加工工艺对糙米乳稳定性及主要品质的影响

为解决储存过程中糙米乳淀粉、蛋白质、纤维素沉淀及脂肪等小分子的上浮,导致的产品分层及沉淀问题,采用酶解、离心、胶体磨或均质等工艺处理来改善产品的组织状态,提高其稳定性。经α-淀粉酶、糖化酶、纤维素酶及蛋白酶酶解后,糙米乳的稳定性得到改善;采用卧式螺旋卸料沉降离心机对糙米乳进行离心处理,其最佳离心参数为主机频率38 Hz,副机频率35 Hz;随着胶体磨处理时间的延长,糙米乳悬浮稳定性逐渐增加,离心沉淀率逐渐降低,当处理时间超过3 min后,糙米乳的悬浮稳定性与离心沉淀率变化放缓;在20 MPa压力下均质2次,糙米乳的悬浮稳定性与离心沉淀率均达到最佳;且糙米乳营养全面、滋味良好,其理化指标符合QB/T 4221—2011《谷物类饮料》的要求。     

牛乳蛋白质的性质及应用

在乳品工业中非常关心的一个实际问题是乳蛋白质在乳中存在状态，蛋白质胶粒的稳定性（分散，乳化）不稳定性（凝聚，沉淀）等现象，都直接与乳蛋白质的性质有关，本文论述了乳蛋白的分类，性质及应用，对乳品加工具有一定的指导意义。     

影响羊奶乳脂肪稳定性因素的研究

对崂山奶山羊乳中乳脂肪的稳定性进行了研究,通过测定离心前后吸光度比值(稳定性系数)分析了温度、超高压、乳化剂、蔗糖、柠檬酸及钙离子浓度对生鲜原料乳中乳脂肪稳定性的影响。结果表明,羊乳中乳脂肪经加热处理后在75℃时稳定性最高;经超高压处理后稳定性降低;当蔗糖添加量为1%,蔗糖酯的添加量为0.12%时稳定性最高;添加柠檬酸后乳脂肪的稳定性明显下降;一定量的钙离子能够增加乳脂肪的稳定性,但浓度增加后反而降低乳脂肪的稳定性。通过研究不同因素对羊乳中乳脂肪稳定性的影响为羊乳在实际生产中提出了一些具有指导意义的意见和建议。     

羊初乳免疫球蛋白(IgG)稳定性的研究

研究了酸、碱、糖、加热对羊初乳中免疫球蛋白（IgG）稳定性的影响.结果表明,IgG在pH值为5.0～10.0范围内比较稳定,在pH值为低于5.0条件下,随pH值降低,变性率剧烈上升;在加热或pH2.0的环境下,糖醇化合物对IgG具有保护作用,随着糖类浓度的升高IgG的变性率降低,其中蔗糖、果糖、麦芽糖的效果较好,葡萄糖、乳糖的效果较差;羊初乳中IgG对加热比较敏感,随着加热温度的上升,其变性率增大.于55℃加热30 min,变性率为25.5%;于65℃加热30 min,变性率为38.1%;于75℃加热7 min时,变性率已达100%;于85℃加热2.0 min时变性率也已达100%.     

牛羊乳蛋白质粒度对其热处理沉淀率的影响

研究牛羊乳蛋白质粒度大小对其热处理沉淀率的影响。采用离心沉淀、原子力显微镜、激光粒度仪和SDS-PAGE分析热处理后(95℃,15 min)牛羊乳蛋白质沉淀率、表面形貌、牛羊鲜乳蛋白质粒度和酪蛋白组成。结果表明:羊乳热处理后沉淀率显著高于牛乳(p0.05);羊乳蛋白质粒子明显大于牛乳,其蛋白质热处理片状凝聚程度(35 858.15 nm~2)大于牛乳(18 215.18 nm~2);鲜牛乳蛋白质粒度大小主要集中在1 nm以下,鲜羊乳蛋白质粒度在1 nm以下相对较少,主要分布在1~1 000 nm之间;牛羊鲜乳酪蛋白主要有β-酪蛋白和αs1-酪蛋白两种,相对分子质量分别为34 000和26 000左右。牛乳的热稳定性高于羊乳;蛋白质粒度大小是影响其热稳定性的直接因素;原子力显微镜结合激光粒度仪是分析乳蛋白粒度的有效手段。     

抑制α-葡萄糖苷酶活性鹰嘴豆乳制备条件优化

本文以鹰嘴豆为原料,以蛋白质得率及蛋白质含量为指标优化其浸泡与制浆条件,以α-葡萄糖苷酶抑制率为指标优化酶解时间,最后以离心沉淀率为指标,通过单因素实验和正交实验复配稳定剂,优化鹰嘴豆乳的稳定性,得到抑制α-葡萄糖苷酶活性的鹰嘴豆乳。研究发现,鹰嘴豆粉浸泡时间为7 h,料水比为1:10 (g/mL)时,蛋白质得率较高,为97.89%,且鹰嘴豆乳的蛋白质含量为2.01%;鹰嘴豆乳在80 ℃糊化40 min,采用高温α-淀粉酶(终浓度7 kU/kg)95 ℃液化40 min,糖化酶(终浓度200 kU/kg)60 ℃糖化6 h后,对α-葡萄糖苷酶抑制率最强,为78.08%;添加0.1%卡拉胶,0.08%瓜尔豆胶、0.08%黄原胶后,鹰嘴豆乳的稳定性最佳,此时鹰嘴豆乳的离心沉淀率为18.86%。     

常见热杀菌方式对关中羊乳品质的影响

采用5种常用热杀菌方式处理关中羊乳,即低温长时巴氏杀菌(65 ℃/30 min)、高温短时巴氏杀菌(72 ℃/15 s)、超巴氏杀菌(95 ℃/5 min)、高温高压灭菌(121 ℃/20 min)和超高温瞬时灭菌(137 ℃/7 s),在测定蛋白沉淀率、酒精稳定性、pH、红度值、粘度和脂肪球变化基础上,结合内源荧光光谱和聚丙烯酰胺凝胶电泳(SDS-PAGE)分析,探究热杀菌处理对关中羊乳品质的影响。结果表明,高温高压灭菌羊乳蛋白沉淀率最高、酒精稳定性最差、pH明显下降、红度值明显增大,但5种杀菌方式对粘度没有显著影响(p>0.05);羊乳脂肪球经巴氏杀菌和超巴氏杀菌后,表观直径略微增大,而高温高压灭菌和超高温瞬时灭菌,尤其是高温高压灭菌则导致其明显变小;荧光光谱表明,高温高压灭菌羊乳蛋白结构改变最大,内源荧光强度剧烈升高;电泳显示,巴氏杀菌(65 ℃/30 min和72 ℃/15 s)对羊乳酪蛋白和乳清蛋白影响较小,超巴氏杀菌(95 ℃/5 min)乳清蛋白开始变性、聚集或部分降解,高温高压灭菌和超高温瞬时灭菌,尤其是高温高压灭菌则使乳清蛋白明显降解甚至消失,酪蛋白出现聚集和解聚。结果表明,高温高压灭菌和超高温瞬时灭菌,尤其是高温高压灭菌对关中羊乳品质影响较大,超巴氏杀菌影响次之,而巴氏杀菌则对其影响较小。     

乳蛋白质加工过程中影响因素的探讨

介绍了蛋白质是乳中最重要的营养成分,牛乳中蛋白质含量为3．3％左右。阐述了牛乳的加热、原料乳的酸度、异常乳、均质处理及微生物对乳蛋白质的影响。在加工过程中,通过采取相应的措施使牛乳蛋白不受破坏并保持优良的品质,从而在人体内得到高效率吸收。     

褐色调制乳的研制

为了研究褐色调制乳生产工艺参数,本试验以离心沉淀率和感官品质评定为指标,对食用葡萄糖的添加量、褐变时间、蛋白质含量和均质压力及次数进行了筛选优化,并进行实际应用观察产品的稳定性和感官品质。结果表明,最佳工艺参数:葡萄糖添加量为6%;褐变时间为95℃(2 h);蛋白质含量为3.0%;均质条件为65℃,20 MPa,均质2次。产品常温(25℃)时放置30 d时无脂肪上浮及沉淀,组织状态良好。     

产胸苷磷酸化酶短乳杆菌融合菌株的构建及其特性

利用紫外加热灭活双亲原生质体技术对短乳杆菌原生质体进行融合,考察短乳杆菌原生质体制备、再生及融合的影响因素,并对短乳杆菌融合子产酶能力和遗传稳定性进行了研究。结果表明:短乳杆菌在含0.6%甘氨酸发酵培养液培养至对数生长期,2 mg/mL溶菌酶于37℃恒温水浴酶解脱壁2 h,原生质体制备率和再生率可达95%和48%;20 W紫外灯距离20 cm照射50 min,60℃处理短乳杆菌原生质体60 min,原生质体的灭活率几乎为100%;将双亲灭活的原生质体用40%PEG6000,30℃恒温融合10 min,筛选融合子F15并进行5次传代测试其胸苷磷酸化酶活均在1.500 U/mg湿菌体,较亲本酶活提高了50%。     

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.