SUPERPOSITION OF COMPLEX VISCOSITY CURVES DURING GELATINIZATION OF STARCH DISPERSION AND DOUGH

Complex viscosity (η*) of 8% tapioca starch dispersion (STD) during gelatinization at a specific oscillatory frequency (ω, rad s^?1) was independent of the heating rates: 1.5 to 6.0C min^?1 when plotted against temperature as the independent variable instead of time. The influence of ω in the range: 3.14 to 62.83 rad s^?1 on η* was scaled by a frequency shift factor resulting in a reduced complex viscosity (η*_R) versus temperature (58–88C) master curve. Similar η*_R versus temperature master curves were derived for η* data on a 8% waxy rice STD at the heating rate 2C min^?1 and ω values 1.27 to 125.6 rad s^?1, and a 45.5% waxy rice dough at the heating rate 4C min^?1 and ω values 1.27 to 94.2 rad s^?1. The areas under the η*, at ω=6.28 rad s^?1, versus temperature curves of the tapioca and the waxy rice STDs with different starch concentrations were exponentially related to the concentrations.     

VISCOELASTIC BEHAVIOUR DURING THE GELATINIZATION OF STARCH II. EFFECTS OF EMULSIFIERS

The viscoelastic behaviour during the gelatinization of starch in the presence of emulsifiers was studied in oscillatory shear. Glycerol-monostearate and sodium stearoyl-lactylate delayed the viscoelustic changes during gelatinization in a way which was intetpreted as related to the granules being stiffer in presence of these emulsifiers. Sodium abdecyl sulphate caused a destabilization of the granules, resulting in the rheological changes occurring at lower temperatures. Emulsifiers increased the viscous part of the rheological response. In a wary-starch variety, where the amount of amylase is small, emulsifiers had only a small effect on gelatinization. It was concluded that the formation of an amylose-lipid complex was of importance if an emulsifier was to exert an effect.     

ASSESSMENT OF THE SPREADABILITY OF OFFICIAL PHARMACEUTICAL CREAMS AND OINTMENTS USING THE MASTER CURVE CONCEPT

Abstract . Spreadability characteristics of official creams and ointments of the British Pharmacopoeia and the British Pharmaceutical Codex were determined using the Master Curve concept and continuous shear data. Experimental results were obtained using a Ferranti-Shirley cone and plate viscometer at 25 C and 34 C, representing an approximate temperature range encountered during spreading of topical preparations. Data derived for creams intersected the Master Curve in the preferred region, although not at the optimum value. Ointments demonstrated large variations in spreading properties. The variation and lack of optimum spreadability characteristics were explained by considering the medicinal criteria required of topical pharmaceutical products as distinct from cosmetics.     

BACK EXTRUSION and SIMULATION of VISCOSITY DEVELOPMENT DURING STARCH GELATINIZATION

A generalized apriori theoretical model relating apparent viscosity of protein dough to several independent variables was used to model gelatinized starch dispersions. Independent variables in the original model were shear rate, temperature, moisture content, temperature-time history and strain history. the model is applied here to corn starch dispersions gelatinized using various temperature-time treatments. Apparent viscosity of a 13.7% gelatinized cornstarch solution at constant shear rate and strain history was measured at 20 C using a back extrusion technique. Activation energy of gelatinization was estimated as 210 kJ/mol (50 kcal/mol) over the range 81–95 C. the activation energy decreased in the range 95–105 C.     

INFLUENCE OF GRANULE SIZE ON VISCOSITY OF CORNSTARCH SUSPENSION

The influence of granule size and size distribution in gelatinized suspensions of 2.6% cornstarch heated at fixed temperatures between 70–90C on the power law viscosity was measured by laser diffraction. In the early stages of gelatinization, where the granule size standard deviation was less than 12 μm, dilatant behavior was observed over the shear rate range 200–1100 _S ⁻¹. At constant starch concentration and without granule rupture, suspension consistency, K, increased exponentially with granule mean diameter while the flow behavior index, n, decreased linearly with increase in the extent of gelatinization and the standard deviation of the granule size. The variation of K with granule size and that of n with standard deviation were found to be independent of temperature over 70–90C. In the later stages of gelatinization, where the granules lose their integrity, suspension viscosity progressively decreased as granule rupture continued.     

VISCOELASTIC BEHAVIOUR DURING THE GELATINIZATION OF STARCH I. COMPARISON OF WHEAT, MAIZE, POTATO and WAXY-BARLEY STARCHES

Dynamic measurements were used to characterize the viscoelastic behavior during gelatinization of wheat, maize, potato and waxy-barley starches. During the experimental conditions used the curves of storage modulus (G') and loss modulus (G") versus temperature showed an initial peak for all starches, followed by a second peak at 90–95° C in the case of wheat and maize starches. Wheat starch gave a more viscous response than the other starches. The changes in G' and G" were correlated to the changes in gel volume and amylose leaching during the heating. The results were interpreted using a composite material as a model for the starch gel.     

OPTIMIZATION OF CORNSTARCH/XANTHAN GUM CONTENT FOR THICKENING OF COCOA SYRUPS

ABSTRACT

Blended cornstarch–xanthan gum systems were optimized for thickening of cocoa syrups. For this purpose the sensory (whole and partial), textural (force of penetration, adhesiveness and stringiness) and rheological properties (flow curves as well as viscosity/time and viscosity/temperature relationships) of cocoa syrups were studied. Flow curves were described by rheological model of Casson, which accounted syrups under study for non‐Newtonian, pseudoplastic and thixotropic fluids. Also models of Weltman and Arrhenius were applied for comparison of obtained data. The areas of thixotropy hysteresis loops were also calculated. Obtained data (sensory, textural and rheological) were used as a base for mathematical calculations. The results were presented in the tables to enable their easier understanding. As a result, optimization of thickeners was achieved – the best ranges of cornstarch (0.45–0.49%) as well as xanthan gum (0.15–0.17%) concentrations in cocoa syrups were selected.

PRACTICAL APPLICATION

The result of this study could be used as a guide for thickening of cocoa syrups by the application of cornstarch–xanthan gum combination, chemically nonmodified thickeners. Mathematical method tried in this study for optimization of thickeners addition could be useful for optimization of the other thickeners and additives employed for different sauces, syrups, dressings, ketchups, mayonnaises, etc.

     

淀粉糊化和回生的研究

对淀粉糊化和老化现象进行了论述，着重介绍了其影响因素，并概述了淀粉糊化和老化的测定方法。     

“东芭曲线”优化车间管理

玩具生产企业的车间管理是至关重要的,它直接关系到产品生产制造能力,是企业的硬实力。本文作者广州东芭玩具有限公司总经理、设计总监罗建平在婴儿毛绒玩具制造行业浸淫多年,在实践中通过摸索、总结,创建了能有效分析和优化生产活动的“东芭曲线”理论,本刊曾在2008年8月办刊介绍过,笔者近几年深化理论研究,指导车间管理,有利于产业效益最大化。     

复配型改良剂对蒸烤馒头老化影响的研究

馒头的老化是制约馒头工业化进程的一个关键问题。防止馒头老化较为有效的方法是在馒头的配方中添加各种可食用的乳化剂，使馒头中各纽分分散润湿良好。通过对复配型添加剂在馒头生产中的应用研究和对比实验，开发出在馒头中增添该复配型添加剂的生产工艺，有效地解决了目前馒头变硬、口感不佳、失水等问题。     

DISPERSION STATE OF PROTEIN-STABILIZED EMULSIONS

The stability of concentrated benzene-in-water emulsions emulsified by bovine serum albumin (BSA) in the presence of various concentrations of sodium chloride has been measured in the light of the coalescence kinetics. On the acid and alkaline sides of the isoelectric point of BSA (pH 4.9), the rate of coalescence between globules decreased and approached that at the isoelectric point of BSA with increasing concentrations of sodium chloride. In these systems, the interfacial tension at the benzene/aqueous BSA solution interface, and the globule size distribution in the emulsions, reached the values observed at the isoelectric point when the concentration of sodium chloride was above about 50 mM. The role of the adsorbed film of BSA on the surface of dispersed globules is considered in relation to the dissociation state of the BSA molecules.     

空间遥控主－从式智能机器人STANFORD型主机械手设计研究

介绍一种直接驱动的６自由度ＳＴＡＮＦＯＲＤ型主机械手的研制及主要特点，重点分析腕部和臂部的几项关键技术。提出了新的腕部结构和大臂平衡方法，并从位姿矩阵分析和动态力学解算诸方面论证了其合理性。