3rd International Conference on Food Microbiology & Nutrition
Jiangnan University, China
Title: Induction of a viable but non-culturable state in Salmonella typhimurium is correlated with free radicals generated by thermosonication
Biography: Hongmei Liao
It was found that a small subpopulation of Salmonella typhimurium in pure culture was induced into a viable but non-culturable (VBNC) state during thermosonication (TS) processing in our previous study, though few known about the situation in real food and how bacteria were induced into that special state. Based on the speculation that free radicals generated during TS affected induction of VBNC, the relationship between them was investigated preliminarily. It was observed that higher intensity of TS treatment, such as higher power, elevated temperature and prolonged duration resulted in more viable S. typhimurium cells in carrot juice been inducted into VBNC state. The ESR spectra revealed three kinds of free radicals, including carbon centered (ethanol) radicals, hydroxyl radical and hydrogen protons were generated in carrot juice during TS processing. The intensity of free radicals was tied to the TS processing parameters and also influenced the occurrence of VBNC. A nonlinear sigmoidal curve of the intensity of free radicals VS the VBNC incidence index in three stages, including a slow phase (with free radicals intensity of 0~0.10), a rapid growth phase (with free radicals intensity ranged 0.10~0.14) and a final equilibrium phase (with free radicals intensity greater than 0.14), was observed and well fitted with the Boltzmann model. Moreover, the significance of free radicals generated during TS processing for induction of VBNC state was verified and confirmed with 0~200 mM sodium pyruvate. The obtained results may contribute to understand the complicated phenomenon and guide the application of TS as a decontamination technique.