不同蛋白酶对脱脂豆粉酶解条件的研究

以水解蛋白得率和蛋白质水解度为评价指标,研究了内切蛋白酶和外切蛋白酶酶解脱脂豆粉的适宜条件.结果表明:内切蛋白酶最适酶解条件为pH7.5,温度60℃,酶解时间6h,酶用量1.5%,水与脱脂可粉的比为7:1;外切蛋白酶最适酶解条件为pH5.5,温度55℃,酶解时间9h,酶用量1.5%,水与脱脂豆粉的比为7:1.在最适酶解条件下,内切蛋白酶酶解脱脂豆粉的水解蛋白得率达到50.6%,外切蛋白酶酶解脱脂豆粉的蛋白水解度为26.7%.     

蛋壳膜硫酸软骨素的提取工艺及其优化

以蛋壳膜为原料,采用稀碱与酶解相结合的方法提取硫酸软骨素。以胰蛋白酶、胃蛋白酶分解去除杂蛋白,经酒精沉淀并干燥后得到产品。实验得到的最佳提取工艺为:料液比1:1.5,碱浓度5%,碱提温度40℃,胰蛋白酶、胃蛋白酶的用量分别为1.5%、0.8%,pH值分别为8.2和5.5,酶的各自最适条件作用时间均为2.0h。     

骨肉酶解工艺条件研究

为了进行猪骨肉的综合利用,本实验以猪骨为原料,研究木瓜蛋白酶、中性蛋白酶和胰蛋白酶的水解效果以及最适蛋白酶的酶解温度、pH、酶用量、料液比和酶解时间对骨肉蛋白水解度和总氮回收率的影响。结果表明：胰蛋白酶为最佳骨肉水解酶,胰蛋白酶水解猪骨的最佳工艺参数为：酶解时间为5h、酶解温度60℃、pH8、酶用量5000U／g原料、料液比为1：5。     

蛋壳膜中透明质酸的提取及部分特性研究

分别采用胰蛋白酶和胃蛋白酶降解蛋壳膜,从中提取透明质酸.通过正交实验考察酶解温度、pH、酶用量、料液比和酶解时间对透明质酸提取量的影响,确定采用胰蛋白酶酶解的最佳条件为:温度为50℃,时间为7h,料液比为1:40.酶用量为8000U/g,pH为8.5,提取率为13.294mg/g;采用胃蛋白酶酶解的最佳条件为:温度为37℃,时间为5h,料液比为1:40,酶用量为11000U/g,pH为3.0,提取率为24.494mg/g.结果表明,胃蛋白酶提取透明质酸的效果好于胰蛋白酶,且壳膜中含有重要数量的透明质酸.通过红外光谱分析和测定葡萄糖醛酸、氨基葡萄糖的含量,对提取的透明质酸进行分析鉴定.     

脱脂蛋黄蛋白粉酶水解实验研究

蛋黄蛋白粉是提取药用卵磷脂生产的副产物,用酶解方法将蛋黄蛋白转化为氨基酸或寡肽是回收利用脱脂蛋黄蛋白粉的重要途径之一.从研究水解反应入手,通过单因素试验和正交优化试验研究胃蛋白酶的最佳水解条件,考察了底物浓度、水解时间、反应温度、pH、酶浓度对脱脂蛋黄蛋白粉水解度的影响,然后根据正交试验结果对胃蛋白酶胰蛋白酶组合水解进行研究.研究结果表明,胃蛋白酶水解的最佳工艺条件是:温度为38 ℃,pH为2.0,底物浓度为5％,酶浓度为2％,水解时间为4h,此条件下水解度为15.76％.胃蛋白酶-胰蛋白酶组合酶水解的最佳工艺条件是:先加胃蛋白酶水解4h,而后调节pH为7.5,温度55℃,再加入浓度为0.5％的胰蛋白酶水解4h,此时水解度高达20.41％,明显高于胃蛋白酶单酶水解.     

响应面法优化鹿骨多肽酶解工艺及其体外抗氧化活性

目的:筛选鹿骨蛋白最适提取温度和最佳酶解工艺并检测其抗氧化活性。方法:根据鹿骨蛋白的蛋白浓度筛选出最适提取温度,根据水解度（DH）通过单因素及响应面实验设计筛选鹿骨多肽的最佳酶解工艺,并通过测定鹿骨多肽对DPPH自由基、羟自由基的清除能力来评价鹿骨多肽的抗氧化活性。结果:最佳提取温度为95 ℃,通过响应面法优化及实际验证确定了胃蛋白酶和胰蛋白酶最佳酶解工艺分别为胃蛋白酶酶用量6200 U/g,温度37.3 ℃,pH2.0,时间3.2 h,此时的水解度为11.23%;胰蛋白酶酶用量6300 U/g,温度37.2 ℃,pH8.1,时间4.0 h,此时的水解度为23.09%。鹿骨多肽对DPPH自由基、羟自由基具有清除能力,其IC₅₀值分别为:3.72、2.24 mg/mL。结论:本实验得到了鹿骨蛋白最佳提取温度并确定鹿骨多肽最佳酶解工艺,且鹿骨多肽对DPPH自由基、羟自由基具有良好的清除能力,说明鹿骨多肽具有良好的抗氧化活性。     

响应面优化超声波辅助水酶法提取花生蛋白工艺

采用水酶法结合超声波预处理提取花生蛋白,在单因素实验基础上,选出最优的超声时间和超声温度,重点以酶用量、酶解pH、酶解温度、酶解时间和料液比为考察的影响因子,花生蛋白提取率为响应值。确定最优复合酶水解的水酶法提取花生蛋白工艺条件为：加酶量为1.59%,温度为56.5℃,酶解时间为3.9h,料水比为1∶4.4,pH为9.0,此时蛋白提取率为94.31%±0.37%。     

酶改性蛋白制备水溶性蜂王浆的研究

以胃蛋白酶和碱性蛋白酶为实验用酶,对蜂王浆蛋白的最佳水解条件及两种酶解液的特性进行了研究.结果表明:胃蛋白酶的最佳水解条件为pH=2,温度为37.C,料液比为1:3,酶浓度7‰,反应时间为8h;碱性蛋白酶的最佳水解条件为pH=8,温度为50%,料液比为1:4,酶浓度7‰,反应时间为8h.碱性蛋白酶其酶解产物的澄清度、苦味值及氮溶解指数均优于胃蛋白酶酶解产物,可用于制备水溶性蜂王浆.     

鹿角盘成分提取及其工艺的优化

摸索鹿角盘提取条件,优化提取工艺。利用正交试验考察水提法和酶解法对鹿角盘提取率的影响。水提法:料液比1︰25 (g/mL), 100℃煎煮6 h,提取率为28.11%。单酶酶解法:胃蛋白酶酶解工艺为料液比1︰30 (g/mL),pH 1.8,加酶量4%,酶解温度37℃,酶解4 h,提取率为22.39%;胰蛋白酶酶解工艺为料液比1︰20 (g/mL), pH 8.0,加酶量4%,酶解温度55℃,酶解6 h,提取率为20.99%。复合酶解酶解工艺:先胃蛋白酶,处理条件为料液比1︰20 (g/mL),pH 1.8,加酶量1%,酶解温度37℃,酶解12 h;后胰蛋白酶,处理条件为料液比1︰20 (g/mL), pH 8.0,加酶量0.4%,酶解温度37℃,酶解2 h,提取率可达31.84%。按照复合酶解工艺,对水提法最佳条件下提取后的鹿角霜进行复合酶解,提取率仅为1.33%。利用水提和酶解的方法筛选出鹿角盘的最优提取条件,制备工艺合理。由结果看出,两个方法中得到的提取率差异不明显。复合酶解得到的提取物种类和含量多于水提法的种类和含量。     

猪血红蛋白酶解制备ACE抑制肽的研究

本实验选用碱性蛋白酶、胰蛋白酶、胃蛋白酶、风味蛋白酶、中性蛋白酶和木瓜蛋白酶等六种商业蛋白酶在各自最适反应条件下分别水解猪血红蛋白12h,研究其水解产物对血管紧张素转换酶抑制率和蛋白水解度的影响。结果显示:采用胃蛋白酶酶解获得的产物ACE抑制率最高。胃蛋白酶的酶解条件为底物5%(质量分数),酶与底物浓度比E:S=3%,温度37℃,pH2.0,水解4h后其ACE抑制率为81.10%,水解度为6.64%。     

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.     

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.     

低温带皮菜籽粕微粉的不同粒级部分的功能特性

为研究低温带皮菜籽粕微粉的不同粒级部分的功能特性,以经低温脱脂的带皮菜籽粕为原料,经微粉碎后筛分成212~425μm、150~212μm和106~150μm的3个不同粒级的微粉样品,检测这些样品的吸水性、吸油性、乳化性和乳化稳定性、蛋白质体外消化率。结果表明:1 3个不同粒级的微粉样品之间的粗纤维含量存在显著差异,表明三者的结构组成成分有一定差异。23个微粉样品的乳化活性和乳化稳定性随粒度级别的减小而显著增加(P0.01)。33个微粉样品的蛋白质体外消化率随粒度级别的减小而显著增加(P0.01)。4不同粒级带皮菜籽粕微粉样品的吸水性与吸油性受其结构组成物质不同和粒度的双重影响,与粒度的相关性不明显。     

Microbiology of food taints

Fresh and processed foods are often spoilt by the presence of undesirable flavours and odours caused by microbial action. The aim of this paper is to review the current knowledge of microbiologically induced taints that occur in a wide range of foodstuffs, including meats, poultry, fish, crustaceans, milk, dairy products, fruits, vegetables, cereals and cereal products. Examples have been chosen where the compounds responsible for the taint have been identified and sufficient data obtained to demonstrate the involvement of microorganisms. However, in some cases the full identity of the causative organism may not have been elucidated. The types of microorganisms covered by this review include bacteria, fungi, yeasts, actinomycetes and cyanobacteria. Although cyanobacteria do not in general infect foods, their presence in aqueous systems and water supplies can lead to off-flavours in aquatic organisms and processed foodstuffs. Several examples of each of these processes are discussed. Wherever possible, the likely biosynthetic pathway used by the microorganism to produce the offending compound in a foodstuff is indicated.     

Analysis for organic residues from aids to polymerization used to make plastics intended for food contact

Polymers intended for food contact use have been analysed for organic residues which could be attributed to a range of substances employed as polymerization aids (e.g. initiators and catalysts). A wide range of polymers was extracted with solvents and the extracts analysed by gas chromatography-mass spectrometry (GC-MS). The overwhelming majority of substances identified were not derived from aids to polymerization but were oligomers, additives and adventitious contaminants. However, a small number of substances were identified as initiator residues. These included tetramethylsuccinonitrile (TMSN) which was observed in two polymers and it derived from recombination of two azobisisobutyronitrile (AIBN) initiator radicals. Methyl benzoate, benzoic acid, biphenyl and phenyl benzoate were detected in one poly(methyl methacrylate) sample and in two polyvinylchlorides and they are thought to be derived from benzoyl peroxide initiator. TMSN was subsequently targeted for analysis of poly-(methyl methacrylate) plastics using proton nuclear magnetic resonance spectrometry (¹     

Tests of potential functional barriers for laminated multilayer food packages. Part II: Medium molecular weight permeants

Experiments were performed to characterize the kinetics of the permeation of different medium molecular weight model permeants: bisphenol A, warfarin and anthracene, from liquid paraffin, through a surrogate potential functional barrier (25 microns-thick orientated polypropylene--OPP) into the food simulants olive oil and 3% (w/v) acetic acid. The characterization of permeation kinetics generally observed the permeation models previously reported to explain the experimental permeation results obtained for a low molecular weight group of model permeants. In general, the model permeants exhibited behaviour consistent with their relative molecular weights with respect to (a) the time taken to attain steady-state permeation into the food simulant in which they were more soluble, (b) their subsequent steady-state permeation rates, and (c) their partition between liquid paraffin and the OPP membrane.     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. I: Interlaboratory studies of methods of analysis

This paper describes the first part of a project undertaken to develop mussel reference materials for Paralytic Shellfish Poisoning (PSP) toxins. Two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin (STX) and decarbamoyl-saxitoxin (dc-STX) in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the second part of the project: the certification exercise. In the first study, 18 laboratories were asked to measure STX and dc-STX in rehydrated lyophilized mussel material and to identify as many other PSP toxins as possible with a method of their choice. In the second interlaboratory study, 15 laboratories were additionally asked to determine quantitatively STX and dc-STX in rehydrated lyophilized mussel and in a saxitoxin-enriched mussel material. The first study revealed that three out of four postcolumn derivatization methods and one pre-column derivatization method sufficed in principle to determine STX and dc-STX. Most participants (13 of 18) obtained acceptable calibration curves and recoveries. Saxitoxin was hardly detected in the rehydrated lyophilized mussels and results obtained for dc-STX yielded a CV of 58% at a mass fraction of 1.86 mg/kg. Most participants (14 out of 18) identified gonyautoxin-5 (GTX-5) in a hydrolysed extract provided. The first study led to provisional criteria for linearity, recovery and separation. The second study revealed that 6 out of 15 laboratories were able to meet these criteria. Results obtained for dc-STX yielded a CV of 19% at a mass fraction of 3.49mg/kg. Results obtained for STX in the saxitoxin-enriched material yielded a CV of 19% at a mass fraction of 0.34mg/kg. Saxitoxin could not be detected in the PSP-positive material. Hydrolysis was useful to confirm the identity of GTX5 and provided indicative information about C1 and C2 toxins in the PSP-positive material. The methods used in the second interlaboratory study showed sufficiently consistent analysis results to undertake a certification exercise to assign certified values for STX and dc-STX in lyophilized mussel.     

Focus on China's Paper Industry

In the English section of this issue, 〈China Paper Newsletters〉 will introduce ＂National Development and Reform Commission Issued Announcement for Selection of Major Preliminary Research Projects for the ＇13th Five-Year Plan＇＂, ＂2013 Annual Report of China＇s Paper Industry＂, and news of projects and other policies.     

Listen to downstream & search for innovation

正Nowadays,textile enterprises are all taking efforts in transformation and upgrading,like improving producing capacity and optimizing production structure to face market downturn.It claimed a higher request to the standard of textile equipments.In the upcoming of ITMA ASIA+CITME 2014exhibition,this magazine have interviewed several branch associations and a series of relative enterprises,to summarize industrial developing status