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J. A. NARCISO, Citrus Research & Education Center, University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850

Physical parameters of an environment help to dictate the types of organisms capable of growth under a specific set of conditions. The microenvironments in food systems influence the growth and survival of the microorganisms found in them. As an example of this, fruit juices provide a niche for a variety of microorganisms including the filamentous fungi. Filamentous fungi are characterized by a thallus composed of microscopic “threads” that branch in all directions to cover the substrate. These organisms are capable of growth over a wide range of temperatures, osmotic potentials, pH, and oxygen availability. Environmental conditions in citrus juices are suitable to support a number of filamentous organisms. These organisms have [ sporadically] become a problem for juice processors because of changes in processing technology and the longer shelf-life of products. Filamentous fungi (molds) in juices were first studied in Britain in the 1930’s and in Europe and the United States in the 1960’s. These studies primarily looked at heat-resistant molds that were assumed to have come in on the fruit and survived thermal processing. Recent studies show that some of these fungal contaminants may be coming from the packaging, as in the case of juice held in paperboard cartons. Other sources contributing to fungal contamination of juices include propagules from air and equipment. For many years, molds in citrus juices were thought to be more a problem with the cosmetic appearance of the food rather than to have an adverse effect on food safety. Issues have been raised concerning the safety of mold contaminated fruit juices. Although no disease outbreaks from mycotoxins in citrus juices have been documented, several studies have found that mycotoxins may be produced in citrus juices inoculated with mycotoxigenic fungi, but the stability of the compounds and their concentrations are variable.