ANALYSIS OF WHEY CRYOCONCENTRATION AT SEVERAL SUCCESSIVE STAGES

In Russia, more than 50% of whey is drained as a waste product, which brings no profit and poses a threat to the environment. One possible solution to this problem is the introduction of technology of separation freezing out. The present paper is devoted to the research on the effectiveness of cryoconcentration of whey using a multistep method. Experiments were performed on separation freezing out of whey in a capacitive crystallizer. Freezing out was carried out in three stages At the first stage a coolant temperature was -4°C, at the second stage it was -5.5°C, at the third stage it was -7°C. The duration of each step was 180 min. The nonlinear relationship between the thickness of the layer of ice on the heat exchange surface and the length of whey crystallization has been established. The corresponding regression equation has been developed. Physical and chemical indices of concentrates and ice formed have been defined. It has been found that the three-stage separation freezing out improves solids content of the whey by 2 times. The structure of the resulting ice has been studied. It has been found that the ice structure is more solid when the process of freezing out is slow. The value of solids losses during separation freezing out of whey has been determined. They are 37.7, 29.5 and 27.4% of the initial content at the first, second and third stages, respectively. In this case the losses of protein and lactose at the first and third stages of concentration are approximately the same and constitute 21-25%. They are a bit higher (28-33%) at the second stage.