The effects of cell immobilization, pH and sucrose on the growth of Listeria monocytogenes Scott A at 10°C Original Research Article

A study into the growth of Listeria monocytogenes Scott A investigated the effects of cell immobilization, varying sucrose concentrations (as a humectant) and alteration of initial pH at 10°C. Three conclusions were drawn from this study. Firstly, it was found that the growth rate of the organism was affected by immobilization, increasing sucrose concentrations (up to 59% w/v) and the lowering of the pH (pH 7.0 to 4.6). Secondly it was found that the lower limits of growth, in terms of pH and water activity, were different for immobilized and planktonic cultures. Lastly, it was observed that the viable population increased when planktonic cells were incubated at 10°C in combination with either low pH (pH 4.6 and 4.8) or high sucrose concentrations (59% w/v). However, this was not observed with immobilized cells, which failed to initiate growth when incubated under these conditions. Such influences of immobilization on the effects of food preservation methods are an important consideration in the predictive modelling of the survival and growth of bacteria in foods.