两步水解法制备玉米-大豆复合抗氧化肽及其稳定性研究

采用麦芽粉和碱性蛋白酶Alcalase两步水解玉米醇溶蛋白和大豆分离蛋白的混合物(质量比1∶1)制备复合抗氧化肽,以水解度、可溶性蛋白含量和抗氧化活性为指标,对第二步Alcalase的水解条件进行优化,确定两步水解法制备复合抗氧化肽的最适条件。另外,对复合抗氧化肽相对分子质量分布、稳定性和氨基酸组成进行了研究。结果表明,制备复合抗氧化肽的最适条件为在底物质量分数10%、pH 5.5、50℃、酶(麦芽粉)底质量比30%条件下水解3 h后,再在底物质量分数10%、pH 8.5、60℃、酶(Alcalase)底质量比0.75%条件下继续水解3 h。在最适条件下,水解度、可溶性蛋白含量、羟自由基清除率和亚铁离子螯合率分别为36.32%、36.83 mg/mL、40.01%和86.83%,相对分子质量主要分布在300~6 500 Da (含量92.44%)范围内,必需氨基酸指数(EAAI)值为8.02(n=9),属于优质蛋白源。复合抗氧化肽具有热稳定性,在中性及碱性条件下稳定,但不耐受酸性(pH 3~5)、4℃贮存和反复冻融的加工条件。     

酶法制备汉麻籽蛋白抗氧化肽

采用不同蛋白酶酶解汉麻籽蛋白,确定Alcalase 2.4L碱性蛋白酶是酶解汉麻籽蛋白制备抗氧化肽的优良酶源。通过单因素和响应面回归分析,得到Alcalase 2.4L碱性蛋白酶酶解汉麻籽蛋白的优化条件为:底物浓度50 mg/mL、水解时间2 h、温度50℃、加酶量2.2%、pH 9.4。优化酶解条件下,水解度约为20%,10 mg/ mL酶解产物的DPPH自由基清除率为82.65%,显示出较好的抗氧化活性。     

Alcalase蛋白酶水解花椒籽蛋白制备抗氧化肽的条件优化

本研究以花椒籽蛋白质抗氧化肽水解度(DH)和DPPH自由基清除率为指标,对酶解花椒籽蛋白制备抗氧化肽的水解用酶及其酶用量、底物浓度、酶解温度、时间等酶解条件进行研究,以期优化得到酶解法制备花椒籽抗氧化肽的最优条件。结果表明Alcalase蛋白酶水解花椒籽蛋白制备抗氧化肽效果最好,通过响应面分析法优化出该酶最佳酶解花椒籽制备抗氧化肽的条件为:底物浓度5%,温度55℃,pH 8.5,加酶量4%;该方法可用于花椒籽蛋白制备抗氧化肽,在此条件下花椒籽水解液DPPH自由基清除率可达到61.00%,水解度为12.00%。     

双酶法制备花生抗氧化肽

研究碱性蛋白酶(Alcalase)和风味蛋白酶(Flavourzyme)分步水解花生粕制备花生抗氧化活性肽的工艺条件。结果表明:Alcalase的添加量为0.048AU/g pro,其最佳的底物质量分数为4%,pH值为8.0、酶解时间180min、酶解温度60℃。然后向Alcalase水解液中添加Flavourzyme,添加量为15LAPU/g pro,pH值为7.0、酶解温度50℃、酶解时间180min。在此条件下,花生抗氧化肽得率为90.28%,体系水解度达33.73%,所得花生肽分子质量在5000D以下的为96.92%,具有显著的抗氧化活性。     

Alcalase酶解高底物浓度玉米蛋白工艺优化

以玉米蛋白粉为原料,研究底物浓度、加酶量、水解液pH值和水解温度对酶解产物水解度、可溶性蛋白含量、抗氧化活力和蛋白转换率的影响.首先将玉米蛋白粉顺次进行碱洗、α-淀粉酶去淀粉和高温蒸煮预处理,以破坏蛋白高级结构和去除淀粉,然后以碱性蛋白酶Alcalase为生物催化剂进行玉米蛋白(10％～15％,m∶V)的限制性水解.结果表明,最适酶解条件:底物浓度13.5％(m∶V),加酶量2％,水解温度68℃,反应体系pH值7.7,总水解时间210min.在上述条件下,蛋白水解度为28.81％,水解液的可溶性蛋白含量为31.69mg/mL,水解物抗氧化活性为547.83U/mL,蛋白转化率为36.92％.获得的玉米蛋白水解物的溶解性显著增加,具有良好的抗氧化活性,显示了其在食品和药品等行业应用的潜力和前景.     

大豆蛋白酶解产物抗氧化活性与水解度相关性研究

利用碱性蛋白酶Alcalase 2.4L水解大豆分离蛋白,研究了底物浓度、加酶量、p H、温度因素对酶解液水解度和还原力的影响,并在此基础上用响应面分析法优化酶水解条件。以还原力为主要指标考察酶解产物的抗氧化活性,通过水解度与还原力的比较,得到Alcalase 2.4L碱性蛋白酶酶解大豆分离蛋白产物的抗氧化活性与水解度之间没有直接线性关系。在实验得到的最佳条件下制备的大豆肽抗氧化活性良好,具有良好的应用前景。     

双酶水解玉米醇溶蛋白制备抗氧化肽的工艺优化

为了制备抗氧化活性肽,利用Alcalase碱性蛋白酶和中性蛋白酶分步酶解玉米醇溶蛋白。在单因素的基础上,以1.1-二苯基苦基苯肼(DPPH·)自由基清除率、羟基自由基清除率和水解度(DH)为响应值,采用响应面(RSM)中心组合实验,选取Alcalase碱性蛋白酶加酶量、中性蛋白酶与Alcalase碱性蛋白酶活力之比、底物浓度为自变量,探讨最佳酶解工艺条件。采用Design-Expert软件,通过响应面优化确定修正后各因素的最佳工艺条件为:Alcalase碱性蛋白酶加酶量12880 U/(g底物)、中性蛋白酶与Alcalase碱性蛋白酶活力之比为1∶4,底物浓度为3.4%。在此修正条件下,DPPH·自由基清除率为42.98%,水解度为32.18%,与预测值的相对误差为1.04%。浓度为20 mg/m L时,玉米醇溶蛋白的DPPH·自由基清除率和羟基自由基清除率分别为同浓度VC的85.8%和67.0%。     

鸡骨蛋白肽酶解工艺参数优化研究

为探索鸡骨利用的新途径,以鸡骨渣为原料,开展了鸡骨蛋白肽酶解技术研究。研究了6种酶的酶解效果以及最适蛋白酶的酶用量、底物浓度、温度、pH和酶解时间对鸡骨蛋白水解度和短肽得率的影响,结果表明,Alcalase为最佳用酶,Alcalase水解鸡骨的最佳工艺参数为:酶用量为每克原料0.099 mkat、底物浓度4%、反应温度55℃、pH8.5、反应时间为120 min,在此条件下,鸡骨蛋白水解度为15.9%,短肽得率为61.81%。     

酶法制备家蝇幼虫抗氧化肽条件的优化

以家蝇幼虫为原料,Alcalase碱性蛋白酶为水解酶,采用五因子二次旋转正交组合设计优化水解条件,用清除DPPH·活性的方法测定水解所得家蝇幼虫肽的抗氧化活性.结果表明,制备家蝇幼虫抗氧化肽的最佳酶解条件为:[E]/[S]=3.62%、温度62.17℃、pH 8.20、底物浓度11.71%、时间3.05h.在该水解条件下家蝇幼虫抗氧化肽对DPPH·有很强的清除作用,清除率为86.387%.     

酶解花生蛋白制备功能性多肽条件优化研究

为优化Alcalase 蛋白酶酶解花生蛋白制备功能性多肽的工艺条件,采用响应面分析法,以水解度、短肽得率为响应值,研究温度、pH 值、底物质量分数、酶底比对制备功能性多肽工艺的影响。综合考虑成本和工艺要求等问题,最终确定酶解花生蛋白制备功能性多肽的工艺条件为温度55℃、pH8.4、底物质量分数4.31%、酶底比3.39%、时间4h。该条件下水解度(DH)及三氯乙酸可溶性氮溶解指数(TCA-NSI)分别为23.40% 和74.88%,与理论值的相对误差在0.5% 以内,优化工艺稳定,DH 及TSA-NSI 较高,实验结果与模型预测值相符。     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

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

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Analysis of benzo[a]pyrene in spiked fatty foods by second derivative synchronous spectrofluorimetry after microwave-assisted treatment of samples

A simple, rapid and inexpensive method has been developed for the determination of benzo[a     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. II: Certification study

This paper describes the second part of a project undertaken to develop certified mussel reference materials for paralytic shellfish poisoning toxins. In the first part two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin and decarbamoyl-saxitoxin in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the certification exercise. Fifteen laboratories participated in this certification study and were asked to measure saxitoxin and decarbamoyl-saxitoxin in rehydrated lyophilized mussel material and in a saxitoxin-enriched mussel material. The participants were allowed to use a method of their choice but with an extraction procedure to be strictly followed. The study included extra experiments to verify the detection limits for both saxitoxin and decarbamoyl-saxitoxin. Most participants (13 of 15) were able to meet all the criteria set for the certification study. Results for saxitoxin.2HCl yielded a certified mass fraction of <0.07 mg/kg in the rehydrated lyophilized mussels. Results obtained for decarbamoyl-saxitoxin.2HCl yielded a certified mass fraction of 1.59+/-0.20 mg/kg. The results for saxitoxin.2HCl in enriched blank mussel yielded a certified mass fraction of 0.48 +/- 0.06 mg/kg. These certified reference materials for paralytic shellfish poisoning toxins in lyophilized mussel material are the first available for laboratories to test their method for accuracy and performance.     

Detection of adulteration of locust bean gum with guar gum by capillary electrophoresis and polarized light microscopy

Capillary electrophoresis (CE) and polarized light microscopy (PLM) were utilized in the detection of the adulteration of locust bean gum with guar gum. For CE analyses, standards of locust bean and guar gums were extracted with 30% CH₃CN, removing the residual proteins from the gum matrix. A 8.75 mM NaH₂PO₄-20.6 mM Na₂B₄O₇ buffer, pH 9, was used to separate these proteins and to identify marker proteins that were present in the guar gum. These markers did not co-migrate with components in the extracts of mechanically processed locust bean gum, and are used as indicators of adulteration. Using PLM with toluidine blue and iodine staining techniques, unadulterated locust bean gum samples were distinguished from mixed samples through the differential staining of components in locust bean versus guar and tara gums. These experiments in the use of CE and PLM provide orthogonal and complementary methods for the verification of 'true' positives and the elimination of 'false' positives.     

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     

Chinese CTP Market

According to Printing and Printing Equipment Industries Association of China（PEIAC）＇s statistics to the plate manufucturer in China, in 2013, the actual offset plate production has reached 346 million square meters in China. Among them, the CTP production volume was 245 million square meters, up by 11% than that of last year; the total sales of the CTP plate was 239 million square meters, up by 13%.