Formulation Factors Affecting the Microbial Stability of Oil-in-Water Food Emulsions

Abstract

Oil in water emulsions can support microbial growth of pathogens and spoilage microorganisms and their microbial stability is strongly influenced by oil level, inclusion of additives, preservation factors and the structure provided by the level of oil and other additives such as hydrocolloids used as stabilizers. Regarding oil level, its concentration varies between 3-5% in the case of milk, from 10 to 40% for salad dressings and can be as high as 85% for mayonnaise. Furthermore, oil droplets can be used as delivery systems to encapsulate, protect, and release bioactive hydrophobic compounds such as flavors, nutrients, antimicrobials and antioxidants. It must be stressed that system structure modifies the way of microorganism growth, in the case of liquids, it occurs planktonically. But, in structured emulsions the mobility is restricted; microorganisms are immobilized and grow as colonies. Moreover, system pH and stress factors applied determine the type of microorganism able to grow. The main objective of this chapter is to review the bibliography concerning the formulation factors affecting microbial stability of oil in water emulsions. Additionally, the interaction between microbial growth and emulsion stability was also considered. This information will help to choose the formulations and conditions that contribute to improve the food safety and quality of oil in water food emulsions.