THE MOLDS OF GREATEST IMPORTANCE TO FOODS

 

Main Groups:

 

  1. Deuteromycota (Fungi Imperfecti): This is a class of septate fungi in which a sexual stage (perfect state) of the life cycle has not been observed.  The Fungi Imperfecti are essentially a provisional taxonomic grouping; if a sexual stage is observed in a fungus assigned to this group, the organism will then be assigned a new name that reflects its perfect state.

Aspergillus – Very important genus that includes species used in industrial fermentations and the production of enzymes and organic acids.  It also includes several spoilage microorganisms and two species, A. flavus and A. parasiticus, which produce carcinogenic aflatoxins.

Botrytis – Cause grey mold rot in fruits.

Penicillium – Like Aspergillus, this genus includes industrially important species as well as others that are involved in food spoilage and the production of mycotoxins.

 

  1. Ascomycota: Septate mycelium, sexual reproduction characterized by the formation of a sac-like structure called an ascus.  The ascus eventually ruptures and the enclosed spores are liberated.  This is a very large class of fungi that includes the genera Byssochlamys, and the perfect states of some fungi formerly classified under Aspergillus.

Byssochlamys – Form heat resistant spores that can survive heat treatment and result in the spoilage of high-acid canned foods, especially fruits.

 

  1. Zygomycota: A diverse group of lower, filamentous fungi which have aseptate mycelium and are capable of rapid growth.  This group has sexual and asexual modes of reproduction.  Members include the genus Rhizopus, which olds several species that cause bread molds as well as R. oligosporus, a species used in oriental soybean fermentations (tempeh).

 

Yeasts: Classified into the same group as molds, most do not live in soil but are instead found in environments with high sugar content such as the nectar of flowers or the surface of fruits.

 

Ascomycota:

Debaromyces – One of the most prevalent genera in dairy products.  D hansenii is an important food spoilage species, it can grow in 24% NaCL and at aw as low as 0.65.

 

Saccharomyces – Includes the important industrial species, S. cerevisiae, used in bread and alcoholic fermentations.  S. bailli is another important species because it is involved in the spoilage of several types of foods and is resistant to the antifungal preservatives benzoate and sorbate.

 

            Deuteromycota:

Candida – Includes the pathogen C. albicans, this genus also includes the most common species of yeasts in fresh ground beef & poultry, a few species are involved in industrial fermentations.