微波处理对板栗仁酶促褐变的影响

研究了微波处理对板栗仁中多酚氧化酶(PPO)和过氧化物酶(POD)活性的影响,通过改变微波处理时间和处理量,测定了不同处理条件下板栗仁的PPO、POD活性和色差ΔL*值。结果表明:PPO的活性对栗仁酶促褐变的影响较大,栗仁中POD的热稳定差,易失活。在功率密度8 W/g、处理时间100 s的条件下,PPO活力下降为18.33 U/m L,POD活力为0.53 U/m L,栗仁色差ΔL*值为7.46。说明微波处理栗仁能很好地抑制酶促褐变的发生,起到了较好的护色效果。     

微波辅助板栗脱壳去皮的技术研究

板栗具有很高的食用和药用价值。随着板栗产量的不断提高,板栗脱壳去衣成为其加工过程中的一大难题。本文根据微波能加热原理,通过正交实验,确定了一种板栗微波同步脱壳去皮的新方法,在快速、高效去除板栗外壳和内皮的同时,最大程度保持了栗仁原有的色泽、风味和营养。结果表明,当微波功率为800W,板栗微波脱壳去皮的最佳工艺分别为:大板栗,加入量300g,第一次微波25s,冷却7min,第二次微波15s;中板栗,加入量250g,第一次微波15s,冷却6min,第二次微波20s;小板栗,加入量250g,第一次微波15s,冷却6min,第二次微波10s。经验证,在最优组合条件下,大、中、小板栗的脱壳率均可达到80%以上,破仁率和熟化度则小于15%。     

脱水板栗片制备工艺的优化

以信阳大板栗为试验材料,以板栗片营养成分、色差值、复水率为考察对象,对热风干燥、真空干燥、微波干燥三种工艺脱水板栗片的工艺进行了研究。结果表明,板栗片经过护色后,切成0.1 cm薄片,在热风干燥工艺中,以始温35℃,以5℃/h的速度升温,至60℃条件下保持1 h,再以5℃/h的速度降温至50℃,干燥6 h,得到的板栗片能保留板栗原有的色、香、味;在真空干燥工艺中,最佳干燥条件为:真空度0.07 MPa,温度设定在80℃,干燥时间3 h,板栗片色差值最小;在微波干燥工艺中,最佳干燥条件为:微波功率为400 k W,干燥8 min,板栗片的色泽较好;经过比较脱水板栗片营养成分、色差值及复水率得出,真空干燥法板栗片的营养成分保留最高,色差最小,复水率最高。     

板栗真空爆壳工艺条件的优化

以浙江丽水产的新鲜板栗为原料,对影响板栗真空爆壳效果的预热温度、预热时间、爆壳温度、爆壳时间等主要因素进行试验研究,优化板栗真空爆壳工艺条件。结果表明,其最佳工艺参数为预热温度80℃,预热时间20min,爆壳温度75℃,爆壳时间120min。该工艺条件下,板栗的爆壳率可达到90%以上,而栗仁失水率低于3%,保持生鲜完好。     

无损伤栗果的微波爆壳工艺研究

栗果的脱壳去衣是板栗深加工的头道工序,历来是板栗加工的技术难题,已成为发展板栗加工业的制约因素。研究将微波技术引入栗果脱壳过程,以期找到一种有效的栗果脱壳去衣方法。研究结果表明:利用微波技术可实现对栗果的一次性脱壳去衣,一次性栗果爆壳率可达90%,栗果微波爆壳的合理工艺条件为:原料→ 称重分级 → 90℃预热干燥15 min →微波脉冲处理(平均功率495 W)→ 爆裂栗果 → 分离壳衣 → 栗仁(粉)。     

板栗微波去壳切口工艺优化

主要研究切口板栗的相关工艺条件,以期获得较好的爆壳效果。按照板栗背部中轴位置,对板栗进行纵向切口,且切口长度为全长,切口深度不伤及栗仁和切口数为1道时为宜;经切口的物料在微波功率700W、处理时间60s的条件下,板栗爆壳率达90%。     

微波复热时间和微波功率对预油炸牛肉串品质的影响

研究了微波加热时间(30、40、60、90、120s)和微波功率(350、490、700W)对预油炸牛肉串出品率、剪切力、色差和感官评价的影响.结果表明,在不同微波复热条件下,牛肉串的出品率、剪切力、色差变化和总体可接受性存在明显差异(p＜0.05).在同一微波功率条件下,随着微波加热时间的延长,肉串的出品率逐渐下降,亮度L*值降低,红色度a*值升高;除微波加热30s外,随着微波加热时间的延长,肉串的剪切力值增加,嫩度下降.牛肉串在700W加热40s、490W加热40s和60s时,不仅明显提高了肉串的出品率,而且改善了牛肉串的色泽,并使肉串保持较低的剪切力值.     

响应面法优化低脂甘薯脆片加工工艺

以红心甘薯为原料,优化低脂甘薯片生产过程中漂烫、热风干燥、油炸等关键工艺参数,以产品含油率和色差(L*值和b*值)为评价指标,并通过响应面优化确定最优的低脂甘薯片生产工艺。结果表明,较优漂烫工艺条件为:漂烫温度70 ℃,漂烫时间7 min;较优的热风干燥工艺条件为:热风干燥温度70 ℃,热风干燥时间40 min;最优油炸工艺条件为:预油炸温度149 ℃,预油炸时间98 s,二次油炸温度190 ℃,在该条件下测定含油率的平均值达(17.1±0.2)%。该工艺条件下制得的甘薯脆片含油率低于同类产品,外观亮黄,无焦糊现象。     

变温烘烤工艺对广式香肠品质的影响

中式香肠烘烤温度各地都不同,为得到最佳香肠干燥工艺参数,本实验对香肠采用二段式变温烘烤,对变温烘烤的温度和时间进行了筛选,并与52℃传统恒温烘烤的香肠品质进行了比较。结果显示:前期烘烤时间和后期烘烤温度对广式香肠总体接受度存在显著性影响,以总体接受度为预测条件,得出广式香肠最优烘烤方式为65℃烘烤7h后48℃烘烤;与传统组比较发现:变温组香肠L*值、弹性高于传统组(p0.05),a*值、过氧化值和回复性小于传统组(p0.05),变温烘烤所需总时间为13.45 h,比传统烘烤组减少1.58 h。实验结果得出:广式香肠最优变温烘烤工艺为65℃烘烤7h后48℃烘烤。     

微波-热风联用制取笋干工艺条件优化

为获得干燥时间短、干燥品质好的笋干,以竹笋为原料,在单因素试验的基础上,根据中心组合试验设计原理,分析微波干燥功率、微波干燥时间和热风干燥温度3 个因素对笋干感官评分、总干燥时间、复水比、色差和硬度指标的影响,以确定微波-热风联用制取笋干最佳工艺条件。结果表明,制取笋干的最佳工艺条件为：微波干燥功率6.3 W/g、微波干燥时间60 s、热风干燥温度65 ℃。在此条件下得到的笋干感官评分85.6、总干燥时间200 min、复水比6.17,干制品色差ΔE* 19.99、复水制品色差ΔE* 13.92、干制品硬度19 511.23 g、复水制品硬度20010.71 g,该工艺研究结果可为笋干产业化发展提供理论支持。     

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.     

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.     

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.     

Analysis of benzo[a]pyrene in spiked fatty foods by second derivative synchronous spectrofluorimetry after microwave-assisted treatment of samples

A simple, rapid and inexpensive method has been developed for the determination of benzo[a     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. II: Certification study

This paper describes the second part of a project undertaken to develop certified mussel reference materials for paralytic shellfish poisoning toxins. In the first part two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin and decarbamoyl-saxitoxin in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the certification exercise. Fifteen laboratories participated in this certification study and were asked to measure saxitoxin and decarbamoyl-saxitoxin in rehydrated lyophilized mussel material and in a saxitoxin-enriched mussel material. The participants were allowed to use a method of their choice but with an extraction procedure to be strictly followed. The study included extra experiments to verify the detection limits for both saxitoxin and decarbamoyl-saxitoxin. Most participants (13 of 15) were able to meet all the criteria set for the certification study. Results for saxitoxin.2HCl yielded a certified mass fraction of <0.07 mg/kg in the rehydrated lyophilized mussels. Results obtained for decarbamoyl-saxitoxin.2HCl yielded a certified mass fraction of 1.59+/-0.20 mg/kg. The results for saxitoxin.2HCl in enriched blank mussel yielded a certified mass fraction of 0.48 +/- 0.06 mg/kg. These certified reference materials for paralytic shellfish poisoning toxins in lyophilized mussel material are the first available for laboratories to test their method for accuracy and performance.     

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.