ε-聚赖氨酸-壳聚糖/PE复合膜对鲜切茄子保鲜作用

利用ε-聚赖氨酸-壳聚糖/聚乙烯(PE)复合膜对鲜切茄子进行真空包装,并考察ε-聚赖氨酸含量(1%、3%、5%、7%)对鲜切茄子的保鲜效果影响。结果发现,随着贮藏天数的增加,鲜切茄子的感官品质、可溶性固形物均呈下降趋势,失质量率、褐变度均在增加。其中5%ε-聚赖氨酸含量的ε-聚赖氨酸-壳聚糖/PE复合膜对鲜切茄子的保鲜效果最佳。     

三种保鲜剂复配对生鲜面的保鲜效果

为延长生鲜面的保质期,本文优化了乙醇、丙酸钙、ε-聚赖氨酸盐酸盐三种保鲜剂的复配配方,并研究了最优配方下生鲜面在不同贮藏温度下的品质特性变化。结果表明,生鲜面最佳保鲜剂配方为:2.0%乙醇、0.020%丙酸钙与0.0060% ε-聚赖氨酸盐酸盐,在此配方下测得的菌落总数为1.27 lg CFU/g,霉菌总数为13 CFU/g,感官评价得分为90分。未添加保鲜剂的生鲜面在常温贮藏条件下的保质期为8 h。在最佳配方条件下,生鲜面在常温贮藏下保质期为4周;生鲜面在4 ℃贮藏4周时,水分含量、Aw、pH、色差、蒸煮特性、质构参数变化较小,感官评价得分较高;在25、35 ℃贮藏4周时,颜色逐渐变暗,感官、水分含量、水分活度、蒸煮品质均随贮藏时间的延长而下降。     

海藻酸钠和羧甲基纤维素钠涂膜改善鲜切豇豆贮藏特性的比较分析

为了提高鲜切豇豆的品质,本文研究了海藻酸钠(0.6%,m/m)和羧甲基纤维素钠(0.8%,m/m)两种涂膜剂对其贮藏期间的呼吸强度、维生素C、叶绿素等品质指标变化规律的影响。研究发现,与对照相比,在贮藏期间,海藻酸钠和羧甲基纤维素钠涂膜均有效降低鲜切豇豆的呼吸强度,维持较高的可溶性固形物含量,减少鲜切豇豆维生素C和叶绿素的损失,保持较高的过氧化物酶活性,减少丙二醛的积累。贮藏至12 d,海藻酸钠涂膜的鲜切豇豆呼吸强度为237.67 mg/(kg·h),处于较低水平;其维生素C、叶绿素及可溶性固形物含量分别比羧甲基纤维素钠涂膜的高13.06 mg/100 g、0.62 mg/g、0.49%,但丙二醛含量低11.36%。研究结果表明,海藻酸钠涂膜更有利于保持鲜切豇豆的品质及延长贮藏期,其用于豇豆的保鲜贮藏具有潜在的应用前景。     

生物保鲜剂延长冷鲜牛肉货架期的效果

为延长冷鲜牛肉的货架期,保证其贮藏期间的食用品质及安全性,采用单因素试验与正交试验筛选一组 复配生物保鲜剂（乳酸链球菌素、纳他霉素和ε-聚赖氨酸）,并研究其对冷鲜牛肉的保鲜效果。结果表明：复配 生物保鲜剂中3 种保鲜剂的最佳配比为乳酸链球菌素2.5 g/L、纳他霉素1.5 g/L、ε-聚赖氨酸3.0 g/L;冷鲜牛肉在 （4±1） ℃条件下贮藏8 d后,其挥发性盐基氮值为19.84 mgN/100 g,属于二级鲜肉;菌落总数较对照组降低2 个 数量级,表明复配生物保鲜剂能够有效抑制腐败菌的增长;贮藏后期,处理组冷鲜牛肉的汁液流失率较对照组减少 1.73%。复配生物保鲜剂可以将冷鲜牛肉的货架期有效延长4 d。     

超声-ε-聚赖氨酸盐酸盐复合处理对鲜切苹果的保鲜作用

为提高鲜切苹果品质、延长货架期,探究超声-ε-聚赖氨酸盐酸盐复合处理鲜切苹果的最优参数及其保鲜效果。采用Box-Behnken设计,以菌落增长数为响应值,通过响应面法确定超声-ε-聚赖氨酸盐酸盐复合处理鲜切苹果的最佳参数。根据菌落总数、霉菌和酵母、色差、V_C含量结果,评价超声-ε-聚赖氨酸盐酸盐复合处理对鲜切苹果贮藏期间的保鲜作用。结果表明,超声-ε-聚赖氨酸盐酸盐复合处理鲜切苹果的最优参数为:超声时间为10 min、超声温度为40 ℃、ε-聚赖氨酸盐酸盐浓度为0.2 g/L,切分前与切分后处理实际测定值分别为1.59 lg CFU/g、1.71 lg CFU/g,与预测值相对误差分别为3.92%、5.59%,拟合度高,模型可靠。利用优化的条件处理的鲜切苹果在4 ℃贮藏期间,细菌、霉菌和酵母增长速度显著低于（P<0.05）对照,V_C未受到明显破坏,切分前超声-ε-聚赖氨酸盐酸盐复合处理组色差上升速度低于对照组。响应面法优化的超声-ε-聚赖氨酸盐酸盐复合处理鲜切苹果是可行的,其中切分前超声处理效果较好,货架期比对照组延长4 d。     

抗坏血酸钙和ε-聚赖氨酸对鲜切甘薯保鲜护色效果的影响

以二郎苕甘薯为试验材料,研究在4℃贮藏条件下,抗坏血酸钙和ε-聚赖氨酸2种绿色保鲜剂及其复合处理对鲜切甘薯褐变度、菌落总数、总酚含量、苯丙氨酸解氨酶(Lphenylalanin ammonia-lyase,PAL)、多酚氧化酶(polyphenol oxidase,PPO)和过氧化物酶(Peroxidase,POD)活性等的影响。研究结果表明,与对照相比,5%抗坏血酸钙+0.03%ε-聚赖氨酸浸泡10min能够有效降低鲜切甘薯贮藏期间的褐变度和菌落总数,保持鲜切薯块较高的总酚含量,抑制鲜切薯块PAL、PPO、POD活性的升高,对提高鲜切甘薯贮藏品质和延长贮藏周期具有一定效果。     

气调结合生物保鲜剂对葡萄冷藏品质及电子鼻判别的影响

为了提高无核寒香蜜葡萄的贮运品质,在箱式气调的基础上,研究800、1000 mg/L浓度的纳他霉素和500、1000 mg/L浓度的ε-聚赖氨酸对无核寒香蜜葡萄微环境气体含量、感官、质地、营养、生理品质及电子鼻判别的影响。结果表明:生物保鲜剂的添加可以维持箱内较高的CO_2含量和较低的O_2含量,且不同浓度的相同生物保鲜剂间具有显著差别(P0.05);1000 mg/L纳他霉素和500 mg/L的ε-聚赖氨酸均可在不同程度保证无核寒香蜜葡萄的品质,且1000 mg/L纳他霉素处理无核寒香蜜葡萄的贮藏品质最佳,至60 d时,其落粒率和腐烂率为12.00%,果皮强度和脆性保持在4.04 N、196.00 g/s,TSS、TA及Vc含量分别为15.80%、0.68%、4.2 mg/100 g,呼吸强度和乙烯生成速率分别为40.60 mg CO_2/kg·h、1.20μL/kg·h。PCA和LDA方法均适用于气调结合生物保鲜剂处理无核寒香蜜葡萄冷藏期的风味分析判别,NATA800、ε-PL1000处理与其余处理风味有一定的差异。     

气调包装对鲜切菠萝品质的影响分析

该试验研究了包装材料对鲜切菠萝贮藏品质的影响。采用自发气调袋包装鲜切菠萝,对照组选用普通菠萝保鲜袋,置于4 ℃低温贮藏。测评了鲜切菠萝感官评价,探究了包装袋气体成分变化、硬度、可溶性固形物（TSS）、可滴定酸（TA）、抗坏血酸（Vc）、丙二醛（MDA）、乙醇等各项指标。结果表明,与对照组相比,气调袋包装的鲜切菠萝在贮藏期间O2浓度保持在11.29%以上,CO2浓度保持在3.03%以下,贮藏12 d感官得分为9.67分,硬度下降11.17%,TSS下降19.44%,TA下降12.14%,Vc含量下降21.78%,有效缓解了鲜切菠萝各生理指标下降的趋势。与普通保鲜袋相比,气调袋抑制了菠萝MDA含量和乙醇含量的增加,普通袋MDA含量为3.52 μmol/g,而气调袋为2.99 μmol/g,缓解了鲜切菠萝的膜脂过氧化;普通袋乙醇含量高达615.9 μg/g,而气调袋乙醇含量仅为120.68 μg/g,大大减少了菠萝在贮藏期间无氧呼吸产生乙醇。因此,采用自发气调袋包装有效的保持了鲜切菠萝的品质,延长了鲜切菠萝的贮藏期,具有广阔的市场前景。     

ε-聚赖氨酸-壳聚糖/PE复合膜对鲜切茄子保鲜作用

利用ε-聚赖氨酸-壳聚糖/聚乙烯（PE）复合膜对鲜切茄子进行真空包装,并考察ε-聚赖氨酸含量（1%、3%、5%、7%）对鲜切茄子的保鲜效果影响。结果发现,随着贮藏天数的增加,鲜切茄子的感官品质、可溶性固形物均呈下降趋势,失质量率、褐变度均在增加。其中5% ε-聚赖氨酸含量的ε-聚赖氨酸-壳聚糖/PE复合膜对鲜切茄子的保鲜效果最佳。     

复合保鲜剂对鲜切山药保鲜效果的影响

为了延缓鲜切山药的褐变和品质劣变,延长保鲜期。从洋葱中提取洋葱油,结合保鲜剂柠檬酸和壳聚糖,以色差L*值和感官评分为考察指标,在单因素试验的基础上进行正交试验,筛选适合鲜切山药保鲜的复合保鲜剂配方。结果表明:鲜切山药最佳保鲜剂组合为0.6%洋葱油+1.0%柠檬酸+1.0%壳聚糖,与清水处理相比,该组合可显著抑制鲜切山药贮藏过程中多酚氧化酶(PPO)和过氧化物酶(POD)的活性,降低鲜切山药的相对电导率和丙二醛(MDA)含量,延缓失重和软化,保持鲜切山药的亮度和总酚含量,维持鲜切山药可溶性固形物和还原糖含量,且具有较好的感官品质。与对照组相比,该复合保鲜剂可使鲜切山药保鲜期延长6d左右。     

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.     

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.     

低温带皮菜籽粕微粉的不同粒级部分的功能特性

为研究低温带皮菜籽粕微粉的不同粒级部分的功能特性,以经低温脱脂的带皮菜籽粕为原料,经微粉碎后筛分成212~425μm、150~212μm和106~150μm的3个不同粒级的微粉样品,检测这些样品的吸水性、吸油性、乳化性和乳化稳定性、蛋白质体外消化率。结果表明:1 3个不同粒级的微粉样品之间的粗纤维含量存在显著差异,表明三者的结构组成成分有一定差异。23个微粉样品的乳化活性和乳化稳定性随粒度级别的减小而显著增加(P0.01)。33个微粉样品的蛋白质体外消化率随粒度级别的减小而显著增加(P0.01)。4不同粒级带皮菜籽粕微粉样品的吸水性与吸油性受其结构组成物质不同和粒度的双重影响,与粒度的相关性不明显。     

Microbiology of food taints

Fresh and processed foods are often spoilt by the presence of undesirable flavours and odours caused by microbial action. The aim of this paper is to review the current knowledge of microbiologically induced taints that occur in a wide range of foodstuffs, including meats, poultry, fish, crustaceans, milk, dairy products, fruits, vegetables, cereals and cereal products. Examples have been chosen where the compounds responsible for the taint have been identified and sufficient data obtained to demonstrate the involvement of microorganisms. However, in some cases the full identity of the causative organism may not have been elucidated. The types of microorganisms covered by this review include bacteria, fungi, yeasts, actinomycetes and cyanobacteria. Although cyanobacteria do not in general infect foods, their presence in aqueous systems and water supplies can lead to off-flavours in aquatic organisms and processed foodstuffs. Several examples of each of these processes are discussed. Wherever possible, the likely biosynthetic pathway used by the microorganism to produce the offending compound in a foodstuff is indicated.