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Item Formation of by high power ultrasound aggregated emulsions stabilised with milk protein concentrate (MPC70)(Elsevier BV, 2021-12-03) Zhang R; Luo L; Yang Z; Ashokkumar M; Hemar YIn this work, oil-in-water emulsions stabilised by milk protein concentrate (MPC70) were investigated. The MPC70 concentration was kept constant at 5% (close to the protein content found in skim milk) and the oil volume fraction was varied from 20 to 65%. Sonication was performed at 20 kHz and at a constant power of 14.4 W for a total emulsion volume of 10 mL. Under certain oil concentration (≥35%) and sonication times (≥3s) the emulsion aggregated and formed high-viscosity pseudo plastic materials. However, the viscosity behaviour of the emulsion made with 35% oil reverted to that of a liquid if sonicated for longer times (≥15 s). Confocal laser scanning microscopy showed clearly that the oil droplets are aggregated under the sonication conditions and oil concentrations indicated above. An attempt to explain this behaviour through a simple model based on the bridging of oil droplets by the MPC70 particles and, taking into account the oil droplet and MPC70 particle sizes as well as the oil volume fraction, was made. The model fails to describe in details the aggregation behaviour of these emulsions, likely due to the inhomogeneous protein layer, where both free caseins and casein micelles are adsorbed, and to the packing of the oil droplets at concentrations ≤55%. Nonetheless, this work demonstrates the potential of ultrasound processing for the formation of dairy emulsions with tailored textures.Item Cooking of short, medium and long-grain rice in limited and excess water: Effects on microstructural characteristics and gastro-small intestinal starch digestion in vitro(Elsevier Ltd, 2021-07) Tamura M; Kumagai C; Kaur L; Ogawa Y; Singh JThe purpose of present study was to investigate the impact of cooking methods on starch hydrolysis of rice grain using an in vitro digestion model. Three varieties of short, medium and long-grain rice were cooked in two different ways: in limited water method (LWM) using a rice cooker and excess water method (EWM) using a pan. The water absorption of raw rice grain was found to differ among the different rice varieties. The moisture, crude protein, total starch and resistant starch contents of the grain were affected by the cooking method. Starch hydrolysis for medium and long-grain rice at 210 min was higher for rice cooked through LWM (75.1 and 87.5%, respectively) than those cooked using the EWM (65.8 and 64.5%, respectively). Microscopic observations of grain cooked through LWM and EWM showed that the former had bigger voids present throughout the grain and had more cell wall damage than the latter, confirming that the microstructural characteristics were responsible for better enzyme accessibility and higher starch hydrolysis. These results revealed that the starch digestibility of rice grain cooked through different methods was affected by the disruption of the tissue structure that was dependent on the cooking method.Item The viscosity and molecular conformation of galactomannans in solution : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy, Chemistry, Biochemistry, Biophysics Department, Massey University(Massey University, 1974) Sharman, Wayne RobertTwo galactomannans, from the seeds of Guar (Cyanopsis tetragonoloba) and Carob (Ceretonia siliqua) also known as Locust Bean, have found widespread use as industrial hydrocolloids. Many other galactomannans have been isolated from legume seeds, but so far none have been widely employed in industry. Measurements of the viscosity of the solutions of some of these latter galactomannans (from Red Clover, Lucerne, Lotus pedunculatus, Sophora japonica, and Soybean) were made along with solutions of Guar and Carob galactomannans. A wide range of viscosities was found for the various samples, with the viscosity of Guar and Carob galactomannan solutions being the highest. The effects of shear rate, temperature, and galactomannan concentration on the solution viscosities were examined. The measured viscosity changes correlated well with Schutz's (1970) empirical equations explaining the viscous solution behaviour of pseudoplastic carbohydrates (including Guar galactomannan). The effects on viscosity of two common industrial additives, sucrose and sodium chloride, were also examined, and interpreted in terms of a dehydration mechanism. In order to explain the viscosity results, the galactomannan molecular weights were determined by measuring their sedimentation and diffusion coefficients in an Analytical Ultracentrifuge. Their molecular weight distributions were obtained both from their Schlieren sedimentation diagrams using the method of Gralen and Langermalm (1952), and from the ratio of their apparent diffusion coefficients to their weight-average diffusion coefficients (Henley, 1962). The dependence of galactomannan intrinsic viscosities, sedimentation coefficients, and diffusion coefficients on molecular weight (weight-weight average and sedimentation-diffusion average) was examined, and a good linear correlation obtained in each case, with two exceptions. Lucerne galactomannan had a very wide distribution of molecular weights. The galactomannan from Lotus pedunculatus II was thought to differ slightly in structure from the other galactomannans due to its high substitution ratio of one galactose sidechain for every mannose in the molecular backbone which changed the conformation of the mannose backbone. The dependence of the galactomannan intrinsic viscosities, sedimentation coefficients and weight-average diffusion coefficients on the weight-weight average degree of polymerisation and/or the weight-weight average molecular weight was examined in the light of recent hydrodynamic theories. By use of the theories of Debye, Beuche and Brinkman; Kirkwood and Riseman; Kuhn and Kuhn; Peterlin; and Flory, Fox and Mandelkern it was deduced that the galactomannan molecule approximates to a random coil in solution. The molecule is highly extended, and the presence of the galactose sidechains alters its draining characteristics, making its solution behaviour deviate from that expected from the theories. Comparison of galactomannan solution behaviour with that of two soluble cellulose ethers, ethylhydroxyethyl cellulose (Manley, 1956) and hydroxyethyl cellulose (Brown, 1962) shows many similarities. It was concluded that galactomannans in solution can be treated as a linear polymer series provided that the galactose mannose ratio is not less than 1 : 5 or more than 1 : 1.1, and also that their molecular weight distributions are very similar. This implies that other galactomannans could be used industrially instead of those of Guar and Carob, provided some problems of yields and solubility could be surmounted. It was also concluded that galactomannans in aqueous solution have conformations very similar to water-soluble cellulose derivatives. Similarities between mannans and cellulose have already been proved in the solid state.Item Rheological Behavior of High-concentration Sodium Caseinate Dispersions(Wiley-Blackwell, 2010) Loveday, SM; Rao, M. A.; Creamer, Lawrence K.; Singh, HarjinderApparent viscosity and frequency sweep (G’, G”) data for sodium caseinate dispersions with concentrations of approximately 18−40% w/w were obtained at 20°C; colloidal glass behavior was exhibited by dispersions with concentration ≥ 23% w/w. The G’−G” crossover seen in temperature scans between 60 and 5°C was thought to indicate gelation (low-temperature crossover). Temperature scans from 5 to 90°C revealed gradual decrease in G’, followed by plateau values. The gelation and end of softening temperatures of the dispersions increased with the concentration of sodium caseinate. From an Eldridge−Ferry plot, the enthalpy of softening was estimated to be 29.6 kJ mol−1.Item Phase and Rheological Behavior of High-Concentration Colloidal Hard-Sphere and Protein Dispersions(Wiley-Blackwell, 2007) Loveday, SM; Creamer, Lawrence K.; Singh, Harjinder; Rao, M. A.Colloidal hard-sphere particles of narrow-size distribution exhibit crystalline and glassy states beginning at the particle volume fractions φ=0.494 and φG=0.58, respectively. Dynamic rheological data on the dispersions was strongly modified to solid-like behavior as φ approached φG. In addition, cooperative motion in structural relaxation has been observed microscopically in the colloidal dispersions near the glassy state. Very high viscosities and glassy states were also found in high-concentration dispersions of sodium caseinate, and the globular proteins: bovine serum albumin and β-lactoglobulin. Viscosity models developed for hard-sphere dispersions provided reasonable predictions of relative viscosities of colloidal protein dispersions. Dispersions of food colloidal particles may be employed in studies, in which volume fraction is the thermodynamic variable, for understanding the relaxation and transport processes related to first-order and colloidal glass transitions