THE INFLUENCE OF TEMPERATURE AND GAS-MIXTURES ON THE GROWTH OF THE INTRINSIC MICROORGANISMS ON CUT ENDIVE - PREDICTIVE VERSUS ACTUAL GROWTH

Effects of temperature and carbon dioxide concentration on the growth of mesophilic aerobic count (MAC), psychrotrophic, Gram-negative bacte ria, pseudomonads and lactic acid bacteria were investigated in a case -study of minimally processed endive. When plotting population density against time, a distinct lag time was not observed. In a temperature range from 4.3-16.1 degrees C, both combined Arrhenius-Ratkowsky-restr icted growth models were used to model growth of these groups of micro -organisms. Temperature dependence of the growth rate constant for pse udomonads and psychrotrophic, Gramnegative bacteria were similar, wher eas the growth rate constant of the MAC was much more temperature depe ndent. A combined exponential (CO2)-Arrhenius (temperature)-restricted growth model was selected to model the number of pseudomonads and an exponential (CO2)-Ratkowsky (temperature)-restricted growth model was selected to model the growth of MAC on cut endive. The restricted grow th model was differentiated with respect to time to obtain a dynamic r estricted growth model. Temperature shift-up and shift-down experiment s were performed. Use of the Arrhenius equation for the temperature de pendence of the growth rate constant and parameter estimates obtained under constant CO2 and temperature conditions only partially allowed u s to predict the microbial evolution of minimally processed endive und er dynamic conditions. Especially under temperature shift-down conditi ons, a systematic underestimation of growth was observed. (C) 1996 Aca demic Press Limited