酶法糖基化修饰对玉米醇溶蛋白部分结构及流变学性质的影响

为了提高玉米醇溶蛋白的生物利用率,用谷氨酰胺转氨酶(TGase)和低聚氨基葡萄糖对玉米醇溶蛋白进行酶法糖基化修饰,研究了TGase催化的低聚氨基葡萄糖的共价结合反应对玉米醇溶蛋白部分结构性质及流变学性质的影响。试验结果表明,与玉米醇溶蛋白相比,低聚氨基葡萄糖的共价结合使玉米醇溶蛋白的游离巯基含量降低32.37μmoL/g,热变性温度和变性焓分别增加11℃和72.3J/g,即糖基化反应使玉米醇溶蛋白的热稳定性增加。在剪切速率为1～100s~(-1)条件下,糖基化玉米醇溶蛋白分散液的表观黏度最高,并表现出剪切稀化的特性。在剪切频率0.1～10 Hz时,交联玉米醇溶蛋白和糖基化玉米醇溶蛋白分散液的弹性模量(G′)均大于黏性模量(G″),表现为类固体特征。     

D-氨基半乳糖修饰对玉米醇溶蛋白结构性质及生物活性的影响

以含有伯胺基团的D-氨基半乳糖为酰基受体,通过谷氨酰胺转氨酶(TGase)催化的糖基化反应修饰玉米醇溶蛋白,分析了糖基化修饰对玉米醇溶蛋白结构性质及生物活性的影响。红外光谱的测定结果表明,在TGase的催化下,玉米醇溶蛋白与D-氨基半乳糖发生了共价结合。在D-氨基半乳糖不存在的反应体系,TGase催化的玉米醇溶蛋白分子间的交联反应发生的概率低,对玉米醇溶蛋白结构性质的影响较小。与玉米醇溶蛋白相比,D-氨基半乳糖的共价结合使玉米醇溶蛋白的游离巯基含量降低67. 45μmol/g,变性温度和总变性焓分别增加8. 8℃和31. 97 J/g,即糖基化增加了玉米醇溶蛋白的热稳定性。糖基化修饰使玉米醇溶蛋白的抗氧化活性(包括DPPH自由基、超氧阴离子自由基和羟自由基清除活性和还原力)和乙醇脱氢酶激活率均显著提高,为进一步研究糖基化玉米醇溶蛋白的护肝活性奠定了理论基础。     

酶法糖基化修饰对玉米醇溶蛋白物化性质的影响

以D-氨基半乳糖为酰基受体,转谷氨酰胺酶为催化剂,对玉米醇溶蛋白进行酶法糖基化改性,分析了D-氨基半乳糖的共价结合对玉米醇溶蛋白物化性质的影响。实验结果表明:与玉米醇溶蛋白相比,糖基化玉米醇溶蛋白的乳化活性/乳化稳定性、起泡性/泡沫稳定性和体外消化能力均增加,而持水性和吸油性下降。在剪切速率为(1~100)s—1条件下,糖基化玉米醇溶蛋白分散液的表观黏度最高,并且表现出剪切稀化特性;在频率为(0.1~10)Hz条件下,交联玉米醇溶蛋白和糖基化玉米醇溶蛋白分散液的弹性模量均大于黏性模量,表现为类固体特征。     

白酒糟醇溶蛋白的磷酸化改性及功能性质

酒糟是酿酒产业的最大副产物。酒糟富含醇溶蛋白,然而由于水溶性差,限制其进一步应用。采用醇碱法从清香型白酒糟中提取醇溶蛋白(prolamin from distiller’s grains, PDG),用三聚磷酸钠对PDG进行磷酸化改性,通过溶解度、持水性、持油性、乳化性等方面的分析,研究磷酸化改性对PDG功能性质的影响。结果表明,醇碱法提取的白酒糟PDG主要由4种不同分子质量的蛋白组成,原材料酒糟粉粉碎度影响PDG的提取率,粒度小时有利于提高蛋白提取率,以200目细粉为原料时PDG的提取率可达22.69%±0.26%。差示扫描量热实验结果显示PDG的热变性温度为123.47℃,PDG具有良好的热稳定性。傅里叶红外光谱结果表明与三聚磷酸钠反应后磷酸基团修饰到PDG上。磷酸化改性改善了PDG在水中的溶解度,30℃时磷酸化后PDG的溶解度较PDG提高了3.53倍,达到943.08±16.04μg/mL。由于引入磷酸基团,PDG的功能性质显著改善,磷酸化改性后PDG较PDG的持水性和持油性分别增加了44.9%和33.8%(30℃),乳化性及乳化稳定性分别提高了54.9%和3.6倍(pH10)。...     

壳寡糖酶法糖基化修饰对玉米醇溶蛋白功能性质的影响

为了提高玉米醇溶蛋白的生物利用率,以微生物转谷氨酰胺酶为催化剂,壳寡糖(分子质量为1 500 Da)作为酰基受体,通过糖基化反应修饰玉米醇溶蛋白,分析糖基化修饰对玉米醇溶蛋白物化性质和抗氧化活性的影响。红外光谱和游离氨基含量的测定结果表明,在转谷氨酰胺酶的催化下,玉米醇溶蛋白与壳寡糖发生了共价结合。与玉米醇溶蛋白和交联玉米醇溶蛋白相比,糖基化玉米醇溶蛋白的表面疏水性显著降低,表明其水溶性显著改善;糖基化玉米醇溶蛋白的抗氧化活性(包括1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基、超氧阴离子自由基和羟自由基清除活性,还原力和亚铁离子螯合能力)显著提高,尤其是DPPH自由基清除活性,其EC50值为0.945 mg/m L;糖基化玉米醇溶蛋白的持水性、吸油性、乳化性和Zeta电位的绝对值均显著降低。实验结果可为糖基化玉米醇溶蛋白在食品工业的应用提供参考。     

磷酸化修饰改善玉米醇溶蛋白溶解度

玉米醇溶蛋白不溶于水,限制了其作为营养物质在食品工业中的应用,因此,提高其溶解度十分必要。本实验中采用磷酸化修饰蛋白的方法,探究了三聚磷酸钠用量、反应时间、反应温度、反应pH四个因素对提高磷酸化玉米醇溶蛋白溶解度的影响,优化出玉米醇溶蛋白磷酸化的最佳工艺条件为:三聚磷酸钠用量25%,pH9.0,反应温度30℃,反应时间2.5h,此工艺条件下,磷酸化玉米醇溶蛋白的溶解度达15.4%。     

葡萄糖糖基化改性玉米醇溶蛋白膜的物化性质 及在胶囊壳中的应用

以葡萄糖为原料对玉米醇溶蛋白进行糖基化改性,以抗拉强度为指标,考察最佳改性成膜工艺,并通过差示扫描量热法(DSC)、傅里叶变换红外光谱(FT-IR)、扫描电子显微镜(SEM)对改性蛋白膜的物化性质进行研究。结果表明:在葡萄糖与玉米醇溶蛋白质量比1∶10、超声功率450 W、反应时间30 min的条件下,制得玉米醇溶蛋白-葡萄糖膜的抗拉强度达到34.06 MPa,接枝度为63.05%。玉米醇溶蛋白以共价键的方式与葡萄糖结合,使糖基化改性产物结构更加稳定。改性蛋白膜的表面较改性前更加平整,凹陷凸起基本消失。玉米醇溶蛋白-葡萄糖膜热变性温度从改性前的157.95℃升高到164.26℃,膜的热稳定性提高。经葡萄糖糖基化改性后的玉米醇溶蛋白胶囊壳指标符合《中华人民共和国药典》(2015版)要求。     

湿法糖基化改性玉米醇溶蛋白的物化特性及其在胶囊壳中的应用

利用麦芽糖浆对玉米醇溶蛋白进行湿法糖基化改性,以抗张强度为指标,考察改性后蛋白膜的机械性能,通过SDS-PAGE、DSC、傅里叶红外和扫描电子显微镜等手段考察蛋白改性前后的物化性质。结果表明:改性后蛋白膜较传统的明胶膜和纯玉米醇溶蛋白膜机械性能有较大提高。对SDS-PAGE电泳谱图分析可知玉米醇溶蛋白与麦芽糖浆进行了有效的糖基化接合。经傅里叶红外光谱扫描,可知改性后的玉米醇溶蛋白的化学结构发生了变化。差示量热扫描仪分析表明湿法改性的产物zein-MS膜热变性温度从由为改性前的188. 47℃提高到了206. 87℃,增加了膜的稳定性。扫描电子显微镜发现改性后膜的表面较改性前更加平整,孔洞基本消失。将玉米醇溶蛋白改性产物制成胶囊壳,以常规明胶胶囊壳作对照,参考《中华药典》(2015版)的相关检测指标进行检测,各项指标均合格。     

萝卜籽蛋白提取及其功能性质研究

以萝卜籽为原料,用正己烷脱脂得萝卜籽粕,采用碱溶酸沉法对萝卜籽粕中的蛋白质进行提取,并测定其等电点。通过考察料液比、碱溶p H、浸提时间和浸提温度对萝卜籽蛋白提取率的影响,确定最佳的萝卜籽蛋白提取条件,并对所提取的萝卜籽蛋白和大豆分离蛋白进行功能性质的对比。结果表明:萝卜籽蛋白溶解度为84.9%,有很高的营养价值;在料液比1∶20、碱溶p H 9.0、浸提时间120 min、浸提温度50℃的条件下,萝卜籽蛋白提取率为52.3%;萝卜籽蛋白等电点有两个,分别为p H 0.5和p H 4.5;萝卜籽蛋白吸油能力为328.67%,乳化性及乳化稳定性与大豆分离蛋白相近,起泡性及泡沫稳定性较大豆分离蛋白好。     

磷酸化改性玉米蛋白的性质

采用三氯氧磷(POCl3)为磷酸化试剂,制备玉米磷酸化改性蛋白并测定了其功能性质。与原玉米蛋白相比,磷酸化改性蛋白的溶解度、乳化能力和乳化稳定性、发泡性和发泡稳定性、持水性等功能性质均得到了提高;红外光谱分析表明,蛋白质肽链上引进磷酸根基团。     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPL C with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether)analysed in the same products in the context of a previous study.     

Review of techniques to manufacture micro-hydrogel particles for the food industry and their applications

Microgels are ‘soft’ microscopic cross-linked polymeric particles that are being increasingly exploited in a variety of industries for rheology control, encapsulation and targeted delivery. They are valued because of the ability to tune their functionality to address specific applications in oil recovery, coatings, drug delivery, cosmetics, personal care and foods. Food microgels are typically biopolymer hydrogels in the form of microspheres, nanospheres (also called nanogels), spheroids and fibres. The utilisation of engineered microgels in foods has so far been limited, despite their great potential to address several needs in the food industry, including: satiety control, encapsulation of phytonutrients and prebiotics, texture control for healthier food formulations (e.g. reduced fat products), and targeting delivery to specific areas in the digestive tract. We review the scientific and patent literature on the utilisation and manufacturing methods for producing microgels with an emphasis on micro-hydrogels for food applications.     

12—A CRITIQUE OF SOME HYPOTHESES RELATING TO THE HETEROGENEITY OF THE HIGH-SULPHUR PROTEINS OF WOOL

Joubert and Burns prepared a large number of fractions from the high-sulphur proteins of wool and estimated their molecular weights and amino-acid compositions. Their data have been re-examined in order to look for statistically significant interrelations between amino acids and between the proportion of various amino acids and molecular weight. Statistical analysis of the data is also used to examine the credibility of some hypotheses concerning the mechanism of keratin biosynthesis and to provide further evidence for the existence of families of proteins within the high-sulphur fractions of wool.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.     

Announcing a new international peer-reviewed journal:Food Science and Human Wellness now accepting manuscript submission in English

<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of     

The Latest Data about Development of Chinese Printing Industry in 2013

In the 2014 China（Shanghai）International Printing Week,Director Wang Yanbin released the latest data about development of Chinese printing industry in 2013.According to statistics,in 2013,the total output value of Chinese printing industry exceeded 1trillion Yuan for the first time,reaching 1.03985 trillion Yuan.There were 105,000 printing enterprises in China,employees were 3.415 million.The total asset was 1.06247 trillion Yuan;     

The State Council Issued "Directory of Government Approved Investment Projects(2013 Edition)"

正On December 2nd,2013,the State Council issued the notification of"Directory of Government Approved Investment Projects(2013 Edition)"(hereafter referred to as"notification").It is pointed out in the"notification"that in order to further deepen reforms in investment systems and administrative examination and approval systems,simplify administrative procedures and delegate powers to lower levels,earnestly     

China textile machinery: taking off in progress

正Among the 1600 exhibitors who take apart in the ITMA ASIA+CITME2014 2/3 are Chinese manufactures.If the numerous figures failed to attract your attention,the increase of quality should draw your focus.To adopt the demand of developing textile machine market,domestic textile machinery enterprises now follow the slogan of"technology drives development"to enhance product competitiveness.Our domestic sellers will showcase product ranging from spinning,weaving,dyeing and printing,     

Top Ten News of China's Paper Industry 2013

On December 24th, 2013, the meeting on the selection of top 10 news of China＇s paper industry 2013 sponsored by 〈China Paper Newsletters〉 was held in Beijing. The yearly selection of the top l0 news, which began in 2000, has become a brand activity widely recognized in the industry thanks to the support from the authorities at all levels and public participation.