CONCENTRATION OF SKIM MILK AND DAIRY PRODUCTS BY FORWARD OSMOSIS

The concentration of liquid foods such as fruit-vegetable juices and milk by removing its water content is an important chemical process in terms of concentration of food nutrition, shelf-life and stability extension, decrease of the bacterial activities and cost reduction of transportation and storage. Milk can be consumed as concentrated milk by removing its water content at certain rates. Eliminating the water content in milk at certain proportions is also an essential step during several dairy product manufacture processes such as cheese, yogurt and milk powder production. In this study, milk concentration is carried out by means of forward osmosis using membrane contactors as an alternative process to conventional evaporation processes. In this process milk is circulated through the shell side of the hydrophobic membrane contactor while a draw solution of CaCl2 is circulated through the lumen side. Thus water is transferred from the milk solution to the brine solution because of the activity difference between these two solutions. In forward osmosis the effect of process parameters such as feed and draw solution rates, draw solution concentration, temperature on water fluxes was investigated and it was found that water can be removed efficiently and rapidly using this process. The concentration was carried out until the milk volume reduced in half and flux values at investigated process conditions were found to be in the range of 155-387 ml. h-1 m-2 .