蒸煮袋用溶剂及其迁移的研究

通过改换溶剂减少了高温杀菌后蒸煮袋材料的溶剂残留及迁移.利用溶剂的溶解度参数、沸点、安全性、价格等优选出乙酸甲酯、丙酮2种溶剂.比较厂方用的乙酸乙酯、优选的乙酸甲酯、丙酮3种溶剂的聚氨酯黏合剂的性能和其对蒸煮袋开袋异味的影响.结果显示,改换溶剂对聚氨酯黏合剂的燃烧、外观、密度、固化速度没有明显的影响;综合不挥发物含量、适用期、失重、感官评价几项性能,采用乙酸甲酯为溶剂能够达到剥离强度较高、溶剂残留量最小和无异味的效果.     

高温蒸煮袋干式复合工艺研究

使用干式复合法制备了结构为PET 12μm/Al 9μm/PA66 15μm/CPP 70μm的蒸煮包装袋;优化了聚氨酯胶的涂布量和熟化工艺;考察了复合膜阻隔O2和水蒸气的能力;并检测了复合膜的溶剂残留量.结果表明,该工艺生产的高温蒸煮袋质量较优.     

熟制板栗蒸煮袋包装的设计

采用高温蒸煮袋技术,围绕蒸煮袋的结构及蒸煮袋材料的选择、材料厚度的确定、理论保质期的计算等内容对熟制板栗进行蒸煮袋袋装设计.通过理论分析计算,确定所设计的熟制板栗高温蒸煮袋的透明阻隔层材料为PET12/PVDC15/CPP50、不透明阻隔层材料为:PET12/Al9/CPP50;根据熟制板栗的最大允许透水量、所设计材料透湿系数和厚度,理论估算该高温蒸煮袋的保质期为4年,符合设计要求.     

本期专题：关注高温蒸煮包装——我国高温蒸煮包装现状探析

高温蒸煮袋从1959年在美国研究成功到现在,其产量逐年增加,且品种也走向多样化。为了保证其保质期,对产品外包装的要求就格外严格,耐高温蒸煮袋具有包装持久、储藏稳定、防菌、耐高温杀菌处理等性能,是软罐头最佳的包装复合材料。     

蒸煮袋脱层问题剖析

蒸煮袋是用来包装蒸煮食品的塑料软包装，根据耐温性能不同而分为耐水煮袋(≤100℃)、耐蒸煮袋(121-125℃)和耐高温蒸煮袋(≥135℃)。经过约30min高温杀菌后，蒸煮袋能大大延长食品的保质期，因而蒸煮袋的生产获得了迅速发展。蒸煮袋脱层是指装入食品蒸煮后发生的脱层现象。该问题具有一定的潜伏性，印刷、复合、熟化时就已埋下隐患．但问题一般发生在食品企业使用蒸煮袋时，因而往往给企业造成重大损失。     

高温下纸中Irgacure-184向奶粉迁移行为研究

食品印刷包装纸中的光引发剂Irgacure-184会向食品中迁移,建立了用气相色谱法检测被污染的奶粉中Irgacure-184的方法,并研究了在高温条件下,纸中Irgacure-184向奶粉迁移的行为。结果表明:温度越高,迁移速度越快,越容易在短时间内达到平衡,且总迁移量越大。     

扣肉高温蒸煮异型袋包装设计

采用高温蒸煮袋技术,围绕蒸煮袋的结构及蒸煮袋材料的选择、材料厚度的确定、理论保质期的计算等内容对扣肉蒸煮异型袋袋装设计.通过理论分析计算,确定所设计的扣肉异型高温蒸煮袋的透明阻隔层材料为BOPP25/EVOH16/CPP50、不透明阻隔层材料为BOPP25/Al10/CPP50;根据扣肉的最大允许透水量、所设计材料透湿系数和厚度,理论估算该高温蒸煮袋的保质期为1.6年,符合设计要求.     

蒸煮袋复合材料溶剂迁移性的研究

分析了蒸煮袋复合材料溶剂残留的产生原因,提出了竹碳吸附剂法和替换溶剂法两种解决方案,并通过实验验证了竹碳吸附剂法和替换溶剂法可以有效降低蒸煮袋"异味"问题.     

“软罐头”在肉制罐头食品上的使用逐步扩大

所谓“软罐头”,是指用软质包装容器包装,经过100℃以上高温杀菌后达到商业无菌,可在常温下长期保存的包装食品。其包装材料是由两层、三层或多层不同基材复合而成,是近年来在食品罐头,特别是肉制罐头食品包装中兴起的一种新的包装形式。目前常用于肉制罐头食品包装的软包装材料主要有透明蒸煮袋和铝箔蒸煮袋两种。     

橡胶接触油脂类食品时食品模拟物的选择

目的 研究体积分数为50％的乙醇作为食品接触用橡胶材料及制品的油脂类食品模拟物的适用性,为我国食品接触用橡胶材料及制品标准的修订提供数据支撑.方法 制备含1,4-二苯基-1,3-丁二烯(1,4-diphenyl-1,3-butadiene,DPBD)的阳性橡胶样片,通过迁移实验并结合气相色谱-三重四极杆串联质谱法,测定并比较DPBD在不同的迁移条件下在含油脂真实食品、食品模拟物(体积分数50％的乙醇、植物油)和替代溶剂(体积分数95％的乙醇)中的迁移量.结果 同一个迁移条件下,DPBD在体积分数50％的乙醇中校正前的迁移量大于在火腿肠和午餐肉中的真实迁移量,其在橄榄油校正前的迁移量均大于在对应的4种含油脂食品中的真实迁移量;丁腈橡胶中DPBD在替代溶剂(体积分数95％的乙醇)的迁移量大于在橄榄油的迁移量.结论 对于含油脂食品,现行食品接触用橡胶材料及制品标准中对油脂类食品模拟物(体积分数50％的乙醇)的设定并不完全适用;建议首选橄榄油作为油脂类食品模拟物,当接触食品为火锅底料或者黄油时不建议对结果进行校正,当接触食品为火腿肠或午餐肉时建议对结果进行校正,或选择体积分数50％的乙醇且不对结果进行校正;对于食品接触用丁腈橡胶,可以采用体积分数95％的乙醇作为油脂类食品模拟物的替代溶剂,对乙丙橡胶不建议采用体积分数95％的乙醇作为替代溶剂.     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Analysis of anisotropy of properties on the basis of studies of texture of coarse-grained ingots of thermoelectric materials

An analysis of anisotropy of the properties of a Bi₂Se_0.3Te_2.7 solid solution was carried out using construction of demonstrative surfaces for thermoelectric effectiveness and thermal expansion coefficients. It is shown that the texture is an important factor forming anisotropy of properties and technological fitness of ingots for manufacturing modules. Anisotropy of properties based on the studies of the ingot textures obtained using the float-zone method and Bridgman method (growing thermoelectric plates in a flat cavity) was studied.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.