Egg Yolk Emulsion

Add aseptically to melted bottles of Bacillus cereus base medium cooled to 50 °C, before pouring into Petri dishes when cooled to room temperature.

Once solidified on a flat surface, spread the plates by streaking methodology or by spiral method. Incubate the plates right side up aerobically at 35-37 °C for 24-48 hours.

(Incubation times longer than those mentioned above or different incubation temperatures may be required depending on the sample, on the specifications, etc. This medium can be inoculated directly or after any enrichment broth.)

After incubation, enumerate all the colonies that have appeared on the surface of the agar.

Selective supplementation of the medium suppresses almost all the accompanying flora.

Each laboratory must evaluate the results according to their specifications.

Presumptive isolation of Bacillus sp. must be confirmed by further microbiological and biochemical tests.

Calculate total microbial count per mL of sample by multiplying the average number of colonies per plate by the inverse dilution factor if a diluted sample was streaked. Report results as colony forming units (CFU) per mL or g along with incubation time and temperature.

(according to ISO 7932:2004)

Physical/chemical control

Microbiological control

Add 10 mL of product to 90 mL of Bacillus Cereus Agar Base.

Inoculate: practical range 100 ± 20 CFU, min. 50 CFU (productivity).

Analytical methodology according to ISO 11133:2014/Amd 1:2018; A2:2020.

Aerobiosis. Incubation at 37 ± 1 °C, reading after 24-48 ± 2 h.

Sterility control

Inoculate 10 mL of product in 100 mL THIO USP / TSB. Incubate and verify in TSA.

Incubation 7 days at 30-35 °C: NO GROWTH.

• SMITH, B.A. and BAIRD-PARKER, A.C. (1964) J. Appl. Bact. 27:28.
• VANDERZANT, C. and D.F. SPLITTSTOESSER (1992) Compendium of Methods for the Microbiological Examination of Foods. 3rd. Ed. APHA. Washington.
• CeNAN. (1982). Técnicas para el Análisis Microbiológico de Alimentos y Bebidas. Madrid.
• MOSSEL, D.A.A., KOOPMAN, M.J., JONGERIUS, E. (1967) Appl. Microbiol. 15, 650-653.
• NYGREN, B. (1962) Acta Path. Microbiol. Scand. 56, Suppl. 1-160.
• ISO 7932 Standard (2004) 3rd ed. Microbiology of food and animal feeding stuffs. Horizontal method for the enumeration of presumptive Bacillus cereus. Colony count technique at 30 °C.