Effect of heat pretreatment on the yield and composition of oil extracted from corn fiber.

Previously, hexane extraction of corn fiber was reported to produce a unique and potentially valuable oil that contained high levels of several phytosterols (which have been noted for their cholesterol-lowering properties). Current studies revealed that heat treatment (over the range of 100-175 degrees C) of corn fiber in either a convection oven or a vacuum oven caused only a modest reduction in the levels of the phytosterol components. However, these same heat pretreatments caused a considerable increase (up to 10-fold) in the levels (increasing from 0.34 wt % to a maximum of 3.64 wt % gamma-tocopherol in the oil) and yields (increasing from 5.4 mg of gamma-tocopherol/100 g of corn fiber to a maximum of 52.1 mg of gamma-tocopherol/100 g of corn fiber) of gamma-tocopherol in corn fiber oil. The main differences between the convection oven and vacuum oven pretreatments were associated with the disappearance of free fatty acids and free phytosterols at the higher temperature pretreatments in the vacuum oven, probably due to the lower boiling points of these lipids. Microwave pretreatment was also effective but caused a much smaller increase in the levels of gamma-tocopherol.     

Comparison of oil and phytosterol levels in germplasm accessions of corn, teosinte, and Job's tears

Seeds of 49 accessions of corn (Zea mays ssp. mays), 9 accessions of teosinte (Zea species that are thought to be ancestors and probable progenitors to corn), and 3 accessions of Job's tears (Coix lacryma), obtained from a germplasm repository, were ground and extracted with hexane. Whole kernel oil yields and levels of four phytonutrients (free phytosterols, fatty acyl phytosterol esters, ferulate phytosterol esters, and gamma-tocopherol) in the oils were measured. Among the seeds tested, oil yields ranged from 2.19 to 4.83 wt %, the levels of ferulate phytosterol esters in the oil ranged from 0.047 to 0.839 wt %, the levels of free phytosterols in the oil ranged from 0.54 to 1.28 wt %, the levels of phytosterol fatty acyl esters in the oil ranged from 0.76 to 3.09 wt %, the levels of total phytosterols in the oil ranged from 1.40 to 4.38 wt %, and the levels of gamma-tocopherol in the oil ranged from 0.023 to 0.127 wt %. In general, higher levels of all three phytosterol classes were observed in seed oils from accessions of Zea mays ssp. mays than in seed oils from accessions of the other taxonomic groups. The highest levels of gamma-tocopherol were observed in teosinte accessions.     

Phytosterol and tocopherol components in extracts of corn distiller's dried grain

As the ethanol industry continues to grow, it will become very important to develop value-added markets for its coproducts in order for the industry to remain profitable. Corn distiller's dried grain (DDG) is a major coproduct of ethanol fermentation from corn processed by dry-milling and is primarily sold as livestock feed. The objective of this research was to determine if valuable phytochemicals found in corn oil and corn fiber oil, such as phytosterols and their saturated equivalents, phytostanols, ferulate phytosterol esters (FPE), tocopherols, and tocotrienols, are retained in DDG. Hexane and supercritical carbon dioxide (CO2) extracts of DDG were similar in their concentrations of total phytosterols (15.8-17.3 mg/g of extract), FPE (3.75-3.99 mg/g of extract), and tocols (1.7-1.8 mg/g of extract). Ethanol extracts were slightly lower in concentration of phytosterols (8.9-11.4 mg/g of extract), FPE (1.62-1.98 mg/g of extract), and tocols (0.73-0.76 mg/g of extract).     

Phenolic acids, lipids, and proteins associated with purified corn fiber arabinoxylans

Corn fiber gum (CFG) is a hemicellulose (arabinoxylan)-enriched fraction obtained by the extraction of corn bran/fiber using a proprietary alkaline hydrogen peroxide process. When purified CFG prepared by this process was hydrolyzed with more concentrated base (1.5 N methanolic KOH at 70 degrees C for 1 hour), considerable amounts of hydroxycinnamic acids (up to 0.015% of mainly ferulic acid) and lipids (up to 0.43%) were released. The released phenolic acids and lipids were identified and quantified using high-performance liquid chromatography (HPLC) with detection by both UV and evaporative light-scattering detection (ELSD). During the wet milling of corn, two types of corn fiber are produced: coarse fiber, which is primarily from pericarp, and fine fiber, which is from the endosperm. The total phenolic acid content in CFGs purified from coarse corn fiber (pericarp fiber) is comparatively higher than that purified from fine corn fiber (endosperm fiber). It was also determined that the purified CFG samples contained significant amounts of strongly associated proteins, from 2 to 5% by weight. The presence of these phenolic acids, lipids, and proteins strongly associated or bound to CFG may contribute to its excellent ability to emulsify oil-in-water emulsions.     

基于机器视觉的玉米种粒定向定位摆放装置研制

为实现玉米定向、定位播种,基于图像处理技术研制了一种玉米种粒定向定位摆放装置。在介绍装置的组成和工作原理的基础上,设计了关键部件的结构,通过试验分析和理论计算,确定了关键部件的尺寸参数和安装方位,测试了导向定位管的定位精度,分析了凹型定位槽连续有效作业的条件,并结合作业精度要求,设计了控制方式并设置了控制参数。同时结合金博士郑单958种粒样本的特点,改进了合格种粒胚芽正反面和尖端朝向的图像检测算法。试验结果表明,胚芽正反面检测准确率为98%,尖端朝向检测偏差小于8°,凹槽定位准确率为97%,定位吸取准确率为94%,定位摆放准确率为99%,摆放后角度偏差不大于10°,满足设计要求。该研究可为实现种粒的定向包装以及后续的定向播种提供参考。     

Protein distribution in commercial wet- and dry-milled corn germ

To identify high-valued coproducts from commercially processed corn germ, it was necessary to determine the effect of processing conditions on corn germ proteins. We found that significantly less protein was extracted from commercial wet-milled as compared to dry-milled corn germ using Tris, sodium dodecyl sulfate (SDS) buffer containing 14 mM 2-mercaptoethanol at 100 degrees C for 10 min. SDS-polyacrylamide gel electrophoresis (PAGE) revealed a number of proteins with molecular masses ranging from approximately 10 to 66 kDa for the dry-milled corn germ as compared to only a few significant protein bands centered around 23 kDa in the wet-milled corn germ. The protein content of the wet- and dry-milled corn germ was approximately the same; however, nonprotein nitrogen values were significantly greater for the wet-milled than for the dry-milled germ. The distribution of fractionated germ protein freshly excised from the embryo of yellow dent corn kernels was more similar to that of dry-milled than wet-milled corn. SDS-PAGE of laboratory preparations of wet-milled corn germ more closely resembled commercial dry- than wet-milled corn germ, which could be attributed to limited microbial growth during steeping in the laboratory preparations.     

Effect of Alternative Milling Techniques on the Yield and Composition of Corn Germ Oil and Corn Fiber Oil

The effects of alternative corn wet‐milling (intermittent milling and dynamic steeping (IMDS), gaseous SO₂ and alkali wet‐milling) and dry grind ethanol (quick germ and quick fiber with chemicals) production technologies were evaluated on the yield and phytosterol composition (ferulate phytosterol esters, free phytosterols, and fatty acyl phytosterol esters) of corn germ and fiber oil and compared with the conventional wet‐milling process. Small but statistically significant effects were observed on the yield and composition of corn germ and fiber oil with these alternative milling technologies. The results showed that the germ and fiber fractions from two of the alternative wet‐milling technologies (the gaseous SO₂ and the IMDS) had, for almost all of the individual phytosterol compounds, either comparable or signficantly higher yields compared with the conventional wet‐milling process. Also, both of the modified dry grind ethanol processes (the quick germ and quick fiber) with chemicals (SO₂ and lactic acid) can be used as a new source of corn germ and fiber and can produce oils with high yields of phytosterols. The alkali wet‐milling process showed significantly lower yields of phytosterols compounds in germ but showed significantly higher yield of free phytosterols, fatty acyl phytosterol esters and total phytosterols in the fiber fraction.     

利用近红外光谱测定玉米非淀粉组分中纤维素及半纤维素含量

玉米非淀粉组分是可再生的生物质资源,为实现玉米皮渣中纤维素及半纤维含量的快速检测,该研究以偏最小二乘法(PLS)建立数学模型,探讨一阶导数及二阶导数平滑等预处理对建模的影响,建立玉米皮渣中纤维素及半纤维素近红外分析模型.研究结果表明,纤维素模型的定标集和验证集相关系数为0.9806和0.9799,定标集标准偏差(SEE...     

Quick Fiber Process: Effect of Mash Temperature,Dry Solids,and Residual Germ on Fiber Yield and Purity

Preliminary calculations showed that recovery of fiber before fermentation in the dry grind ethanol facilities known as the Quick Fiber process increases fermenter capacity and reduces ethanol production cost by as much as 4 ¢/gal. The objective of the current research was to evaluate the effect of mash temperature, dry solids, and residual germ on fiber yield and purity when using the quick fiber process. Fiber was recovered by flotation and skimming, while maintaining a specified temperature, dry solids, and residual germ in the mash. Varying temperature and dry solids in the mash resulted in a statistically significant effect on the fiber yield, neutral detergent fiber (NDF) content, and weight of NDF/100 g of dry corn. Varying residual germ in the mash resulted in statistically significant differences for NDF through dilution and the weight of NDF/100 g of dry corn. The highest fiber yield was 10.9% at 45°C, 23% dry solids, and 15% residual germ; the highest NDF was 50.9% at 30°C, 21% dry solids, and 0% residual germ. The highest weight of NDF/100 g of dry corn was observed at 45°C, 23% dry solids, and 0% residual germ.     

Angiotensin I converting enzyme-inhibitory peptides from commercial wet- and dry-milled corn germ

Bioprocesses were developed to enhance the value of proteins from deoiled corn germ. Proteins were hydrolyzed with trypsin, thermolysin, GC 106, or Flavourzyme to generate the bioactive peptide sequences. At an enzyme to substrate ratio of 1:100, protein hydrolysis of wet-milled germ was greatest using thermolysin followed by trypsin, GC 106, and Flavourzyme. For the dry-milled corn germ, protein hydrolysis was greatest for GC 106 and least for Flavourzyme. Electrophoretic patterns indicated that the hydrolysis conditions used were adequate for generating low molecular weight peptides for both germs. Unhydrolyzed dry- and wet-milled corn germ did not appear to contain angiotensin I converting enzyme (ACE)-inhibitory peptides. After hydrolysis with trypsin, thermolysin, and GC 106 but not Flavourzyme, ACE inhibition was observed. ACE inhibition was greatest for the GC 106 hydrolysate for both wet- and dry-milled corn germ. Denaturing the protein with urea before hydrolysis, in general, increased the amount of ACE-inhibitory peptides found in the hydrolysate. Membrane fractionations of both the wet- and dry-milled hydrolysates indicated that most of the ACE-inhibitory peptides were in the <1 kDa fraction. Examination of the control total protein extracts (before treatment with proteases) from wet- and dry-milled germ revealed that neither had ACE-inhibitory properties. However, when both total corn germ control protein extracts were fractionated, the <1 kDa fraction of wet-milled corn germ proteins exhibited ACE inhibition, whereas the comparable low molecular weight fraction from dry-milled corn germ did not.     

乙醇水溶液提取玉米胚芽油的工艺优化

为了解决水酶法提取玉米胚芽油生产成本高、提取时间长的缺点,该文采用乙醇水溶液作为提取剂提取玉米胚芽油。通过对粒径、料液比、温度、乙醇体积分数、p H值和时间等条件对油在油相、水相和渣相中分布的研究发现,物料粒径和乙醇体积分数对提高清油得率具有显著(P0.05)的影响,而提取时间对清油得率的影响最小(P0.05)。在单因素试验的基础上通过正交试验,得出乙醇水溶液提取玉米胚芽油的最佳工艺参数为:物料细粉4次(此时粒径为49.18μm)、料液比1∶7 g/m L、温度70℃、乙醇体积分数30%、p H值9.0、提取时间2 h。在该条件下,清油的得率为94.05%±0.32%,水相含油量为3.49%±0.77%,渣相含油量为2.55%±0.82%。分析乙醇水溶液提取的玉米胚芽毛油酸价、过氧化值和含水率等指标发现,该毛油的质量优于国标规定的玉米原油,并且和压榨一级成品油指标接近,只需要经过简单精炼就可以达到食用油要求。研究结果为乙醇水溶液工业化生产玉米胚芽油提供参考。     

Effect of Various Acids and Sulfites in Steep Solution on Yields and Composition of Corn Fiber and Corn Fiber Oil

The addition of six acids (organic and inorganic) and four sulfite compounds (including gaseous SO₂) during the conventional corn wet‐milling steeping process of two yellow dent corn hybrids were evaluated for the effect on corn fiber yield, corn fiber oil yield, and the composition of three phytosterol compounds (ferulate phytosterol esters [FPE], free phytosterols [St], and phytosterol fatty acyl esters [St:E]) in the corn fiber oil. No significant effect of different sulfite compounds and acids were observed on corn fiber yields. However, a significant effect was observed on corn fiber oil yield and the composition of corn fiber oil for phytosterol compounds. Three of the sulfite compounds (including gaseous SO₂) caused very little effect on the levels of phytosterol compounds compared with the control sample (corn steeped with sodium metabisulfite and lactic acid). However, for one hybrid, ammonium sulfite gave a significantly higher yield of FPE and St:E and had no effect on the yield of St. For the other hybrid, it gave a significantly higher yield of FPE and had no effect on the yield of St and St:E compared with the control sample. This indicates that the effect of these sulfite compounds on yields of these phytosterol compounds in corn fiber oil is probably hybrid‐dependent. No significant effect of acids was observed on corn fiber yields, but significant effects were observed on corn fiber oil yields and yields of phytosterol compounds in the corn fiber oil. The effect also seems to be hybrid‐dependent because different acids affected the two hybrids differently. Overall, it seems that weak acids have a positive effect on increasing the individual phytosterol compounds in the corn fiber. When comparing the effect of experimental acids and sulfites on the two hybrids, acids have a more positive effect than sulfites in increasing the yield of phytosterol compounds in corn fiber oil.     

分层破胚剥皮玉米不同部位营养成分富集特征

为明确玉米籽粒营养成分的分布差异及不同部位富集特征,应用快速缓苏、微量着水半湿法分层破胚剥皮技术,结合靶向代谢组学方法,对郑单958玉米不同部位的营养成分及基础代谢物质进行分析与比较。结果表明玉米籽粒不同部位的淀粉、脂肪、矿物元素和膳食纤维等营养物质含量存在显著差异（P<0.05）。该研究中的玉米内皮层可能主要由种皮、糊粉层及部分外胚乳构成,该部位营养成分的种类及含量均较为丰富,其中水溶性膳食纤维含量显著高于其他部位（P<0.05）,可作为玉米水溶性膳食纤维的提取分离来源。K、P和Mg元素是玉米中含量最高的矿物元素,主要存在于胚芽中,Fe、Zn、Mn和Cu元素在胚芽和玉米皮层中均有较多分布,精制加工会导致这些矿物元素的损失。玉米胚芽中水解氨基酸种类较其他部位丰富且含量较高（P<0.05）,甜味氨基酸占总游离氨基酸含量的24.49%,高于玉米皮层部位、显著高于胚乳部位。研究结果为玉米营养健康食品的创制、玉米精深加工及相关专用装备的研发提供参考。     

Ethanol Production from Modified and Conventional Dry‐Grind Processes Using Different Corn Types

Different corn types were used to compare ethanol production from the conventional dry‐grind process to wet or dry fractionation processes. High oil, dent corn with high starch extractability, dent corn with low starch extractability and waxy corn were selected. In the conventional process, corn was ground using a hammer mill; water was added to produce slurry which was fermented. In the wet fractionation process, corn was soaked in water; germ and pericarp fiber were removed before fermentation. In the dry fractionation process, corn was tempered, degerminated, and passed through a roller mill. Germ and pericarp fiber were separated from the endosperm. Due to removal of germ and pericarp fiber in the fractionation methods, more corn was used in the wet (10%) and dry (15%) fractionation processes than in the conventional process. Water was added to endosperm and the resulting slurry was fermented. Oil, protein, and residual starch in germ were analyzed. Pericarp fiber was analyzed for residual starch and neutral detergent fiber (NDF) content. Analysis of variance and Fisher's least significant difference test were used to compare means of final ethanol concentrations as well as germ and pericarp fiber yields. The wet fractionation process had the highest final ethanol concentrations (15.7% v/v) compared with dry fractionation (15.0% v/v) and conventional process (14.1% v/v). Higher ethanol concentrations were observed in fractionation processes compared to the conventional process due to higher fermentable substrate per batch available as a result of germ and pericarp fiber removal. Germ and pericarp yields were 7.47 and 6.03% for the wet fractionation process and 7.19 and 6.22% for the dry fractionation process, respectively. Germ obtained from the wet fractionation process had higher oil content (34% db) compared with the dry fractionation method (11% db). Residual starch content in the germ fraction was 16% for wet fractionation and 44% for dry fractionation. Residual starch in the pericarp fiber fraction was lower for the wet fractionation process (19.9%) compared with dry fractionation (23.7%).     

Photodegradation of cassava and corn starches

The baking expansion properties of sour cassava starch (Polvilho azedo) are attributable to photochemical starch degradation induced by heterolactic fermentation after sun-drying. This study investigated the effects of UV irradiation on the different structural levels of cassava starch as compared to those of corn starch and dextrins. Photosensitive compounds excited at 360 and 290 nm in cassava starch were photodegraded when starch was exposed to sunlight or 360 nm irradiation. UV irradiation depolymerized cassava and corn starches, inducing modifications due, at least in part, to a mechanism involving free radicals. Lactic acid was also photodegraded. Photodegradation induced by UV absorption could have been due to fluorescent chromophores found in starches and nonfluorescent chromophores present in glucosidic units.     

Analysis of Alkylresorcinols in Wheat Germ Oil and Barley Germ Oil via HPLC and Fluorescence Detection: Cochromatography with Tocols

Alkylresorcinols are long‐chain phenolic compounds that have been reported to be localized in the outer layers of the kernels of wheat, rye, barley, and other grains. A sensitive HPLC method with fluorescence detection was recently reported for the quantitative analysis of alkylresorcinols in cereal grains and products. Using this new HPLC method we report for the first time that wheat germ oil contains moderate levels of alkylresorcinols, approximately 800–1,500 µg per gram of oil. We also found that commercial wheat germ oil and some experimental samples of wheat germ oil and barley germ oil also contained three unknown peaks. Upon further evaluation of these peaks it was found that the peaks appeared to be tocopherols (one peak of α‐tocopherol, one peak of δ‐tocopherol, and a peak with the combination of β‐ and γ‐tocopherol), even though the excitation and emission wavelengths for alkylresorcinols (excitation 274 nm and emission 300 nm) are different than those for tocols (excitation 294 nm and emission 326 nm). We also found that with this HPLC system one alkylresorcinol, AR17, had the same retention time (7.6 min) as δ‐tocotrienol and that another alkylresorcinol, AR19, had the same retention time (10.8 min) as α‐tocotrienol.     

Phytochemical and fiber components in oat varieties in the HEALTHGRAIN Diversity Screen

The levels and compositions of a range of phytochemicals (sterols, tocols, avenanthramides, folates, phenolic acids) and dietary fiber components were determined in five oat cultivars (four husked and one naked) grown on a single site in 2005. The total levels of tocols, phenolic acids, and avenanthramides varied by over 2-fold between cultivars, but less variation occurred in total sterols and total folates. Limited variation was also observed in the dietary fiber content and composition of the four husked lines. These results indicate that it may be possible to selectively breed for lines with high contents of dietary fiber and specific groups of phytochemicals.     

Comparative studies on thermochemical characterization of corn stover pretreated by white-rot and brown-rot fungi

The effects of white-rot and brown-rot fungal pretreatment on the chemical composition and thermochemical conversion of corn stover were investigated. Fungus-pretreated corn stover was analyzed by Fourier transform infrared spectroscopy and X-ray diffraction analysis to characterize the changes in chemical composition. Differences in thermochemical conversion of corn stover after fungal pretreatment were investigated using thermogravimetric and pyrolysis analysis. The results indicated that the white-rot fungus Irpex lacteus CD2 has great lignin-degrading ability, whereas the brown-rot fungus Fomitopsis sp. IMER2 preferentially degrades the amorphous regions of the cellulose. The biopretreatment favors thermal decomposition of corn stover. The weight loss of IMER2-treated acid detergent fiber became greater, and the oil yield increased from 32.7 to 50.8%. After CD2 biopretreatment, 58% weight loss of acid detergent lignin was achieved and the oil yield increased from 16.8 to 26.8%.     

Yield and Phytosterol Composition of Oil Extracted from Grain Sorghum and Its Wet‐Milled Fractions

Corn fiber contains an oil with high levels of three potential cholesterol‐lowering phytosterol compounds. Little information is available about the levels and types of phytosterols in sorghum. In this study, phytosterols were evaluated in grain sorhgum and its wet‐milled fractions and were compared with the phytosterols in corn. The study showed that sorghum kernels can provide a significant source of two phytosterol classes, free phytosterols (St) and fatty acyl phytosterol esters (St:E). Most of these phytosterols are concentrated in the wet‐milled fiber fraction followed by the germ fraction. In addition to phytosterols, other lipid classes such as wax esters and an aldehyde (50% C28 and 50% C30) are also present in the sorghum oil. Comparison of sorghum and corn kernels show that corn has 72–93% more phytosterols than sorghum.     

Comparison of Yield and Composition of Oil Extracted from Corn Fiber and Corn Bran

We recently reported that corn fiber oil contains high levels of three potential cholesterol-lowering phytosterol components: ferulate-phytosterol esters (FPE) (3–6 wt%), free phytosterols (1–2 wt%), and phytosterol-fatty acyl esters (7–9 wt%). A previous study also indicated that corn bran oil contained less phytosterol components than corn fiber oil. The current study was undertaken to attempt to confirm this preliminary observation using more defined conditions. Accordingly, oil was extracted from corn fiber and corn bran prepared under controlled laboratory conditions, using the same sample of corn hybrid kernels for each, and using recognized bench-scale wet-milling, and dry-milling procedures, respectively. After extraction, the chemical composition of the phytosterol components in the oil were measured. This study confirmed our previous observation—that FPE levels were higher in corn fiber oil than in corn bran oil. During industrial wet-milling, almost all of the FPE are recovered in the fiber fraction (which contains both fine and coarse fiber). During laboratory-scale wet-milling, ≈60–70% of the FPE are recovered in the coarse fiber (pericarp) and 30–40% are recovered in the fine fiber. During laboratory-scale dry-milling, <20% of the FPE are recovered in the bran (pericarp), and the rest in the grits. The recoveries of the other two phytosterol components (free phytosterols and phytosterol-fatty acyl esters) revealed a more complex distribution, with significant levels found in several of the dry- and wet-milled products.