室温下不同植物油开封后最佳食用期研究

以6种常见食用植物油亚麻籽油、葵花籽油、菜籽油、大豆油、花生油、芝麻油为原料,测定其脂肪酸含量,并在模拟家庭环境下每间隔5 d测定其过氧化值,从而研究开封后植物油最佳食用期及其与脂肪酸含量的关系。研究结果表明:亚麻籽油、菜籽油开封后的最佳食用期均为15～20 d,大豆油、葵花籽油的最佳食用期最长不超过25 d,花生油、芝麻油最佳食用期应为25～30 d。油脂氧化情况与其不饱和脂肪酸的含量成正比,不饱和脂肪酸含量越高,油脂越容易被氧化,最佳食用期越短。     

不同冻藏温度和时间对沙棘果中Vc含量的影响

将沙棘速冻后分别在-10、-20℃和-30℃条件下冻藏90 d,每隔一段时间测定其Vc含量的变化.结果表明冻藏过程中沙棘的vc含量随冻藏时间的增加而逐渐降低;不同冻藏温度对沙棘Vc含量也存在影响,冻藏温度越低其Vc损失越小,-30 ℃冻藏时沙棘的Vc损失最小.     

冻藏条件对带鱼鱼肉及其鱼糜凝胶特性的影响

为研究不同冻藏条件对带鱼鱼肉及其鱼糜凝胶特性影响,将新鲜带鱼分别置于-7、-13、-18和-23℃下冻藏15～120 d,期间测定带鱼鱼肉理化特性(羰基、巯基、Ca²⁺-ATPase活性、TBARS),随后将鱼肉制成鱼糜凝胶后测定凝胶特性(色泽、凝胶强度、持水力),并结合扫描电镜观察微观结构。结果表明,随着冻藏时间的延长,鱼肉羰基含量和TBARS值逐渐升高,巯基含量和Ca²⁺-ATPase活性下降。冻藏温度越低,鱼肉的各项指标变化程度越小。除-7℃冻藏60 d后的样品TBARS值大于0.58 mg MDA/kg外,其余样品均未发生腐败。随冻藏时间的延长,带鱼鱼糜凝胶色泽逐渐劣变,持水力逐渐降低,冻藏温度越低色泽和持水力的变化越小。带鱼鱼肉在四个温度下冻藏120 d制成的鱼糜凝胶,其凝胶强度分别下降了72.33%、54.13%、39.17%和29.31%。通过SEM观察发现更低的冻藏温度能够使鱼糜凝胶保持良好的三维网状结构,抑制带鱼凝胶的劣变。综上,随冻藏时间的延长,带鱼鱼肉及其鱼糜凝胶特性逐渐劣变,随着冻藏温度由-7℃降低到-23℃,劣变过程...     

解冻方式对牦牛乳品质的影响

牦牛乳营养丰富，由于泌乳期较短人们常用冻藏的方式贮存，但是不同解冻方式对牦牛乳的品质有一定的影响。本研究观察不同解冻方式（4℃冷藏解冻、室温静水解冻、40℃水浴解冻、微波解冻）下-20℃和-40℃冻藏乳的品质差异。结果显示，静水解冻的冻结乳pH较低，菌落总数最多，在微生物的作用下营养成分含量也最低；冷藏解冻的冻结乳脂肪聚集程度最明显，稳定性最差；由于微波温度较高，使得微波解冻下牦牛乳的脂肪氧化度和蛋白水解度较高，营养成分含量偏低。相比较而言，40℃水浴解冻后乳的稳定性较高，解冻时间快，营养成分损失较少。此外，-40℃冻藏乳的蛋白和脂肪含量显著大于-20℃冻藏乳，提示冻结速率越快解冻时对乳品质的影响越小。     

不同冻藏温度对金枪鱼肉肉色变化的影响

以黄鳍金枪鱼背部肌肉为研究对象,测定不同的冻藏温度(-18℃,-25,-55℃)对肌肉颜色(a*值)、高铁肌红蛋白的含量、脂肪氧化的影响。结果表明:随着冻藏时间的延长,a*值呈下降趋势;高铁肌红蛋白含量增加、脂肪氧化值增加;在不同的冻藏温度下,肌肉a*值变化显著(p<0.05);冻藏温度越低,a*值,脂肪氧化值变化越小,肌红蛋白氧化成高铁肌红蛋白的量越少。     

煎炸时间对植物油脂中脂肪酸含量的影响

目的探讨不同煎炸时间对大豆油、花生油和芝麻油3种植物油脂脂肪酸含量变化的影响。方法选取煎炸温度为350℃,煎炸时间分别为0.5、1、3、5、7、25 h,用氢氧化钾-甲醇溶液进行甲酯化,并采用气相色谱-质谱法(gas chromatography-mass spectrometry)对脂肪酸甲酯化溶液进行定量分析。结果随着煎炸时间的延长,油脂中总脂肪酸含量呈现递减趋势。其中,油脂中饱和脂肪酸(SFA)的总含量均呈递增趋势,而不饱和脂肪酸(UFA)的总含量均呈递减趋势。结论煎炸25 h后的大豆油、花生油和芝麻油的饱和脂肪酸(SFA)含量分别由19.03%、14.68%、17.54%增至33.01%、23.24%、27.41%,变化率分别为58.45%、34.43%、56.34%,从饱和脂肪酸的变化率来看,花生油相对更稳定。而其不饱和脂肪酸(UFA)分别由80.84%、85.21%、82.39%减少到59.67%、68.97%、69.41%,变化率分别为19.06%、26.18%、15.75%,从不饱和脂肪酸来看,芝麻油更具稳定性。     

冻结及冻藏温度对小龙虾蛋白质理化性质的影响

将小龙虾热烫后置于真空包装盒内,灌水并抽真空,分别于3个冻结温度(-20,-40,-55 ℃)下冻结至中心温度为 -15 ℃,并置于2个冻藏温度(-20,-40 ℃)中冻藏24周,测定不同冻结温度处理和冻藏的小龙虾肉的肌原纤维蛋白含量、表面疏水性、内源荧光强度、总巯基和二硫键含量、二级结构的变化。结合冰晶的显微结构观察结果,探讨冻结及冻藏温度对小龙虾蛋白质理化性质的影响,为小龙虾加工原料的周年供应提供理论指导。试验结果显示:在冻藏温度相同时,-20 ℃冻结小龙虾肉的冰晶较大,导致肌肉结构受到严重的破坏,肌原纤维蛋白含量显著低于-40,-55 ℃冻结(P<0.05)的表面疏水性、内源荧光强度、总巯基和二硫键含量差异不显著(P>0.05)。在冻结温度相同时,-20 ℃冻藏小龙虾肉的冰晶更大,出现针形冰晶的时间更早,肌原纤维蛋白含量、总巯基含量显著低于-40 ℃(P<0.05),表面疏水性、二硫键含量显著高于-40 ℃(P<0.05),内源荧光强度变化幅度更大。此外,-20 ℃冻结或冻藏时,α-螺旋的相对含量较高,而β-折叠、β-转角和无规卷曲无明显差别。这些结果表明,较低的冻结及冻藏温度使小龙虾肉蛋白的空间构象更稳定,减轻了蛋白质的变性程度,使冻藏期间小龙虾的品质更好。     

低温胁迫肌原纤维蛋白结构和热稳定性的变化

本文研究了冻藏温度(-5,-18,-26,-35,-70℃)、冻藏时间(0,1,3,6,9,12 mon)对猪肉背最长肌中的蛋白质结构(ATPase酶活性、巯基含量、SDS-聚丙烯酰氨凝胶电泳)和热稳定性的影响。结果表明:随着冻藏温度的降低,12 mon蛋白质总巯基含量、活性巯基含量、Ca~(2+)-ATPase活性、K~+-ATPase活性呈递减趋势;通过DSC测定蛋白的热稳定性,冻藏过程中肌肉蛋白的热转变温度和焓值均降低,且冻结温度越高冻藏时间越长,温度和焓值降低得越明显;蛋白的SDS-PAGE电泳图谱结果显示,冻藏时间越长冻藏温度越高,蛋白质分子降解越明显。     

冻藏温度对南极磷虾品质变化的影响

本文以感官评分、持水力(WHC)、盐溶性蛋白质含量(SSP)、硫代巴比妥酸反应物(TBARS)为指标,研究了(-20、-30、-40、-50±1)℃四个冻藏温度对南极磷虾品质变化的影响。结果表明,冻藏温度对南极磷虾的品质变化影响差异显著(P0.05),冻藏温度越高,时间越长,南极磷虾的感官品质和肌肉持水能力越差,蛋白变性和脂肪氧化程度越高。冻藏过程中南极磷虾品质变化趋势基本一致,在-20、-30、-40、-50℃下冻藏180 d后,WHC分别下降了18.27%、15.00%、16.04%、12.92%,SSP分别下降了32.66%、33.99%、24.95%、21.84%,TBARS分别上升了76.38%、78.09%、65.71%、53.55%。-20℃冻藏南极磷虾品质变化较快,在200 d时感官品质难以接受,-30℃冻藏200 d时,感官品质尚可接受,-40℃和-50℃冻藏南极磷虾品质较好,冻藏温度越低越有利于南极磷虾品质的保持。因此,南极磷虾需长期贮藏建议冻藏温度在-30℃及以下。     

冻藏温度对海鲈鱼鱼糜蛋白生化指标及其凝胶特性的影响

为了研究不同冻藏温度下鱼糜品质的变化,以无添加剂的海鲈鱼鱼糜为原料,研究3种不同冻藏温度在6周时间内对鱼糜的理化特性和流变特性的影响。结果表明:随着冻藏时间延长,鱼糜的盐溶蛋白含量、Ca2+-ATPase活性、总巯基含量、保水性、白度值和凝胶强度均呈下降趋势,而挥发性盐基氮(TVB-N)含量呈上升趋势,各指标数值在4周以后进入稳定期,变化减少。在不同冻藏温度下的鲈鱼蛋白变性速率差异显著(p0.01),冻藏温度越低,蛋白变性速率越慢,并对鱼糜的微观结构进行观察,阐释其机理。鱼糜在-24℃以下冻藏效果较好,冻藏6周后鱼糜还处于一般鲜度以上。鱼糜的机械模量(G’和G’’)随冻藏时间延长而下降,且随冻藏温度的升高其变化也越明显。无添加剂的海鲈鱼鱼糜在-24℃以下储藏6周之内可有效延缓其品质的劣变。     

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.