搅拌型酸奶黏度及持水性测定的研究

以搅拌型酸奶为研究对象,对影响其黏度测定的搅拌方式、搅拌强度、搅拌时间及恢复时间进行了研究,提出了合适的黏度测定条件。同时,选择市场上流行的8种搅拌型酸奶,研究不同离心力与离心时间下酸奶的持水性,并测定其黏度,结果表明:测定酸奶黏度时需施加合适的应力大小与剪切时间使样品均匀,同时在测定前尽量使破坏后的结构得以恢复;黏度总体上与持水性呈现出较高的正相关性,样品的黏度越大其持水性越强;另外,离心力与离心时间明显影响酸奶的持水性,在离心力300 g、离心时间10 min时能有效区分不同样品的持水性,可以用于酸奶持水性大小的评价。     

凝固型酸奶的制备和质量评价

设计了9组凝固型酸乳样品,通过分析增稠剂添加量、乳清蛋白添加量(WPC30)、发酵终止pH值对其感官品质、凝胶强度和持水性的影响,表明增稠剂对凝固型酸奶整体口感、凝胶强度、持水性均有显著性影响,乳清蛋白对凝固型酸奶的持水性有显著性影响.结合颠簸实验数据,建立了增稠剂添加量0.6%,乳清蛋白0.6%,发酵终止pH值为4.4的凝固型酸奶配方工艺,这样的凝固型酸乳的凝胶强度为23 g,持水性为74.04%,可以抵御长途冷链运输中的颠簸性破坏,维待良好的组织状态.     

不同乳蛋白强化对搅拌型酸奶品质特性的影响

以未添加乳蛋白产品的酸奶为对照,研究了不同添加量的乳蛋白产品包括脱脂乳粉(SMP),乳清蛋白浓缩物(WPC),乳蛋白浓缩物(MPC)和凝乳酶干酪素(CS)的对搅拌型酸奶性质的影响,并研究了4℃下贮藏1d,7d和14 d后黏度和持水力的变化.结果表明:比较几种蛋白强化酸奶,加入1％WPC后能够明显提高酸奶黏度,较对照样品提高了376.4％,4℃条件下贮藏14d后各个蛋白强化酸奶的黏度相应的降低；除了CS外,其他几种蛋白强化均可以增加酸奶持水性,其中添加2％WPC后持水性较对照样品增加了12.10％,且随着贮藏时间的延长,WPC强化酸奶的持水性下降；MPC和SMP强化可以明显提高感官品质,尤其是风味;不同蛋白强化后均改变了酸奶的凝胶结构,从而影响了其品质特性.     

超声处理对肌原纤维蛋白凝胶特性和结构的影响

采用超声波技术对猪肉肌原纤维蛋白(MP)进行改性处理,研究超声功率(0, 80, 140, 180和200 W)对肌原纤维蛋白凝胶特性及结构的影响。结果表明,与未经超声处理的肌原纤维蛋白比较,随着超声功率增加,凝胶强度、持水性、持油性及白度均显著升高。超声功率180 W时,经超声处理后的肌原纤维蛋白凝胶表现出较高的凝胶特性,同时扫描电镜观察结果发现,经过180 W超声波处理后肌原纤维蛋白凝胶结构致密、均匀、孔洞小。红外光谱分析表明,超声波处理会改变肌原纤维蛋白的结构。     

枸杞大豆蛋白植物基酸奶理化性质研究

该文旨在以枸杞和大豆分离蛋白为原料制备植物基酸奶，探讨全蔗糖发酵、蔗糖和乳糖混合发酵对植物基酸奶外观、色度、发酵终点pH值、乳清析出率、持水性、微观结构、粒度、凝胶强度、流变学特性的影响，同时以枸杞和脱脂牛奶、全脂牛奶所制备的动物基酸奶为对照，以期为植物基酸奶的研究与开发提供理论基础。研究结果显示，添加枸杞的大豆蛋白植物基和动物基酸奶均能形成稳定的凝胶结构；枸杞大豆蛋白植物基酸奶的白度显著低于动物基酸奶；枸杞大豆蛋白植物基酸奶的持水性、凝胶强度、黏性、黏弹性均低于全脂动物基酸奶，但高于脱脂动物基酸奶。此外，采用蔗糖和乳糖混合发酵可以降低植物基酸奶发酵终点的pH值和乳清析出率，提高凝胶的黏弹特性。     

蛋白质强化对搅拌型酸奶品质特性的影响

为了研究蛋白质强化对搅拌型酸奶品质特性的影响,以脱脂奶粉(SMP)和乳清浓缩蛋白-80(WPC-80)作为蛋白源,研究了强化不同种类及不同含量(2.7%、3.1%、3.5%、3.9%)的蛋白质强化对搅拌型酸奶感官品质、黏度和持水性的影响。结果表明:用SMP和WPC-80强化原料乳的蛋白质均可提高搅拌型酸奶的感官品质、黏度和持水性;比较同种蛋白源、不同蛋白质强化水平制得的搅拌型酸奶,其组织状态变化明显,风味稍有变化,色泽保持不变;酸奶的黏度和持水性都随蛋白质水平的上升而显著提高。SMP强化蛋白质含量至2.7%时,酸奶的感官品质最好;WPC-80含量则在3.5%时,酸奶的感官品质最好。同一蛋白质水平、不同强化蛋白相比较,WPC-80强化酸奶比SMP有更好的感官品质和更高的持水性,而SMP强化则得到更高的黏度值;从感官评定的黏稠度得分和测得的黏度值对比得出,搅拌型酸奶的黏度并不是越高越好,最佳黏度值在537～712mPa.s之间。实验中搅拌型酸奶的最佳蛋白强化配方为WPC-80强化蛋白质含量3.5%。     

酸奶的感官与理化特性和乳酸菌活菌数的相关性

在前期酸奶工艺优化的基础上,对酸奶进行感官评分和理化、微生物检测,对酸奶感官评分与理化、微生物指标之间的相关性进行研究。结果表明:黏度、酸度、乳酸菌活菌数和持水性与感官特性有极显著的相关性,由此提出以黏度、酸度和乳酸菌活菌数以及持水性4个指标来客观评价酸奶品质,为酸奶的研制提供理论依据。     

不同处理方式对柑橘纤维形态结构的影响研究

本研究探讨了三种柑橘纤维[AQ-Plus (1号),Fiber-Star (2号)和在我们的实验室中提取的纤维(3号)]之间基本成分、物理性质(持水性、持油性以及膨胀性)的差异;通过测定柑橘纤维悬浮液的粒径、Zeta电位、表观黏度以及微观结构来探讨高压均质、超声波处理对三种柑橘纤维悬浮液的形态表征的影响。实验结果表明:1号纤维素(38.02±1.61 g/100 g)、半纤维(29.56±0.63 g/100 g)含量较高,持水性(21.58 g/g)、持油性(14.29 g/g)以及膨胀性(27.46 mL/g)较好,2号次之,3号最差;经过30 MPa,60℃高压均质处理,三种柑橘纤维粒径降低,Zeta电位、表观黏度较未处理前显著提升;随着超声波处理时间的增加,三种柑橘纤维的粒径逐渐下降,表观黏度呈现递增的趋势;在0～5min处理过程中,三种柑橘纤维悬浮液Zeta电位绝对值随着超声波处理时间的增加而显著提高,随着超声时间的进一步延长,三种柑橘纤维Zeta电位无显著变化。     

超声辅助凝胶化对鲢鱼糜凝胶特性的影响

为了改善鲢鱼糜凝胶的品质,采用超声波辅助强化,定向考察了超声波输出设备内的声场分布,并通过测定鱼糜凝胶强度、持水率、色度、微观结构等指标研究了超声波条件对鲢鱼糜凝胶特性的影响。结果表明:设备内超声波声场分布与换能器的位置存在显著规律,越靠近换能器的区域,声功率强度值越大;当声功率强度达到0.49 W/cm2及以上时,超声波辅助处理可以提高鲢鱼糜的凝胶强度和持水率,且随着声功率强度的增加,鱼糜凝胶强度和持水率呈增加趋势;超声处理对鱼糜凝胶的白度无显著影响。扫描电镜分析显示,0.85 W/cm2超声处理的鱼糜样品,其致密度和均匀度较对照组更好。     

转谷氨酰胺酶提高酸奶品质的工艺研究

转谷氨酰胺酶可通过其酶促蛋白交联作用而改善酸奶的质构特性,按酶的不同处理方式（反应后灭酶和不灭酶）和不同添加量（0．15,0．25,0．35g／L）进行组合实验,然后测定酸奶的凝胶强度、黏度和贮存黏度、乳清析出率和持水性等指标的变化和综合感官评定．优化了酶的应用工艺及技术参数,即酶的处理方式为反应后不灭酶,酶的适合添加量为0．15g／L。     

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.     

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.     

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.     

Announcing a new international peer-reviewed journal:Food Science and Human Wellness now accepting manuscript submission in English

<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of the