牦牛肾脂氧化初期脂肪酸动态变化研究

以牦牛肾周脂为研究对象,研究了其在15±1℃下储藏期脂肪酸的动态变化。结果表明:牦牛肾脂肪氧化初期发生于储藏期第0～25d(15±1℃),在此期间,饱和脂肪酸(SFA)含量由49.68%提高至55.96%,多不饱和脂肪酸(PUFA)含量和单不饱和脂肪酸(MUFA)分别由10.73%和37.85%下降至6.95%和28.22%。第0～20d,n-6/n-3PUFA的比率低于4,但在第25d达到4.46,并且MUFA/SFA较PUFA/SFA下降幅度高11.24%。此外,除共轭亚油酸(CLA)和油酸(LA)外,功能性脂肪酸(ARA,EPA,DHA)在10d后下降显著(p<0.05)。     

蒸煮与微波加热对牛肉肌内脂肪中脂肪酸组成的影响

取中国黄牛(公牛)的半腱肌(n=10)用来测定不同加工方式(蒸煮和微波加热)处理在不同中心温度水平(60、70、80 ℃)条件下脂肪酸组成的变化.结果显示,肌内脂肪中极性脂肪、中性脂肪及总脂中脂肪酸组成变化不一致.蒸煮时中性脂肪(NL)中多不饱和脂肪酸(PUFA)增加,而饱和脂肪酸(SFA)保持不变,P/S升高.而蒸煮时极性脂肪(PL)和总脂(TL)中PUFA含量减少,SFA含量升高,导致P/S下降.微波加热时NL、PL和TL中SFA显著增加,PUFA含量降低,但极性脂肪(PL)中PUFA含量降低不显著(p＞0.05),导致NL、PL和TL中P/S显著下降(p＜0.05).M/S比值在两种加工条件下基本没变化.在蒸煮和微波加热条件下,n-6/n-3比值在中心温度达到80℃时比加热到60℃或70℃显著升高.结果提示,大理石花纹丰富的牛肉蒸煮烹饪对脂肪酸的保护效果好于微波加热;牛肉应尽量避免在过高温度(80℃)下处理,以减少营养成分的损失,利于人体健康.     

厦门白姑鱼腌制加工过程中的脂肪酸变化分析

探讨厦门白姑鱼（Argyrosomus amoyensis）腌制加工过程中的脂肪酸的变化,并结合脂肪氧化相关指标：过氧化值（peroxide value,POV）及硫代巴比妥酸反应物（thiobarbituric acid reactive substance,TBARS）值,确定脂肪氧化对脂肪酸组成的影响。从腌制加工的7 个关键工序中取样,采用气相色谱-质谱联用法分析脂肪酸,同时考察POV及TBARS值。结果表明：厦门白姑鱼原料含26.41%的饱和脂肪酸（saturated fatty acids,SFA）、20.26%的单不饱和脂肪酸（monounsaturated fatty acids,MUFA）和53.33%的多不饱和脂肪酸（polyunsaturated fatty acids,PUFA）,共24 种,必需脂肪酸占12.49%,二十碳五烯酸（eicosapentaenoic acid,EPA）和二十二碳六烯酸（docosahexaenoicacid,DHA）占40.70%。在腌制加工中,SFA含量显著增加,MUFA含量和PUFA含量显著降低（P＜0.05）。POV和TBARS值都呈现了先增后减的趋势,分别在烘干1 d和3 d出现峰值。相关性分析表明,SFA与MUFA呈显著负相关（P＜0.05）,与PUFA呈极显著负相关（P＜0.01）,MUFA和PUFA没有相关性;SFA与POV和TBARS值呈现显著正相关（P＜0.05）,而PUFA与POV和TBARS值分别呈显著（P＜0.05）和极显著负相关（P＜0.01）。因此,厦门白姑鱼脂肪酸种类多,含有丰富的不饱和脂肪酸,腌制加工过程对主要8 种脂肪酸有显著影响,脂肪的氧化使SFA含量增加,同时使PUFA含量降低,PUFA更容易发生氧化。     

青海牦牛肉与秦川牛肉氨基酸和脂肪酸的比较研究

通过青海牦牛肉与秦川牛肉的氨基酸和脂肪酸的比较研究,分析青海牦牛肉品质的特性及其潜在优势.选取秦川牛肉,青南、大通和环青海湖地区的成年牦牛肉以及大通犊牦牛肉进行氨基酸和脂肪酸的相关研究.结果表明:牦牛肉各组的蛋白质含量高于秦川牛肉,但差异不显著(P＞0.05);脂肪含量都低于秦川牛肉,差异极显著(P＜0.01).青南地区成年牦牛肉的必需氨基酸/非必需氨基酸(EAA/NAA)值、必需氨基酸/氨基酸总量(EAA/TAA)值、18∶2cis-12,15、α-亚麻酸、20∶0、多不饱和脂肪酸(PUFA)、必需脂肪酸(EFA)、多不饱和脂肪酸/脂肪酸总量(P∶S)值和n-3多不饱和脂肪酸都显著高于秦川牛肉(P＜0.05或P＜0.01);16∶0、二十碳五烯酸(EPA)和n-6/n-3值都显著低于秦川牛肉(P＜0.05或P＜0.01).大通成年牦牛肉的赖氨酸、组氨酸和15∶0都显著高于秦川牛肉(P＜0.05或P＜0.01);月桂酸、亚油酸、PUFA、EFA、n-6多不饱和脂肪酸和n-6/n-3值都显著低于秦川牛肉(P＜0.05或P＜0.01).环湖地区成年牦牛肉的脯氨酸、15∶0、16∶1cis-9、17∶0和18∶2cis-12,15都显著高于秦川牛肉(P＜0.05或P＜0.01);月桂酸和n-6/n-3值都显著低于秦川牛肉(P＜0.05或P＜0.01).大通犊牦牛肉的色氨酸、肉豆蔻酸、17∶1cis-9、18∶1cis-11、亚油酸、α-亚麻酸、20∶3cis-5,8,11、20∶3cis-7,10,13、花生四烯酸(AA)、EPA、PUFA、EFA、P∶S值、n-3多不饱和脂肪酸和n-6多不饱和脂肪酸都显著高于秦川牛肉(P＜0.05或P＜0.01);脯氨酸、14∶1cis-9、棕榈酸、17∶0、油酸、SFA、MUFA和n-6/n-3值都显著低于秦川牛肉(P＜0.05或P＜0.01).结论:青海成年牦牛肉的蛋白质和必需氨基酸含量稍高于秦川牛肉,组成与秦川牛相近,但犊牦牛肉的氨基酸含量稍差一些.牦牛肉的n-6/n-3多不饱和脂肪酸比秦川牛肉合理,都在4.0左右,其中犊牦牛肉的P∶S值为1.15,说明牦牛肉的脂肪酸品质优,尤其是犊牦牛肉.     

肌内脂肪与背最长肌肉质、脂肪酸组成的关系

研究肌内脂肪(IMF)含量与肉质以及脂肪酸含量和组成比例之间的关系.以北京黑猪背最长肌(n=20)为实验材料,测定肌内脂肪含量、肉质以及脂肪酸含量和组成.结果显示,肌内脂肪含量与滴水损失呈显著正相关(P＜0.05),与蒸煮损失、剪切力、肉色的相关性不显著(P＞0.05).随着肌内脂肪含量升高,除长链多不饱和脂肪酸(C20:3n6、C20:4n6)以外的大多数脂肪酸含量增加,相对比例也上升;多不饱和脂肪酸的含量增加,但是相对比例下降;长链多不饱和脂肪酸的含量和相对比例都降低.随着肌内脂肪含量的升高,饱和脂肪酸(SFA)和单不饱和脂肪酸(MUFA)的含量升高,回归方程斜率分别为197.3和248.31,多不饱和脂肪酸(PUFA)增加的幅度不大,回归方程的斜率为11.43.结果提示:肌内脂肪含量较低时(本实验平均值2.86％),对肉质的影响不显著.随着肌内脂肪含量升高,总脂肪酸含量(TFA)增加,主要归因于SFA和MUFA含量的增加.PUFA的含量相对稳定,受肌内脂肪含量变化的影响较小.     

青海牦犊牛肉脂肪酸组成分析

分析青海牦犊牛与成年牦牛肌肉脂肪酸组成特点,将肌肉提取脂肪后进行甲酯化,以脂肪酸酯标样作为标准品,采用气相色谱仪对试样的脂肪酸甲酯进行定性与定量.结果显示,牦犊牛的MUFA、PUFA相对含量极显著高于成年牦牛(P<0.01).分别占到总量的32.38%和11.59%,其中油酸、亚油酸含量尤为突出,分别为29.52%、5.72%,而SFA相对含量为53.54%显著低于成年牦牛的61.04%(P<0.05).牦犊牛PUFA/SFA与n-6/n-3值分别为0.98%、0.22%均极显著高于成年牦牛(P<0.01).青海牦犊牛肉脂肪酸营养价值更高、更均衡,对牦犊牛的选育、肉品深加工具有一定意义.     

电子束辐照对手撕牛肉贮藏品质的影响

以真空包装的手撕牛肉为材料,辐照剂量分别为2、5、8、10、15、20 kGy,研究高能电子束辐照对手撕牛肉品质的影响。探究在不同辐照剂量下,手撕牛肉在25℃下贮藏63 d过程中的品质变化。结果表明,辐照处理组的手撕牛肉在贮藏期内的菌落总数较对照组明显减少;当辐照剂量大于8 kGy时,能明显延长手撕牛肉的贮藏期;电子束辐照对手撕牛肉的剪切力、咀嚼性和pH值并未产生明显影响;对硫代巴比妥酸（thiobarbituric acid,TBA）值的影响较小;随着辐照剂量的增加,感官评分出现一定程度的下降,当辐照剂量大于10 kGy时,辐照组的色泽评分明显低于对照组。综合分析各项指标可得：8 kGy～10 kGy的辐照剂量既能最大限度保留手撕牛肉的原本品质,又能保障其安全性。     

蒙古斑点马不同部位脂肪和肌肉组织中脂肪酸组成的比较研究

通过对蒙古斑点马不同部位脂肪和肌肉组织中脂肪酸组成进行分析比较,旨在明确蒙古斑点马体脂脂肪酸组成特点。选择3 匹成年蒙古斑点马,屠宰后采集肾周、肠周和皮下脂肪以及肩肌、背最长肌和臀肌样品,利用气相色谱法测定脂肪酸组成及含量。结果表明：蒙古斑点马不同脂肪组织中均检出19 种脂肪酸,其中饱和脂肪酸（saturated fatty acid,SFA）含量34.77%～37.38%,不饱和脂肪酸（unsaturated fatty acid,UFA）含量达60%以上,UFA中单不饱和脂肪酸（monounsaturated fatty acid,MUFA）含量33.04%～36.39%,多不饱和脂肪酸（polyunsaturated fatty acid,PUFA）含量26.47%～27.51%,其中皮下脂肪C10:0、C18:0、C20:0含量显著低于肾周和肠周脂肪（P＜0.05）;MUFA在皮下脂肪的沉积程度较其他2 个部位高,但均无统计学差异;PUFA中C18:3 n-3含量最高,其在各脂肪组织间无显著差异。3 个不同部位肌肉中均检出15 种脂肪酸,其中SFA含量占总脂肪酸含量的38.32%～40.04%,MUFA含量占35.70%～40.19%,PUFA含量占15.25%～20.33%;SFA中背最长肌和臀肌C12:0含量显著高于肩肌（P＜0.05）,其余SFA在不同部位肌肉间无显著差异;MUFA中背最长肌C16:1含量显著高于肩肌和臀肌（P＜0.05）;肩肌n-6/n-3 PUFA比值显著高于背最长肌和臀肌（P＜0.05）;皮下脂肪的C18:3 n-3和总PUFA含量显著高于背最长肌（P＜0.05）。综上所述,蒙古斑点马不同部位脂肪和肌肉组织脂肪酸组成各具特点,但UFA含量均较高。     

不同处理后的四川白兔肌内脂肪酸组成在冷藏过程中的变化

研究了用4种不同的处理方式(微波、烘烤、蒸煮、和超声波辅助腌制)对四川白兔的后腿肌(hind leg muscle,HL)进行处理后再用2种不同包装方式进行包装(非真空和真空包装),分析样品在冷藏过程中肌内总脂肪含量及脂肪酸组成的变化。结果表明,四川白兔肌内脂肪主要含20种脂肪酸,多数为不饱和脂肪酸。在0~12 d的冷藏过程中,4种方式处理后的四川白兔肌内脂肪含量显著下降(P0.05)。相对其他处理方式来说,微波处理对不饱和脂肪酸(UFA)尤其是多不饱和脂肪酸(PUFA)的影响较小,而蒸煮对PUFA破坏作用最大。随冷藏时间的延长,饱和脂肪酸(saturated fatty acid,SFA)的含量升高显著(P0.05),UFA、PUFA含量与P/S(PUFA/SFA)、n-6/n-3(n-6系列PUFA/n-3系列PUFA)的比值显著降低(P0.05),而单不饱和脂肪酸(MUFA)含量变化不显著。从脂肪氧化角度来看,处理后兔肉中丙二醛(MDA)的沉积量在0~10 d冷藏期间内不断升高,且耐贮性不断降低。真空包装的样品在饱和脂肪酸(saturated fatty acid,SFA)上升与UFA下降的趋势方面有减缓作用,同时将TBA值维持在较低的水平,延缓了加工肉品的腐败变质。     

不同温度处理的风干牛肉贮藏过程中脂肪变化

为了研究干燥温度对风干牛肉贮藏过程中脂肪酸组成的变化规律,选取新疆褐牛后腿肉为研究对象,经腌制后分别进行20 ℃ 48 h、40 ℃ 20 h、50 ℃ 12 h、60 ℃ 8 h的风干处理,冷却后置于4 ℃冰箱贮藏,分别在第0、15、30天和第60天取样,检测其pH值、过氧化值、酸价、硫代巴比妥酸反应底物（thiobarbituric acid reaction substrate,TBARS）值、脂肪含量和脂肪酸组成变化。结果表明：随着贮藏时间的延长,pH值先降低后略微升高（P＞0.05）;处理温度对脂肪含量影响显著（P＜0.05）,而贮藏时间对脂肪含量影响不显著（P＞0.05）;相同温度处理的样品过氧化值、酸价和TBARS值随着贮藏时间的延长呈增加的趋势;处理温度对风干牛肉中肌内脂肪酸组成、甘油三酯和磷脂相对含量影响也不明显,但对游离脂肪酸含量影响较明显,且温度越高,游离脂肪酸相对含量越高;与20 ℃处理组相比,60 ℃处理组样品中游离脂肪酸相对含量在0、15、30、60 d分别增加了0.84%、1.82%、1.45%、1.14%;50、60 ℃处理组的样品随着贮藏时间的延长,磷脂脂肪酸中多不饱和脂肪酸（polyunsaturated fatty acid,PUFA）相对含量降低,游离脂肪酸中的PUFA相对含量增加。本实验结果可为阐明不同温度影响风干牛肉加工过程中风味形成的原因提供一定参考。     

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.