Comparison of Alkali and Conventional Corn Wet-Milling: 1-kg Procedures

An alkali corn wet-milling process was developed to evaluate the process as a method to produce high purity corn starch and coproducts with added value. Using a single hybrid (R1064 × LH59), the effects of alkali concentration (0.18–0.82% NaOH), time (29–61 min), and temperature (36–75°C) were investigated. Starch yield was not affected by steep time or temperature. Starch yield was optimal at 65.2% using 0.5% alkali. Increasing the concentration of alkali to 0.82% or decreasing it to 0.18% caused a decrease in starch yield of 8–10 percentage points. Other wet-milling products (fiber, germ, and gluten) also were affected. Steep conditions of 0.5% NaOH, 60 min, and 45°C gave optimal starch yield. Comparisons between alkali and sulfur dioxide wet-milling processes, using 1-kg sample size, were performed on 10 commercial yellow dent corn hybrids. The alkali process averaged 1.7 percentage points more starch than the sulfur dioxide process. Each hybrid had a higher starch yield when wet-milled with the alkali method. Alkali wet-milling produced pure corn starch with <0.30% protein (db).     

Comparison of Laboratory and Pilot-Plant Corn Wet-Milling Procedures

One waxy and three regular yellow dent corn hybrids were wet milled by using two scales of laboratory procedures (modified 100-g and 1-kg) and a pilot-plant procedure (10-kg). The modified 100-g and 1-kg laboratory procedures gave similar yields of wet-milling fractions. Starch yields and recoveries were significantly lower for the pilot-plant procedure, whereas gluten and fiber yields were greater because of their high contents of unrecovered starch. Protein contents of the starches obtained by all three procedures were within commercially acceptable limits (<0.50% db for normal dent corn and <0.30% for waxy corn). Rankings for starch yields and starch recoveries for the four hybrids, having very different physical and compositional properties, were the same for all three procedures. The harder the grain, the lower the yield and recovery of starch. Least significant differences (P < 0.05) for starch yield were 0.8% for the modified 100-g procedure, 1.2% for the 1-kg procedure, and 2.0% for the pilot-plant procedure.     

Near-Infrared Reflectance Correlated to 100-g Wet-Milling Analysis in Maize

An understanding of the genetic control of starch, protein, and oil concentrations in the corn (Zea mays L.) kernel is essential for improvement of grain quality. Because large numbers of progenies are needed for genetic studies, a rapid, accurate, analytical procedure is necessary. As part of a study to identify chromosomal regions associated with starch and protein, a rapid near-infrared reflectance (NIR) method and a more labor-intensive 100-g wet-milling procedure were compared for consistency in ranking families and identifying quantitative trait loci (QTL) using a set of 200 F₂S₁ families from the cross of the 70th generations of the Illinois High Protein (IHP) × Illinois Low Protein (ILP) corn strains. NIR starch and wet-milling starch values were highly correlated (r = 0.80), as were NIR protein and gluten measured by wet-milling (r = 0.72). Chromosomal regions associated with NIR starch and wet-milling starch were generally the same. Fiber concentration was significantly negatively correlated with starch and positively correlated with protein. Chromosome regions with significant associations with starch also had significant associations with fiber. The NIR method is satisfactory for measuring starch and protein in material with a wide range of variability in the early stages of a corn-breeding program.     

Nitrogen and Sulfur Concentrations and Flow Rates of Corn Wet-Milling Streams

Nitrogen (N) and sulfur (S) concentrations can affect the market value of coproducts from corn wet-milling. The composition of parent streams would be expected to affect composition of the resulting coproducts but there are few published data available to examine this relationship. Concentration and flow data are needed to determine which streams are important in modifying N and S coproduct concentrations. The objective was to measure concentrations and flows of N and S in corn wet-milling streams. Samples were taken from 21 process streams from 3 wet-milling plants during two periods of three weeks each; N and S concentrations of each sample were determined. There were large differences in N and S concentrations among processing streams; within most streams, N and S concentrations were similar among plants. Concentrations of N and S were related inversely to flow rates. Steepwater and gluten streams contained most of the N and S flow and provide an opportunity for modification. The process water stream carried large quantities of N and S and represents another opportunity for improving process efficiency and coproduct value.     

Effect of Chemical Pretreatments and Lactic Acid on the Rate of Water Absorption and Starch Yield in Corn Wet-Milling

The relative effectiveness of dehulling, potassium hydroxide dipping (alkali concentrations 0.2, 0.5, and 1.0 %), and ethyl oleate spraying (aqueous emulsion 1%, v/v) to increase the rate of water absorption by dent and flint corn during steeping was compared with untreated corn samples. These pretreatments increased the water absorption rate of both hybrids when compared with the untreated control samples. To evaluate the observed increase, the diffusion coefficients of pretreated and untreated corn samples were estimated. Corn grains steeped in SO₂ aqueous solution and variable lactic acid concentrations (0.2, 0.5, and 1.0%, v/v) were performed. Absorption rates for lactic acid concentrations were ≈0.5% higher than those steeped only in SO₂ solution. This effect was more marked for dent than for flint corn. Corn samples pretreated with potassium hydroxide had lower starch yields than the control. However, the presence of lactic acid in steepwater increased the starch yield of dent and flint corn, particularly for the samples treated with alkaline solution. This procedure was particularly beneficial for flint corn. An effective release of the starch granules was achieved within 24 hr of steeping.     

Comparison of Raw Starch Hydrolyzing Enzyme with Conventional Liquefaction and Saccharification Enzymes in Dry‐Grind Corn Processing

In a conventional dry‐grind corn process, starch is converted into dextrins using liquefaction enzymes at high temperatures (90–120°C) during a liquefaction step. Dextrins are hydrolyzed into sugars using saccharification enzymes during a simultaneous saccharification and fermentation (SSF) step. Recently, a raw starch hydrolyzing enzyme (RSH), Stargen 001, was developed that converts starch into dextrins at low temperatures (<48°C) and hydrolyzes dextrins into sugars during SSF. In this study, a dry‐grind corn process using RSH enzyme was compared with two combinations (DG1 and DG2) of commercial liquefaction and saccharification enzymes. Dry‐grind corn processes for all enzyme treatments were performed at the same process conditions except for the liquefaction step. For RSH and DG1 and DG2 treatments, ethanol concentrations at 72 hr of fermentation were 14.1–14.2% (v/v). All three enzyme treatments resulted in comparable ethanol conversion efficiencies, ethanol yields, and DDGS yields. Sugar profiles for the RSH treatment were different from DG1 and DG2 treatments, especially for glucose. During SSF, the highest glucose concentration for RSH treatment was 7% (w/v), whereas for DG1 and DG2 treatments, glucose concentrations had maximum of 19% (w/v). Glycerol concentrations were 0.5% (w/v) for RSH treatment and 0.8% (w/v) for DG1 and DG2 treatments.     

玉米秸秆与污泥的腐解物对盐碱地化学指标的影响

为探索发酵后的玉米秸秆对内蒙古地区盐碱化土壤化学性质(有机质、ESP,pH值、EC、土壤代换性Na~+)的影响,在实验室条件下以污泥作为接种物,将玉米秸秆在不同发酵的条件下以不同梯度的秸秆还田量施加到盐碱化土壤中,以施加未发酵的玉米秸秆为对照。结果显示:(1)施加玉米秸秆对土壤的部分化学性质有着一定的改善,且发酵后的玉米秸秆比未发酵的玉米秸秆效果要好;(2)当玉米秸秆与污泥的配比为2∶1且秸秆还田量为75%时,土壤的有机质含量上升幅度最大,土壤的ESP、pH值、土壤代换性Na~+降低幅度最大;(3)施加玉米秸秆对土壤的EC作用不明显,反而使EC的含量有所上升,施用发酵后的玉米秸秆尤为明显。综合考虑,在本试验条件下针对该土壤最佳参数为:玉米秸秆与污泥配比为2∶1,发酵后的玉米秸秆还田量为75%。     

Effects of Alkali Debranning,Roller Mill Cracking and Gap Setting,and Alkali Steeping Conditions on Milling Yields from a Dent Corn Hybrid

Starch yield was significantly affected by all three main unit operations in alkali wet‐milling (debranning, roller milling, and steeping). The conditions for the three unit operations were studied using a single hybrid. Studies on debranning showed that optimal separation between pericarp and corn endosperm was obtained when corn was soaked in a 1.5–2% NaOH solution at 85°C for 5 min. Passing debranned corn through smooth roller mill once or twice did not affect the product yields, but passing the corn through the roller mill three times decreased the germ yield because of a large amount of broken germ. A 62% higher processing rate could be achieved when passing corn through the mill twice than by passing it through the mill once. The gap should be set at 2.0 mm when passing corn through the mill once, and it should be set at 3.5 mm for the first pass and 2.0 mm for the second pass when passing corn through the mill twice. Starch yield was more sensitive to NaOH concentration and steep temperature than to steep time. The highest starch yield was obtained when steeping corn in 0.5% NaOH for 1 hr at 45°C.     

Comparison of Enzymatic (E‐Mill) and Conventional Dry‐Grind Corn Processes Using a Granular Starch Hydrolyzing Enzyme

A new low temperature liquefaction and saccharification enzyme STARGEN 001 (Genencor International, Palo Alto, CA) with high granular starch hydrolyzing activity was used in enzymatic dry‐grind corn process to improve recovery of germ and pericarp fiber before fermentation. Enzymatic dry‐grind corn process was compared with conventional dry‐grind corn process using STARGEN 001 with same process parameters of dry solid content, pH, temperature, enzyme and yeast usage, and time. Sugar, ethanol, glycerol and organic acid profiles, fermentation rate, ethanol and coproducts yields were investigated. Final ethanol concentration of enzymatic dry‐grind corn process was 15.5 ± 0.2% (v/v), which was 9.2% higher than conventional process. Fermentation rate was also higher for enzymatic dry‐grind corn process. Ethanol yields of enzymatic and conventional dry‐grind corn processes were 0.395 ± 0.006 and 0.417 ± 0.002 L/kg (2.65 ± 0.04 and 2.80 ± 0.01 gal/bu), respectively. Three additional coproducts, germ 8.0 ± 0.4% (db), pericarp fiber 7.7 ± 0.4% (db), and endosperm fiber 5.2 ± 0.6% (db) were produced in addition to DDGS with enzymatic dry‐grind corn process. DDGS generated from enzymatic dry‐grind corn process was 66% less than conventional process.     

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.     

土壤有机质含量与玉米生产力的关系

土壤有机质是土壤肥力的重要指标。本文通过空间移位的方法,将东北黑土带由南向北5个点有机质含量为18.1g kg-1、31.1g kg-1、54.6g kg-1、103.9g kg-1、53.6g kg-1的农田黑土,分别移至黑龙江省的海伦市和吉林省的德惠市的两种气候下,通过田间试验的方法,研究了黑土有机质含量与玉米生产力的关系。结果表明,在相同的施肥条件下,土壤有机质含量与玉米产量间不存在显著相关关系,产量差异不显著;施肥对各种有机质含量的黑土均有显著增产作用,增产幅度在12.3%～64.1%,黑土带的南部区域德惠市的施肥增产作用要明显高于北部区域海伦市的增产作用。     

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%).     

燕麦幼苗对盐胁迫和碱胁迫的生理响应差异

为探讨‘定莜6号’燕麦对盐胁迫和碱胁迫的生理响应差异,采用砂培法研究了不同浓度(0mmol/L,50mmol/L,100mmol/L,150mmol/L和200mmol/L)NaCl和NaHCO3胁迫对幼苗生长、活性氧代谢和渗透调节物质积累的影响。结果表明:(1)随着NaCl和NaHCO3浓度增大,燕麦植株干重及叶片K+含量和K+/Na+明显下降,叶片Na+含量及O2·产生速率、H2O2和MDA含量显著提高。NaHCO3胁迫的上述指标变幅大于NaCl胁迫。(2)不同浓度NaCl和NaHCO3胁迫均引起燕麦叶片SOD、CAT、POD和APX活性提高或降低;NaHCO3胁迫与NaCl胁迫相比抗氧化酶激活或受抑的程度在不同Na+浓度下表现不同。NaHCO3胁迫的燕麦叶片ASA和GSH含量低于相同Na+浓度下的NaCl胁迫,100 mmol/L Na+浓度下GSH含量则相反。(3)50~150 mmol/L Na+浓度下,NaHCO3胁迫的燕麦叶片具有比NaCl胁迫更高的可溶性糖含量,200mmol/L Na+浓度下可溶性糖含量则相反。NaHCO3胁迫的燕麦叶片游离氨基酸含量明显高于NaCl胁迫,脯氨酸含量则相反。上述结果表明,燕麦的耐碱性低于耐盐性,这可能与碱胁迫引起Na+、K+更严重的失衡及活性氧清除系统变化和渗透调节物质积累存在差异有关。     

Interactions Between Sulfur and Selenium Uptake by Corn in Solution Culture

Interactions between sulfur (S) and selenium (Se) uptake and accumulation in corn (Zea mays) plants were investigated in solution culture. Two concentrations (5 and 10 μ M) of Se (as selenate) and three concentrations of S (as sulfate) (0.5, 1.5, and 2.5 mM) were used. Results showed that shoot and root biomass were affected significantly by different S concentrations in solution, but not affected by Se application when S concentrations in solution were lower than 1.5 mM. Selenium concentrations as well as Se accumulation in shoots and roots on a dry weight basis increased dramatically with increasing Se concentrations in solution. At a constant Se level, increasing S in solution reduced Se concentrations. Selenium accumulation in plants was not affected by S application, except in nutrient solution with Se at a concentration of 10 μ M. Sulfur concentrations and S accumulation in shoots increased significantly with increasing Se concentrations in solution, while those in roots were unaffected by Se addition. Solution-to-shoot transfer factors and shoot-root distribution coefficients of Se and S were also discussed. These data suggest that it is necessary to manage carefully both S and Se levels in solution or in soils for supplementation of Se in plants. Results from this study indicate that human Se nutrition can be improved by supplementation of Se in crops.     

Comparison of Lead Extraction and Detection Procedures for Six Canadian Soils

The effects of acid digestion procedures and instrumentation on extracted lead (Pb) concentrations from several soils, including a mildly Pb-contaminated soil, were determined using a two-factor factorial experiment. The two factors were (i) digestion procedure [seven levels: U.S. EPA, AOAC (dry ashing), nitric acid (NA), three aqua regia procedures (AR1, AR2, and AR3), and hydrofluoric acid (HF)] and (ii) instrumentation [two levels: atomic absorption spectrometry (AAS) and inductively coupled plasma (ICP) spectroscopy]. The greatest Pb recovery was obtained when soils were digested with HF and analyzed by AAS. The results suggest that the AOAC procedure (a standard procedure for recovery of soil nutrients and trace elements in Canadian laboratories) and EPA procedure (a standard procedure in American laboratories) may underestimate Pb concentrations in some Atlantic Canadian soil types. The AAS procedure is more accurate than ICP for determining Pb concentrations in soil with a history of PbHAsO₄, at least for Atlantic Canadian soils.     

Comparison of Gas Distribution Properties of Conventional and High Capacity Structured Packings

This paper presents the results of an experimental study carried out using large scale equipment to observe the effect of geometry on gas distribution properties of a high capacity corrugated sheet str...     

Comparison of Two Procedures for Extraction and Clean-up ofOrganophosphorus and Pyrethroid Pesticides in Sediment

Two procedures were compared for extraction and clean-up of 20 organophosphorus and 19 pyrethroid pesticidesin sediment to identify the more effective procedure for groups of pesticides or individual compounds. In Procedure I,methanol/water and n-hexane were used for extraction, and 1:10 (v/v) dichloromethane in n-hexane and acetone wereused as eluents for eluting the analyte through the cartridge, with one evaporating steps on a rotary evaporator and twoeluting steps on the cartridge, n-hexane/acetone (2:1, v/v) was used for extraction and elution in Procedure II with oneevaporating step on a rotary evaporator and one eluting step oll the cartridge. All extractions were performed underan ultrasonic bath and gas chromatography and mass spectrometry were utilized for measurements. Procedure II wasdeveloped as a rapid, timesaving, less costly and safer substitute for Procedure I which was an old method. ProcedureII was more effective for almost all the organophosphorus pesticides tested and 11 of the 19 pyrethroid pesticides, whileProcedure I was more appropriate for analysis of 5 pyrethroid pesticides. However, recoveries of most pyrethroid pesticideswere fairly low. Thus, further studies should focus on adjustment and formulation of solvents for more efficient extractionand clean-up of pyrethroid pesticides from sediment samples.     

有机种植与常规种植体系的比较——基于土壤与肥料的视角

有机种植体系因其安全、绿色、可持续的特点在国内外得到了普遍关注,自其发展以来,关于有机与常规种植体系的比较屡见不鲜,但基于土壤与肥料视角的系统比较在国内还鲜见报道。土壤为植物提供了直接生活环境,从土壤与肥料的角度能全面地理解有机与常规种植体系的本质不同及影响。本文综合分析了前人的研究结果,从土壤与肥料的视角对有机和常规种植体系进行系统比较,初步阐述了两种种植体系下作物产量、品质、土壤肥力效应、环境效应的差异及产生差异的可能原因。分析发现在作物种植初期有机体系的产量大多低于常规体系,但增产潜力较大;相比常规种植体系,有机种植体系可改善土壤性质、提高土壤肥力,且一般有助于提高农产品品质;此外,有机种植体系对大气环境和水环境的污染风险低于常规种植体系。产生差异的原因可能是有机种植体系下,前期土壤氮素及速效养分释放较缓慢,且随着种植年限的增加,土壤固碳能力逐渐增强,土壤微生物多样性增加,土壤养分利用率提高。