Various organic acids are used as food preservatives. Some of them are added intentionally, such as citric acid (beverages) and acetic acid (marinades); the others either occur naturally in raw
food materials or are formed in the process of production, such as lactic acid (in the fruit, vegetable, and dairy industries). Surviving of B. cereus vegetative cells in the pH found in the stomach may be considerable, when ATR has been activated for example such as may happen in low-pH food. This means that the pH of the food which vegetative cells get into GIT also plays a role in determining the level of their survival in stomach. As reported Chen et al. [29],the initial exposure to low pH increased the resistance of B. cereus to lactic, acetic, propionic, and citric acid, though to a different extent in each case. In the case of propionic acid, the resistance of the acid-adapted cells increased around 1000-fold. In contrast, the viable cell count increased only 10-fold in the case of citric acid. It was observed that both acid-adapted and non-adapted cells exhibited a similar reaction to low pH only when exposed to the stress of lactic acid [29]. It was also confirmed that the adaptation of B. cereus cells to a sublethal range of low pH values inhibited their production of the Hbl toxin [30]. Both the time of exposure and the type of organic acids (pK a ) present in the environment (e.g. in food product) affected the resistance of B. cereus to low pH e.g. in stomach. All these factors need to be taken into account when performing a detailed analysis and risk assessment of technological
processes. This rule particularly applies to processes that require acidification as the only method of preventing the development of pathogens like B. cereus