水分含量对大米淀粉糊化和回生的影响

用差示扫描量热仪和动态流变仪对不同水分含量的大米淀粉糊化、短期回生和长期回生特性进行了研究。试验结果表明：水分含量越低，大米淀粉越难糊化。水分含量低于50％时，常压下难以使大米淀粉完全糊化。对于大米淀粉的短期回生，水分含量越低，短期回生速度越慢，淀粉凝胶达到稳定的时间越长。对于大米淀粉的长期回生，水分含量60％时，大米支链淀粉最易重结晶，淀粉体系长期回生速度最快。直链—脂类复合物的解体温度随着水分含量的降低而升高。     

初始水分含量与温度对油炸香蕉片贮藏稳定性的影响

为研究油炸香蕉片在不同贮藏条件下的贮藏特性,采用静态平衡将样品水分稳定到高、低两种初始水分含量,分别贮藏于0、25、37 ℃的避光环境,通过测定过氧化值、酸值、茴香胺值和介电常数等指标评价油炸香蕉片贮藏期间的氧化状况。结果表明,相同的贮藏温度和时间条件下,高初始水分含量油炸香蕉片的过氧化值、酸值、茴香胺值、介电常数均高于低初始水分含量的样品,降低油炸香蕉片的初始水分含量可以提高其贮藏稳定性。高初始水分含量油炸香蕉片的过氧化值随贮藏时间的延长而升高,低初始水分含量样品达到峰值后逐步降低;样品的酸值、茴香胺值在贮藏期间均升高;高初始水分含量样品介电常数在贮藏期间变化不大,低初始水分含量样品介电常数随贮藏时间的延长,整体呈上升趋势。     

莲藕园子及低脂藕片加工与保藏

研究了莲藕园子和低脂藕片的水分含量。水分活度、脂肪含量以及贮藏过程中制品的脂肪氧化值。结果表明：油炸莲藕圆子及低脂藕片的水分活度都在 ０． ９～０． ９４之间，脂肪含量在 ２２％以下，且低脂藕片的脂肪含量较一般油炸制品的低２０％左右。复合铝箔袋包装能减缓脂肪的氧化。上述制品的保鲜期以二个月较为适宜。     

饼干水分快速测定仪

饼干水分含量一般要求在5％以下。水分过高容易发霉变质,过低则减少收率增加成本。可是长期以来由于没有简便快速的检定方法,在生产过程中一直未能加以控制。 测量水分的方法大致可分为以下几类:     

水分对米胚芽贮藏性的影响

杂交米胚芽的呼吸强度随着水分含量的提高而增强，含水量达到7．6％时，胚芽的呼吸强度激剧增强。杂交米胚芽的临界水分为7．6％，含水量高的米胚芽在贮藏中的总酸度高、品质差，因而贮藏性差。     

泰莱公司推出新型超干淀粉产品线

近日泰莱公司宣布推出两款超干淀粉产品：MERIZET^RI16和MERIzET回118，从而扩大其原淀粉的产品种类。这两款超干淀粉均为低水分产品，水分含量分别为5％和7％。     

试谈成熟度较差、含水率偏高籽棉的加工方法

籽棉含水的高低、成熟程度的好坏，对轧花的产质量影响很大。一般情况下，籽棉成熟度好，含水率低，轧花的产量高，轧出的皮棉含杂低、疵点少，质量好；而成熟度较差、含水率高的籽棉，不但轧花产量低，而且轧出的皮棉含杂多、疵点高，质量差。所以很多资料和教课书上都谈到付轧籽棉必须掌握适宜的含水率。经验认为适宜的水分为7－10％，而水分在7－8％时，轧花产量高，皮棉质量好，低于或高于这个指标，都将影响皮棉的产量和质量。本将侧重谈谈成熟度较差、水分偏高籽棉加工方法问题。     

生物质锅炉自动化控制技术的应用与分析

生物质能是地球上最普遍的一种可再生能源,开发利用潜力巨大,具有CO2零排放特性,是潜在的可再生能源资源,生物质能转化为电能,传统上大多采用直接燃烧的方法,即采用蒸汽循环方式生物质燃料和其他化学燃料相比,最重要的不同点是：燃料特性的多变性,高水分和低氮、低硫含量在燃烧过程中,必须考虑燃料中的水分：高水分的生物质燃料在燃烧之前需要消耗能量来使其干燥,所以水分高会时降低燃烧效率,使锅炉的效率随着水分含量而变化、当燃料水分含量超过40％时,将会使锅炉效率大大降低,生物质锅炉使蒸汽可在啤酒行业中推广应用.     

高水分蒸坯对浸出棉籽毛油品质的影响

在实验室模拟高水分蒸坯过程,研究蒸坯水分、蒸坯温度、蒸坯时间等因素对浸出棉籽毛油磷脂和游离棉酚含量的影响,并采用正交试验对高水分蒸坯工艺进行优化.结果表明,蒸坯水分20％,蒸坯温度95℃,蒸坯时间65 min,可以将棉籽毛油中磷脂含量降至0.87％,游离棉酚含量降至0.075％,有效改善了浸出棉籽毛油的品质.     

正交试验在乳粉水分控制中的应用

全脂加糖乳粉的水分含量,国家标准规定特级品不得高于2.5％,而乳粉中水分含量的最佳范围是在1.88～2.25％之间。我厂1986年生产的全脂加糖奶粉特级品率只为93％,造成产品特级品率低的主要原因是产品水分指标不稳定,而产品水分含量的大小取决于工序中对半成品水分的控制。由统计表(表1)中可看出,乳粉水分波动幅度很大,大部分偏高,其原因就在于只是事后把     

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.