Yohanes Aris Purwanto

Concentration of liquid foods by the use of gas hydrate

Abstract The formation of gas hydrate in both distilled water and coffee solutions was studied to provide the basic data for the development of liquid foods concentration by the use of gas hydrate. Experiments were carried out with xenon gas. Coffee solution samples were prepared to the concentration of 1.5, 5.1, 9.9 and 14.7 wt.%. Temperature was set from 2°C to 10°C and the range of xenon pressure was from 0.20 to 1.00 MPa. It was found that xenon hydrate could form in coffee solutions. The time required for xenon hydrate formation in coffee solutions, that is induction time, depended on the concentration of solution. Longer induction time was required for higher concentration of solution. The growth of xenon hydrate was examined through the change in size distribution of xenon hydrate with time. The effect of temperature on the size of xenon hydrate was clearly observed at the temperature–pressure condition that showed low xenon solubility. Finally, lower xenon pressure and higher temperature created the larger size of xenon hydrate crystals but it required longer time.

Separation Process of Nonpolar Gas Hydrate in Food Solution under High Pressure Apparatus

Separation process of nonpolar gas hydrate formation in liquid food was experimentally studied under high pressure container. Xenon (Xe) gas was selected as hydrate forming gas and coffee solution was used as a sample of liquid food. The high-pressure stainless steel container having the inner diameter of 60 mm and the volume of 700 mL with a U-shaped stirrer was designed to carry out this experiment. A temperature of 9.0°C and Xe partial pressure of 0.9 MPa were set as a given condition. The experiment was designed to examine the effect of steel screen size, formation rate, temperature condition, and amount of Xe gas dissolving in the solution on the separation process which was indicated by concentration efficiency. Screen size of 200 and 280 mesh resulted in higher concentration efficiency than that of 100 mesh. The higher stirring rate caused the higher formation rate of Xe hydrate and created the smaller Xe hydrate crystals. At the condition giving the same solubility in water, temperature of 14.8°C resulted in lower concentration efficiency than 9.0°C. The increase in the amount of Xe gas dissolving in coffee solution caused the concentration efficiency to decrease; however, the concentration ratio between the final and initial concentration of the solution increased.