共查询到20条相似文献，搜索用时 296 毫秒
1.
An improved means of isolating zein is needed to develop new uses for corn zein. We have measured the yield of zein and evaluated the ability of acetic acid to remove zein from corn gluten meal, distillers dried grains, and ground corn using acetic acid as solvent. Acetic acid removed zein more quickly, at lower temperatures, and in higher yields when compared with alcoholic solvents. After 60 min at 25°C, ≈50% of the zein in corn gluten meal was removed. A step change in yield from 43 to 50% occurs as the extraction temperature is increased from 40 to 55°C after mixing for 30 min at 25% solids. The protein composition of the zein removed from corn gluten meal using acetic acid is very similar to that of commercial zein by SDS‐PAGE. The zein obtained from corn gluten meal using acetic acid had higher amounts of fatty acids and esters according to IR analysis, leading to slightly lower protein content. Films made from zein extracted from corn gluten meal using acetic acid had lower tensile strength (≈60% lower) than films produced from commercial zein. Fibers with very small diameter (0.4–1.6 μm) can be produced by electrospinning using the AcOH solution obtained after corn gluten meal extraction. 相似文献
2.
John W. Lawton 《Cereal Chemistry》2006,83(5):565-568
Traditionally, zein is isolated and recovered from corn gluten meal (GCM) using aqueous alcohol as the solvent. Recovery of zein from this solvent is inconvenient and costly. Zein is insoluble in 100% ethanol at room temperature, but it is soluble at 120°C in ethanol. Absolute ethanol effectively extracted zein from CGM, distillers dried grains (DDG), and ground corn. Zein was extracted from CGM with absolute ethanol in a high‐pressure reactor at 130°C. After extracting at 130°C for 45 min, the solution was pumped out of the extractor and allowed to cool. Upon cooling, the zein precipitated from solution. The precipitate was removed from the solution and air‐dried, resulting in 14% recovery of the starting material. The recovered precipitate had an average protein content of >90% on a dry basis, accounting for ≈20% of the CGM protein and recovered ≈35% of its zein. No differences were seen in the amount of zein extracted from CGM samples that were hand‐collected off the dewatering screen and gently dried, versus commercial CGM samples. The commercial CGM did produce a greater amount of solubles. The extraction procedure also worked at temperatures as low as 90°C. The lower temperature did produce lower yields of extracted zein. The zein extracted at the lower temperatures was less brown, but zein extracted at either temperature was almost fully soluble in traditional zein solvents. 相似文献
3.
Twelve corn gluten meal samples obtained from six wet-milling plants were processed into zein. Zein was extracted using 88% aqueous isopropyl alcohol at pH 12.5, followed by chilling. Protein recovery ranged from 21.3 to 32.0%, and protein purity ranged from 82.1 to 87.6%. Protein recovery increased as the protein purity increased (r = 0.76) (P < 0.01). One of the major factors influencing extraction yield was protein composition; especially α-zein content, which ranged from 53.4 to 64% of the total protein in the corn gluten meal samples. The intensity of red color of the corn gluten meal was negatively correlated with protein recovery and zein purity (r = -0.66 and -0.72, respectively) (P < 0.02). 相似文献
4.
Corn can be fractioned to produce starch, fiber, oil, and protein in relatively pure forms. The corn kernel contains 9–12% protein, but half of this is an industrially useful protein called zein. Dry milled corn (DMC), corn gluten meal (CGM), and distiller's dried grains with solubles (DDGS) are all coproducts from corn that contain zein and are used for zein extraction. Because it is insoluble in water, zein has found uses in many products such as coatings, plastics, textiles, and adhesives. Newer applications are taking advantage of zein's biological properties for supporting growing cells, delivering drugs, producing degradable sutures, and producing biodegradable plastics. This review covers zein characteristics and nomenclature, past and current practices in processing and extraction of zein from corn products and coproducts, and the modifications of zein for various applications. 相似文献
5.
Wang JF Geil PH Kolling DR Padua GW 《Journal of agricultural and food chemistry》2003,51(20):5849-5854
Matrix-assisted laser desorption/ionization mass spectrometry (MALDI/MS) was used to analyze the protein composition of corn prolamine (zein). Mass spectra were obtained from commercial zein and zein extracted with aqueous 2-propanol and aqueous ethanol from consumer corn meal. For the commercial zein, three major zein fractions with m/z 26.8k, 24.1k, and 23.4k were clearly seen with two minor fractions (m/z 14.5k and 20.4k) also present. As compared with the results from sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), these three fractions were identified as alpha-zeins (24.1k and 23.4k combined as Z19; 26.8k as Z22). When extracted with 55% aqueous 2-propanol, three alpha-zein fractions with m/z 26.8k, 24.1k, and 23.4k were predominant. When extracted with ethanol, extraction temperature had an effect on the final products. When extracted with 75% aqueous ethanol at room temperature, alpha-zein and some 17-18k species were observed, whereas at 60 degrees C, a small amount of delta-zein was also present. Comparison of the MALDI/MS results with SDS-PAGE and gene sequence analysis shows that the MALDI/MS method is superior to SDS-PAGE in having higher resolution and mass accuracy. 相似文献
6.
A modified procedure for the extraction of α‐zein from corn gluten meal was developed and compared against a commercial extraction method. The modification involved raising the concentration of alcohol in solvent and removing the precipitate by centrifugation. Five organic solvent mixtures were compared using the modified extraction procedure developed along with the reductant sodium bisulfite and NaOH. The modified procedure precipitated most of the non‐α‐zein protein solids by increasing the concentration of alcohol. The supernatant had α‐zein‐rich fraction, resulting in higher yield of α‐zein than the commercial method when cold precipitated. The commercial extraction procedure had a zein yield of 23% and protein purity of 28% using 88% 2‐propanol solvent. The three best solvents, 70% 2‐propanol, 55% 2‐propanol, and 70% ethanol, yielded ≈35% of zein at protein purity of 44% using the modified extraction procedure. Zeins extracted using the novel method were lighter in color than the commercial method. Densitometry scans of SDS‐PAGE of α‐zein‐rich solids showed relatively large quantities of α‐zein with apparent molecular weights of 19,000 and 22,000 Da. The α‐zein‐rich solids also had small amounts of δ‐zein (10,000 Da) because it shares similar solubility properties to α‐zein. A solvent mixture with 70% 2‐propanol, 22.5% glycerol, and 7.5% water extracted significantly less zein (≈33%) compared to all other solvents and had α‐zein bands that differed in appearance and contained little to no δ‐zein. 相似文献
7.
Batch extraction of zein from dry‐milled whole corn with ethanol was optimum with 70% ethanol in water, an extraction time of 30–40 min, and temperature of 50°C. High yields (60% of the zein in corn) and high zein contents in the extracted solids (50%) were obtained at a solvent‐to‐solids ratio of 8 mL of 70% ethanol/g of corn. However, zein concentration in the extract was higher at lower ratios. Multiple extraction of the same corn with fresh ethanol resulted in a yield of 85% after four extractions, whereas multiple extractions of fresh corn with the same ethanol resulted in high (15 g/L) zein concentration in the extract. Optimum conditions for batch extraction of zein were 45°C, with 68% ethanol at a solvent‐to‐solids ratio of 7.8 mL/g for an extraction time of 55 min. Column extractions were also best at 50°C and 70% ethanol; a solvent ratio of 1 mL/g resulted in high zein concentrations in the extract (17 g/L) but yields were low (20%). 相似文献
8.
This study was conducted to improve yields and qualities of corn protein co‐products produced by the sequential extraction process (SEP), a process using ethanol to fractionate corn in producing fuel ethanol. A two‐stage extraction protocol was evaluated to recover zein and subsequently recover a glutelin‐rich fraction (GRF). After the simultaneous oil‐extraction and ethanol‐drying step of SEP, zein was extracted from the anhydrous‐ethanol‐defatted, flaked corn by using 70% (v/v) ethanol at 60°C for 1.5 hr in a shaking water bath. Zein was recovered by ultrafiltering and then drying in a vacuum‐oven. Zein yield was 65% of the available zein in the flaked corn. SDS‐PAGE band patterns of the recovered zein closely resembled that of commercial zein. After zein extraction, the GRF was extracted using 45% ethanol and 55% 0.1M NaOH at 55°C for 2 hr. The extract was concentrated by ultrafiltration and then freeze‐dried. GRF yield was ≈65% of the available protein. Freeze‐dried GRF contained 90% crude protein (db), which classified the protein as a protein isolate. As with the protein concentrate from the original SEP, the GRF isolate was highly soluble in water at pH ≥ 7, had good emulsifying and foaming properties, formed stable emulsions, and was heat‐stable. 相似文献
9.
Zeins were isolated from corn ethanol coproduct distiller's dried grains (DDG) and fractionated into α- and β γ-rich fractions. The effects of the ethanol production process, such as fermentation type, protease addition, and DDG drying temperature on zein recovery, were evaluated. Yield, purity, and molecular properties of recovered zein fractions were determined and compared with zein isolated from corn gluten meal (CGM). Around 29-34% of the total zein was recovered from DDG, whereas 83% of total zein was recovered from CGM. Process variations of cooked and raw starch hydrolysis and fermentation did not affect the recovery, purity, and molecular profile of the isolated zeins; however, zein isolated from DDG of raw starch fermentation showed superior solubility and film forming characteristics to those from conventional 2-stage cooked fermentation DDG. Protease addition during fermentation also did not affect the zein yield or molecular profile. The high drying temperature of DDG decreased the purity of isolated zein. SDS-PAGE indicated that all the isolated α-zein fractions contained α-zein of high purity (92%) and trace amounts of β and γ-zeins cross-contamination. Circular dichroism (CD) spectra confirmed notable changes in the secondary structure of α-zeins of DDG produced from cooked and raw starch fermentation; however, all the α-zeins isolated from DDG and CGM showed a remarkably high order of α-helix structure. Compared to the α-zein of CGM, the α-zein of DDG showed lower recovery and purity but retained its solubility, structure, and film forming characteristics, indicating the potential of producing functional zein from a low-value coproduct for uses as industrial biobased product. 相似文献
10.
《Cereal Chemistry》2017,94(4):693-698
The high cost of kafirin and zein restricts their use for bioplastic and food applications. Effective, simple, and rapid kafirin/zein isolation processes are required. Here a percolation‐type aqueous ethanol solvent extraction process from coarse meals (grits) and coarse sorghum distillers dried grains and solubles (DDGS) for kafirin and zein isolation employing a low ratio of extractant to meal (2.5:1) was investigated, which is potentially applicable in the grain bioethanol industry. Postextraction filtration times were more than twice as fast using coarse meals compared with fine flours. Washing the meals prior to extraction to remove starch improved protein preparation purity to 73–85% compared with 68–72% for unwashed meals. Hence, no subsequent filtration or centrifugation step is required to clean up the kafirin/zein solution prior to solvent evaporation. With a single extraction step, kafirin/zein yields were 48% (protein basis) for DDGS and 53–70% for washed sorghum/maize meals. Cast films were used as a model bioplastic system to evaluate extracted kafirin/zein functional properties. DDGS kafirin films had rough surfaces but had the lowest water uptake and in vitro digestibility, owing to heat‐induced disulfide crosslinking during DDGS processing. Extraction by percolation using coarse meal/DDGS has potential to improve kafirin/zein viability. 相似文献
11.
Corn gluten meal is a high‐protein product from wet milling of corn. Substitution of 15% of the flour weight by corn gluten meal increased protein content of brownies from 6.3 to 8.0%. Sensory evaluation of brownies with 0, 10, and 15% corn gluten meal, with and without an added masking agent, showed addition of corn gluten meal to brownies did not have any detrimental effect as judged by trained sensory panelists. 相似文献
12.
Adhesive properties on glass of commercial zein and an inexpensive zein-lipid mixture isolated from dry-milled corn were investigated. A method was developed for uniformly preparing bonded glass panels and measuring the amount of pull required to separate the panels. The adhesive strength of commercial zein to glass was greater at 29% than at 52% relative humidity (RH). Bonded samples prepared from zein isolates were less sensitive to changes in RH. Bonds using commercial zein formulations containing plasticizer reached a maximum strength at 10% poly(ethylene glycol) regardless of RH. Formulations that required the least amount of ethanol (35-42%) were obtained by adjusting its pH to 3 or 10 with a volatile acid or base. These formulations completely bonded to the glass panels at low sample concentrations as estimated by 100% cohesive failure and exhibited lower Young's Modulus values than most of the other bonding materials tested. Samples bonded with a polyvinyl acetate emulsion adhesive were not as strong as the zein-bonded samples and were sensitive to changes in RH. 相似文献
13.
L. C. Dickey M. F. Dallmer E. R. Radewonuk N. Parris M. Kurantz J. C. Craig 《Cereal Chemistry》1998,75(4):443-448
Corn particles were extracted in an agitated vessel with a 4:1 mass ratio of 70% ethanol to corn for periods of 1–6 hr at ambient temperature. The extract solution was filtered and centrifuged to remove suspended particles after extraction and then diluted to 40% ethanol to precipitate extracted solute. Measurements of the mass of suspended particles separated by centrifugation indicate that mixing the corn particles with the ethanol dissolves and weakens the protein between cells and between starch granules within cells near the particles' surface. Under the conditions of this study, corn particles release starch granules more rapidly than the protein bodies dissolve, as indicated by analysis of the centrifuged particles. The diffusion coefficient for ethanol solution in corn was estimated and compared with a coefficent derived from a fit of the trend in the rate of release of fine particles from the milled corn. The diffusion coefficient of pure zein in a stagnant 70% ethanol solution was estimated from the measurement of weight loss by a ball of zein. Analysis of the ambient temperature protein extraction rate indicates that 2-mm particles exhibit more convective mass transfer than 20-μm particles. 相似文献
14.
Zein, extracted from underutilized corn gluten meal may serve as an alternative starting material for fabrication of biodegradable packaging. Zein plasticized with oleic acid may be formed into flexible and water‐resistant sheets. Our objective was to investigate the effect of plasticization on thermal behavior of zein sheets employing differential scanning calorimetry (DSC). Zein sheets were rolled from a resin prepared by dispersing zein and oleic acid in aqueous alcohol followed by the recovery of the formed moldable compound by precipitation with water. Sheets were later replasticized with additional oleic acid to increase ductility. DSC thermograms were used to investigate zein‐oleic acid interactions in zein sheets. DSC endotherms were attributed to melting of free oleic acid or to the dissociation of zein‐oleic acid bonds. Plasticized sheets contained bound and free oleic acid. Further heat‐treatment of plasticized sheets apparently resulted in zein absorption of free oleic acid. However, high temperatures were believed to cause dissociation of some zein‐oleic acid bonds formed during replasticization. 相似文献
15.
Parris N Dickey LC Powell MJ Coffin DR Moreau RA Craig JC 《Journal of agricultural and food chemistry》2002,50(11):3306-3308
Dry-milled yellow corn and freshly ground food and nonfood grade yellow and white hybrid corn kernels were pretreated in a solution of lactic acid and sodium metabisulfite followed by extraction with 70% ethanol. Zein was precipitated from the extract by reducing the ethanol content of the extract to 40%. Lipid associated with the zein isolates was between 15 and 20% and contained mostly endogenous free fatty acids. The effect of the endogenous free fatty acids on zein isolate films, with and without free fatty acids, was determined by measuring various film properties. Stress-strain measurements indicated 40-200% greater elongation for zein films containing endogenous free fatty acids. Films prepared from zein isolated from preground corn stored for approximately 4 months (27 degrees C, 17% relative humidity) had approximately 3 times greater elongation values than zein films prepared from freshly ground corn. 相似文献
16.
The strength of films extruded from powder blends of corn zein or corn gluten meal (CGM) with low‐density polyethylene was investigated. Tensile strength, percent elongation at break, and elastic modulus of the extruded films were measured. The tensile strength decreased from 13 MPa to ≈10.5 MPa with zein addition, while CGM addition resulted in tensile strength of ≈6 MPa. The higher the level of biological material (CGM or zein) in the films the lower the tensile properties. Films containing CGM exhibited significantly lower tensile properties than those containing zein. Extrusion processing of biological films is a step toward commercial viability. 相似文献
17.
Spaghetti was prepared by replacing either 5 or 10% semolina or farina with corn gluten meal, a high-protein fraction from the wet milling of corn, to increase the protein content of pasta. Spaghetti fortified with corn gluten meal had a similar cooked weight and cooking loss but was less firm compared with the control. The overall flavor quality score of the spaghetti decreased with the increasing additions of either water-washed, water/ethanol-washed or regular corn gluten meal because of the higher intensity of the fermented flavor. Spaghetti with acceptable quality can be prepared with 5% water/ethanol-washed corn gluten meal, thereby improving its nutritional value while providing an additional market for corn gluten meal. 相似文献
18.
Corn distillers' grains with solubles (CDGS), the major coproduct of fermentation of corn to produce ethanol, were extracted with 0.1M NaOH, 0.1% dithiothreitol (DTT), and 0.5% SDS yielding 35% of the total nitrogen and ≈25% of the protein nitrogen. Gel electrophoresis revealed that the extractable proteins contained zein plus other proteins similar to the extractable proteins from corn flour. Although difficult to extract, the proteins isolated from the fermentation coproducts appeared undegraded and apparently survived gelatinization, fermentation, distillation, and drying during the production of ethanol. Extraction of CDGS with 60% ethanol at 60°C yielded 1.5–3.9% of crude zein. When the ethanol contained DTT, yields of crude zein were increased to 3.2–6.6%. Protein contents of the crude zeins were only 37–57%, indicating that lipids and pigments were coextracted with the ethanol. Gel electrophoresis showed that the protein fractions extracted by ethanol contained primarily α-zein whereas the proteins extracted by ethanol + DTT contained α- + β-zein. Further confirmation of the presence of zein in the crude prolamin preparations was obtained by amino acid analyses. The amino acid compositions of the crude zeins paralleled those of commercial zein and α-zein. 相似文献
19.
Production of corn gluten meal (CGM), a high‐protein coproduct from wet milling of corn, is increasing as production of fuel ethanol from corn increases. Unpleasant taste and odor have limited the use of CGM in human food. Adjustment of pH and extraction with water have been reported to reduce the off‐flavor of CGM but the improvement is not enough for substantial addition of CGM to the human diet. More study of CGM is needed. In this study, volatile compounds released under different conditions of pH, water extraction, and temperature were identified and compared using solid‐phase microextraction‐gas chromatography‐mass spectrometry (SPME‐GC‐MS). The water‐extractable portion, which improves the taste of CGM by its absence, was dried and analyzed by SPME‐GC‐MS. In addition, materials extractable from CGM with methylene chloride were identified by gas chromatography‐mass spectrometry (GC‐MS). Further, the spontaneous generation of a CGM‐like odor accompanied by a change in physical appearance of the CGM sample was described. Flavors and odors known to be associated with the identified CGM compounds were listed. Some possible origins of the volatiles, from degradation of corn constituents or as fermentation products of the corn steeping process, were noted. 相似文献
20.
An acidic method of zein extraction from DDGS 总被引：3，自引：0，他引：3
Zein with a higher intrinsic viscosity and phosphorus content, similar protein content, lower yellowness, and at potentially much lower cost than commercially available zein was obtained from distillers dried grains with solubles (DDGS). A novel extraction method using acidic conditions in the presence of a reducing agent has been used to obtain about 10% aqueous ethanol soluble zein from DDGS. The optimum pH, time, temperature, and amount of reducing agent that can produce zein with high quality and yield have been developed. In addition to the zein, about 17% oil based on the dry weight of DDGS has also been obtained during zein extraction. The zein obtained from this research is expected to be suitable for use as fibers, films, and binders and in paints. 相似文献