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.     

A Modified Maxwell and a Nonexponential Model for Characterization of the Stress Relaxation of Agar and Alginate Gels

Compressive stress relaxation curves of agar and alginate gels of different gum concentration (1–3% and 0.5–2%, respectively) were fitted by a two parameter nonexponential empirical model and a three term modified Maxwell model with two fixed relaxation times (10 and 100s). The asymptotic portion of the residual (unrelaxed) stress calculated by the two models for each gel had a similar magnitude, and therefore could serve as an objective measure of the gels degree of solidity. The coefficients of the modified Maxwell model provided a simple but meaningful means to compare, in quantitative terms, the differences in the relaxation time spectra that were associated with the gels' stiffness and strength.     

Component Flows and Interactions in Agar Gels Predicted by Linear Irreversible Thermodynamics

Equations derived from the linear irreversible thermodynamics showed direct relationships between flow, pressure and chemical potential gradients. To predict flows, three coefficients (hydraulic permeability, solute permeability, and reflection coefficient) were introduced into the equations and measured experimentally for counter-current transfer of water and salt in agar gels. The reflection coefficient was less than 0.0003 indicating that the gel behaved as a non-selective membrane. To analyse the interactions, three interaction coefficients, for solute and water, solute and polymer network and water and polymer network were used, and expressed as a function of the former coefficients. Results showed that only salt and water interactions controlled the rate of transfer.     

Proton NMR and Dielectric Measurements on Sucrose Filled Agar Gels and Starch Pastes

Low-field proton NMR and high-frequency dielectric measurements were performed on sucrose-filled agar gels of 0 to 1.2g sucrose/g water and starch pastes of concentrations between 0.2 and lg starch/ g water. The dielectric constant decreased linearly with increasing concentration for both. The dielectric loss of sucrose-filled agar gels showed two regions, first increasing and then decreasing with concentration. The dielectric loss data for starch pastes showed a constant value close to that of pure water throughout the concentration range. Dielectric data were related to hydration models derived from proton NMR measurements.     

琼脂—聚内烯酰胺凝胶固定化干酪乳杆菌生产乳酸

将干酪乳杆菌(Lactobacillus Ceasei)细胞固定有琼脂——聚丙烯酰胺凝胶内,用于生产乳酸。研究了底物浓度,酵母膏浓度,培养温度等因素对固定化细胞生产乳酸的影响。对置换发酵过程中固定化细胞的活性及操作稳定性也进行了研究。     

Shear Stress Relaxation of Native and Modified Potato Starch Gels

Shear stress relaxation measurements were used to characterize native potato starch gels, and modified gels, such as starch acetate, distarch phosphate, dihydroxypropyl distarch phosphate and lipid coated starch. It was found that cross-linking and lipid coating greatly increased the stiffness of the gels, which was observed as increased relaxation modulus (G). These gels behaved like viscoelastic solids, which was observed as increased relaxation times (T½) and increased apparent residual moduls (G∞). During ageing, an increase in G and T½ as well as in G∞ was observed for the native starch, the starch acetate and the distarch phosphate. The hydroxypropoyl distarch phosphate and the lipid coated starch were very stable during ageing. To interpret the results in terms of the structure of the starch gel, the gel was described as a composite material, and the stress relaxation results were discussed according to a cooperative theory of flow.     

琼脂甜米酒的试制

琼脂甜米酒是以甜酒酿均质后酒基,加入１．２‰的琼脂,经灭菌处理而成,该产品介科于酒与饮料是,酷似浓牛奶,既保留了甜酒酿的风味特色和营养成分,又保留了琼脂的保健功效。     

GDL诱导改性大豆分离蛋白凝胶溶胀性的研究

讨论了乙二胺四乙酸二酐(EDTAD)改性大豆分离蛋白的制备条件,研究了葡萄糖酸内酯(GDL)诱导该改性大豆分离蛋白凝胶的溶胀性。得出2%SPI适宜的改性条件是:pH 12,温度65℃,改性大豆蛋白时EDTAD为0.6%条件下,所制备的凝胶在GDL为1.2%,所得到的凝胶溶胀率最好,并且该凝胶具有一定的pH响应性。     

Rheological Characteristics of Fibrinogen-Thrombin Solution and Its Effects on Surimi Gels

Gel enhancing effects of fibrinogen-thrombin on surimi were investigated using failure stress and analyzed by mixture design. Gelation time of fibrinogen-thrombin mixture (20:1) gradually decreased as temperature increased from 5 to 40°C, whereas the G′ and G″ values continued to decrease up to 30°C and then increased at >30°C. Low quality surimi produced higher textural values (stress and strain) when fibrinogen and thrombin mixture (3–5%) had been added. Nonlinear stepwise regression model showed no significant interaction effects between surimi and fibrinogen-thrombin mixture. However, the response trace plot showed that failure stress value of surimi gel was increased by the concentration of fibrinogen-thrombin, but decreased by water content.     

Effect of Surfactant Gels on Dough Rheological Characteristics and Quality of Bread

Sodium stearoyl-2-lactylate (SSL), diacetyl tartaric acid esters of monoglyceride (DATEM), glycerol monostearate (GMS), and distilled glycerol monostearate (DGMS) surfactant gels were made with water and varying shortening contents. The effect of these gels on dough rheological characteristics and quality of bread was investigated. Overall, the surfactant gels improved the farinograph and extensograph characteristics of wheat flour, but the improvement reduced to some extent with the presence of shortening in the gels. Alveograph data indicated that dough properties improved with the addition of surfactant gels. Shortening in gels showed varying influence on the dough alveograph properties of wheat flour. The results indicated that the surfactant gels changed the rapid visco analyzer characteristics of wheat flour, and the presence of shortening in gels further altered the characteristics. All surfactant gels improved the volume, specific volume, texture, and overall quality scores of bread, but the improvement varied for different surfactants. By increasing the addition of shortening in gels, though the quality characteristics further improved, the response to surfactants reduced by increasing shortening content.     

κ-卡拉胶对大豆分离蛋白乳浊凝胶特性的影响

研究了κ 卡拉胶在不同pH的条件下对大豆分离蛋白乳浊凝胶质构特性和流变特性的影响。研究结果表明 ,pH 7 3条件下的乳浊体系比 pH 6 8的体系更易形成凝胶。卡拉胶质量分数为 0 0 5 %时 ,因与大豆分离蛋白发生静电吸引相互作用形成连接型凝胶而显著提高了凝胶的质构特性和流变特性。 0 2 %时则形成相分离型凝胶 ,降低了凝胶的弹性和内聚性。     

状如琼，凝为脂

在我们喝的饮料粒粒橙中，为什么那些细小的橙子颗粒是悬浮在橙汁中的呢？果冻和布丁为什么是透明，且柔软有弹性的呢？去看看成分表，我们不难发现共同之处，看似不同的食品都添加了一种共同的成分——琼脂。[编者按]     

Structural Characteristics of Protein Gels as Determined by an Ultrasound Imaging Technique

Structural density features of gels formed with gelatin, egg albumen, and poultry thigh natural actomyosin were determined with an ultrasound system equipped with a real time monitor, imager and photographic unit. Echo recordings of the acoustic impedance showed that all protein gels were similar in respect to structural density differential patterns. Increases in protein concentration increased the net area occupied by protein junctions and interlinks. The ultrasound imaging technique confirmed the aggregated junction, interlink and interstitial regions that are common features of protein gels.     

Thermoirreversible Characteristics of Curdlan Gels in a Model Reduced Fat Pork Sausage

Dynamic viscoelasticity and thermal characteristics of a model reduced fat pork sausage containing curdlan were investigated. Curdlan formed thermoirreversible gels during preparation of sausage at end point temperatures that were within the range in which such gels usually transform from thermoreversible to thermoirreversible. Dynamic viscoelasticity of curdlan gels and thermal characteristics of curdlan aqueous suspensions were analyzed to help explain the physicochemical behavior of curdlan gels in sausage. Once formed curdlan gels exhibited stronger thermoirreversibility with increasing concentrations. The thermoirreversibility could be attributed to the curdlan concentration being higher than the maximum theoretical curdlan to water ratio.     

大豆分离蛋白凝胶制备和凝胶质构特性研究

本研究以大豆分离蛋白为原料，考察蛋白质浓度、pH值、加热温度、加热时间对凝胶形成的影响，采用物性仪对不同务件下制备的凝胶的质构特性进行研究，不同评价指标得出的结论不尽相同。通过正交实验得出形成凝胶硬度最大的制备条件为：蛋白浓度12％，pH值6．5，加热温度95℃，加热时间35min；形成凝胶脆性最大的制备凝胶争件为：蛋白浓度12％，pH值7．0，加热温度95℃，加热时间25min；形成凝胶弹性最好的制备凝胶务件为：蛋白浓度12％，pH值7．0，加热温度85℃，加热时间35min；形成凝胶粘附性最大的制备凝胶条件为：蛋白浓度12％，pH值7．0，加热温度95℃，加热时间35min。     

Comparison of Transparent Gels with Turbid Gels Prepared from Egg White: Creep Analysis of Gels

Egg white from which the precipitate occurring during dialysis against water had been removed gave a transparent gel on heating at lower salt concentrations and pH 3.54. The addition of NaCl or a shift of pH from 3.54 to 4.50 brought about the turbid gels. Creep analyses of these transparent and turbid gels were done using a four-element mechanical model. The instantaneous elastic modulus, E₀, Newtonian modulus, ηn and retarded viscoelastic moduli, E₁ and η₁ increased with NaCl up to 125 mM and then decreased with increase in NaCl concentration at pH 3.54. At 125 mM NaCl and pH 3.54, a translucent gel was obtained. E₀ and η₁ decreased with the temperature of the gel, while E₁ and η₁did not change depending of temperature.     

Dynamic Rheological Measurement of Structure Development in High-methoxyl Pectin/Fructose Gels

Incipient structure development (SD) in 65% fructose—0.5, 0.75, and 1% high—methoxyl (HM) pectin gels (pH 2.7) being cooled (50–10°C) were measured in terms of dynamic viscosity (η*) at 1Hz. SD rates (poise/min) were higher at lower temperatures, higher pectin concentrations, and when pectin was hydrated for 16 hr. Below the gel temperature, SD rates in 1% gel followed the Flory-Weaver model. SD in stored 0.5% gels during 22 days was strongly affected by storage temperature (2–38°C) and pH. SD rates in pH 2.7 gels were positive above, but negative below 18°C.     

Physicochemical Properties of Soybean Proteins Related to Flow, Viscoelastic, Mechanical and Water-holding Characteristics of Gels

Initial viscosity, the thixotropic relaxation time, hardness, fracturability and water-holding capacity showed a positive correlation with the water absorption capacity of commercial soy protein isolates. However, cohesiveness was negatively affected. Springiness and the degree of elasticity were correlated to the oil absorption capacity, indicating that the degree of elasticity would be enhanced by an increase in the hydrophobic character of the protein. Initial viscosity of gels was highly correlated to the fracturability and cohesiveness to water-holding properties. The degree of elasticity correlated to flow parameters.     

江蓠琼胶提胶新工艺的研究

对空气压力法提取琼胶新工艺进行了优化探讨，研究结果表明，在空气压力为0．8MPa，提胶温度为100℃，加水量为江蓠藻重的40信时，提取45min可达到最佳提取效果。以阳江细基江蓠为原料，出胶率为32．1％，与蒸汽压力提胶法出胶率相近（32．0％），比常压提胶法提高21.6％；空气压力提胶法对琼胶凝胶强度破坏少，达到860g／cm2，和常压提胶法相近（8509／cm2），比蒸汽压力提胶法所得琼胶凝胶强度高19．4％。因此，空气压力提胶法兼备常压提胶法、蒸汽压力提胶法的优点，克服了后两种提胶法的缺点。此外，还结合3种提胶方法对江蓠藻体微观结构破坏情况，以及对空气压力提胶法能加速胶质溶出、提高出胶率的原因进行了较深入的研究。     

改性瓜尔胶特征及其在特种纸中的应用

改性瓜尔胶是指在瓜尔胶原粉中引入功能基团的一类产品.该类产品能够有效地改进填料和细小纤维的留着,改善纸张的强度、透气度、表面性能等指标.改性瓜尔胶无毒副作用,适合特种纸的生产,目前已广泛应用于烟草用纸、装饰用纸等行业.