Activation of Lipolysis. I.Distribution of Lipase Activity in Temperature Activated Milk

Abstract

Temperature activation did not affect lipase activity of whole milk but altered the distribution of lipase in skim milk and cream fractions. Cooling milk to 4C caused migration of lipase activity to the cream fraction. Maximum redistribution of lipase activity was achieved by the normal temperature activation treatment of warming milk from 4C to 30C and recooling. Repeated temperature activation treatments failed to increase the amount of lipase adsorbed to the cream fraction. Storage of milk at 4C for 24h or at 22C for 2h prior to temperature activation decreased lipase activity of the cream. Warming temperature-activated milk reversed the migration of lipase activity from cream to skim milk. Relationships between lipase activities of skim milk and cream from milk before and after activation indicate that a) equilibrium between the lipase activity of skim milk and cream is temperature dependent and b) distribution of lipase in milk is determined primarily by the lipid phase.