不同贮藏温度下两种发酵香肠品质变化及货架期预测模型的建立

对玫瑰低硝半干发酵肠（M）和传统半干发酵肠（P）在3个温度（4、25、35 ℃）贮藏过程中的品质变化进行了评价,并运用动力学和Arrhenius方程建立了两种发酵肠货架期预测模型。研究表明,温度对两组香肠的红度值和质构特性影响较大,在贮藏期间,各贮藏温度下的酸价、挥发性盐基氮（total volatile basic nitrogen,TVB-N）值和菌落总数( total viable count,TVC)随贮藏时间推移而升高,且温度越高变化越快;以TVB-N值和TVC为关键因子建立动力学模型,并结合Arrhenius方程构建两种发酵肠的货架期预测模型,P发酵肠的TVB-N值和TVC预测模型中活化能E_a分别为52.37 kJ/mol和43.39 kJ/mol,指前因子k₀分别为69859734.72、8806494.34;M发酵肠的TVB-N值和TVC预测模型中活化能E_a分别为46.46 kJ/mol和43.53 kJ/mol,指前因子K₀分别为5373553.61和8016399.99。选取4、30 ℃验证模型可靠性,两种发酵肠货架期理论值与实测值的相对误差在11.18%以内,可准确预测4～35 ℃范围内的货架期。此外,在不同贮藏温度下M发酵肠的品质均优于P发酵肠,并具有较长的保质期限。     

不同贮藏温度条件下鲐鱼货架期预测模型的构建

为了探索海上移动运输船上东海鲐鱼新鲜度随温度变化规律及其动力学特性,将鲐鱼贮藏在0、5、10、15 ℃条件下,测定K值、挥发性盐基氮（total volatile base nitrogen,TVB-N）值与菌落总数（total viable count,TVC）,并进行感官评分,研究其货架期预测模型。结果显示,随贮藏时间的延长,鲐鱼的感官品质指标逐渐下降,K值、TVB-N值和TVC均逐渐上升。实验用Arrhenius方程构建了贮藏温度、贮藏时间与K值、TVB-N值和TVC之间的动力学模型,其中,K值变化的活化能（Ea）及速率常数（k0）分别为30.54 kJ/mol和1.54×104;TVB-N变化的Ea及k0分别为41.21 kJ/mol和4.40×105;TVC变化的Ea及k0分别为46.78 kJ/mol 和2.93×106。建立的动力学模型可以在0～15 ℃范围内对鲐鱼的货架期进行准确预测。     

冷却猪肉货架期预测模型建立及验证

建立针对不同贮藏温度下冷却猪肉的货架期预测模型,为猪肉贮藏和物流过程中品质评价、货架期预测提供技术支持。分析了0,2,4,6,8,10℃不同贮藏温度下猪肉的挥发性盐基氮(TVB-N)、pH值、色差(a*)、水分活度(Aw)与感官评定结果的相关性,利用一级反应动力学方程和Arrhenius方程求得TVB-N变化反应的活化能(E0)为87.19 kJ/mol,指前因子(k0)为2.169×1014,速率常数k为2.169×1014e-87190/RT,在此基础上建立了以TVBN为指标的冷却猪肉货架期预测模型。在0,4,8,10℃贮藏条件下对TVB-N预测模型进行验证,相对误差均小于10%,准确度和偏差度均为1.03,在可接受范围内。TVB-N是预测冷却猪肉货架期的有效指标,用其建立的货架期预测模型准确实用。     

不同贮藏温度对暗纹东方鲀水分迁移、质构和色泽的影响及其货架期预测

以暗纹东方鲀为研究对象,实验研究了微冻(-3℃)、冰温(-1℃)、冷藏(4℃)、10℃和15℃条件下鱼肌肉中水分迁移、质构(texture profile analysis,TPA)和色泽的变化规律,以及水分迁移对鱼肉质构和色泽的影响,同时,构建了货架期预测模型。研究结果显示,不同贮藏温度下鱼肉的结合水、不易流动水和自由水的相对含量(p T_(21),p T_(22),p T_(23))随贮藏时间分别呈上升、上升后下降和下降后上升的变化趋势,鱼肌肉中结合水和自由水的弛豫时间(T_(21),T_(23))波动上升,T_(22)对应的不易流动水先上升后下降。总体上,不同温度贮藏组的不易流动水随着贮藏时间向自由水的迁移均较明显。不同温度组p T_(21)和T_(21)对应的结合水对鱼肉的弹性、硬度和白度有较大影响。相关性拟合结果显示菌落总数(total viable count,TVC)、挥发性盐基氮(total volatile base nitrogen,TVB-N)与感官评分的相关性最高(|r| 0. 95,R2 0. 90),并以此建立了货架期预测模型;验证结果表明,结合Arrhenius方程构建的TVC和TVB-N的时间-温度-品质的动力学模型能较准确地预测-3～15℃贮藏暗纹东方鲀的货架期。     

鱼糜制品储藏特性和货架期预测研究

将鱼糜制品（青葱虾米小天妇罗）储藏在不同温度条件下,研究其感官品质、挥发性盐基氮（TVB-N）、硫代巴比妥酸值（TBA）以及菌落总数的变化,建立了鱼糜制品的TVB-N、TBA、菌落总数与储藏温度和储藏时间的Arrhenius动力学模型,得到的货架期预测模型为SL=16.006e-0.15t（R2= 0.922 6）。结果表明,随着储藏时间的延长,细菌总数增加,脂肪的氧化和腐败现象加重,并且其品质的劣化速率随着温度的增长而增快。用Arrhenius方程描述的品质变化的动力模型有很高的拟合精度。建立的鱼糜制品的货架期预测模型相对误差能达到10%之内。     

基于鲜度的动力学模型预测鹰爪虾剩余货架期

为探究鹰爪虾在不同温度贮藏过程中的鲜度变化,实时监测物流期间的货架期,将鹰爪虾贮藏在-30,-18,0,4℃条件下,测定其K值、挥发性盐基氮(TVB-N)值与菌落总数(TVC),研究其货架期预测模型。结果表明:随着贮藏温度的降低,鹰爪虾的鲜度指标下降速率减慢,货架期延长,且不同温度组对鹰爪虾的鲜度指标有较大影响。采用Arrhenius方程构建贮藏温度、贮藏时间与K值、TVB-N值和菌落总数间的动力学模型,将其与食品TTT理论相结合,结果表明各项鲜度指标的拟合度较好(R~20.9),鹰爪虾的变温货架期预测模型对其剩余货架期的预测准确率较高,预测值与实测值的相对误差的绝对值不超过5%,说明基于鲜度指标建立的动力学模型可用于鹰爪虾变温冷链物流过程中剩余货架期的预测。     

市售简易包装牡蛎干常温保藏下货架期预测

目的建立市售简易包装牡蛎干货架期预测模型。方法对简易密封包装牡蛎干酸价、过氧化值、挥发性盐基氮(total volatile basic nitrogen,TVB-N)值3个指标随贮藏时间和温度变化情况进行测试和分析。结果牡蛎干在不同贮藏温度下,随着贮藏时间的延长品质逐渐下降,温度越低,品质衰败速率越缓慢,符合一级反应动力学模型,并根据Arrhenius理论公式建立了不同指标的货架期预测方程。经计算得出酸价、过氧化值、TVB-N值预测模型中的活化能分别为46.85、49.89、46.79 kJ/mol;指前因子k_0分别为7.80×10~5、2.77×10~6、9.54×10~5。结论本研究建立了市场流通中货架期的评估模型,并按照GB/T 26940-2011《牡蛎干》标准要求,以TVB-N值为判断指标,经25℃和40℃对照存放实验验证预测模型预测相对偏差分别为6.51%和2.41%。     

河鲫鱼在不同贮藏温度下的货架期模型预测

为了研究河鲫鱼在物流过程中的品质变化与货架期预测模型,将河鲫鱼分别贮藏在273、279、282、285、291K条件下,测定了河鲫鱼的感官指标、挥发性盐基氮(TVB-N)、菌落总数(TVC)、脂肪氧化(TBA)和鲜度指标K值随贮藏时间的变化规律。通过相应的品质能级函数分析,确定零级化学反应动力学更适合表现河鲫鱼各指标品质变化规律。利用Arrhenius方程对活化能Ea,A0和温度进行非线性拟合,得到TVB-N、TVC、TBA和K值的活化能(Ea)和指前因子(A0)分别为:77.68kJ/mol和4.590×1014、99.64kJ/mol和1.790×1018、83.78kJ/mol和1.146×1014、104.4kJ/mol和2.219×1020。结果表明:河鲫鱼的感官品质指标随着贮藏时间的延长而不断下降,且随着贮藏温度的升高而下将迅速,TVB-N、TVC、TBA及K值随着贮藏时间的延长而增加,温度越高各指标变化越快,且贮藏后期更快。用河鲫鱼贮藏在282K下的货架期实测值来验证建立的货架期预测模型,实验结果证明该模型所获得的货架期预测值相对误差达到±5%以内。因此可根据TVB-N、TVC、TBA和K值在273~291K范围内,对河鲫鱼的新鲜度和剩余货架期进行预测,同时也为其他水产品货架期的预测提供了一定的参考。     

半干鲐鱼片冷风干燥工艺优化及货架期预测

实验以鲐鱼为原料,分析了冷风干燥工艺参数对半干鲐鱼片品质和风味的影响,通过U*₉(94)均匀设计实验,以不同的干燥工艺因素(温度、相对湿度、风速)为自变量,测定半干鲐鱼片的挥发性盐基氮值(TVB-N值)、菌落总数(TVC)与硫代巴比妥酸值(TBA值),进行感官评价,并建立干燥条件下的回归模型,对其结果进行综合分析,确定冷风干燥工艺的最优参数组合,并结合一级动力学模型与Arrhenius方程,研究其货架期预测模型。结果表明:温度、风速对TVB-N值有显著影响(p<0.05),温度对TBA有显著作用(p<0.05)。半干鲐鱼片冷风干燥工艺的最优条件为温度15℃,风速2.4 m/s,相对湿度25%。在此条件下验证得到实测值与预测值的一致性较好,TVB-N、TBA值误差分别为0.71%、1.16%。半干鲐鱼片干燥时间为21 h,TVB-N值为25.33 mg/100 g,TVC为5.93×103 CFU/g,TBA值为1.11 mg/kg,感官评分为94.38分,鲜度好,风味佳。在-5~10℃范围内,建立的TVB-N值、TVC、TBA值与贮藏时间的动力学模型有较高拟合度,选用TVB-N、TBA值作为评判指标,可以准确预测半干鲐鱼片的货架期,本研究结果可为半干鲐鱼片的工业化生产提供理论依据。     

基于挥发性盐基氮快速预测冷鲜鸡货架期

为了解冷鲜鸡的货架期,以挥发性盐基氮（TVB-N）为品质表征参数,研究了冷鲜鸡在不同温度（5、10和15 ℃）下的变化规律,利用Arrhenius方程建立了不同温度下冷鲜鸡货架期预测模型,并对该模型进行内部验证和实际样本验证。结果表明:Arrhenius方程中TVB-N的活化能Ea为52.636 kJ/mol,指前因子k₀为3.8×107。以5、10和15 ℃作为验证温度,其相对误差为6.30%,6.00%和3.91%,实际样本验证最大相对误差为?10.5%,说明该模型拟合效果好。通过该模型可快速获得不同贮藏温度下冷鲜鸡的货架期,为生产企业和监管部门制定货架期标准提供理论依据。     

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.     

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.     

Influence des ions sur le pouvoir hydratant de l'ure e: e tude sur peau de porc ex vivo

This study deals with the influence of ions (NaCl and MgSO4) in a W/O emulsion containing 10% urea. Moisturization kinetics are assessed by corneometry on pig skin ex vivo. The formula's influence on urea penetration is measured by infrared spectrometry with an ATR device and the stripping method. Corneometry and spectroscopy were chosen to record simultaneously the hydratation levels and urea localization into superficial cell layers. Urea crystallization after evaporation of emulsions and aqueous solutions is described. Results show that urea does not hydrate nor penetrate when applied to the skin through an aqueous gel. In a W/O emulsion, sodium chloride increases the ability of urea to moisturize without improving penetration. In vitro urea crystallization is disturbed by sodium chloride or magnesium sulphate for solutions and emulsions. This stabilization by ions is correlated with good moisturization values. The stabilization of urea in the solute state provided by ions increases its water epidermal binding capacity without enhancing penetration.