Designing and ManufacturingMilk Pasteurization Apparatus by Ohmic Heating and studying Its Efficiency

Abstract

A device for pasteurizing milk by ohmic heating was designed, manufactured, and its efficiency was studied and tested. This device pasteurizes milk and consist of the following parts : raw milk tank made ofstainless steel double jacket of 25L capacity, feed pump , heat exchanger of 120 cm length and 1.25 cm diameter , heating tube made of Teflon of 36 cm length and 5cm diameter .and stainless steel electrodes that heat milk at three different voltage 220 ,110,80 V . These electrodes are organized in the tube in parallel way and the distance between them is 5.5cm. The device also included a holding tube of 4cm length and 1cm diameter to hold milk for 15sec. at 72°C ,It has an electric valve , delivery valve and manual valves. The results have shown the following:The perfect voltage for milk pasteurization by using ohmic heating is 80Vwhich gave milk of good quality , while 110,220Vgave milk of bad quality. The electric conductivity and trend are increased with the increase of temperature in the ohmic heating at 220,110,80V and decreased with the increase of temperature at 220V. The period of keeping milk in the device decreased with the increase of voltage in the ohmic heating which was less than HTST. Heating speed increased as applied potential difference increased and it was higher when using heating for all potential differences than conventional heating and HTST. Productivity amounted to ohmic heating device when 220, 110, 80V and conventional pasteurization rapid 25.2, 23.3, 23.3, 5 L /h respectively . Characterize ohmic heating on the V 80 as the highest coefficient of performance was 0.80, compared with 220 110, which was then the performance coefficient of 0.49, 0.76 respectively . Tested chemical , microbial and phosphatase test indicate the efficiency of pasteurization by ohmic heating .