Protein breakdown during the preparation of frozen batter-coated squid rings

The objective of this paper was to study the main chemical and microstructural changes in squid proteins during processing as a frozen batter-coated product using different coatings. Protein bands of the squid and of the batters used for coating were studied using SDS-PAGE. It is concluded that it is not only the proteins of the layer of batter, which are directly exposed both to the frying oil and to freezing temperatures, that deteriorate during the preparation process, the protein fraction of the squid substrate, mainly the myofibrillar proteins, is also degraded. At a microstructural level, big voids are generated during freezing as a consequence of the packing of the fibres, although the size of these voids decreases after final frying. After this step of the process, the central sarcoplasm is still visible but has been altered by coagulation of the sarcoplasmic proteins and the sarcolemma is observed to be separate from the myofibrillar package.     

脯氨酰内肽酶水解啤酒蛋白的研究

将脯氨酰内肽酶(PEP)添加在啤酒后酵液中,通过冷混浊实验分析脯氨酰内肽酶对啤酒非生物稳定性的影响。结果表明,添加5mg/L的脯氨酰内肽酶就能有效地提高啤酒的非生物稳定性;采用75%硫酸铵沉淀啤酒蛋白,进行SDS-PAGE电泳分析,结果显示,啤酒蛋白电泳图谱的分布主要表现为8～14.4 ku的窄带和35～45 ku的宽带,而经脯氨酰内肽酶处理的啤酒蛋白电泳图谱中8～14.4 ku的条带消失,说明此蛋白被脯氨酰内肽酶水解。     

改性乳清蛋白体外抗氧化特性

以木糖、葡萄糖、果糖、乳糖、麦芽糖、蔗糖和乳清蛋白为美拉德反应原料,按照一定比例进行湿热糖基化反应。结果表明:在湿热糖基化反应后,6种糖类与乳清蛋白复合物在420 nm和294 nm处的吸光值差异显著(P<0.05);除乳清蛋白-蔗糖复合物外,其他5种乳清蛋白糖基复合物的游离氨基酸含量均显著降低(P<0.05)。除了乳清蛋白-蔗糖复合物外,其他5种乳清蛋白糖基化复合物随浓度的增加,还原能力和DPPH自由基清除能力都有所提高,其中乳清蛋白-木糖复合物的抗氧化能力提高最大,而且SDS-PAGE显示乳清蛋白-木糖复合物反应后分子质量明显增大;傅里叶红外光谱(FTIR)结果显示,乳清蛋白-木糖和乳清蛋白-葡萄糖复合物中蛋白质的酰胺I和II明显减少。     

利用蛋白质SDS-PAGE电泳方法检测转基因大豆的初步研究

为建立利用蛋白质检测转基因大豆的较稳定的新方法,采用SDS-PAGE蛋白质电泳方法时转基因大豆和非转基因大豆进行检测,初步研究发现转基因大豆中大约45 ku蛋白带的表达量明显强于非转基因大豆中相对应的蛋白带,通过固定转基因大豆的上样量,逐渐增加非转基因大豆的上样量进一步验证了结果.以国内不同品种的非转基因大豆进行SDS-PAGE蛋白电泳检测,初步排除了结果偶然性的产生.     

高压处理大米蛋白酶解过程中糖-蛋白结合特性的变化

研究了热变性大米蛋白经100MPa高压处理的酶解过程中蛋白质与糖结合特性的变化,并与未高压处理的酶解物进行了比较.凝胶色谱分析显示,经高压处理的大米蛋白可溶性酶解物中蛋白/糖含量比值低于常压处理者.β-消去反应证明了蛋白和糖的连接方式为N-糖肽键结合.FT-IR分析表明,高压和常压处理后大米蛋白的酶解残余物中均含有糖组分,且高压处理者的糖相对含量较低.SDS-PAGE和PAS-Schiff试剂染色显示,高压和未高压处理者的酶解残余物中14ku均是糖蛋白.上述结果表明,高压处理有利于糖蛋白的酶解,但部分糖蛋白仍呈不溶解状态.     

燕麦蛋白组分分离提取及其SDS-PAGE电泳分析

通过单因素实验对燕麦蛋白组分的分离提取工艺进行了优化,并通过SDS-PAGE电泳对燕麦蛋白组分进行亚基分析。结果表明:燕麦清蛋白提取的最佳温度为40℃,球蛋白提取最佳盐浓度为7%,醇溶蛋白提取的最佳乙醇浓度为75%,谷蛋白提取的最佳碱浓度为0.05 mol/L,蛋白质提取率为83.1%。SDS-PAGE实验结果显示:燕麦清蛋白在10~100 kD范围内均有分布,燕麦球蛋白由2个亚基组成,分子量分别在97.4~100 kD和43~66.2 kD范围内,燕麦醇溶蛋白亚基大部分集中在18.39~40.72kD之间,燕麦谷蛋白部分亚基分布在20.67~26.66kD与43.29~50.80 kD之间。     

高静水压处理对牛初乳中IgG的影响

采取不同的高静水压条件（处理压强、施压温度、保压时间）处理产犊后48 h内的牛初乳,研究高静水压处理牛初乳对免疫球蛋白G（immunoglobulin G,IgG）活性的影响。将牛初乳离心去除酪蛋白、乳脂肪等,取上清液进行高静水压处理,采用高效液相色谱法和十二烷基硫酸钠-聚丙烯酰胺凝胶电泳法（sodium dodecyl sulfatepolyacrylamidegel electrophoresis,SDS-PAGE）对处理后的样品进行检测。结果表明：高静水压处理后的样品,经高效液相色谱仪检测,其与亲和色谱柱发生特异性吸附的能力下降,IgG检出质量浓度降低;经SDS-PAGE检测和凝胶电泳成像仪扫描处理,不同处理条件下IgG的轻链和重链的质量变化不显著。因此,当牛初乳在200 MPa、30 ℃和20 min的高静水压处理条件下,IgG的活性最好,检出质量浓度为16.843 9 mg/mL。     

The applicability of using a protease extracted from cashew fruits (Anacardium occidentale), as possible meat tenderizer: An experimental design approach

Meat tenderness is one of the most important organoleptic properties in determining consumer acceptance in meat product marketability. Therefore, an effective meat tenderization method is sought after by exploring plant-derived proteolytic enzymes as meat tenderizer. In this study, a novel protease from Cashew was identified as a new alternative halal meat tenderizer. The extraction of cashew protease was optimized using response surface methodology (R² = 0.9803) by varying pH, CaCl₂ concentration, mixing time, and mass. pH 6.34, 7.92 mM CaCl₂ concentration, 5.51 min mixing time, and 19.24 g sample mass were the optimal extraction conditions. There was no significant difference (n = 3; p < 0.05) between the calculated (6.302 units/ml) and experimental (6.493 ± 0.229 units/ml) protease activity. The ascending order of the effects was pH < mixing time < CaCl₂ < sample mass. In meat tenderizing application, the meat samples treated with 9% (v/w) crude protease extract obtained the lowest shear force (1.38 ± 0.25 N) to cause deformation on the meat. An electrophoretic analysis showed that protein bands above ~49.8 kDa were completely degraded into protein bands below ~22.4 kDa. Scanning electron microscopy shows the disruption of the muscle fibers after being treated by the Cashew protease. The results of this study show the Cashew (Anacardium occidentale) crude extract can be used as an alternative of the animal and microbial protease as meat tenderizer and subsequently overcome the shortcoming of the halal industrial protease.     

Studies on the proteins of kodo millet (Paspalum scrobiculatum)

Studies on the proteins of five varieties of kodo millet showed that there are hardly any varietal differences. Fractionation of the proteins showed that glutelin is the major storage protein. The amino acid compositions of the protein of the five varities of kodo millet and the individual protein fractions of two varieties were determined. Lysine is the most limiting amino acid followed by methionine and cystine. There is no significant negative correlation between lysine levels and protein content. Sodium dodecylsulphate polyacrylamide gel electrophoresis patterns indicate great similarities in the different varieties.     

鲍鱼腹足肌原纤维蛋白的组成及其性质

采用SDS-PAGE分析了鲍鱼腹足肌原纤维蛋白的组成,并考察了温度、pH和离子强度对鲍鱼腹足肌原纤维蛋白溶液浊度和溶解度的影响。结果表明,鲍鱼腹足肌原纤维蛋白主要含有肌球蛋白、肌动蛋白、副肌球蛋白和原肌球蛋白。随着加热温度的升高,鲍鱼腹足肌原纤维蛋白的浊度上升、溶解度降低,且温度在40~50℃时浊度和溶解度变化明显;pH在5.5~6.0时,蛋白的浊度急剧下降而溶解度急剧升高;随着离子强度的增加蛋白的浊度下降、溶解度升高,离子强度在0.2~0.4 mol/L时浊度和溶解度变化明显。