PRODUCTION OF BRINED SOFT CHEESE FROM FROZEN ULTRAFILTERED SHEEPS MILK .1. PHYSICOCHEMICAL, MICROBIOLOGICAL AND PHYSICAL STABILITY PROPERTIES OF CONCENTRATES

Some physicochemical, microbiological and physical stability changes i n sheep's milk as a result of its concentration by ultrafiltration (UF ) and long-term deep-frozen storage were studied. Skim milk was concen trated by UF to 19.37, 23.40 or 26.49% total solids (TS), mixed with c ream to obtain recombined UF concentrates with 30.40, 33.95 or 36.90% TS, respectively, and then frozen and stored at -20 degrees C for up t o 6 months. With the exception of highly concentrated milks frozen for 6 months, no significant differences in lipolysis (acid degree value) and fat oxidation (peroxide value) were observed between the control milk and the UF milk concentrates stored frozen for up to 6 months. Th e UF process resulted in significant increases in the bacterial and co liform counts in sheep's milk, which decreased during the frozen stora ge. The UF concentrates exhibited good protein stability throughout fr ozen storage, except for one obtained from milk to which 0.5% NaCl was added before UF, which destabilized after 2 months frozen storage.