不同电商物流终止温度对鮰鱼冻藏品质变化的影响

目的 研究不同电商物流终止温度下的鱼肉贮藏品质,从而推进农产品电商的发展。方法 将鮰鱼宰杀后进行真空包装,并快速将其冷冻,当中心温度稳定在-18 ℃后取出,进行电商物流模拟,待其到达不同电商物流终止温度（0,4,8 ℃）后,放入-18 ℃中冻藏5个月,每月测定其理化指标（pH值、色泽、汁液损失率、剪切力、三甲胺含量、硫代巴比妥酸（Thiobarbituric acid, TBA）含量、挥发性盐基氮（Total volatile base nitrogen, TVB-N）含量、新鲜度（K值））和蛋白质特性（盐溶性蛋白含量、巯基含量、羰基含量、表面疏水性）。结果 将鮰鱼冻藏5个月后,3组鮰鱼片的汁液损失率、剪切力、羰基含量、表面疏水性、三甲胺含量、TBA值、TVB-N值、K值均显著上升（P<0.05）,盐溶性蛋白含量、巯基含量显著下降（P<0.05）。在冻藏过程中,三甲胺含量、TBA、TVB-N、K值的增长速率为 v8 ℃＞v4 ℃＞v0 ℃。结论 电商物流终止温度分别为0,4,8 ℃的鮰鱼片在冻藏5个月后,持水性下降,肉质变硬,蛋白变性程度升高,新鲜度下降,加工品质大大降低,但均保持在二级鲜度以上,仍具有加工食用价值。此外,0 ℃的电商物流终止温度更有利于抑制鮰鱼片在冻藏过程中的品质劣变,4 ℃次之,8 ℃最差。     

不同冻结速率对毛豆冻藏过程中品质的影响

以毛豆为试材,研究了-35℃鼓风冻结(风速8 m/s)、-35℃静止冻结和-18℃静止冻结三种冻结方式对毛豆冻结温度变化曲线及冷冻毛豆在-18℃冻藏过程中解冻后汁液流失率、硬度、细胞膜透性、丙二醛、叶绿素、维生素C等品质指标的变化,为选择适宜的毛豆速冻方式提供参考。结果表明:-35℃鼓风冻结冷冻速度最快,毛豆通过最大冰晶生成带的时间最短,仅为40 s,而-35℃和-18℃静止冻结所用时间分别为6 min和1 h左右。三种不同冻结方法对冷冻毛豆贮藏过程中解冻后的质构和汁液流失率,及冻藏过程中的细胞膜透性、丙二醛、叶绿素和维生素C含量等指标有显著影响。毛豆冻结过程中冻结温度越低、风速越高,毛豆冻藏过程中的质构、细胞膜完整性和营养成分等劣变速度越慢。-35℃鼓风冻结的毛豆在冻藏过程中品质显著好于-18℃静止冻结,是较好的毛豆冻结方法。     

不同冻藏时间对速冻草莓营养品质的影响

用非破坏快速分析方法-近红外光谱法（NIRs）分析草莓在-18℃条件下冻藏1个月、2个月、4个月和6个月时维生素C、柠檬酸、苹果酸、蔗糖、葡萄糖和果糖等6种营养成分的变化。结果表明冻藏过程中速冻草莓维生素C、柠檬酸和蔗糖含量逐渐降低；苹果酸、葡萄糖和果糖含量逐渐增加。     

高压静电对速冻冬枣解冻品质的影响

利用高压静电解冻的方法,研究不同解冻场强、解冻时间和解冻温度对速冻冬枣解冻品质的影响.结果表明:高压静电解冻效果优于自然解冻,高压静电解冻后,冬枣硬度、含水量、有机酸含量、维生素c含量和可溶性糖含量均维持较高水平,汁液流失较少.适宜的解冻时间和解冻环境温度对解冻冬枣品质也有一定影响,适宜的解冻条件为18℃、100kV/m下解冻40min.     

微冻贮藏对猪肉品质的影响研究

以猪里脊肉为原料,设置稳定的-2℃微冻、4℃冷藏和-18℃冻藏三个低温保藏环境,通过测定细菌总数、挥发性盐基氮、汁液流失率、持水性、pH值和感官评价来对比各温度下猪肉新鲜度及品质的变化。结果表明:稳定的-2℃在15d内能保持猪肉一级鲜度,27d内保持二级鲜度,而4℃保质期仅6d;相比较于-18℃冻藏,-2℃微冻条件下猪肉汁液流失率低,有较好的持水性且感官评价更好。因此微冻技术用于猪肉保鲜是一种有效的保鲜方式。     

冻藏温度对冻结扇贝质量变化和实用贮藏期的影响

采用了EPN值、持水能力、质地特性和感官评定等四种质量指标,对扇贝在－14～－30℃范围的5种不同温度冻藏过程中的质量变化和实用贮藏期进行了测定,结果表明：（1）冻藏温度－18℃与－14℃相比能显著延缓蛋白质的变性速度;（2）冻藏温度－22℃与－14℃相比能显著减小持水能力的降低速度;（3）冻藏温度－25℃与－18℃可以显著地减缓蛋白质变性、持水能力及质地特性降低的速度;（4）冻藏温度－30℃与－25℃相比,EPN值、持水能力及质地特性变化速度无显著性影响。     

鱼糜在冻藏阶段的品质影响因素及控制技术

目的 进一步提高鱼糜在冻藏过程中的品质,提高其产品附加值,满足消费者对高品质鱼糜的要求。方法 介绍鱼糜的物理化学特性和腐败机理,分析冻结时间、冻结温度、冻结速率和冻融循环对鱼糜冻藏阶段品质变化的影响,综述低温液氮速冻、物理场辅助冻结为代表的新型冻结方式和抗冻剂在冷冻鱼糜品质控制中的应用,并对其发展进行展望。结论 在鱼糜冻藏过程中,应综合考虑冻藏时间和冻藏温度的影响,同时尽量减小温度波动,防止冻融循环的发生;为了更好地保持鱼糜的品质,应进一步研究和优化新型冻结技术在鱼糜中的应用,并探究新型抗冻剂和复合抗冻剂的可行性,以期实现产业化应用。     

四种低温储藏条件对橙汁品质的影响研究

研究了巴杀橙汁在较高温冷藏环境(8℃)、较低温冷藏环境(4℃)、冰温(-2℃)以及冻藏(-20℃)四种不同温度下储藏五周的品质变化规律。结果表明:与其他储藏温度相比,冰温条件下储藏的橙汁在可溶性物、挥发性风味物质等与风味相关的指标上更具优势,也就是该条件下储藏的橙汁的风味品质更优。在维生素C的保存方面,冻藏则更具优势。8℃储藏条件下的橙汁在品质上劣于其他三种储藏温度。1)冰温条件下,储藏期间橙汁的可溶性固形物变化最小;检测出的挥发性风味物质种类最多,其中萜烯类、醇类种类最多,醇类和酯类的相对含量最高。2)冻藏条件下,第五周时VC含量最高;检测出的挥发性风味物质中,醛类的相对含量也最高。3)冷藏条件下,较高储藏温度的果汁的可溶性固形物含量变幅较大;检测出的挥发性风味物质中,化合物总数最少,但烯萜类组分的相对含量最高,重要风味贡献物月桂烯、里那醇和柠檬醛的相对含量最低。4)各储藏条件下,橙汁的总酸、pH值和色度的变化差异不显著。     

基于高通量法分析鲐鱼冻藏期间的微生物群落变化

目的 分析不同冻藏时期鲐鱼表面微生物群落的变化,为鲐鱼冻藏期间微生物安全控制提供相关依据。方法 将新鲜鲐鱼冻藏于-18 ℃冰箱中,分别在冻藏前、冻藏40 d与冻藏100 d时取样,采用高通量测序技术提取分析其表面微生物。结果 冻藏鲐鱼样品操作分类单元（Operational taxonomic units,OTU）数量范围为115~266,优化有效序列为38 899~45 012条;其中,样品在冻藏前的OTU数量最高,冻藏100 d时的OTU数量最低,此时样品的Ace,Chao,Shannon等3个指数均值偏低,但Simpson指数较高,可见其菌群种类和丰度较低;同时,嗜冷杆菌（Psychrobacter）和鞘氨醇单胞菌（Sphingomnnas）为样品冻藏前的优势菌群,而在冻藏40 d时不动杆菌（Acinetobacter）也成为样品的主要微生物;当样品在冻藏100 d时,其优势菌群为乳球菌（Lactococcus）和芽孢杆菌（Bacillus）等。结论 鲐鱼样品在不同冻藏时期的菌群组成存在较大差异,表明冻藏时间对菌群组成有明显影响。     

液氮速冻对火龙果块微生物和品质的影响研究

本文以火龙果块为原料,研究了-40℃、-60℃、-80℃和-100℃喷淋式液氮速冻及-18℃冰箱缓冻处理对火龙果微生物和品质的影响,并筛选了最佳液氮速冻温度。结果表明:样品冻结速率随液氮速冻温度的降低而加快,冻结时间由1. 25 min降至0. 367 min,但-100℃出现低温断裂现象;液氮速冻处理对样品的多酚氧化酶有抑制作用,其中,-80℃液氮速冻处理后样品的多酚氧化酶活性降至47. 27%,而缓冻处理后的酶活升高至301. 09%;相比于缓冻处理,液氮速冻处理后的样品的质构保持更好,其汁液流失率在8. 88%～10. 50%之间,而缓冻处理则高达38. 29%;随着液氮速冻温度的降低,样品的可滴定酸、可溶性固形物、总酚、花色苷、抗坏血酸等品质保持更好。所以在不同温度液氮速冻处理中,-80℃对样品的品质保持最佳。     

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.