M.A. Tung

Relationship Between Hydrophobicity and Emulsifying Properties of Some Plant Proteins

Abstract Significant positive correlations were observed between bound dodecylsulfate or linoleate and dispersibility of surfactant treated soy, sunflower and rapeseed proteins, suggesting that the bound surfactants played an important role in solubilization of these proteins. Dispersibility was also highly correlated with effective hydrophobicity of the proteins as measured fluorometrically. The effective hydrophobicity thus determined for soy, sunflower and rapeseed proteins treated with surfactants and B. subtilis proteinase for solubilization revealed good correlations with surface tension, interfacial tension and emulsifying activity of the proteins, indicating the importance of protein hydrophobicity when used as emulsifiers.

Functional Properties of Modified Oilseed Protein Concentrates and Isolates

Abstract Some functional properties of nine oilseed concentrates and isolates were studied in order to evaluate the effects of protein source and preparation treatment on functionality. Canola (rapeseed), sunflower and soybean products were investigated, each treated during processing by enzyme hydrolysis or linoleic acid addition, or left untreated as controls. Functionality tests of water holding and hydration capacities and protein solubility were used as the bases of comparison. Protein, carbohydrate and moisture contents of the products were also determined. Both trypsin and linoleate treatments significantly affected functional properties of the products, although the treatment effects differed among sources in some cases. In general, trypsin and linoleate treatments resulted in products which exhibited higher solubilities and water hydration capacities than corresponding untreated products.

Microstructure of Rapeseed

Abstract The microstructure of the rapeseed kernel was studied by light microscopy, scanning electron microscopy and transmission electron microscopy The structural effect of mechanical dehulling was investigated and attempts were made to localize a major alkali-soluble 12 S glycoprotein. Rapeseed is a small, spherical kernel characterized by the major cell inclusions common to most oilseeds, i.e. nuclei, oil droplets and protein bodies or aleurone grains. Dehulling by pneumatic attrition produced changes in microstructure that may reflect a loss of cellular material. 12 S glycoprotein does not appear to be localized in any specific part of the seed.

Drilling fluid shear stress overshoot behavior

Shear stress overshoot behavior was studied in four drilling fluid systems and ten bentonite dispersions. These overshoot properties, also described by the American Petroleum Institute as gel strengths, were measured after gelation times of 10 s to 24 h at temperatures of 20–80 °C. Two different rheometers were used to measure overshoot behavior. Gel strength development with time followed a first-order model. Gel development rates at 20 °C varied from 0.005 to 0.01 min−1 for drilling fluid systems and from 0.0004 to 0.02 min−1 for bentonite dispersions. Increasing the gelation temperature for each drilling fluid system caused an increase in the gelling rate constant. Comparison of gel strengths in bentonite dispersions were made using a Fann 35 A viscometer and a Weissenberg Rheogoniometer. Higher gel strength values observed using the Rheogoniometer were believed to be due to differences in instrument spring stiffness and fixture inertia.

Rheograms For Power-Law Fluids Using Coaxial Cylinder Viscometers And A Template Method

Abstract A simple template method has been developed to obtain Power-Low model parameters and to enable construction of rheograms using data from coaxial cylinder viscometers. This method incorporates a shear rate correction for non-Newtonian flow in Couette rheometers with intermediate gap sizes and represents a distinct improvement over the commonly used shear rate equations. The proposed template system is valid for shear-thinning and shear-thickening power-law fluids, and does not require lengthy calculations or computer facilities. The proposed method was tested in comparison with modern computer techniques using viscometric data from two popular coaxial cylinder rheometers and selected fluid foods. For a range of shear-thinning foods less than 5% difference was found in apparent viscosity, at various shear rates, derived by template and computer methods.

Functionality of Modified Plant Proteins in Model Food Systems

Abstract Functionality of soy and canola protein isolates and sunflower protein concentrate receiving trypsin, potassium linoleate, or sodium dodecyl sulfate solubilizing treatments was tested in a model whipped topping, an oil-in-water emulsion and a model frankfurter emulsion. Foam volume and foam stability of the whipped toppings were determined, while cook stability and texture of the frankfurters were measured. Significant interactions were found between protein source and solubilizing treatment for each parameter analyzed. Performance of the proteins in the model systems was related to functional and physico-chemical properties of the plant proteins by multiple regression analyses. Protein solubility was a significant factor only for foam volume of the whipped topping model system. For the oil-in-water and frankfurter systems, factors related to protein-lipid interactions (e.g. fat absorption, apparent hydrophobicity, emulsification activity index, emulsification capacity) were most significant.

Prediction of Colour Deterioration in Strawberry Juice

Abstract The rate of colour change from red to brown in reconstituted strawberry juice at temperatures of 20, 35 and 45 °C was investigated over 12 weeks. A model was developed to explain the increase in degradation product concentration, using first order reaction kinetics. With this model, the increase in brown colour over time was studied at storage temperatures of 35 and 45°C. The loss in red colour was found to follow first order kinetics at 20, 35 and 45°C. The ratio of red colour to brown colour, often referred to as a degradation index, gradually declined with storage time but could not be modeled using empirical methods. Reaction rate constants for both the increase in brown colour and the loss in red colour were higher at 45 than 35°C. The first order model developed was accurate in predicting the rates of brown colour increase at 35 and 45°C and the rates of red colour loss at 20, 35 and 45°C.

Modelling Heat Transfer in Steam/Air Processing of Thin Profile Packages

Abstract Heat transfer studies were carried out in two pilot scale batch- type steam/air retorts to evaluate the heating rate indices (f) and lag factors (j) for thin profile test bricks of silicone rubber and nylon. Using measured surface heat transfer coefficients for the steam/air mixtures along with thermal properties and dimensions of these test bricks, corresponding f and j values were predicted by theoretical calculations. The predicted f values were within ± 6% of experimental values; however, predicted lag factors were considerably higher than experimental values when evaluated at the commonly used come-up time effectiveness factor of 42%. A relationship was established for predicting the come-up period effectiveness which showed that, during steam/air processing of thin profile packages, the effectiveness value could be over 80%. A concept identifying a “limiting surface or overall heat transfer coefficient” below which heat transfer rates could be potentially retarded was detailed.

Thermo-Rheological Changes in Protein-Replaced Meat Emulsions

Abstract Thermo-rheological profiles of a meat emulsion and dispersions of canola or soy protein isolate demonstrated that development of elasticity of the meat emulsion during heating was essentially complete at 75–80°C, whereas elasticity of canola or soy protein dispersions continued to rise with heating to 95°C. A meat emulsion containing canola protein displayed characteristics of the all-meat emulsion and canola protein dispersion thermoprofiles, but the increased structure formation from canola protein at higher temperatures did not fully compensate for an initial decrease in elasticity that resulted from the loss of meat protein.

The Ultrastructure of Commercial Wheat Gluten

Abstract Structural relationships of the component parts of wheat gluten and flour doughs were studied by electron microscopy. Consideration was given to characteristics relative to use of wheat gluten in texturized vegetable protein products. Transmission and scanning electron microscope techniques revealed that starch granules played an important role in formation of protein fibril structure and that free lipid apparently made little direct contribution to the ultrastructural relationships of component parts in the doughs. Lipoprotein derived from free lipid and protein during gluten development.was apparently very important to both protein-protein and starch-protein interaction. It is expected that these findings will be of considerable importance in optimizing the use of the unique properties of wheat gluten in texturized vegetable protein applications.