• Korean Journal of Food Science and Technology
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• v.31 no.4
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• pp.1011-1016
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• 1999

This study was performed to search a physical method having high yield and quality and minimum environmental pollution for extraction of pectin from apple pomace. Based on the physical solubilization of plant cell wall under the condition of high temperature, pressure and shearing stress, apple pomace was treated by a corotating intermeshing type twin-screw extruder with the diameter-to-length ratio of 1/20. The specific mechanical energy of extruder was introduced as system parameter for extrusion process modeling and the shaft speed, feed rate and moisture content as process variables. The yield, average molecular weight and galacturonic acid content of water-soluble polysaccharides obtained by extrusion were, respectively, modeled with the linear functions of the system parameter which was of the form as a linear function of process variables. The specific mechanical energy increased with increase of shaft speed and with decrease of feed rate and moisture content. Out of process variables, moisture content had the greatest effect on specific mechanical energy. The yield increased with increase of specific mechanical energy while the average molecular weight and galacturonic acid content increased with its decrease. In aspects of yield and quality of pectin, the results from this study showed the possibility to replace a traditional acidic method with the extrusion treatment of this study.

• Korean Journal of Food Science and Technology
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• v.16 no.2
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• pp.206-210
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• 1984

Heat penetration pattern of canned oyster mushroom(Pleurotus astreatus) was monitored for processing variables-can size, heating temperature and solid fill fraction, and its effects on sterilization condition was reviewed. The $f_h$ value decreased sharply with decrease of solid fill fraction and then became stable from certain solid fill fraction unique to can size. Heat penetration was a little faster at higher heating temperature with lower $f_h$ value. As viewed from $f_h$ value, convection started at higher solid fill fraction with higher length/diameter ratio, and $f_h$ values decreased to about 1.0 with decrease of solid fill fraction. From standpoint of overall cost, retorting time and energy consumption, solid fill fraction of 3/5 was optimum for all can sizes considered.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.52-68
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• 1991

A new propeller series is developed using the newly developed blade section(KH18 section) which behaves better cavitation characteristics and higher lift-drag ratio at wide range of angle-of-attack. The pitch and camber distributions are disigned in order to have the same radial and chordwise loading distribution with the selected circumferentially averaged wake input. Since the geometries of the series propeller, such as chord length, thickness, skew and rate distribations, are selected by regression of the recent full scale propeller geometric data, the performance prediction of a propeller at preliminary design stage can be mure realistic. Number of blades of the series propellers is 4 and the expanded blade area ratios are 0.3, 0.45, 0.6 and 0.75. Mean pitch ratios are selected as 0.5, 0.65, 0.8, 0.75 and 1.1 for each expanded area ratio. The new propeller series is composed of 20 propellers and is named as KD(KRISO-DAEWOO) propeller series. Propeller open water tests are performed at the experimental towing tank, and the cavitation observation tests and fluctuating pressure measurements are carried out at the cavitation tunnel of KRISO. $B_{P}-\delta$ curves, which can be used to select the optimum propeller diameter at the preliminary design stage, are derived from a regression analysis of the propeller often water test results. The KD-cavitation chart is derived from the cavitation observation test results by choosing the local maximum lift coefficient and the local cavitation number as parameters. The caviy extent of a propeller can be predicted more accurately by using the KD-cavitation chart at a preliminary design stage, since it is derived from the results of the cavitation observation tests in the selected ship's wake, whereas the existing cavitation charts, such as the Burrill's cavitation chart, are derived from the test results in uniform flow.