瑞士Bracker钢领与国产轴承钢钢领性能研究

探讨瑞士Bracker钢领与国产轴承钢钢领的组织结构与性能。从微观组织、表面合金层、力学性能等方面对瑞士Bracker钢领与国产轴承钢钢领进行了对比分析。结果表明:瑞士Bracker轴承钢晶粒直径较小,马氏体较为精细,有较高的碳化物含量;表面镀铬层结构致密,与基体结合良好并呈网状沟纹,提高了耐磨性能。指出:应改善国产轴承钢钢领镀铬层及与基体的结合质量,采用松孔处理工艺,可获得具有一定密度和深度的网状沟纹,提高国产钢领的耐磨损性能。     

氢过氧化物裂解酶的筛选及纯化

研究了不同植物原料中氢过氧化物裂解酶的含量,并最后筛选出苋菜作为提取原料。利用高速离心、表面活性剂溶解、硫酸铵分级沉淀、羟基磷灰石柱层析和离子交换色谱对苋菜氢过氧化物裂解酶进行纯化至电泳纯。结果表明,纯化的苋菜氢过氧化物裂解酶分子量约为55ku,对于13-亚麻酸氢过氧化物的活力高于13-亚油酸氢过氧化物,最适pH6.0,最适温度为25℃,在常温下酶能保持较高水平的活力。     

法式风情 城堡家具——走进《我们的法兰西岁月》

东方家具与西方家具作为世界家具的两个体系,向人们展示着家具背后的文化差异性。由于我国海派家具与西方家具有着不可分割的联系,所以西方家具备受一些研究海派家具的学者所关注。笔者有幸来到西洋古堡古董家具公司,目睹了西方不同时期的古董家具。由于其家具种类较为齐全,所以经常和一些影视公司形成合作关系,如为《我的法兰西岁月》、《风声》等剧组提供家具。     

Production of (2E)-hexenal by a hydroperoxide lyase from Amaranthus tricolor and salt-adding steam distillation for the separation

(2E)-Hexenal is widely used in flavors and perfumes; however, it is mainly derived from chemical synthesis. In this study, hydroperoxide lyase (HPL) naturally originated from Amaranthus tricolor was used to catalyze the reaction to generate (2E)-hexenal from 13-hydroperoxy-9Z, 11E, 15 Z-octadecatrienoic acid (13-HPOT), and salt-adding steam distillation was used for the separation of (2E)-hexenal. A maximum yield of (2E)-hexenal that reached 1,156.4?mg?L^?1 was obtained with a high substrate concentration (40?mM 13-HPOT) under the following conditions: 10?min, pH 7.5, 20?°C, HPL 16 U?mL^?1, butylated hydroxytoluene (BHT) 1?mM, and dithiothreitol (DTT) 15?mM. Then the separation of (2E)-hexenal was conducted by salt-adding steam distillation. It was found that AlCl₃ had the greatest effect on the separation of (2E)-hexenal, followed by CaCl₂ and NaCl. The distillate yield with the addition of AlCl₃ was 93.2?%, while the distillate yield without the addition of salt was 81.2?%. The distillate concentration with AlCl₃ was 6,464.2?mg?L^?1, while the distillate concentration without the addition of salt was 4,490.3?mg?L^?1. The addition of salt improved the efficiency of the steam distillation. This study was greatly meaningful for providing a green method to the large-scale production of (2E)-hexenal.     

Effect of heat treatment on the properties of soy protein‐stabilised emulsions

The effect of heat treatment on the properties of soy protein‐stabilised emulsions was investigated. Emulsions were prepared with unheated and heat‐treated soy protein (NSP and HSP) dispersions. Heating on soy protein dispersions at 95 °C for 30 min resulted in smaller average oil droplet size, lower tendency for oil droplet flocculation, higher protein adsorption and lower viscosity. The properties of emulsions were significantly influenced by the protein concentration. The sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) profiles showed that the heat treatment on soy protein dispersions increased the protein adsorption at O/W interface. The viscosity of all samples at low shear rate was inversely proportional to the d₃₂, suggesting a positive relation to the total interfacial area per unit volume. Emulsions showed shear‐thinning behaviour. The relaxation time was found to increase with aqueous phase viscosity determined by the Cross viscosity model.     

响应面分析法优化微波提取密蒙花总黄酮工艺

以水为介质,密蒙花总黄酮提取率为考察指标,优化微波强化提取密蒙花总黄酮的工艺.选取微波功率、微波工作时间和液料比为影响因子,在单因素试验的基础上,进行3因素3水平的Box-Behnken中心组合试验设计.以密蒙花总黄酮提取率为响应值,进行响应面(RSM)分析,优化微波强化提取密蒙花总黄酮的提取条件.试验结果表明,微波处...     

Oxidative modification of soy protein by peroxyl radicals

Oxidative modification of soy protein by peroxyl radicals generated in a solution containing 2,2’-azobis (2-amidinopropane) dihydrochloride (AAPH) under aerobic condition was investigated. Incubation of soy protein with increasing concentration of AAPH resulted in gradual generation of protein carbonyl derivatives and loss of protein sulphydryl groups. Circular dichroism spectra indicated that exposure of soy protein to AAPH led to loss of α-helix structure. Effect of oxidation on tertiary structure was demonstrated by surface hydrophobicity and tryptophan fluorescence. Surface hydrophobicity steadily decreased, accompanied by loss and burial of some tryptophan residues, indicating that soy protein gradually aggregated. The results of the size exclusion chromatogram (SEC) implied that incubation caused an AAPH-dose-dependent increase of fragmentation and aggregation of oxidised soy protein. Sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) indicated that non-disulphide linkages were involved in aggregate formation, and β-conglycinin was more vulnerable to peroxyl radicals than glycinin.     

Influence of different thawing methods on physicochemical changes and protein oxidation of porcine longissimus muscle

The objective of the present study was to elucidate the physicochemical changes and protein oxidation of porcine longissimus muscle as influenced by different thawing methods. Five kinds of thawing methods, comprising of refrigerator thawing (RT, 4 °C), ambient temperature thawing (AT, 20 °C), water immersion thawing (WT, 14 °C), lotic water thawing (LT, 9 °C), and microwave thawing (MT), were used. There were significant effects on the porcine meat quality due to different thawing methods. RT had the least quality loss and the physicochemical characteristics of pork were closer to fresh muscle than the other thawing methods. MT significantly increased thawing loss, cooking loss, cutting force, carbonyl content, and TBARS (thiobarbituric acid-reactive substances) value, but decreased a* value and Ca-, K-ATPase activities (P < 0.05). Microstructural changes in experimental muscle showed that MT induced visibly larger gap between muscle fibers and tore more muscle fiber bundles compared to the other thawing methods. The reduction of Ca- and K-ATPase activities (P < 0.05) of myofibrillar protein was consistent with the increases in carbonyl content and TBARS value (P < 0.05). The results demonstrated all the thawing methods could cause porcine lipid and protein oxidation. Gel electrophoresis patterns of porcine muscle displayed that different thawing methods did not induce obvious protein aggregates and fragments.     

影响凯氏定氮法测定蛋白质准确度的因素探讨

随着客户对产品质量要求的提高,企业对面粉及其副产品的等级评定中蛋白质含量都有了明确要求,对使用的原料小麦的蛋白质含量也有明确验收范围,可见蛋白质测定的准确度非常重要.国标GB 5009.3-2016第一法凯式定氮法检测蛋白一直是最经典的测定方法,凯氏定氮法是由样品消化成铵盐蒸馏,用标准液吸收,用标准酸滴定,测定出样品中...