蔗糖晶体在一定的流体力学条件下生长的研究

本文主要研究了蔗糖晶体周围的流体力学条件对晶体生长的影响问题。作者通过许多科学实验,获得各种结晶条件下晶液相对运动速率与蔗糖晶体生长速率的关系数据。经过计算机分析处理后,作者不仅认为 Sherwood 准数方程不适宜于描述蔗糖晶体的生长过程,而且还建立了蔗糖晶体在纯净糖液中生长时的综合性数学模型。此外,作者利用高倍电子显微镜扫描了在不同晶液相对运动速度下生长的蔗糖晶体生长表面,经分析发现,在蔗糖晶体生长过程中,具有一定厚度的浓度边界层对晶面台阶有一定的保护作用.     

晶液间相对流动速度对晶体生产速率和结晶表面的影响研究

实验表明，晶液间相对运动速率对晶体生产速率有直接影响，并且，当相对运动速率大于临界值后，其运动方向将会影响晶体表面的生长台阶。论文提出了晶液间相对运动速率与晶体生产速率间关系的新数学解析式，并从机理上对晶面结构受到的影响进行了探讨。     

晶浆黏度对谷氨酸结晶晶习及粒度分布的影响

用不同浓度的蔗糖溶液制备不同黏度梯度的溶液,考察了黏度对谷氨酸结晶晶习及粒度分布的影响,并通过测定不同黏度条件下谷氨酸结晶诱导期时间及生长速率的变化,探寻了黏度对谷氨酸结晶的影响机理。实验表明,在实验所测的黏度范围(1.00～10.30mP·s)内,黏度对谷氨酸的晶习基本没有影响,在相同过饱和度下,黏度增加,谷氨酸结晶诱导期时间延长,结晶成核速率减小,谷氨酸晶体的生长速率减小,使得谷氨酸晶体的颗粒直径减小,但晶体粒度分布均匀性略有增加。在工业生产上可以适当地提高结晶温度,以降低溶液的黏度,缩短结晶的诱导期时间,提高晶体的生长速率,使其更有利于谷氨酸的结晶。     

实验室流动床中晶体生长的研究

在实验室规模的流动床结晶罐中，４０℃下，测定蔗糖晶体的速度，有助于预测工业结晶罐中蔗糖晶的生长速度，作为研究方案的一个部分。     

甘蔗制糖文摘(六)

蔗糖晶体表面图中杂质扩散速率的研究卢家炯，中国甜菜糖业，1995（3），9～13原糖精炼的蜜洗过程迄今为止仍是凭经验操作，为追求蜜洗效果而有人为地延长蜜洗混合时间的趋向。该研究根据传质理论对蜜洗过程进行了试验。测定了蔗糖晶体表面膜中示踪物钾和若丹明（RhodamineB）在蜜洗混合过程的扩散速率，并对膜厚度进行了计算。试验表明蜜洗混和过程所需时间比实际操作的时间短得多。浅谈设备管理在制糖生产中的重要地位牟爱东，中国甜菜糖业，1995（3），32～35甘蔗制糖文摘搞好设备管理是企业经济效益的基础，只有完好的设备才能保证生产…     

蔗糖晶体中母液包裹体问题探讨

针对结晶器中在流态化状态下生长的晶体中包裹体对蔗糖产品质量的影响。综述了包裹体的形成及其影响因素以及包裹体的测量方法，并对包裹体的进一研究方向进行探讨。     

表面活性剂对蔗糖结晶色素物质影响的机理初探

在煮糖过程中添加表面活性剂,可以获得降低蔗糖晶体色值的结果.本文从结晶学和工艺学方面分析了煮糖过程中造成晶体着色的主要因素,以及表面活性剂的影响,从而对表面活性剂的作用机理进行了初步探讨。认为:正是由于表面活性剂本身的化学的和物理的作用,改善了蔗糖晶体的生长环境,结果使得一方面直接减少了晶体的着色,另一方面提高了晶体的感观质量,使分蜜效果得到了改善,进而降低了晶体糖的色值。     

大米在微波场下糊化过程中的晶体演变研究

针对微波连续煮饭机开发的需要，对大米在微波场中的糊化过程进行了实验研究，在研究过程中使用了X射线衍射的方法，对大米在微波场中糊化过程中的晶体演变进行了测定，初步对大米在微波场下的糊化过程进行了探讨，为进一步研究、设计、开发微波连续煮饭机提供理论依据、设计依据和技术基础。     

氨-水体系中硝酸钾结晶的生长特性

采用MSMPR结晶器研究了不同悬浮密度、氨水浓度和过饱和度下，KNO，在氨-水体系中的结晶动力学特性，并得到KNO3在氨水溶液中的结晶动力学模型。研究结果表明：随着悬浮密度的减少，晶体平均粒径增大，粒径分布变得均匀；氨的浓度增加，结晶成核速率与生长速率均下降，晶体平均粒径减少，但粒径分布变均匀；随着过饱和度的加大，结晶成核速率与生长速率均增加，但晶体平均粒径减小，且粒径分布变差。研究结果可为硝酸钾生产工艺中结晶器的设计提供基础数据。     

蔗糖晶体的“生长分散”与“生长集中”现象

本文简要介绍了在华南理工大学工业结晶实验室进行的有关蔗糖晶体生长性态的研究,以及在煮糖结晶过程中观察到的现象,论述了产生“生长分散”的主要原因,指出“生长分散”、“尺寸分散”不是蔗糖晶体的内在生长特性,而是由于生长环境不均匀所造成的。文中以大量事实说明:在蔗糖晶核的生长过程中还存在着使尺寸趋于均匀统一的“生长集中”现象,并对这一现象产生的机理条件和达到“生产集中”状态所需采取的手段进行了分析、论证。     

Drying and Crystallization of Sucrose Solutions in Thin Films at Elevated Temperatures

ABSTRACT: Thin sucrose films were dried over 30-min periods during which sucrose crystal growth rates were monitored by videomicroscopy. Drying parameters and sucrose solution properties were varied to determine their effect on initial sucrose crystal growth rates. Growth rates increased by a factor of 4.5 as temperature increased from 40 to 70 °C. Varying initial sucrose concentration (70 to 80%) and drying air velocity (2 to 5 m/s) produced no change in crystal growth rates. Increases in film thickness from 150 to 450 μm and the presence of moisture in the drying air reduced growth rates by 33% at 70 °C, but had no effect at 50 °C. The addition of invert sugar (up to 5%) reduced growth rates by a factor of 2 to 3.     

蔗糖结晶过程的粒度分布及其控制

蔗糖晶体的粒度是衡量其质量的重要指标之一。研究蔗糖结晶过程的晶体粒度分布对提高蔗糖质量和蔗糖连续结晶的实践具有明显的指导意义。本论文通过对晶体粒度的计量及结晶过程粒度分布的研究,着重分析了有关影响晶体生长分散的因素,从而指出控制蔗糖晶体粒度及其分布的途径。     

Microwave Heating of Agar Gels Containing Sucrose

A mathematical model was developed for predicting the temperature profiles of cylindrical samples of sucrose containing agar gels heated by microwaves. Temperature was modeled in terms of dielectric properties of gels and the power absorbed by the sample. Experimental corroboration of the predicted temperatures was obtained by microwave heating cylindrical gels of 2% agar containing 0, 40, and 60% sucrose. The levels of sucrose in the gels notably affected the temperature profiles in the cylinders. Samples with no sucrose showed a pronounced central heating effect, 40% sucrose samples showed a early uniform heating profile and 60% sucrose samples showed surface heating.     

Effect of Locust Bean Gum and Selected Sweetening Agents on Ice Recrystallization Rates

A methodology has been devised to study the effects of sweeteners and a stabilizer on the rate of ice recrystallization. Aqueous solutions of sucrose, corn syrup (62 DE), and high fructose corn syrup with locust bean gum, and solutions of corn syrup with varying levels of locust bean gum were also studied. Microprocessor controlled time-temperature experiments were performed with each sample. Average ice crystal size was measured after each heating/ cooling cycle. Effect of viscosity on ice recrystallization growth rates was also studied. This methodology is an improved technique for providing temperature control during fluctuating temperature studies. Concentration of locust bean gum showed no correlation to ice recrystallization rates. The choice of sweetener used in the aqueous solution was found to affect the rate of ice recrystallization.     

Ice recrystallization inhibition in ice cream as affected by ice structuring proteins from winter wheat grass

Ice recrystallization in quiescently frozen sucrose solutions that contained some of the ingredients commonly found in ice cream and in ice cream manufactured under commercial conditions, with or without ice structuring proteins (ISP) from cold-acclimated winter wheat grass extract (AWWE), was assessed by bright field microscopy. In sucrose solutions, critical differences in moisture content, viscosity, ionic strength, and other properties derived from the presence of other ingredients (skim milk powder, corn syrup solids, locust bean gum) caused a reduction in ice crystal growth. Significant ISP activity in retarding ice crystal growth was observed in all solutions (44% for the most complex mix) containing 0.13% total protein from AWWE. In heat-shocked ice cream, ice recrystallization rates were significantly reduced 40 and 46% with the addition of 0.0025 and 0.0037% total protein from AWWE. The ISP activity in ice cream was not hindered by its inclusion in mix prior to pasteurization. A synergistic effect between ISP and stabilizer was observed, as ISP activity was reduced in the absence of stabilizer in ice cream formulations. A remarkably smoother texture for ice creams containing ISP after heat-shock storage was evident by sensory evaluation. The efficiency of ISP from AWWE in controlling ice crystal growth in ice cream has been demonstrated.     

Hot-stage Microscopy of Cake Batter Bubbles during Simulated Baking: Sucrose Replacement by Polydextrose

A hot-stage video microscopical technique was developed to study the effects of sucrose replacement by polydextrose (weight for weight basis) on the foam characteristics of cake batters, before and during heating. Polydextrose substitution increased the mean size of air-bubbles in the cake batter and introduced a larger variation in bubble size distribution than the sucrose batter. The differences between sucrose and polydextrose batters on initial bubble size distribution were reflected in expansion rates of bubble populations during heating. The lack of uniformity in the bubble distribution of batters containing polydextrose increased the rate of gas diffusion from small bubbles to larger ones. On heating, the bubble population of sucrose batters expanded more than that of polydextrose substituted batters.     

Freezing and Ice Recrystallization Properties of Sucrose Solutions Containing Ice Structuring Proteins from Cold-Acclimated Winter Wheat Grass Extract

ABSTRACT: The freezing properties of sucrose solutions containing ice structuring proteins (ISPs) from cold-acclimated winter wheat grass extract (AWWE) were evaluated. Neither significant ice nucleation nor thermal hysteresis activity in unpurified AWWE were detected ( P > 0.05). Ice recrystallization in sucrose solutions was assessed by bright field microscopy. Ice crystal growth was significantly reduced with the addition of more than 0.05% total protein from AWWE in 23% sucrose solutions frozen under static conditions and temperature cycled under long periods of time (60 min). Ice recrystallization inhibition was not evident when the samples were temperature cycled for shorter periods of time (10 min), indicating that an adsorption time may be required for the ISPs to be significantly active. The ice recrystallization was reduced with the increased on ISP concentration until reaching a plateau after adding 0.13% total protein from AWWE, representing a surface coverage of 9 mg protein/m² ice (assuming 100% adsorption). The reduction of ice crystal growth was as high as 74% compared with the control. This ice recrystallization inhibition offers significant opportunity for the use of ISPs from AWWE in frozen foods.     

煮糖过程的新型建模方法

煮糖过程的主要非线性表现为晶体生长率。本论文采用两种方法来描述晶体生长率模型的设计，第1种方法是通过采用非线性规划最优化方法(NLP)决定晶体生长率经验公式的参数；第2种方法是一种新颖的建模策略，它把晶体生长率作为非线性逼近器的人工神经网络(ANN)与由蔗糖晶体质量平衡所表述的先前既定的知识相结合。最初结果显示第1种类型的模型能够较好地执行局部匹配，而第2种具有更大的灵活性。     

Effect of trehalose on the glass transition and ice crystal growth in ice cream

The effects of trehalose and sucrose on the rate of ice crystal growth in ice cream during accelerated shelf‐life were compared. Experimental and theoretical freezing curves were shown to be in good agreement. Glass transition temperatures (T_g) of maximally freeze concentrated trehalose and sucrose solutions (40% w/w) were found to be ?39.5 °C and ?47 °C respectively. For ice cream mixes, the T_g value increased from ?46.4 °C for the 100% sucrose‐based mix to ?42.0 °C for the 100% trehalose sweetened ice cream. However, no differences in viscosity, nucleation rate or inhibition of ice crystal growth were observed with increasing trehalose concentration in ice cream.