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 endosperm lipids of three Canadian wheats

Flour samples were prepared from intact and degermed kernels of Hard Red Spring, Soft White Spring, and Amber Durum wheats. The “free” (hexane soluble) and “bound” (hexane resistant, water-saturatedn-butanol extractable) lipids were extracted from the six flours and separated quantitatively by silicic acid column chromatography. Thin-layer chromatography (TLC) was used to monitor the column and to resolve the lipid classes into components. Gas-liquid chromatography (GLC) was used to obtain the fatty acid composition of the triglyceride, sterol ester, and phospholipid fractions, and also to determine the nature of the sterol components of the unesterified sterol and sterol ester classes. Similar patterns of lipid classes were shown by all three varieties; the differences were in the degree of dominance. In fatty acid composition some varietal differences were found but the greatest difference was between lipid classes. Contribution No. 5 of the Food Research Institute. Presented at the AOCS Meeting, Toronto, 1962.     

The distribution of lipids in the germ,endosperm, pericarp and tip cap of amylomaize,LG-11 hybrid maize and waxy maize

The quantitative distribution of 23 acyl lipid classes and unsaponifiable matter in kernels of amylomaize, LG-11 hybrid maize and waxy maize is described. LG-11 and waxy maize were normal (oil content) varieties, containing 4.9% and 5.1% lipid, respectively, while amylomaize (9.3% lipid) was a high oil variety. The distribution of kernel lipids was 76–83% in germ, 1–2% in pericarp, 1% in tip cap, 1–11% in starch, and 13–15% in aleurone plus the nonstarch fraction of the starchy endosperm. Germ contained 39–47% lipid, which was nostly triglyceride (TG), with some steryl esters (SE) and diglycerides (DG), and small amounts of glycolipids (GL) and phospholipids (PL). Aleurone lipids appeared to be TG with some free fatty acids (FFA) and SE. The other nonstarch lipids in starchy endosperm were FFA with very small amounts of SE, DG, GL and PL. The starches had a little surface lipid (FFA) and true (internal) starch lipid (FFA, lyso-PL) in quantities roughly related to amylose content (amylomaize =ca. 73% amylose, 1.0% lipid; LG-11=23% amylose, 0.7% lipid; waxy maize =<5% amylose, 0.2% lipid). Pericarp lipids (0.8–2.5%) were mainly unsaponifiable matter, the acyl lipids being TG, SE, DG and FFA. Tip cap lipids (2.5–2.9%) had more TG, GL and PL than pericarp lipids, but were otherwise similar. Pericarp lipids and endosperm nonstarch lipids appeared to have suffered extensive degradation at some time during kernel development or after harvesting, while lipids in starch, germ and tip cap were evidently unaffected. FFA and lyso-PL are regarded as normal components of maize starch (rather than degradation products) and may occur as amylose inclusion complexes.     

Kinetics of oil extraction from corn germ

This paper describes the effect of temperature and moisture content on the kinetics of oil extraction from corn germ flakes prepared by a dry degermination process. The experiments were carried out according to the factorial design 3². The moisture content in the extracted material was varied in the range 8%–12%, whereas the extraction temperature varied in the range 52.5°C–57.5°C. From the method of response surfaces, a functional dependence was established between the extraction rate, the moisture content in the material and the temperature of extraction. On the basis of this dependence, it was concluded that moisture content had a crucial effect on the rate of oil extraction. A decrease in moisture from 12% to 8% yielded a doubling of the extraction rate. On the other hand, temperature variations in the given range had no practical effect on the course of the extraction. Kinetics of oil extraction was determined according to the method developed in the Leningrad Institute of Oils and Fats (VNIIZh-method), modified to the extent described in the paper.     

Food applications of corn germ protein products

Many convenience foods such as meat analogs, breakfast foods, and baked goods use ingredients prepared from cereal grains and their processed products. Among the most important new cereal protein products, corn germ protein products appear to have the greatest potential food markets.     

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.     

Reactions of lipids in corn with ammonia

Ammonia has recently been employed in experimental tests for the treatment of corn to inactivate aflatoxin, to control molds, and as a preservative during ambient-air drying of freshly harvested high-moisture corn. When these various ammonia treatments are properly applied, no adverse effects have been found on any of the constituents of whole corn. However, in the work being reported when 0.1% or more ammonia was in contact with corn in the presence of air for more than a few days, irreversible changes occurred in the polyunsaturated lipids that were proportionate to the ammonia concentrations. The extent of the changes were dependent upon: (a) air-to-corn ratio, (b) ammonia concentration, (c) temperature, (d) corn moisture, and (e) time. The changes were characterized by a reduction in unsaturation of the lipid, by incorporation of nitrogen into the lipids, and by a consequent increase in lipid polarity. The change in polarity of these altered lipids rendered them unextractable with the usual fat solvents. Air (oxygen) and an initiating mechanism that occurs naturally in corn were required for the lipid-ammonia interaction to occur. This interaction involved only the polyunsaturated fatty acid moieties and formed a class of nitrogenous derivatives. Corn may be treated with ammonia for purposes of detoxification or preservation for long periods with no detectable adverse effects on the lipid composition, as long as headspace air is kept low during ammoniation. This may be accomplished in any of the following ways: (a) by ammonia ting the corn with a very limited headspace, (b) by ammoniating corn in a sealed bin and displacing the air in the headspace with ammonia gas, and (c) by replacing the headspace air with an inexpensive, inert gas such as nitrogen.     

Lipids in the germ,endosperm and pericarp of the developing maize kernel

Acyl lipids were quantified in the germ, endosperm and pericarp of LG-11 maize kernels at eight stages of development from 9 to 87 days after pollination (DAP). Changes in the lipids are discussed in relation to morphological events in the developing kernel. Storage lipids (triglyceride, steryl ester) and membrane lipids (diacylphospholipids) accumulated in germ until 52-76 DAP, then decreased slightly without formation of lipid degradation products, lated in endosperm until 36-42 DAP and then decreased. Maximum values for galactosyldiglycerides and diacylphospholipids (nonstarch lipids) were reached at 16-23 DAP, and all decreased to very low values at maturity. Loss of these functional (membrane) lipids during the period of endosperm cell filling is unexpected. Starch contained 82% of the lysophospholipids and 64% of the free fatty acids in endosperm at 76 DAP. Endosperm lysophospholipids increased until 76 DAP and then decreased slightly, while free fatty acids increased continuously mostly inside starch granules at all stages of development, and any possible decrease after 76 DAP was masked by acids formed by hydrolysis of aleurone and endosperm nonstarch lipids from 52 DAP. In DAP, and phospholipids decreased after 42 DAP. Loss of these lipids is associated with senescence of most pericarp tissue. Triglycerides and steryl esters accumulated steadily to maturity, while the main accumulation of unsaponifiables occurred after 52 DAP about the time of suberin formation.     

Evaluation of cookies enriched with corn germ and soy fiber

The objective of this study was to evaluate four cookie formulations which wheat flour was partially substituted by free-fat corn germ flour and/or soy fiber. Baking quality, protein, fat, ash, dietary fiber, hardness, color, Protein Efficiency Ratio PER and Apparent Digestibility in vivo were determined. A trained panel evaluated color, hardness and fracturability of cookies. Dietary fiber of cookies varied from 8.2 to 24.9% and protein from 11.3 to 12.7%. The source and amount of dietary fiber modified physical, sensory, and nutritional properties of cookies. Cookies formulated with 20% corn germ flour gave the highest PER, Digestibility Aparente in vivo, and acceptance by consumers. This study demonstrated the potential use of free-fat corn germ and soy fiber as functional ingredients.     

大豆脂肪氧合酶催化合成氢过氧化玉米胚芽油

研究了大豆脂肪氧合酶催化合成氢过氧化玉米胚芽油的反应。考察了溶剂种类、溶剂量、温度、底物浓度对氢过氧化玉米胚芽油得率的影响。较佳反应条件为：5℃下．当溶剂乙醇体积分数为4％,底物浓度100g／L,硼酸-硼砂缓冲液（pH9．0）,反应1．5h后氢过氧化玉米胚芽油得率为53．3％。     

Stereospecificity of linoleic acid hydroperoxide isomerase from corn germ

Linoleic acid hydroperoxide isomerase from corn germ inverted the stereoconfiguration of its substrate. 9-D(S)-Hydroperoxy-trans-10,cis-12-octadecadienoic acid was converted to 10-oxo-9-L(R)-hydroxy-cis-12-octadecenoic acid. Presumably, the H₂O solvent of OH⁻ acted as a nucleophile. In the presence of another nucleophile, linoleate, the 9-D(S)-hydroperoxide was transformed into 9-L(R)-linoleoyloxy-10-oxo-cis-12-octadecenoic acid. The substitution of nucleophiles from the incubation solution and the inversion of stereoconfiguration at carbon-9 are consistent with a bimolecular nucleophilic substitution (S_N2) mechanism. The 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.     

超临界二氧化碳流体萃取玉米胚芽油

用超临界ＣＯ２流体技术对玉米胚芽油的萃取进行了研究，考察了温度、压力对得油率的影响，初步探讨了分离器的温度、压力以及萃取原料对油品质量的影响。     

不同返粕量对玉米混合粉发酵乙醇的影响

本文以中粮生化能源(肇东)有限公司现有生产线上的玉米混合粉为原料,进行不同返粕量的发酵效果的初步研究,试验了不同返粕量的酒精(返粕量分别为10%、13%、15%、17%和20%)的发酵效果及其对DDG蛋白含量的影响。结果显示:返粕量为13%的成熟醪酒分、淀粉出酒率及蛋白含量最高。     

A comparison of commercial enzymes for the aqueous enzymatic extraction of corn oil from corn germ

An aqueous enzymatic method was developed to extract corn oil from corn germ. The basic steps in the method involved “churning” the corn germ with various enzymes and buffer for 4 h at 50°C, and an additional 16 h at 65°C, followed by centrifugation and removal of the oil layer from the surface. No hexane or other organic solvents are used in this process. By using oven-dried corn germ samples (6 g) from a commercial corn wet mill, corn oil yields of about 80% were achieved using three different commercial cellulases. A fourfold scale-up of the method (to 24 g of germ) resulted in oil yields of about 90%. Nine other commercial enzymes were evaluated and resulted in significant but lower oil yields. In the absence of enzymes, oil yields of 27 to 37% were achieved. The chemical compositions of hexane-extracted vs. aqueous enzymatic-extracted corn oils were very similar.     

Quality of corn germ oil obtained by aqueous enzymatic extraction

Aqueous enzymatic extraction of corn germ oil was investigated. By applying hydrothermal pretreatment of corn germ, it was possible to inactivate native enzymes present in the germ and to loosen its structure. The corn was then ground and treated with enzymes. After the oil had been released by the enzyme reaction, it was separated by centrifugation. The quality of oil obtained by enzymatic extraction (Pectinex Ultra SP-L at 37°C, pH 5.2, for 6 h) was good. The oil had 1.5% free fatty acids; a total content of oxidation product value of 8.1; light yellow color (AOCS photometric color, 12.7; dominant wavelength λ_D=575 nm); 0.022% phosphatides; 1350 mg/kg total tocopherol; and an oxidative stability value (Rancimat test, 100°C) of 14.6 h.     

Fatty acid compositions of lipids from corn and grain sorghum kernels

Summary Characteristics and fatty acid compositions of the lipid components of the main fractions (germ, starch, gluten, and fiber) obtained in the wet milling of corn and grain sorghum kernels have been determined. The various lipids exhibited differences in chemical characteristics and fatty acid composition. These differences were found to be similar in both grains. Germ fats were the most unsaturated, contained the least free fatty acids and the least unsaponifiable matter. Starch fats were 70 to 90% free fatty acids and contained large amounts of palmitic acid. Gluten and fiber fats contained up to 32% unsaponifiables and about 20% free fatty acids.     

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.     

Our experiences in processing maize (corn) germ oil

This paper discusses the properties and composition of corn oil. Influences of processing steps on oil quality are described, along with alkali and physical refining, degumming, bleaching, dewaxing, deacification-decodorization. A new method for wet degumming-bleaching and deacidification-deodorization is presented. Flowsheets and other data are given for a new 150 metric tons per day of corn oil plant.     

Evaluation of corn germ protein as an extender in plywood adhesive

This study was conducted to evaluate the potential of wet-milled corn germ protein as an extender in plywood adhesive. Partially defatted dried corn germ from wet-milling, containing 2.1% (dry basis, db) crude oil and 24.7% (db) crude protein, was ground to 40-mesh particle size to produce the meal. The predominant water- and saline-soluble proteins were extracted from the corn germ meal (CGM) by using 0.1?M NaCl as solvent in a method that used homogenization, centrifugation, dialysis, and freeze-drying. The recovered freeze-dried protein extract (FDPE) was substituted (on protein content basis) for wheat flour in the standard adhesive mix for sprayline coaters. Adhesive containing CGM was also prepared in the same manner. Mixing and adhesion properties of the corn germ-based adhesives were compared with those of the industry standard adhesive. The adhesive containing FDPE showed dispersibility and mixing behaviors, as well as viscosity values that were almost identical to those of the industry standard and superior to those of CGM adhesive. The mean wet tensile strength of the adhesive containing FDPE was notably greater (1.71?MPa) than that of CGM-based adhesive (1.34?MPa) and wheat-based standard adhesive (1.38?MPa), which indicated stronger bonding. The results demonstrated that corn germ protein has the potential to be an alternative protein extender in plywood adhesives for sprayline coaters.