基于聚类和时序分析的砂梨果实耐贮性及贮藏品质分析预测

目的:对3个品种砂梨的贮藏期和品质进行评价,为品种选育和保鲜技术的研发提供理论支撑。方法:以遗传背景相似的早生新水、沪晶梨18(HJ18)、沪晶梨67(HJ67)为试材,分别将成熟度一致的3个品种砂梨果实放置于温度为(1.0±0.5)℃、相对湿度85%～90%的冷库中贮藏60 d,每10 d对果实质构、糖酸及挥发性物质进行测定,基于聚类、主成分、时序分析,划分贮藏期和贮藏品质。结果:3个品种砂梨果实质地、糖酸及挥发性物质均受到贮藏时间的调控,且不同指标间有一定的相关性。可将14个品质评价参数简化为果肉组织硬度、咀嚼性、紧实度、果皮脆性、弹性、苹果酸、柠檬酸、可溶性固形物和果糖9个指标;传感器S2、S6、S7、S8、S9的贡献率较大。基于14个品质指标,贮藏期间的HJ67与早生新水和HJ18处于相对独立的空间;基于10个传感器响应值,3个品种存在空间交集,未得到有效区分。3个品种砂梨的贮藏时间被划分为不同的区间,基于质地、非挥发性和挥发性物质的划分结果较为一致,HJ67被划分为0～20,30,40～50,60 d 4个时间段。结论:HJ67质地、糖酸含量和挥发性物质与早生新水和HJ18差...     

1- 甲基环丙烯对李果实冷藏及货架期非挥发性风味物质的影响

使用多变量分析方法研究1-MCP对‘黑琥珀’李果实0℃贮藏和随后的20℃货架期间非挥发性的糖、有机酸和氨基酸的影响。单因素试验结果表明：低温贮藏期间,李果实蔗糖和苹果酸含量逐渐下降,D-果糖含量先降后升,其余组分均在贮藏67d时达到释放高峰;货架期间,96d后的货架期非挥发性组分含量均达到高峰。主成分分析结果表明：与出库时相比,冷藏67d后的货架9d时各组分含量均降低,而贮藏后期的货架9d时则升高;冷藏67d时及冷藏96d后的货架期,1-MCP处理均显著降低了糖、酸类物质的峰值,减缓了糖、酸物质的代谢速率,维持了冷藏期间的营养品质并延缓了货架期的品质劣变。偏最小二乘和通径分析结果表明：D-果糖与感官甜酸比呈显著正相关,是主要的直接与间接因子;苹果酸对感官酸度和可溶性固形物(SSC)均有显著正相关性,且对SSC主要通过D -葡萄糖的间接效应来实现;山梨糖醇与pH值呈极显著负相关。     

1-甲基环丙烯对李果实采后衰老期间非挥发性风味物质影响的多变量分析

采用多变量分析的方法研究1-甲基环丙烯(1-MCP)对‘黑琥珀’李果实20℃贮藏期间非挥发性风味物质形成的影响。结果表明：李果实中主要的糖酸组分是D-果糖、D-葡萄糖、蔗糖、山梨糖醇和苹果酸,D-果糖在采收时与贮藏前期释放较多,蔗糖在贮藏后期时含量较高;1-MCP处理抑制了蔗糖向D-果糖和D-葡萄糖的转化,延缓了可溶性固形物含量的下降,在贮藏后期,1-MCP处理诱导苹果酸、柠檬酸和L-天冬氨酸含量的降低,而增加了果实的pH值。偏最小二乘回归与通径分析结果表明,感官甜酸比与山梨糖醇、蔗糖呈高度正相关,酸度与苹果酸呈高度正相关,且蔗糖是甜酸比的主效因子,对甜酸比的影响主要是通过对山梨糖醇、D-果糖和苹果酸的间接效应实现的。     

臭氧对砀山酥梨采后生理及腐烂效果的影响

研究了臭氧对冷藏条件下砀山酥梨采后生理以及贮期病害的影响。在冷藏(缓慢降温至(0±0.5℃)期间,每日用4 mg/m~3臭氧处理砀山酥梨3 h,定期测定了贮藏期相关生理指标和腐烂率,并进行了臭氧对砀山酥梨主要致腐菌梨青霉、梨褐腐、梨轮纹的离体和活体实验。臭氧处理可显著抑制砀山酥梨的呼吸强度,延缓可溶性固形物、可滴定酸以及丙二醛含量,有效降低果实的腐烂率,但对果实硬度没有显著影响;臭氧明显抑制引起砀山酥梨发生腐烂的青霉痛、褐腐病、以及轮纹病病原真菌孢子的萌发,抑制了接种病原菌在梨果实上的扩展。将臭氧用于砀山酥梨的贮藏,既可维持较高的贮藏品质,又可防治果实腐烂。     

不同采收期对鸭梨采后贮藏香气成分的影响

香气成分的损失是梨果实贮藏期间风味裂变的主要表现之一,掌握不同成熟度梨果实香气变化规律对建立基于风味品质变化的梨果实采收和贮藏技术有重要意义。采用SPME-GC 的方法,对不同采收期(早、中、晚)鸭梨果实贮藏期间的主要香气成分进行分析,结果表明,鸭梨果实的主要香气成分为乙酸乙酯、己醛、己醇、丁酸乙酯、己酸乙酯等。采收期不同对鸭梨果实贮藏期间香气成分变化有明显的影响。早采鸭梨香气成分的产生受到抑制,贮藏期间含量一直较低;在贮藏初期,晚采梨果实采收后香气成分总含量高于早采和中采果实,但贮藏过程中香气容易散失,贮藏后期下降较快;中期采收的梨果实贮藏期间香气成分逐渐积累,贮藏6 个月时大部分香气成分含量显著高于早采和晚采果实(P ＜ 0.05)。     

3种梨贮藏期间果实品质、可溶性糖和有机酸含量变化

以玉露香梨、红香酥梨、酥梨为试材,研究并分析贮藏期间果实品质变化规律及可溶性糖、有机酸含量的变化。结果表明,随着贮藏时间延长,玉露香梨和红香酥梨果皮由绿向黄转变,油腻化程度不断增大,14 d货架期间果皮变黄和油腻化程度更加明显。3种梨果实硬度在贮藏期间均呈现逐渐下降趋势,红香酥梨硬度显著高于玉露香梨和酥梨（P<0.05）。3种梨果实的主要糖类均为果糖和葡萄糖,果糖含量高于葡萄糖和蔗糖含量之和。玉露香梨的总可溶性糖含量高于酥梨,显著高于红香酥梨（P<0.05）,酥梨的总可溶性糖含量降低幅度较玉露香梨和红香酥梨大。玉露香梨、红香酥梨、酥梨均为苹果酸优势型梨品种,3种梨的总有机酸含量在低温贮藏前期增加,中后期下降,苹果酸的变化趋势与总有机酸相似。     

CO2高传导保鲜膜处理对雪青梨贮藏品质及生理的影响

以雪青梨果实为试材,研究CO2高传导保鲜膜在低温贮藏条件下对雪青梨果实采后贮藏品质及生理特性的影响。结果表明：CO2高传导保鲜膜处理可推迟雪青梨呼吸高峰的出现,抑制PPO活性的升高,降低MDA含量,从而减缓果实的衰老;处理组可明显延缓雪青梨果实硬度、可滴定酸和VC含量的下降,抑制可溶性固形物含量的升高,从而较好地保持果实在贮藏期间的品质和风味。     

1-MCP处理对新高梨冷藏保鲜效果的影响

以新高梨果实为试材,通过对1-甲基环丙烯(1-MCP)处理新高梨冷藏期间主要生理指标和感官指标变化规律的分析,研究了1-MCP处理对新高梨果实冷藏保鲜效果的影响.结果表明:1-MCP处理推迟了乙烯和呼吸高峰的出现,抑制了果实丙二醛(MDA)和果皮相对膜透性的升高,延缓其衰老,明显延缓了果实硬度的下降,抑制了可溶性固形物含量的升高,从而较好地保持果实在贮藏期间的品质和风味;对照和处理的可滴定酸(TA)含量无明显变化:1-MCP处理可以抑制果心褐变,但经过1-MCP处理却加速了果实的果皮褐变.     

成熟度对‘红香酥’梨冷藏及货架期品质的影响

[目的]比较不同采收成熟度‘红香酥’梨果实低温贮藏及货架期品质的差异。[方法]基于IAD值将‘红香酥’梨果实成熟度分为3个等级（低、中、高）,果实置于（0±0.5）℃条件下冷藏210、300 d 后在(20 ±1)℃货架下放置7 d时,比较冷藏及常温货架条件下,低（1.30～1.63）、中（0.98～1.30）、高成熟度（0.65～0.98）‘红香酥’梨果实的果皮色差(L值和ho)、硬度、可溶性固形物含量（Soluble solids content, SSC）、可滴定酸（Titratable acid,TA）含量、固酸比、感官分值、黑心指数和腐烂指数的动态变化。[结果]随着贮藏期的延长,各成熟度果实的硬度、可滴定酸含量、感官分值下降;固酸比、黑心指数、腐烂率升高。低成熟度果实色度角（ho）降低,L值和SSC升高;中成熟度果实色度角（ho）降低,SSC升高;高成熟度果实SSC降低。高成熟度果实SSC、固酸比、果心褐变指数显著高于中、低成熟度,可滴定酸含量、果皮ho显著低于中、低成熟度,3个成熟度果实硬度无显著差异,低、中成熟度果实黑心指数间无差异,但显著低于高成熟度。至冷藏300 d后货架7 d时,低、中成熟度果实较高成熟度果实,果心褐变指数低19.83%、23.67%,固酸比低5.48%、30.62%。中成熟度果实腐烂率显著低于低、高成熟度果实63.66%、57.14%,但低、高成熟度间无差异。[结论]采摘成熟度对‘红香酥’梨贮藏效果的影响较大,低成熟度果实适合中期贮藏,中成熟度果实更适合长期贮藏,高成熟度果实适合短期贮藏。     

1-MCP处理对不同期采收的阿克苏富士苹果在采后贮藏期糖代谢的影响

以阿克苏富士苹果为试材,通过测定在贮藏过程中(0~150d),果实蔗糖、葡萄糖、果糖和山梨醇含量,以及蔗糖磷酸合成酶(SPS)、蔗糖合成酶(SS-S、SS-C)、酸性转化酶(AI)、中性转化酶(NI)和山梨醇脱氢酶(SDH)的活性,研究采后苹果果实糖代谢及相关酶活性的变化规律并分析了1-MCP处理对它们的影响。结果表明:在采后贮藏期间1-MCP处理在一定程度上抑制了贮藏过程中富士苹果果实蔗糖、葡萄糖、果糖和山梨醇含量的增加,且对不同采收期果实酶活性的影响效果不同,果实中蔗糖、山梨醇含量以及SDH活性呈下降趋势,果糖含量、葡萄糖含量、与SPS、SS-S活性呈先下降后上升趋势,AI与NI在贮藏过程中出现明显峰值,且1-MCP处理可以显著提高这一峰值。     

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.     

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.     

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.     

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.     

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.