胰蛋白酶有限水解蚕豆盐溶性蛋白的研究

研究了胰蛋白酶水解蚕豆盐溶蛋白的动力学及其水解物的水溶性。高压液相色谱的实验结果证实胰蛋白酶可以水解蚕豆盐溶蛋白。底物浓度5%、酶与底物之比(E/S)为10U/g蛋白质、pH8.0、温度45℃的酶反应条件下,水解6000s时的蚕豆盐溶性蛋白的水解度达到6.8。蚕豆盐溶蛋白经过胰蛋白酶有限水解后水溶性显著增加,与蚕豆盐溶性蛋白相比,pH8.0时水解度2.1%、4.5%、6.8%的蚕豆盐溶性蛋白水解物的水溶性分别提高350%、390%和510%。     

脱脂小麦胚芽的蛋白酶法水解及其蛋白水解物的功能性质

研究了不同蛋白酶对脱脂小麦胚芽的水解特性.实验发现,碱性蛋白酶和复合风味酶可溶出脱脂小麦胚芽中蛋白质的80%,而木瓜蛋白酶、中性蛋白酶和复合蛋白酶则相对较低.对采用碱性蛋白酶得到的脱脂小麦胚芽蛋白水解物(DWGP)的功能性质进行了研究,pH值为6.0时氮溶指数约为70%,中性条件下乳化活性、乳化稳定性及乳化能力分别为64%,57%及62%.在pH值为7和70℃,持水性为232%.DWGP可作为一种潜在的功能性蛋白资源应用于食品中.     

酶水解制备猪血浆蛋白抗氧化肽工艺参数的优化

对猪血浆蛋白的水解条件进行优化,并对其不同水解条件下水解物的抗氧化性进行了研究.采用碱性蛋白酶、中性蛋白酶、风味蛋白酶、复合蛋白酶、胰蛋白酶以及木瓜蛋白酶制备猪血浆蛋白水解物,用pH-Stat法测定其水解度,通过测定卵磷脂脂质氧化体系的抑制作用和亚铁还原能力,来研究水解物的抗氧化能力.结果表明,猪血浆蛋白水解物的抗氧化能力与酶的种类、底物是否经预热处理及水解度的大小有关,筛选出碱性蛋白酶为最佳用酶;通过测定不同底物浓度、不同酶与底物浓度比以及不同水解时间的水解物的TBARS值(硫代巴比妥酸值)和还原能力,得出底物浓度为4%,酶与底物浓度比为2%,水解时间5h的水解物具有较高的抗氧化能力.     

中性蛋白酶限制性水解对高温菜籽粕蛋白功能性质的影响

研究了中性蛋白酶限制性水解菜籽蛋白的功能性质。结果表明,中性蛋白酶水解能显著改善高温菜籽粕蛋白的各种功能性质,限制性水解菜籽蛋白的溶解性随水解度的增加而增加,DH=10的限制性水解菜籽蛋白在pH7.0时溶解度达57.11%;DH=2的限制性水解菜籽蛋白乳化性最好,其在测定的pH范围内乳化性均较菜籽蛋白提高40%以上;DH=4的限制性水解菜籽蛋白起泡性最佳,可达162.5%;DH=2的限制性水解菜籽蛋白吸油性与吸水性均最好,且分别较原菜籽粕蛋白提高了2.6倍与1.9倍。     

猪血浆蛋白水解物功能特性的研究

将猪血浆蛋白用碱性蛋白酶水解,用pH-Stat方法测定其水解度,制备得到不同水解度的水解样品.测定水解物在不同pH条件下的表面疏水性、溶解性、乳化性和乳化稳定性以及起泡性和起泡稳定性,研究水解度对猪血浆蛋白水解物功能特性的影响.研究结果表明,猪血浆蛋白碱性蛋白酶水解物的溶解性随着水解度的增加而逐渐增大(P<0.05),表面疏水性、乳化性和乳化稳定性以及起泡性和起泡稳定性随着水解度的增加而降低(P<0.05).同时,水解物的表面疏水性、溶解性、乳化性以及起泡性都随着pH的改变而变化.因而猪血浆蛋白碱性蛋白酶水解物可以提高蛋白质的溶解度,但是较高的水解度会在一定程度上降低其乳化性和起泡性.     

大米浓缩蛋白限制性水解及其性质研究

以水解度为依据,比较了4种商品蛋白酶水解大米浓缩蛋白的效率.碱性蛋白酶具有最高的水解效率,其最佳水解条件为温度50℃～60℃,pH8.5,加酶量1%(E/S),底物浓度6%.考察了频率40 kHz,功率40 W～100 W的超声波对碱性蛋白酶水解的辅助作用.超声波在蛋白水解初期有一定加速度作用,不同的超声功率对水解速率影响并不显著.在蛋白水解水解度2%～10%范围内,用碱性蛋白酶制备了不同水解度的大米蛋白产品,并比较了他们溶解性、发泡性和持泡性以及口感.蛋白质的水解度与溶解性呈正相关,在水解度≥8%之后蛋白水解产物的开始出现苦味.蛋白质的持泡性随水解度的增加有一定改善,起泡性未见改善.     

碱性蛋白酶限制性水解对高温菜籽粕蛋白功能性质的影响

为改善高温菜籽粕蛋白质的功能性质,用碱性蛋白酶对其进行限制性水解,并研究不同水解度(DH)高温菜籽粕蛋白功能性质及相对分子质量分布。结果表明：碱性蛋白酶限制性水解高温菜籽粕蛋白的溶解度、乳化性和吸油性均有所改善,其中溶解度随水解度增加而增加,pH7.0 时DH为10% 的高温菜籽粕蛋白的溶解度达63.82%,是原蛋白溶解度的2.1 倍;DH 为2.0% 的水解蛋白乳化性最好,pH6.0 和pH8.0 时乳化指数分别为0.43 和0.49,比原蛋白乳化指数分别高0.13 和0.11;DH 为8% 的水解蛋白吸油性最好,为4.39g/g。水解后高温菜籽粕蛋白的某些功能性质与其相对分子质量分布有一定的关系,需控制高温菜籽粕蛋白水解度以获得某种良好的功能性质。     

胃蛋白酶水解大米蛋白的研究

采用胃蛋白酶对大米蛋白进行水解以改善其功能性质。结果表明,酶添加量7U/g(以蛋白质干基计)、pH1.5、时间5h、温度30℃时,胃蛋白酶对大米蛋白溶解性有较好的改善作用。水解后大米蛋白的乳化稳定性与乳化性分别为33.28min、0.456,高于大豆蛋白和鸡蛋清蛋白;起泡性和起泡稳定性比未经过任何处理的大米蛋白分别提高了25.0%、82.4%;持水性和持油性为2.80、3.30g/g,是未经处理的大米蛋白的2.09、2.92 倍。     

酶解小麦面筋蛋白及其组分功能特性研究

利用木瓜蛋白酶对谷朊粉功能特性进行改良,在pH7.0的条件下,研究时间对水解度的影响以及水解度对乳化活性和溶解度的影响,水解度为2.4%时,乳化活性可以达到72.5%.通过响应面实验,研究酶浓度、底物浓度、pH值、反应时间、反应温度对谷朊粉乳化活性和溶解性的影响,探索木瓜蛋白酶水解谷朊粉提高乳化性和溶解性的最佳反应条件,分析发现5个因素对谷朊粉乳化性的影响由强到弱的顺序为酶浓度、谷朊粉浓度、时间、温度和pH值.最佳水解条件为:酶浓度0.475%、反应温度60℃、反应时间1.63 h、pH6.6、底物浓度4%,此时的水解度为4.32%、乳化活性为63.4%、溶解度则为19.04%.经过超滤(10 ku)后得到的截留组分乳化活性与酶解面筋蛋白接近.     

酶法水解对罗非鱼下脚料蛋白功能特性的影响

以罗非鱼下脚料为原料,采用Alcalase蛋白酶、中性蛋白酶、风味蛋白酶对其进行控制酶解,通过pH-stat法控制水解程度,制备不同水解度(1.0%～15.0%)的罗非鱼下脚料酶解蛋白,探讨酶的种类和水解度对其乳化性和发泡性的影响。结果表明:在水解度较低(3.0%～5.0%)时,酶解蛋白的乳化性和发泡性较好,随着水解度进一步增大,酶解蛋白的乳化性和发泡性均降低;比较而言,由中性蛋白酶水解得到的酶解蛋白乳化性较好,而风味蛋白酶水解得到的酶解蛋白发泡性较好;此外,pH值(2～10)对轻度酶解蛋白的乳化性和发泡性影响较大,在pH 4.0～5.0范围内,酶解蛋白的乳化性和发泡性最差。     

罗非鱼头蛋白质的提取及性质研究

以罗非鱼头为原料,采用加热浸提、酶法水解、酸/碱溶解-等电点沉淀法提取鱼蛋白,冷冻干燥得到4种鱼蛋白粉,分别记为热提鱼蛋白(HFP)、酶解鱼蛋白(EFP)、酸溶鱼蛋白(AFP)和碱溶鱼蛋白(ALFP),并探讨了4种鱼蛋白的营养特性、溶解性和乳化性。结果表明:ALFP和AFP的蛋白含量分别为89.97%和85.87%,必需氨基酸占总氨基酸的比例达到49.72%和48.63%,而脂肪和灰分含量以及白度值均低于HFP和EFP,且差异显著(P<0.05)。溶解性和乳化性的研究显示,EFP和HFP在pH 2.0～10.0内溶解度均高于93%,但体系的乳化活性和稳定性较差;而AFP和ALFP的溶解度随pH值的变化非常明显,在pH 4.0～6.0内,体系的溶解性和乳化性极差,而在pH值低于4.0或高于6.0时,溶解度大大增强,乳化活性和乳化稳定性随之提高,且乳化活性和稳定性明显高于HFP和EFP。酸/碱溶解-等电点沉淀法可用于制备营养价值高,乳化特性相对较好的鱼分离蛋白。     

碱性蛋白酶限制性酶解对蓝圆鲹分离蛋白功能特性的影响

以蓝圆鲹(Decapterus maruadsi)分离蛋白为原料,采用碱性蛋白酶对其进行限制性酶解,研究水解度(degree of hydrolysis,DH)对分离蛋白酶解产物溶解性、持油力、乳化性与起泡性等功能特性的影响.结果表明,碱性蛋白酶酶解产物的相对分子质量显著下降.酶解可有效提高分离蛋白的溶解性,其溶解度随...     

Preparation and Functional Properties of Enzymatically Deamidated Soy Proteins

Heat-denatured soy protein was hydrolyzed by Alcalase to 2.0% or 4.0% degree of hydrolysis (DH), heated again at 100°C and deamidated with B. circulans peptidoglutaminase. The extent of deamidation was 6.0% and 8.2% for 2.0 DH hydrolysates and 12.8% and 16.0% for 4.0 DH hydrolysates heated for 15 and 30 min, respectively. Deamidation increased protein solubility and substantially enhanced emulsifying activity under mildly acidic (pH 4–6) as well as alkaline conditions. Deamidation improved emulsion stability and foaming power of heat-denatured hydrolysed soy proteins. Enzymatically deamidated soy protein hydrolysates had improved functional properties compared to nondeamidated hydrolysates and the native soy protein.     

Action of Pepsin on Emulsifying Properties of Globin

The emulsifying properties of bovine globin, extracted by the acidified acetone method, were studied at different pH values and after several times of peptic-hydrolysis. The emulsifying capacity, the emulsifying activity index, and the emulsion stability were determined. In general, the peptic hydrolysis was disadvantageous for the emulsifying properties of globin, since it only increased the emulsifying capacity (at pH = 3.0, after 30 and 60 minutes hydrolysis; at pH = 4.0, after 10 to 60 minutes hydrolysis), and the emulsifying activity index (at pH = 5.0 after 60 minutes hydrolysis; at pH = 6.0 after 15, 30, and 60 minutes hydrolysis). This treatment reduced the emulsion stability in almost all conditions studied.     

加工工艺对荞麦蛋白功能特性的影响

探讨了加工工艺对荞麦蛋白(BWP)功能特性的影响。pH＜5．0和 pH＞6．0时,喷雾干燥制备的荞麦蛋白(SBWP)的溶解度高于商品大豆分离蛋白(SPI)(P＜0．05)。pH＜7．0时,超声协助提取荞麦蛋白(U- BWP)的溶解度较搅拌提取荞麦蛋白(M-BWP)和脱脂、超声协助提取荞麦蛋白(DU-BWP)好；pH＞7．0时,结果相反。总体来说,BWP 持油能力较 SPI 强,且冷冻干燥制备的荞麦蛋白(F-BWP)的持水、持油能力强于 S-BWP (P＜0．05)。BWP 的乳化活性与其溶解度呈正相关。pH 4．0～5．0时,BWP 的乳化活性指数(EAI)最小而乳化稳定性(ES)最高。脱脂处理明显提高了 BWP 的 EAI 和 ES。     

Chemical Modification and Functional Properties of Acylated Beef Heart Myofibrillar Proteins

Beef heart myofibrils were acylated with 0.1, 0.3, 0.6, 0.8, 1.0, 1.5, 2.0, 3.0, and 5.0 mmoles anhydride/g protein, at pH 8.0–8.5 and 2–3°C, with acetic anhydride (AA), succinic anhydride (SA), cis,cis,cis,cis-tetrahydrofuran-2,3,4,5-tetracarboxylic dianhydride (FA), and 1,2,4-benzenetricarboxylic anhydride (BA). The anhydride reacted with e-amino groups of lysine, sulfhydryl groups, and hydroxyl groups of tyrosine, serine, and threonine. Chemically modified beef heart myofibriliar proteins were superior to native heart myofibriliar proteins in solubility, emulsifying capacity, emulsion activity, and emulsion stability in a low salt solution of 0.1M NaCl, 0.05M potassium phosphate at pH 7.4 and 6.0. Protein modified with 0.5 mmole anhydride/g protein in 0.2M NaCl had a solubility greater than unmodified proteins in 0.6M NaCl at pH 7.4. Chemical modification also altered the pH-solubility profile. The chemically modified beef heart myofibrillar proteins exhibited an emulsifying capacity at pH 6.0 and 7.4 that was greater than that of the native proteins at pH 7.4. The recommended extent of acylation for modifying beef heart myofibrils on a gram protein basis is 0.6 mmole AA, 1.5 moles SA, 0.6 mmole FA, and 0.6 mmole BA.     

Effect of Partial Proteolysis and Succinylation on Functionality of Corn Germ Protein Isolate

Corn germ protein isolate (CGPI) was partially hydrolyzed with trypsin and pepsin and succinylated at three levels. Various functional and electrophoretic properties of the native and modified protein were determined. Water absorption and foaming properties of CGPI were Improved by partial hydrolysis with trypsin; emulsifying capacity and nitrogen solubility were reduced; oil absorption was increased only slightly. CGPI pepsin hydrolyzate has decreased oil absorption, nitrogen solubility and emulsifying capacity but improved foaming properties; water absorption was unchanged. Treatment of CGPI with succinic anhydride improved water and oil absorption, nitrogen solubility and foaming capacity but decreased emulsifying capacity; foam stability was unchanged. Succinylation retarded electropohoretic mobility while hydrolysis altered band intensities.     

Functional properties of protein hydrolysates from pea (Pisum sativum,L) seeds

The aim of this study was to investigate the effects of partial enzymatic hydrolysis on functional properties of two different pea protein isolates obtained from two pea genotypes, Maja and L1. Papain and commercial protease (Streptomyces griseus protease) were used for protein modification. Solubility, emulsifying and foaming properties were estimated at four different pH values (3.0, 5.0, 7.0 and 8.0). Papain increased solubility of L1 pea protein isolate at pH 3.0, 5.0 and 8.0, emulsifying properties and foaming capacity at all pH values. Otherwise, papain increased solubility of Maja pea protein isolate only at pH 8.0. This pea protein isolate modified with both enzymes formed emulsions with improved stability at lower pH (3.0, 5.0). The commercial protease‐prepared pea protein isolates showed generally low solubility and different emulsifying and foaming properties. Proper selection of enzyme, conditions of hydrolysis and genotypes could result in production of pea protein isolates with desirable functional properties.     

Functional properties of bovine blood plasma intended for use as a functional ingredient in human food

With the aim of using bovine blood as functional ingredient in food processing, as an emulsifier or fat replacer, a study of some functional properties of blood plasma was made. The effect of pH (3.0–8.0), tryptic hydrolysis and NaCl addition (0.034 mol/L) on the solubility, hydrophobicity and emulsifying properties of bovine blood plasma were studied. The results showed that the hydrophobicity and emulsifying activity index (EAI) of bovine blood plasma reached a maximum at pH 3.0 and 7.0, respectively, while the other parameters stayed nearly constant with pH change. Tryptic hydrolysis improved hydrophobicity at certain hydrolysis times, reduced solubility and emulsifying capacity (EC) and showed no effect on EAI and emulsion stability (ES). The influence of NaCl tested at pH 5.0 and 6.0 was only positive for plasma EAI at pH 5.0 and significantly reduced solubility, hydrophobicity and EC at pH 5.0 and 6.0. For ES, NaCl addition did not produce any modification.