热处理对小米蛋白体外消化率的影响

为探究不同热处理方式的小米蛋白质的消化情况,采用胃蛋白酶-胰蛋白酶体外模拟消化法测定蒸制、煮制、挤压处理并经淀粉酶解的小米蛋白消化率。对从小米生粉中提取的醇溶蛋白蒸制、煮制的蛋白消化率进行测定,结果表明,经120 min的胃蛋白酶和胰蛋白酶处理,蒸制、煮制和挤压处理的小米的体外蛋白消化率分别较未处理小米降低了31.00%,17.15%和11.02%。蒸煮的醇溶蛋白消化率也分别降低了35.57%和28.63%。蒸煮对小麦蛋白的消化率有不利影响,挤压处理优于蒸煮处理。蒸煮处理降低小麦蛋白体外消化率可能与醇溶蛋白消化率的降低有关。     

乳清蛋白的体外模拟消化过程及热处理的影响

探讨了乳清蛋白体外胃蛋白酶和胰蛋白酶的消化过程,以及热处理对该消化过程的影响。SDS-PAGE分析结果表明,胃蛋白酶和胰蛋白酶对乳清蛋白的体外消化作用的影响不明显。干热处理(75℃和100℃,1h)几乎不影响乳清蛋白的体外胰蛋白酶消化过程,而在同样条件下,湿热处理能显著提高胰蛋白酶对乳清蛋白的消化作用。乳清蛋白分别经75℃和100℃湿热处理30min后,再由胰蛋白酶消化8h,其氮释放率分别达到82.1%和91.3%,而未湿热处理的氮释放率仅为66.7%,表明不同热处理方式对乳清蛋白的体外消化过程产生不同的影响。湿热处理能有效地提高乳清蛋白的消化速率,且湿热处理温度越高,乳清蛋白的体外消化速率越快。     

不同预处理对蚕蛹制备呈味基料风味的影响

以鲜蚕蛹为原料,采用漂烫灭酶、脱衬模拟、脱衬模拟+烘干三种方式对原料进行处理,通过酶解及美拉德反应制备蚕蛹呈味基料,研究不同处理对蚕蛹的脂肪酸、酶解产物的水解度及氨基酸、美拉德反应产物的感官风味等指标的影响。结果表明,三种处理方式均能提高蚕蛹呈味基料的感官风味,但不同处理方式的风味存在不同程度的差异。其中漂烫灭酶处理的产物风味最好,其脂肪酸组成及含量变化不大,酶解液水解度最高(23.88%),肽类鲜甜味氨基酸占总鲜甜味氨基酸的比例亦在三种处理方式中最高(高达76.90%),酶解液美拉德反应产物的肉香味有所增加,苦味和蚕蛹本身的腥臭味均被除去,共鉴定出挥发性风味化合物26种,其中醛类9种、吡嗪类6种、呋喃类3种、其他化合物8种。     

不同热处理燕麦片风味物质分析

为了研究不同热处理对燕麦片风味的影响,应用电子鼻检测经微波、焙烤、蒸煮处理的燕麦片风味,运用主成分方法进行分析,同时采用固相微萃取-气质联用仪对不同处理的燕麦片风味物质进行定性定量分析。结果表明:电子鼻可较好区分不同热处理的燕麦片,第一主成分贡献率为61.33%,第二主成分贡献率为23.19%,足够收集全部传感器信息。经不同处理的燕麦片共鉴定出61种挥发性风味成分,仅6种为相同挥发性成分,表明不同热处理对燕麦片风味成分影响较大。未处理燕麦片主要风味为烯类(37.78%)、醛类(14.30%)、萘类(14.16%),微波和蒸煮处理燕麦片均产生了较多的醛类,分别占总挥发性成分的62.05%和80.65%,焙烤处理除了产生较多醛类(33.95%),还生成较多的吡嗪类(38.82%)与嘧啶类(20.12%),呈现了浓郁的烤香味。     

热处理对过氧自由基氧化米糠蛋白体外胰蛋白酶消化性质及消化产物抗氧化性的影响

选用不同浓度的2,2’-盐酸脒基丙烷(2,2’-azobis (2-amidinopropane) dihydrochloride,AAPH)在有氧条件下热降解生成的过氧自由基氧化米糠蛋白,再通过95℃水浴处理氧化米糠蛋白,研究热处理对过氧自由基氧化米糠蛋白体外胰蛋白酶消化性质及消化产物抗氧化性的影响。结果表明:随着AAPH浓度的增加,过氧自由基氧化米糠蛋白体外胰蛋白酶消化率、初始消化速率、消化产物分子质量分布在500～1 500 u的肽含量、消化产物清除ABTS~+·、·OH、O~-_2·能力和还原能力均先上升后下降,消化产物清除DPPH·能力和金属螯合能力先不变后下降;而热处理后,氧化米糠蛋白体外胰蛋白酶消化产物金属螯合能力先上升后下降,ABTS~+·清除能力和还原能力先不变后下降。同未热处理相比,热处理显著提高了相同氧化程度下米糠蛋白体外胰蛋白酶消化率、初始消化速率以及消化产物抗氧化性。表明过氧自由基氧化会改变米糠蛋白体外胰蛋白酶的消化性质,而热处理可以改善相同氧化程度下米糠蛋白体外胰蛋白酶的消化率和消化产物的抗氧化性。     

蒸煮时间对黄豆酱风味的影响研究

采用顶空固相微萃取-气质联用(HS-SPME-GC-MS)技术分析不同蒸煮时间(5,8,10,15min)对黄豆酱中挥发性风味物质的影响,并结合感官评价对其风味进行综合分析。结果表明:不同的发酵酱共检测出25种不同的挥发性化合物,其所含挥发性物质的种类相似,相对含量有较为明显的区别,包括酯类6种、酸类2种、醛类5种、醇类2种、酮类3种、含氮化合物1种、烃类5种、其他化合物1种。其中,经过蒸煮10min黄豆酱的酯、醛、醇、酸等主要香气化合物含量较多,具有更浓郁的香气。感官评价实验中,结合色泽、香气、滋味和体态,表明经过蒸煮时间为8min时,黄豆酱的感官性状最佳。     

不同处理方式对蓝蛤提取液核酸类物质及其风味的影响

为探讨不同处理方式对蓝蛤提取液核酸类物质及其风味的影响,研究了不同加热温度(60 ℃、70 ℃、80 ℃、90 ℃和100 ℃)、超声和超高压对蓝蛤提取液氨基酸态氮含量、电子鼻电子舌评价、核酸含量、核苷酸含量及挥发性风味成分的影响。结果表明:超声处理时蓝蛤提取液氨基酸态氮含量最高。电子鼻结果显示各处理组提取液挥发性风味差异明显。电子舌表明不同处理方式得到的蓝蛤提取液味觉差异主要体现在苦味、丰度和鲜味。不同处理方式下蓝蛤提取液的核酸和核苷酸含量差异显著(P<0.05)。顶空固相微萃取-气质联用技术(HS-SPME-GC-MS)分析表明,60 ℃、70 ℃、80 ℃、90 ℃和100 ℃热处理得到的蓝蛤提取液中分别鉴定出25种、24种、26种、28种和28种挥发性化合物,超声和超高压处理得到的蓝蛤提取液中分别鉴定出28种和12种挥发性化合物。     

采用HS-SPME-GC-MS分析棕榈油热处理过程中挥发性成分变化

采用顶空固相微萃取与气相色谱质谱联用技术(HS-SPME-GC-MS)对棕榈油(24℃)热处理过程(180℃)中挥发性成分变化进行分析。结果表明:热处理前后的棕榈油中共鉴定出63种挥发性化合物,包括醛类、醇类、酸类、酮类、烃类和杂环类;棕榈油中挥发性成分种类随加热时间的延长呈先增多后减少趋势;经热处理后,棕榈油中挥发性成分种类以醛类和烃类为主,且醛类物质含量最高,加热12 h后达80.413%;此外,1-辛烯-3-醇、己酸、2-十五烷酮和2-戊基呋喃的检出表明棕榈油中亚油酸发生了氧化分解,其变化趋势表明棕榈油随加热时间延长氧化劣变程度加深,油脂品质劣变加重。     

加热处理对大豆乳清中胰蛋白酶抑制剂活性以及大豆乳清蛋白体外消化率的影响

采用胃蛋白酶-胰蛋白酶两步体外消化法测定了加热对大豆乳清蛋白的体外消化率的影响。与没有经过加热的对照蛋白相比,适当的加热处理可以提高蛋白的体外消化率,80℃,10min处理的体外消化率达到最高。加热对抑制剂的破坏是正相关,加热处理的程度越高,胰蛋白酶抑制剂活性降低的百分比就越大。1000℃,50min处理以及120℃,8min处理可以将其活性降低到90％以下,达到充分消除豆制品中抗营养因子的目的。     

红烧猪肉工艺优化及其挥发性风味成分的分离与鉴定

基于模糊数学感官评价法优化红烧猪肉制作工艺参数(焯水时间、焖焅温度、焖焅时间)。采用固相微萃取(SPME)预处理与气相色谱-质谱(GC-MS)联用技术相结合对红烧猪肉中挥发性风味成分进行分离鉴定。结果表明,红烧猪肉的最佳工艺条件为:焯水时间3 min,焖焅温度100℃,焖焅时间2.5 h。对SPME萃取参数(平衡时间、萃取温度、萃取时间)进行优化,确定较佳的萃取条件是:水浴温度60℃下平衡10 min,萃取35 min。通过SPME-GC/MS共鉴定出60种挥发性风味成分,包括醇类10种、醛类10种、脂肪烃类15种、酯类5种、酮类7种、含S、N化合物7种及其它化合物6种。红烧猪肉挥发性风味成分中醛类比例最高(24.68%),其次含S、N化合物(20.99%)、脂肪烃类(19.57%)、醇类(16.88%),而酯类、酮类及其它化合物比例较低(10%),其中己醛(0.72μg/g)、柠檬烯(0.51μg/g)、硫化丙烯(0.51μg/g)为含量较高的化合物。     

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.