R. E. Beal

Quality of oil from damaged soybeans

Abstract and SummaryVarious processing steps were explored in an at-tempt to improve the quality of oil from field- and storage-damaged soybeans. A crude soybean oil (5.7% free fatty acid) commercially extracted from damaged soybeans was degummed in the laboratory with different reagents: water, phosphoric acid, and acetic anhydride. Two alkali strengths, each at 0.1 and 0.5% excess, were used to refine each degummed oil. After vacuum bleaching (0.5% activated earth) and deodorization (210 C, 3 hr), these oils were un-acceptable as salad oils. A flavor score of 6.0 or higher characterizes a satisfactory oil. Scores of water and phosphoric acid degummed oils ranged from 4.5 to 5.1, while acetic anhydride degummed oils aver-aged 5.6. Flavor evaluations of (phosphoric acid de-gummed) single- and double-refined oils (210 C deodorization) showed that the latter were signifi-cantly better. Flavor scores increased from 5.0 to about 6.0. To study the effects of deodorization tem-perature, the crude commercial oil was alkali-refined, water-washed and bleached with 0.5% activated earth, but the degumming step was omitted. Flavor evalua-tion of oil deodorized at 210, 230, and 260 C showed that each temperature increment raised flavor scores significantly. Further evaluations of specially proc-essed oils (water, phosphoric acid, and acetic anhy-dride degummed oils given single and double refinings and deodorized at 260 C) showed that deodorization temperature is the most important factor affecting the initial quality of oil from damaged beans. Flavor evaluations showed that hydrogenation and hydro-genation-winterization treatments produced oils of high initial quality, but with poorer keeping proper-ties than oils from normal beans. No evidence was found implicating nonhydratable phosphatides in the oil flavor problem. Iron had a deleterious effect in oils not treated with citric acid during deodorization.

Iron and phosphorus contents of soybean oil from normal and damaged beans

Analyses of commercial crude soybean oils showed a highly significant correlation of 0.74 between free fatty acid and iron content. Poor flavor characteristics exhibited by finished oils extracted from damaged beans may be caused in part by a higher free fatty acid and related higher iron content in crude oils. Source of the increased iron appears to be both damaged beams and steel processing equipment. Crude oil from damaged beans is 2–10 times higher in iron than crude oil extracted from sound beans. Iron appears loosely bound in soybeans, since autoclaving, spontaneous heating in storage, or treating with alcohol increased the level of iron in laboratory extracted crude oil from 0.2 to more than 1 ppm. Present data do not indicate that iron and phosphorus contents are associated statistically in extracted oils.

Partial hydrogenation and winterization of soybean oil

Soybean oil was hydrogenated under selective and nonselective conditions to give products with iodine values (I.V.) ranging from 85-115. The products were crystallized at 8C and examined for yield, stability, and fatty acid composition of the winterized oil. Changes in fatty acid composition, formation oftrans acids, and yield of winterized oil are approximately linear with the degree of hydrogenation. Stearine fractions, which are 15-20 I.V. units lower than winterized oil, were further crystallized in solvents to yield liquid oils and hard stearines.

Flavor evaluation of copper-nickel hydrogenated soybean oil and blends with unhydrogenated oil

Soybean oils hydrogenated to zero linolenate in the pilot plant with a mixed copper-nickel catalyst and a straight copper chromite catalyst were evaluated and compared for flavor and odor. Hydrogenated oils were winterized and deodorized and stabilized with butylated hydroxytoluene, butylated hydroxyanisole, citric acid, and methyl silicone. Taste panel flavor scores of stored oils and room odor scores of oil at frying temperature were similar for oils hydrogenated either with straight copper chromite or with mixed copper chromite-nickel catalysts. Blends containing 1, 2, and 3% linolenate made from unhydrogenated soybean salad oil and soybean oil hydrogenated to 0% linolenate with mixed copper chromite-nickel catalyst were similarly evaluated. Panel responses indicated a blend of 29% unhydrogenated soybean salad oil and 71% hydrogenated soybean oil scored slightly lower than the hydrogenated soybean oil.

Removal of copper from hydrogenated soybean oil

Hydrogenation with a copper-chromite catalyst at 170 C, 30 psi, increased the copper content of a refined, bleached soybean oil from 0.02 to as much as 3.8 ppm. Removing residual copper from soybean oil is essential to the successful use of copper catalysts for selective hydrogenation. Various methods were examined to remove this copper, including alkali refining, bleaching, acid washing, citric acid treatment and cation-exchange resin treatment. Properly conducted, each of the methods except alkali refining gives 95% or higher removal of copper introduced during hydrogenation. Ion exchange appears to be the most economical, but addition of about 0.01% citric acid during deodorization may be needed to inactivate traces of unremoved copper. Soybean oil hydrogenated with a copper-chromite catalyst, bleached or treated with an ion-exchange resin and deodorized with 0.01% citric acid added had low AOM peroxide values and acceptable flavor scores after eight days at 60 C which indicate that removal of residual copper from the oil should be adequate for the production of stable oils low in linolenic acid content.

Cyclic fatty acids: Removal of aromatic acids formed during hydrogenation

Monomeric fatty acids derived from the alkali treatment of linseed oil at temperatures above 200C contain cyclic (1,2-disubstituted cyclohexadiene) and straight-chain fatty acids. Hydrogenation converts cyclic to liquid, saturated cyclic acids that can be recovered in a pure state by crystallization. During hydrogenation (palladium catalyst) some of the unsaturated cyclic acids form aromatic fatty acids by loss of hydrogen and under some conditions are not subsequently hydrogenated. It was necessary to establish conditions for complete hydrogenation since color and oxidative stability at high temperature are inversely related to aromatic content. Previously, the preparation of cyclic acids free of aromatic acids was by hydrogenation in the presence of a high concentration of acetic acid. A further study of reaction variables established conditions to make saturated cyclic fatty acids free of aromatic without acetic acid. Factors favoring the elimination of aromatic acids include a high catalyst concentration, high temperature and pressure, good hydrogen dispersion in the liquid and good agitation.

Soybean soapstock utilization: Fatty acid adducts with ethylene and 1-butene

The relation of certain reaction variables to yield was investigated in the preparation of ethylene and 1-butene Diels-Alder adducts with alkali conjugated linoleic and linolenic acid soaps derived from soybean oil soapstock. Adduct yields generally increased with pressure at the 295 C reaction temperature. Maximum yields obtained with fatty acids derived from soapstock were ca. 80% of theory with ethylene and 40% of theory with 1-butene. Purification of adduct methyl esters by vacuum fractional distillation gave adducts with >95% purity. Ethylene adduct amides showed promise as antiblock agents for plastic film.

Hydrogenation of Soybean Oil with Copper-Chromium Catalyst: Preliminary Plant-Scale Observations

AbstractFour commercial hydrogenations were carried out on 20,000 1b batches of soybean oil with 0.25, 0.5, and 1% fresh copper-chromite catalyst and 1% used catalyst. Hydrogenations proceeded smoothly at catalyst levels of 0.5 and 1%, but the reaction was slow at a 0.25% concentration. Kinetic, selectivity ratio

Selective hydrolysis of soybean oil phosphatides

(K\frac{{Ln}}{{Lo}})