复合天然防腐保鲜液对Mozzarella干酪贮藏期的影响

采用无盐渍新工艺法制作部分脱脂Mozzarella干酪,使用复合天然防腐保鲜液(0.69%茶多酚+0.013%Nisin和溶菌酶(1∶1)+0.0043%那他霉素)对成熟干酪样品进行浸泡处理,并在4℃冷藏,通过每间隔7d测定干酪不同贮藏时间的水分含量、pH、滴定酸度、可溶性氮含量(SN)、SDS-凝胶电泳、未融化干酪质构特性、融化干酪功能特性、微生物指标和感官评定等一系列指标的变化,评定复合天然防腐保鲜液对Mozzarella干酪贮藏效果的影响。实验结果表明:浸泡处理组4℃冷藏49d时的贮藏效果与对照组28d时相当,复合天然防腐保鲜液的使用可有效延长Mozzarella干酪的贮藏期。     

不同气调贮藏对Mozzarella干酪功能特性的影响

采用无盐渍新工艺制得部分脱脂Mozzarella干酪,以PVDC为包装材料,分别采用50%CO2和50%N2,75%CO2和25%N2,100%CO2对干酪进行气调包装,以真空包装为对照组(CK),在4℃下进行冷藏,对不同气调贮藏条件下的Mozzarella的理化指标以及功能特性进行了测定.结果表明:各气调组水分含量、pH值、硬度、弹性均显著高于时照组(P<0.05),各气调组干酪的pH值为4.6 SN和质量分数为12%的TCA SN均显著低于对照组(P<0.05),各气调组与对照组相比,凝聚性、融化性无变化.b值逐步下降.各气调组保持了干酪特有的功能特性,感官评分均高于时照组.质量分数为75%的CO2和质量分数25%的N2能有效地延长Mozzarella干酪贮藏期.     

不同包装材料对乌龙头贮藏品质的影响

目的 研究不同包装材料对乌龙头贮藏品质的影响。方法 以‘长白’品种乌龙头为材料, 采用不同包装材料[普通聚乙烯(polyethylene, PE)食品袋(对照)、PE气调保鲜袋、聚氯乙烯(polyvinyl chloride, PVC)保鲜袋、PVC硅窗保鲜袋]对乌龙头进行贮藏, (1±1)℃下贮藏15 d, 研究包装材料对乌龙头感官品质、腐烂指数、呼吸强度、失重率、叶绿素含量、维生素C (vitamin C, VC)含量、粗纤维含量、丙二醛(malonaldehyde, MDA)含量、过氧化物酶(peroxidase, POD)活性和多酚氧化酶(polyphenol oxidase, PPO)活性等相关生理指标的影响。结果 3种保鲜袋均可以显著延长乌龙头贮藏期, 其中PVC硅窗保鲜袋的保鲜效果最佳, 与对照(PE食品袋)相比, 呼吸高峰出现推迟3 d。贮藏至12 d时, PVC硅窗保鲜袋的叶绿素含量和维生素C含量分别是对照的2.1倍和1.9倍, 与对照相比, 感官评分提高29.1%, 腐烂指数、失重率、粗纤维含量和MDA含量分别下降86.4%、50.3%、45.8%和42.4%, POD和PPO含量分别下降了37.5%和52.7%。结论 PVC硅窗保鲜袋可显著抑制乌龙头贮藏期间感官品质和叶绿素含量的下降, 抑制其腐烂, 贮藏期延长3 d。     

包装材料对鲜切西兰花贮藏品质的影响

为了延长西兰花货架期,采用4 种膜包装鲜切西兰花,研究其在贮藏期品质的变化。将鲜切西兰花分别用 聚偏二氯乙烯（polyvinylidene chloride,PVDC）、聚乙烯（polyethlene,PE）、低密度PE、聚甲基戊烯4 种膜 包装,贮藏期间每3 d测定西兰花生理生化指标。结果表明：随着贮藏时间的延长,西兰花的品质逐渐下降;贮 藏12 d时,采用PVDC膜包装的西兰花的VC含量、可溶性固形物质量分数、过氧化物酶活力最高,质量损失率、 呼吸强度、丙二醛含量及多酚氧化酶活力最低;但PVDC膜在叶绿素保持及提高超氧化物歧化酶活力方面不如PE 膜。综合分析得出,鲜切西兰花贮藏0～9 d,PVDC膜保鲜效果最好;贮藏9～12 d,PE膜包装的商品性最高。     

不同包装材料对大米恒温恒湿贮藏品质的影响

分别采用聚偏二氯乙烯(PVDC)和聚乙烯/尼龙/聚丙烯(PE/PP/PA)包装材料对大米进行包装,在恒温恒湿(温度37℃,湿度70%)贮藏条件下,研究不同包装材料对大米贮藏品质的影响。试验结果表明,这两种包装材料的大米水分均有所降低,蒸煮品质下降,淀粉酶活力和脂肪酶活力呈先升高后降低的趋势,脂肪酸值升高;PVDC包装材料组各项指标变化程度均低于PE/PP/PA包装材料组。在恒温恒湿贮藏条件下,PVDC包装材料能更好地延长大米保质期。     

包装材料结合活性包装对荞麦半干面常温货架期及品质的影响

为了延长荞麦半干面的常温货架期,以聚偏二氯乙烯(PVDC)和聚乙烯(PE)为包装材料,采用不同活性包装方式(脱氧包装和脱氧结合酒精缓释包装)对其进行包装处理。考察脱氧剂、酒精缓释剂和不同包装材料对荞麦半干面货架期和储藏期间品质的影响。测定荞麦半干面在储藏期间菌落总数、酸度值、p H值、质构特性、感官品质和包装袋内顶空氧气含量、顶空酒精浓度的变化。结果表明:储藏期间菌落总数整体呈现上升趋势,脱氧结合酒精缓释包装协同抑制微生物生长。储藏9 d后,脱氧结合酒精缓释包装的面条菌落总数均未超过106cfu/g,同时显著抑制了理化品质的劣变(P0.05);脱氧剂的吸氧量越大,24 h内除氧速率越快,抑菌效果越显著;相同活性包装方式下,与PE包装材料相比,PVDC包装材料能增强其延长荞麦半干面常温货架期的作用效果。与其他包装方式相比,脱氧(200 m L)结合酒精缓释PVDC包装将荞麦半干面货架期延长至16 d,并且维持了面条储藏期间的品质。     

对比PE膜与微孔膜对冷藏青萝卜品质的影响

为探讨包装材料对青萝卜采后贮藏品质的影响,以卫青萝卜为试材,在(2.0±0.5)℃冷藏条件下,分别采用PE膜、微孔膜对卫青萝卜进行包装,比较了卫青萝卜主要理化及感官指标变化。结果表明:贮藏期间PE膜组和微孔膜组的VC、酸度、可溶性固形物、亚硝酸盐以及还原糖含量变化基本一致,均为先上升后下降。微孔膜组的VC含量、酸度、可溶性固形物含量和失重率均比PE组高;PE组的淀粉酶活性、还原糖和亚硝酸盐含量高于微孔膜组;微孔膜组的质构指标和感官指标优于PE组;二者色差指标差异不明显。微孔膜包装处理的卫青萝卜最佳食用期为5周,最佳贮藏期为11周。PE组包装处理的卫青萝卜品质随着贮藏时间的延长而逐渐下降,最佳贮藏期为9周。微孔膜组的卫青萝卜品质更佳。     

包装材料与乙烯吸收剂,1-MCP组合处理对延长银白杏贮藏期的影响

探讨了延长银白杏的贮藏期的方法。首先对八成熟的银白杏进行1.0μL/m L 1-甲基环丙烯熏蒸处理,然后用不同保鲜袋(PVC袋,PE袋,PE打孔袋)与乙烯吸收剂组合处理,测定在4℃条件下贮藏期间呼吸强度、理化和感官指标的变化。试验结果表明,在7周的贮藏期中,乙烯吸收剂对银白杏果实的保鲜效果无有益影响。在不加乙烯吸收剂的情况下,与其他两种包装和冷藏对照相比,贮藏两周后PVC袋内O2和CO2含量分别保持在3%和3%~5%,达到最佳的气调贮藏条件,使杏果实的呼吸高峰推迟1周,且呼吸强度明显降低;PVC包装在贮藏期内显著延缓果皮、果肉硬度和可滴定酸的下降;3种包装对VC和可溶性固形物含量均无显著影响。经1-甲基环丙烯熏蒸处理,用PVC包装使银白杏的贮藏期于4℃延长至6周,达到较好的贮藏保鲜效果。     

不同包装膜对生菜贮藏期品质的影响

以生菜为实验材料,研究在(4±1)℃贮藏条件下,无膜包装(CK)、聚氯乙烯(PVC)包装、聚乙烯(PE)包装、微孔膜(MF)包装对其贮藏期品质的影响。定期测定生菜在贮藏期间Vc含量、叶绿素含量、失重率、可溶性固形物含量、腐烂指数、感官综合评价等指标的变化情况,结果表明:与对照组相比,不同薄膜包装材料对生菜贮藏均有不同程度的保鲜作用;微孔膜在抑制Vc的氧化、水分流失、腐烂、叶绿素分解、可溶性固形物流失方面优于PVC膜和PE膜。微孔膜因其安全无毒无污染,又具有强延展性、耐热耐寒性,可作为生菜贮藏的保鲜材料。     

PA/PE复合膜对鲜切莴笋保鲜效果的影响

为了验证尼龙-聚乙烯（polyamide/polyethylene,PA/PE）复合膜对鲜切莴笋的保鲜效果,将新鲜莴笋切片真空包装后在4 ℃条件下冷藏,不加任何包装的鲜切莴笋同样条件下作空白对照。贮藏期间评价菌落总数、色差、pH值、汁液流失率、VC含量、感官等指标。结果PA/PE组贮藏期达24 d,而不加包装的对照组只有4 d。可见对于鲜切莴笋的贮藏,PA/PE复合膜结合真空包装可明显延长其贮藏期。     

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.