Kinetics of Trypsin Inhibitory Activity Loss in Heated Flour from Bean, Phaseolus vulgaris

The effect of temperature, time and moisture content on, trypsin inhibitory activity of bean flour was studied. Trypsin inhibitory activity loss followed first-order reaction kinetics and the rate of loss was greatly increased with increasing moisture content of flour from 2-55%. Activation energies for the first-order reaction constants were calculated and ranged between 13-27 Kcal/mole, showing a maximum value at 30% moisture content.     

Influence of Soy Protein and NaCl on the Rheological Properties of Beef, Pork or Chicken Muscle Homogenates

Yield stress, consistency index and flow behavior index of homogenates were 3.5–11.7 N/m², 6.9–14.9 N sⁿ/m², and 0.31–0.37, respectively, but with the addition of soy protein the respective values were 8.8–23.4 N/m², 15.7–34.7 N sⁿ/m², and 0.23–0.25. NaCl in the muscle homogenates changed yield stress, consistency index and flow behavior index to 17.6–26.4 N/m², 27.2–31.6 N sⁿ/m², and 0.23–0.25, respectively, but when both NaCl and soy protein were added, the respective values were 17.641 N sⁿ/m², and 0.24–0.29. Rheological parameters for homogenates containing soy protein decreased in value with NaCl addition but the magnitude of the decrease was lower when meats were present compared to the homogenate containing only soy proteins.     

Relationship of Absorptive and Interfacial Behavior of Some Food Proteins to Their Emulsifying Properties

The relationship between surface and interfacial tension of 14 food proteins and their hydrophilic/lipophilic characteristics was studied. Maximum lowering of surface and interfacial tension was achieved when the water-oil absorption index (WOAI), calculated by measuring the spontaneous water and oil uptake was nearly two; the protein absorbed twice as much water as oil. The ability of a protein to decrease interfacial tension between oil and water was related to its ability to emulsify oil, being determined by the WOAI. However, stability of emulsions was not ensured by a large decrease in interfacial tension.     

Kinetics of Water Uptake by Food Powders

The water uptake by several food materials that included animal and vegetable proteins and starch materials was studied. The amount q of water taken up by a sample powder during time t was described by the equation q = Qt/(B + t), where Q is the total water uptake of equilibrium and B is the time required to sorb Q/2. The rate of water uptake was proportional to the square of the amount of water that must still be absorbed to reach equilibrium. A specific rate constant for the process was calculated as (BQ)^?1.     

Effect of Heat Treatment on Sorption Isotherms and Solubility of Flour and Protein Isolates from Bean Phaseolus vulgaris

The effect of heating at 50, 70 or 90°C and low moisture contents on water sorption behavior (above about 0.65 water activity) and nitrogen solubility of bean flour and protein isolates, was investigated. The results suggested that relative water sorption changes, in the range studied, may not be the most adequate indicators of nitrogen solubility changes in “dry”/“moist” heated protein products. This is so because heated samples may undergo very important changes in nitrogen solubility while having experienced relatively little modifications in water sorption capacity.     

Prediction of Emulsion Instability from Emulsion Composition and Physicochemical Properties of Proteins

Emulsion instability at 37, 45 and 60°C of soy protein-stabilized emulsions of variable protein-oil concentration were systematically investigated. A regression model for prediction of emulsion instability was derived. The variables were functions of the relationship between the water and oil absorbed by the protein and total water and oil in the emulsion. The regression model derived for soy protein stabilized emulsions was suitable for predicting emulsion instability of many other protein stabilized emulsions. Knowledge of water-and-oil-absorption capacity of the protein and composition of the emulsion would allow a rapid prediction of emulsion instability.     

Water-Oil Absorption Index (WOAI): A Simple Method for Predicting the Emulsifying Capacity of Food Proteins

An index for describing the relative hydrophilic-lipophilic character of proteins was proposed based on the measurement of the “spontanoeous water and oil uptake”. The water-oil absorption index (WOAI) showed a defined correlation with emulsifying capacity (EC) for most proteins making it possible to predict EC in a simple way. Maximum emulsion capacity was achieved when the WOAI was nearly two, that is when the protein absorbed twofold more water than oil. Proteins with WAOI greater than two had increasingly hydrophilic characteristics and concomitantly increasingly low EC. Proteins with WOAI lower than two showed increasingly lipophilic characteristics and concomitantly increasing low emulsifying capacity. The finding of this study supports the concept that emulsifying capacity of proteins depends on the suitable balance between the hydrophilic and lipophilic characteristics, rather than merely high values for each one.     

水辅助激光微细加工技术进展

介绍了水辅助激光加工技术的研究现状,系统总结了水辅助激光加工技术的产生原因以及包含的主要技术内容. 针对每种水辅助激光加工技术,详细介绍了国内外研究者在理论与实验方面的主要研究成果,并对不同水辅助激光加工技术之间的技术差异和适用范围进行了论述. 水辅助激光微细加工技术在解决激光加工热损伤导致的精度损失、效率降低等方面具有明显的效果,各种形式的水辅助装置以及组合技术也为类似工程问题解决方案的拟定提供了参考价值.     

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.     

EFFECTIVE PURIFICATION PROCEDURE OF ASPERGILLUS ORYZAEα-AMYLASE FROM SOLID STATE FERMENTATION CULTURES INCLUDING CONCANAVALIN A-SEPHAROSE

Solid state fermentation cultures of Aspergillus oryzae NRRL 3485 on moistened wheat bran produced high levels of α-amylase as judged by the specific activity of water extracts (500–700 units/mg protein) and by the enzyme concentration (around 0.15 g/L) in those extracts. The purification of α-amylase by affinity chromatography on Concanavalin A-Sepharose is described. A first DEAE-Sepharose chromatography step (binding of the enzyme contained in the water extract and further elution with 0.2 M NaCl, pH 5) was necessary in order to remove contaminants that hinder the binding of the glycoprotein α-amylase to the lectin. Elution was performed with 7.5 mM α-D-methylmannoside. The enzyme was obtained highly concentrated and purified with a specific activity of 2000 units/mg protein and a recovery of around 60%, free of α-glucosidase, amyloglucosidase and color contaminants. The purity of the enzyme preparation was assessed through nondenaturing gel electrophoresis and sucrose gradient centrifugation. An improvement of the performance of the purification procedure is presented in which the maximum capacities of both the anion exchanger and the lectin matrices were exploited.