus in soybean and corn oil processing

A procedure to measure phosphorus content of soybean and corn oil samples has been developed using nephelometry (turbidity). The method uses the relationship between phosphorus level due to phosphatides in vegetable oil and turbidity formed in phosphatide mixtures. The rapid 10-min determination of phosphorus in process samples is 30 times faster than colorimetric methods. Phosphorus vs turbidity data formed nearly linear relationships for crude, degummed, once-refined, bleached and deodorized soybean and corn oil process samples.     

The determination of tocopherol content during the commercial processing of soybean oil

Summary A method for the analysis of the total tocopherols in soybean oil has been presented, and judged by distillation and other procedures is estimated to be accurate to within 10%. A discussion is made of the tocopherol to within 10%. A discussion is made of the tocopherol losses in various steps of soybean oil refining. Communication No. 115 from the Research Laboratories of Distillation Products, Inc., Rochester, New York. (Presented at The American Oil Chemists Society meeting in New Orleans, May 20–22, 1947.)     

Effects of processing on the oxidative stability of soybean oil produced in Mexico

The stability parameters of 22 samples of soybean oil produced in Mexico were determined. Samples were analyzed for moisture, color, free fatty acids, peroxide value, p-anisidine value, fatty acid profile, metals, flavor, and Rancimat test for oxidative stability. Results obtained were compared with the stability parameters of soybean oil sproduced in the United States and Costa Rica. The fatty acid profile in all samples analyzed corresponded to the expected profile for a 100% soybean oil. Sixty-four percent of the oils had oxidative stabilities similar to those reported for soybean oils from the United States and Costa Rica. This suggests that in spite of the good quality, the soybean oil production process in Mexico needs further improvement. Especially important is maintaining appropriate control during the degumming and bleaching steps. Special consideration should be given to preserving the natural antioxidants present in the oil.     

Effects of processing steps on the contents of minor compounds and oxidation of soybean oil

The processes of degumming, alkali refining, bleaching and deodorization removed 99.8% phospholipids, 90.7% iron, 100% chlorophyll, 97.3% free fatty acids and 31.8% tocopherols from crude soybean oil. The correlation coefficient between the removals of phosphorus and iron in soybean oil during processing was r = 0.99. The relative ratios of α-, β -, γ- and δ-tocopherols in crude oil, degummed oil, refined oil, bleached oil and deodorized soybean oil were almost constant, γ- and δ -tocopherols represented more than 94% of tocopherols in soybean oil. The order of oxidation stability of oil is crude > deodorized > degummed > refined > bleached oil.     

Hexane elimination from soybean oil by continuous packed tower processing with supercritical CO2

Hexane elimination is the most energy-consuming step in the industrial extraction of soybean oil. It utilizes three sets of equipment: two evaporation stages in series followed by a stripper at a pressure of about 0.07 bar. The final hexane residue in the oil is about 1000 ppm. We propose an alternative to the present process for hexane elimination, based on the extraction of the soybean oil/hexane mixture with supercritical CO₂ in a continuous countercurrent packed tower. In this work, we tested a soybean oil/hexane mixture feed containing 10% by weight of hexane. Various pressures and temperatures of the column were tested to reduce hexane residue in the oil. The extraction process was demonstrated to be very effective for hexane separation. Indeed, at the bottom of the column we recovered soybean oil containing quantities of hexane as low as 20 ppm when we operated at 120 bar, 40°C. The effect of process parameters is also discussed.     

Nutritional properties of coconut oil

Coconut oil has been one of the most widely used vegetable oils since the agricultural revolution. Only in recent years has there been controversy over the desirability of its uso. Controversy has usually stemmed from observed disturbances of calcium or cholesterol metabolism when hydrogenated coconut oil was fed, frequently with inadequate linoleate supplementation, to experimental animals. Furthermore, in many of the studies involving cholesterol, entirely unphysiological amounts of cholesterol have been included in the diet. It is contended here that the findings in such studies are the consequence of abnormal nutrition rather than inherent defects in coconut oil. Evidence from epidemiological studies of arteriosclerosis in populations consuming large amounts of coconut oil are cited to show that coconut oil in a natural diet is not disadvantageous and may even be of advantage. The high level of medium chain fatty acids in coconut oil is discussed from the point of view that they may contribute to beneficial effects on the part of coconut oil under some abnormal conditions.     

Nutritional characteristics of DAG oil

Excess calorie intake in industrialized countries has prompted development of fat substitutes and other lower-calorie dietary items to enhance health. DAG cooking oils, with a 1,3 configuration, taste and have the texture of commonly used TAG cooking oils. Because they are not hydrolyzed to 2-MAG in the gut, the absorption and metabolism of DAG oil differs from that of TAG. Among the physiological differences are lower postprandial lipemia and an increased proportion of FA being oxidized instead of stored. Preliminary studies suggest that these differences in energy partitioning between DAG and TAG may be usefully exploited to reduce the amount of fat stored from cooking oil and oil components of food items. Over 70 million bottles of DAG oil have been sold in Japan since its introduction in February 1999, and the product is being test-marketed in the United States. It is hoped that wider use of DAG oil may provide one additional means of preventing obesity.     

Metals in soybean oil

Certain metals often produce deleterious effects when present in soybean oil. Trace quantities of copper, iron and manganese dramatically reduce the oxidative stability of edible oils. The presence of calcium and magnesium in crude oils reduces the efficiency of degumming and refining operations. Sodium soaps reduce bleaching efficiency by inactivating adsorption sites on bleaching earth. Phosphatides or phosphorous containing lipids exert a poisoning effect on hydrogenation catalysts. Nickel, an artifact of hydrogenation, must be removed from the oil for health, stability and safety considerations. This paper provides an overview of the various effects of metals on processing and stability, describes how to inhibit or diminish their activity, and discusses various analytical techniques for identification and quantitation of the metals present in soybean oil.     

Distribution of chlorinated pesticides in soybeans,soybean oil,and its by-products during processing

Soybean samples were collected from seven different locales in Central Illinois and subjected to analysis for chlorinated pesticides. Different parts of the beans showed varying levels of residue concentrations. It was found that pesticide residues had a tendency to accumulate, in descending order, in hypocotyls, hulls and cotyledons on the basis of ground samples. When oils extracted from the same fractions were analyzed, much higher concentrations of residues were located in hulls than hypocotyls, which had greater concentrations than cotyledons. Crude, refined, bleached and deodorized oils, soapstock, Fuller’s earth sludge and deodorization condensate swere analyzed for hexachlorobenzene isomers, heptachlor, heptachlor epoxide, aldrin, dieldrin, DDT, DDD and DDE. None of the processing steps except deodorization were completely effective in the removal of chlorinated pesticide residues. Oil deodorized at 250 C under 1-5 mm pressure was almost free of such residues, whereas all the residues were concentrated in deodorization condensate.     

In-situ alcoholysis of soybean oil

In-situ alcoholysis of soybean oil with methanol, ethanol,n-propanol, andn-butanol was investigated, as well as the extraction of the oil with these solvents, to explain the progress ofin-situ alcoholysis and to determine the parameters that affect this reaction. Because methanol is a poor solvent for soybean oil, the amount of oil dissolved in methanol and converted to methyl esters was low afterin-situ alcoholysis. Ethyl, propyl, and butyl esters of soybean fatty acids could be obtained in high yields fromin-situ alcoholysis of soybean oil with these alcohols.In-situ alcoholysis proceeded through dissolution and alcoholysis of triglycerides successively, and the overall reaction rate was determined by the extraction and alcoholysis rates. The parameters, affecting yield and purity of the product esters, were mainly those that favor extraction rate.     

Acid-catalyzed alcoholysis of soybean oil

In an effort to increase utilization of fats and oils with high concentrations of FFA, acid catalysts were investigated at elevated temperatures to determine their efficacy under various operating conditions. Acid-catalyzed alcoholysis of soybean oil using sulfuric, hydrochloric, formic, acetic, and nitric acids was evaluated at 0.1 and 1 wt% loadings at temperatures of 100 and 120°C in sealed ampules, but only sulfuric acid was effective. Kinetic studies at 100°C, 0.5 wt% sulfuric acid catalyst, and nine times methanol stoichiometry provide >99 wt% conversion of TG in 8 h and less than 0.8 wt% FFA concentrations at less than 4 h. Reaction conditions near 100°C at 0.1 to 0.5 wt% were identified as providing the necessary conversions in a 24-h batch cycle while not darkening the product as is typical with high temperatures and catalyst loadings. The oxygen/air contained in the reaction ampules at the onset of the reaction was not sufficient to color the product, but the product darkened if atmospheric air contacted the reacting mixture. The presence of small amounts of stainless steel significantly decreased conversions.     

Enzymatic glycerolysis of soybean oil

Enzymatic glycerolysis of soybean oil was studied. Of the nine lipases that were tested in the initial screening, Pseudomonas sp. resulted in the highest yield of monoglycerides. Lipase from Pseudomonas sp. was further studied for the influence of temperature, thermal stability, enzyme/oil ratio, and glycerol/oil ratio. A full factorial optimization approach was performed. The following conditions were tested over the specified ranges: temperature (30–70°C), thermal stability (30–70°C), enzyme/oil ratio (0.05–0.2 g enzyme/10 g oil), glycerol/oil ratio (1:1–3:1 glycerol/oil molar ratio) and 1 h reaction time. The stability of the enzyme at the reaction temperature was also incorporated as a separate variable. At temperatures above 40°C enzyme denaturation offset the higher activity. The optimal conditions were selected to be the basis for a continuous process: 40°C, a glycerol/oil molar ratio of 2:1, and an enzyme/oil ratio of 0.1 g enzyme/10 g oil. A definition for glycerolysis activity was adopted. The glycerolysis activity (1 GU) was defined as the amount of enzyme necessary to consume 1 μmol of substrate (glycerol and oil) per minute. This research is intended to explore the reaction parameters that are important in a continuous enzymatic glycerolysis process.     

Hydrogenation of oxidized soybean oil

Anderson Clayton Foods, Richardson, TX 75080 Portions of refined and bleached soybean oil were stored at various temperatures for various lengths of time, then hydrogenated to 70 iodine value (IV) to find the effect of peroxides on the rate of hydrogenation and on characteristics of hydrogenated product. Samples were treated up to 3 wk at up to 65°C and provided samples with peroxide values (PV) of up to 358. All samples were analyzed, hydrogenated, and reanalyzed. Peroxides affected the fatty acid composition as determined by gas chromatography, the calculated iodine value based on fatty acid composition, and rate of hydrogenation. Peroxides also affected the selectivity of hydrogenation and slope of the solids curve in hydrogenated products.     

The hydrogenation of soybean oil

Journal of the American Oil Chemists' Society - 1