The antimicrobial paradox: why preservatives lose activity in foods

Antimicrobials are components added to foods to inhibit microbial growth or inactivate microorganisms. The use of increasingly diverse raw materials coming from a great variety of sources and regions, consumer requirements to process foods minimally to preserve as much of the original character of the raw materials as possible, and the distribution of foods over greater and greater distances, has led to a re-discovery of this traditional approach to food preservation. Nowadays, modern food antimicrobial research focuses on the development of new synthetically derived antimicrobials, or on the discovery of antimicrobially active compounds from natural sources. This has led to the introduction of many new compounds that could be used by food scientists to enhance the quality and safety of food. Unfortunately, many of these antimicrobials demonstrate excellent activities against food pathogens and spoilage organisms in model media but fail to be effective when used in complex foods. This paradox of a high activity in microbial model systems and a low activity in foods as well as the seemingly random extent of such activity losses are still not well understood. This article presents results of some relevant studies that illustrate this phenomena. From those studies, some mechanistic conclusions are derived that may be used to explain this phenomena. These could be used to better forecast activity losses of a particular antimicrobial in a given food system. Finally some conclusions highlighting future research needs are presented.