Extreme high-temperature treatment of milk with respect to plasmin inactivation

The thermal inactivation of plasmin in combination with the denaturation of β-lactoglobulin was studied using a newly developed Innovative Steam Injection (ISI) system, a direct heating system with a very short heating time combined with very high temperatures (0.2 s, 150–180 °C). The model for inactivation of plasmin was improved by integrating the effect of the formation of (partly) denatured β-lactoglobulin during pre-heating on the kinetics of plasmin inactivation. By applying these new kinetics, the heat load of milk by currently applied UHT-treatments can be reduced while obtaining a sufficient inactivation of plasmin (i.e., <1%). It turned out that it is possible to decrease the plasmin activity below 1% of the initial value and concomitantly to achieve >5.5 decimal reduction of Bacillus sporothermodurans while computer simulations showed the denaturation of β-lactoglobulin to be minimized.