紫外线降低片猪肉表面微生物研究

紫外线可以杀灭各种微生物,通过设计的紫外线杀菌器,在线研究不同条件下,紫外线的杀菌效果。得出片猪肉表面干燥、照射距离短、照射时间长、照射功率大,杀菌的效果好,并且对金黄色葡萄球菌的致死效果明显。同时也阐述了紫外线照射杀菌不属于"辐照"的范畴。     

小油坊黄曲霉毒素B_1紫外光降解技术模拟及脱毒效果研究

模拟小油坊黄曲霉毒素B_1(AFB_1)紫外线降解技术机理,研究不同紫外照射强度对不同AFB_1含量花生油的脱毒效果。结果表明:随着紫外照射时间的增加,花生油中AFB_1的含量呈逐渐降低趋势,且在1 600μW/cm~2紫外照度下可将高浓度AFB_1于10 min内降解至国家标准限量以下;在紫外照度800~1 600μW/cm~2范围内,每增加400μW/cm~2照度,各浓度AFB_1降至安全范围所需辐照时间可减少一半;在高紫外照度下,AFB_1降解效果与花生油中AFB_1含量大小无显著关联;对于小油坊使用紫外光降解设备对花生油进行AFB_1脱除处理的,要根据所用设备实际照射强度选择合适照射时间。     

紫外线结合生物源膜基抑菌剂保鲜肉鸡技术

研究了紫外线、生物源膜基抑菌剂及两者结合处理,对冰鲜鸡保鲜中细菌的消长,及TVB-N值等理化指标的影响,辅以感官评价冰鲜鸡的保鲜效果。实验结果表明冰鲜鸡表面主要微生物是革兰阴性菌;采用5.0 mW/cm~2强度的UV处理可降低细菌菌落总数约为0.60 lg cfu/cm~2,对鸡肉的感官、理化指标无显著影响;生物源膜基抑菌剂可抑制细菌总数,并能延缓蛋白质腐败和脂肪酸败;UV辅助生物源膜基抑菌剂的处理可显著提高冰鲜鸡保鲜效果,4℃保藏8 d,细菌菌落总数约为105 cfu/cm~2,TVB-N值仅为11.85 mg/100 g。细菌菌落总数与鸡肉pH值、TVB-N值、TBARS值、感官评分成高度相关;建立紫外线结合生物源膜基抑菌剂处理冰鲜鸡后,菌落总数与保鲜时间的一元线性回归模型lgY=2.772+0.296X,相关系数r=0.98,P0.01;感官评分与保鲜时间一元线性回归模型:Y=99.60-4.65X,相关系数r=0.99,P0.01。两模型结合可以较好地预测冰鲜鸡的保质期为10 d。     

大肠杆菌射频加热杀菌效果及动力学模型拟合

为研究射频加热杀菌效果及微生物致死动力学。选取大肠杆菌为试验菌株,研究极板间距和菌悬液电导率对加热速度及杀菌效果的影响。选取4种常见的模型,即一级动力学、Weibull、Dose-response和Log-Logistic模型对大肠杆菌射频加热失活曲线进行动力学模型拟合。结果表明:极板间距和电导率影响射频加热速度,极板间距越大升温速度越慢,杀灭微生物所需时间越长,当电导率接近1 000μs/cm时,升温速度最快。在极板间距115 mm,电导率1 083μs/cm的条件下,加热90 s,大肠杆菌致死率即可达100%。大肠杆菌的失活动力学曲线基本呈倒"S"型,不符合一级反应动力学模型。Weibull、Log-Logistic和Dose-response模型都能较好地拟合射频杀菌失活曲线。通过对模型的拟合评价参数,即精确因子Af、偏差因子Bf、根平均方差RMSE和决定系数R2的比较,确定Log-Logistic模型拟合效果最好。     

淀粉、脂肪、蛋白质和NaCl成分对气态ClO2杀菌效果的影响

分别检测了几种食源性微生物革兰氏阴性菌、革兰氏阳性菌、酵母菌、霉菌孢子以及细菌芽孢,在相对湿度为90%和0.08mg/L气态ClO2氛围下的敏感性。结果表明:通过气态ClO2处理,5种微生物平均减量0.1～3.5lg(CFU/cm2),5种微生物对气态ClO2的抗性均呈逐渐增强。研究了食物中淀粉、脂肪、蛋白质和NaCl对气态ClO2杀菌效果的影响。结果表明:可溶性淀粉和NaCl均对ClO2的杀菌效率没有显著影响;但琼脂中的黄油、玉米油或乳清蛋白几乎消除了ClO2的杀菌作用。气态ClO2处理的玉米油水乳液中,过氧化值显著增加,表明形成了一级氧化产物。同样,用ClO2处理增加乳清蛋白中的羰基含量,并诱导—SH基团转变为—S—S—基团。结果表明,气态的ClO2对于富含碳水化合物的食物将是一种高效的强氧化杀菌剂,但对高蛋白和脂肪类食物的杀菌效果有限。     

超声波紫外线协同杀菌技术在饮用天然水除菌中的应用研究

研究了超声紫外协同杀菌的饮用天然水杀菌工艺,将超声波紫外线灭菌器应用于山泉水处理中,经过近1年运行。得出最优超声波-紫外线协同杀菌条件为:超声频率20 k Hz,功率500 W;紫外线照射剂量30 m J/cm2,杀菌时间10 s。超声波紫外线杀菌器对水源水有很明显的杀菌效果。将超声波紫外线协同杀菌与臭氧杀菌技术联合使用与单一臭氧杀菌进行比较,协同杀菌技术使用臭氧浓度0.10 mg/L时杀菌效果优于单一0.30 mg/L臭氧杀菌效果,且溴酸盐浓度低于0.005 mg/L,符合国家标准。超声波紫外线协同低浓度臭氧的饮用水杀菌技术可替代单一的臭氧杀菌技术,既能达到杀菌效果,又可降低溴酸盐风险,确保产品的高品质。     

脉冲强光对黄曲霉菌孢子的杀菌效果、微观结构及动力学的影响

脉冲强光是一种新兴的非热杀菌技术。为研究和预测脉冲强光对黄曲霉菌孢子的杀菌作用,在强度2.86,1.60,1.08,0.93 W/cm2脉冲强光下对固体培养基中黄曲霉菌孢子处理1~60 s,并对处理前、后孢子的微观形态进行扫描电镜分析。运用Log-linear模型、Weibull模型和Weibull+tail模型对杀菌致死曲线进行动力学分析。研究表明,随着照射强度增加和时间的延长,脉冲强光对黄曲霉菌孢子的杀菌效果增强。初始菌落数为5.15 lg(CFU/mL)的孢子在2.86 W/cm2下处理19 s可被全部杀死。电镜照片显示脉冲强光处理后孢子细胞结构崩溃。Weibull模型和Weibull+tail模型较Log-linear模型能更好地拟合脉冲强光处理黄曲霉菌孢子的杀菌曲线(R2>0.95)。其中Weibull+tail模型能更加精确地拟合杀菌动力学过程(R2=0.9727)。     

蓝光对阪崎肠杆菌的杀菌及机制研究

本文以食源性致病菌阪崎肠杆菌为对象,研究了医学领域抗细菌感染蓝光的杀菌作用,并首次对其杀菌机制进行了探究。结果表明,当蓝光剂量大于30 J/cm~2时,对阪崎肠杆菌具有显著杀菌作用,照射剂量达240 J/cm~2时,杀菌率超过8 log 10 CFU。亚致死剂量(0～30 J/cm~2)蓝光照射下,单线态氧(~1O_2)探针SOSG开始出现绿色荧光信号,显示细胞内1O2涌现并造成细胞外壁微小孔洞;活性氧物质(ROS)也迅速产生并逐渐增大至5 a.u.;随后脂质氧化标志物丙二醛(MDA)逐渐增加,显示细胞内产生脂质氧化。上述胞内物质变化导致细胞外膜受损,30 J/cm~2蓝光下细胞外膜渗透性增加了48.96%;此外脂肪酰基谱测定揭示,不饱和脂肪酸C18:2,C16:1和C18:1含量减少并逐渐消失,很可能是细胞外膜损伤的重要原因之一。本研究确证了蓝光下细菌胞内~1O_2、ROS及脂质氧化物的动态变化,更重要是的,揭示了细胞外膜损伤是蓝光杀菌的重要方式之一,因为细菌脂质尤其是不饱和脂肪酸是蓝光杀菌重要靶标,本研究将有助于蓝光杀菌机制的深入探究。     

紫外LED冷光技术对花生油中黄曲霉毒素B1降解效果的研究

以10种黄曲霉毒素B1(AFB_1)含量不同的花生油为样品,采用紫外LED冷光照射花生油,探究紫外LED冷光技术对花生油中AFB_1的降解效果。结果表明:紫外LED冷光照射能有效降低花生油中AFB_1的含量,随着紫外照射时间的延长,花生油中AFB_1含量呈逐渐降低的趋势;当样品中AFB_1含量小于等于650μg/kg,紫外LED冷光照射时间120 s,可达到国家标准要求的花生油中AFB_1含量不超过20μg/kg的要求;而当样品中AFB_1含量大于650μg/kg,需延长其照射时间(样品3照射时间1 200 s),才可达到国家标准要求的花生油中AFB_1含量不超过20μg/kg的要求;相同的照射时间(60 s)下,在3 500～450μW/cm2的照射强度下,随照射强度的降低AFB_1降解率降低。花生油经紫外LED冷光照射后,其酸价、过氧化值没有显著的变化。     

紫外光照射降解水中吡虫啉和啶虫脒的研究

本文研究了紫外光照射技术对水模拟体系中吡虫啉和啶虫脒的降解作用,探讨了照射时间、紫外光强度、水模拟体系pH值和农药初始浓度等因素对降解效果的影响。结果表明,紫外光照射可有效降解水模拟体系中的吡虫啉和啶虫脒,且吡虫啉的降解效果优于啶虫脒。在本实验研究条件下,照射时间越长,紫外光强度越大,吡虫啉和啶虫脒的降解率越高;农药初始浓度越低,在相同照射时间下,吡虫啉和啶虫脒的降解率越高;中性和碱性的水模拟体系更利于啶虫脒的降解。采用紫外光强度为650μW/cm2的短波紫外光照射水体系30 min(pH 6,吡虫啉和啶虫脒初始浓度均为0.2μg/mL),吡虫啉和啶虫脒的降解率达到最大,分别为100%和46.30%。动力学研究表明,水模拟体系中吡虫啉和啶虫脒紫外光降解过程符合一级动力学模型(R2≥0.95)。     

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.