氮素营养对小麦产量和籽粒蛋白质及组分含量的影响

研究了不同施氮量和施氮时期对小麦籽粒蛋白质及组分含量和产量的影响。试验结果表明 ,随施氮时期后移 ,小麦籽粒蛋白质及不同组分含量呈递增趋势 ,其中谷蛋白和清蛋白含量随施氮期推迟而递增 ,以孕穗期施氮达最高 ,醇溶蛋白和球蛋白含量以拔节期施氮为最高 ;随施氮量增加 ,小麦籽粒蛋白质含量明显提高 ,二者呈显著正相关。施氮量与籽粒产量和蛋白质产量间呈二次曲线关系 ,籽粒最高蛋白质产量施氮量高于其最高产量施氮量     

氮素运筹技术对冬小麦籽粒产量和品质影响的研究

研究结果表明施氮量与籽粒产量、蛋白质含量均呈二次抛物线关系。籽粒产量的临界施氮量小于籽粒蛋白质含量的临界施氮量,0~23.31g/m2为产量和蛋白质含量的同步增长区,23.31~27.14g/m2为异步徘徊区,27.14g/m2以上为同步下降区。增施氮肥能提高籽粒麦谷蛋白、醇溶蛋白的含量及籽粒麦谷蛋白与醇溶蛋白的比值,同时显著提高籽粒湿面筋含量、面团稳定时间和面团延伸度。氮肥基施与追施相结合有利于提高籽粒产量和品质,以基施、拔节期和孕穗期三次施肥效果最佳,适当加大中后期氮肥施用比例,对提高小麦籽粒营养和加工品质有着重要的作用。     

氮用量对香料烟生理特性及品质的影响

采用盆栽与大田试验 ,研究了不同氮 (N)用量对香料烟生育期内生理特性及品质的影响。结果表明 :随氮用量的增加 ,各时期鲜叶中叶绿素、游离氨基酸含量、硝酸还原酶活性呈增加趋势 ,调制后烟叶总氮、烟碱、蛋白质、钾含量随氮用量的增加而增加 ,还原糖的含量则以施氮量 30kg hm2 的处理较高 ,氮用量对氯离子含量影响不明显 ;调制后烟叶中测定出的 33种香气物质总量以施氮量 15～ 30kg hm2 的处理较高 ,不施氮的处理最低。     

氮肥运筹模式对不同穗型冬小麦籽粒产量和品质调控效应的研究

以重穗型品种矮早8和中间型品种周麦18两个中筋小麦品种为试验材料,研究了在180～300 kg/hm2范围内3个梯度氮肥用量和三种基追比例对小麦产量和品质形成的调控效应.试验结果表明:氮肥运筹模式对不同穗型小麦品种籽粒产量有明显的调控作用.重穗型品种矮早8以中氮水平下基肥:拔节肥:孕穗肥为3:5:2的M1处理单产最高,为8 319.0 kg/hm2;中间型品种周麦18以中氮水平下基肥与拔节肥并重的M2处理籽粒单量最高,为9027.0 kg/hm2.氮肥对中间型品种周麦18产量的调控主要是通过对单位面积稳数的调控来实现的,对重穗型品种矮早8则主要是通过对穗粒数和千粒重的调控来实现的.重穗型品种矮旱8籽粒蛋白质含量随氮肥用量和追肥比例的增加而升高,高氮水平下基肥:拔节肥:孕穗肥为3:5:2的处理H1籽粒蛋白质含量最高;中间型品种周麦18籽粒蛋白质含量则以中氮水平下基肥与拔节肥并重的M2最高;供试品种的淀粉直/支比均随氮肥用量的增加和追肥比例的增加而提高.在180～300 kg/hm2纯氮范围内,根据品种不同穗型特点,采用中氮水平,适当加大追肥比例,重穗型品种矮早8以中氮水平下基肥:拔节肥:孕穗肥适为3:5:2适宜,中间型品种周麦18以中氮水平基肥:拔节肥为5:5是实现高产优质同步提高比较合理的氮肥运筹模式.     

氮素水平对红花大金元烟叶游离氨基酸和蛋白质含量的影响

为了解氮素水平对云南烟区红花大金元烟叶游离氨基酸和蛋白质含量的影响,通过田间试验设置4个施氮水平0、45、90和135 kg/hm~2,分析其对红花大金元烟叶游离氨基酸和蛋白质含量的影响,并通过感官质量对烟叶品质进行评价。结果表明,烟叶内组氨酸和天冬酰胺等含量随施氮水平的提高而显著增加,谷氨酰胺和精氨酸等含量以施氮90 kg/hm~2处理最高,施氮135 kg/hm~2时出现下降趋势,赖氨酸含量则是随施氮水平的增加而显著降低;游离氨基酸总量和蛋白质含量随施氮水平的提高显著增加,施氮135 kg/hm~2最高可达9.617 mg/g和10.56%;感官评吸中烟叶的香气质和评吸总分以施氮90kg/hm~2处理得分最高,不施氮处理最低。在本试验条件下,烟叶内游离氨基酸的含量变化随施氮水平的改变呈现出不一样的特点,但游离氨基酸总量和蛋白质含量随施氮水平的提高显著增加,施氮90 kg/hm~2处理烟叶感官质量最佳。     

施氮量对烤烟常规化学成分含量及主流烟气中7种有害成分释放量的影响

以烤烟豫烟12号为材料,通过田间试验研究不同施氮量对烤烟化学成分和主流烟气中7种有害成分的影响。结果表明,施氮量不同不仅影响烟叶常规化学成分的含量,而且对主流烟气中有害成分的释放量产生了影响;随施氮量增加,烟叶中蛋白质、烟碱和总氮的含量增加,总糖和还原糖含量减少,钾和氯含量影响不明显;主流烟气中7种有害成分随施氮量的增加变化趋势不同,随施氮量增加,巴豆醛的释放量减少,氨和NNK的释放量增加;施氮量在55 kg/hm2时,烟叶常规化学成分协调,主流烟气中7种有害成分的危害性指数最低,烟草质量安全性较高。      

施氮量对烤烟糖代谢关键酶活性及其基因表达的影响

为明确供氮水平对烤烟糖代谢关键酶活性、基因表达量以及糖含量的影响,开展了供氮水平及品种的两因素试验,结果显示,蔗糖合成酶活性随施氮量增加而增强,且处理间差异显著;蔗糖磷酸合成酶、转化酶及淀粉酶的活性,在栽后45 d与60 d随施氮量增加而增强;在栽后80 d,高施氮量转化酶及淀粉酶的活性低于低施氮量。同一施氮量,品种间的酶活性没有显著的差异。施氮量对糖代谢关键酶基因的表达量有显著影响,同一施氮量不同品种之间基因表达量存在一定的差异。烟叶总糖和还原糖含量受施氮量的影响较小;但淀粉的含量却随着施氮量的增加而增加。同一施氮量处理不同品种之间,糖含量差异不明显。相关分析结果显示,测定的4个糖代谢关键酶的活性,与各生育时期淀粉含量呈著或极显著相关;栽后45 d,蔗糖磷酸合成酶基因表达量与烟叶淀粉含量显著负相关,栽后60 d及80 d蔗糖合成酶基因的表达量,分别与还原糖及总糖呈显著正相关。本研究的结果表明,施氮水平对烤烟糖代谢关键酶活性及其基因表达有着显著的影响,烟叶中的糖含量受蔗糖合成酶及蔗糖磷酸合成酶活性及基因表达量的制约。     

水分胁迫下施氮量对烤烟生理特性及化学成分的影响

采用盆栽试验研究了水分胁迫下施氮量对烤烟生理特性及化学成分的影响.结果表明,在中度干旱下(相对含水率50%)随施氮量增加,烤烟根系活力增强,叶片脯氨酸含量、超氧化物歧化酶(SOD)活性及光合速率明显升高,丙二醛含量无明显差异;轻度干旱条件下(相对含水率65%),烤烟团棵期和成熟期缺氮或氮素水平过高,烤烟根系活力、SOD酶活性及光合速率均明显降低,丙二醛含量增加,脯氨酸含量变化不大,在烤烟旺长期和现蕾期烤烟根系活力、SOD酶活性,丙二醛及脯氨酸含量均随施氮量增加明显升高.在中度和轻度干旱下随施氮量增加,上部叶和中部叶总氮、烟碱及蛋白质含量呈增加趋势,总糖、还原糖含量呈下降趋势,糖碱比、氮碱比、施木克值以纯N 7 g/株的中氮肥处理较合理.在同一施氮水平下,中部叶和上部叶总糖和还原糖含量随着土壤含水率的增加而增加,烟碱、总氮以及钾含量均有所降低,糖碱比、氮碱比、施木克值以轻度干旱较适宜.     

不同类型专用小麦HMW-GS和GMP含量与面筋含量的关系

高分子质量谷蛋白质亚基(HMW-GS)是决定小麦加工品质的重要因子,以25个小麦品种为材料,采用SDS-PAGE电泳方法研究亚基组成、各位点(Glu-A1、Glu-B1、Glu-D1)亚基积累量、谷蛋白大聚合体(GMP)含量及其与面筋含量的关系.研究结果表明:低蛋白小麦品种HMW-GS组成主要以"N、7+8/7+9、2+12"亚基组合为主,高蛋白小麦品种HMW-GS组成则主要以"1、7+8/7+9、5+10"亚基组合为主,中等蛋白小麦品种兼有以上两种类型亚基组合;亚基组成相同的小麦,籽粒GMP含量和蛋白质含量仍有较大差异.相关分析表明,HMW-GS亚基总积累量与籽粒蛋白质含量和GMP含量呈极显著正相关,与干、湿面筋含量成正相关;GMP含量与干、湿面筋含量、蛋白质含量均呈极显著正相关,说明小麦品质类型虽与HMW-GS组成有关,但亚基积累强度不同可能是导致籽粒品质类型差异的重要因素之一.     

施氮量对烤烟产量和品质的影响

通过在福建三明和南平的田间试验研究了施氮量对烤烟产量和品质的影响.结果表明,不同施氮量对烟株农艺性状、烟叶产量、产值、化学成分、外观品质和评吸质量均有显著影响.株高、茎围、最大叶面积、单叶重和产量随施氮量的增加而上升,产值、均价和上等烟比例在适宜的施氮量下表现较好.不同部位烟叶烟碱含量随施氮量增加显著提高,还原糖含量和还原糖/烟碱比值降低.综合烟叶内在化学分析、外观品质和评吸结果,三明试验点以施N76.5kg/hm2和102kg/hm2处理较好,而南平试验点则以施N102kg/hm2和127.5kg/hm2较好.     

Co-precipitation of whey and pea protein – indication of interactions

The aim was to optimise the yield of co-precipitation of whey protein isolate (WPI) and pea protein isolate (PPI) and compare co-precipitates and protein blends with respect to solubility. The yield of co-precipitates was tested with different protein ratios of WPI and PPI in combination with different temperatures and acid precipitation (pH 4.6). The highest precipitation yield was obtained at protein ratios WPI < PPI, high temperature and alkaline protein solvation. The solubility was measured by an instability index and absorption spectroscopy of re-suspended precipitated proteins at pH 3, 7 and 11.5. Co-precipitates had significantly lower solubility than protein blends. Protein ratios WPI > PPI, low precipitation temperature and high pH showed the highest solubility. Differences in protein composition between co-precipitates and protein blends were observed with SDS-PAGE and matrix-assisted laser desorption ionisation time-of-flight, and indicated different protein–protein interaction in samples, which needs further investigations.     

大豆蛋白溶解性研究

该文概述大豆蛋白溶解特性及其与一般物质溶解差异,介绍提高大豆蛋白溶解性改性方法及研究现状,对比不同改性增溶方法优、缺点,并提出今后大豆蛋白改性研究方向。     

细菌中蛋白质样品制备方法研究进展

细菌在生长繁殖时,细菌蛋白的表达受到环境影响而存在较大差异,使得细菌蛋白表达具有复杂性.在食品生产加工过程中可能会受到致病菌污染,细菌产生的内毒素和外毒素均会对人体健康构成威胁,因此需要高灵敏度和高特异性的检测方法来定量分析和鉴定食品中的细菌毒素.蛋白组学方法可以揭示细菌蛋白组成及其潜在的生物学功能,感染过程中菌体蛋白...     

Physicochemical and Functional Properties of Soy Protein Substrates Modified by Low Levels of Protease Hydrolysis

ABSTRACT: Endo-protease treatments achieving low degrees of hydrolysis (DH 2% and 4%) were used to improve functional properties of hexane-extracted soy flour (HESF), extruded-expelled partially defatted soy flour (EESF), ethanol-washed soy protein concentrate (SPC), and soy protein isolate (SPI). These substrates had protein dispersibility indices ranging from 11% to 89%. Functional properties, including solubility profile (pH 3 to 7), emul-sification capacity and stability, foaming capacity and stability, and apparent viscosity were determined and related to surface hydrophobicity and peptide profiles of the hydrolysates. Protein solubilities of all substrates increased as DH increased. Emulsification capacity and hydrophobicity values of the enzyme-modified HESF and EESF decreased after hydrolysis, whereas these values increased for SPC and SPI. Emulsion stability was improved for all 4% DH hydrolysates. Hydrolyzed SPC had lower foaming capacity and stability. For substrates other than SPC, foaming properties were different depending on DH. Hydrolysis significantly decreased the apparent viscosities regardless of substrate. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated differences in the molecular weight profiles of the hydrolysates. HESF and EESF, which had high proportions of native-state proteins, showed minor changes in the peptide profile due to hydrolysis compared with SPC and SPI.     

Effects of silage protein degradability and fermentation acids on metabolizable protein concentration: A meta-analysis of dairy cow production experiments

A meta-analysis was conducted using data from dairy cow production studies to evaluate silage metabolizable protein (MP) concentrations. The data consisted of 397 treatment means in 130 comparisons, in which the effects of silage factors (e.g., date of harvest, wilting, silage additives) were investigated. Within a comparison, a fixed amount of the same concentrate was fed. A prerequisite of data to be included in the analysis was that silage dry matter (DM), crude protein (CP), ammonia N, lactic acid (LA), and total acid (TA) concentrations and digestibility were determined. A smaller data set (n = 248) comprised studies in which silage water-soluble N concentration was also analyzed. The supply of MP was estimated as amino acids absorbed from the small intestine using a model with constant values for ruminal effective protein degradability (EPD) and intestinal digestibility of rumen undegraded protein. Microbial protein was calculated on the basis of digestible carbohydrates and rumen degradable protein (RDP). Alternative models were used to estimate microbial protein formation, assuming the energy values of RDP and TA to be equivalent to 1.00, 0.75, 0.50, 0.25, and 0 times that of digestible carbohydrates. Because EPD values are seldom determined in production trials, they were derived using empirical models that estimate them from other feed components. The goodness of fit of models was compared on the basis of root mean squared error (RMSE) of milk protein yield (MPY) predicted from MP supply (adjusted for random study effect) and Akaike's information criterion. Metabolizable protein supply calculated from basal assumptions predicted MPY precisely within a study (RMSE = 16.2 g/d). Variable contribution of RDP to the energy supply for microbial synthesis influenced the precision of MPY prediction very little, but RMSE for MPY increased markedly when the energy supply of rumen microbes was corrected for TA concentration. Using predicted rather than constant EPD values also increased RMSE of MPY prediction. These observations do not mean that the supply of MP from undegraded feed protein is constant. However, it suggests that our current methods overestimate the range in EPD values and that the techniques have so many inherent technical problems that they can mask the true differences between the feeds. Including new elements in feed protein evaluation models may not improve the precision of production response predictions unless the consequent effects on the supply of other nutrients are taken into account.     

大豆蛋白生产与应用现状

该文综述大豆蛋白制品—大豆蛋白粉、大豆分离蛋白、大豆浓缩蛋白、大豆组织蛋白生产现状、存在问题及大豆蛋白在面制品、肉制品、乳制品、饮料制品等中应用现状。     

The structures and functions of ice crystal-controlling proteins from bacteria

Many organisms have evolved into unique mechanisms which minimize freezing injury due to extracellular ice formation. Specifically, certain bacteria have produced a few proteins each with different functions. For example, the ice nucleation protein acts as a template for ice formation, which is responsible for imparting ice nucleating activity. The anti-nucleating protein inhibits the fluctuation of ice nucleus formation by a foreign particle in the water drop. Also, the antifreeze proteins depress the freezing temperature, modify or suppress ice crystal growth, inhibit ice recrystallization, and protect the cell membrane from cold-induced damage. In this article, a review on the current knowledge of the structure and the function of these three types of proteins, which are capable of interacting with ice itself or its nuclei from bacteria.     

Effect of amidation on the foaming and physico-chemical properties of bovine serum albumin

Amidation of bovine serum albumin (BSA) was achieved by a water-soluble carbo-diimide, ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)-mediated reaction using ammonium chloride as the nucleophile. Partial and substantial amidation of 0.5% (w/v) BSA in 5.5 m ammonium chloride solution with 1 times 10-²mmol EDC over 120 min and 1 times 10^-1mmol EDC over 10 min respectively was achieved on a large scale using diafiltration for rapid termination of the reaction and purification. Residual ammonium chloride otherwise enhanced foaming properties. The amidated proteins were characterized by isoelectric focusing, electrophoresis and hydrophobicity and disulphide- and sulphydryl-group measurements. Compared with native BSA, partially amidated BSA (PA-BSA) produced enhanced foam expansion and foam stability values. This was attributed to minimal denaturation and to the presence of both acidic and basic components (pI range 5.25–7.50) within the single protein. In contrast, substantially amidated BSA (SA-BSA) (pI range 7–9.1) had similar foaming properties to those of the ultrafiltered BSA control which were slightly lower than those of native BSA. However SA-BSA interacted synergistically with native BSA producing enhanced foaming properties particularly at the 1:1 ratio through electrostatic interactions, conformational changes and increased hydrophobicity.     

大豆分离蛋白改性对其功能性质影响

大豆分离蛋白是大豆蛋白最为精制形式,广泛应用于食品工业,并在不同产品中表现出不同功能。该文综述近年来大豆分离蛋白物理、化学、酶法及基因工程改性对其功能性质影响,经不同方式改性可产生合适功能性质,从而拓宽大豆分离蛋白在食品工业中应用。     

芝麻蛋白研究概况

简述芝麻蛋白的结构及氨基酸组成、蛋白质性质和应用,并展望进一步研究芝麻蛋白的 前景。