L-鸟氨酸盐酸盐结晶新工艺研究

探索通过电导率仪在线调控结晶过程的可行性,考察添加晶种、消晶水对晶体晶形及晶体平均粒径的影响.实验发现:可以根据电导率的变化趋势比较直观地了解结晶速率的变化情况,进而可以对结晶过程进行调控.5min时加2%的晶种,晶种平均粒径为134.59μm,结晶时间4h,最终得到晶体产品纯度99%,收率86.3%,粒径270.6μm.     

平面蒸发条件对再制盐特性影响的研究

结晶是化工生产过程中的一个重要的单元操作,结晶过程控制多以获得高质量和适宜粒度的产品为目的.实验研究了平面蒸发方法制备氯化钠再制盐过程中的蒸发速率、停留时间及搅拌频率对产品特性的影响.结果表明:沸腾蒸发条件下,晶体成核速率较快,再制盐多为立方体晶习.当蒸发速率为14 mm/h时,再制盐平均粒径为800 μm,晶体产品粒径均匀.停留时间对再制盐片晶厚度影响较大,停留时间越长,片晶越厚.搅拌频率越大,晶体产品平均粒径越小,且在高搅拌频率下再制盐易形成立方体晶习.无搅拌的条件下,停留时间为10 h时,再制盐平均粒径为827.0 μm,堆积密度为0.749 g/mL,粒度分布较均匀,为500μm～ 1500 μm.     

晶种分解过程粒度模型的建立

对晶种分解的机理进行了探讨，研究了晶种分解过程对结晶产品粒度的影响，建立了晶种分解过程粒度变化模型     

石膏型卤水体系硫酸钙结晶过程研究

石膏型卤水体系真空蒸发制备NaCl过程中,CaSO4.2H2O对NaCl产品的纯度影响较大。研究了石膏型卤水体系中CaSO4.2H2O的结晶过程。实验研究了搅拌速率、停留时间、晶种量、温度等条件对石膏型卤水体系二水硫酸钙结晶过程的影响。研究结果表明:晶体的粒度开始随搅拌速率的增大不断增大,当搅拌速率达250 r/min时,晶体粒度达到最大值77.24μm;晶体粒度同样开始时随停留时间的增大而增大,当停留时间为120 min时达到最大值,此时平均粒径为70.39μm。CaSO4.2H2O晶体粒度随晶种量的增加而减小;在40℃～70℃范围内,晶体粒度开始随温度的升高而增大,在60℃时达到最大值,此时晶体的平均粒径为70.39μm,随后随温度的升高晶体的粒度逐渐降低。采用正交实验确定了石膏型卤水体系对二水硫酸钙生长影响的最佳实验条件为:温度为70℃、搅拌速率为250 r/min,停留时间为120 min,晶种量为3 g。此时的晶体的线生长速率为2.508×10-9 m/s。     

珍珠超高压撞击流超微粉碎的研究

本实验研究了超高压撞击流超微粉碎珍珠的可行性。采用300MPa超高压撞击流反复粉碎珍珠,观察珍珠粉体显微形态,检测粒度体积累积分布、表面积/体积及平均粒径,并与市售珍珠粉进行比较。结果表明,随粉碎次数增加,D50、D90、平均粒径逐渐减小,表面积/体积逐渐增大,粉碎10次平均粒径0.712μm,表面积/体积达13.550m2/cm3,优于市售珍珠粉。可见,超高压撞击流粉碎珍珠效果良好,为超微粉碎提供了一种可行方法。     

L-谷氨酸晶种制备新工艺的研究

在研究超声波刺激下溶剂及添加剂对谷氨酸（Ｌ－谷氨酸）过饱和溶液成核晶型、粒度的影响的基础上，研究得出一条制取谷氨酸晶种的新工艺。用本法制得的晶种与目前工业上常用的粗晶种相比，具有粒度均匀、晶形完整、纯净（均为α型晶体）的优点。     

螺旋藻超高压撞击流破壁实验研究

本文将螺旋藻用300MPa对撞式超高压撞击流处理,比较处理前后的显微特征、粒度分布以及粉体表征,考察了撞式超高压撞击流技术对螺旋藻细胞破的壁效果。结果表明对撞式超高压撞击流粉碎后,D98由粉碎前的22.25μm减小到10.772μm;D50由3.706μm减小到1.601μm;体积平均粒径由5.771μm减小到2.65μm;面积平均粒径由1.998μm减小到0.848μm;表面积/体积由3.0032m2/cm3增大到7.0793m2/cm3;粉体显微特征明显减小。对撞式超高压撞击流可以有效粉碎螺旋藻细胞,为螺旋藻破壁加工提供一种方法。     

仲钨酸铵（APT）中温还原制取粗晶钨粉

以仲钨酸铵（APT）为原料,加入添加剂Li、Na盐在1000℃湿氢条件下还原制得粗晶钨粉。通过SEM、XRD和激光粒度仪对粗晶钨粉形貌、物相组成及粒度分布进行表征。研究了还原温度,时间,Li、Na盐的种类及含量对钨粉粒度的影响。结果表明,采用APT为原料,Li2CO3为添加剂,在1000℃,180min湿氢条件下,直接还原制备出了流动性良好、结晶完整的粗晶钨粉,平均粒径≥40μm。     

二次结晶谷氨酸纯化工艺研究Ⅰ:转晶条件优化

从等电母液中蒸发结晶得到的二次结晶谷氨酸,其硫酸铵、色素等杂质含量高,不能直接精制生产味精,转晶是提高二次结晶谷氨酸质量的途径之一。实验研究了转晶温度、pH值、转晶料水比等因素对谷氨酸转晶的影响,得到比较理想的转晶条件:转晶温度95℃,pH值4.5,转晶料水1∶2.5,活性炭添加量为1%(1g活性炭/100g二次结晶谷氨酸)。     

灵芝超微粉理化特性研究

采用超微粉碎技术,得到了灵芝超微粉。对超微粉与常规粉(过60目筛得到)、超细粉(粒径≤30μm,相当于550目)的表征,显微镜观察和粗多糖溶出特性检测结果表明,灵芝超微粉粉体粒度分布在2.92~6.03μm(相当于5 654目),体积平均粒径为3.18μm,100%的粉体颗粒粒径(D100)小于9.96μm,呈对称的单峰分布,均匀性好;其比表面积为3.63μm/g,分别是常规和超细粉的15倍和2倍。同时超微粉细胞破壁完全,主要功效成分灵芝多糖在20 min时的浸出率与超细粉2 h时的浸出率相当,显示生物利用度得到有效提高。     

不同加工方式下菠萝蜜种子物理性质及挥发性成分的比较分析

比较研究了干燥、煮熟及粉碎处理下菠萝蜜种子样品的粒度大小、水合能力、持油性、溶胀性及其挥发性成分的变化。结果表明,菠萝蜜煮熟种子表面积平均粒径为116.13μm,大于新鲜种子的74.15μm和干燥种子的29.22μm,新鲜种子体积平均粒径最大为550.26μm,干燥种子比表面积最大为0.21 m2/g;干燥种子的持水性（5.25）和膨胀性（4.00）比新鲜种子和煮熟种子强,新鲜种子的持油性最强为1.66。从菠萝蜜新鲜种子检出31种挥发性化合物,占总相对含量的77.37%;干燥和煮熟种子分别检出24种和32种化合物,分别占总含量的63.32%和35.74%,表明干燥和水煮处理会减少菠萝蜜种子风味物质。而煮熟种子中酯类化合物达16种,多于新鲜种子的8种和干燥种子的9种,且经过干燥和煮熟加工之后,甲醇等有毒成分得到清除,益于食用,为菠萝蜜种子的食用加工提供一定的理论依据。     

洪泽湖野生红莲子、芡实、菱角中淀粉的理化性质研究

以洪泽湖野生的红莲子、芡实、菱角为原料,采用浸泡法制备3种淀粉,并对3种淀粉的颗粒形貌、大小、结晶结构、热学性质、溶解度、膨胀度、糊化特性、分子大小与分布进行研究。结果表明:野生莲子、芡实和菱角淀粉体积平均粒径分别为11.77,2.15,25.76μm,且颗粒大小均匀。3种淀粉均为A型结晶构型,莲子、芡实和菱角淀粉的晶体度分别为27.1%,23.7%,25.7%。糊化峰值温度分别为76.04,72.37,75.88℃,糊化焓值分别为8.46,5.58,4.63J/g。3种淀粉糊的冻融稳定性较差,易形成局部的微晶束,易凝沉、易回生,均不适合应用于冷冻食品;3种淀粉糊的透明度介于马铃薯淀粉和玉米淀粉之间;3种淀粉的热糊稳定性较好,适用于高温食品的生产。     

水剂法提取萝卜籽油的工艺研究

为充分开发萝卜籽这一新的油料资源,本文研究了水剂法提取萝卜籽油的工艺条件并利用响应面法对提取条件进行了优化.实验以干燥粉碎的油用萝卜籽为原料,以pH4.5的柠檬酸缓冲溶液为溶剂,对油用萝卜籽中的粗脂肪进行提取,探究萝卜籽油提取率与料液比、提取时间以及提取温度这3个实验因素间的关系.结果 表明:萝卜籽油提取率受料液比的影...     

超声波辅助溶剂法提取苦瓜籽油的工艺研究

以苦瓜籽为原料,无水乙醇为浸提溶剂,采用超声波辅助溶剂法提取苦瓜籽油。在单因素试验基础上进行正交试验,得出最佳提取工艺条件:颗粒粒径为212μm、液料比8∶1(mL/g)、超声时间60 min、超声温度50℃、超声功率160 W。在该工艺条件下,苦瓜籽油的平均提取率为84.32%。     

紫苏籽油双层乳状液的制备及其物理化学稳定性评价

采用紫苏籽油为芯材,大豆多糖和壳聚糖为壁材,分别制备紫苏籽油单层与双层乳状液,并且对乳状液的粒径、Zeta电位、物理稳定性以及化学稳定性进行评价。结果显示,单层乳状液粒径随着芯壁比（质量比）的升高而增大,物理稳定性变差,最适的芯壁比（质量比）为2∶1;随着壳聚糖质量分数的增加,双层乳状液的Zeta电位逐渐增大,并且由负值变为正值,壳聚糖质量分数为0.2%时电位绝对值最小为3.6 mV,当壳聚糖质量分数为0.4%时电位为43 mV,电位增加速率变小;随着壳聚糖质量分数的增加,乳状液粒径呈先减小、再增大、再减小的变化,壳聚糖质量分数为0.2%时达到最大粒径为5.21 μm,0.4%时达到最小粒径为1.185 μm;随着壳聚糖质量分数的增加乳状液物理稳定逐渐增强。壳聚糖质量分数对乳状液化学稳定性影响显著（p＜0.05）,抗氧化效果依次为0.4%＞0.6%＞0.2%。     

The Effect of Seed Size and Microstructure on Their Mechanical Properties and Frictional Behavior

The seeds of grass pea were selected based on their size, hardness, and microstructure in order to examine their mechanical properties and friction coefficients versus mass. The size, shape, mass, and static friction coefficients of seeds were determined using adequate methods. Seed hardness was measured using compression methods, and it was described by typical and corrected fracture parameters. The microstructure of cotyledons and seed surfaces was viewed using scanning electron microscopy, and surface microimages were processed by digital image analysis. The length of the examined seeds ranged from 5.86 mm to 14.25 mm, their width ranged from 5.47 mm to 12.93 mm, thickness from 4.59 mm to 6.21 mm, mass from 0.110 g to 0.570 g, projected area from 28.55 mm² to 148.73 mm², and roundness from 1.060 to 1.126. The static friction coefficients for seeds of the examined accessions and varieties determined on steel, wood, rubber, and PVC surfaces were 23.4–33.3°, 24.4–37.2°, 29.6–50.4°, and 22.4–35.4°, respectively. For grass pea seeds of irregular size and shape, corrected fracture energy values (with regard to seed mass and volume) were proposed as a more robust parameter of seed hardness. The values of the static friction coefficient depend on both seed mass and the microstructural properties of seed surface digitalized with the involvement of image analysis techniques.     

Relationships of rapeseed strength properties to seed size,colour and coat fibre composition

BACKGROUND: The size and strength of rapeseeds are factors likely to determine their suitability for storage and processing. The mechanical properties of whole seeds depend mainly on their coat composition. This study investigates variations in seed strength and colour between different‐sized rapeseeds. The paper also presents an explanation of the differences in seed mechanical properties through analyses of coat fibre composition. RESULTS: The strength properties of seeds were dependent on seed size and correlated with seed equivalent diameter. All measured strength indices showed that seeds of diameter above 2 mm were the most resistant. The mechanical properties of seeds were also correlated with the colour of seed surface, indicating that the most resistant seeds were those with values of H > 60°, S < 15% and I < 19% in the HSI colour space. The resistance of individual seeds was attributed to the surface density of soluble and insoluble dietary fibre, especially cellulose and lignin. CONCLUSION: The results suggest that the highest mechanical resistance shown by the largest and blackest rapeseeds can be associated with the high surface density of fibre components in the seed coat. Copyright © 2008 Society of Chemical Industry     

Size,shape, and identity of surface crystals and their relationship to sensory perception of grittiness in soft smear-ripened cheeses

Soft smear-ripened cheeses undergo extensive surface crystallization and radial demineralization of calcium, magnesium, and phosphorus, which likely contributes to radial softening during ripening. Furthermore, anecdotal evidence suggests that grittiness is a common characteristic of smear-ripened cheeses. The primary aims of the present study were to evaluate the intensity of perceived grittiness while assessing other key sensory attributes in US artisanal and European protected designation of origin smear-ripened cheeses, and to relate perceived grittiness to the size, shape, and identity of crystals present in the cheese surface smears. Fully ripened wheels of 24 different varieties of smear-ripened cheeses, 16 produced in the United States and 8 in the European Union, were obtained from retail sources. A trained sensory panel (n = 12) was employed to evaluate intensity of grittiness. Crystals present in the cheese smears were identified by powder X-ray diffractometry and polarized light microscopy, and further evaluated in polarized light microscopy micrographs by image analysis for size and shape characteristics. Mean sensory scores for the 24 cheeses ranged from no perceived grittiness to easily identifiable grittiness. Surface crystals included ikaite, struvite, calcite, and brushite, and mean crystal length and area ranged among cheeses from 27 to 1,096 μm, and 533 to 213,969 μm², respectively. Panel threshold for grittiness occurred at a mean crystal length of about 66 μm and mean crystal area of about 2,913 μm². Cheeses with mean values at or below these thresholds displayed negligible perceived grittiness. In contrast, for cheeses with mean values above these thresholds, the mean sensory scores for grittiness were highly correlated with mean crystal length and crystal area (r = 0.93 and 0.96, respectively). Results suggest that surface crystals in soft smear-ripened cheeses influence sensory perception of texture in complex ways that likely include radial softening and grittiness development. A better understanding of factors that govern surface crystal formation may lead to improved control over crystallization and more consistent cheese texture.     

热处理对汉麻乳稳定性的影响及蛋白结构表征

为研究热处理对汉麻乳稳定性及其蛋白结构的影响,本实验通过汉麻乳氮溶解指数、离心沉淀率、乳化特性、乳液表面电位和粒径等指标监测汉麻乳热处理过程中稳定性的变化,利用傅里叶变换红外光谱表征热处理对汉麻乳蛋白二级结构的影响。结果表明：随着热处理温度的升高（55～95 ℃）,汉麻乳氮溶解指数由58.55%逐渐减小到39.81%,离心沉淀率由16.58%逐渐增加到34%,汉麻乳蛋白的平均粒径由192.2 nm逐渐增大到304.6 nm;傅里叶变换红外光谱分析结果显示,随着热处理温度的升高,汉麻乳蛋白分子二级结构发生变化,α-螺旋结构相对含量由28.57%减少到23.70%,无规卷曲结构的相对含量由21.13%增加至25.41%;汉麻乳在65 ℃热处理时,Zeta电位绝对值达到最大（20.57 mV）,此时汉麻乳表现最稳定,乳化活性及乳化稳定性最高,乳化活性指数为0.357 m2/g、乳化稳定性指数为43.74%。本研究结果将为汉麻乳加工及应用提供理论依据。     

Variation among physical,chemical and technological properties in three Sicilian cultivars of Chickpea (Cicer arietinum L.)

Three Sicilian chickpea cultivars (‘Calia’, ‘Etna’ and ‘Principe’) were evaluated for physical, chemical and technological properties. Whereas no substantial differences were ascertained on seeds chemical composition, the cultivars greatly differed in terms of seed size, specific surface area (SSA) and seed coat incidence. These last two properties affected the technological properties of the seeds. In particular, a high SSA (‘Calia’) contributed to a faster softening, whilst a great coat thickness (‘Etna’) delayed both hydration and softening rate. The time required to obtain an acceptable firmness (cooking time) was greatly reduced by presoaking the seeds in salt solution (0.5% NaCl or NHCO₃). ‘Calia’ required the lowest cooking time when soaked in distilled water or in 0.5% NaCl. Presoaking seed in NaHCO₃ allowed halving the cooking time in all cultivars.