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The Effects of hsian-tsao leaf gum (HG) on the rheological/textural properties of non-waxy starches were studied. Pronounced interactions between starch and HG were observed. The rheological properties, including pseudo-gel viscosity in the rapid visco-analyser test, storage and loss moduli in the dynamic rheological test, as well as firmness in the texture analyser test, of the mixed gels generally improved with increasing gum concentration to a certain level, then deteriorated with further increase in gum concentration. The critical gum concentration for the development of optimal rheological properties depended on the starch type and concentration. Within the concentration range studied, mixed systems with wheat starch could generally reach the highest pseudo-gel viscosity, firmness, and storage modulus if the starch/HG ratio was appropriate, followed by those with corn and tapioca starch.

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Asphaltene deposition during oil production is a major flow assurance problem. The asphaltene deposit layer reduces the pipe cross-section, leading to a significant reduction in the flow rate and eventually plugging the pipeline. This flow assurance problem caused during oil production has motivated the development of several experimental and modeling techniques to investigate the asphaltene behavior. This study proposes an integrated approach to simultaneously model asphaltene precipitation, aggregation, and deposition on a single platform. It focuses on the development of a deposition simulator that performs thermodynamic modeling using the perturbed chain version of the statistical associating fluid theory equation of state (PC-SAFT EOS) and depicts the deposition profile by means of a computational fluid dynamics (CFD) model based on the finite element method. In this work, the asphaltene deposition risk was assessed in the near-wellbore region and the production tubing as a result of gas breakthrough. To achieve this goal, a sample of crude C2 was analyzed to determine its properties and also the tendency of the asphaltenes contained in this sample to precipitate and deposit under various conditions. Laboratory-scale experiments were performed to analyze the rates of asphaltene precipitation, aggregation, and deposition. With the results obtained from the various experiments, advanced modeling methods based on PC-SAFT EOS and CFD models were calibrated and used to predict asphaltene precipitation and deposition under field conditions. Simulation methods for oil flow and asphaltene precipitation in the near-wellbore region of the reservoir and inside the production tubing were coupled to provide the most rigorous modeling approach ever developed to understand and predict this complex flow assurance problem. The results show a low to moderate asphaltene deposition rate produced by crude C2 as the gas breaks through. Nevertheless, further investigation is recommended to analyze the effect of other fluids that may be co-produced to enhance our ability to understand and predict asphaltene deposition under different conditions.

The effects of mixed gums, including decolourised hsian-tsao leaf gum (dHG) mixed with propylene glycol alginate (PGA) or xanthan gum (XG), and egg yolk concentration on the rheological properties of low-fat salad dressing model emulsions were studied. All model emulsions showed pseudoplastic flow behaviour. Model emulsions with PGA addition showed the lowest pseudoplasticity, followed by those with dHG and then XG addition. Increasing the PGA level in the dHG/PGA system reduced the pseudoplasticity. Increasing the XG level in the dHG/XG system did not change the pseudoplasticity significantly but imparted a significant increase in viscosity. Dynamic viscoelasticity measurements indicated that model emulsions with dHG or XG addition could be classified as elastic gels. However, model emulsions with PGA addition essentially belonged to the class of either dilute or concentrated solutions rheologically, depending on the egg yolk concentration. The rheological characteristics of individual gums were found to be confounded in generating the rheological characteristics of model emulsions containing them. (C) 2004 Society of Chemical Industry