大豆浓缩蛋白的酶水解改性的研究

以产品纯度高、反应温和的酶水解作为大豆浓缩蛋白的改性方法,以氮溶解指数为考察指标,通过木瓜蛋白酶和1398中性蛋白酶单酶水解和双酶混合水解大豆浓缩蛋白单因素和正交试验进行分析比较,表明双酶混合水解效果优于单酶水解,其最佳工艺条件为:底物浓度为6.5%、pH为6.5、温度为55℃、反应时间为3 h、混合酶浓度为5 000 U/g,大豆浓缩蛋白的氮溶解指数可以恢复到81.94%,具有较高的工业化应用前景。     

木瓜蛋白酶控制水解蚕豆水溶性蛋白及水解度对蚕豆蛋白功能性质的影响

针对蚕豆蛋白在pH较低的体系中溶解性差、乳化能力低,制约其在食品工业中应用等问题,应用808Titrando瑞士万通全自动滴定仪控制木瓜蛋白酶水解蚕豆蛋白,实现蚕豆蛋白的有限水解,探讨水解度对蚕豆蛋白水解物的溶解性、乳化能力及持水性等功能性质的影响。通过木瓜蛋白酶的控制水解获得水解度为2%～4%的蚕豆蛋白水解物;与蚕豆蛋白相比,在pH4.0～6.0体系、水解度为4%的蚕豆蛋白水解物的溶解度提高2～3倍;pH6.0、水解度为2%的蚕豆蛋白水解物的乳化能力是蚕豆蛋白的2.3倍,持水力是蚕豆蛋白的1.6倍。     

Interference by cyanide with the measurements of papain hydrolysis

Potassium cyanide, a commonly used activator for the proteolytic enzyme papain, may be bound by the Strecker reaction to form cyanohydrins in digestion mixtures. The formation of these N-containing complexes depends on the pH of the digest, incubation time and temperature, and the amount of reducing sugar present. They are soluble in 5% trichloroacetic acid (TCA), so the N in the complexes will be estimated together with the non-protein N released during digestion. Their formation probably accounts for some experimental discrepancies observed when studying the action of KCN-activated papain on extracted leaf proteins, and calculating the percentage hydrolysis from the amount of N found in the TCA-soluble fraction. A procedure for digesting leaf proteins by papain is described that uses thioglycollic acid as activator, and the N is estimated in the undissolved substrate and the TCA-precipitable fraction, instead of in the TCA-soluble fraction.     

木瓜蛋白酶水解发酵豆粕优化工艺研究

豆粕是饲料工业中应用最为广泛的植物性蛋白原料,本试验以微生物固态发酵豆粕粉为原料,以蛋白质增加量、游离氨基酸增加量和水解度为品质指标,探讨了酶解初始pH值、料液比、酶用量和酶解时间对木瓜蛋白酶酶解发酵豆粕的影响。在单因素实验基础上,采用L9(34)正交试验进行优化,结果表明酶解的最佳工艺条件为：酶解初始pH6.5,酶用量3%,料液比1∶10,酶解时间1 h。在该条件下,酶解豆粕中蛋白质增加量为75.633 mg/g,游离氨基酸增加量为121.932 μg/g,水解度为0.033%。     

青鳞鱼蛋白木瓜蛋白酶控制水解动力学模型的研究

在假设木瓜蛋白酶恒温控制水解动力学遵循外切酶限制水解动力学历程的前提下,采用实验方法求出了木瓜蛋白酶恒温控制水解动力学模型.结果表明,木瓜蛋白酶对青鳞鱼蛋白进行控制水解的动力学模型为:R=(92.16e0-0.00005s0)exp(-0.115DH),DH=8.696 ln[1 (10.923e0/s0-0.0008)t];其酶失活常数Kd=10.923 min-1;水解反应能够顺利进行的条件是:e0/s0＞c0,常数c0=5.4×10-7.验证实验证明,根据木瓜蛋白酶恒温控制水解动力学模型得到的理论DH与实际DH基本吻合,该动力学模型具有很强的实用价值.     

低限度酶水解对醇法大豆浓缩蛋白分散性的影响

以大豆浓缩蛋白的分散时间和分散稳定时间为主要指标,研究了大豆浓缩蛋白经过Alcalase酶低限度水解后,分散时间和分散稳定时间的变化情况,并考察了低限度酶水解对分子量分布的影响。      

低限度酶水解对醇法大豆浓缩蛋白分散性影响

以大豆浓缩蛋白分散时间和分散稳定时间为主要指标,研究大豆浓缩蛋白经过Alcalase酶低限度酶水解后,分散时间和分散稳定时间变化情况,并考察低限度酶水解对分子量分布影响。     

In-vitro multienzyme digestibility of protein of some plant source flours blended with bovine plasma protein concentrate

The in-vitro multienzyme protein digestibilities of the flours of maize, cassava, pigeon pea (Cajanus cajan), African yambean (Sphenostylis stenocarpa) and bambara groundnut (Vigna subterranea), blended with bovine plasma protein concentrate were investigated. The multienzyme system consists of trypsin, chymotrypsin and peptidase. It was found that the addition of bovine plasma protein concentrate improved the protein digestibility of the flours compared with flours without the additive. The digestibilities were increased by between 3% in bambara groundnut blended flour to about 10% in cassava blended flour. When the flours were wet-heat treated, the digestibilities further increased in all samples with increments between 7·5 % in bambara groundnut and 16·6% in cassava flour. Bovine plasma protein concentrate may be a good source of protein for the fortification of protein-deficient foods, particularly maize and cassava flours.     

木瓜蛋白酶酶解黑豆制备多肽

以黑豆豆粕粉为主要原料,经木瓜蛋白酶水解成多肽。通过一系列单因素和正交实验,确定黑豆多肽的最佳水解工艺条件,根据四肽标准曲线得出多肽转化率。结果表明:最优实验方案为豆粕粉浓度为0.01g/mL,酶解温度为60℃,酶活为40000U/g,酶解7h,此时黑豆蛋白水解度最大,黑豆多肽转化率为63.53%。各因素对实验的影响主次依次为温度、时间、豆粕粉含量、酶活。      

木瓜蛋白酶酶解黑豆制备多肽

以黑豆豆粕粉为主要原料,经木瓜蛋白酶水解成多肽.通过一系列单因素和正交实验,确定黑豆多肽的最佳水解工艺条件,根据四肽标准曲线得出多肽转化率.结果表明:最优实验方案为豆粕粉浓度为0.01 g/mL,酶解温度为60℃,酶活为40000U/g,酶解7h,此时黑豆蛋白水解度最大,黑豆多肽转化率为63.53％.各因素对实验的影响主次依次为温度、时间、豆粕粉含量、酶活.     

磁性固定化胰蛋白酶水解乳清蛋白及清除DPPH研究

利用氨基化磁性高分子固定化胰蛋白酶对乳清浓缩蛋白进行水解优化,得出水解条件为:底物质量浓度80 g/L,E/S为1400 U/g(底物),pH值为7.0,温度50℃,水解时间4 h.并且对不同水解度水解产物的清除DPPH能力进行研究,得出当水解度10%左右清除DPPH能力最大.     

In vitro protein digestibility of legumes cooked with spices

The present study was planned to investigate the effect of spices on in vitro protein digestibility in decorticated forms of bengal gram (Cicer arietinum), black gram (Phaseolus mungo), green gram (Phaseolus radiatus) and red gram (Cajanus indicus). The spices used were chilli (Capsicum annum), pepper (Pepper nigrum L.), coriander (Coriander sativum) and a mixture of these. Legumes were pressure cooked with 5.0% of freshly powdered spices and in vitro protein digestibility determined using pepsin and pancreatin enzymes by standard techniques. Samples without spices served as controls. The results reveal that protein content of legumes ranged from 20.5 to 23.0 g/100 g. The percent protein hydrolysed for legumes without spices were 63.4 for bengal gram, 65.8 for black gram, 60.0 for green gram and 55.4 for red gram. Casein sample could be hydrolysed to the extent of 78.8%. Chilli powder decreased digestibility significantly by 50, 78, 73, 60 and 69% in casein, bengal gram, black gram, green gram and red gram, respectively. Pepper exhibited a variable effect of altering the digestibility to 93% in casein and red gram, 106% in black gram and green gram and 98% in bengal gram, which were not significant. Coriander also decreased digestibility by 48, 76, 87, 77 and 73% and mixture of spices by 74, 91, 96, 96 and 82% in casein, bengal gram, black gram, green gram and red gram, respectively. It can be concluded that spices do influence in vitro protein digestibility in legumes to varying extent.     

玉米黄粉酶解工艺条件研究

研究木瓜蛋白酶水解玉米黄粉蛋白最佳工艺,通过单因素实验研究底物浓度、酶底比和酶解时间对制备工艺影响,并经正交实验,结果表明,木瓜蛋白酶水解玉米蛋白最佳工艺条件为:底物浓度5.0%,酶底比0.4%,pH6.5,温度50℃,进行酶解4小时水解度最高,此条件下水解度可达39.29%。     

The in vitro hydrolysis of leaf proteins. I.—The action of papain on protein extracted from the leaves of Zea mays

Maize leaf protein is not digested by papain at 37°, under conditions in which casein is hydrolysed. An increase in temperature has more effect on both the initial rate of reaction, and the final amount of hydrolysis, than an increase in enzyme concentration. Maximum digestion is observed at pH 6-6 and 70° using KCN-activated papain: 70% of the substrate N is hydrolysed to non-protein N. De-fatting of the protein by neutral solvent mixtures results in only a slight increase in digestion. Soluble N-containing fractions precipitable by TCA occur at all pH values, but most at pH 7.5 and above. Digestion leads to almost complete solution of the leaf protein at pH 8.6 but the percentage of hydrolysis never exceeds that at pH 6.6. These soluble fractions resemble those found in similar digests of seed proteins. Though in vivo experiments show that protein made from mature wheat leaves has a higher nutritive value than protein from young leaves, there is no corresponding increase in the in vitro digestibility of protein extracted from maize leaves of increasing maturity.     

The in vitro hydrolysis of leaf proteins. II.—The action of papain on protein concentrates extracted from leaves of different species

The in vitro digestion by papain of protein concentrates extracted from 14 different species of leaves is described. The extent of hydrolysis varies with species and is probably influenced by preparative technique. The effect of leaf age is less certain: most proteins made by the current standard procedure from any one species, at all stages of growth, have similar digestibilities, but the digestibility of some preparations from mature leaves is less in vitro, but more in vivo, than of preparations from young leaves. The hydrolysis of some fractionated proteins, prepared by controlled heating of leaf extracts, is also described. For all the species examined the ‘chloroplastic’ fraction is digested less, and the ‘cytoplasmic’ fraction more, than the corresponding whole protein: these results agree with those previously obtained in vivo. Differences in the N contents and in vitro digestibility of laboratory-prepared fractions and those made on a large scale are discussed. Simulated whole protein, made by combining ‘chloroplastic’ and ‘cytoplasmic’ fractions in the correct proportions, is not hydrolysed to the same extent as the corresponding whole concentrate. The percentages of ‘chloroplastic’ and ‘cytoplasmic’ protein, made by the method described here, varies with species, but the ratio seems not to alter as the leaf matures; this could explain the consistent in vitro results usually obtained with recent preparations, irrespective of leaf age. It is suggested that protein digestibility could be assessed rapidly by the method described here as a preliminary to the more thorough, but slower, in vivo tests.     

脱脂麦胚蛋白的酶法制备及其理化性质的研究

选用木瓜蛋白酶水解制备脱脂麦胚蛋白,通过正交实验确定酶水解的最佳条件为:T=60℃,[E]/[S]=3000∪/g,pH6,t=60min,提取率可达92.43%,并对提取到的脱脂麦胚蛋白进行溶解度及氨基酸含量的测定。结果表明,脱脂麦胚蛋白的等电点为4.0,在碱性条件下,麦胚蛋白的溶解度较好;脱脂麦胚蛋白的氨基酸种类齐全,8种必需氨基酸含量均较高。     

Effect of processing methods and protein content of the concentrate on the properties of milk protein concentrate with 80% protein

In recent years, a large increase in the production of milk protein concentrates (MPC) has occurred. However, compared with other types of milk powders, few studies exist on the effect of key processing parameters on powder properties. In particular, it is important to understand if key processing parameters contribute to the poor solubility observed during storage of high-protein MPC powders. Ultrafiltration (UF) and diafiltration (DF) are processing steps needed to reduce the lactose content of concentrates in the preparation of MPC with a protein content of 80% (MPC80). Evaporation is sometimes used to increase the TS content of concentrates before spray drying, and some indications exist that inclusion of this processing step may affect protein properties. In this study, MPC80 powders were manufactured by 2 types of concentration methods: membrane filtration with and without the inclusion of an evaporation step. Different concentration methods could affect the mineral content of MPC powders, as soluble salts can permeate the UF membrane, whereas no mineral loss occurs during evaporation, although a shift in calcium equilibrium toward insoluble forms may occur at high protein concentration levels. It is more desirable from an energy efficiency perspective to use higher total solids in concentrates before drying, but concerns exist about whether a higher protein content would negatively affect powder functionality. Thus, MPC80 powders were also manufactured from concentrates that had 3 different final protein concentrations (19, 21, and 23%; made from 1 UF retentate using batch recirculation evaporation, a similar concentration method). After manufacture, powders were stored for 6 mo at 30°C to help understand changes in MPC80 properties that might occur during shelf-life. Solubility and foaming properties were determined at various time points during high-temperature powder storage. Inclusion of an evaporation step, as a concentration method, resulted in MPC80 that had higher ash, total calcium, and bound calcium (of rehydrated powder) contents compared to concentration with only membrane filtration. Concentration method did not significantly affect the bulk (tapped) density, solubility, or foaming properties of the MPC powders. Powder produced from concentrate with 23% protein content exhibited a higher bulk density and powder particle size than powder produced from concentrate that had 19% protein. The solubility of MPC80 powder was not influenced by the protein content of the concentrate. The solubility of all powders significantly decreased during storage at 30°C. Higher protein concentrations in concentrates resulted in rehydrated powders that had higher viscosities (even when tested at a constant protein concentration). The protein content of the concentrate did not significantly affect foaming properties. Significant changes in the mineral content are used commercially to improve MPC80 solubility. However, although the concentration method did produce a small change in the total calcium content of experimental MPC80 samples, this modification was not sufficiently large enough (<7%) to influence powder solubility.