Preservative agents in foods. Mode of action and microbial resistance mechanisms.

Preservative agents are required to ensure that manufactured foods remain safe and unspoiled. In this review, we will discuss the mode of action of both chemical and biological (nature-derived) preservatives and the stress response mechanisms induced by these compounds in microorganisms of concern to the food industry. We will discuss the challenges that food manufacturers face with respect to the assurance of food safety and the prevention of spoilage. Following this, chemical preservatives will be discussed, in particular, weak organic acids such as sorbic and benzoic acid which are widely used in preservation. Furthermore. the mechanisms of microbial inactivation with hydrogen peroxide mediated systems and chelators such as citric acid and EDTA and their potential use in preservation will be covered. We will then address the potential of naturally occurring "preservatives". Of the antimicrobial compounds present in nature, first to be discussed will be the nonproteinaceous compounds often present in herbs and spices and we will speculate on the stress response(s) that microorganisms may elicit to these natural compounds. Next to be addressed will be compounds that attack cell walls and membranes, for example, peptides, proteins and lytic enzymes. In discussing the resistance mechanisms against membrane and wall perturbation, the extensive knowledge of stress responses against osmotic stress and temperature stress will be refered to. Finally, in the concluding paragraphs, options for combination preservation systems are evaluated.