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Technician Productivity Maximized 3M Food Safety 3M™ Petrifilm™ Rapid Yeast and

Technician Productivity Maximized 3M Food Safety 3M™ Petrifilm™ Rapid Yeast and Mold Count Plate The 3M™ Petrifilm™ Rapid Yeast and Mold Count Plate is a sample-ready culture medium system which contains nutrients supplemented with antibiotics, a cold-water-soluble gelling agent and an indicator system that facilitates yeast and mold enumeration. Interpretation Guide Growth and Colony Formation Yeast vs. Mold Colonies Yeast: 48 hours 25°C 25°C 28°C 28°C Mold: 48 hours Yeast: 60 hours Mold: 60 hours Yeast Count: 44 The colonies are examples of characteristic yeast: small colonies, colonies have defined edges, pink-tan to blue-green in color, colonies appear raised (3 dimensional) and colonies have a uniform color. Figure 1 Mold Count: 12 The colonies are examples of characteristic mold: large colonies, colonies have diffuse edges, blue-green to variable upon prolonged incubation, colonies appear flat and colonies have a dark center with diffused edge. Figure 2 To differentiate yeast and mold colonies on the 3M™ Petrifilm™ Rapid Yeast and Mold Count Plates, look for one or more of the following characteristics: Incubate 3M Petrifilm Rapid Yeast and Mold Count Plates at 25–28°C for 48±2 hours* in a horizontal position with the clear side up in stacks of no more than 40. Certain food types may exhibit clearer growth and colony formation at 28°C. *If colonies appear faint, allow an additional 12 hours of incubation time for enhanced interpretation. The presence of small air bubbles will not prevent accurate counts. Interpretation Guide: 3M™ Petrifilm™ Rapid Yeast and Mold Count Plate Enzymatic Reaction Count: 0 A uniform blue background color (often seen from the organisms used in cultured products) should not be counted as TNTC. Figure 3 Count: 0 A plate without an enzymatic reaction. Figure 5 Count: 5 A uniform blue background color will not prevent an accurate count. Figure 4 Count: TNTC Some foods containing high levels of enzymes may cause a uniform blue background. Colony growth will still be visible if an enzyme reaction occurs. Figure 6 Food samples may occasionally show interference on the 3M Petrifilm Rapid Yeast and Mold Count Plates, for example: 3M and Petrifilm are trademarks of 3M. Used under license in Canada. Please recycle. Printed in U.S.A. © 3M 2013. All rights reserved. 70-2011-5050-8 3M Food Safety 3M Center Building 275-5W-05 St. Paul, MN 55144-1000 USA 1-800-328-6553 www.3M.com/foodsafety 3M Canada Post Office Box 5757 London, Ontario N6A 4T1 Canada 1-800-364-3577 3M Food Safety offers a full line of products to accomplish a variety of your microbial testing needs. For more product information, visit us at www.3M.com/foodsafety or call 1-800-328-6553. Reminders for Use: 3M™ Petrifilm™ Rapid Yeast and Mold Count Plate Use appropriate sterile diluents: Butterfield’s phosphate buffer (ISO 5541-1), Buffered Peptone Water (ISO), 0.1% peptone water, peptone salt diluent, saline solution (0.85–0.90%), bisulphite-free letheen broth or distilled water. Do not use diluents containing citrate, bisulphite or thiosulfate with 3M Petrifilm Rapid Yeast and Mold Count Plates; they can inhibit growth. If citrate buffer is indicated in the standard procedure, substitute with 0.1% peptone water, warmed to 40–45°C. Place the 3M Petrifilm Rapid Yeast and Mold Count Plate on a flat, level surface. Lift the top film and with the pipette perpendicular dispense 1mL of sample suspension onto the center of bottom film. 1 Roll the top film down onto the sample. 2 Place the 3M™ Petrifilm™ Flat Spreader (6425) or other flat spreader on the center of the 3M Petrifilm Rapid Yeast and Mold Count Plate. 3 Remove the spreader and leave the 3M Petrifilm Rapid Yeast and Mold Count Plate undisturbed for at least one minute to permit the gel to form. 5 Press firmly on the center of the spreader to distribute the sample evenly. Spread the inoculum over the entire 3M Petrifilm Rapid Yeast and Mold Count Plate growth area before the gel is formed. Do not slide the spreader across the film. 4 Inoculation Procedure Read yeast and mold results at 48 hours. Certain slower growing yeasts and molds may appear faint at 48 hours. To enhance interpretation of these molds allow for an additional 12 hours of incubation time. 7 Interpretation Seal by folding the end of the pouch over and applying adhesive tape. To prevent exposure to moisture, do not refrigerate opened pouches. Store resealed pouches in a cool dry place (20–25°C/<60% RH) for no longer than 4 weeks. Rapid Yeast and Mold 8 Storage Incubate 3M Petrifilm Rapid Yeast and Mold Count Plate at 25–28°C for 48±2 hours* in a horizontal position with the clear side up in stacks of no more than 40. * If colonies appear faint, allow an additional 12 hours of incubation time for enhanced interpretation. 6 Incubation uploads/Finance/ petrifilm-guide.pdf