Behavior of Enterobacter amnigenus and Salmonella typhimurium in Crottin goat's cheese: Influence of fluctuating storage temperature

Abstract

The fully integrated cold chain is an important part in the implementation of Hazard Analysis and Critical Control Points procedures by food industry. The aim of this work was to determine the behavior of Enterobacter amnigenus (ATCC 33072 and an isolated cheese strain: LAM 200) and Salmonella typhimurium in Crottin goat's cheese during chill storage and when the cold chain is broken during different time intervals. The inoculated samples were stored in sterile bags at 5 °C for 5 days and were later divided into three groups, each with its own treatment: (A) reference (Ref) at 5 °C for a maximum period of 40 days; (B) kept along 8 h at 25 °C and then taken to 5 °C till the end of the experiment; (C) kept along 24 h at 25 °C and then taken to 5 °C till the end of the experiment. The behavior of the three strains with time in Ref experiments was analyzed with the modified Gompertz nonlinear model. In Ref treatment E. amnigenus LAM 200 did not show a lag phase but grew steadily up to K 8.1 log cfu/g; E. amnigenus ATCC 33072 did show a lag phase (7.35 days), after which it grew up to K 7.68 log cfu/g. S. typhimurium population decreased rapidly during the first 5 days. After that a second inactivation kinetics phase was observed. The behavior of E. amnigenus LAM 200 was not affected by the break in the cold chain. It seems that the cells could adapt to the stresses and fluctuating conditions. On the other hand, E. amnigenus ATCC 33072 suffered a behavior modification, as cells needed some time to acclimatize to the new conditions. The evolution of Salmonella in B treatment closely resembled Ref treatment. On the other hand in the cheese kept along 24 h at 25 °C it showed an increase of 2.4 log units after the break in the cold chain; probably as a consequence of the reparation of higher cellular numbers. It is very important factories regard GMP in order to avoid any kind of contamination, as only controlling the temperature would not be a preventive enough measure to ensure the shelf life and safety of the products.