甘薯热变性蛋白限制性酶解产物的乳化特性研究

采用5种酶(Alcalase 2.4L,As1.398,Neutrase,Pepsin,Trypsin)对甘薯热变性蛋白(SPHP)进行限制性酶解。将各酶解产物离心后分别取上清和沉淀测定和观察其乳化液的乳化颗粒平均粒径(D4,3)、乳化活性指数(EAI)、乳化稳定性指数(ESI)、乳化液的微观结构和表观黏度。结果显示:酶解产物上清和沉淀中蛋白的溶解度均有增加,但沉淀增加的幅度小于上清。SPHP的D4,3是71.96μm,而酶解产物上清和沉淀乳化液的D4,3均减小,且上清的D4,3小于沉淀的。在5种酶解产物中,Pepsin酶解物上清的D4,3最小,为14.94μm。SPHP酶解后上清的乳化颗粒大小较为均一,且沉淀的乳化颗粒酶解前后变化不大。SPHP的EAI为11.21m2/g,酶解产物上清和沉淀的EAI均有显著提高(P<0.05),其中Pepsin酶解物上清的EAI最高为70.32m2/g。此外,酶解产物上清和沉淀乳化液的ESI增大。与沉淀相比,5种酶解产物的上清具有较低的表观黏度,且酶解产物上清和沉淀的乳化液均呈剪切变稀的非牛顿流体特性。

高压均质处理对甘薯热变性蛋白Alcalase酶解肽乳化特性影响研究

采用高压均质处理甘薯热变性蛋白Alcalase酶解肽(SPHP-Al)的乳化液,以乳化活性指数(EAI)和乳化稳定性指数(ESI)为指标,探讨了不同高压均质条件下(均质压力0.1～80MPa,均质时间0～2min),多肽浓度为0.1%(w/V)与油相体积分数为25%(V/V)形成的SPHP-Al乳化液乳化特性的变化。在所得到最佳的均质条件下,以EAI、ESI、乳化颗粒平均粒径(d4,3)和表观粘度为指标,考察了SPHP-Al浓度(0.1、0.25、0.5、1.0、1.5和2.0%,w/V)和油相体积分数(5、15、25、35和45%,V/V)对SPHP-Al的乳化特性的影响。结果显示,均质压力为50MPa和均质时间为1min时,SPHP-Al乳化效果最佳,SPHP-Al乳化液的EAI和ESI分别比未高压均质的提高了4倍(158.14m2.g-1)和8倍(318.06min);且随着SPHP-Al浓度的增加,乳化液的EAI、d4,3和表观黏度均显著减小,ESI显著增大(p<0.05);与此相反,随着油相体积分数的增大,乳化液的EAI、d4,3和表观黏度均显著增大,ESI显著减小(p<0.05)。因此,高压均质可明显改善SPHP-Al的乳化性,且SPHP-Al浓度与油相体积分数对SPHP-Al乳化性影响显著。上述结果为SPHP-Al在食品行业中的潜在应用提供了数据支撑。

Expression and Thermal Stability Analysis of Peat1 and the 3 Deletion Mutants

[Objective] The research aimed to reveal the functions of NAC and UBA domains in Peatl＇s thermal stability. [Method] Fusion expression vectors of Pearl protein and the 3 deletion mutants were constructed. The recombinant plasmids were induced by IPTG and the target proteins （Peatl, Peatl-△CD99,Peatl-△ND49 and Pearl-△ND108 ）were expressed obtained by AKTA and its thermal stability was analyzed. [Result] The research found that 3 deletion mutants have good thermal stability like Pearl. [Conclusion] The research demonstrated that the coexistence of NAC or UBA domains is not necessary to thermal stability of Pearl protein , and they may give the protein particular stability structure seperately.

Detection of the End Point Temperature of Thermal Denatured Protein in Fish and Chicken Meat Through SDS-PAGE Electrophoresis

Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was applied in the detection of the end point temperature (EPT) of thermal denatured protein in fish and meat in this study. It was also used in studying the thermal denatured temperature range of proteins in salmon and chicken meat. The results show that the temperature ranges of denatured proteins were from 65 ℃ to 75 ℃ , and these temperature ranges were influenced by the processing methods. Through SDS-PAGE, the features of repeated heating thermal denatured proteins under the same temperature and processing time were studied. The electrophoresis patterns of thermal denatured proteins determined through repeated heating at the same temperature did not exhibit any change. For the detection of cooked fish and meat samples, they were subjected to applying the SDS-PAGE method, which revealed an EPT ranging from 60 ℃ to 80 ℃ .

Molecular chaperones and neurodegenerative diseases

Neurodegenerative diseases are characterized by the accumulation of intracellular or extracellular protein aggregates that result from conformational changes in proteins. These diseases may result from an imbalance between the produetion of misfolded proteins and normal chaperone capacity. Molecular chaperones provide a first line of defenee against misfolded, aggragation-prone proteins and are, therefore, promising therapeutic targets for neurodegenerative diseases.

Effect of Acid Treatment on Interfacial and Foam Properties of Soy Proteins

The goal of the present work was to study the effects of acid treatment on the foaming properties of a soybean protein isolate （SPI） and its fractions, glycinin （11S） and β-conglycinin （7S）. The structural characteristics, interfacial properties, foaming capacity and stability of the treated proteins were studied. Results from surface hydrophobicity and differential scanning calorimetry （DSC） showed that the acid treatment caused the complete denaturation of 11S and a partial denaturation of 7S. This protein unfolding affected their interracial properties, which led to an improvement in the foaming properties of both protein fractions and isolate. Treated 7S showed the best behavior in the rearrangement process, probably due to its smaller size and its modified structural characteristics. All treated proteins showed stronger interracial films. The foams of treated proteins were destabilized mostly due to gravitational drainage rather than Ostwald ripening.

薄层等电聚焦电泳法检测动物源食品加热终点温度

使用薄层等电聚焦电泳方法研究鸡肉加热后蛋白热变性的温度范围和同一温度下肉类重复加热后蛋白热变性的薄层等电聚焦电泳特征。实验结果表明,热变性的薄层等电聚焦电泳图谱有渐进式的变化,pI6.05处的条带可能成为理想的检测参考条带,鸡肉热变性完全的温度范围在71～75℃,并且加工方式对电泳图谱有影响。同一温度下肉类重复加热后蛋白热变性的薄层等电聚焦电泳图谱没有变化。确立以同一温度下肉类重复加热后进行薄层等电聚焦电泳来检测肉类是否热变性的方法。