谷氨酰胺转氨酶对碱溶酸沉法提取南极磷虾(Euphausia superba)蛋白质得率的影响

通过碱溶酸沉法提取了南极磷虾蛋白质,研究了谷氨酰胺转氨酶的应用对蛋白质得率的影响。结果表明:碱溶酸沉法能够较好地回收南极磷虾蛋白质;在酸沉过程中,合理添加谷氨酰胺转氨酶能够提高蛋白质得率约5%。     

A three-prong strategy to develop functional food using protein isolates recovered from chicken processing by-products with isoelectric solubilization/precipitation

BACKGROUND: Skin‐on bone‐in chicken drumsticks were processed with isoelectric solubilization/precipitation to recover muscle proteins. The drumsticks were used as a model for dark chicken meat processing by‐products. The main objective of this study was conversion of dark chicken meat processing by‐products to restructured functional food product. An attempt was made to develop functional food product that would resemble respective product made from boneless skinless chicken breast meat. A three‐prong strategy to address diet‐driven cardiovascular disease (CVD)with a functional food was used in this study. The strategy included addition of three ingredients with well‐documented cardiovascular benefits: (i) ω‐3 polyunsaturated fatty acid‐rich oil (flaxseed‐algae, 9:1); (ii) soluble fiber; and (iii) salt substitute. Titanium dioxide, potato starch, polyphosphate, and transglutaminase were also added. The batters were formulated and cooked resulting in heat‐set gels. RESULTS: Color (L*a*b*), texture (torsion test, Kramer shear test, and texture profile analysis), thermal denaturation (differential scanning calorimetry), and gelation (dynamic rheology) of chicken drumstick gels and chicken breast gels were determined and compared. Chicken drumstick gels generally had comparable color and texture properties to the gels made from chicken breast meat. The endothermic transition (thermal denaturation) of myosin was more pronounced and gelation properties were better for the drumstick gels. CONCLUSION: This study demonstrated a feasibility to develop functional food made of muscle proteins recovered with isoelectric solubilization/precipitation from low‐value dark chicken meat processing by‐products. The functional food developed in this study was enriched with CVD‐beneficial nutrients and had comparable instrumental quality attributes to respective products made of chicken breast meat. Although the results of this study point towards the potential for a novel, marketable functional food product, sensory tests and storage stability study are recommended. Copyright © 2012 Society of Chemical Industry     

调配型酸乳饮料中最优稳定剂的选择

在制作酸性乳饮料时需添加稳定剂。探讨了稳定剂与酪蛋白的作用机理。选用果胶、CMC、PGA、瓜尔豆胶、黄原胶5种稳定剂,通过离心沉淀率的测定,选取其中稳定效果最优的稳定剂。结果表明：在酸乳饮料体系中,果胶是最优稳定剂。     

Gelation properties of goose liver protein recovered by isoelectric solubilisation/precipitation process

Isoelectric solubilisation/precipitation (ISP) process was applied to goose liver (GL) for protein extraction. The gelation properties of proteins extracted by acid processes (ACP, pH 2.0, 2.5 and 3.0) and alkaline processes (ALP, pH 11.0, 11.5 and 12.0) were estimated, where the unextracted ground GL was set as the control. Nearly 58.39~79.00% of GL proteins were recovered by ISP treatments. High molecular weight (100~250 kDa) proteins were found to be partially hydrolysed by ACP, while few changes in proteins occurred during ALP. As evidenced by rheological and textural measurements, ALP proteins formed gels with high elasticity and superior texture, whereas ACP proteins had inferior gelation properties. Moreover, ALP proteins were able to form a highly interconnected and homogeneous three‐dimensional microstructure. Predominantly, gels produced by 11.0 had optimal texture and the lowest cooking loss (P < 0.05). These results suggested that the ISP process (ALP) is a potential method to improve the economic value of GL.     

两种粗提纯法对纤溶酶纯化效果的比较研究

采用硫酸铵盐析法及乙醇沉淀法对海洋枯草芽孢杆菌纤溶酶的纯化效果进行比较研究,得到的最佳纯化方案为：取一定体积的纤溶酶发酵液进行预处理,再进行分段盐析及分级沉淀,在分段盐析中,30％和70％饱和度的硫酸铵分别用于去除杂蛋白和沉淀纤溶酶,最后进行碱处理及超滤除盐;在分级沉淀中,最佳乙醇沉淀时间为1.5h,去除杂蛋白和沉淀纤溶酶的乙醇体积比分别为25％和165％,最后将两种方法得到的粗提液进行冷冻干燥,硫酸铵法的酶活回收率为83.52％,纯化倍数为1.42,冻干粉得率为4.812 g/L,单位酶活为76 755.82IU/g;乙醇纯沉淀法的酶活回收率为89.7％,纯化倍数为1.72,冻干粉得率为7.611 g/L,单位酶活为137 190.57 IU/g,该结果表明乙醇沉淀法对纤溶酶的粗提效果要优于硫酸铵盐析法.     

卤水-氨水制备超细Mg（OH）_2及超声处理对其影响

超声处理技术作为一种新型高效的材料加工方法,目前已被广泛研究用于纳米/微米材料的制备工艺中。文章以卤水和氨水为原料,采用直接沉淀法制备超细氢氧化镁,并在制备后期加入超声处理。探讨了超声作用对产物晶粒尺寸和粒度分布的影响。利用SEM、XRD等手段表征其结构形貌,通过TG-DTA和物理超声分散法分析了产物的热稳定性和分散性,并分别讨论了温度、反应时间、氨水浓度、反应物浓度、陈化时间等对产物粒径和产率的影响,从而得出制备超细氢氧化镁的最佳工艺条件。实验结果表明,超声处理有利于减小产物的尺寸。在最佳条件下可以得到厚度50 nm左右,晶形完整,纯度高,热分解温度为350℃且分散性好的片状氢氧化镁。     

三步沉淀法纯化鸡卵类黏蛋白

鸡卵类黏蛋白（hen’s egg ovomucoid,HOVM）是鸡蛋清中最重要的过敏原蛋白,探讨三步沉淀（一步三氯乙酸沉淀以及两步硫酸铵盐析沉淀）从鸡蛋清中提取并纯化HOVM的工艺条件,并利用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳以及高效液相色谱（high performance liquid chromatography,HPLC）技术检测纯化效果。结果表明：用等体积去离子水稀释的鸡卵清液加入质量分数10%三氯乙酸去除大部分杂蛋白后,所得上清液加入硫酸铵至终饱和度50%,盐析沉淀进一步去除非HOVM的杂蛋白,上清液中最后再追加硫酸铵至终饱和度80%,离心所得沉淀再经过透析冻干即为高纯度的HOVM;HPLC（检测波长220 nm）检测所获HOVM的纯度为99.202%,此工艺条件下得到HOVM的提取率约为27.05%。     

超声辅助碱法提取对类PSE鸡肉蛋白提取率和功能特性的影响

为提高碱溶酸沉方法提取类PSE（pale, soft and exudative）鸡肉蛋白的提取率,采用超声辅助碱法（超声时间0、5、10、15 min）提取并研究其对类PSE鸡肉蛋白功能特性的影响。结果表明：与对照组相比,超声辅助提取类PSE蛋白的提取率由45.55%显著提高至68.58%（P＜0.05）,蛋白含量显著提高25.32%（P＜0.05）;当超声辅助提取时间为10 min时,类PSE鸡肉蛋白具有较小的浊度、黏度和粒径;扫描电子显微镜结果进一步证实,超声辅助碱法提取的类PSE鸡肉蛋白结构变得更加疏松,碎片尺寸较小;超声处理后,类PSE鸡肉蛋白凝胶的蒸煮损失率显著降低61.77%（P＜0.05）,表明蛋白凝胶的保水性增加,但其凝胶强度显著降低（P＜0.05）;此外,超声辅助提取得到的类PSE鸡肉蛋白溶解度、乳化活性指数和乳化稳定性指数分别提高38.56%、8.02%和12.94%。综上,超声辅助提取不仅可以提高碱溶酸沉法提取类PSE鸡肉蛋白含量,且可以改善类PSE鸡肉蛋白的功能特性。     

麦草乙醇法分解液中木素的分离和结构表征

通过加水、加酸和调节温度的方式回收麦草乙醇法分解液中的粗乙醇木素,并对制得的粗乙醇木素与工业碱木素分别进行FI-IR1、HNMR表征来确定粗乙醇木素的物理化学结构特征,并且进行了成分分析。结果表明,稀释比例为1∶1,pH值为2.5,温度为30℃时,粗乙醇木素的沉淀量最大,木素纯度更高,其物理化学结构特征与工业碱木素有所不同,乙醇木素含有更多的羟基、羰基和甲氧基,有利于改性利用。     

丝绸废水中丝胶提取方法的研究

丝绸废水经过真空浓缩和喷雾干燥制成粗粉末。采用酸析法和低温乙醇沉淀法对粗粉末中的丝胶进行提取,结果表明:低温乙醇沉淀法的提取率较高,采用体积分数为75%的乙醇溶液提取率达到64%。理化性质分析结果表明,低温乙醇沉淀法提取的丝胶蛋白含量高达90%以上,溶解度有所下降,灰分含量降低,蚕腥味被去除。应用圆二色光谱和红外光谱研究2种方法提取的丝胶二级结构分子构象的变化,结果显示提取得到的丝胶蛋白分子构象以无规卷曲为主,β转角构象的比例增加。研究结果表明,低温乙醇沉淀法是一种简便有效提取丝胶的方法。