Impact of environmental factors on growth/no growth interface model of Listeria monocytogenes under different inoculum size

The growth/no growth responses of Listeria monocytogenes were monitored at different environmental factors,and inoculated concentration at four levels( 101,103,105,107 CFU/m L) by means of 10-fold dilution into tryptic soy broth added with 0.6% yeast extract( TSB-YE),and then cultivated in constant temperature incubator.The study was carried on tryptic soy agar added with 0.6% yeast extract( TSA-YE) plates and growth was monitored visually by observing the turbidity of the medium combined with plate counts. The growth/no growth interface of Listeria monocytogenes was modeled by using logistic polynomial regression.Results showed that the hurdle effects of temperature,salinity and p H had a significant influence on the growth/no growth of Listeria monocytogenes,and inoculation size also had certain impact on the specific position of transition areas on growth /no growth interface of Listeria monocytogenes,but its mechanism and more details need to be further discussed.This study provided certain references for controlling environmental factors to inhibit the growth of the Listeria monocytogenes and predicting the pollution extent in practical products.For products which have a potential risk of Listeria monocytogenes contamination,this study also provided an important reference in strengthening the hurdle factors,optimizing process conditions and improving safety for real products.