基于保活和品质变化规律分析缢蛏(Sinonovacula constricta)贮藏过程中的代谢特性

研究缢蛏在不同温度条件下(-4±1℃,0±1℃,5±1℃,10±1℃,25±1℃)贮藏的存活率、基本营养成分(水分、糖原、粗脂肪、粗蛋白和灰分)、生化特性(挥发性盐基氮、p H、肌原纤维蛋白巯基含量及Ca~(2+)-ATPase活力)和菌落总数的变化规律及特征。结果表明:不同贮藏温度下,缢蛏的存活时间分别为0 d、11 d、9 d、5 d、3 d。不同温度条件贮藏过程中,缢蛏的水分和粗蛋白含量基本保持稳定,消耗能量物质时以糖原为主粗脂肪为辅。贮存11 d后,糖原下降幅度约为54.86%~69.45%,其次粗脂肪下降幅度约为21.69%~28.92%。p H呈先下降后上升的趋势。缢蛏的肌原纤维蛋白巯基含量和Ca2+-ATPase活性总体呈下降趋势。不同温度(0±1℃、5±1℃、10±1℃、25±1℃)贮藏期间,分别在11 d、9 d、7 d、5 d、2 d缢蛏TVB-N值接近海水贝类最大可接受限值15 mg/100g;缢蛏的菌落总数分别于7 d、5 d、3 d、2 d接近4.7 log(CFU/g)。研究表明,(0±1)℃无水保活期间缢蛏营养损失和生化特性变化均较缓慢,且保持良好的鲜活状态。     

滩羊肉成熟过程中糖酵解与保水性之间的关系

为阐明滩羊肉成熟过程中糖酵解程度与保水性的关系,以6月龄滩羊背最长肌(M.longissimus dorsi)为研究对象,分析其4℃成熟0、1、2、3、4、8 d时滴水损失率、贮藏损失率、离心损失率、钙蛋白酶-1活性、肌原纤维小片化指数、ATP含量、葡萄糖含量、糖原含量、乳酸含量、乳酸脱氢酶活性、丙酮酸激酶活性以及pH值的变化情况。结果表明,随成熟时间的延长,滩羊背最长肌的滴水损失、贮藏损失及离心损失呈先增大后减小的趋势(P<0.05),并在成熟4 d时达到最大;ATP、糖原含量持续下降(P<0.05);葡萄糖、乳酸含量呈先上升后下降趋势(P<0.05);乳酸脱氢酶活性呈先增大后减小的趋势(P<0.05),并在成熟4 d时达到最大;丙酮酸激酶活性呈持续下降趋势(P<0.05)。相关性分析结果表明,糖原含量与滴水损失呈显著负相关(P<0.05),与贮藏损失、离心损失呈极显著负相关(P<0.01),与T₂₁、T₂₂、T₂₃均呈显著正相关(P<0.05,P<0.01);乳酸...     

近江牡蛎在净化和生态冰温保活过程中主要营养成分的变化

近江牡蛎经过臭氧净化后分为薄膜包装组和散装组在5℃进行生态冰温保活;在净化前后和保活1、3、5、7、9d分别取样,分析上述过程中主要营养成分的变化。结果表明:净化前后牡蛎的主要营养成分基本未发生变化;在生态冰温保活过程中粗蛋白和水分基本保持稳定,粗脂肪和糖原呈明显下降趋势,而乳酸呈显著的上升趋势。与保活前相比,薄膜包装组粗脂肪、糖原分别降低了55.7%和29.2%,乳酸含量增加了57.3%;散装组脂肪、糖原分别降低了51.2%和41.0%,乳酸含量增加了107.7%。由结果可知,薄膜包装组主要营养成分的损失较小。     

核桃多肽抗疲劳作用的研究

用不同剂量(200、400、800mg/kg·d)的核桃多肽给小鼠灌胃,测定其血清和组织中乳酸、肌糖原、肝糖原和尿素氮含量,观察其对小鼠负重游泳实验的影响。结果表明:经过30d的实验,各实验组小鼠负重游泳力竭时间均极显著延长(p<0.01),血清尿素氮的含量均极显著下降(p<0.01)。高剂量组血清乳酸含量极显著下降(p<0.01),中剂量组和低剂量组血清乳酸含量均显著下降(p<0.05)。组织中肌糖原含量均极显著升高(p<0.01),肝糖原含量均显著升高(p<0.05)。结果表明核桃多肽具有较好的抗疲劳功效。     

黄颡鱼无水保活技术研究

研究了黄颡鱼在生态冰温区的无水保活运输技术、相关的影响因子及鱼体肌肉和血液中生化指标的变化.结果表明:黄颡鱼的生态冰温区为-1～4℃,黄颡鱼暂养2d后,在低温(2℃)纯氧状态下可保活24h,且可在常温水中(20℃)完全复苏;在保活过程中,肌肉中糖原含量、pH下降、乳酸含量上升,血液中肌酐、血糖、乳酸含量显著上升,白蛋白显著下降,尿酸显著上升;保活前后,除肌酐、血糖、乳酸外其他各项指标没有显著变化.     

冷却方式对黄羽肉鸡胴体僵直进程与品质的影响

以黄羽肉鸡为研究对象,探讨宰后肉鸡胴体自来水降温至25 ℃、冰水浸泡冷却及冰水浸泡结合低温冷风的混合冷却对肉鸡僵直进程和鸡肉品质的影响。结果表明：鲜光鸡肌糖原酵解产生乳酸的速度较快,导致肉的pH值快速降低,4 h左右即进入僵直期。冰鲜鸡在4 ℃下储藏,低温减缓了肌糖原酵解产生乳酸及pH值降低的速度,低温对延缓肉鸡进入僵直期有明显效果。鲜光鸡弹性的降速及降幅显著大于（p<0.05）冰鲜鸡;混合冷却在储藏后期,弹性略优于（p>0.05）冰水直接冷却。在储藏过程中,胸肉的剪切力下降的速率和幅度明显高于腿肉,特别是鲜光鸡胸肉由0 h的59.55±2.71 N/mm2降至4 h的36.73±1.61 N/mm2,腿肉的剪切力变化相对较小。鲜光鸡胸肉及腿肉中可溶性蛋白含量显著高于（p<0.05）冰鲜鸡样品,混合冷却略高于水冷样品。因此,冰水浸泡冷却是导致鸡肉中可溶性蛋白损失和冰鲜鸡滋味逊于鲜光鸡的主要原因。     

微生物接种剂和酶制剂对黑麦草青贮发酵品质的影响

通过在室温23±2℃条件下添加乳杆菌、乳球菌和纤维素酶青贮黑麦草,以评价其单独或联合应用对黑麦草青贮发酵品质的影响.试验分为4组:对照组、乳杆菌组、乳杆菌和乳球菌复合添加组及乳杆菌和纤维素酶复合添加组.结果表明:单独添加乳杆菌、乳杆菌与乳球菌复合添加对黑麦草pH值无明显影响(P>0.05),但发酵质量较对照组有所改善.与对照组相比,乳杆菌和纤维素酶的复合添加明显降低了pH值(P<0.05),增加了发酵产物乳酸(P<0.01)的含量,明显降低了NH3-N(P<0.05)、NDF(P<0.01)和ADF(P<0.05)的含量,蛋白质损失减少约8%,但丁酸含量略高于其他组.因此,乳杆菌和纤维素酶联合添加可显著改善黑麦草青贮发酵品质.     

不同年龄和部位羊肉中AMPK活性与糖酵解的差异

选取6月龄和18月龄宰后绵羊不同部位的骨骼肌,分别测定它们的AMPK活性和糖酵解各指标,研究不同年龄和部位羊肉中二者的差异,以探讨肌肉宰后生理的机理。结果表明:18月龄绵羊的AMPK活性极显著大于6月龄羊(P<0.01),pH下降幅度、肌糖原含量、乳酸含量和己糖激酶活性均极显著高于6月龄羊(P<0.01),乳酸脱氢酶活性显著高于6月龄羊(P<0.05)。并且同一年龄羊的各不同部位肌肉中AMPK活性和糖酵解也存在差异,运动量大的部位AMPK活性高,糖酵解速度快。因此得到结论,肌肉的AMPK活性较高时糖酵解速度也较快,反之较慢。     

不同预冷时间下鮰鱼能量代谢和加工品质的相关性分析

为了研究不同预冷时间下淡水鱼能量代谢和加工品质的相关性,本实验以鮰鱼为研究对象,分别测定了鮰鱼宰杀后在4℃下预冷48 h内的能量物质(糖原、乳酸、三磷酸腺苷(adenosine-5’-triphosphate,ATP)及其关联物含量)、代谢酶(己糖激酶(hexokinase,HK)、丙酮酸激酶(pyruvate kinase,PK)、乳酸脱氢酶(lactate dehydrogenase,LDH)、肌酸激酶(creatine kinase,CK))活力、理化品质(pH值、蒸煮损失率、加压失水率、质构特性、K值、色泽)变化。结果表明:随着预冷时间的延长,鮰鱼中糖原和乳酸含量在24 h内不断下降,随后开始积累;二磷酸腺苷、一磷酸腺苷、肌苷酸含量逐渐降低,次黄嘌呤、肌苷含量逐渐升高,ATP几乎检测不到;HK活力不断下降,PK活力在预冷8 h后上升至最大值,随后不断下降,LDH及CK活力均呈波动式下降;pH值和剪切力逐渐下降;加压失水率、蒸煮损失率以及色泽在24 h内保持稳定,在48 h后显著上升(P0.05),鱼肉的持水性下降;K值不断上升,并在24 h内保持在20%的高鲜度范围内。通过相关性分析发现:糖原含量和乳酸含量呈显著正相关(P0.05);K值与HK活力呈显著负相关(P0.05),与白度呈极显著正相关(P0.01);LDH活力与CK活力、剪切力呈显著正相关,与白度呈显著负相关(P0.05);加压失水率与蒸煮损失率呈显著正相关(P0.05)。宰后鮰鱼在预冷24 h内更有利于其在加工过程中的品质控制。     

海蛾鱼提取物抗氧化及抗疲劳作用

对海蛾鱼水提物及醇提物的抗氧化及抗疲劳作用进行了研究。通过测定DPPH自由基清除率、β-胡萝卜素褪色抑制率及FRAP值来研究提取物的抗氧化作用;通过测定小鼠转棒停留时间、小鼠强迫游泳时间、肝糖原、肌糖原、血糖、血清尿素氮及血乳酸含量等指标来研究海蛾鱼提取物的抗疲劳作用。海蛾鱼醇提物对DPPH自由基清除IC₅₀为1.22 mg/mL,抑制胡萝卜素褪色IC₅₀为1.18 mg/mL,FRAP值为383.35 μmol/g。海蛾鱼水提物可显著提高小鼠转棒滞留时间,400 mg/kg剂量组其滞留时间为(61.81±8.57)s(p<0.01);水提物在400 mg/kg剂量时可显著(p<0.05)延长小鼠强迫游泳时间;海蛾鱼水提物还可提高肝糖原含量至(17.84±4.52) mg/g(p<0.01),稳定血糖(9.24±1.17) mmol/L(p<0.05),降低BUN含量至(7.92±0.57) mmol/L(p<0.05),降低血乳酸含量至(3.76±0.41) mmol/L(p<0.01)。海蛾鱼水提物不具有明显的体外抗氧化作用,而醇提物不具有显著的抗疲劳作用。两种提取物可互补,使得海蛾鱼提取物具有开发成相应功能营养补充剂的潜力。     

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.     

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.     

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.     

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.