**pH value**

The minimum pH is 3.80, but it all depends on the type of acid used, among which acetic acid seems to be more effective. Over the past twenty years, the survival of *Salmonella* under varying conditions of acid stress (Acid Tolerance Response ATR) has been extensively studied, especially regarding sublethal exposure with organic acids, which make the pathogen adapt to the acid used. The complex molecular mechanisms and environmental factors involved in ATR have been studied. An interesting discussion on this topic can be found in the article by Álvarez-Ordóñez *et al*. (2011). The increase in resistance to acids is very consistent, not only for the chances of survival of *Salmonella* in food, but also because it can lead the pathogen to resist to gastric pH (<1.5) and thus pass through the intestine unharmed. Generally speaking, we can say that *Salmonella* is very sensitive to acetic acid and lactic acid, while it is much more resistant to citric acid, used to acidify foods. In turn, these acids are more active if storage or treatment temperatures are close to the pathogen's minimum or maximum values of growth. Finally, we also have to underline that the acidification and/or heat treatment should not be applied to food in sublethal conditions, in order to avoid adaptation phenomena of pathogenic strains to the same treatment or even to different treatments (salt, water activity, etc.). Leyer & Johnson (1993) tested a strain of adapted to acid *S*. Typhimurium by constantly lowering the pH, finding out that the adaptation was not only due to the rebalance of intracellular pH, but also to a change in membrane proteins and not in the lipopolysaccharidic component.

#### **Disinfectants**

An incorrect method of disinfection and sanitization can make *Salmonella* persist on tools and utensils used in the food industry and kitchens, with the ability to form *biofilm* and, therefore, enable the spread of the pathogen.

Møretrø *et al*. (2009), using a treatment with a concentration of 100 ppm chlorine or 50 ppm of iodine for 15 minutes, noticed a biofilm can be completely removed, while with sodium hypochlorite (approximately 400 ppm) or cationic surfactants (benzalkonium chloride) for 5 minutes, *Salmonella* biofilm can resist on stainless steel surfaces. 70% ethanol for 5 min. is unable to remove the biofilm (Ramesh *et al*., 2002).
