Kinetics of Cowpea Starch Gelatinization Based on Granule Swelling

Granule size measured by laser diffraction was employed to describe the gelatinization kinetics of cowpea starch. During isothermal heating of the starch suspensions over the temperature range 67-86°C, the granule mean diameter increased rapidly initially and gradually leveled off to an equilibrium value that showed both power law and exponential dependency on temperature. Gelatinization of the starch followed pseudo first-order kinetics after an initial time lag that diminished with increased heating temperature. The gelatinization rate constant increased with temperature and could be described by the Arrhenius model with an activation energy of 233.6 kJ/mole.     

Chlorination of Cake Flour and Its Effect on Starch Gelatinization

The influence of a defined chlorination on the gelatinization behaviour of different cake flours in sucrose solutions (30–60% w/w) was investigated. Besides microscopic examinations, methods were developed for the estimation of hot paste viscosity and “amylose”

1 “Amylose” will throughout this paper mean linear polymers of glucose long enough to give a blue colour with iodine, but not necessarily native amylose as exists within the starch granule.

exudation from starch granules. The findings have shown that the amount of “amylose” which is exuded from starch granules during heating, as well as paste viscosity, increases with the chlorination of flour. High positive correlations were obtained between “amylose” exudation, hot paste viscosity and cake crumb firmness. It is proposed that this increased “amylose” exudation is, via an increase of gel strength, to a large extent responsible for the prevention of high ratio cake collapse. Besides reducing “amylose” exudation the high sucrose concentrations prevailing in cake batters were also found to inhibit greatly starch breakdown by malt and fungal amylase activity.     

Rheology of Sol-Gel Thermal Transition in Cowpea Flour and Starch Slurry

A thermal scanning rigidity monitor was used to follow rheological changes during heating of cowpea flour and starch slurries. The gelantinization temperature of cowpea starch was in the range 67–78°C. For cowpea flour, in addition to starch gelatinization, a shallow plateau was observed. The starch gelatinization onset temperature shifted from 67°C for starch to 72C for 25% cowpea flour that contained 12–15% starch. The modulus (G′) of cowpea gels increased with flour concentration according to a power relationship. Rigidity of the cowpea starch and flour gels decreased at temperatures higher than 78 and 87°C, respectively.     

Viscosity Pattern of Native and Fermented Black Gram Flour and Starch Dispersions

The effects of fermentation and added NaCl on aqueous dispersions of black gram flour were studied. After fermentation the apparent viscosities of cold pastes increased significantly over that of native flour dispersions (NFD). Addition of NaCl caused considerable decrease in apparent viscosities of NFD but only marginal decrease in fermented flour dispersions (FFD). Studies on rheological constants showed that changes brought about in these by fermentation were greater than that exerted by adding NaCl. Brabender viscography indicated that peak viscosity (PV) decreased by both NaCl and fermentation. FFD with salt showed 15% increase in PV over that without salt. FFD with or without NaCl showed greater breakdown (BV) and set back (SV) viscosities, but the values were lower in comparison to NFD. Starch was isolated in 33–35% yield from native and fermented batters. Apparent viscosity in 1M KOH showed increase due to fermentation. Brabender viscography indicated a GT of ∽81°C for both starches. The PV of fermented starch increased by 13%, BV by 15% and SV by 30% over that of native. Intrinsic viscosity of starch increased considerably while solubility and swelling power increased only marginally after fermentation.     

利用差示扫描量热仪研究小米淀粉及小米粉的糊化特性

采用差示扫描量热仪（differential scanning calorimeter,DSC）研究NaCl添加量、蔗糖添加量及pH值对小米淀粉和小米粉糊化特性的影响,并用SPSS软件进行相关性及显著性分析,将小米淀粉和小米粉的糊化特性进行对比。结果表明：相同测试条件下,小米淀粉的糊化温度（包括糊化起始温度T0、峰值温度Tp、糊化终止温度Tc）比小米粉糊化温度低（2.65±0.87） ℃;糊化热焓值（ΔH）比小米粉高（2.51±0.32） J/g;添加NaCl的小米淀粉及小米粉的糊化温度比添加蔗糖的糊化温度高（4.30±1.24） ℃。酸性条件抑制小米淀粉的糊化作用,碱的存在则促进体系糊化。     

Gelatinization of Starch and Modified Starch

Gelatinization temperatures of starch and hydroxyethyl starch was determined using Differential Scanning Calorimetry (DSC), hot stage microscopy and viscography. The gelatinization temperature based on peak temperature of DSC is incorrect. Viscograph overestimates the gelatinization temperature. Hot stage microscopy based on visual observation gives the correct gelatinization temperature. DSC gives the heat of gelatinization which is helpful in estimating heat requirement during cooking of starch. Hydroxyethylation of starch reduces gelatinization temperature and heat of gelatinization for starch.     

Cooperative Test on Amylography of Milled-Rice Flour for Pasting Viscosity and Starch Gelatinization Temperature

An ICC cooperative test on Amylograph viscosity of milled-rice flour involving 11 laboratories and 4 contrasting rice samples was undertaken to determine the reproducibility of the method. The highest contribution to total variance was from sample followed by laboratory and then sample x laboratory. Only 2 of 9 laboratories showed similar peak viscosities on the samples, only 3 of 8 laboratories had similar cooked paste final viscosities, but none of 7 laboratories had similar cooled paste final viscosities using preground flour and a common method. Use of individual mills to prepare flour for the common method and use of laboratory method with preground flours increased variance due to laboratory and reduced the contribution of sample. Final gelatinization temperature of starch may be readily estimated from the apparent temperature of 20 BU intercept of the Amylograph curve of 20% preground paste from the results of 5 laboratories with 700 g · cm cartridge.     

Gelatinization of Dieffenbachia Starch

The starch grain of Dieffenbachia seguine has the shape of an elongated, flat rod, one of whose ends is rounded and the other square. Its hilum lies near the rounded end of the grain. The molecules of the central core are parallel to the long axis of the grain while those of the peripheral layer tend to be nearly perpendicular (radial) to that axis. Gelatinization makes evident a fibrillar construction in which the fibrils of the core region are elongated parallel to the long axis of the grain while those of the periphery are crossed, at a low angle to the perpendicular. Presumably the heated starch molecules contract along their long axis, becoming randomly coiled, and thereby cause radial expansion in the core and axial and tangential expansion at the periphery of the starch grain.     

玉米淀粉的粒度效应对其糊化行为影响研究

研究和探讨了经过机械微细化处理的不同粒度玉米淀粉的糊化特性，结果表明，随着玉米淀粉粒度的降低，其糊化温度下降，糊化温度区间缩小，淀粉糊的粘度下降，但热糊稳定性增加。由于微细化处理后淀粉凝沉性增强，淀粉糊的透明度随淀粉粒度的下降而降低。     

Cold Gelatinization of Starch

The cold gelatinization of starch and the subsequent leaching with water has been studied by a spectrophotometric difference method. It has been proved that the gel formation can only take place if amylose has first leached out of the starch granules and that amylopectin is the predominant gel forming component of starch.     

木糖醇对小麦淀粉和复配粉糊化及回生特性影响

以小麦淀粉为原料,把谷朊粉按小麦粉添加量的10％、12％、15％添加到小麦淀粉中配成3种复配粉,研究不同添加量木糖醇对小麦淀粉、复配粉糊化性质和回生特性的影响.结果表明:添加木糖醇后,小麦淀粉糊化温度升高;峰值黏度随着木糖醇添加量的增加呈上升趋势;添加15％、20％、25％木糖醇时,小麦淀粉的衰减值、回生值增加.添加木糖醇后,复配粉的峰值黏度、低谷黏度和最终黏度增加.随复配粉中谷朊粉含量的增加,添加相同含量木糖醇的复配粉的峰值黏度、低谷黏度、最终黏度呈下降趋势.在不同天数添加木糖醇的小麦淀粉硬度增加,且随添加量的增加,硬度呈上升趋势,说明木糖醇促进了小麦淀粉的老化;而添加木糖醇的复配粉硬度降低,且随添加量的增加,硬度呈下降趋势,表明对于复配粉,木糖醇具有保湿和抗老化作用.     

眉豆淀粉的研究

本文研究了眉豆淀粉的性质 ,实验采用日立S - 550型电子扫描显微镜拍摄了眉豆淀粉颗粒的形貌 ;用日本OlympusVanoxBHS - 2型多功能光学显微镜观察了其偏光十字 ;用日本理学D/max -IIIA型X -光衍射仪测定了X -光衍射图样及结晶结构 ;用美国Waters公司SugarAnalyerI型高效液相色谱仪测定了其淀粉的重均聚合度、数均聚合度、分子量分布及分散度等 ,并与玉米、马铃薯淀粉进行了比较。在淀粉的应用中 ,糊的性质至关重要 ,实验采用德国Viskograph -E型Brabender连续粘度计对眉豆淀粉在不同乳浓度、pH及蔗糖添加量的情况下测定其粘度曲线 ,研究了不同条件对糊粘度的影响等。将为指导生产和开发眉豆淀粉应用提供理论基础 ,具有重要意义     

Effect of Soy Flour and Maize Flour Addition on Phase Separation in Moi-Moi from Soaked Cowpea (Vigna unguiculata) and Cowpea Flour from Different Cowpea Varieties

Two improved varieties of cowpea (IT89KO and IT90K-76) and one local variety (lsiocha) were used to investigate the effects of added soyflour and maize flour on the phase separation in moi-moi made from soaked cowpea and cowpea flour. Different levels (5%, 10%, 15%, 20% and 25%) of maize flour, soyflour and a 1:1 blend of soyflour and maize flour (soy/maize flour) were separately added. The moi-moi from the different combinations was evaluated for phase separation and per cent height of the upper layer calculated. Soaking of cowpea reduced the size of the upper layer in moi-moi compared with the use of cowpea flour. The addition of maize flour or the soy/maize flour reduced the upper layer compared with when either flour was added alone. The upper layer of moi-moi made from cowpea flour with added soy flour (21.20%) was significantly higher (p < 0.05) than moi-moi from soaked cowpea with added soy flour (15.2%). Moi-moi with added maize flour made from cowpea flour produced a significantly (p < 0.05) higher mean per cent upper layer (19.72%) compared with that from soaked cowpea (8.95%). Addition of soyflour produced the greatest upper layer for all varieties used. There were no significant (p > 0.05) differences in the per cent upper layers for moi-moi from all cowpea varieties when maize flour was added. Increasing the proportion of added flours increased the size of the upper layer. Complete prevention of the occurrence of phase separation in moi-moi by addition of soy flour and maize flour alone is not feasible.     

含豇豆粉蛋糕的研制

将豇豆粉添加到面粉中制作面包,通过单因素与正交试验设计,优选出含豇豆粉蛋糕的最佳配方为:蛋糕专用粉200 g、豇豆粉30 g、鸡蛋420 g、白砂糖170 g、塔塔粉5 g、食用油50 g、水100 g、泡打粉5 g,此时所制得的含豇豆粉的蛋糕品质最佳。     

Gelatinization of Crosslinked Potato Starch

The gelatinization temperature of crosslinked potato starch suspended in water was measured as a function of the water content of the sample. The resultant data were analysed using the thermo-dynamic theory of melting in polymer-diluent systems. The dependence of the values of the thermodynamic parameters so obtained on the procedure used to analyse the data is discussed. Differences between gelatinization and melting transitions in synthetic polymer-organic diluent mixtures are considered.     

Physicochemical and Nutritional Aspects of Cowpea Flour

Cowpea (Vigna ungiiculata) flour was prepared by soaking.the beans in 25°C tap water for 18 hr, drying in an air draft, milling to a coarse powder, removing the seed coat by an air jet, autoclaving the powder at 121°C for 10 min, redrying in an air draft and grinding to a fine flour. Ths flour was creamy-white, free-flowing, nonhy-groscopic and dispersed readily in water. The conversion of cowpeas to flour resulted in 10% loss of thiamin and riboflavin and 30% loss of niacin. Also the flour contained less K, P, and Mg but more Ca and Na than the raw cowpeas.     

The Effect of Protein and Fiber on the Kinetics of Starch Gelatinization and Melting in Waxy Corn Flour

The in situ presence of corn proteins and fibers along with starch in waxy corn flour affect the DSC scan of starch only slightly. The kinetic behaviors of cooking waxy corn flour with limited water contents (25% and 35%, w/w) are very similar to that of cooking waxy cornstarch. There are increases in reaction rate constants for samples with 25% water content when corn flour data are compared to that of corn starch. For samples with 35% water, the rate constants are very close for flour and starch. Cooking of corn flour requires a lower activation energy than cooking of cornstarch.     

Concentration and Temperature Dependence of Flow Behavior of Xanthan Gum Dispersions

Apparent viscosities of xanthan gum dispersions over shear rates of 0.5–3000s^?1 were studied at concentrations of 0.05–1.00% (w/w) and temperatures of 5–45°C. All dispersions were shear rate thinning non-Newtonian fluids described accurately by the power-law model. The logarithm of viscosity varied with the logarithm of concentration and the reciprocal of absolute temperature. A combined model was derived to describe the variation of viscosity with shear rate, concentration and temperature for aqueous dispersions of xanthan gum.     

Viscosity and Gelatinization Characteristics of Hydroxyethyl Starch

Viscosity and gelatinization characteristics of corn and potato starches as well as their hydroxyethyl derivatives were investigated. The inherent viscosity increased from 164 in native corn starch to 209 in etherified one of DS 0.18. The etherified corn starch gelatinized at lower temperature than native corn starch due to their increase of DS. Maximum viscosity decreased from 93°C to 69°C for the modified corn starch. The retrogradation of starch was minimized by etherification as retrogradation ability of corn starch from its solution decrease from 22% to 6%. This is of great importance when starch is used as blood plasma volume expander. Variable results were obtained with etherified potato starch which might be due to its high contents of phosphorus.     

小麦总淀粉、A-淀粉及B-淀粉的热损伤与其糊化度、糊化特性的关系

为了探索热处理温度和水分对淀粉损伤及损伤后淀粉糊特性的影响,揭示小麦淀粉的热损伤程度与糊化度、糊黏度特性之间的关系,以市售面粉分离的总淀粉、A-淀粉和B-淀粉为原料,经30～90 ℃的温度处理后,测定其在高、低水分下的破损淀粉含量、糊化度及糊化特性的变化。结果表明：低水分下,淀粉损伤、糊化度和淀粉糊性质随热处理温度变化不明显;高水分含量下,随着热处理温度的升高,破损淀粉含量和糊化度呈明显上升趋势,热损伤程度与糊化度之间呈显著正相关（P＜0.05）,糊化温度略有增加,主要的黏度参数显著下降,损伤淀粉与峰值黏度之间呈显著负相关（P＜0.05）。