压缩饼干硬度临界值的确定以及加速试验条件下硬度的变化规律

压缩饼干是一种长货架期食品,理化指标和感官指标变化缓慢。为了阐明压缩饼干在贮藏过程中硬度变化规律,通常采用加速试验的方法。首先在50℃条件下采用感官可接受性评价和WHA(Weibull Hazard Analysis,威布尔危险分析)方法确定出压缩饼干硬度的感官可接受终点值以及以硬度作为指标的货架寿命预测模型。其次,分别将压缩饼干贮藏在40、60℃和70℃下进行加速试验,研究样品硬度变化与温度和贮藏时间之间的关系。结果表明:压缩饼干硬度的可接受临界值为290～330N;温度的增高明显地加快了压缩饼干变硬,温度越高压缩饼干达到硬度终点的时间越短。继续贮藏,硬度在一定范围内波动。     

能量棒贮藏期稳定性及其货架期预测

对能量棒的贮藏稳定性进行了研究。测定了产品常温(25℃)下的水分活度和菌落总数、色差、酸价及过氧化值的变化,选取37、45、55、65℃4个温度进行加速试验,测定了加速贮藏过程中产品色差、酸价及过氧化值的变化,以感官实验确定产品可接受终点,依据颜色亮度L值变化的二级动力学原理,对L值的变化进行回归分析,预测产品货架期。结果表明:能量棒贮藏期间主要的品质劣变为非酶褐变引起的颜色变化,温度越高褐变速度越快,以颜色亮度L为指标建立预测模型,其Lnk-1/T预测方程为Lnk=-15244/T+40.729,对常温25℃反应速率的预测误差为1.1%。     

自热菜肴竹笋鸡肉的品质变化及货架期预测

为探究自热菜肴贮藏过程中品质变化并对其货架期进行预测,该研究以自热菜肴竹笋鸡肉为研究对象,以色泽、质构、酸价、过氧化值和丙二醛为评价指标,利用恒温加速破坏性实验,研究了不同贮藏温度下（52、62 ℃）自热菜肴竹笋鸡肉品质的变化,并预测出竹笋鸡肉的货架期。结果表明贮藏温度越高,自热菜肴竹笋鸡肉品质劣变越快;在贮藏温度62 ℃下,贮藏84 d和0 d相比,竹笋根部硬度值和竹笋尖部硬度值降幅分别为74.50%和70.31%;在贮藏温度为52 ℃下,贮藏112 d和0 d相比,竹笋根部和尖部硬度值降幅分别为67.37%和60.87%;52 ℃贮藏条件下竹笋鸡肉的感官评分在112 d降至62.6分,贮藏温度为62 ℃在84 d为52.8分;总体上自热菜肴竹笋鸡肉在贮藏前期各类指标变化较快,随着贮藏时间的进一步延长其各项指标变化变缓。根据贮藏期间测定指标与感官评分之间相关关系,并通过货架期预测模型得出25 ℃下的货架期为714 d。     

富含花色苷的压缩饼干在贮藏中货架期预测模型研究

本文以添加花色苷的压缩饼干为对象,测定压缩饼干的理化指标,采用加速实验法预测产品的货架期。研究产品在加速温度实验条件下DPPH自由基清除率、酸价、过氧化值和色泽随贮藏时间的变化,基于Arrhenius模型对反应速率常数和贮藏温度之间的关系进行拟合,确定较优模型,进而对货架期进行预测。结果表明:压缩饼干的脂肪和碳水化合物含量较高,能量密度高达5.74kcal/g。在一定温度条件下,随着贮藏时间的延长,DPPH自由基清除率下降(p0.05),色差值L*降低(p0.05),酸价升高(p0.05),过氧化值无明显变化规律。酸价和L*在贮藏中的变化规律遵循零级反应动力学,综合酸价和L*的货架期预测分析,选用L*的非线性拟合方程为该压缩饼干的货架期预测模型。压缩饼干的活化能为61.99 k J/mol,25℃下预测货架期为517.89 d。     

山核桃基于温度变化的贮藏寿命预测

研究不同温度(2、12、22、32℃)贮藏过程中山核桃过氧化值、酸价及感官品质随贮存时间的变化规律及其动力学特性,在Arrhenius 动力学方程基础上,建立过氧化值和酸价与贮藏时间、贮藏温度之间的动力学模型,以预测和控制贮藏过程中山核桃的品质变化。结果表明,新鲜山核桃的过氧化值和酸价随着贮藏时间的延 长而增加,且随着贮藏温度的升高而增加迅速,其感官品质指标随着贮藏时间的延长而下降,且随着贮藏温度的升高而迅速下降。一级化学反应模型和Arrhenius 方程对过氧化值和酸价变化具有很高的拟合精度,建立的山核桃货架期预测值准确率达到± 10% 以内,可根据过氧化值、酸价在2～32℃范围内,对山核桃的氧化货架寿命进行预测。     

保温贮藏对煎制肉饼品质特性的影响

试验模拟快餐店生产模式,将肉饼煎制后采用65℃保温贮藏,跟踪检测其品质变化情况,探究保温贮藏对煎制肉饼品质的影响。试验将煎制好的猪肉饼于65℃条件下保温贮藏,考察保温第0、30、60、90、120、180分钟时肉饼的pH值、硫代巴比妥酸反应物(thiobarbituric acid resctive subastances,TBARS)、挥发性盐基总氮值(total volatile basic nitrogen,TVB-N)、过氧化值、感官评价等指标的变化,确定肉饼可接受的最长保鲜时间。试验结果表明:在保温贮藏过程中,煎制肉饼色pH值、TBARS值、TVB-N值、过氧化值、酸价等不断上升,L*、a*和感官评分不断下降。前90 min内,TVB-N值、TBARS值、酸价值、过氧化值、感官评价变化不显著(P0.05),90 min后与前期相比差异显著(P0.05)且感官评价为不可接受。因此,在65℃保温贮藏条件下,煎制肉饼的最长保鲜时间是90 min。     

棕榈油复合火锅底料不同贮藏温度品质变化及货架期预测

以新研发的棕榈油复合火锅底料为研究对象,对5,25,37℃贮藏条件下复合火锅底料的感官品质、过氧化值、酸价、色差、细菌总数、大肠菌群、主要风味物质的变化规律进行分析,并在Arrhenius动力学方程基础上,建立了感官品质、过氧化值和酸价与贮藏温度之间的动力学模型。研究结果表明:以酸价作为指标建立动力学模型预测复合火锅底料的货架期,模型的活化能(E)和回归系数(K_0)分别为15.06kJ/mol和2.08。由此推导出酸价变化速率常数与贮藏温度(T)之间的方程K=2.08exp(-15060/RT),通过该方程及酸价判断终点值4.0mg/g,即可预测一定贮藏温度下棕榈油复合火锅底料的货架期。     

动力学模型预测速冻饺子货架寿命

研究不同温度下贮藏过程中速冻饺子的感官性质、酸价、过氧化值随贮藏时间的变化规律,确定酸价和过氧化值是引起速冻饺子在贮藏过程中品质变化的重要表征.并建立酸价、过氧化值与贮藏时间、贮藏温度之间的动力学模型,以预测速冻饺子在贮藏过程中的品质变化和货架期.结果表明,一级化学反应动力学模型对酸价、过氧化值变化具有较高的拟合精度(R2＞0.9),酸价和过氧化值变化的动力学模型分别为A=0.32e(1.284 0×106e-38.74×103/RT-0.001 1)t和A=0.62e4.236 5×105e-35.84×103/RTt.     

复合营养粉贮藏期稳定性与货架期预测研究

对以小麦胚芽、低值鱼为主原料,经挤压膨化工艺制备复合营养粉的贮藏稳定性进行了研究:选取50、60、70℃三个温度进行加速实验,测定了产品常温(25℃)下的水分活度,以加速贮藏过程中产品色差、酸价、过氧化值及微生物的变化为指标,结合产品感官评定,依据油脂一级化学动力学原理,对过氧化值变化进行回归分析,预测产品货架期。研究表明,产品在加速贮藏中色泽向土黄色转变,产品最终保藏水分为5%,其LnKa-1/T线性方程为:y=-0.52012x+13.169。     

香菇牛肉酱贮藏过程中品质变化及动力学模型构建

以香菇牛肉酱为对象,分析不同贮藏温度下香菇牛肉酱的感官品质、酸价和过氧化值的变化规律,在Arrhenius动力学方程的基础上,建立感官品质、酸价和过氧化值与贮藏温度之间的动力学模型。结果表明:随着贮藏时间的延长,香菇牛肉酱的感官品质逐渐下降,酸价和过氧化值逐渐上升。将酸价作为指标,建立动力学模型可预测香菇牛肉酱的货架期,模型的活化能(E_a)和回归系数(K_0)分别为23 627.556 6 J/mol和48.623 2。经验证,此动力学模型可快速预测贮藏温度在25℃和35℃贮藏条件下香菇牛肉酱的货架期,误差在±5.0%以内。     

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.