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1.
Yellow dent corn soaked in deionized water at 52°C for 24 h without addition of SO2 was wet‐milled using a modified 100‐g laboratory procedure employing ultrasound treatment at different points in the milling process and compared to conventional wet milling and milling‐only corn. Starch yields from ultrasound treatments varied from 66.93 to 68.72% and were comparable to conventional wet milling (68.92%). The ultrasound treated samples produced 6.35 to 7.02 more percentage point starch compared to the milling‐only corn. Compared to the starch from milling‐only corn, the ultrasound‐produced starches showed a significant increase in whiteness and decrease in yellowness that are comparable to starches produced by conventional wet milling. Ultrasound treatment after the second grinding produced the highest starch yield and the lowest protein content in the resulting starch. The ultrasound‐treated starches exhibited different pasting properties as evidenced by higher paste viscosities. 相似文献
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Abdulvahit Sayaslan 《LWT》2004,37(5):499-515
Commercial manufacture of wheat starch and vital wheat gluten involves physical separation of starch granules and gluten particles formed in a neutral aqueous system. The wet-separation of gluten proteins and starch from wheat flour is based on their water insolubility, density, and particle size. Upon wetting, gluten proteins in wheat endosperm aggregate and form particles that are larger in size but less dense than starch granules. Wheat starch and vital gluten are currently produced industrially through wet-milling of wheat flour principally by four processes; the Martin, Alfa-Laval/Raisio, Hydrocyclone, and the High-Pressure Disintegration (HD) processes. The industrial processes differ mainly in the forms of the flour-water mixtures presented to the fractionation equipment (centrifuge, hydrocyclone, or screen) or in the initial separation practice of starch and gluten fractions from flour. However, the processes essentially merge into one as the intermediate starch and gluten-particle streams are purified to give >98% pure starch and ∼80% protein vital gluten. Handling of a second-grade starch stream, flour water-soluble, and fibrous residues may differ at various processing steps. Small-scale tests are available to assess the wet-milling quality of flours to be wet-processed by the Martin, Batter, Alfa-Laval/Raisio, and the HD processes. Yet, there are no laboratory tests reported for the Hydrocyclone process. Given the development of numerous new wheat varieties each year and of high-amylose and waxy wheats, it is important that small-scale wet-milling tests to assess the wet-milling quality and suitability of flour samples for the industrial processes be available. 相似文献
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吸水率是谷朊粉品质的一项重要指标。通过不同方法对谷朊粉吸水率进行测定,对比分析不同测定方法和不同颗粒度对吸水率的影响,结果表明:手工法测定出的吸水率最高,在一定范围内吸水率随颗粒度的减小而增大,在同一吸水率情况下,硬质麦与软质麦相比,其湿面筋数要高于软质麦。 相似文献
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Field peas from two cultivars were dehulled and groats were processed by two protocols: (1) groats directly ground with water into a slurry and fractionated into fibre, protein and starch concentrates (groat wet fractionation, GWF), and (2) groats dry milled into flour and then wet fractionated using steps identical to that of protocol-1 (flour wet fractionation, FWF). The yield (%, w/w) and composition (%, w/w) of starch, protein and fibre concentrates from both protocols were determined. The data indicated that the FWF had significantly higher starch yield when compared to GWF. Scanning electron micrographs clearly suggested that better tissue fragmentation caused by dry milling may be responsible for better starch yield in FWF. The purity of starch isolate from FWF was lower than that of GWF. Brabender viscoamylographs showed differences in pasting properties of starches between protocols. Furthermore, the effect of sonication on starch yield and purity was studied between two wet fractionations. A combination of FWF with the sonication at 75% amplitude for 10 min showed better starch yield. 相似文献
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Experimental lines of hybrid grain sorghums were produced with thousand‐kernel‐weights (TKW) varying between 23.1–44.9 g. The proportion of germ in the normal‐seeded hybrids with TKW 23–27 g was ∼ 9.9–10.2% of dry kernel weight, whereas that in the large‐seeded hybrids with TKW 37–45 g was ∼ 10.8–11.2%. Starch in grain decreased ∼ 4% as kernel weight increased which was offset by an increase in protein level. Wet‐milling of the grain was done without steeping after an initial coarse‐grinding step in two parts of water with 0.3% sodium bisulfite. Three of four samples of large‐seeded and soft‐textured grain sorghums gave 77–82% recovery of starch with 0.5–0.7% protein, while one gave 59% recovery and 0.6% protein. The starches had < 0.5% damaged starch, gave no rancid off‐odor after storing 26 months at 25°C in a sealed glass container, and had lightness (L*) values of 93.1–93.7 vs. 95.2 for a commercial corn starch. Their pasting curves were similar to that of commercial corn starch. The bran/germ/endosperm fraction obtained by limited wet‐milling of one large‐seeded hybrid was separated by flotation to recover one‐half the germ in 98% purity as estimated by fat content. 相似文献
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Separation of wheat flour into its constituents starch and gluten was studied using a cone-cone shearing device, with emphasis on the effect of rotation rate, processing time, temperature and water content. This study confirms the two step mechanism previously proposed for the gluten migration: aggregation of gluten protein into gluten domains that subsequently migrate to the apex of the cone. The results show that optimal process conditions for gluten migration are different from the process conditions for gluten aggregation. While gluten agglomeration (step 1) benefits from high temperature, low rotation rate and high water content, gluten migration (step 2) is positively influenced by a high dough viscosity and higher rotation rate. 相似文献
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糯玉米淀粉提取及理化性质的研究 总被引：9，自引：0，他引：9
以糯玉米为原料，采用湿法提取淀粉工艺，制得淀粉得率高，质量优质的纯净糯玉米淀粉，通过正交实验设计筛选出最佳的提取方案：浸泡温度，浸泡溶液亚硫酸浓度，浸泡时间分别为50℃，0．3％，60h，影响淀粉得率的主要因素是：时间，浓度，温度，糯玉米淀粉较普通玉米淀粉相比具有糊化温度低，黏度高，透明度高等特点。 相似文献
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Andreas Blennow Anne Mette Bay‐Smidt Peter Leonhardt Ole Bandsholm Marianne H. Madsen 《Starch - St?rke》2003,55(9):381-389
The correct choice of selection and quality criteria is critical for most starch applications. In this study, a set of different potato starches, selected for a large variation in natural phosphate content and final viscosity, was cationised and tested in a laboratory scale wet‐end paper manufacturing process. Analysis of further parameters expected to be critical for processing, including amylose content and starch granule size, was also performed. Since no significant correlation was found between any of these parameters and paper processing, further attempts were made to find structural or physico‐chemical explanations for the paper processing performance. Hence, several additional parameters of the starches were determined including amylopectin chain length pattern, phosphate substitution, molecular size distribution, pasting‐texture properties and fragility of the gelatinised granules. Among these parameters, the best correlation found to paper filler retention was stickiness of the starch as measured by texture analysis. The starches that performed best in the paper trials showed rapid granule bursts that could be readily estimated from the width of the pasting curve peaks. Light microscopy of non‐soluble remnant starch obtained after gelatinisation of starch under dilute conditions revealed a high proportion of broken granular structures. It is hypothesised that the degree of phosphorylation, together with a hitherto unknown molecular parameter that is related to starch granule fragility, determines starch paste stickiness, which in turn is an important parameter for wet‐end paper manufacturing. 相似文献
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Dispersions of wheat gluten were prepared at different pHs (4, 6 and 11) in the presence or absence of ethanol. Films were obtained after casting suspensions followed by evaporation of the solvent. Films prepared at pH 11 were significantly stronger than the films prepared at pH 4 and 6 with tensile strengths of approximately 7 vs. 2 MPa. With increasing strength, the elongation at break was moderately reduced from approximately 300% to 190%. No significant variations of water vapour transfer rate properties were observed among the films. The solubility of gluten films in aqueous and 1.5% sodium dodecyl sulfate (SDS) solution decreased with increasing pH of films. Tricine sodium dodecyl sulfate‐polyacrylamide gel (SDS‐PAGE) patterns of wheat gluten and film showed the formation of high molecular weight fractions. The amount of free amino groups in the wheat gluten decreased during film formation. Amino acid analysis showed the presence of lysinoalanine (LAL). All these results indicate the formation of irreversible intermolecular cross‐linking upon film formation at pH 11. 相似文献
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Sabah Al‐Abbas Tatiana Y. Bogracheva Ian O. Topliff Iain Crosley Cliff L. Hedley 《Starch - St?rke》2006,58(1):6-17
Methods for milling and separation of flour from seeds of a normal (wild‐type) and two mutant (lam and r) types of pea (Pisum sativum L.) into starch‐rich and protein‐rich fractions are described. The methods entail using combinations of mills (100AFG, 50ZPS and 100UPZ) together with an air‐classification system based on a 50ATP air‐classifier, all run under a range of conditions to optimise the separation. The efficiency of separation was assessed as well as the economic advantages of the different systems. The best route for separation and fractionation was 2×100UPZ + 100AFG + 50ATP, while the most economic system that also gave good separation and fractionation was 2×100UPZ + 50ZPS + 50ATP, which had an energy consumption of 226 kWh/t. A novel method for determining the starch content within the high and low starch fractions is described. The method is based on a comparison between the gelatinisation enthalpy of starch in starch‐rich and in protein‐rich fractions with that for pure starch produced from the same flour, using differential scanning calorimetry. Qualitative assessments of the starch contents of the fractions were also made using microscopy and particle size distribution analysis. It is suggested that the starch‐rich fractions could be used as a relatively cheap raw material for non‐food applications. 相似文献
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采用乙酸酐对小麦面筋蛋白质进行酰化改性 .结果表明 :小麦面筋蛋白质乙酰化的最佳反应条件为面筋蛋白质质量分数 5 % ,反应温度 35℃ ,乙酰酐用量为小麦面筋蛋白质用量的 15 % ;乙酰化改性后的面筋蛋白质 ,溶解度、乳化能力和起泡能力均得到了提高 ,乙酰化小麦面筋蛋白质对弱筋粉粉质特性的改善效果强于普通谷朊粉 . 相似文献
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Structural and physicochemical characteristics of cassava starch treated with 0.36% HCl in anhydrous ethanol during 1 and 12 h at 30, 40, and 50°C followed by ball milling for 1 h were analyzed. Average yield of acid‐ethanol starches reached 98% independent of the treatment conditions. Solubility of acid‐ethanol starches increased with reaction temperature and time, but it did not change after ball milling. Granule average size reduced with chemical treatment from 25.2 to 20.0 µm after 12 h at 50°C. Ball milling decreased the granule average diameter of the native starch and those chemically treated at 30°C/1 h or 40°C/1 h, but it did not alter the starches treated for 12 h, independent of temperature. From scanning electron microscopy (SEM), starch granules presented round shape and after modification at 50°C/12 h, before and after ball milling, showed a rough and exfoliated surface. Some granules were deformed, suggesting partial gelatinization that was more intense after milling. Starch crystallinity increased as temperature and time of chemical treatment were increased, while amylose content, intrinsic, and pasting viscosities decreased. Gelatinization temperatures increased for all chemical starches. The findings can be related to the preferential destruction of amorphous areas in the granules, which are composed of amylose and amylopectin. After ball milling, the starch crystallinity decreased, amylose content, intrinsic, and pasting viscosities kept unchanged and gelatinization temperatures and enthalpy reduced. Ball milling on native and chemical starches caused the increase of amorphous areas with consequent weakening and decreasing of crystalline areas by breaking of hydrogen bonds within the granules. 相似文献
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Short‐time and no‐time steeping were used in the wet‐milling of grain sorghum to give two products, starch in over 78% recovery (starch basis) plus the remaining grain solids. In the wet‐milling process 1.5 parts of fresh water were used per part of grain to compensate for drying and transfer losses. Starting with 100 g (dry solids) of commercial No.2 grain sorghum, steep time (1—3 h), steep temperature (25—60 °C), and coarse‐grinding speed (7, 500—12, 500 rpm with tip speed of 90.4—150.7 km/h) were varied in a model study; starch recovery, starch lightness (L*), and damaged starch were the responses. Grain sorghum was steeped with twice its weight of process water containing 0.2% sulfur dioxide and the steeped kernels were added to an equal volume of process water and the mixture was ground for 6 min in a Waring blender with blunt blades (d = 3.2 cm). The course‐ground material was sieved (opening 1190 μm) to collect the bran/germ, and the throughs were allowed to stand. The sedimented phase was finely ground by one pass through a plate mill, and the fine fiber removed by sieving (opening 73 μm). The slurry was adjusted to a specific gravity of 1.04, and the starch was separated from the protein fraction on a starch table. The protein fraction was combined with the steep‐liquor concentrate (54% solids) plus the bran/fiber and the fine‐fiber fractions to give the co‐product, which contained 70% moisture (wet basis, wb) and 27% protein (dry basis, db). In the surface response study, recovery of starch ranged from 57 to 89%, starch protein content from 0.4 to 0.5%, and lightness (L*) from 90 to 93. Damaged starch content was constant at around 0.4%. Commercial grain sorghum gave the highest starch recovery (90%) after steeping 2 h at 55 °C and coarse‐grinding at 10, 500 rpm; whereas a food‐grade, a white and a red sorghum gave 85, 84, and 80% recoveries, respectively. The four starches had lightness (L*) values of 93—94 and damaged starch contents of 0.4—0.6%. When the commercial grain sorghum was wet‐ground without steeping in 2 parts of water containing 0.2% sulfur dioxide, a 78% recovery of starch was obtained with L* 93.7 and starch damage 0.5%. 相似文献
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Juliet A. Gerrard Rebecca C. Abbot Marcus P. Newberry Margy J. Gilpin Marcela Ross Sin E. Fayle 《Starch - St?rke》2001,53(6):278-280
As part of our studies on the mechanisms of bread staling, starch bread was used as a research tool that enables us to gain insights into the individual contributions that starch and gluten have on staling. Reconstitution experiments have demonstrated that bread of equivalent specific loaf volume stales at the same rate irrespective of protein concentration, or type of protein. However, other properties of bread, such as specific loaf volume, may be altered by specifically changing the protein component in the flour. 相似文献
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The effects of a commercial cell‐wall‐degrading enzyme (CWDE) complex and/or commercial protease on yield and quality of starch extracted from white regular sorghum (RSOR), white waxy sorghum (WSOR) and yellow maize (YMZ) were determined. A bifactorial experiment with a level of confidence of P<0.05 was performed to study the effect of CWDE and/or protease addition to coarsely ground grains for 4 h after 20 h of regular SO2 steeping of whole kernels. Calcium oxide (CaO) or lactic acid were used to adjust the pH solution to 5.5 prior to grinding. YMZ yielded the highest amount of starch, whereas RSOR gave higher starch yield than WSOR. All enzyme treatments significantly (P<0.05) improved starch yields. Protease alone and CWDE plus protease treatments were the most effective treatments in terms of starch yields. These enzyme treatments allowed the recovery of more than 90% of the starch. The two types of sorghum starches contained higher amounts of residual protein and ash when compared with maize starch. The various enzymes treatments did not affect starch composition or Visco Analyser properties of each type of kernel. As expected, the WSOR starch had lower pasting temperature and retrogradation when compared with the regular starches. 相似文献