Intensity of free radicals - dependent induction of VBNC state in Salmonella typhimurium within carrot juice

Hydrogen peroxide is widely used for microbial disinfection, but may induce bacteria into the viable but non-culturable (VBNC) state. However, it may induce bacteria into the VBNC state, and the underlying mechanisms remain unclear. This study employed hydrogen peroxide as a model oxidant to investigate VBNC induction in Salmonella typhimurium. VBNC formation showed a clear concentration-dependent relationship with hydrogen peroxide. Free radicals generated during treatment, including electron spin resonance (ESR) signals consistent with hydroxyl-, hydrogen-, and carbon-centered species, were associated with this transition. Among the observed signals, the hydroxyl-radical-related signal showed the highest apparent intensity under the tested conditions. A strong nonlinear association was observed between radical-related ESR signal intensity and VBNC incidence, and a constrained logistic model was used to quantitatively describe this relationship. Sodium pyruvate reduced the ESR signal and was associated with increased viable and culturable cell counts and decreased VBNC incidence at low to moderate H2O2 concentrations. Overall, the findings indicate that radical-mediated oxidative stress may be an important contributing factor to VBNC induction under the tested conditions, while the specific contributions of H2O2 and individual radical species require further investigation.