家畜肌内脂肪沉积过程相关基因研究进展

肌内脂肪的含量是影响肉品质的重要因素之一,其含量会影响肉的嫩度及风味等理化性质。文章结合肌内脂肪沉积的相关过程,包括脂肪酸的转运、脂肪的合成代谢、脂肪的分解代谢,阐述了脂肪酸结合蛋白(FABPs)、脂肪酸合成酶(FAS)、乙酰辅酶A羧化酶(ACC)、激素敏感脂酶(HSL)、脂蛋白酯酶(LPL)作为肌内脂肪沉积的候选基因在不同品种中的表达规律,旨在为提高畜肉品质提供一定参考,并对未来的研究方向进行展望。     

基因与肉品质关系的研究进展

氟烷基因和RN-基因是影响肉品质的主效基因,氟烷基因的表达调控导致了PSE肉的产生,RN-基因则主要使肌肉pH下降,从而产生酸肉.除此之外,影响肉品质的候选基因还有脂肪酸结合蛋白(FABP),主要调控肌内脂肪(IMF)的表达,IMF是肉食用品质的因素之一,决定肉的质地的肌纤维类型及其含量受到了钙蛋白酶抑制蛋白(CAST)和MyoD基因的调控,肉的嫩度则与钙蛋白酶基因的表达有关.     

基因与肉品质关系的研究进展

氟烷基因和RN-基因是影响肉品质的主效基因,氟烷基因的表达调控导致了PSE肉的产生,RN-基因则主要使肌肉pH下降,从而产生酸肉。除此之外,影响肉品质的候选基因还有脂肪酸结合蛋白（FABP）,主要调控肌内脂肪（IMF）的表达,IMF是肉食用品质的因素之一,决定肉的质地的肌纤维类型及其含量受到了钙蛋白酶抑制蛋白（CAST）和MyoD基因的调控,肉的嫩度则与钙蛋白酶基因的表达有关。      

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(C_20:3n6、C_20:4n6)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。      

脂肪酸代谢与骨骼肌收缩相关基因对羊肉品质影响的研究进展

肉质受到多种因素的影响,遗传因素中的基因对肉质的调控起主导作用。脂肪酸代谢和骨骼肌收缩与肉的风味、嫩度和肌纤维的密度存在密切相关性,进而影响肌间脂肪的蓄积、肌肉纤维的发育和肌肉含水率等肉质性状。本文主要对影响脂肪酸代谢的脂素1基因、二乙酰基甘油酰基转移酶1基因、脂肪组织甘油三酯水解酶基因和影响骨骼肌收缩的骨骼肌快速肌钙蛋白基因、原肌球蛋白3基因的功能及其对肉质的调控机理进行介绍,并对基因影响肉质的研究现状进行综述。      

脂肪酸代谢与骨骼肌收缩相关基因对羊肉品质影响的研究进展

肉质受到多种因素的影响,遗传因素中的基因对肉质的调控起主导作用。脂肪酸代谢和骨骼肌收缩与肉的风味、嫩度和肌纤维的密度存在密切相关性,进而影响肌间脂肪的蓄积、肌肉纤维的发育和肌肉含水率等肉质性状。本文主要对影响脂肪酸代谢的脂素1基因、二乙酰基甘油酰基转移酶1基因、脂肪组织甘油三酯水解酶基因和影响骨骼肌收缩的骨骼肌快速肌钙蛋白基因、原肌球蛋白3基因的功能及其对肉质的调控机理进行介绍,并对基因影响肉质的研究现状进行综述。     

乌珠穆沁肉羊自然放牧条件下肌内脂肪相关基因表达分析

为研究自然放牧条件下不同月龄乌珠穆沁肉羊的股二头肌、肱三头肌、背最长肌3个部位骨骼肌肌内脂肪相关基因的表达,采用实时荧光定量聚合酶链式反应(polymerase chain reaction,PCR)技术测定肉羊生长过程中过氧化物酶体增殖剂激活受体γ亚型(peroxisome proliferator activated receptors,PPARγ)和脂肪酸合成酶(fatty acid synthase,FAS)相关基因(PPARγ、FAS)表达量。结果表明:两种基因表达量在各部位骨骼肌上的趋势相近。PPARγ基因的表达量在1月龄和12月龄较高,9月龄和18月龄较低;FAS基因的表达量在3月龄和12月龄较高,9月龄和18月龄较低。通过对基因表达量与肌内脂肪的相关性分析可以得出,PPARγ基因和FAS基因的表达量与肌内脂肪含量呈负相关。     

饲养方式对苏尼特羊脂肪组织中脂肪代谢相关基因表达量的影响

以12 月龄放牧和圈养条件下的苏尼特羊肌内脂肪、尾脂和肾脂为实验材料,采用实时荧光定量聚合酶链式反应技术,研究饲养方式对苏尼特羊脂肪组织中脂肪代谢相关基因表达量的影响。结果表明：在圈养条件下,硬脂酰辅酶A去饱和酶（stearoyl-coenzyme A desaturase,SCD）基因在脂肪组织中表达量显著高于放牧组（P＜0.05）;放牧条件下,脂肪酸脱氢酶I（Δ5-fatty acid desaturases,FADS1）、脂肪酸脱氢酶II（Δ6-fatty acid desaturases,FADS2）、脂肪酸延长酶5（elongase of very long chain fatty acid 5,Elove5）和过氧化物酶体增殖物激活受体γ（peroxisome proliferator-activated receptor,PPARγ）基因在脂肪组织中表达量高于圈养条件（P＞0.05）,放牧组脂蛋白脂酶基因在尾脂和肾脂中的表达量高于圈养组（P＜0.05）。不同脂肪组织间脂肪代谢相关基因的表达量存在显著差异,在肌内脂肪中FADS1、FADS2、Elove5和脂肪酸β-氧化关键酶肉碱棕榈酰转移酶1（carnitine palmitoyltransferase I,CPT1）基因表达量显著高于尾脂和肾脂（P＜0.05）;在尾脂和肾脂中PPARγ基因的表达量显著高于肌内脂肪（P＜0.05）。脂肪代谢基因相关性研究中,在尾脂中,乙酰辅酶A羧化酶（acetyl-CoA carboxylase,ACC）基因的表达可以极显著促进SCD基因表达（P＜0.01）,有助于脂肪中单不饱和脂肪酸沉积。     

不同部位荣昌猪肉中脂肪含量和脂肪酸组成对比

研究不同部位猪肉中脂肪含量和脂肪酸组成的变化规律,以荣昌猪4个不同部位的肌肉为原料,对比四者脂肪含量和肌内总脂、甘三酯、磷脂、游离脂肪的脂肪酸组成。结果显示：4部位肌内总脂和甘三酯含量有显著差异(P＜0.05),而磷脂和游离脂肪酸的含量差异不显著(P＞0.05);4部位总脂肪酸和游离脂肪组成有显著差异(P＜0.05),而甘三酯和磷脂的脂肪酸组成差异不显著(P＞0.05)。由于游离脂肪酸在肌内脂肪中比较很小,不足以对总脂肪酸组成产生显著影响,因此不同部位荣昌猪样品间肌内脂肪含量和脂肪酸组成的显著差异主要都是由肌内甘三酯含量的显著差异引起的。     

日龄对麻鸭脂肪沉积及相关基因表达的影响

为研究日龄对麻鸭脂肪沉积的影响及肌内脂肪对肉质的影响,选取4?组不同日龄麻鸭,测定了不同日龄麻鸭的肌内脂肪质量分数、皮脂率、腹脂率、蒸煮损失率、剪切力、pH值。利用实时荧光定量聚合酶链式反应法测定两组日龄下3?个脂肪代谢相关基因的荧光值并计算其表达量,探讨了CIDEa基因、脂肪酸合成酶（fatty acid synthase,FAS）基因、甘油三酯脂肪酶（adipose triglyceride lipase,ATGL）基因的表达量与麻鸭脂肪沉积的关系。结果表明：随着日龄的增加,麻鸭脂肪质量分数显著升高（P＜0.05）,其中肌内脂肪质量分数的变化与pH值、剪切力、蒸煮损失率密切相关;CIDEa基因和FAS基因在脂肪质量分数丰富的组织中表达量较高,且CIDEa基因在高日龄麻鸭中表达量显著升高（P＜0.05）。本研究为探究日龄对麻鸭生长发育过程中脂肪沉积以及脂肪沉积对肌肉品质变化的影响提供了一定的理论依据。     

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.     

Chlorohydrins of bisphenol A diglycidyl ether (BADGE) and of bisphenol F diglycidyl ether (BFDGE) in canned foods and ready-to-drink coffees from the Japanese market

BADGE.2HCl and BFDGE.2HCl were determined in 28 samples of ready-to-drink canned coffee and 18 samples of canned vegetables (10 corn, 5 tomatoes and 3 others), all from the Japanese market. HPLC was used as the principal analytical method and GCMS for confirmation of relevant LC fractions. BADGE.2HCl was found to be present in one canned coffee and five samples of corn, BFDGE.2HCl in four samples of canned tomatoes and in one canned corn. No sample was found which exceeded the 1mg/kg limit of the EU for the BADGE chlorohydrins. However the highest concentration was found for the sum of BFDGE.2HCl and BFDGE.HCl.H₂O at a level of 1.5mg/kg. A Beilstein test confirmed that all cans containing foods contaminated with BADGE.2HCl or BFDGE.2HCl had at lest one part coated with a PVC organosol.     

European priorities for research to support legislation in the area of food contact materials and articles

A strong science base is required to underpin the planning and decision-making process involved in determining future European community legislation on materials and articles in contact with food. Significant progress has been made in the past 5 years in European funded work in this area, with many developments contributing to a much better understanding of the migration process, and better and simpler approaches to food control. In this paper this progress is reviewed against previously identified work-areas (identified in 1994) and conclusions are reached about future requirements for R&D to support legislation on food contact materials and articles over the next 5 or so years.     

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.