HEAT-STABILITY OF RECOMBINED MILK - INFLUENCE OF LECITHINS ON THE HEAT COAGULATION TIME-PH PROFILE

Two types of lecithin, namely egg and soya lecithin. were investigated as potential stabilizers of recombined milk. They were incorporated into recombined milk both before and after homogenization (20.7 MPa; 60-degrees-C). Their presence at homogenization changed neither mineral equilibria nor homogenization efficiency. However, heat stability varied significantly irrespective of batch of low-heat skim milk powder used in recombined milk. The variation in heat stability depended on type of lecithin. Soya lecithin proved to be a verv effective stabilizer. It improved heat stability over a wide pH range (6.3-7.1) and the effect occurred even when the lecithin was added after homogenization. ln contrast. egg lecithin destabilized the system to heat at pH < 6.7 by converting a Type A into a Type B heat coagulation time-pH profile if it was incorporated before homogenization: after homogenization it had no effect. The effects of both egg and soya lecithin on the heat stability of recombined milk strongly suggest that interactions occur between phospholipids and milk protein.