Thin Film Rheology and Tribology of Chocolate

We investigated relations between food texture and thin film properties rather than bulk properties. Such thin film rheological or‘tribological’effects may characterize physical behavior and physical perceptions of food products. Experiments were done on three chocolate samples. The Surface Forces Apparatus (SFA) proved to be effective for studying the very complex chocolate system. Very complex thin film behavior was found to be quite different for the three samples. Fat constitution and average particle size were important in determining the type of friction forces generated between shearing/sliding surfaces separated by thin films of chocolate. Such studies can help characterize specific physical qualities of chocolate.     

Capillary Flow and Rheology Measurements on Chocolate Crumb/Sunflower Oil Mixtures

ABSTRACT: Rates of penetration of sunflower oil into beds of 3 types of chocolate crumb have been measured and the results analyzed using the Washburn-Rideal theory. The data show that the rates are a function of both the specific surface area of the crumb particles and their surface composition. Addition of an emulsifier to the oil reduces the penetration rate into the crumb made with full-cream milk powder, whereas for crumbs containing skimmed-milk powder, rates go through a maximum with increase of emulsifier concentration. Rheological data for dispersions of crumb in oil were fitted to the Casson equation. An inverse correlation was found between penetration rates and Casson yield values.     

Viscosity of Molten Milk Chocolate with Lactose from Spray-Dried Whole-Milk Powders

Dry whole-milk powders containing 0, 30, 50 and 70% nominal lactose prepared by spray-drying alone, or followed by post-drying crystallization, were incorporated into milk chocolate to give 0–50% substitution of lactose for sucrose. Increasing the concentration of amorphous lactose from spray-dried powders in the chocolates decreased viscosity, increased particle size of refined chocolate mass, and lowered the concentration of surface-active agents at which a minimum in Casson yield value was observed. Increasing the concentration of crystalline lactose from milk powders in the chocolates increased viscosity, decreased particle size, and increased the concentration of surface-active agents at which a minimum in Casson yield value was observed. Conditions which affect lactose crystallinity in milk powders, such as improper storage and handling prior to use in chocolate production, could be responsible for variations in chocolate viscosity noted sometimes by processors.     

凉粉草胶的稳剪切流变学性质

研究了凉粉草胶在不同质量浓度、温度、pH、盐的种类及盐浓度和不同蔗糖浓度下的流体行为以及固定剪切速率下的表观粘度随不同条件的变化情况。结果表明,凉粉草胶溶液在不同的条件下呈牛顿流体或假塑性流体行为,在剪切速率52.8s-1下,10 g/dL凉粉草胶溶液的表观粘度随胶质量分数(1~20 g/dL)的增加而递增,随温度(25~70℃)的升高而递减,随pH(5~12)的变化则不具有单调性,随NaCl(0~3.0 g/dL)的添加而递减,随CaCl2(0~3.0 g/dL)的添加则先减小后增大,随蔗糖(10~50 g/dL)的添加则递增。     

巧克力起霜问题探讨

如何有效防止起霜是巧克力制造业需待解决问题,该文比较全面分析巧克力起霜原因,机理, 并提出相应延缓巧克力起霜方法。     

冷冻干燥草莓巧克力的研制

研究了草莓的冷冻干燥及巧克力涂衣方法的生产工艺,确定了冻干草莓的工艺参数及巧克力涂衣的两种方法的生产参数,其中以喷淋挂衣法为佳。     

Effect of Shear on the Rheology and Crystallization of Palm Oil

ABSTRACT:  This article reports on the impact of shear on crystallization upon cooling of palm oil. Samples were cooled down under shear from 70 to 10 °C, then kept at this temperature, while performing rheological measurements using a controlled shear rate rheometer and rheo-optical observations using optical microscopy and small-angle light scattering. Shear rates between 1 and 300 s⁻¹ were investigated. Two crystallization steps were observed, characterized by associated viscosity increases. The effect of shear on these 2 crystallization processes was investigated. Shear was shown to influence almost all of the steps of the structuring process of the crystallizing palm oil. The spherulite size and growth rate during the 1st crystallization are affected by shear. The onset time of the 2nd crystallization process strongly depends on the extent of shear. The steady state structures after the 1st and 2nd crystallization processes constituted of a suspension of aggregates of spherulites are controlled by the applied shear rate.
Practical Application: The texture of crystallized vegetal fats and subsequent end product properties depend on the structure developed during the crystallization process. This structuring process is strongly influenced by the thermo-mechanical history applied to the product (cooling rate, degree of undercooling, annealing time, application of flow). This article shows how the shear rate as well as extent of shear affects the different steps of the crystallization and aggregation processes in the case of palm oil after the 1st crystallization.     

巧克力豆腐干的综合指标优化研究

优化生产巧克力豆腐干的生产工艺,采用传统制作豆腐干的生产工艺流程:点浆→胀浆→上板→压榨→切块→成品,并在生产流程点浆中加入巧克力粉,利用控制单一变量的实验方法,控制豆腐脑的加入量为65g(一般豆腐干所需要的豆腐脑的含量),分别加入5、10、15、20、25g的巧克力粉,确定不同质量巧克力粉下豆腐干相关指标(表皮光洁度、味浓度、入口的软糯程度豆腐干的规整度),进行感官评价,确定最适合的巧克力粉加入量。豆腐干成型后的相关指标为:豆腐干的表面光洁度采用摩擦力计进行测定,豆腐干的味浓度、入口的软糯程度、规整度采用感官评价,并对发放调查问卷的统计结果进行数学统计分析,确定最优的巧克力粉加入量为15g时可优化巧克力豆腐干的生产工艺,缩短生产时间,达到最好的生产效率。     

巧克力非活性乳酸菌饮料的研制

研究了以脱脂奶粉、可可粉为主要原料,生产巧克力非活性乳酸菌饮料的生产工艺,通过试验确定了工艺参数。     

Partitioning of Printing Ink Solvents on Chocolate

Partitioning (Kp) of printing ink solvents was studied in three types of chocolate with different fat content and degrees of crystallinity. At 25°C, chocolate liquor (48% fat and medium crystallinity) showed a higher Kp than chips (25% fat and higher crystallinity), but cream (29% fat and lowest crystallinity) showed the highest Kp. Order appeared to depend on degree of crystallinity. At 35°C and 45°C as samples became increasingly molten, effect of crystallinity diminished and order of increasing Kp depended on fat content. Kp order of solvents was the same in all chocolates and temperatures: toluene > isopropanol > methyl ethyl ketone > ethyl acetate > hexane in accord with Hildebrand solubility parameter differences.     

纸浆与漂白剂的混合机理与纸浆流变学

主要论述了纸浆漂白过程中的混合机理及影响混合效果的诸如纸浆流变学等因素。     

低能量巧克力的开发

食品的低能量化成为当今世界食品发展的主要趋势。低能量巧克力开发的关键在于 ,如何去除或替代脂肪。本文详细介绍了一些新型低能量巧克力的配方、生产工艺以及技术难题     

巧克力珍珠的呈色与成因属性

采用LA-ICP-MS、拉曼光谱仪、微型光纤光谱仪等分析测试仪器,对近期市场上出现的巧克力珍珠样品的化学成分、拉曼光谱、反射光谱、表面微观特征及其成因属性进行了初步研究。分析与测试结果表明,多数巧克力珍珠样品内发育有简单且着色外浅(棕黄色、棕红色)内深(灰黑色)的同心色带结构,深浅不一的棕红色色斑和灰白色色斑沿珍珠层表面相间无序分布;经低温加热漂白处理后,巧克力珍珠样品的化学成分、拉曼光谱、UV-NIS反射光谱特征均发生了不同程度的变化。其化学成分以相对富Cu和Pb、贫K为特征;1 276 cm-1处的拉曼谱峰红移至1 371 cm-1附近,1 583 cm-1处的拉曼谱峰则蓝移至1 545 cm-1附近,663 cm-1处的拉曼谱峰随之消失;在可见光波长范围内,c带(697 nm)的相对吸收强度骤减,a带向长波方向红移并与b带组合成一宽大舒缓的吸收谱带。初步证实,巧克力珍珠样品的颜色与其黑色素内共轭双键电子跃迁之间尚无直接的内在联系,主要归因于塔希提棕黑色珍珠内存在的钾色素蛋白经热变异作用所致。     

巧克力起霜研究进展

巧克力起霜导致产品品质下降,成为困扰糖果工业的一个世界性难题。基料油种类不同,起霜的机理显著不同。从基料油性质出发,详细阐述基料油组成、加工条件以及储存条件对巧克力起霜的影响。在此基础上,对各类巧克力起霜的机理进行总结,为解决起霜问题提供理论支持。参考国内外文献报道,对巧克力起霜的研究方法进行总结,并详细阐述具有延缓起霜作用的措施,为巧克力生产提供参考。     

Chocolate at a Sliding Interface

The tribological properties of a chocolate‐lubricated tribo‐system have been measured with a pin‐on‐disk tribometer employing poly(tetrafluoroethylene) (PTFE)/zirconia (ZrO₂) as the tribo‐pair. For this study, a series of test chocolate samples was prepared by systematic variation of conching type, particle‐size distribution, milk fat/cocoa butter ratio, and lecithin content. Tribological measurements were found to be sensitive to lecithin content for all particle sizes investigated, while only being sensitive to particle size at high lecithin content. Rheological measurements were found to be sensitive to lecithin content in the case of small particle size, and sensitive to particle size in the case of low lecithin content.     

HACCP在劲跳巧克力生产中的应用

本文按照HACCP体系的监控要求对劲跳巧克力生产过程进行危害分析和品质控制,确立了四个关键控制点:原辅料验收、化油、精磨、过滤和两个特殊过程,即水分控制过程和细度控制过程,并建立了相应的监控程序和纠偏措施,提高了劲跳巧克力的生产效率。     

Tempering of Chocolate in a Scraped Surface Heat Exchanger

Crystallization of dark chocolate during different tempering processes has been studied in-situ in a lab-scale Scraped Surface Heat Exchanger. The linear relationship between torque and viscosity made possible the control of chocolate crystallization during tempering by following torque variations vs. time and converting them to equivalent viscosity values. These variations of equivalent viscosity of chocolate observed during tempering were correlated with temper-meter measurements which had been related to the content of cocoa butter seeding crystals. A temperature cycle (50-26.1-30.5-33.3°C) enabled preparation of a well-tempered chocolate stable for ≥30 min at that temperature. It was characterized by a seed crystals content of about 1.15 ± 0.1% of cocoa butter, crystallization temperature of 23.9 ± 0.2°C in the temper-meter and an equivalent viscosity of 3.0 ± 0.4 Pa.s.