海藻酸钠固定化乳酸菌促熟干酪效果的研究

对海藻酸钠固定化乳酸菌促熟干酪的效果进行了研究。结果表明，在干酪粒中添加10^6CFU／g固定化乳酸菌，水溶性氮（WSN）、三氯乙酸氮（TCASN）和磷钨酸氮（PTASN）含量较对照组明显增大；ADV值在添加固定化乳酸菌干酪中成熟初期变化不大，45d后明显增大；感官评定结果表明，干酪粒中添加10^5CFU／g固定化乳酸菌干酪成熟60d时风味和质地较好，可比对照组干酪成熟期缩短30d左右。     

混合型大豆干酪成熟特性的研究

对混合型大豆干酪的成熟特性进行了研究。检测了混合型大豆干酪成熟过程中游离脂肪酸和氨基酸含量的变化,在扫描电镜下观察了不同成熟条件下干酪的微观结构。结果表明,成熟温度对游离脂肪酸含量影响不显著,对游离氨基酸含量影响显著;随着成熟时间的延长,饱和脂肪酸与不饱和脂肪酸含量之比下降,游离氨基酸含量变化较为显著;成熟对混合型大豆干酪的微观结构影响很大,使得干酪质地越来越致密均匀。     

原料乳冷藏时间对牦牛乳硬质干酪理化指标的影响

冷链贮存运输已广泛运用于各大乳制品生产，冷藏时间的长短对原料乳及其制作的干酪理化品质具有重要影响。该研究以冷藏24、48、72 h牦牛乳为原料制作硬质干酪，比较了硬质干酪成熟过程中的理化指标变化规律。结果表明，在0～6个月成熟期中，冷藏24、48、72 h牦牛乳制成的硬质干酪中水分含量、脂肪含量呈现降低趋势，NaCl含量呈现增加趋势。pH值在成熟初期下降，到成熟后期又逐渐升高；pH 4.6可溶性氮、12%三氯乙酸可溶性氮和游离氨基酸总量呈现增加趋势。整个成熟过程中，3组牦牛乳硬质干酪中pH 4.6可溶性氮、12%三氯乙酸可溶性氮以及游离氨基酸总量始终为冷藏72 h组>冷藏48 h组>冷藏24 h组。该研究可为牦牛乳的冷藏及其在干酪加工中的应用提供理论参考。     

凝乳酶对牦牛乳硬质干酪成熟期间蛋白降解的影响

以新鲜牦牛乳为原料,采用小牛皱胃酶、木瓜蛋白酶和微生物凝乳酶制作硬质干酪,探讨凝乳酶种类对牦牛乳硬质干酪成熟期间蛋白质降解的影响。结果表明:三种凝乳酶牦牛乳硬质干酪成熟过程中,不同凝乳酶牦牛乳硬质干酪在成熟期间蛋白质降解能力存在较大差异,总氮(TN)、p H4.6水溶性氮(p H4.6-SN/TN)、12%的三氯乙酸氮(12%TCA-N/TN)、5%磷钨酸氮(5%PTA-N/TN)含量、游离氨基酸均随成熟时间延长不同程度的增加,蛋白氮和酪蛋白氮逐渐降低,多肽氮呈先升高后下降趋势,且微生物凝乳酶降解牦牛乳硬质干酪蛋白能力显著(p0.05)高于木瓜蛋白酶和小牛皱胃酶。     

两种羊奶干酪成熟期间理化和生化特性研究

对硬质、半硬质羊奶干酪成熟90d内理化和生化特性的研究表明:硬质、半硬质羊奶干酪的pH在成熟过程中都呈先减小后增大的趋势,水分含量逐渐降低,盐含量逐渐增大,蛋白质和脂肪含量先增大后减小.在蛋白质降解产物中,pH4.6水溶性氮(WSN-N)、12%三氯乙酸氮(TCA-N)、5%磷钨酸氮(PTA-N),氨基酸态氮(AAN)含量都呈上升趋势.在脂肪降解产物中,ADV值、羰基价和TBA值变大,POV值在干酪成熟过程中上升和下降交替出现.     

成熟温度和时间对半硬质干酪成熟特性影响研究

研究成熟温度和时间对半硬质干酪成熟特性的影响。将干酪分别在4、10、16℃条件下成熟,测定其在90d 内品质变化规律。结果表明,在90d 成熟期内,pH 值先下降后升高,最后趋于稳定;pH4.6 可溶性氮含量和12% 三氯乙酸可溶性氮含量逐渐升高;乳酸菌总数逐渐下降。成熟温度对干酪的感官品质、pH 值、蛋白质的降解和乳酸菌总数影响显著。4℃成熟的干酪,在第90 天时,感官品质达到最好;10℃成熟的干酪,在第45天时,感官品质达到最好;16℃成熟的干酪,感官品质较差。根据感官品质和其他参数的变化规律,确定半硬质干酪的最佳成熟温度为10℃,最佳成熟时间为45d。     

两种乳源切达干酪成熟期间蛋白质降解状况对比

为了了解中国特色水牛乳切达干酪成熟过程中蛋白质降解的情况,以荷斯坦牛乳切达干酪为对照,用凯氏定氮法研究两种干酪的磷钨酸可溶性氮(PTA-SN)、三氯乙酸可溶性氮(TCA-SN)和pH 4.6可溶性氮(pH 4.6-SN)在干酪成熟期间的变化情况.结果表明:在成熟期90 d内,两种切达干酪在成熟过程中PTA-SN、TCA-SN和pH 4.6-SN含量随着成熟时间的延长逐渐增大,且成熟温度越高,增加得越多,最终分别上升了约5％～10％,1％～10％,2％～5％.中国水牛乳切达干酪蛋白降解程度更深.     

基于多元线性回归对Tilsit型干酪成熟期的研究

根据Tilsit干酪加工方法制作生干酪样品,在90 d成熟内测定其总氮、水溶性氮(WSN)、三氯乙酸水溶性氮(TCA-SN)、磷钨酸水溶性氮(PTA-SN)等含量,研究成熟过程中蛋白质水解程度。上述指标,除磷钨酸水溶性氮,其余均与干酪成熟期呈现一定的线性相关性(p<0.05),该多元线性回归模型可以用于鉴定和预测Tilsit型干酪的成熟期。     

瑞士乳杆菌对高达干酪蛋白水解的影响

研究高达干酪在4℃条件下成熟16周过程中瑞士乳杆菌对蛋白水解的影响。制作4个高达干酪样品,2个为对照样品,不添加瑞士乳杆菌;另2个为试验样品,添加瑞士乳杆菌KLDS 1.0432。在干酪成熟过程中每隔一段时间测定pH4.6水溶性氮(SN-pH4.6)、12%三氯乙酸氮(SN-TCA)、5%磷钨酸氮(SN-PTA),并进行SDS凝胶电泳。结果显示:对照样品和试验样品的SN-pH4.6和SDS凝胶电泳没有显著差别,但是试验样品中的SN-TCA和SN-PTA比对照样品高。     

快速成熟契达干酪成熟期间的理化特性变化

对天然契达(Cheddar)干酪快速成熟期间理化特性进行了研究,结果表明,在21 d内,pH值呈下降趋势(P<0.05),在21 d到35 d的成熟中,pH值缓慢增加(P>0.05);Cheddar干酪快速成熟过程中由于蛋白酶和脂肪酶的作用使蛋白发生水解,pH值为4.6醋酸溶液—水溶性氮质量分数、质量分数为12%的三氯乙酸—可溶性氮和游离氨基酸(FAA)的质量分数都呈明显增加趋势(P<0.05);成熟过程中TPA各项指标均有不同程度的变化,硬度和凝聚性呈先下降后增加的趋势,弹性和咀嚼性呈先上升后下降的趋势。     

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.     

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.     

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.     

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.     

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.