百里香精油抗菌涂层包装对鲜切生菜货架期内理化品质及微生物的影响

精油抗菌涂层包装是一种环保的包装技术。文中利用百里香精油抗菌涂层包装膜包装鲜切生菜,通过检测鲜切生菜货架期内的呼吸强度、抗坏血酸含量、多酚氧化酶活性、菌落总数等指标,并结合生菜感官品质,对比普通PE食品保鲜膜与抗菌包装膜在不同贮藏温度下(1、4、10℃)的保鲜效果差异,最后通过荧光假单胞菌的回接实验探究薄膜对鲜切生菜的优势腐败菌的抑制效果。结果表明:精油抗菌包装膜能较好地抑制鲜切生菜的呼吸强度、微生物生长及多酚氧化酶的活性,减少贮藏期内VC的损失,维持生菜良好的感官品质。当与4℃的低温贮藏结合时,可将鲜切生菜的货架期延长至5 d。     

鲜切生菜在贮藏期间的微生物生长模型

主要研究了在 0℃、4℃和 2 5℃贮藏温度下鲜切生菜中细菌的生长趋势和感官质量的变化。研究结果表明 ,实验中所建立的Gompertz模型能有效地拟合在不同贮藏温度下鲜切生菜中细菌总数的动态变化 ,从而能预测不同贮藏温度下、不同贮藏时间内鲜切生菜中的细菌总数 ,为快速、有效地评估鲜切生菜的货架期和微生物安全性 ,提供了一个方便有效的方法。同时探讨了鲜切生菜中细菌总数与细胞组织腐烂的关系 ,即当细菌总数≤ 1 0 6 cfu/ g ,鲜切生菜的细胞组织不会腐烂。     

4种常用蔬菜清洗剂处理对鲜切萝卜抑菌及保鲜效果比较

目的 评价过氧化氢(hydrogen peroxide, H2O2)、过氧乙酸(peracetic acid, PAA)、次氯酸钠(sodium hypochlorite, NaClO)和二氧化氯(chlorine dioxide, ClO2) 4种常用蔬菜清洗剂对鲜切萝卜的清洗抑菌及产品保鲜应用效果。方法 对鲜切萝卜进行6种处理: (1)未清洗处理(CK1)、(2)清水处理2 min (CK2)、(3) 4种清洗剂处理2 min, 并于4℃贮藏12 d。对比不同清洗方案下鲜切萝卜产品的质构、颜色、感官及微生物指标变化情况, 最终筛选出抑制鲜切萝卜腐败变质, 维持其感官品质的最优清洗剂。结果 相比于H2O2和ClO2处理, PAA和NaClO处理能更好的抑制细菌、霉菌和酵母的生长; H2O2处理感官评分最高、色泽最佳, 其次为NaClO和ClO2, PAA最差。25 mg/L H2O2、150 mg/L PAA、100 mg/L NaClO和30 mg/L ClO2为每种清洗剂的最佳清洗浓度。进一步筛选表明100 mg/L NaClO可使鲜切萝卜表面的菌落总数保持在5 log CFU/g以下, 霉菌和酵母数量保持在4 log CFU/g以下, 并在贮藏结束后较好维持了萝卜的硬度、色泽、感官。结论 100 mg/L NaClO能有效抑制鲜切萝卜表面微生物的生长,同时其感官品质也得以维持,可在萝卜鲜切产品中应用推广。     

鲜切莴笋低温贮藏期间的品质变化

以鲜切莴笋为原料,研究聚丙烯(PP)保鲜盒和真空包装下鲜切莴笋在低温贮藏期间品质的变化。试验结果表明:两种包装下的鲜切莴笋在9 h时品质良好,而24 h后的鲜切莴笋已不具有商业价值,真空包装能够有效地控制鲜切莴笋的失重率、可滴定酸含量、呼吸强度、VC损失率、叶绿素损失率、丙二醛含量与细菌总数,提高莴笋的感官品质和营养价值。     

鲜切小白菜和生菜不同贮藏温度下货架期预测模型的建立

为研究鲜切小白菜和鲜切生菜在贮藏期间的品质变化,并预测其货架期,本文以鲜切小白菜和鲜切生菜为研究对象,对其贮藏期间的感官品质、细菌总数和大肠菌群数变化进行研究,并以细菌总数为自变量对低温与室温下鲜切小白菜和生菜货架期预测模型进行拟合。结果显示,在4℃与25℃下贮藏时间分别为10 d与3 d时,两种蔬菜的感官评价均大于5分,超过了消费者接受范围,细菌总数和大肠菌群数也在该贮藏时间时超出了标准规定范围,得出鲜切小白菜和鲜切生菜在4℃与25℃下的货架期终点分别为10 d与3 d;低温与室温下鲜切小白菜和鲜切生菜货架期预测模型拟合结果分别为:SL_(4℃)=ln{ln[5.096/(N_1-1.990)]}-1/0.279+7.452和SL_(25℃)=ln{ln[3.621/(N_1-3.651)]}-1/1.124+1.512;两个预测模型的偏差因子分别为0.979和1.001,准确因子分别为1.050和1.040,表明所建立的模型是有效的。     

鲜切苹果臭氧水杀菌工艺研究

以红富士苹果为试材,在鲜切加工过程中,采用臭氧水进行杀菌处理,确定了臭氧水的最佳杀菌浓度、杀菌时间和杀菌温度,并研究了臭氧水杀菌处理对鲜切苹果低温贮藏期间菌落总数和品质指标的影响。结果表明,1.00 mg/L 15℃臭氧水处理鲜切苹果5 min,对其表面微生物的杀灭作用效果明显,在贮藏9 d时,该处理鲜切苹果的菌落总数仅是对照的1.7%。同时,该处理抑制了鲜切苹果的褐变,延缓了果实硬度、可溶性固形物和抗坏血酸含量的下降,降低了失重率。总之,1.00 mg/L 15℃臭氧水处理鲜切苹果5 min,杀菌效果和保持果实品质的效果均较好。     

不同贮藏温度下鲜切马铃薯的生理生化变化

目的:研究18,10,4℃3个贮藏温度下鲜切马铃薯的生理生化变化;方法:测定颜色、硬度、呼吸强度、Vc含量、总酚和丙二醛含量以及多酚氧化酶、过氧化物酶活性的变化;结果:切割引起的伤害会导致马铃薯的呼吸强度增强.诱导了与褐变相关酶的活性增加,促使切割马铃薯褐变的发生,颜色变差,硬度下降,总酚含量增加,但这种伤害也使鲜切马铃薯Vc含量增加.18℃条件下,鲜切马铃薯的品质在第3天使开始下降;10℃条件下,鲜切马铃薯的品质在第5天开始下降,4℃条件下,鲜切马铃薯的品质在贮藏期内(6 d)一直保持良好;结论:低温贮藏能够有效地保持鲜切马铃薯的品质.     

不同清洗方式对鲜切鸡毛菜保鲜效果的影响

实验采用臭氧水、电解水、次氯酸钠、超声波对鲜切鸡毛菜进行清洗,自来水清洗作为对照。通过测定贮藏期间叶绿素、VC、亚硝酸盐、细菌总数、感官品质等来比较清洗效果。实验结果表明,臭氧水和超声波处理的样品在杀菌、保持营养物质及感官上的效果相对其他处理的样品要好,贮藏至14d仍有商品价值和食用价值,可作为鲜切鸡毛菜加工过程中的处理方式。     

不同预冷方式对鲜切紫甘蓝冷链贮运销品质变化的影响

采用冰水、冷库、压差和强制通风预冷4种方式对紫甘蓝进行处理,经包装、模拟运输后放于0℃下进行20 d保鲜实验,分析在贮藏期间其呼吸代谢、褐变、营养特性及理化指标的变化。结果显示,压差预冷对鲜切紫甘蓝冷链贮运销品质保鲜效果最佳。贮藏结束时,其花青素、丙二醛(MDA)、可滴定酸和可溶性固形物分别为4.09 mg/L、3.09 mmol/g FW、0.059 8%和8.53%,同时呼吸强度、过氧化物酶(POD)、多酚氧化酶(PPO)得到了有效地抑制。压差预冷延缓了鲜切紫甘蓝在冷链贮运销期间褐变的发生,有效抑制了微生物(菌落总数和大肠菌群)的增长,维持感官品质。综合以上,压差预冷是鲜切紫甘蓝冷链贮运销期间较适宜的预冷方式。     

运输时间对鲜切生菜品质的影响

研究运输时间对鲜切蔬菜品质的影响。以鲜切生菜为研究对象,进行2、3、5 h冷藏运输,然后在模拟商超货架(4℃)进行贮藏。在货架第0、2、4、6天测定样品菌落总数、硬度、Vc含量和感官评分等,首次采用Image-pro-plus表征叶片褐变面积比例。结果发现:短途运输(2、3 h)对鲜切生菜品质影响小,长途运输(5 h)引起鲜切生菜叶片褐变比例显著提高。因此,长途运输对鲜切生菜的品质产生负面影响。     

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.