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阀体结构是高压均质过程影响食品原料超微细化效果的关键。该文应用多物理场仿真软件COMSOL,对新型的短程射流共点交汇对撞阀(简称交汇对撞阀)内流体的剪切、撞击、空化和湍动效应进行分析,并进行纤维素高压射流均质超微细化试验。结果表明,交汇对撞阀内剪切、湍动、摩擦作用更强;阀体内交汇撞击区附近,压力回升利于空泡向内溃灭造成冲击,空化效应更强;与直孔阀相比,阀体出口附近湍动能增加近10倍。经交汇对撞阀处理,纤维素水分散液固形物体积占比升至75%,且电镜观察纤维素微纤直径和长度明显减小。阀体内作用机理分析与试验结果的一致性表明,流体转向、短程射流、共点交汇的阀体设计强化撞击、空化、湍流效应等,从而提升交汇对撞阀的超微细化效果。 相似文献
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目的利用球磨设备对普通食用级马铃薯淀粉进行微细化加工,研究不同微细化条件对马铃薯淀粉微细化效果的影响。方法采用二次正交旋转回归试验对微细化工艺进行优化,通过得到的二次正交旋转回归方程,确定影响微细化结果的各因素的主次顺序依次为:球磨时间、球磨机转速、淀粉液浓度。结果经试验最后确定马铃薯淀粉微细化的最适宜条件为以无水乙醇为球磨介质,球磨时间24 h,球磨机转速350 r/min,淀粉液浓度0.35 g/mL。结论二次正交回归旋转组合试验结果表明,影响马铃薯淀粉微细化工艺的各因素的主次顺序依次为:球磨时间、球磨机转速和淀粉液浓度;最佳条件下得到的淀粉粒度为11.019μm,回归模型预测值偏差为2.7%,预测精度较高。 相似文献
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为了揭示纤维素超微细化处理后的结构和物性变化,利用高压射流技术对两种纤维素微粉(原样、碱处理)悬液进行了湿法破碎,检测了产物微观形态、粒径分布、比表面积以及结晶度的变化。结果表明,高压射流处理(130 MPa,100μm单孔阀,4次)可使原样和碱化(10%NaOH,70℃,1 h)后的纤维素微束直径由原料的5.0〜50.0 pm分别降至0.5〜5.0μm和0.1〜1.0μm,微束长度由原料的20.0〜200.0降至1.0〜10.0粒径分布曲线峰值可由原料的158.0μm降至10.0μm左右;比表面积分别提高3.0倍和5.5倍。碱化处理可降低纤维素无定形区的强度进而降低纤维素的破碎能。纤维素原样经高压射流后结晶度改变不明显;碱化预处理后高压射流处理产物的结晶度小幅度(10%)下降。碱化预处理增强了高压射流处理纤维素原料的微细化程度。 相似文献
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膜液质量浓度对MC/WG可食性复合膜性能的影响 总被引:2,自引:0,他引:2
研究膜液质量浓度对甲基纤维素(MC)/小麦面筋蛋白(WG)可食性复合膜性能的影响。结果表明:MC/WG复合膜的抗拉强度、阻氧性能随着膜液质量浓度的增大而显著提高;断裂伸长率、透光率随着膜液质量浓度的增大而降低;水蒸气透过系数则随着膜液质量浓度的增大先减小后增大,在膜液质量浓度为50g/L时最小。各个质量浓度下的复合膜均可完全溶于水,具有良好的水溶性。综合比较复合膜在不同质量浓度下的性能,MC/WG质量浓度以50g/L为宜。 相似文献
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以漂白竹浆为原料,采用中性2,2,6,6-四甲基哌啶-氮-氧化物(TEMPO)微波氧化预处理,然后在浆浓0.6%下结合超声波处理将竹浆纤维素分离解纤为微纤化纤维素(MFC)。通过表观分散性观察、透射电子显微镜(TEM)、傅里叶变换红外吸收光谱(FI-TR)和X射线衍射仪(XRD)对不同超声时间所制备的MFC的分散特性、形态特征、化学结构、结晶度和晶型结构进行表征分析。结果表明,超声2 h可以得到分散性好、完全透明的MFC,其直径分布均一(5~15 nm),而长度在微米级;超声处理不会改变纤维素的化学结构和晶体类型,但对其结晶度有一定的影响,超声1.5 h其结晶度最高66.97%,超声2.5 h后其结晶度剧烈下降至39.16%。 相似文献
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The use of trimethyl quat cellulose derivatives in hair and skin care products is well established. The introduction of fatty quat groups into cellulose can modify the surface activity and conditioning behaviour. The present study was directed to a coconyl dimethyl quat derivative of cellulose, with an average molecular weight of approximately 100,000. A modified version of the rubine dye test, capable of giving quantitative results, was used to seek information on substantivity and tendency for build-up on hair. The evidence presented indicates that this surface-active cellulose polymer exhibits a plateau maximum value for substantivity which is achieved by a single conditioning treatment as an aqueous solution with a concentration of 1% or higher. The same plateau value can be approached by successive shampoo/conditioning cycles at lower polymer concentrations. This in-built mechanism for preventing excessive build-up from aqueous solutions is compared with the behaviour of other cationic cellulose polymers of higher average molecular weight. 相似文献
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The horny endosperm of maize gives the greatest resistance to the mechanical disintegration of the protein matrix during starch extraction. Thus attempts were made to release the starch by wet-milling of maize grits in the valve of a high-pressure homogenizer. At the same time, information was gathered on the principles involved in the structural breakdown of the endosperm components. For this purpose the influence of the valve geometry as well as the concentration and flow rate of the suspension on the particle size reduction and disintegration was examined. Using a valve specially constructed for the photographic documentation of this process step, it could be shown that the slit height of the valve predominantly determined the particle size of the wet milled product. Already after a single passage through the valve, set at slit heights between 200 and 600 μm, 70% of the grits were reduced to particles <40 μm. The grits were initially between 250 and 1000 μm in size. Scanning electron microscope photographs showed that a large fraction of the mass existed as free starch granules alongside partly intact particles of the protein matrix. Since the starch granules were of higher purity after raffination, it is assumed that the extent to which disintegration of the endosperm particles results in starch granules and protein particles as separate entities, depends not only on the particle size reduction step, but also on the different visco-elastic behaviour of the protein matrix and the starch granules under the influence of the large shear forces occuring in the valve. 相似文献
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在聚合物发泡中,CO2气体的浓度分散和扩散速率与初始气泡形态有关。用可视化方法,对挤出条件下CO2气体注入静、动态流场以及气体在高压和低压注入时的气泡形态和破碎问题的研究。研究表明气体小流量时,静态熔体中球形气泡形成、直径长大定型、长度不断伸长的3个阶段与动态熔体中的初始球形膨胀,头部变尖、中间涨大,尾部颈缩及断裂3个阶段有所不同;新型螺杆对气泡破碎和分离作用比收敛流道更有效。高压下,符合实际生产的气体大流量以射流注入螺槽,形成气熔混合的蜂窝状泡沫,促进了气泡的破裂和分散,加强了气体浓度分散和扩散,有助于聚合物/CO2均相溶液的形成。 相似文献
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