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1.
Baks T Bruins ME Matser AM Janssen AE Boom RM 《Journal of agricultural and food chemistry》2008,56(2):488-495
Enzymatic hydrolysis of starch can be used to obtain various valuable hydrolyzates with different compositions. The effects of starch pretreatment, enzyme addition point, and hydrolysis conditions on the hydrolyzate composition and reaction rate during wheat starch hydrolysis with alpha-amylase from Bacillus licheniformis were compared. Suspensions of native starch or starch gelatinized at different conditions either with or without enzyme were hydrolyzed. During hydrolysis, the oligosaccharide concentration, the dextrose equivalent, and the enzyme activity were determined. We found that the hydrolyzate composition was affected by the type of starch pretreatment and the enzyme addition point but that it was just minimally affected by the pressure applied during hydrolysis, as long as gelatinization was complete. The differences between hydrolysis of thermally gelatinized, high-pressure gelatinized, and native starch were explained by considering the granule structure and the specific surface area of the granules. These results show that the hydrolyzate composition can be influenced by choosing different process sequences and conditions. 相似文献
2.
An enzymatic method based on hydrolysis of starch by amyloglucosidase and measurement of d-glucose released by glucose oxidase-peroxidase was developed to measure both gelatinized starch and hydrolyzable starch in situ of dried starchy products. Efforts focused on the development of sample handling steps (particle size reduction of dry samples followed by a unique mechanical resolubilization step) prior to the enzymatic hydrolysis using native and fully gelatinized flours of corn and rice. The new steps, when optimized, were able to maximize resolubilization of gelatinized/retrograded starch while minimizing solubilization of native starch in dried samples, thus effectively addressing issues of insusceptibility of retrograded starch and susceptibility of native starch to enzymatic attacks and eliminating the need to isolate starch from dry samples before using an enzymatic method. Various factors affecting these and other steps were also investigated, with the objectives to simplify the procedures and reduce errors. Results are expressed as the percentage of the total starch content. The proposed method, verified by measuring mixed samples of native and fully gelatinized flours of five grain species (corn, rice, barley, oat, and wheat) at different ratios, is simple, accurate, and reliable, with a relative standard deviation of less than 5%. 相似文献
3.
Native starch granules of 11 selected cultivars (potato, waxy potato, sweet potato, normal maize, high‐amylose maize, waxy maize, wheat, normal barley, high‐amylose barley, waxy barley, and rice) were treated with a calcium chloride solution (4M) for surface gelatinization. The surface‐gelatinized starch granules were investigated using light microscopy and scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). In general, those starches with larger granule sizes required longer treatment time to complete the gelatinization. The salt solution treatment of starch was monitored by light microscopy and stopped when the outer layer of the granule was gelatinized. The surface gelatinized starch granules were studied using scanning electron microscopy. On the basis of the gelatinization pattern from calcium chloride treatments, the starches could be divided into three groups: 1) starches with evenly gelatinized granule surface, such as normal potato, waxy potato, sweet potato, maize, and high‐amylose maize; 2) starches with salt gelatinization concentrated on specific sites of the granule (i.e., equatorial groove), such as wheat, barley, and high‐amylose barley; and 3) starches that, after surface gelatinization, can no longer be separated to individual granules for SEM studies, such as waxy barley, waxy maize, and normal rice. The morphology of the surface gelatinized starch resembled that of enzyme‐hydrolyzed starch granules. 相似文献
4.
The water dynamics and retrogradation kinetics behavior of gelatinized wheat starch by either ultrahigh pressure (UHP) processing or heat are investigated. Wheat starch completely gelatinized in the condition of 90, 000 psi at 25 degrees C for 30 min (pressurized gel) or 100 degrees C for 30 min (heated gel). The physical properties of the wheat starches were characterized in terms of proton relaxation times (T2 times) measured using time-domain nuclear magnetic resonance spectroscopy and evaluated using commercially available continuous distribution modeling software. Different T2 distributions in both micro- and millisecond ranges between pressurized and heated wheat starch gels suggest distinctively different water dynamics between pressurized and heated wheat starch gels. Smaller water self-diffusion coefficients were observed for pressurized wheat starch gels and are indicative of more restricted translational proton mobility than is observed with heated wheat starch gels. The physical characteristics associated with changes taking place during retrogradation were evaluated using melting curves obtained with differential scanning calorimetry. Less retrogradation was observed in pressurized wheat starch, and it may be related to a smaller quantity of freezable water in pressurized wheat starch. Starches comprise a major constituent of many foods proposed for commercial potential using UHP, and the present results furnish insight into the effect of UHP on starch gelatinization and the mechanism of retrogradation during storage. 相似文献
5.
Starch suspensions (0.25%) were gelatinized to 70 and 100°C, and starch ghosts (defined as gelatinized starch granule envelopes after the majority of internal starch polymers have been released) and remnants were collected by centrifugation and washed with water. Protein was revealed in isolated gelatinized normal starch ghosts using confocal laser scanning microscopy and a protein‐specific dye that fluoresces only after reaction with primary amines in protein. This technique eliminates background interference from residual dye. Observation of fluorescent‐labeled protein in the starch ghosts at different optical depths of field revealed that protein was concentrated in the envelopes of swollen, gelatinized potato, maize, and wheat starch ghosts. Only traces of protein were found in gelatinized starch granule remnants of waxy maize and amylose‐free potato starches after they were heated to 100°C, indicating that the proteins observed in gelatinized normal maize starch were largely granule‐bound starch synthase (GBSS). Moreover, fragility of the gelatinized waxy and amylose‐free starch granule remnants might be caused in part by the lack of GBSS. Gel electrophoresis of proteins in starch ghosts confirmed that GBSS in potato and maize was tightly associated with the starch ghosts. The study provides a structural explanation for a role of granule‐associated proteins in maintaining the integrity of starch ghosts and remnant structures, and their consequent effect on paste rheology. 相似文献
6.
Recently, we reported the development of an enzymatic corn wet‐milling process that reduces or eliminates sulfur dioxide requirements during steeping, considerably reduces steep time, and produces starch yields comparable to that of conventional corn wet‐milling. The best results so far, using the enzymatic corn wet‐milling procedure, were achieved when a particular protease enzyme (bromelain) was used. In this study, pasting properties and surface characteristics of starch obtained from six different enzyme treatments (three glycosidases [β‐glucanase, cellulase, and xylanase] and three proteases [pepsin, acid protease, and bromelain]) using the enzymatic corn wet‐milling procedure were evaluated and compared with those from starch obtained using the conventional corn wet‐milling procedure. Significant effects from enzymatic milling were observed on all the three starch pasting properties (peak, shear thinning, and setback). The setback viscosities of starch from all enzyme treatments were significantly lower compared with those of the control sample, indicating that starch polymers from enzymatic corn wet‐milling do not reassociate to the same extent as with the control. Comparison between bromelain treatment and the control sample showed that starch samples obtained from bromelain treatment are very similar to control starch in water‐binding capacity, molecular breakdown, and time to swell when cooked in water. Significant effects from enzymatic milling were observed on the surface characteristics of starch granules. The glycosidase treatments, especially the β‐glucanase samples, showed holes in the starch granules. No visual differences were observed in starch granules between bromelain and control samples. 相似文献
7.
水肥耦合条件下作物产量、水分利用和根系吸氮的试验研究 总被引：37，自引：6，他引：37
根据1998～2000年两年在北京市水科所永乐店节水灌溉中心开展的冬小麦、夏玉米水肥耦合的田间试验成果的分析研究表明，氮肥效益的发挥与农田水分状况密切相关，低供水水平时(本研究中为冬小麦仅灌拔节水的节水灌溉处理)，肥料的增产效益十分显著，但氮肥贡献率随施肥量的增加而呈递减的趋势。不同的分析方法都表明，在永乐店节水灌溉中心，冬小麦施尿素400 kg/hm2和200 kg/hm2两个施肥水平的试验处理所获得的水(肥)分生产率最高(在不同农田供水状况下)，由于两者的水分生产率差异不大，为提高施肥效率，建议在生产上考虑选择200 kg/hm2的施肥方案较合理。 相似文献
8.
《Cereal Chemistry》2017,94(4):645-653
This study aimed to investigate impacts of milling methods on ethanol production using an uncooked dry‐grind (cold fermentation) process and characterize residual starch in the distiller's dried grains (DDG) coproduct. Four corn lines with different chemical compositions were ground with cyclone, ultra‐centrifugal, or hammer mills equipped with a screen of 0.5 mm opening and used for the cold fermentation process. Greater starch hydrolysis and ethanol yield were obtained from cyclone‐milled corn, resulting from larger damaged starch contents and smaller particle sizes of the ground corn. Corn grains and ground corn after five‐month storage showed less starch hydrolysis than the freshly ground counterpart. Residual starch (2.8–8.0%) with large proportions of intact amylopectin contents (up to 42.5%) was found in the DDG from all types of milling. The results suggested that the entrapment of starch granules in ground corn and a low activity of amylolytic enzymes at a high ethanol concentration were accountable for the remaining of starch in the DDG. 相似文献
9.
10.
冻结-高压湿热解冻对多种淀粉中支链淀粉断裂的影响 总被引：2，自引：2，他引：0
冻结和高压湿热解冻是含淀粉面团在食品加工过程的必要工艺,在此过程中淀粉球破裂、部分支链淀粉断裂成为直链淀粉,给面团和食品的物理性状控制带来许多不可预见的结果。该文通过研究加热时间、加热温度、冷冻时间和解冻时间对糊化后的小麦、甘薯、马铃薯和玉米淀粉中直链淀粉含量的影响,间接反映支链淀粉断裂情况,结合冻结解冻前后淀粉分子量分布、链长分布、光学和电子显微镜图谱提出了冻结-解冻过程不同淀粉中支链淀粉可能断裂方式。结果表明,4种淀粉中的直链淀粉含量先升高后下降,直链淀粉含量在4种淀粉的中达到峰值的时间分别为48,48,48,72 h。光学显微照片观察表明,冻融处理会导致更多凝胶化淀粉球的破裂。对于小麦支链淀粉,冻融解冻过程支链淀粉中侧链长度为5、6、7个葡萄糖残基的侧链对应3种可能的断裂方式:2+2+1、2+2+2及2+2+2+1;对于甘薯支链淀粉,支链淀粉中侧链长度为10、11和13个葡萄糖残基的侧链对应3种可能的断裂方式:3+3+4、2+2+3+4及2+2+2+3+4;对于马铃薯支链淀粉,支链淀粉中侧链长度为5和6个葡萄糖残基的侧链对应3种可能的断裂方式:2+3、2+4、3+3;而玉米支链淀粉中,支链淀粉中侧链长度为7、8、9个葡萄糖残基的侧链对应3种可能的断裂方式:2+5,3+5,和3+3+3(其中1表示1个葡萄糖;2表示含2个葡萄糖的麦芽糖、3表示含3个葡萄糖的麦芽多糖、4表示含4个葡萄糖的麦芽多糖和5表示含5个葡萄糖的麦芽多糖)。该论文结果为培育具有冻融稳定性的淀粉种子提供一种全新的思路,即通过基因方法控制植物减少容易断裂淀粉侧链的合成。 相似文献
11.
Effects of β-amylolysis on the resistant starch formation of debranched corn starches 总被引：1，自引：0，他引：1
Retrograded amylose is resistant to digestion by amylolytic enzymes, which is known as resistant starch type III (RS3). In this study we investigated the effect of β-amylase hydrolysis on the formation and physicochemical properties of RS3 from debranched corn starches. Three types of corn starch (Hylon VII, Hylon V, and common corn) were first gelatinized and then hydrolyzed using β-amylase to varying degrees. The resultant hydrolyzed starch was debranched with isoamylase and then exposed to temperature cycling to promote RS formation. A broad endotherm from approximately 45 to 120 °C and a small endotherm above 150 °C were noted for all retrograded starches. All three corn starches had increased RS contents after moderate β-amylolysis, with Hylon V having the highest RS content at 70.7% after 4 h of β-amylolysis. The results suggest that RS3 formation is affected by the starch composition as well as the starch structure and can be increased by moderate β-amylolysis. 相似文献
12.
Ping Wang Vijay Singh Hua Xue David B. Johnston Kent D. Rausch M. E. Tumbleson 《Cereal Chemistry》2007,84(1):10-14
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. 相似文献
13.
红壤旱地肥力变化及有效施肥技术 总被引：10，自引：2，他引：8
红壤不施肥或施用单一营养元素化肥,连续种植,导致土壤肥力下降;施用氮磷钾化肥,有一定增产效果,连续种植导致部分中量元素和微量元素的亏缺。施用有机肥配合施用化肥,保证了作物高产稳产,是培肥土壤的主要途径。 相似文献
14.
Liming Cai Induck Choi Jong‐Nae Hyun Young‐Keun Jeong Byung‐Kee Baik 《Cereal Chemistry》2014,91(1):65-71
The influence of bran particle size on bread‐baking quality of whole grain wheat flour (WWF) and starch retrogradation was studied. Higher water absorption of dough prepared from WWF with added gluten to attain 18% protein was observed for WWFs of fine bran than those of coarse bran, whereas no significant difference in dough mixing time was detected for WWFs of varying bran particle size. The effects of bran particle size on loaf volume of WWF bread and crumb firmness during storage were more evident in hard white wheat than in hard red wheat. A greater degree of starch retrogradation in bread crumb stored for seven days at 4°C was observed in WWFs of fine bran than those of coarse bran. The gels prepared from starch–fine bran blends were harder than those prepared from starch–unground bran blends when stored for one and seven days at 4°C. Furthermore, a greater degree of starch retrogradation was observed in gelatinized starch containing fine bran than that containing unground bran after storage for seven days at 4°C. It is probable that finely ground bran takes away more water from gelatinized starch than coarsely ground bran, increasing the extent of starch retrogradation in bread and gels during storage. 相似文献
15.
Enrique Corts‐Ceballos Esther Prez‐Carrillo Sergio O. Serna‐Saldívar 《Cereal Chemistry》2015,92(1):88-92
Double mashing for wort production is a time‐consuming process that can be reduced if pregelatinized adjuncts are used. Optimal extruding conditions were determined to obtain brewing adjuncts from corn and sorghum starch. For corn starch extrusion, a Box–Behnken design was devised in which moisture, screw speed, temperature of the barrel, and concentrations of sodium stearoyl lactylate (SSL) were varied, and sorghum starch was extruded according to a 23 model in which the modified variables were moisture, SSL concentration, and temperature. The aim was to maximize starch damage and minimize resistant starch and final viscosity as determined with a Rapid Visco Analyzer. The treatments that satisfied these requirements were mashed, and wort extract yield was determined. Glucose, maltose, and maltotriose concentrations in the resulting worts were determined by HPLC with a refractive index detector. Feedstock tempering and SSL content were the most important factors affecting the response; for corn starch, treatments with lower moisture (20%) and middle levels of SSL (0.5%) or with high levels of both moisture (40%) and SSL (1%) produced the most desirable samples for mashing, whereas for sorghum starch the best treatment was tempering to 20% moisture and containing middle levels of SSL (0.5%). No statistical differences were found between these experimental treatments and the control. 相似文献
16.
玉米秸秆粉碎还田+旋耕播种是晋西南小麦玉米一年两熟区小麦季的主要栽培模式,冬前灌水可塌实土壤、加快秸秆腐熟、确保小麦安全越冬。为探明合理运筹越冬水对培育冬前壮苗、增加小麦产量、提高籽粒水分利用率的影响,在山西省临汾市尧都区,设置4个冬小麦冬前灌水时间处理,分别为11月10日、11月25日、12月10日和12月25日,以冬小麦传统灌冬水时间(12月10日)为对照(CK),研究冬前灌水时间对冬小麦冬前群体茎数、根系、旗叶光合性能和土壤容重、酶活性影响。结果表明:与不灌冬水的处理相比,冬前灌水可塌实耕层土壤、调节土壤容重,利于小麦根系与土壤紧密接触,增强土壤酶活性、提高土壤肥力,促进冬小麦分蘖和次生根的发生。与传统冬前灌水时间(12月10日)相比,冬水前移对小麦生长有补偿作用,使冬前总茎数、单株茎数、次生根数、根干重增加,延长了旗叶的功能期,提高了叶绿素含量和光合速率,促进光合产物的合成转化,使成穗数增加1.66%~5.37%,千粒重增加0.55%~3.03%。玉米秸秆粉碎还田+旋耕播种条件下,小麦冬前灌水时间由传统昼消夜冻(12月10日)前移一个节气,即11月25日左右,主茎叶龄3叶到3叶1心的分蘖初期,可使小麦增产8.40%,水分利用效率提高5.76%,达22.05 kg·mm~(-1)·hm~(-2)。 相似文献
17.
Cruz-Orea A Pitsi G Jamée P Thoen J 《Journal of agricultural and food chemistry》2002,50(6):1335-1344
We report high-precision measurements of phase transitions in the starch-water system by using for the first time adiabatic scanning calorimetry (ASC). Potato starch and nixtamalized corn flours were studied by this technique as a function of the moisture content. We calculated the percentage of gelatinized starch granules, as a function of the temperature, for both flours. For bi-phasic behavior in potato starch, at intermediate water contents, we propose an explanation based on previous hypotheses and on the experimental behavior as deduced from ASC measurements. ASC results suggest, in the case of nixtamalized corn flour, that uniform moisture is present in corn starch granules for all the considered moistures. A shift to higher temperatures of the peak temperature is observed when comparing the c(p)(T) curves with the classical DSC endotherms as measured for this flour. For both flours we estimated from the ASC results the melting temperatures of the starch granules, at zero moisture content, by using Flory's equation. 相似文献
18.
J. A. Lacerenza J. M. Martin L. E. Talbert S. P. Lanning M. J. Giroux 《Cereal Chemistry》2008,85(3):322-328
Production of fuel ethanol hinges on the availability of carbohydrate sources, with corn being the crop of choice in most areas. However, in some climatic regions, it is not feasible to grow adequate volumes of corn so other starch sources must be utilized. Here we examined various small grain crops commonly grown in the Northern Great Plains for suitability for ethanol production. Four cultivars each of the hexaploid wheat (Triticum aestivum L.) classes hard red spring (HRS), hard white spring (HWS), soft white spring (SWS), along with durum wheat (Triticum durum L.), and four spring barley (Hordeum vulgare L.) cultivars were grown in replicated plots in two environments in 2006. Agronomic and seed quality traits, along with starch content and ethanol yield over a period of 72 hr were measured on all cultivars. Agronomic yield was highest for the barley cultivars and lowest for HRS and HWS. Seed size was greatest for the durum and barley cultivars. The SWS group had the lowest protein content and the highest starch content. Starch content was highly correlated with final ethanol yield and the SWS group was highest in absolute ethanol yield. However, ethanol yield per hectare was highest for barley, with SWS ranking second, while the HRS and HWS groups had the lowest ethanol yields per hectare. The results indicate that selection for small grain ethanol yield should focus primarily upon agronomic yield at the expense of protein content. Traditional selection for high HRS and HWS milling and baking quality is not consistent with maximal ethanol yield per hectare. 相似文献
19.
X. Wu R. Zhao D. Wang S. R. Bean P. A. Seib M. R. Tuinstra M. Campbell A. O'Brien 《Cereal Chemistry》2006,83(5):569-575
The effects of amylose, protein, and fiber contents on ethanol yields were evaluated using artificially formulated media made from commercial corn starches with different contents of amylose, corn protein, and corn fiber, as well as media made from different cereal sources including corn, sorghum, and wheat with different amylose contents. Second‐order response‐surface regression models were used to study the effects and interactions of amylose, protein, and fiber contents on ethanol yield and conversion efficiency. The results showed that the amylose content of starches had a significant (P < 0.001) effect on ethanol conversion efficiency. No significant effect of protein content on ethanol production was observed. Fiber did not show a significant effect on ethanol fermentation either. Conversion efficiencies increased as the amylose content decreased, especially when the amylose content was >35%. The reduced quadratic model fits the conversion efficiency data better than the full quadratic model does. Fermentation tests on mashes made from corn, sorghum, and wheat samples with different amylose contents confirmed the adverse effect of amylose content on fermentation efficiency. High‐temperature cooking with agitation significantly increased the conversion efficiencies on mashes made from high‐amylose (35–70%) ground corn and starches. A cooking temperature of ≥160°C was needed on high‐amylose corn and starches to obtain a conversion efficiency equal to that of normal corn and starch. 相似文献
20.
L. A. Grant 《Cereal Chemistry》1998,75(5):590-594
The effects of two different methods of starch isolation, drying, and grinding on gelatinization and retrogradation properties were investigated. Starch was isolated from whole wheat and flour of four hard red spring wheat cultivars. Portions of each starch isolate were freeze-dried or air-dried and portions of each dried starch were ground using a mortar and pestle or a Wiley Jr. mill. Less starch damage was obtained for freeze-dried starch regardless of isolation method or grinding technique and for all starches derived from whole wheat. Highest starch damage was obtained for air-dried starch isolates. Wiley-milled starch isolates showed higher water-binding. Whole wheat starch isolates had higher peak, lower trough, and lower final viscosities, as determined by starch paste viscosity analysis, than did starch isolates derived from flour. Major effects of all treatments on differential scanning calorimetry gelatinization properties showed lower onset temperature for flour starch isolates, lower peak temperature for freeze-dried starches, and no effects due to grinding. Endotherms of all starches after refrigerated storage and freezethaw cycling were lower than those for gelatinization. 相似文献