Molecular Structure and Functionalities of Protein Isolates Prepared from Defatted Cottonseed Flour Succinylated at Various Levels

Protein isolates were prepared from glandless cottonseed flour succinylated at various levels. Succinylation levels of the resultant proteins followed first order kinetics with respect to succinic anhydride concentration added. Succinylation decreased the amount of free sulfhydryl, as well as ξ-amino groups of proteins, but did not change intermolecular disulfide bonds. Protein isolate prepared from highly succinylated flour consisted of one homogeneous protein agglomerate, while isolate from unmodified flour contained several heterogeneous proteins. Water solubility of the isolates increased logarithmically with respect to degree of succinylation, with the sharpest increase at 95% succinylation or higher. Heat coagulability had an inverse-linear relationship with amounts of negative charges on protein molecules. Emulsion capacity and oil absorption capacity were not significantly changed at less than 60% succinylation. However, these increased markedly at greater than 60% succinylation. Emulsion capacity had a positive, but not linear correlation with water solubility of proteins.     

Succinylation of Cottonseed Flour: Effect on the Functional Properties of Protein Isolates Prepared from Modified Flour

Succinylated cottonseed protein isolates (40% and 54% modification of amino groups of control isolate) were prepared under pilot scale processing conditions. Partial succinylation of cottonseed flour increased the yield of protein isolate in isoelectric precipitation (pH 4.5). The succinylated isolates were more water soluble, less heat-coagulable in water, and lighter in color as compared to conventional isolates. They also showed improved functional properties including higher oil absorption, emulsion capacity, gel strength, water hydration, water retention, and viscosity. Bulk density was decreased and resulted in fluffy isolates.     

Effect of Acylation Upon Extractability of Nitrogen, Phytic Acid and Minerals in Rapeseed Flour Protein Concentrates

Rapeseed flour (RF) and protein concentrates (RPC) were acylated with various levels of succinic or acetic anhydride. Compared with the unmodified control, 63% succinylation or 87% acetylation resulted in up to 45% increase in nitrogen and 95% decrease in phytic acid extractabilities in the first RF extract. At 21% succinylation or 55% acetylation, the extractability of phytic acid was more than double that of the unmodified control whereas the extractability of nitrogen was increased by 22%. A second extraction of the residual acylated RF with deionized water increased the extractability of phytic acid. For both first and second extracts, the extractability pattern of the major minerals followed that of phytic acid. Acylation of heat treated protein concentrate was not effective in increasing the nitrogen and decreasing the phytic acid extractabilities.     

Fate of Pigments and Phytate During Isolation of Protein from Defatted Glandless Cottonseed Flour

In sequentially extracting proteins from defatted glandless cottonseed flour with water, salt (5% NaCl) and alkali (0.2% NaOH) solutions, high concentrations of yellow pigments resulted in watersoluble isolate (WSI), while much of the dark-brown pigments and phosphorus were found in alkali-soluble isolate (ASI) and small amounts of pigments in salt-soluble isolate (SSI). The major protein fractions of WSI and SSI contained small amounts of sugar and pigments and no phosphorus, while that of ASI contained high levels of bound sugar, dark-brown pigments and phosphorus. Yellow pigments were preferentially bound to small molecular weight proteins, but dark-brown pigments were bound to large protein molecules.     

高温处理对脱脂豆粕中大豆分离蛋白结构的影响

以不同温度处理的脱脂豆粕为原料,制备大豆分离蛋白,通过紫外光谱、荧光光谱、电泳及浊度测定等方法探讨了高温处理对脱脂豆粕中大豆分离蛋白结构的影响,结果表明:热处理可促使蛋白多肽链局部展开,色氨酸等残基暴露并部分氧化,产生一些新荧光物质;凝胶电泳分析显示,热处理样品的高分子区域条带渐趋显著,各亚基条带呈现扩散趋势,蛋白质相对分子质量分布范围变宽;浊度分析表明,随着样品热处理温度升高,大豆分离蛋白的混浊度增加。     

脱脂麦胚蛋白功能特性的研究

以脱脂麦胚蛋白为材料,研究了其溶解性、乳化剂、起泡性和持水性等功能特性。结果表明：脱脂麦胚蛋白的等电点为４．０,ＰＨ〉６．０时蛋白质溶解指数ＮＳＩ值可达７０％,具有较高的溶解度;脱脂麦胚蛋白的乳化活性ＥＡ和乳化稳定性ＥＳＧ民牛血清白蛋白近似,并略高于酪蛋白;脱脂麦胚蛋白具有很好的起泡性ＦＣ,其泡沫稳定性ＦＳ稍差,但可通过物理、化学或酶和为克服;脱脂麦胚蛋白具有非常理想的持水性ＷＲ,在ＰＨ＝８．０和     

Effects of Defatted Jack Bean Flour and Jack Bean Protein Concentrate on Physicochemical and Sensory Properties of Bread

This study evaluated the effects of substituting wheat flour with defatted Jack bean flour and Jack bean protein concentrate on bread quality. Jack bean flour milled from the seed nibs was defatted with n-hexane and part of the defatted flour (DJF) extracted in acid medium (pH; 4.5) for protein concentrate (JPC). Both the DJF and JPC were analysed for nutrient composition, and then used to fortify bread. Five bread samples with 0%, 10% and 20% of DJF or JPC were prepared using straight dough procedure, and then analysed for quality characteristics. The DJF and JPC had 28.8% and 49.47% protein, 46.44% and 30.22% carbohydrate, 0.61% and 1.00% crude fibre respectively; and were rich in Ca, Fe, Zn and P. Both DJF and JPC improved quality of bread but JPC conferred better quality. The 20% DJF and JPC respectively improved protein content of bread from 9.45% to 10. 97% and 11.16%, crude fibre from 2.39% to 5.20% and 5.32%, fat from 2.35% to 7.00% and 6.55%, and ash content from 1.35% to 2.05% and 2.10% but decreased carbohydrate content from 72.12% to 50.45% and 50.39% in the bread samples. All the fortified bread samples had acceptable crumb colour, crumb texture, flavour and loaf volume significantly comparable (p > 0.05) to those of 100% wheat bread. Thus, defatted Jack bean flour and Jack bean protein concentrate is recommended for use in fortifying bread for higher quality.     

Functional Properties of Defatted and Detoxified Madhuca (Madhuca butyraceae) Seed Flour

Functional properties of defatted and detoxified Madhuca (Madhuca butyraceae) seed flours were determined and compared with those of soybean flour. Soybean and detoxified Madhuca flours had higher water absorption capacities than defatted Madhuca flour. Due to the presence of saponins, the defatted Madhuca flour showed higher foaming capacity than the soybean and detoxified Madhuca flours.     

Microwave and Ultrasound to Enhance Protein Extraction from Peanut Flour under Alkaline Conditions: Effects in Yield and Functional Properties of Protein Isolates

The effect of microwaves (MWs) and/or ultrasound (US) to assist alkaline extraction of peanut proteins was evaluated. Isolate extraction yields and purities were obtained as well as functional properties (water solubility and retention, fat absorption, nitrogen solubility, emulsifying activity, and foam activity and stability), in vitro digestibility, free amino nitrogen (FAN), microstructure and secondary structure. In MW-assisted treatments, power (145, 290, 435, 580, and 725 W) and time (2, 4, 6, 8, and 10 min) were evaluated, whereas in US-assisted assays, amplitude (20/100%) and time (15/40 min) were varied. For MW-assisted extraction, 725 W and 8 min yielded an extraction of 55% (100% purity), i.e., 77% more protein when compared with the control, while for US, an increase of 136% and purity of 86% was reached (100% amplitude and 15 min). The sequential use of both technologies was also evaluated, but a synergistic effect in protein extraction was not observed. In terms of functional properties, fat absorption index remained the same for both treatments whereas water absorption, foam activity, emulsifying activity (for MW), and in vitro digestibility (for MW only) improved. In the case of free amino nitrogen, a reduction of 50% for assisted peanut protein isolates was observed. Microstructure was not different among treatments, but secondary structure did change: β-sheet and nonordered structures were higher for experimental treatments compared with the traditional alkaline isolate (up to 8 and 4%, respectively). The use of MW and US favored peanut protein extraction for production of high purity isolates.     

Functional Properties of Chinese Rapeseed Protein Isolates

A membrane-based protein isolation process developed in our laboratory produced two protein isolates from CH₃OH/NH₃/H₂O-hexane-extracted Chinese rapeseed meal. Both contained ～99% protein (NX6.25), and they were essentially free of glucosinolates or their breakdown products (<2,2 μmol/g). Their functional properties were evaluated and compared with a commercial soybean protein isolate. The precipitated isolate gave high values for all properties except nitrogen solubility index (NSI) while the soluble isolate showed excellent NSI and fat absorption but poor emulsification characteristics. They both had good foaming properties. The two Chinese rapeseed protein isolates complemented each other and were comparable to soybean protein isolate in most functions.     

Functional Properties of Acylated Pea Protein Isolates

Pea protein isolates were acylated with succinic and acetic anhydride at 1.0, 3.0, and 5.0 mmol anhydride/g protein. The chemically modified isolates showed increased emulsifying capacity, emulsion stability, foam capacity and stability, and water adsorption compared to untreated pea protein isolate. In general, the greater the extent of acylation, the greater the improvement in emulsification properties compared to the untreated protein isolate; however, improvement at greater than 3.0 mmol anhydride/g protein was slight. Acetylation at 3 mmol/g increased foam capacity to the greatest extent. Water adsorption was enhanced to the greatest extent in protein isolates acetylated at 5 mmol/g. Acylation lowered the isoelectric point of protein isolates compared to untreated isolate. In vitro enzyme hydrolysis of the protein isolates, as determined by a multienzyme system of trypsin, chymotrypsin and peptidase, was not impaired by acylation.     

Functional Properties of Deamidated Oat Protein Isolates

Oat protein isolates were deamidated by mild acid hydrolysis. Amino acid analysis and gel filtraiton chromatography showed no significant cleavage of peptide linkages although the aggregated and oligomeric oat proteins were extensively dissociated. Deamidation led to marked improvement in solubility, emulsifying properties and water and fat binding capacities. The pH for heat-induced gelation was lowered by deamidation, and a firm, elastic gel was produced by mixing egg white with deamidated oat isolates.     

脱脂花生蛋白粉对玉米膨化功能特性的影响

以玉米为原料,脱脂花生蛋白粉为主要辅料,对其进行挤压膨化,对产品的功能特性及各分析指标的相互关系进行了研究。结果表明:产品的膨化度和吸水指数(WAI)均随着脱脂花生蛋白粉添加量的增加而下降,色泽逐渐加深,而水溶性指数(WSI)随着脱脂花生蛋白粉添加量的增加而增加,当脱脂花生蛋白粉添加量为25%时,产品的糊化度最高(98.92%),并具有较好的WAI和WSI;得到了各分析指标的关系模型。     

棉仁蛋白粉毒性实验观察

依据GB15193.1～15193.21—2003《食品安全性毒理学评价程序和方法》对棉仁蛋白进行安全性毒理学研究。结果表明,雌、雄大鼠的急性经口毒性试验(MTD)均大于10g/kgBW,属实际无毒物,相当于约人体推荐量的200倍;小鼠骨髓嗜多染红细胞微核试验、小鼠精子畸形试验(受试物剂量分别为2.5、5.0、10.0g/kgBW),Ames试验(受试物分别为0.032、0.16、0.8、4.0、20.0mg/皿)结果均为阴性,无致突变作用;90d喂养试验各剂量组雄性大鼠每日实际摄入样品量分别相当于2.33、4.74、8.73g/kgBW,雌性大鼠每日实际摄入样品量分别相当于2.79、5.65、10.09g/kgBW。各剂量组大鼠生长情况良好,各剂量组大鼠各周体重均高于对照组,差异大都无统计学意义;主要脏器绝对重量、脏体比、血常规检查、生化检查均在正常值范围内;高剂量组肝、脾、肾、胃、十二指肠、睾丸、卵巢与对照组比较均未见与受试物作用有关的组织病理学改变;传统致畸试验对胎鼠未见致畸作用。     

Characteristics and Functional Properties of Protein Isolates from Various Peanut (Arachis hypogaea L.) Cultivars

Protein isolates from 9 cultivars of peanut (Arachis hypogaea L.) were compared. Sephadex G-200 gel filtration and nondenaturing polyacrylamide gel electrophoresis (NPAGE) of the protein isolates showed very similar patterns of arachin and nonarachin fractions. The content of individual fractions was somewhat different among cultivars, possibly indicating genetic variability. Sodium dodecyl sulfate-PAGE (SDS-PAGE) showed that the protein isolates had extremely complex sub-unit compositions. The content of acidic amino acids of the protein isolates was 34–38%, basic was 15–17%. Differences in some functionalities such as solubility and emulsification activity were conspicuous among cultivars.     

脱脂大豆粉对小麦粉及馒头品质影响研究

将脱脂大豆粉添加到小麦粉中,研究其对小麦粉理化特性和馒头制作品质的影响。研究结果表明,在小麦粉中添加低于2%的脱脂大豆粉时,可以明显地改善小麦粉的品质,具体体现在可以增加面粉的白度,增加面团的吸水量、稳定时间以及拉伸曲线面积和拉伸比数,还可以改善馒头的品质;当在小麦粉中添加高于2%的脱脂大豆粉时,其对面粉的品质具有不好的影响,具体体现在降低小麦粉的白度以及面团的筋力,对馒头的品质也具有不良的影响,表现为馒头体积变小,颜色发暗。     

脱脂豆粉对面团性质的影响及在面包焙烤中的应用

面包中添加脱脂豆粉使其具有良好的营养价值,在面粉中添加10%的脱脂豆粉后,对面团流变学特性和面包焙烤品质产生直接影响,吸水率和面团的耐搅拌性提高,产品的弹性增加。通过测定产品压缩值、比容值,发现添加10%脱脂豆粉的甜面包不但营养丰富,而且在产品品质、质地、结构、体积、口感等方面基本达到了要求。     

脱脂活性豆粉对面粉品质的影响

通过在面粉中添加一定比例的脱脂活性豆粉,研究了其对面粉流变学性质、快速粘度性质及馒头品质影响。粉质试验表明,脱脂活性豆粉可使面团的校正吸水率提高,稳定时间提高(除1.0%略低于空白外),形成时间缩短,粉质指数提高,弱化度降低;快速粘度特性结果表明,脱脂活性豆粉可使面粉峰值粘度、低谷粘度、崩解值和最终粘度降低,糊化温度(除2.5%)提高;馒头实验表明,脱脂活性豆粉可以提高馒头表面白度,增加成品质量和体积。     

脱脂麦胚蛋白的制取和理化及其功能特性的研究

本文用碱提取后等电点沉淀法制取了脱脂麦胚蛋白 ,并对其理化和功能特性进行了研究。结果表明 :脱脂麦胚蛋白氨基酸含量高达 2 6 .793g/ 10 0g ,且种类齐全 ,八种必需氨基酸含量均较高 ;脱脂麦胚蛋白的等电点为 4 .0 ,pH >6 .0时蛋白质溶解指数NSI值可达 70 % ,具有较高的溶解度 ;脱脂麦胚蛋白的乳化活性EA和乳化稳定性ES与牛血清白蛋白近似 ,并略高于酪蛋白 ;脱脂麦胚蛋白具有很好的起泡性FC ,其泡沫稳定性FS稍差 ,但可通过物理、化学或酶处理方法来克服 ;脱脂麦胚蛋白具有非常理想的持水性WR ,在pH=8.0和温度 70℃时有最高持水性。     

酶法改性对鹰嘴豆分离蛋白功能性的影响

研究了Alcalase及转谷氨酰胺酶(TGase)酶法改性对鹰嘴豆分离蛋白(CPI)的溶解性及乳化性的影响。CPI经A1calase水解60min(DH5.91%),低离子强度对溶解性不再有负面影响;CPI水解30min(DH5.80%),无盐或0.1mol/L NaCl条件下,蛋白质的乳化活力分别是未改性前的1.22和2.78倍。TGase对CPI在0.1mol/L NaCl条件下的溶解性及乳化活力不能起到良好的改善作用。