Fatty acid composition of corn endosperm and germ oils as influenced by different extraction procedures

Gas liquid chromatography was used to determine fatty acid composition of oil obtained from corn (Zea mays L.) inbred lines by different extraction procedures. Kernels were separated into endosperm and germ fractions for nine inbreds which had a considerable range in fatty acid composition of oil. Oil obtained from the endosperm by different extraction procedures was significantly different in composition for all fatty acids. Oil obtained from the germ by different extraction procedures was similar in fatty acid composition. The differences in response of endosperm and germ oils to extraction procedures were attributed to the type of lipid found in each fraction. It was concluded that choice of extraction procedures was of little importance in studies of oil from the corn germ, but that specific extraction procedures must be recognized as a factor when studying oil composition of the endosperm. Approved as Journal Series Paper No. 696, University of Georgia, College of Agriculture Experiment Stations.     

The lipids of corn germ and endosperm

Mature kernels of an inbred corn were hand dissected into germ and endosperm fractions. Among various solvents tested, boiling, water-saturatedn-butanol extracted the most lipid from endosperm, and it was used as t h e extracting solvent for both germ and endosperm. The germ contained 78% of the total lipids and the endosperm 17%. The most striking differences in the fatty acid compositions of the triglycerides and polar lipids were higher levels of stearic and linolenic acids in the endosperm lipids. Although precautions were taken during extraction to inactivate lipases, immediately after harvest the free fatty acid level of the total lipids of the whole kernel was 6.5%. Ninety-five percent of the free fatty acids was in the endosperm fraction where the free fatty acids made up 36.5% of the total lipids. In germ, free fatty acids represented only 0.6% of the total lipids. The individual phospholipid and glycolipid classes of the endosperm and germ lipids were similar except for high levels of lyso compounds in the endosperm lipids. The higher levels of linolenic acid, free fatty acids and lyso lipids in endosperm may affect the keeping quality of the corn grain and of fractions milled from the endosperm. Presented at the AOCS meeting, St. Louis, May 1978.     

Distribution of tocopherols within the corn kernel

The concentration of tocols and tocotrienols in the germ, endosperm and pericarp of the corn kernel was determined after hand dissection of four dent corn hybrids—normal, early maturing, high oil and high lysine (opaque-2). Among these hybrids the germ fraction contained 70–86% and the endosperm fraction contained 27–115 of the tocopherols extracted from the whole grain. The endosperm fractions contain all of the measurable tocotrienols occurring in whole corn. In the four hybrids analyzed, the germ fraction contained 94–96% of thea-tocopherol extracted from the whole grain. Concentration ofa-tocopherol was the highest in the germ fraction of the opaque-2 hybrid.     

Tocol levels in milling fractions of some cereal grains and soybean

Tocol levels in the milling fractions of rice, barley, corn, wheat, and soybeans were analyzed by HPLC with a fluorescence detector. Among all milling fractions tested in this study, rice germ had the highest total tocol levels. In the four milling fractions of barley, except pearling flour, all eight tocol isomers were detected, and they were more uniformly distributed than in any other cereal grains measured in this study. The total tocol and α-tocopherol levels of wheat germ were significantly (P<0.05) higher than the other wheat milling fractions. A significantly (P<0.05) higher proportion of γ-tocopherol was obtained from corn germ (71.5%) and endosperm (50.3%) than from corn hulls. Only four tocol isomers (α-, β-, γ-, and δ-tocopherol) were detected in soybean milling fractions; no tocotrienol isomers were detected. The δ-tocopherol level of soybean endosperm, although minor, was significantly higher than those in milling fractions of other cereal grains in this study.     

The composition of corn oil obtained by the alcohol extraction of ground corn

All commercial corn oil is obtained by the hexane extraction of corn germ. The chemical composition of commercial corn oil has been well characterized. This study was under-taken to quantitatively evaluate the lipid composition of corn oil obtained by the ethanol extraction of ground, whole corn kernels. When corn oil was obtained by extracting ground corn kernels (ground corn) with polar or nonpolar solvents, the resulting corn oil contained much higher levels of hydroxycinnamate steryl esters (≈0.3%) than those found in commercial hexane-extracted corn (germ) oil (≈0.02%). The levels of valuable tocopherols and tocotrienols were also significantly higher in kernel oil than in traditional corn germ oil. We previously reported that when corn oil was obtained by extracting corn kernels with polar solvents, the oil contained two polyamine conjugates, diferuloylputrescine and p-coumaroyl feruloylputrescine. In the current study, when ground corn was extracted with ethanol, the resulting corn oil contained about 0.5% diferuloylputrescine and about 0.2% p-coumaroyl feruloylputrescine. This is the first study to quantify these unique compounds in corn oil extracted by new techniques. This compositional information is important because this new oil is being considered for human food use.     

Foam Separation of Oil from Enzymatically Treated Wet-Milled Corn Germ Dispersions

More than 9 billion gallons of ethanol were produced in 2008, mostly from dry grind corn fermentation plants. These plants are a potential source of substantial amounts of corn oil, if an economical method of separating it can be developed. In this work, oil was separated from corn germ by aqueous enzymatic extraction (AEE). Batches of wet-milled corn germ in water were preheated in a pressure cooker, ground in a colloid mill, and churned in a vertical column/mixing vessel system, after the addition of enzyme. Nitrogen gas was then bubbled through the column removing an overflowing foam fraction which was subsequently centrifuged to separate free oil. Using a newly commercialized enzyme complex it was found that 80% of the oil could be recovered using a w/w ratio of enzyme solution to germ of 1:80. The low dose and low price of the enzyme complex leads to a cost estimate of AEE of corn oil from germ, similar to the wet-milled germ extracted, cost competitive with expelled oil (with the separation and drying of the foam protein), and feasible for commercialization in a dry grind plant retrofitted to separate germ.     

以硝酸处理西藏硼砂矿制备硼酸及硝酸钠的研究

以硼酸母液浸溶西藏硼砂矿,对所得硼砂溶液进行酸化,生成硼酸和硝酸钠;控制反应浓度和其他相关工艺条件,使硼酸和硝酸钠同时结晶,再利用二者相对密度的不同,采用重力分离法实现了硼酸与硝酸钠的有效分离。实验证明：硼和钠收率分别达到92.0%和91.5%,产品质量符合国家标准。工艺过程不对硼酸母液进行蒸发。     

Studies on the Separation of Cadmium from Solutions by Foam Separation. I. Foam Separation of Cadmium Cations

Abstract

The efficiency of Cd²⁺ foam separation with sodium lauryl sulfate and sodium laurate from sodium sulfate and sodium nitrate solution was tested. Foam fractionation of Cd²⁺ with lauryl sulfate in the form of a hydrated ion pair 2C₁₂H₂₅SO₄, Cd²⁺ is ineffective because of a low recovery and high hydration of the foam. But ion flotation of Cd²⁺ as a low-solubility salt (C₁₂H₂₅COO)₂Cd is highly effective. The presence of electrolyte in the solution has a negative influence on Cd²⁺ foam fractionation with lauryl sulfate because of an increase of inert salt concentration which causes competition for the collector between colligend Cd²⁺ and the added Na⁺ ions, and because of simultaneous increase in the thickness of water sheaths around the gas bubbles. In the case of ion flotation with sodium laurate, the presence of electrolyte improves Cd²⁺ recovery and decreases the thickness of the water sheaths around the gas bubbles. The interpretation of the results is based on the exchange of the collector counterions as well as on the properties of the reaction products.     

Interfacial tension and density measurement of the system corn germ oil – carbon dioxide at low temperatures

In this article, the physical properties of corn germ oil at high pressures of up to 30 MPa and at low temperatures from ?10 °C to 22 °C are presented. We measured the interfacial tension of the commercially available corn germ oil Mazola® and of unrefined corn germ oil in contact with carbon dioxide, as well as the density of carbon dioxide‐saturated corn germ oil. The interfacial tension of refined and unrefined corn germ oil in contact with gaseous carbon dioxide at temperatures above ?10 °C depends on time, while at higher pressures the equilibrium value of the interfacial tension is reached immediately after the formation of the drops or bubbles. The interfacial tension of unrefined corn germ oil in contact with carbon dioxide is higher than the interfacial tension of refined corn germ oil. This fact is explained in this article. The interfacial tension of refined and of unrefined corn germ oil in contact with carbon dioxide decrease with rising pressure and can be described as a function of the carbon dioxide density for the examined temperature range. The density of carbon dioxide‐saturated corn germ oil is linearly dependent on pressure, with a high slope if carbon dioxide is gaseous and with a low slope if carbon dioxide is liquid.     

Laboratory and pilot solvent extraction of extruded high-oil corn

Oil extraction of flakes and extrudates of high-oil (HO) corn was studied, using hexane as solvent. HO corn contained 19.5% oil, 70% of which was located in the germ. Microstructures of starchy endosperm and germ were analyzed by scanning electron and light microscopy. Conventionally extruded samples extracted faster and to a lower residual oil content than flakes and steam-injected extrudates. Ultrastructural disruption and cooking of conventionally extruded material was adequate to free the oil from the spherosomes and produce a porous pellet with a high proportion of “surface oil.” Encapsulation of the oil within a gelatinized starch matrix made it partly unavailable in steam-injected extrudate samples. Data presented for laboratory and pilot plant runs demonstrate that conventional extrusion is a promising pretreatment for solvent extraction of high-oil, starchy materials.     

Composition and economic comparison of germ fractions from modified corn processing technologies

Several new processes for milling corn have been developed recently specifically to isolate germ as a value-added co-product and improve the profitability of dry-grind ethanol production. The present work used modified and conventional corn milling technologies to recover germ fractions from corn kernels using either wet or dry separation processes. This study determined the quality, composition, and yield differences among the corn germ produced and compared these properties with those of the conventional wet- and dry-milled germ. A method for calculating the estimated market value for germ produced by the alternative processing methods is given. There were significant differences in the oil, protein, starch, and ash compositions and in the estimated market values among germ fractions produced by the alternative milling processes. The different germ fractions produced (including the traditional wet-and dry-milled) were found to contain 18–41% oil, 13–21% protein, and 6–21% starch, depending on the milling process used. The estimated value of germ from these processes varied from as low as $0.058/lb ($0.128/kg) to a maximum of $0.114/lb ($0.251/kg), showing that the specific process used to produce the germ will have the major impact on the overall economics of the ethanol process.     

Effect of controlled temperature environments on oil content and on fatty acid composition of corn oil

Total oil content and fatty acid composition of germ and endosperm oil were determined on grain from three inbred lines and one variety of corn (Zea mays L.) grown in four phytotron environments and one standard greenhouse environment during seed maturation. Pronounced differences occurred with reversals for relative percentages of oleic and linoleic acids of germ oil for one inbred line and for the variety. Comparative trends were generally less pronounced for two of the inbred lines. Differences among environments were less evident for palmitic, stearic, and linolenic acids of germ oil and for the fatty acids of the endosperm oil. Total oil was lowest for two inbred lines and the variety grown in the high temperature environment (30 C day/26 C night). The magnitude of temperature effects on oil content and oil composition varied among the four corn genotypes. Journal article 3961 of the North Carolina State University Agricultural Experiment Station. ARS, USDA.     

Carotenoids and tocols of corn grain determined by HPLC

A high performance liquid chromatographic (HPLC) procedure has been developed that permits determinationof carotenoids and tocols in the same sample preparation of corn grain. For 15 inbreds, the total carotenoids ranged from 16 to 77 μg/g dry wt and the total tocols from 30 to 128 μg/g dry wt. For four inbreds, total carotenoids were concentrated in the horny endosperm (83±2%) and total tocols in the germ (77±6%). After six months storage at room temperature, the mean loss of total carotenoids for four inbreds was 42±4%, while the tocols had a mean loss of 5%. Presented at the AOCS meeting in Honolulu, HI in May 1986.     

The influence of moisture content and cooking on the screw pressing and prepressing of corn oil from corn germ

Samples of corn germ were obtained from a commercial corn wet mill (factory dried to about 3% moisture) and a commerical corn dry mill (undried, produced in the mill with about 13% moisture). The germ samples (200 g each) were cooked for various times in either a conventional oven at 180°C or a microwave oven at 1500 W. Bench-scale single screw pressing was then performed. With the dry milled corn germ, no oil was obtained from the uncooked germ. A maximal yield of about 5% oil [26% of total oil recovery (TOR), relative to hexane extraction] was obtained by cooking the dry-milled germ for 6.5 min in a conventional oven at 180°C before pressing. A maximal yield of about 7% oil (37% TOR) was obtained by cooking the dry-milled germ for 4.5 min in a microwave oven at 1500 W before pressing. With the wet-milled germ, yields of about 7% oil (18% TOR) were obtained with the uncooked germ and yields increased to a maximum of about 22% oil (56% TOR) by cooking in a conventional oven at 180°C for 5 min or a maximum of about 17% oil (44% TOR) by cooking for 4 min in a microwave oven at 1500 W. These results indicate that microwave and conventional oven cooking are both effective pretreatments before pressing. Microwave preheating resulted in higher oil yields with dry-milled germ, and conventional oven pretreatment resulted in higher oil yields with factory-dried wet-milled corn germ.     

The combined effect of lead ion and sodium silicate in the flotation separation of scheelite from calcite

Flotation separation of scheelite from calcite is difficult because of the existence of the same cation in the minerals and similar physicochemical characteristics. Many studies have been performed to determine the selective depressants for calcite, but the separation of scheelite from calcite is still a big problem. In this article, the flotation separation of scheelite from calcite has been studied by flotation tests. The results show that benzohydroxamic acid has weak collecting ability to both scheelite and calcite. Lead ions can activate the flotation of scheelite and calcite, but the flotation separation of scheelite from calcite can’t be realized. The depressant saline sodium silicate (mixture of sodium silicate and lead ions) has selective depression effect on calcite and the optimum ratio of sodium silicate to lead ions is 3:1. The use of saline sodium silicate as a depressant can achieve the flotation separation of scheelite from calcite. The zeta potential results and adsorption studies showed that the pre-adsorption of saline sodium silicate only interferes with the adsorption of benzohydroxamic acid on calcite surface; this is the main reason for the selective depression effect of saline sodium silicate on calcite.     

内循环式泡沫浮选塔处理含铬废水

采用自制的内循环泡沫浮选塔处理含铬废水,考察pH值、Fe(NO3)3浓度、十二烷基硫酸钠(SDS)浓度、气体流量、分离时间等因素对分离效率的影响,并与常规泡沫塔比较. 结果表明,在12~35 min内,内循环式浮选塔分离效率更高,35 min时塔内铬离子浓度为0.6 mg/L,常规泡沫塔内铬离子浓度为10 mg/L. 内循环浮选塔最佳分离工艺条件为,对初始铬浓度为20 mg/L的废水,在pH 5.5、SDS 100 mg/L、Fe(NO3)3 60 mg/L、气体流量800 mL/min条件下处理效果最好,泡沫夹带率约为10%,Cr(III)脱除率可达97%以上.     

Antioxidant Activity of Oat Malt Extracts in Accelerated Corn Oil Oxidation

Oat cultivar AC Vermont was malted to concentrate antioxidants, milled to fractionate only the endosperm portion and extracted with methanol to isolate the crude antioxidants. The oat malt antioxidant fraction was assessed as a natural antioxidant based upon enhancing the stability of corn oil against oxidation and compared to the synthetic antioxidant butylated hydroxytoluene (BHT). The induction time (time required for the formation of 10 meq hydroperoxide per kilogram corn oil thermally oxidized) was used to measure antioxidant activity of oat antioxidant or BHT. The protection factor achieved by crude oat malt antioxidant extract concentrate at 0.26% (2,600 μg/g) was comparable to BHT (75 μg/g). The antioxidant activity of the oat and barley malt extract concentrates was not significantly different. However, the extract concentrate of oat malt had 44% less color compared to that of barley malt at equal concentrations showing its potential as a natural food antioxidant.     

贵州省煤系硫铁矿石选矿试验

贵州煤系硫铁矿石矿物组分简单、易选，用单一的重选法和浮选法都能获得较好的分选指标，尤以重浮联合流程分选为佳。采用中矿再磨再选流程可以获得含硫45％的硫精矿．制酸后的烧渣含铁大于60％，可炼铁综合回收铁资源。     

超临界CO2萃取玉米胚芽油工艺的研究

本文研究采用超临界ＣＯ２从玉米胚芽中萃取油品的工艺条件，运用响应面法探讨了萃取压力、萃取温度和物料粒径在油品产率为９０％时对ＣＯ２消耗量的影响，确定了最佳工艺参数，分析比较了超临界ＣＯ２萃取、正己烷索氏萃取和压榨三种方法对油品质量和脂肪酸组成的影响。     

High performance liquid chromatography of the tocols in corn grain

A sensitive and selective method was developed for analyzing the tocol isomers in corn grain by high performance liquid chromatography (HPLC) with fluorescence detection. The relative proportions and the total amounts of the tocol isomers (α-tocopherol, α-tocotrienol, γ-tocopherol and γ-tocortrienol) varied greatly among the 15 corn inbreds that were examined. Although γ-tocopherol has traditionally been considered to be the predominant vitamin E isomer in corn, inbreds with equal or higher levels of α-tocopherol have been discovered. No tocotrienols were found in corn germ oil, only α-and γ-tocopherols. Analysis of the tocopherols of the germ oils of inbreds and their reciprocal crosses indicated that the proportions of the α- and γ-isomers and the total amount of the tocopherols are heritable. Presented at the 74th AOCS annual meeting, Chicago, 1983.