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1.
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).  相似文献   

2.
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%).  相似文献   

3.
A procedure that reduces diffusional limitations by periodically milling the corn to reduce particle size and stirring the ground mash in the presence of sulfur dioxide (SO2) and lactic acid was developed. The process, called intermittent milling and dynamic steeping (IMDS), includes three main stages: initial soaking (a short-time immersion in water) of whole kernels, initial cracking of the partially hydrated kernels, and dynamic steeping with interspersed milling. This study evaluated the three stages of the process separately, evaluating the effect of variables on each stage of the process. Corn fractions yield (germ, fiber, gluten, starch) were used to decide the best conditions for the soaking and steeping stages, and germ damage was used to determine the best kernel cracking method. Starch, gluten, and germ yields were not affected by soak temperatures (52–68°C) or soak time (1–3 hr). A temperature of 60°C was chosen for soaking because it increased the rate of kernel hydration without gelatinizing starch, which happens at higher temperatures. A 2-hr soak time was preferred because there was less fiber in the germ fraction and less germ damage was observed. Although there were no advantage to using SO2 or lactic acid in the soak water, the presence of these compounds during dynamic steeping enhanced starch yield. The starch yield for 3 hr of dynamic steeping was not statistically different from the starch yield for a 7.5-hr dynamic steep. The Bauer mill was preferred over the use of a roller mill or a commercial grade Waring blender for kernel cracking. The IMDS process produced, on an average, 1 percentage point more starch than the conventional 36-hr steeping process. Total steep or kernel preparation time was reduced from 24–40 hr for conventional wet-milling to 5 hr for the IMDS process.  相似文献   

4.
The fate of DNA during steeping, wet-milling, and subsequent processing of maize was examined using a sensitive polymerase chain reaction (PCR-based) detection system. The system used specific amplification of maize DNA sequences by primers generated toward plant nuclear- and chloroplast-encoded genes. The PCR method facilitated analysis of DNA content in food products, which is an important issue in use of genetically modified organisms. In a conventional laboratory wet-milling countercurrent steep system, DNA was detected in maize kernels throughout the process but was not found in steepwater. After kernels were wet-milled, DNA was detected in the starch, germ, coarse fiber, and wet gluten fractions but not in the fine fiber fraction. When dried by heating at 135°C for 2 hr, DNA was degraded to undetectable levels in the wet-milled gluten fraction and hydrated kernels. DNA was not detected in feed pellets, starch, dextrose, sorbitol, or high-fructose maize syrup made from industrial wet-milled samples. Although DNA could be detected in laboratory wet-milled fractions, some degree of degradation occurred after extended exposure to steepwater. Countercurrent steepwater samples from the later stages of the steeping process were able to degrade DNA. The level of DNA degradation appeared to correspond to the presence of sulfur dioxide and may represent a physiochemical rather than an enzyme-mediated process. Our results indicate that some steps in the steeping and wet-milling process can degrade maize genomic and plastid DNA.  相似文献   

5.
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.  相似文献   

6.
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.  相似文献   

7.
Effects of phytase addition, germ, and pericarp fiber recovery were evaluated for the E‐Mill dry grind corn process. In the E‐Mill process, corn was soaked in water followed by incubation with starch hydrolyzing enzymes. For each phytase treatment, an additional phytase incubation step was performed before incubation with starch hydrolyzing enzymes. Germ and pericarp fiber were recovered after incubation with starch hydrolyzing enzymes. Preliminary studies on phytase addition resulted in germ with higher oil (40.9%), protein (20.0%), and lower residual starch (12.2%) contents compared to oil (39.1%), protein (19.2%), and starch (18.1%) in germ from the E‐Mill process without phytase addition. Phytase treatment resulted in lower residual starch contents in pericarp fiber (19.9%) compared to pericarp fiber without phytase addition (27.4%). Results obtained led to further investigation of effects of phytase on final ethanol concentrations, germ, pericarp fiber, and DDGS recovery. Final ethanol concentrations were higher in E‐Mill processing with phytase addition (17.4% v/v) than without addition of phytase (16.6% v/v). Incubation with phytases resulted in germ with 4.3% higher oil and 2.5% lower residual starch content compared to control process. Phytase treatment also resulted in lower residual starch and higher protein contents (6.58 and 36.5%, respectively) in DDGS compared to DDGS without phytase incubations (8.14 and 34.2%, respectively). Phytase incubation in E‐Mill processing may assist in increasing coproduct values as well as lead to increased ethanol concentrations.  相似文献   

8.
Effect of lactic acid, SO2, temperature, and their interactions were assessed on the dynamic steeping of a Brazilian dent corn (hybrid XL 606) to determine the ideal relationship among these variables to improve the wet‐milling process for starch and corn by‐products production. A 2×2×3 factorial experimental design was used with SO2 levels of 0.05 and 0.1% (w/v), lactic acid levels of 0 and 0.5% (v/v), and temperatures of 52, 60, and 68°C. Starch yield was used as deciding factor to choose the best treatment. Lactic acid added in the steep solution improved the starch yield by an average of 5.6 percentage points. SO2 was more available to break down the structural protein network at 0.1% than at the 0.05% level. Starch‐gluten separation was difficult at 68°C. The lactic acid and SO2 concentrations and steeping temperatures for better starch recovery were 0.5, 0.1, and 52°C, respectively. The Intermittent Milling and Dynamic Steeping (IMDS) process produced, on average, 1.4% more starch than the conventional 36‐ hr steeping process. Protein in starch, oil content in germ, and germ damage were used as quality factors. Total steep time can be reduced from 36 hr for conventional wet‐milling to 8 hr for the IMDS process.  相似文献   

9.
In the dry-grind process, corn starch is converted into sugars that are fermented into ethanol. The remaining corn components (protein, fiber, fat, and ash) form a coproduct, distillers dried grains with solubles (DDGS). In a previous study, the combination of sieving and elutriation (air classification), known as the elusieve process, was effective in separating fiber from DDGS. In this study, elusieve fiber was evaluated for ethanol production and results were compared with those reported in other studies for fiber from different corn processing techniques. Fiber samples were pretreated using acid hydrolysis followed by enzymatic treatment. The hydrolyzate was fermented using Escherichia coli FBR5 strain. Efficiency of ethanol production from elusieve fiber was 89–91%, similar to that for pericarp fiber from wet-milling and quick fiber processes (86–90%). Ethanol yields from elusieve fiber were 0.23–0.25 L/kg (0.027–0.030 gal/lb); similar to ethanol yields from wet-milling pericarp fiber and quick fiber. Fermentations were completed within 50 hr. Elusieve fiber conversion could result in 1.2–2.7% increase in ethanol production from dry-grind plants. It could be economically feasible to use elusieve fiber along with other feedstock in a plant producing ethanol from cellulosic feedstocks. Due to the small scale of operation and the stage of technology development for cellulosic conversion to ethanol, implementation of elusieve fiber conversion to ethanol within a dry-grind plant may not be currently economically feasible.  相似文献   

10.
A modified dry‐grind corn process has been developed that allows recovery of both pericarp and endosperm fibers as coproducts at the front end of the process before fermentation. The modified process is called enzymatic milling (E‐Mill) dry‐grind process. In a conventional dry‐grind corn process, only the starch component of the corn kernel is converted into ethanol. Additional ethanol can be produced from corn if the fiber component can also be converted into ethanol. In this study, pericarp and endosperm fibers recovered in the E‐Mill dry‐grind process were evaluated as a potential ethanol feedstock. Both fractions were tested for fermentability and potential ethanol yield. Total ethanol yield recovered from corn by fermenting starch, pericarp, and endosperm fibers was also determined. Results show that endosperm fiber produced 20.5% more ethanol than pericarp fiber on a g/100 g of fiber basis. Total ethanol yield obtained by fermenting starch and both fiber fractions was 0.370 L/kg compared with ethanol yield of 0.334 L/kg obtained by fermenting starch alone.  相似文献   

11.
Our report shows the calcium ion diffusion process through the different parts of maize kernels (pericarp, endosperm, and germ) during the traditional nixtamalization process as a function of steeping time (t) 0–24 hr. The cooking step of the nixtamalization process used 3 kg of maize kernels in 6L of water and 2% calcium hydroxide (w/w). The cooking temperature was 92°C for 40 min. The calcium content of the samples was measured using atomic absorption spectroscopy. We found that the whole instant corn flour, pericarp, endosperm, and germ, had a nonlinear relationship to steeping time, showing a local maximum at 9 hr. Analysis of the different parts of the nixtamalized kernels showed that in short steeping times (0–5 hr) calcium diffusion took place mainly in the pericarp. Calcium diffusion in the endosperm and germ occurred gradually over longer steeping times. However, the physical state of the kernels (broken kernels) accelerated the diffusion process. Calcium diffusion occurred first in the pericarp, followed by the endosperm and germ. Immediately after cooking (t = 0 hr), we found a 1.148% calcium content in the pericarp, 0.007% in the germ, and 0.028% in the endosperm. After 24 hr of steeping, the calcium contents were 2.714% in the pericarp, 0.776% in the germ, and 0.181% in the endosperm. In another study, the calcium content in the endosperm was measured by first separating the 10% from the outermost, followed by another 10% from the next endosperm tissue, and concluding with the remaining 80%. Calcium ions were present mainly in the outermost layers of the endosperm. The damaged kernels steeped for more than 5 hr showed greater calcium concentrations than the undamaged counterparts.  相似文献   

12.
A pilot-plant wet-milling process was specially used to produce corn gluten meal (CGM) with a relatively high protein content (49.8% from Pioneer 3394 and 53.7% from Wilson D110). The protein content of the CGM obtained from a starch table in our pilot-plant procedure was similar to the results obtained by using the hydrocyclone method. Wilson D110 has a higher protein content in its corn kernels, producing higher yield and protein content gluten than the Pioneer 3394, which has lower protein content in the corn. The effects of drying method and temperature on the color of CGM were also discussed.  相似文献   

13.
The effect of adding lactic acid and sulfur dioxide at different times from the start of batch steeping on corn starch yields was studied. Five commercial hybrids were steeped with 0.5% lactic acid or 0.2% sulfur dioxide added over the first 15 hr of steeping and wet-milled following a 100-g corn wet-milling procedure. No significant differences were observed in starch yields when lactic acid was added to the steep solution (SO2 and water) from 0 hr (start of steeping) to 15 hr. Addition of SO2 to the steep solution (lactic acid and water) resulted in significantly higher average starch yields when SO2 was added between 5 and 15 hr compared with addition at 0 hr (SO2 and lactic acid for full 24 hr of steeping). Based on the results of the first experiment, a second experiment was done in which one of five original hybrids was steeped for 24 hr, during which lactic acid or SO2 was added until 23.9 hr (i.e., 5 min before milling) after the start of steeping. Similar results were found in the second experiment. Residual protein in starch samples did not exceed 0.85%. Steepwater protein content decreased with delays (16–20 hr) in adding either chemical to the steep solution. A significant effect on starch pasting properties of chemicals and duration of chemicals in steep-water was observed. Testing these findings using a larger scale (1,000 g) corn wet-milling procedure produced results similar to those obtained with the 100-g corn wet-milling procedure.  相似文献   

14.
Three fibrous corn wet-milling fractions, coarse fiber, fine fiber, and spent flake, were isolated. More highly valued uses are sought for these milling products, which are generally directed into the corn gluten feed product stream. Coarse fiber was further dissected into pericarp and aleurone layers. An alkaline hydrogen peroxide process was used to efficiently extract corn fiber gum (CFG) from each of the materials. CFG is a hemicellulose B arabinoxylan which also contains low levels of D,L-galactose and D-glucuronic acid. CFG yield information was obtained from each source, as well as structural information in terms of degrees of branching of the beta-D-xylopyranose backbone with alpha-L-arabinofuranosyl moieties. There were significant differences in degree of branching among the CFGs from the various fractions. A novel capillary electrophoresis procedure was developed to measure these differences. Solution viscosity differences among the CFGs were also observed.  相似文献   

15.
U.S. No. 2 yellow dent corn was randomly probe‐sampled from rail cars being shipped to a wet‐milling plant from a Corn Belt local elevator. The probe samples were blended together and kernels were sorted into four levels of stress cracks (0, 1, 2, or multiple). Each level of stress cracking was then laboratory wet‐milled in triplicate. The only statistically observed differences were in total fiber and in protein content of the gluten meal fraction. The starch yield difference between zero stress cracked corn and multiple stress cracked corn was smaller (0.8%) than would be expected if stress cracking were an indicator of damage to the wet‐milling characteristics of the corn.  相似文献   

16.
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.  相似文献   

17.
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.  相似文献   

18.
The present work was focused on the effects of acid and alkali on the uniaxial extensional deformation of gluten bioplastics compression‐molded at 80 and 110°C. Water absorption and morphology observation were also performed to characterize the properties and morphology of the gluten bioplastics. The results show that HCl did not show catalysis function for cross‐linking proteins at 80°C and even hindered the cross‐linking reaction at 110°C. On the other hand, NaOH generally accelerated the cross‐linking reaction during compression‐molding, thus significantly improving Young's modulus, tensile strength, and strain at break. However, an NaOH content >0.5 wt% could cause adverse effects at molding temperatures as high as 110°C.  相似文献   

19.
A detailed economic analysis of a 914 tonnes/day (36,000 bu/day) “Quick Germ” ethanol process was performed. The Quick Germ ethanol process is a combination of a dry-grind and a wet-milling ethanol process. The Quick Germ ethanol process increases the coproduct value in the dry-grind ethanol process by recovering germ before fermentation. Germ is recovered using the conventional wet-milling degermination process. Economic assessment of the Quick Germ process proved profitable. The savings achieved by recovering germ as a coproduct and by increasing the fermentor capacity due to removal of nonfermentables from the corn mash will reduce the manufacturing cost of ethanol by 2.69 ¢/L (10.19 ¢/gal or $0.265/bu) when compared to the conventional dry-grind ethanol process.  相似文献   

20.
Oxidized corn starch prepared by a semi-dry process using hydrogen peroxide as an oxidant was studied. The optimum oxidation conditions of corn starch were mole ratio of H2O2 and anhydroglucose unit (0.219); mole ratio of NaOH and anhydroglucose unit (0.144); moisture content of the reaction mixture (27.2%); and reaction temperature (65°C). Compared with oxidized corn starch produced by reacting starch with sodium hypochlorite in alkaline slurry, oxidized corn starches produced by a semi-dry process apparently had different properties. Oxidation by a semi-dry process for corn starch resulted in significant changes in the degree of crystallinity of starch and the changes increased with the increase of carboxyl content of starch. Peak viscosities of oxidized starches produced by a semi-dry process were lower than those of commercial corn starch at similar carboxyl contents, while the final viscosities and setbacks of the former were much higher than the latter. There were apparent differences for texture properties among oxidized starches prepared by different processes. Onset temperature, peak temperature, and conclusion temperature of semi-dry oxidation starches were higher than those of commercial oxidized starch, while the enthalpy of gelatinization of the former were lower than the latter.  相似文献   

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