琥珀酰化改性对米渣分离蛋白乳化性的影响

研究对米渣分离蛋白进行琥珀酰化改性以提高其功能特性,拓展其在食品中的应用范围。在单因素试验的基础上,通过响应面法优化琥珀酰化米渣分离蛋白的改性条件,得到乳化性较好的产物。结果表明:琥珀酸酐添加量、反应温度、pH对酰化反应均有显著影响。琥珀酰化改性的最佳条件为反应温度36.24℃,反应pH 8.57及琥珀酸酐添加量5.39%,在此条件下,琥珀酰化米渣分离蛋白的乳化性为5 551 m2/g,为未酰化米渣分离蛋白乳化性的2.64倍。采用响应面法优化琥珀酰化米渣分离蛋白乳化性的工艺条件可靠,具有实用价值。     

琥珀酰化改性对米糠蛋白功能性质的影响

为了改变米糠蛋白的功能性质,扩大米糠蛋白在食品工业的应用范围,利用琥珀酸酐对米糠蛋白进行酰化改性处理。通过单因素反应,确定了琥珀酸酐酰化改性米糠蛋白的最适反应条件为:米糠蛋白浓度为10%,反应温度为35℃,琥珀酸酐/蛋白质用量为15%。在最适反应条件下,分别反应40 min、80 min,制得酰化度分别为46.8%、69.2%的琥珀酰化米糠蛋白。评价了上述两种琥珀酰化米糠蛋白制品的溶解性、乳化性、起泡性等功能性质,结果表明,琥珀酰化改性对米糠蛋白的溶解性、乳化稳定性以及起泡性均有一定改善,而酰化米糠蛋白的乳化活性、泡沫稳定性随着酰化程度的提高有所下降。     

琥珀酰化改性高溶解度大豆分离蛋白的工艺优化

采用琥珀酸酐对大豆分离蛋白进行酰化改性,测定改性前后大豆分离蛋白溶解特性的变化,并建立蛋白质溶解度与改性条件关系的数学模型,利用四元二次正交旋转组合设计试验法优化出琥珀酰化大豆分离蛋白的适宜条件:大豆分离蛋白质量分数7.0%,反应温度54℃,琥珀酸酐添加量11%,反应时间2 h.该条件下制备的酰化蛋白的溶解特性与未改性的大豆分离蛋白相比提高了15.73倍.     

琥珀酰化燕麦分离蛋白制备条件的优化及其结构分析

为提高燕麦分离蛋白(OPI)的溶解性,采用琥珀酰化法对燕麦分离蛋白进行改性。通过单因素实验研究反应温度、p H、酸酐添加量、蛋白浓度对OPI溶解性的影响,同时采用荧光发射光谱对其结构变化进行分析。在单因素实验的基础上,运用响应面法优化出琥珀酰化改性燕麦分离蛋白的适宜条件:反应温度为50℃、p H为8.5、酸酐添加量为10%、蛋白浓度为4%,在此条件下溶解度为68.38%。荧光发射光谱检测得出,琥珀酰化后OPI的荧光强度增强,是由于改性后侧链结构展开,更多的亮氨酸暴露出来所引起。     

小麦面筋蛋白琥珀酰化修饰研究

采用琥珀酸酐对小麦面筋蛋白进行改性修饰，系统研究了底物浓度、改性剂用量和反应温度对反应程度、溶解性、乳化性、起泡性和泡沫稳定性等蛋白功能特性的影响。优化出小麦面筋蛋白琥珀酰化的最佳条件：琥珀酰化底物浓度10％，琥珀酸酐用量15％，反应温度45℃。应用红外光谱对最优条件下改性的面筋蛋白结构进行了表征。将琥珀酰化改性后的小麦面筋蛋白添加至小麦粉中，面团粘着性提高32％。     

酰化改性对大豆分离蛋白凝胶pH响应性的影响

为探讨琥珀酰化改性对大豆分离蛋白(SPI)pH响应性的影响,在特定pH条件下大豆分离蛋白与琥珀酸酐发生酰化反应。通过单因素得出最优条件:酸酐蛋白比0.15、pH 9.0、反应时间30 min,此时酰化程度最高。优化的响应面试验结果表明:酸酐蛋白比16.97%、时间28.11 min、pH 9.32。以葡萄酸内酯(GDL)作交联剂,将改性的大豆分离蛋白制成凝胶;以溶胀性和pH响应性为指标,测定酸酐添加量和GDL添加量对其凝胶性的影响。结论:当GDL添加量3.0%,酸酐添加量12.5%时,大豆分离蛋白凝胶的溶胀性、pH响应性最佳。     

琥珀酰化提高大豆分离蛋白乳化性的研究

为了提高大豆分离蛋白(SPI)的乳化性,采用琥珀酸酐对大豆分离蛋白进行酰化改性。系统研究了SPI质量分数、琥珀酸酐用量和反应温度对大豆分离蛋白乳化性的影响,建立以上3因素与乳化活性和乳化稳定性关系的数学模型,并利用响应面法优化出大豆分离蛋白琥珀酰化的适宜条件:SPI质量分数6.5%、反应温度49℃、琥珀酸酐添加量11.5%。该条件下制备的琥珀酰化蛋白的乳化活性和乳化稳定性与未改性的大豆分离蛋白相比较,分别提高了2.98倍和4.86倍。     

响应面法优化纳米SiOx/鸡蛋清蛋白可食性膜的琥珀酰化改性工艺

目的：以鸡蛋清蛋白为原料,制备纳米SiOx/鸡蛋清蛋白可食性膜,研究琥珀酰化改性工艺对膜性能的影响。方法：以琥珀酸酐添加量、反应时间、反应温度及反应pH值为影响因素,以拉伸强度、断裂伸长率、水蒸气透过系数及透油系数为响应值,采用单因素试验和响应面分析法,优化可食性膜的琥珀酰化改性工艺。结果：建立了回归模型,优化琥珀酰化改性工艺为琥珀酸酐添加量0.70 g、反应时间40.35 min、反应温度34.87 ℃、反应pH 8.30,在此条件下可食性膜拉伸强度、断裂伸长率、水蒸气透过系数及透油系数的预测值分别为4.935 MPa、75.446%、3.499 g·mm/（m2·d·kPa）、0.874 g·mm/（m2·d）,验证值为：（4.891±0.126）MPa、（73.560±4.329）%、（3.651±0.097）g·mm/（m2·d·kPa）、（0.914±0.008）g·mm/（m2·d）,与之接近,优化结果可靠。结论：琥珀酸酐添加量和反应pH值是影响膜性能的主要因素。     

超声-琥珀酰化复合改性提高大豆分离蛋白乳化性的研究

为提高大豆分离蛋白的乳化性,采用超声和琥珀酰化两种方法对大豆分离蛋白进行复合改性。通过单因素实验研究底物浓度、超声功率、超声时间、琥珀酸酐添加量和酰化反应温度对大豆分离蛋白乳化性的影响。在单因素实验的基础上,运用响应面法优化出超声-琥珀酰化改性大豆分离蛋白的适宜条件:超声功率569.36W、超声时间9.79min、酰化温度49.72℃。该条件下制得的改性大豆分离蛋白的乳化活性和乳化稳定性与未改性的大豆分离蛋白相比较,分别提高了3.05倍和4.65倍。     

花生蛋白酸法去酰胺条件的优化及其性质表征

为考察酸法去酰胺改性条件对花生蛋白改性效果和蛋白结构性质的影响,以去酰胺度、水解度以及二者比值为评价指标,分析硫酸浓度、花生蛋白质量浓度、反应时间、反应温度对去酰胺改性的影响,通过正交实验优化改性条件,并对改性花生蛋白的氨基酸组成、二级结构、微观结构与溶解性进行分析。结果表明:硫酸浓度、反应时间与反应温度是花生蛋白去酰胺改性的显著影响因素,同时,硫酸浓度与反应温度也会显著影响蛋白水解。花生蛋白去酰胺的最优条件是:0.30 mol/L硫酸,质量浓度5.5%花生蛋白溶液,85 ℃反应2 h,在此条件下,花生蛋白脱酰胺度为66.98%±0.54%,水解度为10.56%±0.27%,二者比例为6.34。去酰胺改性基本不影响花生蛋白的一级与二级结构,却会影响蛋白聚集形态,并显著(p<0.05)提高蛋白溶解性。     

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.     

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.     

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.     

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.