Investigation of Cornmeal Components Using Dynamic Vapor Sorption and Differential Scanning Calorimetry

Degermed cornmeal, native starch, and corn gluten meal were individually extruded. DVS technology was used to produce isotherms and to condition extrudates to a constant moisture for Tg analysis. The DVS method results are compared to a PEC method. DSC was used to determine Tg. Isotherm and Tg data for starch and corn gluten meal were used to predict cornmeal snack sorption and Tg behavior. The Tg for extruded cornmeal, dent starch, and corn gluten meal at 18.5%db moisture content were 46.2, 49.4, and 12.7 °C, respectively. This suggests that the polymeric fractions of cornmeal (starch, protein) contribute to the Tg of cornmeal approximately based on the weight fraction of each polymer.     

玉米蛋白粉日粮纤维和能量对猪氮代谢的影响

平均体重 5 0 .9kg生长猪 ,采用全收粪法 ,6× 6拉丁方试验设计 ,测定不同种类的玉米蛋白粉日粮纤维和能量对生长猪氮代谢的影响。试验结果 :玉米蛋白粉 (CP :5 2 % )、玉米蛋白粉 (CP :47.4% )、玉米蛋白粉 (CP :32 % ) 3种日粮 ,氮的消化率分别为 87.9% ,88.9% ,89.7% ;总氮利用率分别为 5 2 .6 4% ,49.0 2 % ,37.86 % ;粪氮与日粮氮比值分别为 12 .0 % ,11.1% ,10 .5 %。玉米蛋白粉日粮的氮沉积量、氮消化率、总氮利用率与日粮的NDF ,ADF ,CF的消化率呈线性正相关。日粮的粪氮与日粮氮比值 ,同日粮的NDF ,ADF ,CF的消化率呈线性负相关 ,同日粮的NDF或CF含量呈线性正相关     

Effects of Enzymatic Hydrolysis of Protein on the Pasting Properties of Different Types of Wheat Flour

Abstract: As one of the most effective methods to modify proteins, enzymatic hydrolysis is used widely in the preparation of wheat products in the food industry. During the same process, starch pasting occurs frequently. The effects of wheat protein hydrolysis with papain, pepsin, and trypsin on the pasting properties of 3 different kinds of flour were investigated in 5 concentrations. Results showed that the peak viscosity, trough, final, and integral area of pasting curve of these flours decreased with increasing enzymatic hydrolysis of protein, and decreased significantly with the increasing enzyme concentrations. Medium‐gluten flour was the least sensitive to enzymatic activity and weak‐gluten the most sensitive. Downtrends appeared with increasing papain and trypsin concentrations in the form of breakdown. Enzymes had no significant different effect on the peak times of strong‐ and medium‐gluten flour, but prolonged peak time slightly in weak‐gluten flour. The pasting time and temperature of strong‐ and medium‐gluten flour were significantly increased in a concentration‐dependent manner. However, there were no significant effects on the pasting times of weak‐gluten flour. These results could supply a basis for utilization of enzymatic hydrolysis of wheat protein in food industry and for further studies into the interactions between hydrolyzed protein and starch in food or processing industries. Practical Application: Illuminating the effects of enzymatic hydrolysis of protein on the pasting properties of different types of wheat flour is very important in food industry. Flour viscosity decreases after enzymatic hydrolysis of protein/gluten. Enzymes have different effects on peak time, pasting time, and pasting temperatures for different types of flour. These results could supply a basis for utilization of enzymatic hydrolysis of wheat protein in food industry and for further studies into the interactions between hydrolyzed protein and starch in food or processing industries.     

Bread staling: Part III.—measurement of the re-distribution of moisture in bread by gravimetry

By converting a standard laboratory balance to one capable of measuring mutt changes in moment it was possible to record continually the progress of migration of moisture between the gluten and starch components in a model system simulating baked dough. The technique was demonstrated to be useful in assessing whether an anti-staling agent exerted its effect on the protein fraction by slowing down the release of moisture from the protein during ageing. Results are presented showing that during staling, crumb undergoes a small contraction in volume (ca. 1.7% in 4 days at 25°C) under conditions of constant moisture, consistent with a re-distribution of moisture from the continuous gluten phase to the starch.     

不同储藏条件对小麦流变学特性的影响

为了解小麦籽粒在不同储藏条件下的品质变化,探索实验室小量样品的最适储藏条件, 本研究以强筋、中筋和弱筋小麦的籽粒和面粉为研究材料,对其在不同梯度温度（?20、4、35 ℃）和不同储藏时间（20、40、60 d）条件下的品质指标进行分析。结果表明:不同储藏条件对不同类型小麦的湿面筋含量、吸水量和弱化度的影响较小,均在允差内。以籽粒方式储藏时,强筋小麦在不同温度条件下各品质参数基本上都在允差范围内,但随着储藏时间的延长（60 d）,形成时间和拉伸面积超差。中筋小麦在不同温度条件下,湿面筋含量和粉质参数基本上都在允差内,但是对拉伸参数（拉伸面积、拉伸阻力和最大拉伸阻力）影响较大;尤其是当储藏条件为?20和35 ℃的情况下,除延伸性外,拉伸面积、拉伸阻力和最大拉伸阻力均有不同程度的超差。弱筋小麦在不同温度条件下湿面筋含量和拉伸各参数均在允差内,但对粉质参数（稳定时间和弱化度）影响较大,尤其是稳定时间。值得注意的是,弱筋小麦随着储藏时间的延长,粉质各参数测定值越接近对照,在允差范围内。另外,不同类型的小麦在4 ℃条件下以面粉方式储藏时,强筋和中筋小麦的湿面筋含量、流变学粉质参数和拉伸参数均在允差值内。因此,本研究认为4 ℃,≤60 d比较适宜小麦籽粒和面粉的储藏。     

静电场辅助冷冻对面筋蛋白品质及分子结构的影响

本文研究了静电场辅助冷冻对面筋蛋白流变特性和热特性的影响,并通过分析其分子结构及离子键、氢键、疏水相互作用和二硫键的结果,探究静电场辅助冷冻对面筋蛋白品质的改善作用。结果表明,与对照（传统冷冻方式）相比,静电场辅助冷冻提高了面筋蛋白的黏弹特性、变性温度（Tp）和变性焓（?H）。化学作用力的分析表明,氢键的含量呈先降低后增加的趋势,而离子键、氢键和疏水相互作用的变化则与之相反。600 V电压静电场处理后,面筋蛋白的二级结构及二硫键的构型分布更加均匀,且?-螺旋的含量增加,二硫键构型中g-g-g构型的含量增加。扫描电镜分析表明,施加300 V和600 V的静电场后,面筋蛋白的网络结构具有更小的孔隙且分布均匀。     

Wheat bran dietary fibre-induced changes in gluten aggregation and conformation in a dough system

This study was conducted to determine the effect of wheat bran dietary fibre (WBDF) on aggregation and conformational changes of gluten in fermented and unfermented dough systems. The results revealed that WBDF has an advantage in maintaining the content of glutenin macropolymer (GMP) in the fermentation process. The analysis of the molecular weight distribution showed decreased content of larger polymeric proteins (LPPs). At the same WBDF level, after fermentation, the content of larger polymeric proteins (SPPs) increased, likely due to the polymerisation of the gliadins. Additionally, fluorescence spectroscopy and surface hydrophobicity analysis revealed that, in fermented dough, with the increase of WBDF content, the protein hydrophobicity significantly increased from 6.56 to 9.43 (P < 0.05). Hydrophobic interactions contributed to the macromolecular unfolding and/or aggregation of gluten. Also, WBDF may induce changes in dough properties by inducing conformational changes in the gluten protein.     

Impact of diatomaceous earth application on the rheological properties of wheat,triticale and rye flour dough

Although utilization of commercial products based on diatomaceous earth, an insecticide of the natural origin, plays a very important role in the integral protection of stored grains, the effect of their application on the rheological quality of small grains is poorly exploited. Therefore, the aim of this research was to employ GlutoPeak and Mixolab rheological devices in order to compare the impact of three diatomaceous earths (DEs) (Protect-It and two inert dusts originated from Serbia) application on the rheological properties of wheat, triticale and rye flour dough. While moisture and protein content did not differ in treated and untreated grain samples, application of all three DEs in two triticale varieties led to an increase in the wet gluten content and Mixolab water absorption, as well as a decrease in the gluten strength, as indicated by gluten index and GlutoPeak maximum torque values. Treated rye samples have also exhibited a decrease in dough maximum consistency and stability and greater protein structure weakening in comparison to untreated sample. The mentioned changes in rheological behaviour were not noticed in wheat varieties treated with DEs. The major changes were recorded in rheological behaviour of triticale and rye starch component which showed a decrease in maximum peak torque and hot paste stability after grain treatment with DEs. In general, the influence of DEs on rheological properties of small grains was highly species and varietal dependent, where more pronounced differences between treated and untreated grains were noticed in stronger varieties.     

The efficacy of enriching wheat meal, bread and gluten with L-lysine evaluated experimentally and theoretically

The effect of enrichment of wheat meal, bread and gluten with L-lysine was studied by the routine method (basing on the biological value estimated on growing rats), and theoretically (by the changes in the potential extent of the biological value). A higher value of the enrichment effect in the second case has confirmed the existence of the compensation induced by significant lysine deficiency. Enrichment of the studied products with lysine leads to elimination of the compensation that consists in lysine economy through decreasing its oxidizing catabolism. The dependence of the biological value on the level of gluten protein in the ration was also studied. Maximum figures of the biological value were recorded at 15% of gluten protein level and they were decreased at 7 and 30% levels.     

植物乳杆菌ST-III发酵苦荞面团中蛋白质降解规律的研究

苦荞蛋白作为苦荞中最主要的生物活性物质以及重要的营养成分之一,具有生物价高与氨基酸比例均衡等优点。但由于苦荞蛋白的组成中面筋蛋白含量较少且本身难以被吸收等方面的问题,其加工利用一直受到较大的限制。面团发酵技术作为一种能够提升面团加工品质以及最终产品营养价值的微生物发酵技术,能够提高谷物中蛋白质的利用率。本文选用植物乳杆菌ST-III(Lactobacillus plantarum ST-III)应用于苦荞面团发酵,通过比较苦荞发酵面团(Buckwheat Sourdough,简称BS)、小麦发酵面团(Wheat Sourdough,简称WS)和混合发酵面团(Wheat-Buckwheat Sourdough,简称WBS)发酵过程中变化发现：植物乳杆菌ST-III在BS发酵过程中菌落密度始终较大且显著高于WS和WBS中植物乳杆菌ST-III的菌落密度(p＜0.05),发酵24 h后可达到13.62 logCFU/g酸面团,同时,BS的pH为6.58,接近植物乳杆菌ST-III的最适pH,总酸含量最高达到24.39 mL,其中,乳酸以及乙酸含量分别是WS 与WBS的1.61-1.75倍以及1.06-1.15倍。此外,通过对三种面团发酵过程中总蛋白、清蛋白、醇溶蛋白、谷蛋白以及游离氨基酸含量的测定,并利用SDS-PAGE凝胶电泳发现,植物乳杆菌ST-III在发酵过程中对三种酸面团中总蛋白及其各组分的降解作用有显著差异(p＜0.05),其中,植物乳杆菌ST-III发酵对BS中苦荞蛋白的降解效果最为明显,且游离氨基酸含量随着发酵的进行呈上升趋势。综上可知,利用植物乳杆菌ST-III发酵苦荞酸面团不仅能够改善苦荞中面筋蛋白含量不足导致的加工品质较差的问题,而且提升了苦荞中蛋白质的利用率。     

SPI与SPH及其复配产物对面团特性和面条品质的影响机制

为提高面制品的营养品质,研究并比较了添加大豆分离蛋白(soy protein isolate,SPI)、大豆水解蛋白(soy protein hydrolyzates,SPH,水解度为4.54%)以及SPI和SPH复配产物(SPI-SPH)的混合粉的面筋特性和粉质特性,面团的动态流变学特性、蛋白质组分、二硫键和非共价键变化,以及面条的品质变化。添加SPI后面粉的湿面筋含量升高,干面筋含量下降,面筋指数降低,粉质特性评价值升高;面团的醇溶蛋白和麦谷蛋白含量增加,黏弹性增大,弹性比例增加。添加SPI-SPH的面粉面筋特性和面团特性变化趋势与添加SPI的面粉一致,其粉质特性评价值增大。添加SPH的面粉中无面筋洗出,粉质特性评价值升高;面团盐溶蛋白含量显著增加(P<0.05),弹性比例降低。添加大豆蛋白的面团中二硫键含量均增加,疏水相互作用减弱,氢键增强。与原面粉面条相比,SPI面条的硬度增大10.82%,SPI-SPH和SPH面条的弹性分别减小7.23%和6.02%,且添加SPH后面条的蛋白质保留率由93.02%降至87.31%。研究表明,大豆蛋白与面筋蛋白通过二硫键交联以及非共价键相互作用,阻碍面筋网络形成,破坏了面筋网络的连续性。并且,SPI和SPH复配在一定程度上减弱了SPH对面筋的弱化作用。     

Changes in urea-dispersibility of proteins during maturation

The quantity of proteins involved in gluten formation in wheat harvested at various stages of development of the grain was inversely related to absorbence at 280 mμ of 3 M -urea extracts. The amount of protein, as determined by the biuret procedure, in the 3·0 M -urea extracts did not change during maturation. Thus the decreasing absorbence (280 mμ) with increasing maturity between 27 to 17 days pre-ripe seems to indicate a gradual increase in molecular weight and complexity of the synthesised proteins. The changes in formation of gluten proteins were accompanied by a decrease in water- and salt-dispersible proteins, and paralleled improvement in bread-making properties of the flours.     

谷朊粉和小麦淀粉添加量对重组面团冻藏品质的影响

面团的冷冻保存品质无法满足鲜湿面条工业化生产的要求。为了研究面团主要组分（面筋蛋白和淀粉）对面团冷冻品质的影响,以高筋小麦面粉（50%）、谷朊粉和小麦淀粉（不同比例）为原料进行面团重组,-18℃冻藏20 d分析其水分分布、流变特性、糊化特性、凝胶强度、微观结构以及氢键强度,以100%原小麦面粉作为对照组。结果表明,随着谷朊粉:小麦淀粉比例从4:1减小至1:4,冷冻重组面团中的水分分布逐渐由结合水向自由水迁移,弹性模量从125900 Pa降低至73020 Pa;样品的各项糊化参数增大,凝胶硬度也由114.30 g增大到181.39 g。扫描电镜观察发现,谷朊粉:小麦淀粉比例越低越不利于面筋蛋白网络结构的均匀性。添加了谷朊粉和小麦淀粉后,重组面团中的氢键强度均大于对照组,且随着谷朊粉:小麦淀粉比例的减小不断增大。当谷朊粉:小麦淀粉为4:1时,冻藏20 d的重组面团的弹性模量值比对照组高49.95%,有效延缓了面团在冻藏过程中的品质劣变。将淀粉与面筋蛋白进行面团重组可以提高面团的黏弹性,进而有利于其冷冻保存品质。     

Effect of soybean proteins on gluten depolymerization during mixing and resting

BACKGROUND: Gluten and soy proteins interact as a consequence of dough mixing; however, there is no evidence of the effect of soy protein on gluten depolymerization. The aim of this study was to assess the depolymerizing effect of soy protein on gluten network after mixing and resting of mixed doughs. Therefore, the changes in glutenin macropolymer (GMP) content, protein composition and free sulfhydryl content were evaluated. RESULTS: The protein profile from gluten–soybean blends, obtained by multistacking SDS‐PAGE, showed differences when compared to gluten profile. Soy and gluten proteins were extracted together with SDS buffer, which showed that soy proteins remained associated to insoluble wheat proteins even after hand‐washing the dough to obtain gluten. GMP content was determined to analyze the effect of soy protein on GMP gel formation. Protein content of GMP obtained from flour mixes and doughs was increased by inactive soy flour because soy proteins became insoluble and precipitated together with GMP. Active soy flour decreased GMP content due to gluten depolymerization. CONCLUSION: Soy proteins were associated to wheat protein through physical interaction and covalent and non‐covalent bonds during mixing and resting. These interactions produced large and medium‐size polymers. This fact increased SDS solubility of insoluble gluten proteins, producing a weakening of the gluten network. Physicochemical status of soy protein in the product had a great influence on how wheat–soy proteins interact. Copyright © 2007 Society of Chemical Industry     

Microscopic investigation of the formation of a thermoset wheat gluten network in a model system relevant for bread making

Although the impact of heat on molecular properties of wheat gluten is well understood, changes in its microstructure have rarely been studied. Here, formation of the thermoset gluten network in a model system relevant for bread baking was studied with confocal laser scanning microscopy and protein network analysis. From 65 °C onwards, gluten converts from thick aligned protein strands in a highly branched and homogeneous network of small thin protein threads. Neither gliadin incorporation in the network nor application of aqualysin 1, the thermo-active serine peptidase from Thermus aquaticus which recently has been reported to hydrolyse gluten proteins in dough only at temperatures exceeding 80 °C, impacts on the gluten microstructure. As starch causes structure setting itself and thereby decreases protein mobility, molecular scale changes in the gluten network at temperatures exceeding 80 °C brought about by aqualysin 1 do not impact its microstructure.     

牡丹花蕊蛋白对面团和面筋蛋白特性的影响

为实现牡丹花蕊资源化利用,以大豆分离蛋白为参照,研究牡丹花蕊蛋白对面团和面筋蛋白质构、动态流变学特性、二硫键、表面微观结构和二级结构的影响。结果表明,牡丹花蕊蛋白能够明显提高面团的硬度、黏着性和咀嚼性,添加量低于6%时效果优于大豆分离蛋白。添加花蕊蛋白提高了面团的储能模量与损耗模量,使得面团黏弹性增加。牡丹花蕊蛋白对面筋蛋白网络结构形成的影响与大豆分离蛋白基本一致,添加量为6%时,扫描电镜显示面筋蛋白气孔数量多且孔洞深,网络结构致密;面筋蛋白二级结构中,相对稳定的α-螺旋+β-折叠占比达到最大值59.32%,与空白组相比二硫键含量提高了89%。牡丹花蕊蛋白能够有效促进面筋蛋白网络结构的形成,提高面团的品质,可用于对黏弹性要求较高的面制品生产。     

Effect of pH on the properties of soy protein–pectin complexes

The interactions of a commercial soy protein isolate (SPI) and a 2:1 SPI:high methoxy pectin (PEC) complex were evaluated over a range of pH values (3-7). The SPI formed very large (> 50 ??m) and largely insoluble aggregates (< 10%) close to its isoelectric point (IEP, pH 4 and 5) and smaller, more soluble (> 80%) particles at higher and lower pH values. The addition of PEC increased the solubility of SPI close to its IEP (pH 4 and 5) and prevented the formation of very large aggregates. However, PEC reduced the solubility of SPI at higher and lower pH values presumably via a depletion mechanism. The ??-potential of diluted SPI dispersions decreased from positive to negative with increasing pH, passing through zero at pH 4.6, the isoelectric point (IEP) of the protein. At pH < 6, the addition of PEC reduced the charge of the protein suggesting the formation of a complex while at pH 6 or 7 there was no evidence of complex formation. The increased SPI solubility in the IEP in the presence of PEC is probably due to the formation of charged complex which do not aggregate while the decreased solubility of protein in the presence at high and low PEC is probably due to the formation of insoluble complexes and a depletion interaction respectively. Thermal treatment (30 min, 90 °C) enhanced the solubility of the SPI:PEC complexes close to the IEP (pH 4 and 5), but reduces it at low pH (pH 3). The SPI:PEC complexes could be manufactured in the form of a beverage at pilot scale where their solubility was enhanced by homogenization.     

Dietary fat, protein degradability, and calving season: effects on nutrient use and performance of early lactation cows.

Twelve multiparous Holstein cows calving in fall and 12 calving in summer were blocked into four groups and used in a 2 x 2 x 2 factorial to determine the effects of season of calving, dietary fat, and protein degradability on milk production and efficiency of NEL utilization in a 16-wk study. Blocks were assigned randomly to one of four dietary treatment combinations: 1) control concentrate plus soybean meal (high degradability protein supplement); 2) control concentrate plus a mixture of heated soybean meal and corn gluten meal (low degradability protein supplement); 3) a blend of the control concentrate and a concentrate containing 12.1% fat to provide 1 kg d-1 fat, plus soybean meal; and 4) concentrate as in diet 3 plus heated soybean meal and corn gluten meal. Nutrient intake, milk yield and composition, BW changes, and daily ambient temperature were monitored. Intake of DM appeared to be related to NDF intake but was not affected by fat, protein degradability, or calving season. Intake of NEL was increased by feeding fat. Digestabilities of DM and CP were increased and fiber was decreased by feeding fat. Percentage and yields of milk fat, SNF, and protein and 4% FCM production were higher in cows calving in fall. Milk fat percentage was low in all cows in the study. Efficiency of energy utilization for milk production was decreased in cows fed fat and calving in the summer and by low protein degradability during wk 5 to 8 of lactation. At high concentrate intake, calving season had more effect on milk production than level of fat or protein degradability.     

Staling in Starch Bread: the Effect of Gluten Additions on Specific Loaf Volume and Firming Rate

Hypotheses on the role of gluten in bread staling range from gluten having an anti-firming effect, or no effect on firming, to gluten-starch interactions being essential for bread firming. To test these hypotheses, the firming rate of starch bread made from protein-free synthetic flour was compared with that of starch-gluten breads made from synthetic flours containing 1–15% gluten (Fig. 1). Only loaves of similar specific loaf volume and crumb moisture content were compared to eliminate these parameters as variables that might influence firming rate. The starch breads clearly increased in firmness up to six days, indicating that gluten was not essential to the firming process, starch alone causing bread to firm with time. The starch-10% gluten breads and starch-15% gluten breads had very similar specific loaf volumes, moisture contents and firming rates to that of the starch breads. This indicates that protein possibly has some role in firming, because if only starch has a role in firming then adding gluten would effectively dilute the starch and reduce the rate of firming. We propose that increasing bread firmness results from glucan chains of partially leached amylose and amylo-pectin attached to swollen starch granules forming hydrogen bonds with other starch granules and, to a smaller extent, with gluten fibrils.     

添加赖氨酸和苏氨酸对小麦面筋蛋白降低大鼠同型半胱氨酸效果的影响

目的在小麦面筋蛋白中添加赖氨酸和苏氨酸,探讨两种限制氨基酸在小麦面筋蛋白中降低大鼠血浆高同型半胱氨酸(Hcy)血症的影响。方法 32只健康Wistar大鼠随机分为4组,分别为大豆分离蛋白组(25S)、酪蛋白组(25C)、小麦面筋蛋白组(29G)、赖氨酸+苏氨酸添加组(29GLT)。各组大鼠分别给予不同饲料喂养14 d后处死,采集血液、肝脏等样品,用于测定生化、酶学指标。结果添加赖氨酸和苏氨酸可有效改善大鼠因摄入小麦面筋蛋白导致的体重、血浆中Hcy的降低,可抑制血浆S-腺苷蛋氨酸(SAM)和肝脏甜菜碱高半胱氨酸甲基转移酶(BHMT)活性的升高,但对胱硫醚β-合成酶(CBS)活性无影响。蛋氨酸含量较低的大豆分离蛋白组,血浆中同型半胱氨酸的含量并未降低。结论小麦面筋蛋白对大鼠血浆同型半胱氨酸浓度的影响可能与其氨基酸的组成特点有关。小麦面筋蛋白的高半胱氨酸和低赖氨酸及低苏氨酸的氨基酸组成是小麦面筋蛋白降低同型半胱氨酸水平的可能因素。