SUMMARY
Growth kinetics and proteases production of Pseudomonas fluorescens in raw milk at refrigeration temperatures
The general use of refrigeration of raw milk has contributed to maintenance of its quality, but has induced the selection of a psychrotrophic bacteria which during its growth produces heat-resistant enzymes responsible, in part, for the deterioration of long-life products. Given the condition of the prolonged refrigeration of the milk before the process, it was necessary to determine the growth curves for bacteria at temperatures between 2°C and 10°C and the kinetics of production of proteasas in raw fresh milk, inoculated with Pseudomonas fluorescens RV I O, using an automatic fermentation system, with minimal agitation under conditions of controlled temperature and pH. The results show a development over 105 ufc/mL in the cultures at 6°, 8° and 10°C during the first 30 h and proteasic activities over 30 m M p-NA/2h getting levels of de 80 - 180 m M p-NA/2h over 50 h of cultivation. Only the cultures at 2°C appeared stable with inferior cell counts and without inducing enzymatic activity. At 4°C an intermediate situation occurs.

Key words: Psychrotrophic in raw milk, heat resistance proteases, Pseudomonas fluorescens.



Recibido: 06/04/2001
Aceptado: 27/08/2001

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