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排序方式: 共有3308条查询结果,搜索用时 15 毫秒
1.
针对车用柴油酸度等性质测定过程繁琐,采用衰减全反射样品池测定车用柴油的红外光谱,用偏最小二乘法(PLS)建立红外光谱测定车用柴油酸度、密度、闪点和凝点的4个校正模型,验证标准误差分别为0.46 mg/(100 mL),0.77kg/m3,2.60 ℃,2.77 ℃,该方法符合标准方法再现性要求。与标准方法相比,该方法具有无需预处理、操作简单、测量快速、重复性好等优点。 相似文献
2.
C. G. Gwie R. J. Griffiths D. T. Cooney M. L. Johns D. I. Wilson 《Journal of the American Oil Chemists' Society》2006,83(12):1053-1062
The spray-freezing of two food fats, tripalmitin (PPP) and cocoa butter (CB) and mixtures thereof, has been modeled experimentally
using a novel single droplet freezing apparatus configured so that temperature profiles or samples for microstructure analysis
can be obtained. For 2 mm diameter droplets suspended in a cold air flow at temperatures around 2–15°C, initial cooling rates
were on the order of 10 K s−1 and the temperature profiles could be correlated directly to DSC data collected at 20 K min−1, indicating that minimal supercooling of the materials occurred in the droplet form. Microstructure analysis confirmed that
PPP crystallized preferentially in mixtures, and that the surface structure was very sensitive to storage conditions. The
bulk structure was much less sensitive, and the internal microstructure of the PPP droplets revealed distinct nucleation sites,
which were absent from the CB: These persisted in the mixtures up to 50 wt%. X-ray analysis indicated that the fats crystallized
in their more stable forms, namely, β for PPP and Form V/V1 in CB. 相似文献
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Directional solidification studies of gelatinized corn starch-water mixtures were undertaken in order to examine, in situ, the freezing behavior of this food model. The solidification rate was controlled by varying sample cell velocity as it moved from a 25°C hot stage to a -25°C cold stage. While freezing at cell velocities ≤7.5 μm/sec, starch granules were alternately pushed or entrapped by the advancing solid-liquid interface producing a segregated structure consisting of alternating high-starch and low-starch bands. At a cell velocity of 10 μm/sec, the frozen product was homogeneous. The relationship between the solid-liquid interface velocity and segregation behavior was quantified and compared to an existing model of particle-interface interactions. 相似文献
5.
Effect of pretreatments and freezing rate on the firmness of potato tissue after a freeze–thaw cycle
Sergio Carbonell Jorge C. Oliveira & Alan L. Kelly 《International Journal of Food Science & Technology》2006,41(7):757-767
The texture of potato tissue after a freeze–thaw process using different freezing rates and different pretreatments was analysed, in order to select the best strategy for optimum preservation of the textural characteristics of pre‐frozen potato. Ten blanching conditions were tested and a two‐step blanching process with calcium chloride (0.07 g mL?1) proved the most effective in protecting the tissue after a freeze–thaw process (maximum load force around 10–55% of the raw tissue, depending on potato batch, for air‐blast freezing and 20–60% for immersion freezing). Vacuum impregnation at 100 and 400 mbar, even when followed by different pre‐drying treatments to remove excess water, was very detrimental to resistance to a freeze–thaw process (maximum load force below 10% of the raw tissue for air‐blast freezing and below 20% for immersion freezing). Microstructure analysis confirmed better tissue integrity retention with ethyleneglycol immersion freezing instead of air‐freezing. Differences were found between batches with a 6‐month difference in storage time, indicating that the fresher batch was more suitable for freezing. 相似文献
6.
Alfalfa juice was extracted from plants during the graving phases of the first and second crops. The alfalfa juice was dried and solute concentrations were measured periodically during the process using freezing point depression (FPD) as an indicator. Solute/solvent weight ratios were calculated from the freezing point depression of fresh unconcentrated 'uice extracted from both firsc and second crops. At the time of harvest, tie FPD was a function of this ratio. The first and second crops behaved distinctively different during the drying process, with the second having a larger soluce concentration and a greater FPD at a given moisture content. The appearance of preci itate during the drying process and the general1 large FPD makes this materiay a questionable product for drying vitg low temperature processes. 相似文献
7.
介绍了标准型直燃机的分类、原理及长庆至呼和浩特输气管道工程冷冻供热站的设计实例 ,重点论述了标准型直燃机在严寒地区使用的利弊 相似文献
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9.
CdZnTeCrystalGrowthbyVerticalGradientFreezingMethodHouQingrun;WangJinyi;DengJincheng;DuBing,(侯清润)(王金义)(邓金诚)(杜冰);LiMeirongandC... 相似文献
10.