The effects of post-harvest handling on physical,chemical and functional properties of cowpea (Vigna unguiculata) seed

Damage by insects and mould, proximate composition, cooking rate and functional properties of sun-dried and stored cowpea (Vigna unguiculata) seeds were evaluated. Cowpea samples spread between black polythene films were placed on cement (CS), Wooden (WS) and corrugated iron sheet (CIS) surfaces, respectively, and sun-dried for 5 h. Storage lasted 6 months in jute and polythene bags. Results show that sun-drying and storage in polythene bags significantly (p < 0.05) lowered the extent of insect and mould damage, moisture-loss at drying, emulsion activity and stability, foaming capacity and foam stability. Treated cowpea seeds could be stored safely for about 5 months. In contrast, storage in jute bags significantly (p < 0.05) lowered only foam stability. Moisture loss during sun-drying principally lengthened cooking time as storage duration progressed. Therefore, assessment of moisture content before and during storage is a preferred quality index of cowpea seeds stored in polythene bags. © 1999 Society of Chemical Industry     

酶改性大豆分离蛋白的制备及产品功能性的研究

为了改善碱溶酸沉法大豆分离蛋白产品(简称SPI)的功能性,采用有限酶解的方法,从6种蛋白酶中选出中性蛋白酶(Neutrase)作为改性用酶.通过单因素实验,分析了底物浓度,E/S,反应时间对水解度和氮收率的影响,并通过正交实验确定制备酶改性大豆分离蛋白(简称ESPI)的最佳工艺参数为:底物浓度为3%,E/S为1 200U/g,时间为60 min.得到的ESPI的蛋白含量与SPI相近,但NSI由SPI的90%提高到97%.而且在功能性方面,ESPI也得到了很好的改善,尤其是乳化性和起泡性.     

Preparation and Characterization of Protein Isolate from Cowpea (Vigna unguiculata L. Walp.)

ABSTRACT: Protein isolate (PI) was prepared from 3 cowpea varieties and 2 soybean varieties in each of 2 y. The protein contents of cowpea PI (CPI) (91.4% to 91.8%) and soy PI (SPI) (93.0% to 93.5%) were significantly different ( P < 0.05). Electrophoretogram showed that CPI was concentrated at 60 and 40 kDa, whereas SPI showed bands at 95, 65, 60, 40, and 35 kDa. The CPI had higher lysine (49.3 to 51.8 mg/g) than SPI (41.9 to 43.4 mg/g). The CPI and SPI had surface hydrophobicities ranging from 387.8 to 572.9 and 640.6 to 643.1, respectively. Denaturation temperature (85.2 to 88.4 °C) and enthalpy (8.42 to 10.33 J/g) of CPI were similar to the 7S fraction of SPI (82.6 °C and 96.0 to 96.3 J/g). These characteristics of CPI might be useful to explain its functionalities for application in food systems.     

榛子分离蛋白提取及其功能特性的研究

以低变性榛子饼为原料,经脱脂后采用碱提酸沉法提取榛子分离蛋白,确定了最佳提取工艺条件,并分析了榛子分离蛋白的功能特性.结果表明,提取榛子分离蛋白的最佳工艺条件为:料液比1:15,碱提pH9.0,碱提温度50℃,碱提时间70 min,酸沉pH4.5.最佳条件下榛子分离蛋白的溶解性、持水性和吸油性分别为34.0%、2.6 mL/g和2.15 mL/g,乳化性、乳化稳定性、起泡性和泡沫稳定性分别为61.2%、85.0%、86.5%和24.0%,榛子分离蛋白的等电点为4.52.     

Effect of a microbial calcium‐independent transglutaminase on functional properties of a partially purified cowpea (vigna unguiculata) globulin

A partially purified globulin from cowpea seeds was polymerised by calcium‐independent microbial transglutaminase. The level of free amino groups in the globulin decreased with increase in enzyme concentration, suggesting that the cross‐linking reaction involved participation of the amino residues. At transglutaminase concentrations of 6–18 μg ml⁻¹ emulsifying activity decreased with increasing enzyme concentration and degree of cross‐linking, while a similar trend was observed for the foaming property at 6–12 μg ml⁻¹ transglutaminase concentrations. The resultant emulsions and foams formed by the cross‐linked proteins were more stable than those formed by the untreated protein. Sodium dodecyl sulphate polyacrylamide gel electrophoresis showed that of the two major polypeptides, the 55 kDa protein was more susceptible to transglutaminase action than the 50 kDa protein. Scanning electron microscopy revealed an amorphous structure for the control protein gel while a more defined and cross‐linked gel structure was observed for the protein treated with transglutaminase. The results suggest that protein products differing in functionalities can be obtained by controlling the degree of enzymatic protein cross‐linking. © 1999 Society of Chemical Industry     

乙酰化大豆分离蛋白的功能特性研究

本文采用乙酸酐对大豆分离蛋白进行改性。测定了改性前后,不同改性程度下大豆分离蛋白功能特性的变化。结果表明：乙酰化大豆蛋白在5.0-9.5范围内大大提高发泡性能、乳化性能,并使等电点朝酸性偏移。     

赤藓糖醇对豌豆分离蛋白结构和功能特性的影响

为研究赤藓糖醇对豌豆分离蛋白结构和功能特性的影响,利用8-苯胺基-1-萘磺酸钠荧光探针法、紫外和荧光光谱法,研究赤藓糖醇对豌豆分离蛋白溶解性、持水性、起泡性、乳化性及表面疏水性等的影响。结果表明:随赤藓糖醇质量分数的增加,豌豆分离蛋白的溶解性基本呈先增加后下降趋势,且均在pH4.0处最低。持水性逐渐增加,且均在pH5.0处最低。起泡性和乳化性均先增加后趋于平稳。当赤藓糖醇质量分数在0~10%范围内,表面疏水性逐渐增加,随后趋于稳定。随赤藓糖醇质量分数增加,色氨酸残基暴露在蛋白质分子表面,荧光强度先增加后趋于稳定,且与表面疏水性变化趋势相同。该研究表明,适度赤藓糖醇处理可改善豌豆分离蛋白的结构和功能特性。     

热烘改性对大豆分离蛋白功能性的影响

研究了利用热处理对大豆分离蛋白(SPI)进行改性。热烘改性对SPI的吸水性、吸油性、发泡性和泡沫稳定性无显著性影响,常温粘度、高温粘度、耐热性、凝胶性和保水性分别比对照提高了118%、135%、108%、81%和83%。比较适宜的热烘改性条件为10min/85℃。     

Functional Properties of Protein Isolate from Cowpea (Vigna unguiculata L. Walp.)

ABSTRACT: Functional properties of protein isolates prepared from 3 cowpea varieties and 2 soybean varieties in each of 2 y were determined. Both cowpea protein isolate (CPI) and soy protein isolate (SPI) showed a u-shaped curve for solubility with the minimum solubility occurring at pH 4.5. The CPI had lower emulsifying activity than SPI but was similar in stability. Foaming capacity and foaming stability ranged from 58.6 to 60.2 mL and 63.7 to 64.4 min for CPI and from 31.9 to 33.0 mL and 43.4 to 45.0 min for SPI, respectively. Gels were formed at 70 °C for 40 min and 30 min for CPI (12%) and SPI (10%), respectively. The CPI needs modification to enhance functional properties for potential application in food products.     

高压均质对大豆分离蛋白功能性质的影响

为了了解高压均质技术对大豆分离蛋白（SPI）功能性质的影响,采用不同的均质压力、均质次数和料液比对大豆分离蛋白溶液进行了高压均质处理,并分析处理前后SPI功能性质的变化.结果表明：高压均质可在一定程度上提高SPI的溶解性、乳化活性及其稳定性和起泡性及泡沫稳定性.均质压力在0～70 MPa的范围内升高时,SPI的溶解性、乳化稳定性、起泡性和泡沫稳定性得到了相应的改善,而乳化活性在压力为40 MPa时达到最高;均质次数由1次向3次增加时,SPI的乳化稳定性、起泡性及泡沫稳定性得到了提高,而溶解性和乳化活性则降低;均质物料料液比在1∶16～1∶8 （g∶mL）的范围内逐步增大时,SPI的各项功能性质均有不同程度的提高,并在料液比为1∶8时达到了最高值.     

Inheritance of protein content in seeds of selected crosses of cowpea (Vigna unguiculata)

The inheritance pattern of protein content in seeds of two crosses of cowpea (Vigna unguiculata (L) Walp) was studied. It was observed that, in both crosses, inheritance of the character involved both additive and non-additive gene effects. Heritability in the broad sense was 0·70–0·78. A significant effect of pollen source was detected in one of the two crosses. In both crosses, comparison of seed protein content of reciprocal segregating generations indicated the influence of cytoplasmic factors.     

Physicochemical and functional properties of a protein isolate produced from safflower (Carthamus tinctorius L.) meal by ultrafiltration

BACKGROUND: The protein isolate obtained from safflower meal by aqueous extraction and ultrafiltration was evaluated for its physicochemical and functional properties. RESULTS: Protein, ash and moisture contents of the safflower protein isolate were 901, 51 and 45 g kg^?1 respectively. Its water and oil absorption capacities were 2.22 mL H₂O g^?1 protein and 2.77 mL oil g^?1 protein respectively. Least gelation concentration was 20 g kg^?1 at pH 2, 6, 8 and 10 but 100 g kg^?1 at pH 4. Emulsifying properties were also affected by the pH: emulsifying activity and emulsion stability at pH 6 were 82.5 and 100% respectively. The highest foaming capacity (126%) occurred at pH 2; however, it increased by 104% with the addition of 0.25 g glucose g^?1 protein to the foam system. CONCLUSION: In the light of its functional properties found in this study, safflower protein isolate produced by ultrafiltration is recommended for use as an ingredient in food products such as salad dressing, meat products, mayonnaise, cakes, ice cream and desserts. Copyright © 2010 Society of Chemical Industry     

不同酶切方式对乳清蛋白疏水性和乳化性的影响

采用不同的蛋白酶对乳清蛋白进行水解,考察了肽键断裂方式对乳清蛋白肽疏水性和乳化性的影响,以及乳清蛋白不同酶解产物的疏水性和乳化性的关系。结果表明:不同蛋白酶作用于乳清蛋白得到的水解产物疏水性不同,6种蛋白酶解液的疏水性均随水解度的增大而降低,其中以胰凝乳蛋白酶酶解液的疏水性下降的最慢。研究还发现,乳化性随着水解度增加而先升高后下降,以双酶复合酶解液最差。不同蛋白酶水解液的乳化性指数随疏水性指数的降低而升高,乳化性指数与疏水性氨基酸质量分数成正相关。     

超声物理改性对SPI功能特性的影响

采用超声仪对大豆分离蛋白（SPI）溶液进行超声处理，研究了不同超声处理时间，不同功率处理后SPI功能特性的变化。结果表明，超声处理后大豆分离蛋白的溶解性、起泡性、乳化性和凝胶性都有明显的提高。     

大豆分离蛋白的功能特性

叙述了分离蛋白功能特性的定义 ,并分别介绍了大豆分离蛋白主要的功能特性及影响其功能特性的因素     

白木通籽分离蛋白的理化与功能性质研究

以白木通籽为原料,采用碱提酸沉法,制备白木通籽分离蛋白（API）,并对其理化性质与功能性质进行了分析。结果表明:白木通籽分离蛋白含17种氨基酸,其中谷氨酸和天门冬氨酸的含量相对较高,有贮藏蛋白的共性。苏氨酸为白木通籽分离蛋白的第一限制性氨基酸。通过SDS-PAGE分析,白木通籽分离蛋白的亚基分子量范围为25～35ku。圆二色性光谱分析表明,白木通籽分离蛋白的二级结构主要由β-折叠和无规则卷曲组成,含量分别为31.2%和36.6%。白木通籽分离蛋白的等电点在pH4～5之间,在此pH范围内,蛋白的溶解性和起泡能力均最低。      

Influence of cowpea (Vigna unguiculata L Walp) variety on protein quality and sensory properties of akara,a popular West African cowpea‐based food

The influence of newly developed cowpea varieties (IT81D‐699, IT82E‐18, IT84S‐2246‐4 and TV_x3236) on the proximate composition, protein quality and sensory properties of akara, a popular West African cowpea‐based food, was investigated and the results obtained were compared with those for akara prepared from a local blackeye cowpea variety. Protein quality was evaluated using weanling albino rats fed diets which were formulated to supply 10% protein using defatted akara samples, with casein as a control. Akara samples prepared from IT81D‐699 and TV_x3236 had crude protein contents, texture and overall acceptability comparable to those of akara prepared from the blackeye variety. Also, akara diets formulated using IT81D‐699 and TV_x3236 showed significantly (p < 0.05) higher values for weight gain, protein efficiency ratio, net protein ratio and true digestibility than diets formulated with IT82E‐18, IT84S‐2246‐4 and blackeye, suggesting an improvement in the nutritional quality of akara produced using these (IT8ID‐699 and TV_x3236) newly developed cowpea varieties. Copyright © 2004 Society of Chemical Industry     

使用圆二色性光谱分析二级结构对大豆分离蛋白表面疏水性的影响

旨在采用圆二色性光谱手段研究二级结构对我国六种经常使用的大豆品种制备而成的分离蛋白的表面疏水性的影响。实验先是对六个品种的大豆进行分离蛋白的提取,并对其性质进行测定,包括溶解度和表面疏水性;再对六种大豆分离蛋白的二级结构进行测定和分析;通过SPSS软件对六种大豆分离蛋白的表面疏水性和二级结构的数值进行线性相关性分析,探究二者之间的构效关系。研究中发现六个品种的大豆分离蛋白的二级结构、溶解性、表面疏水性都差异显著（p<0.05）,表面疏水性的大小随着α-螺旋含量升高而减小,随着无规则卷曲和β-折叠含量增大而提高,因β-转角含量变化的影响不明显。SPSS线性相关性分析表明品种间的表面疏水性与β-转角含量线性关系不显著,与无规则卷曲、β-折叠含量呈正向相关,与α-螺旋含量呈负向相关。      

Comparative studies of some properties of undehulled, mechanically dehulled and manually dehulled cowpea (Vigna unguiculata Walp. L.) flours

A comparative evaluation was made of some physico‐chemical and rheological characteristics of undehulled, manually dehulled and mechanically dehulled cowpea (Vigna unguiculata Walp. L.) flours from brown and white varieties of the legume. The flours were used to prepare steamed bean paste, ‘Moinmoin’, which was analysed for some sensory parameters. Dehulling and dehulling methods had no appreciable influence on the physical characteristics and proximate composition of the flours, except ash content, which was slightly higher in undehulled flour samples. Amylograph pasting characteristics of the flours showed varying trends because of dehulling method and/or presence of seed coats. ‘Moinmoin’ samples prepared from the flours received similar ratings for all sensory attributes, with no significant differences (P < 0.01 and P < 0.05), except for the low‐rated (poorer) colour of the undehulled brown product.