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Yeast and Molds

Use of Acidified Media. HistoricallyAcidification of Media Used to Prevent growth of Bacterial CellsInferior to Use of Antibiotic Added MediaUse Only if pH of Food is >8 CornEggsAntibiotics Not Effective at this pHAcidify to pH 5.0 with 10% tartaric acidAcidify AFTER autoclaving. Antibiotic

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Yeast and Molds

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    1. Yeast and Molds Food Microbiology Laboratory

    2. Use of Acidified Media Historically Acidification of Media Used to Prevent growth of Bacterial Cells Inferior to Use of Antibiotic Added Media Use Only if pH of Food is >8 Corn Eggs Antibiotics Not Effective at this pH Acidify to pH 5.0 with 10% tartaric acid Acidify AFTER autoclaving

    3. Antibiotic Added Media Supresses Growth of Bacterial Cells Allows Recovery of Injured Cells Minimizes precipitation of Food Particles

    4. Media Antibiotic Added Plate Count Agar Dichloran Rose Bengal Agar Yeast and Mold Enumeration using dilution Methods Use SURFACE SPREAD PLATE TECHNIQUE Hot media will kill yeast and molds

    5. Antibiotics Tetracycline Chloramphenicol** Oxytetracycline Gentamicin** Streptomycin Kanamycin **Recommended because of broad spectrum and heat tolerance (can be autoclaved, other must be added after autoclaving)

    6. Rose Bengal Restricts Excessive Mycelial Growth Do Not Expose to Light Photodegradation of rose bengal results in formation of Dichloran which can restrict mold growth

    7. Enumeration Plates should be DRIED overnight prior to plating – Prevents Spreaders Incubate UPRIGHT 22 to 25 C (room temp) for 5 days Countable Plates 15-150 colonies Do not remove plate lids Allergic Reactions DO NOT SMELL

    8. Laboratory Assignment Enumerate Yeast and Molds in Assigned Food Pre-poured Plates Yeast and Mold Petrifilm

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