复合酶对草莓出汁率和澄清度的影响

为提高草莓的出汁率和草莓汁的澄清度,该文以新鲜草莓为原料,研究单一酶（果胶酶、纤维素酶、木聚糖酶）和复合酶对出汁率和澄清度的影响。在单因素试验基础上,对复合酶添加量、复合酶质量比、酶解温度、酶解时间进行响应面优化,得到最佳酶解条件,并对酶解的草莓汁进行感官评价。结果表明,果胶酶和纤维素酶具有协同作用,可明显提高草莓的出汁率和澄清度,出汁率从64.16%（对照组）提高到87.38%,澄清度从2.34%提高到72.83%;经响应面优化试验,得到草莓汁最佳酶解条件为复合酶添加量0.17%、复合酶（果胶酶∶纤维素酶）质量比3∶1、酶解温度41℃、酶解时间35 min,此条件下草莓的出汁率为90.84%,草莓汁的澄清度为84.61%;与对照组相比,复合酶组的感官评分最高,整体风味及口感更优,表明果胶酶和纤维素酶可以有效提高草莓的出汁率和澄清度,且所得草莓清汁感官风味更佳。     

草莓澄清汁的加工工艺研究

研究了用低剂量复合果胶酶制备澄清型草莓汁的加工工艺,确定了最佳技术参数。结果表明, 低剂量酶法制取草莓清汁的最佳工艺参数为:复合果胶酶添加量0．015％,酶解温度35℃,草莓汁原始 pH值,酶解90min。此条件下草莓出汁率为81．10％,果汁的透光率达96．1％。     

果胶酶澄清红树莓果酒的研究

探讨果胶酶澄清红树莓果酒的最佳工艺条件。红树莓榨汁后经发酵获得红树莓果酒,然后添加不同量的果胶酶,通过单因素试验研究果胶酶不同添加量、不同酶解温度、不同酶解时间和不同酶解处理pH对红树莓果酒澄清的影响,通过正交试验确定果胶酶澄清红树莓果酒的最佳工艺条件,并探讨果胶酶澄清避免红树莓果酒后浑浊发生的可能性。应用果胶酶澄清红树莓果酒的最佳工艺条件为:果胶酶添加量0.4 mL/L、酶解温度为35℃、pH为3.0、时间为150 min。澄清后获得的红树莓果酒呈亮红色、透明清澈,具有红树莓自然色泽、口味纯正、营养丰富的特点。利用果胶酶澄清红树莓果酒能较好地避免红树莓果酒后浑浊的发生,因而果胶酶用于澄清红树莓果酒具有应用前景。     

果胶酶对树莓出汁率影响的研究

文中研究了果胶酶对树莓出汁率的影响.通过单因素试验和正交试验研究了果胶酶添加量、酶解温度和酶解时间对树莓出汁率的影响.结果表明,最佳的酶解条件为果胶酶添加最0.07％,温度45℃,时间3.5h.在此条件下树莓汁可保持原有有效成分.     

果胶酶酶解桑葚和杨梅果汁工艺研究

试验以桑葚、杨梅鲜果为原料,打浆后在果浆的自然pH值下,加入果胶酶进行酶解处理,通过优化加酶量、酶解温度和酶解时间,考察果胶酶对桑葚、杨梅果浆酶解效果的影响。经单因素实验,确定桑葚、杨梅果浆酶解的最佳工艺条件。通过试验结果可知桑葚果浆的最佳酶解条件为:果胶酶用量120mg/kg,酶解温度40℃,酶解时间4h;杨梅果浆的最佳酶解条件为:果胶酶用量180mg/kg,酶解温度35℃,酶解时间4h。结果表明在单因素的水平基础上,用果胶酶对桑葚、杨梅浆果进行酶解,酶解效果较好,果汁出汁率高,澄清度较好。     

果胶酶提高葡萄出汁率及色泽的影响

研究用果胶酶提高葡萄出汁率的方法及果胶酶对葡萄汁色泽的影响.通过单因素与正交试验分析酶添加量、酶解温度和酶解时间对葡萄出汁率的影响,结果表明：最佳工艺条件为：果胶酶用量0.1 mL/kg,酶解温度55℃,酶解时间50 min.     

酶法制取芒果混汁的工艺

芒果破碎前进行热烫处理不但有利于去皮,而且可以使过氧化物酶完全失活。研究结果表明最佳热烫条件为100℃下加热5min。采用纤维素酶、果胶酶和木聚糖酶制备芒果混汁,通过正交实验研究了酶加入量、酶解温度、酶解时间对芒果汁出汁率、浊度、悬浊稳定性以及可溶性固形物含量的影响。结果表明,用酶法制取芒果混汁的最佳酶解工艺为:果胶酶用量0.25%(w/w)、纤维素酶用量0.04%(w/w)、酶解时间70min、酶解温度30℃、自然pH。     

果胶酶对番石榴出汁率的影响

为探索果胶酶对番石榴果浆的出汁率的影响,以廉江本地番石榴为试材,采用单一果胶酶酶解方法,研究果胶酶添加量、酶解温度及酶解时间三个因素对番石榴出汁率的影响。结果表明,酶解的最佳工艺为:酶添加量0.05%、酶解时间4 h、酶解温度为45℃。在此基础上进行验证试验,测得番石榴出汁率为81.54%,相比于未加果胶酶处理的空白试验,番石榴的出汁率提高了13.78%。     

梨果汁加工中酶解工艺的研究

以寒地特色梨为研究对象,在单因素实验的基础上,采取正交实验设计,系统研究了梨果汁最佳酶解工艺条件。研究结果表明:加酶量、酶解温度、酶解时间对梨果汁品质有不同程度的影响;最佳酶解工艺条件为:酶解温度50℃,果胶酶添加量3g/kg,酶解时间2h。     

黑莓山楂复合发酵果酒的研究

将新鲜山楂果制成山楂汁,对澄清果汁的影响因素果胶酶用量和酶解时间进行单因素试验,结果最佳果胶酶浓度为1.0～3.0u/mL.最佳酶解时间为2h.运用正交试验再对酶解中的酶量、酶解时间、酶解温度对出汁率的影响进行了研究,得出最佳条件为果胶酶添加量为0.033%,酶解时间为2h,酶解温度为50%.将制成的山楂汁和黑莓汁配成复合果汁,再进行发酵,并对发酵过程中的酵母添加量、发酵温度、发酵时间进行正交试验,得出最佳发酵条件为酵母量200mg/L,前发酵时间9d,温度25%,并得到最高酒精度为12.16%.     

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.