Adaptation of Salmonella enterica to Sequential Food-Processing Stresses: Cross-Protection, Survival and Food-Safety Implications

Food processing is still commonly evaluated one hurdle at a time. Salmonella enterica is rarely encountered in that condition: before a lethal step is applied, cells have often passed through acid, salt, desiccation, mild heat, chilling, oxidative conditions or sanitisers, and may reach a physiological state that a standardised laboratory culture does not reproduce. This review asks what that history does to survival. Prior exposure yields cross-protection, cross-sensitisation or no detectable change, according to exposure order, intensity and duration, the interval between exposures, strain and food matrix. Desiccation illustrates this: it raises tolerance to heat, ultraviolet irradiation and several sanitisers while leaving cells more vulnerable to organic acids. Stress regulators, membrane remodelling, protein maintenance and osmoprotectant accumulation underlie them, but transcriptional change is not the mechanism, and greater killing by a combination does not show that the first step sensitised survivors. Sublethal injury distorts apparent inactivation, altered virulence-associated traits do not establish greater pathogenicity, and few current predictive models capture much beyond prior sublethal heating. We therefore propose a history-aware approach: we compare conditioned with unconditioned populations under matched challenge, apply interventions in their actual sequence, and validate in the relevant matrix with recovery that detects injured survivors. Treating physiological history as a variable rather than noise should make multihurdle control of Salmonella more reliable.