Plasmin inactivation with pulsed electric fields

Plasmin (fibrinolysin E.C.3.4.21.7), an indigenous enzyme in bovine milk, added to simulated milk ultrafiltrate (SMUF) at 100 micrograms/mL (pH 6.11 and ionic strength 0.056 M) was treated at 10 degrees C and 15 degrees C with pulsed electric fields (HVPEF) of 15, 30 and 45 kV/cm and number of pulses 10, 20, 30, 40 and 50. The plasmin activity measured using a commercial assay, was reduced 90% after 50 pulses at both 30 and 45 kV/cm and at a processing temperature of 15 degrees C. Similar inactivation was obtained when plasmin (100 micrograms/mL) in SMUF was heated at 40 degrees C for 15 min. Inactivation of the enzyme depended on the number of pulses applied during treatment, intensity of the applied field, and processing temperature