响应面法优化α-淀粉酶酶解木薯淀粉的工艺及动力学模型研究

以葡萄糖值(DE)为考察指标,在单因素试验基础之上,利用响应面法研究时间、温度及酶与底物比(E/S)对α-淀粉酶酶解木薯淀粉的影响。利用Lineweaver-Burk和Wilkinson统计法求解米氏常数(K_m)和最大反应速度(V_m),并建立相应动力学模型。结果表明:α-淀粉酶酶解木薯淀粉制备葡萄糖的最佳参数为:温度60℃,E/S=0.1 U/mg、时间130 min。在此条件下,DE验证值为(82.91±1.32)%。在pH 6.0,50℃条件下,K_m=12.077 mg/mL,V_m=0.218 mg/(mL·min)。在37~52℃范围内,Ea=44.611 kJ/mol,△H=110.847 kJ/mol。     

响应面法优化荸荠淀粉酶解工艺及动力学研究

以葡萄糖当量值(DE)为考察指标,利用单因素和响应面法对α-淀粉酶酶解荸荠淀粉工艺进行优化,并计算相应酶解动力学参数。结果表明:α-淀粉酶酶解荸荠淀粉优化工艺为:时间88min、温度53℃、E/S=0.12U/mg和p H7.7。在此条件下,验证实验DE为(53.393%±0.899%)。在p H7.0,60℃条件下,Km=47.298mg/m L,Vmax=0.335mg/(m L·min),Ea=11.995k J/mol,△H=71.882k J/mol。     

响应面法优化α-淀粉酶酶解高粱淀粉工艺及动力学研究

以葡萄糖值(DE)为考察指标,利用单因素试验和响应面法研究时间、温度、p H及酶与底物比(E/S)对α-淀粉酶酶解高粱淀粉的影响。利用Lineweaver-Burk和Wilkinson统计法求解米氏常数(K_m)和最大反应速度(V_m),建立相应动力学模型。结果表明:α-淀粉酶酶解高粱淀粉制糖工艺为:时间130 min,温度40℃,p H 7.0及E/S=0.04 U/mg。在此条件下,DE验证值为(38.019±0.226)%。在p H 6.0,50℃条件下,K_m=28.888 mg/m L,V_m=0.156 mg/(m L·min)。在30~50℃范围内,E_a=4.448 k J/mo L,ΔH=65.187k J/mol。该研究为高粱淀粉工业制糖提供理论依据。     

响应面法优化甘薯淀粉酶解工艺及动力学模型研究

研究甘薯淀粉的α-淀粉酶酶解工艺及动力学。以葡萄糖释放率为考察指标,研究酶解时间、酶量、淀粉浓度、p H值及酶解温度对α-淀粉酶酶解甘薯淀粉的影响,利用单因素和响应面法优化酶解工艺。通过Lineweaver-Burk和Wilkinson统计法求解米氏常数(Km)和最大反应速度(Vm),建立相应动力学模型。结果表明:α-淀粉酶酶解甘薯淀粉最优参数为:时间40 min,温度60℃,p H 5.0,酶量0.6 U/m L和淀粉质量浓度5 mg/m L,在此条件下,验证值为(50.676±0.294)%,n=5,RSD=0.519%。在p H 6.0,50℃条件下,活化能(Ea)=31.986 k J/mo L,Km=0.988 mg/m L,Vm=0.107 mg/(m L·min)。     

马蹄风味果酒的酿造工艺研究

以新鲜马蹄全果为原料,研究马蹄果酒酿造过程中的酶解和发酵工艺。探究淀粉酶添加量、纤维素酶添加量、温度、pH值、时间和料液比对酶解液透光度、总糖含量的影响;探究酒曲的添加量、温度、初始糖度和pH值对酒精发酵品质的影响。正交试验结果表明,马蹄浆酶解最优条件为:淀粉酶添加量0.4%,纤维素酶0.015%,酶解温度60℃,酶解时间30 min;发酵最佳工艺条件为:果酒酒曲添加量0.5%,温度30℃,初始糖度24%,pH 6.0。     

薏米酒发酵前淀粉液化及糖化条件的优化

以薏米为原料,以葡萄糖当量值(DE值)为评价指标,对薏米酒微生物发酵前淀粉液化及糖化工艺进行研究,考察酶添加量、pH值、温度、时间对DE值的影响。结果表明,最优的液化工艺条件为α-淀粉酶添加量2.0%、pH6.5、液化温度60℃、液化时间3.0h;糖化最优工艺条件为糖化温度55℃、pH4.5、糖化酶添加量2.5%、糖化时间2.5h。在此条件下,最终水解液的还原糖含量和DE值分别达到6.87g/100mL和76.4%。     

原料前处理对玉米浆酶解效果的影响及酶解工艺优化

玉米浆加工前预处理可解决溶解性不佳、易老化等问题,提高其加工特性、加工产品的感官品质及营养吸收率。该研究以玉米为原料,通过单因素及响应面优化试验,得到不同预处理方法对玉米浆后续酶解效果的影响,以及玉米浆酶解最佳工艺条件。结果表明,预处理选择膨化工艺,中温淀粉酶酶解条件：料液比为1∶5（g/mL）、酶添加量0.4%、酶解温度70℃、酶解时间60 min,此条件下制得的玉米酶解物可溶性固形物含量大于13 g/100 mL,原料利用率大于40%。在此基础上,以葡萄糖当量（dextrose equivalent,DE）为指标进行响应面优化试验,得到玉米浆最佳酶解条件：采用膨化玉米糁为原料,料液比1∶5（g/mL）,中温淀粉酶添加量0.45%、酶解温度70℃、酶解时间80 min,葡萄糖淀粉酶作用pH值为4、酶添加量0.2%、酶解温度70℃、酶解时间60 min,最终酶解产物的DE值高于58%。     

机械酶法制备柑桔果皮低甲氧基果胶的工艺研究

研究以超临界二氧化碳萃取精油等化合物后的桔皮为原料,运用机械和酶法相结合制备低价氧基果胶,采用响应面试验设计,以酯化度DE值为响应值,考察了时间、酶添加量、温度和pH对DE值的影响。结果表明:4个因素对酯化度DE值的影响大小依次为:酶添加量>温度>时间>pH。通过对模型进行分析,得出最佳工艺条件为:时间55.62 min、酶添加量6.69 mL、温度40.38℃、pH4.38,在此条件下,酯化度DE值为41.55,为了实际操作的可行性,在优化条件的基础上,将工艺参数修正为时间为55.5 min、酶添加量6.70 mL、温度40.5℃、pH4.38,得实际酯化度DE值为42.03,回归方程的预测值和试验值无显著性差异,所得回归模型拟合情况良好,能很好地反应实际情况。     

以机械活化玉米淀粉为原料酶法制备低DE值麦芽糊精

以机械活化玉米淀粉为原料制备低DE（Dextrose Equivalent）值麦芽糊精,通过单因素实验研究了机械活化时间、反应时间、反应温度、酶添加量、底物浓度、pH对产品DE值的影响,并在此基础上进行了正交实验。结果表明,经机械活化预处理后的淀粉酶解反应活性明显提高,酶解速度加快,酶解时间大大缩短,而原淀粉在相同条件下几乎不与酶作用。正交实验确定了制备工艺的最佳条件为：酶添加量3u·g-1淀粉干基,pH6.5,水解温度45℃,底物浓度10%,水解时间4min,按此条件所得的麦芽糊精DE值为2.35%。并用红外光谱和X-射线衍射对麦芽糊精进行了分析。     

小麦淀粉基质脂肪模拟物的工艺优化及其性能研究

研究以小麦淀粉为原料采用酶解法制备脂肪模拟物,以葡萄糖当量(DE)为指标,考察小麦淀粉质量分数、酶添加量、酶解时间、酶解温度等因素对小麦淀粉脂肪模拟物制备的影响及制备脂肪模拟物的特性。在单因素试验基础上进行正交试验,得出最优工艺条件为小麦淀粉质量分数30%、酶添加量0.8 mg/g、酶解温度70℃、酶解时间12 min,在此工艺条件下小麦淀粉的DE值为6.20,其脂肪模拟物的持水性为53.30%。     

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.