炒板栗的防褐变研究

本文主要研究了板栗褐变的主要原因以及水质、热烫对板栗褐变的影响.通过单因素实验筛选出四种护色剂:亚硫酸氢钠、植酸、柠檬酸、EDTA-2Na.在此基础上进行了正交实验,最终确定了炒板栗的最佳护色方案为NaHSO3 0.3 %、植酸0.4 %、柠檬酸0.1 %、EDTA-2Na 0.03 %.     

鲜切雪莲果防褐绿变工艺研究

以雪莲果为试材,研究鲜切雪莲果防褐绿变的工艺.实验中比较了不同护色处理方法的护色效果,采用正交实验筛选出鲜切雪莲果的最佳组合护色条件,雪莲果最优组合防褐绿变的工艺为0.1%CaCl2,0.15%柠檬酸,浸泡30min,在.21℃下冻藏7d,未见褐变和绿变.     

响应面法优化“黄元帅”苹果浓缩汁防褐变工艺研究

针对"黄元帅"苹果浓缩汁贮藏期间易褐变的难题,以可溶性固形物含量为70.25%的浓缩苹果汁为实验原料,利用响应面分析法优化苹果浓缩汁制备及贮藏过程中的防褐变工艺,在单因素实验的基础上,以柠檬酸添加量、L-抗坏血酸添加量、L-半胱氨酸添加量和不同热烫温度为影响因子,苹果浓缩汁的褐变抑制率为响应值,通过BoxBenhnken中心组合设计原理,模拟得到二次多项式回归方程的预测模型,确定最佳防褐变工艺为:柠檬酸添加量0.12%、L-半胱氨酸添加量0.15%,热烫90℃,10min处理对苹果汁的褐变抑制率达到93.22%,与预测值相符。因此,采用RSA法优化得到的护色条件参数准确、可靠,具有实用价值,为苹果浓缩汁褐变调控提供理论依据。     

杏的无硫护色工艺研究

研究杏的无硫护色工艺.结果表明:杏片的厚度、护色工艺影响护色效果.将4mm～5mm杏片浸泡于0.3%β-环状糊精+0.2%葡萄糖酸锌复合液中,热烫2 min,经此处理的杏片仍保持杏原有的橙黄色,具有良好的感官效果.为了防止破碎的杏浆料的褐变,采用90℃下热烫2min以钝化多酶氧化酶(PPO),防止有酶参与的酶促褐变.     

杏的无硫护色工艺研究

研究杏的无硫护色工艺.结果表明:杏片的厚度、护色工艺影响护色效果.将4mm-5mm杏片浸泡于0.3%a-环状糊精 0.2%葡萄糖酸锌复合液中.热烫2mim.经此处理的杏片仍保持杏原有的橙黄色,具有良好的感官效果.为了防止破碎的杏浆料的褐变,采用90℃下热烫2min以钝化多酶氧化酶(PPO),防止有酶参与的酶促褐变.     

人工干制树上干杏的防褐变研究

为有效解决树上干杏人工干制过程中的褐变问题,优化树上干杏的护色干制工艺条件,以色度、感官评分为响应值,选择热烫温度、热烫时间及护色剂VC浓度为实验因子,进行响应面分析。得到最优护色参数:热烫温度95.6℃,热烫时间4.62 min,护色剂VC浓度1.63%。实验结果表明树上干杏护色干制工艺合理可行,能有效抑制干制过程中的褐变。     

鲜切雪莲果护色保鲜工艺的研究

以雪莲果为试材,研究鲜切雪莲果防酶促褐变的工艺.实验中将物理方法和化学方法结合起来,采用正交实验筛选出鲜切雪莲果的最佳组合护色剂,从而确定雪莲果最优组合防褐变的工艺.结果表明:抗坏血酸、柠檬酸、EDTA-Na2和NaC1都有抑制褐变的效果,但组合抑制剂的护色效果比单元抑制剂好.且最佳组合护色剂为:0.15%抗坏血酸+O.10%柠檬酸+0.05%EDTA-Na2+1.5%NaC1.     

山胡椒护色技术的研究

为解决山胡椒在加工中的褐变问题,通过热烫与护色剂单因素实验和正交实验,以产品的总色差△E为指标,对山胡椒护色技术进行了研究.结果表明:在90℃漂烫温度下,漂烫60s后,其最佳护色剂组合为0.3％氯化钙、0.08％抗坏血酸、0.03％乙酸铜、0.3％植酸,在该条件下进行验证,山胡椒样品△E为6.02,取得了良好的护色效果.     

马铃薯全粉加工过程中的护色

以马铃薯为主要原料,对马铃薯全粉加工过程中的护色条件和护色剂用量进行分析研究.试验结果表明,最佳护色条件为,热烫时间2min,护色温度70℃,护色时间20min;以0.10%VC、0.30%植酸、0.40%柠檬酸、0.35%L-半胱氨酸作为复合护色剂可有效地抑制马铃薯全粉加工过程中的褐变.     

压差膨化苹果脆片的无硫护色研究

针对压差膨化前处理中苹果的酶促褐变进行了无硫护色研究,通过单因素试验、正交试验研究了不同护色剂及其组合对苹果片的护色效果的影响。试验结果表明柠檬酸、氯化钠、抗坏血酸对苹果片护色效果影响较显著,试验中最佳的复配护色剂组合为:柠檬酸0.4%、抗坏血酸0.04%、氯化钠1.0%;护色温度是25℃,时间20 min,使用该方法护色的苹果片能很好抑制膨化前的酶促褐变。     

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.