EFFECT OF MILK CONCENTRATION, PH AND TEMPERATURE ON AGGREGATION KINETICS AND COAGULATION PROPERTIES OF ULTRAFILTERED (UF) MILK

Aggregation kinetics of renneted ultrafiltered (UF) milk were monitore d by measuring the complex viscosity (mu) at various times with a Nam etre viscometer. The rate of aggregation increased with an increase in milk concentration (1X-4x) and temperature (28-37-degrees-C) and a de crease in pH (6.8-6-0). The coagulation time (CT) decreased with a dec rease in pH from 6-8 to 6.0 and with an increase in temperature. The C T decreased with an increase in milk concentration when milk pH was un adjusted (7.0), but remained unaffected when pH was adjusted by adding lactic acid (6.8 6-0). The curd firmness index increased with an incr ease in both milk concentration and temperature, and with a decrease i n pH. The aggregation kinetics suitably followed the Scott-Blair and B urnett model (mu = mu*(infinity) exp (-lambda/t*)), where mu*(infinit y) = limiting value of mu, cP; lambda = time at which mu* = mu*(infin ity)/e, min and t = time after aggregation, min.