Heat treatment and the defective units' ratio: surviving active spores in pea puree

The aim of the research work was to develop an experimental method to obtai n kinetic data for the thermal inactivation of micro-organisms, with regard to active survivors in the food itself. The method is based on the princip le that the number and concentration of surviving active microbes can be as sessed from the number of spoiled heat treated units (m) out of a sample co ntaining M units (1 less than or equal to m less than or equal to M - 1). C lostridium sporogenes spores have been inactivated in pea puree at 115 degr ees C and 121 degrees C. The concentration of active surviving spores has b een determined from the number of spoiled vials (units) out of samples of 5 0-50 vials at four-time periods. A very small heat resistant fraction has b een detected with D-T = 6.32 min decimal reduction time at T = 121 degrees C, z = 10.41 degrees C temperature coefficient, N-l* = 0.36 and 2.2 cm(-3) initial concentration of spores. Active survivors are understood as those a ble to multiply in the specified food after heat treatment, inactive ones d o not multiply in the food, but in a suitable culture medium. Total initial concentration (potentially active and inactive survivors) was 1.2 x 10(5) spores per cm(3). The experimental method is applicable for low survivor co ncentrations and useful for industrial application, as active survivors are detected in the food itself. Inactive survivors were also found in unspoil ed vials. (C) 2000 Elsevier Science Ltd. All rights reserved.