Effects of Water Activity ( a w ) on Microbial Stability as a Hurdle in Food Preservation

Water activity (aw) is a major factor in preventing or limiting microbial growth. In several cases, aw is the primary parameter responsible for food stability, modulating microbial response, and determining the type of microorganisms encountered in food. This chapter covers aspects that attempt to explain why the concept of aw has been successfully applied to achieve microbial preservation of foods, its mode of action at the cellular level, and its application in food preservation along with other preservative factors, as a hurdle for microbial growth and metabolic activity. The chapter overviews hurdle techniques applied in developed countries and in Latin America, India, China, and Africa. Selected representative products from each category, the process parameters involved, and their contribution as microbial stability factors (hurdles) are also listed. The value of predictive microbiology models is becoming increasingly recognized in the design of combined technologies.