响应面法优化纳米SiOx /蛋清蛋白复合膜的制备工艺

以蛋清蛋白为原料,固定纳米SiOx的添加量,用流延法制备分散均匀的纳米级复合膜。采用单因素试验和响应面分析法,优化了复合膜的制备工艺。以蛋清蛋白添加量、增塑剂添加量、增强剂添加量和交联剂添加量为试验因素,以拉伸强度、断裂伸长率及水蒸气透过系数为响应值,建立了拉伸强度、断裂伸长率及水蒸气透过系数的回归模型,优化的工艺条件为蛋清蛋白添加量8g/100mL、增塑剂添加量3.09g/100mL、增强剂添加量0.55g/100mL、交联剂添加量0.71g/100mL,在此条件下复合膜各性能的预测值分别为3.569MPa、59.784%、5.367g·mm/(m2·d·kPa),验证值为(3.492±0.183)MPa、(58.300±2.415)%、(5.570±0.077)g·mm/(m2·d·kPa),与之接近,优化结果可靠。     

响应面法优化超声波处理纳米SiO_x/蛋清蛋白复合膜液的制备

目的:以蛋清蛋白为原料,制备纳米SiOx/蛋清蛋白复合膜,研究超声波处理复合膜液对膜性能的影响。方法:以超声功率、超声时间与间歇时间比、工作时间为试验因素,以拉伸强度、断裂伸长率、水蒸气透过系数及透油系数为响应值,采用单因素试验和响应面分析法,优化超声波处理复合膜液的制备条件。结果:建立了拉伸强度、断裂伸长率、水蒸气透过系数及透油系数的回归模型,优化的超声处理条件为超声功率205.67W、超声时间与间歇时间比1.13:1、工作时间23.32min,在此条件下复合膜各性能的预测值分别为5.141MPa、38.401%、2.719g.mm/(m2.d.kPa)、0.620g.mm/(m2.d),验证值为(5.092±0.146)MPa、(37.560±3.409)%、(2.961±0.083)g.mm/(m2.d.kPa)、(0.667±0.006)g.mm/(m.d),与之接近,优化结果可靠。结论:超声功率和工作时间是影响膜机械性能的主要因素,而超声时间与间歇时间比和工作时间是影响膜阻隔性能的主要因素。     

水解胶原/海藻酸钠/纳米SiOx三元复合膜的制备及性能测试

探讨不同工艺条件下纳米SiOx粒子在水解胶原、海藻酸钠复合体系中的分散情况,在此基础确定了水解胶原/海藻酸钠/纳米SiOx三元复合膜的制备工艺.实验进一步研究了纳米SiOx的加入量对复合膜力学性能、透水气性、抑菌性能的影响.结果表明,适量纳米SiOx可使复合膜抗张强度抑菌性能增加、透水气性减小,在食品保鲜领域具有一定的应用价值.     

纳米SiO_x对大豆分离蛋白膜特性的影响研究

旨在探讨纳米SiOx对大豆分离蛋白膜特性的影响。采用正交实验研究了纳米SiOx的表面改性条件,采用IR和SEM检测了改性效果,并测定了纳米SiOx的添加量对SPI膜特性的影响。结果表明:纳米SiOx最优改性工艺为pH3、0.4gSDS、超声功率200W、35℃下改性30min。0.3%的纳米SiOx可使SPI膜的氧气透过率和抗拉伸强度达到最大、水溶性降至最低;随添加量增大,膜透明度降低。     

壳聚糖复合膜透性的调节及机理研究

为了探究壳聚糖复合膜透性的调节,采用共混的方法制备了纳米SiOx/壳聚糖复合膜,并用X-射线衍射(XRD)和透射电镜(TEM)对复合膜微观结构进行表征,同时考察纳米SiOx添加量、环境温度和相对湿度对透性的影响。结果表明:当纳米SiOx为0.03 g/100 mL时,纳米SiOx分散均匀,与壳聚糖结合紧密,形成强烈的氢键相互作用,对复合膜透性的影响最显著,对呼吸强度的抑制最强;添加等量的纳米SiOx,一定相对湿度下,温度越低,O2透过系数(OP)、CO2透过系数(CP)和水蒸气透过系数(WVP)越低;一定温度下,相对湿度越高,WVP越高;适量纳米SiOx对透光率(LT)的影响较小。可见通过控制壳聚糖膜中纳米SiOx的量,改变环境温度和相对湿度,能对复合膜OP、CP和WVP进行有效调节。     

乳清分离蛋白成膜工艺的研究

以乳清分离蛋白(WPI)为主料,通过添加甘油(增塑剂)和半胱氨酸(还原剂),制备乳清分离蛋白膜.同时,对其制备工艺与性能进行了详细分析与测定,从而确定了成膜最佳工艺为:乳清分离蛋白含量为8%,增塑剂添加量为4%.还原剂的添加量为0.6mmol/L.在此工艺条件下测定乳清分离蛋白膜性能:厚度0.101±0.013mm,透明度0.055±0.005.抗拉强度1165.2±20.8g.断裂伸长率70.06%±1.62%,透H2O性17.13±0.63g/m2·h,透O2性3.60±0.08g/m2·d,透CO2性445.56±5.26g/m2·d.     

绿豆淀粉/PVA复合膜的制备及性能研究

采用流延法,制备一种含绿豆淀粉与聚乙烯醇(PVA)复合膜,并对其性能进行评价。采用单因素实验研究了绿豆淀粉与PVA比例、交联剂、增塑剂等因素对膜性能的影响,并利用正交实验法对绿豆淀粉与PVA质量比、增塑剂用量和交联剂用量进行的优化。结果表明,以绿豆淀粉∶PVA质量比、甘油和乙二醛的质量分数分别为7∶3(g/g)、20%、8%制备的膜的拉伸强度、断裂伸长率、透光率最佳,分别为(17.3±0.25)MPa、112%±2.15%、28.2%±0.23%。     

壳聚糖/纳米SiOx复合保鲜膜性能衰减的研究

为了研究壳聚糖/纳米SiOx(CTSS)复合保鲜剂性能的衰减,采用流延法制备研究壳聚糖/纳米SiOx复合膜,并分别放置于4、14、24、34、44℃恒温环境中24 h,测定其pH值、氧气透过系数(OP)、二氧化碳透过系数(CP)和水蒸气透过系数(WVP)以及对青霉、酵母菌的抑菌性;同时,在4℃条件下,用CTSS和CTS分别涂膜处理草莓,并测定草莓腐烂率。结果表明:低温4℃贮藏10 d后,CTSS膜处理的草莓比CTS膜组腐烂指数降低了21.4%;纳米SiOx/壳聚糖复合膜随着放置温度的提高,pH值上升;复合膜OP、CP和WVP增大,44℃比4℃的OP、CP和WVP分别增加了13.02、27.54、25.56 mg/cm2·d;对酵母、青霉的抗菌性能减弱;壳聚糖/纳米SiOx复合膜对气体分子的通透阻力减小,从而导致壳聚糖/纳米SiOx复合保鲜剂性能降低。     

猪肝蛋白复合膜性能及其在肉品保鲜中的应用

目的:开发一种以猪肝为主要原料的新型天然食品保鲜剂。方法:以水溶性猪肝蛋白(WSLP)、盐溶性猪肝蛋白(SSLP)和壳聚糖(CS)制备可食性复合膜,通过测定机械性能、傅里叶变换红外光谱(FT-IR)、微观结构等对可食膜组分之间进行多角度研究,并将其用于猪肉保鲜,通过对比猪肉冷藏过程中理化指标的变化探究复合膜的保鲜性能。结果:随着WSLP和SSLP的加入,可食膜的机械性能呈先升高后降低的趋势,当添加量为40%时膜的性能最佳,其膜厚分别为(0.267±0.001 43),(0.264±0.001 21) mm,拉伸强度分别为(9.63±0.29),(4.43±0.37) MPa,断裂延伸率分别为(58.37±0.90)%,(28.24±0.63)%,均与CS膜差异显著(P<0.05);40%的WSLP和SSLP能最大程度提升膜基质间的相互交联,其制得的复合膜表面光滑平整,微观结构最佳。猪肉冷藏12 d后,40%SSLP复合膜的保鲜性能最佳,其pH、菌落总数、TVB-N值及TBARS值均为最小。结论:40%WSLP和SSLP制得的复合膜各项性能均最佳。     

纳米纤维素添加量及干燥温度对海藻酸钠可食用膜性能的影响

为研究纳米纤维素对海藻酸钠可食用膜的影响,首先通过改变纳米纤维素添加量制得海藻酸钠复合膜液,研究成膜溶液静态流变性能,随后在不同干燥温度下制得复合膜,研究其透光率、水溶性、水蒸气透过率、氧气透过率及红外光谱特性。结果表明:所有膜液均为假塑性流体,且随着纳米纤维素添加量增加,膜液的假塑性程度升高,黏度变大。在相同干燥温度下,随着纳米纤维素含量增加,复合膜的透光率降低,水溶时间变长;50℃干燥制得的膜阻隔性能最佳,纳米纤维素添加量为15%的复合膜比纯海藻酸钠膜的水蒸气透过率下降了28.7%,添加量为5%的复合膜比纯海藻酸钠膜的氧气透过率下降了22.1%;红外光谱表征发现,在加入纳米纤维素后,复合膜官能团吸收峰发生位移,这可能是两者之间发生了氢键相互作用,从而改善了海藻酸钠膜的阻隔性能。     

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.     

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.     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. I: Interlaboratory studies of methods of analysis

This paper describes the first part of a project undertaken to develop mussel reference materials for Paralytic Shellfish Poisoning (PSP) toxins. Two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin (STX) and decarbamoyl-saxitoxin (dc-STX) in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the second part of the project: the certification exercise. In the first study, 18 laboratories were asked to measure STX and dc-STX in rehydrated lyophilized mussel material and to identify as many other PSP toxins as possible with a method of their choice. In the second interlaboratory study, 15 laboratories were additionally asked to determine quantitatively STX and dc-STX in rehydrated lyophilized mussel and in a saxitoxin-enriched mussel material. The first study revealed that three out of four postcolumn derivatization methods and one pre-column derivatization method sufficed in principle to determine STX and dc-STX. Most participants (13 of 18) obtained acceptable calibration curves and recoveries. Saxitoxin was hardly detected in the rehydrated lyophilized mussels and results obtained for dc-STX yielded a CV of 58% at a mass fraction of 1.86 mg/kg. Most participants (14 out of 18) identified gonyautoxin-5 (GTX-5) in a hydrolysed extract provided. The first study led to provisional criteria for linearity, recovery and separation. The second study revealed that 6 out of 15 laboratories were able to meet these criteria. Results obtained for dc-STX yielded a CV of 19% at a mass fraction of 3.49mg/kg. Results obtained for STX in the saxitoxin-enriched material yielded a CV of 19% at a mass fraction of 0.34mg/kg. Saxitoxin could not be detected in the PSP-positive material. Hydrolysis was useful to confirm the identity of GTX5 and provided indicative information about C1 and C2 toxins in the PSP-positive material. The methods used in the second interlaboratory study showed sufficiently consistent analysis results to undertake a certification exercise to assign certified values for STX and dc-STX in lyophilized mussel.