竹叶抗氧化物对冷藏三文鱼片新鲜度的影响

研究竹叶抗氧化物对三文鱼贮藏过程中品质变化的影响。将三文鱼片浸渍于0.2%竹叶抗氧化物溶液中,0℃条件下贮藏。以感官评定、菌落总数、挥发性盐基氮(TVB-N)、p H值、K值及TBA为评价指标,研究竹叶抗氧化物对冷藏三文鱼的保鲜效果。结果显示:在贮藏期间,三文鱼片的感官评分值呈下降趋势;菌落总数、挥发性盐基氮(TVB-N)及K值均随时间的延长呈上升趋势;TBA虽规律性不强,但大体呈上升趋势;p H值呈先降低后上升的趋势。浸泡0.2%竹叶抗氧化物的三文鱼片各项评价指标均低于对照组,感官评分值优于空白对照组,可使三文鱼片的冷藏货架期延长2 d~4 d。     

0℃冷藏三文鱼片新鲜度综合评价

对0℃贮藏的三文鱼片的理化指标和微生物指标【包括挥发性盐基氮(TVB-N)值、2-硫代巴比妥酸(TBA)值、p H值、色差值、菌落总数】进行定期测定,用电子鼻分析其挥发性气味组分(包括主成分分析、负荷加载分析以及线性判别分析);结合感官评价,探究冷藏条件下三文鱼片新鲜度的变化规律。试验结果表明:0℃贮藏的三文鱼片的TVB-N值、TBA值、菌落总数都随贮藏时间的延长而增大;p H值先降低后增高;色差值L*值先增加后减小再增加,a*值与b*值与其相反;总色差值则先增加后减小;感官评定分数一直下降。采用电子鼻能很好地区分不同贮藏时间的三文鱼片,各理化指标间有很好的对应关系(P0.01)。     

软包装材料对鲜羊肉品质的影响

以新鲜羊肉为原料,研究真空包装条件下,4种包装材料对鲜羊肉贮藏过程中综合感官指标、色泽、菌落总数、挥发性盐基氮等代表品质因素的关键性技术指标的影响.结果表明,在包装材料厚度相同、贮藏温度相同的条件下,PA/CPP包装组在感官品质明显优于其它3种包装组,菌落总数、pH值、挥发性盐基氮值、汁液流失率均低于其它3组包装,色差仪数值a*较其它3组包装高;4种包装材料的保鲜效果依次为:PA/CPP>OPP/CPP>PET/AL/PE>PA/PE.     

冰温保鲜对牛肉品质特性影响的研究

为探讨冰温保鲜对牛肉品质特性的影响,设定-1℃冰温贮藏,并以4℃冷藏为对照,测定肉样的色差（a*值、L*值）、pH值、汁液流出率、蒸煮损失率、挥发性盐基氮、剪切力和菌落总数,并对肉品进行感官评分。结果显示：-1℃冰温组的色差a*值和L*值、蒸煮损失率、剪切力和感官评分整体上均高于4℃冷藏组,在销售过程中更容易被消费者接受;-1℃冰温组的pH值、汁液流出率、挥发性盐基氮和菌落总数整体上均低于4℃冷藏组,可将肉品的货架期有效延长3 d。因此,冰温贮藏可有效保持肉品的品质,具有明显的保鲜效果。     

不同保鲜剂对冷却牛霖肉保鲜效果的研究

通过实验探究茶多酚、复合有机酸和环脂肽3种保鲜剂对冷却牛霖肉的保鲜效果,在贮藏期间对色差、挥发性盐基氮、菌落总数和感官评分等指标进行测定,以筛选对冷却牛霖肉有较好保鲜效果的保鲜剂。结果表明,在贮藏期间内,茶多酚组、复合有机酸组和环脂肽组的挥发性盐基氮含量和菌落总数低于对照组(无保鲜剂处理),色差和感官评价高于对照组。其中,第10天,环脂肽组a^*值为10.46,挥发性盐基氮含量为11.25 mg/100 g,菌落总数为5.87 lgCFU·g^-1,均为最优;在感官评价方面,环脂肽组感官评分显著高于茶多酚组和复合有机酸组(P <0.05)。环脂肽对冷却牛霖肉具有较好的保鲜效果,可作为天然保鲜剂应用于冷却牛霖肉的贮藏。     

冷藏物流过程中温度变化对三文鱼品质的影响

为了研究冷藏物流过程中温度变化对三文鱼品质的影响,实验模拟4种不同的物流过程,测定三文鱼肉的感官、pH值、色差、失重率、TVB-N、菌落总数以及K值。结果表明:三文鱼肉的品质受冷藏物流过程中温度变化影响显著,贮运及销售过程始终在0℃能够使三文鱼肉保持较好的品质;贮运过程中经历温度变化的三文鱼肉在销售、消费期间品质显著下降。由此得出,冷藏物流过程中温度变化及变化频率对三文鱼肉品质的影响很大,因此应尽量避免贮运期间的温度波动。     

紫苏叶水提物对调理脆肉鲩鱼片冷藏过程中品质的影响

为研究紫苏叶水提物对脆肉鲩鱼片冷藏过程中品质的影响,将脆肉鲩鱼片置于紫苏叶水提物中浸泡腌制,通过对脆肉鲩生鱼片和熟鱼片在冷藏过程中的质构、硫代巴比妥酸(TBA)、挥发性盐基氮(TVB-N)、菌落总数、感官评定等变化规律进行分析。结果表明:紫苏叶水提物对脆肉鲩鱼片贮藏过程中的TBA值、TVB-N值、菌落总数增长有显著抑制作用(p0.05),其中,生鱼片冷藏12 d TBA值为0.167 mg/100 g;熟鱼片冷藏过程TVB-N值均小于国标规定的二级鲜度;贮藏12 d生鱼片菌落总数为6.17 log CFU/g,达到水产品规定的货架期终点;冷藏过程感官评分缓慢下降,失重率不断升高;质构分析表明,鱼片硬度和咀嚼性均呈下降趋势。结论:紫苏叶水提物能有效抑制脆肉鲩鱼片冷藏过程中的脂肪氧化和腐败微生物的生长,明显延缓鱼片的腐败变质。     

不同冷藏温度对白斑狗鱼品质变化的影响

以白斑狗鱼为研究对象,在-4、0、4℃3种贮藏温度下,对其物理(质构、失重率、色差值、持水率),化学(挥发性盐基氮值、pH值、硫代巴比妥酸值、肌原纤维蛋白及肌浆蛋白含量),感官及微生物指标进行测定,从而揭示其品质变化规律。结果表明:随着贮藏温度的升高及贮藏时间的延长,白斑狗鱼的各项指标都呈现出不同程度的变化。样品的失重率、色差值、挥发性盐基氮值、硫代巴比妥酸值及菌落总数指标随着储藏温度的上升而增加且温度越高增加速率越大;样品的质构、持水率、肌原纤维蛋白及肌浆蛋白含量及感官品质理化指标呈现下降的趋势;样品的p H值呈现出先下降后升高的变化特性。以上白斑狗鱼各项指标值可为今后冷水鱼的冷藏和冷链运输提供理论参考。     

冬凌草甲素/壳聚糖复合膜对冰鲜鸡胸肉的保鲜效果

制备了冬凌草甲素/壳聚糖(OR-CS)复合膜,考察了其对冰鲜鸡胸肉的保鲜效果。将复合膜覆盖于鸡胸肉表面,复合膜外再包被一层保鲜膜,4℃贮藏,检测贮藏过程中鸡胸肉的pH、色度、保水性、挥发性盐基氮(TVB-N值)、菌落总数、感官质量的变化。试验结果表明,通过OR-CS复合膜处理的冰鲜鸡胸肉能显著延缓贮藏期间的pH值、菌落总数、TVB-N含量和汁液损失率的上升。OR-CS复合膜包装组使冰鲜鸡胸肉的货架期由4 d(对照组)延长至9 d;此外,通过色差测定和感官评定,OR-CS包装组可以更好地保持冰鲜鸡胸肉的品质和色泽,在贮藏期间能有效延缓肉表面亮度的减弱,显著改善了肉的颜色、气味、黏度和弹性。     

可降解包装材料对冷鲜驼肉品质的影响

以聚(L-乳酸)/聚碳酸亚丙酯/聚己二酸对苯二甲酸丁二酯(PLLA/PPC/PBAT)可降解薄膜为试验组,以尼龙/聚乙烯(PA/PE)薄膜及无包装作为对照组,分别对新鲜骆驼肉进行真空包装后,在(2~4)℃贮藏期间对其菌落总数、挥发性盐基氮、硫代巴比妥酸、p H、系水力、剪切力、色差等指标进行了检测分析。结果表明,PLLA/PPC/PBAT可降解薄膜包装组的新鲜骆驼肉的菌落总数、p H值、挥发性盐基氮、硫代巴比妥酸值均低于其他2组,系水力、色泽、剪切力指标优于其他2组。因此,PLLA/PPC/PBAT可降解薄膜用于骆驼肉的冷鲜包装,可有效延缓骆驼肉的腐败变质,提高肉的品质。     

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.     

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.     

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.