首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 718 毫秒
1.
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.  相似文献   

2.
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.  相似文献   

3.
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.  相似文献   

4.
The variability in commercial corn hybrids for corn fiber yields, amounts of extractable oil, and levels of individual and total phytosterol components in corn fiber oil was determined. Also, the effect of growth location on fiber yields, fiber oil content, and the levels of individual and total phytosterol compounds was determined. Significant variation was observed in the commercial hybrids for fiber yield (13.2–16.6%) and fiber oil yield (0.9–2.4%). No significant correlation was observed between fiber and oil yields. Significant variations in the commercial corn hybrids were also observed in the individual phytosterol compounds in corn fiber oil: 2.9–9.2% for ferulate phytosterol esters (FPE); 1.9–4.3% for free phytosterols (St); and 6.5–9.5% for phytosterol fatty acyl esters (St:E). Positive correlations were observed among the three phytosterol compounds in the corn fiber oil (R = 0.75 for FPE and St:E; 0.48 for St:E and St; and 0.68 for FPE and St). The effect of location on dependent variables was also significant. The same hybrids grown at different locations showed a variation (range) of 4.0–17.5% for FPE, 4.9–12.2% for St:E, and 1.95–4.45% for St. Relative ranking of hybrids with respect to phytosterol composition was consistent for almost all of the growth locations.  相似文献   

5.
Coarse and fine fiber fractions obtained from the corn wet‐milling processes, with and without steeping chemicals (SO2 and lactic acid), were evaluated microscopically for structure and analytically for recovery of phytosterol compounds from the fiber oil. Microscopic results showed that wet milling, with and without chemicals during steeping, changed the line of fracture between pericarp and endosperm and therefore affected the recovery of the aleurone layer in coarse (pericarp) and fine (endosperm cellular structure) fiber. Analytical results showed that most of the phytosterols and mainly phytostanols in corn fiber are contributed by the aleurone layer. Hand‐dissection studies were performed to separate the two layers that comprise the wet‐milled coarse fiber, the aleurone, and pericarp layer. Analyses revealed that the aleurone contained 8× more phytosterols than the pericarp.  相似文献   

6.
Physical and chemical methods were used to recover starch and protein from wet-milled corn fiber. A single milling of the fiber produced an 18% yield of mill starch. By separating the mill starch with a starch table, 68% of this material was recovered as starch with a protein contamination of 0.66%. Milling increased fine fiber from 4.5% in the starting material to 11.5% after a single grind. Successive additional milling passes modestly increased the mill starch and fine fiber yields with a corresponding decrease in the coarse fiber yield. Pretreatment with combinations of lactic and sulfurous acids had only a small effect on the distribution and composition of the recovered fractions.  相似文献   

7.
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).  相似文献   

8.
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.  相似文献   

9.
The phytosterol‐containing oil in the corn fiber (corn fiber oil) has potential use as a natural low‐density lipoprotein (LDL) lowering nutraceutical but its low concentration (1–3%) makes it difficult and expensive to extract. Pretreatment of corn fiber with dilute acid or glucosidases removed nonlipid components of fiber, producing oil‐enriched fractions that should be more amenable to efficient and inexpensive oil extraction. Acid, as well as enzymes, significantly increased the content of corn fiber oil and its phytosterol compounds by hydrolyzing (and removing) the starch and nonstarch (cell wall) polysaccharides from the wet‐milled corn fiber. Dual treatment of the fiber with acid and enzyme greatly increased the concentrations of corn fiber oil and its phytosterol components, compared with acid or enzyme treatments alone. Depending on the treatment, the oil concentration in the residual solids increased from 0.3 to 10.8% (21–771% increase in conc.) and the total phytosterol concentration increased from 19.8 to 1256.2 mg/g of fiber (11–710% increase in conc.) compared with untreated fiber.  相似文献   

10.
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   

11.
Enzymatic milling (E‐Milling) is a process that could potentially replace the sulfur dioxide procedure currently used in all commercial wet‐milling facilities. E‐Milling incorporates the use of a short water soaking step (≤6 hr), a coarse grind, and the use of a protease to release the starch granules from the corn endosperm. E‐Milling does not require sulfur dioxide to obtain starch yields equivalent to conventional wet milling; however, the important antimicrobial effects of sulfur dioxide are not duplicated by the enzymatic process. The use of low levels of sulfur dioxide (sufficient for antimicrobial activity) is being proposed as an easily implemented means of microbial control during E‐Milling. To assess the effectiveness of E‐Milling under these conditions, fraction yields for milling experiments adding sulfur dioxide with and without added enzyme were compared with fraction yields from conventional 24‐hr steeping with 2,000 ppm SO2 and 0.55% lactic acid. Because adding enzyme and SO2 can both improve product yields and compositions independently, it was necessary to use a reduced level of enzyme (much less than necessary to generate “product quality” material) to observe differences in terms of product yields. The results show significant differences in starch, fiber, total gluten, and insoluble gluten recoveries between samples milled with SO2 and enzyme compared with those at the same SO2 level without enzyme addition. No significant differences were observed for soakwater or germ yields regardless of the SO2 level used. The yield benefits from adding both enzyme and SO2 are clearly shown over the addition of each individually, for all coproduct yields with the exception of the yields for germ.  相似文献   

12.
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.  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.
White, fluffy cellulose/arabinoxylan mixtures (CAX) were generated from the solid residues remaining after corn fiber gum (CFG) production. Most CAX were produced using variations of a process in which a single alkaline hydrogen peroxide (AHP) step was used for delignification and for CFG (arabinoxylan) extraction. The optimal ratio of H2O2 to corn fiber to water was 0.1:1:20. Holding this ratio constant, time and temperature conditions were systematically varied, and yields of CAX and CFG determined. Parallel processes were conducted without H2O2 to determine its effect on CAX and CFG yield. CAX prepared under identical conditions but without H2O2 retained nearly twice the levels of CFG sugars, as revealed from L‐arabinose, D‐xylose, and D,L‐galactose levels. Even the CAX prepared under extreme AHP conditions (1 hr, 100°C), however, contained 32.9% of these CFG sugars. This CAX was obtained in a 25.1% yield, whereas those produced under less vigorous conditions were obtained in higher yields, because they retained more CFG. CAX prepared in the presence of H2O2 hydrated very effectively, as indicated by their high swollen volumes and water absorbance values. This suggests potential food applications for CAX as a bulking agent. In addition, the open structure of the CAX matrix would render these residues suitable for chemical derivatization and enzymatic saccharification.  相似文献   

15.
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   

16.
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.  相似文献   

17.
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   

18.
A corn wet-milling process in which alkali was used was studied as an alternative to the conventional corn wet-milling procedure. In the alkali wet-milling process, corn was soaked in 2% NaOH at 85°C for 5 min and then debranned mechanically to obtain pericarp as a coproduct. Debranned corn was cracked in a roller mill, and the cracked corn was steeped with agitation for 1 hr in 0.5% NaOH at 45°C. The cracked and steeped corn was then processed to separate germ, fiber, and gluten by steps similar to those in conventional wet-milling. Alkali wet-milling yielded soakwater solids, pericarp, germ, starch, gluten, and fine fiber. The protein content of the starch and the starch content of the fiber from the alkali process were lower than those from the conventional process.  相似文献   

19.
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.  相似文献   

20.
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.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号