Compact Dry™ YMR

Cat. no. YMR100 Compact Dry™ YMR, 60x75mm Tray with 10x60mm Well 100 trays/box


Hardy Diagnostics Compact Dry™ YMR is a rapid, ready-to-use test method recommended for the isolation and enumeration of yeast and mold growth in raw materials, finished products, or on environmental surfaces pertaining to food and other related industries.

This product is not to be used for the diagnosis of human disease.


Fungi (yeast and mold) are a large, diverse group of organisms that can live in a wide range of environments. Most fungi are obligate aerobes and can grow in broad pH and temperature ranges. This makes them capable of thriving in many types of foods, causing various degrees of food spoilage.(1) Currently, dilution plating and direct plating methods are outlined by the FDA to detect fungi in foods.

Compact Dry™ YMR is a ready-to-use chromogenic medium for performing yeast and mold counts that contains dehydrated culture media and a cold water-soluble gelling agent in a non-woven cloth matrix. The medium is instantly hydrated when inoculated with a sample, and capillary action diffuses the sample evenly over the matrix to form a gel within seconds. Compact Dry™ YMR contains the chromogenic substrate, X-Phos that yields a blue-green reaction when utilized by most yeast species.

Compact Dry™ YMR performs comparably to plating on the Compact Dry™ YM (Cat. No. YM100), an AOAC validated (AOAC no. 100401) product. Compared to other commonly used culture systems, Compact Dry ™ has a longer shelf life, can be stored at room temperature, does not require manual sample spreading, is rigid, stackable and easy to label, and allows for direct colony picking for further subculture.


Compact Dry™ YMR contains dehydrated Potato Dextrose Agar, a gelling agent, and the chromogenic substrate 5-bromo-6-chloro-3-indoxyl phosphate (X-Phos) to assist in differentiating yeast colonies.

Final pH 5.5 +/- 0.3 at 25ºC.




Method of Use:

1. Remove the set of four trays from the foil pouch and separate each individual tray by gently bending along the connecting edge until each tray snaps free. Alternatively, if setting up a dilution series of the same sample, trays can be left connected to facilitate reading similar samples. Trays that are not used immediately should be resealed in the foil pouch. Refer to the "Storage and Shelf Life" section for proper storage of unused trays.

2. Remove the lid of the tray using two fingers to hold down one end of the lid and the thumb to lift the opposite end. Lids are easier to remove using a “peel back” method as opposed to a “pull off” method.

3. Inoculate by pipetting 1ml of sample directly to the center of a dry tray well, being careful not to touch the surface of the matrix with the pipet tip. Once dispensed, the sample will automatically diffuse across the surface by capillary action to form a gel; manual spreading of the inoculum is discouraged. Remember to account for the sample inoculum when calculating the dilution series.

4. Replace the lid and label the tray with appropriate information, including the sample dilution factor.

5. Invert the tray and incubate, upside down with the medium on top, at 25-30° C for 48-72 hours. NOTE: Use the appropriate temperature/time designation according to the legal specification of the prescribed food analysis regulation.

6. Count colonies illuminated from the backside of the tray to calculate CFU/ml using the Mini Light Box II (Cat. no. 378642000) or comparable back lighting. If the colony count is high, use the 1cm x 1cm molded grid on the back of the tray to assist in colony counting. Use a sheet of white paper with gridded lines to diffuse the light if the molded grids in the tray are difficult to visualize with a light box.


After incubation, read trays against a white background such as the Mini Light Box II (Cat. no. 378642000) or comparable back lighting.

Blue colored colonies indicate yeasts. Molds form cottony colonies with characteristic colors. Count all colonies to obtain the total yeast and mold count. The growth area is 20cm2. If the colony count is high, the total count can be obtained by multiplying the average number of colonies observed in one 1cm x 1cm square grid by 20.


Some yeasts do not form blue colonies.

High concentrations on plates (> 300 CFU) will cause the entire growth area to become green/blue. In this case dilute the sample.

During inoculation, do not touch the surface of medium and be careful to avoid any contamination by airborne microorganisms.

During incubation, keep cap tight on plates to avoid any possible dehydration.

A dilution may be needed when the sample has a dark color.

When the sample is viscous (thick), pipetting the sample on several points on a plate or an additional dilution may be needed for an even suspension.

When the sample contains an enzyme, it may react with the enzyme substrate in the dry sheet and affect the color.

If the nature of sample does affect the reaction of the medium, inoculate only after the factor is eliminated by means of dilution and other techniques. (e.g. samples with high viscosity, colored, reactive with chromogenic substrate, and with a high or low pH).

It is recommended to use a stomacher and filter homogenized sample afterwards to eliminate carry over of tiny particles of foodstuff onto the surface of the medium.

Counting colonies may be difficult against a dark background. For best results, count colonies with the tray held against a white background such as with the Mini Light Box II (Cat. no. 378642000) .

If using a light box, the molded grid lines or colonies may be difficult to view due to excessive brightness. Diffuse the light using a sheet of white, gridded (1cm x 1cm) paper underneath the tray to facilitate colony counting.

Colonies are not distinguishable on trays if concentrations are above 100 CFU/ml, as high colony counts will result in the whole surface becoming colored. The sample should be diluted to a concentration of less than 100 CFU/ml for best use.


Standard microbiological supplies and equipment such as loops, swabs such as EnviroTrans™, applicator sticks, scoops, dilution buffers such as Dilu-Lok™ II, other culture media, a light box (Cat. no. 378642000), incinerators, and incubators, etc., as well as serological and biochemical reagents, are not provided.


Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Candida glabrata
JCM® 3699
J 48-72 hrs 25-30°C Aerobic Growth; light bluish green colonies
Candida albicans
ATCC® 10231
J 48-72 hrs 25-30°C Aerobic Growth; light yellow green colonies
Aspergillus brasiliensis
ATCC® 16404
J 48-72 hrs 25-30°C Aerobic Growth; blue colonies
Bacillus subtilis
ATCC® 6633
J 48-72 hrs 25-30°C Aerobic Inhibited
Escherichia coli
ATCC® 8739
J 48- 72 hrs 25-30°C Aerobic Inhibited



Compact Dry™ YMR should appear dry, free of particles and light yellow in color.


1. Association of Official Analytical Chemists. Official Methods of Analysis. AOAC, Washington, D.C.

2. American Public Health Association. Standard Methods for the Examination of Dairy Products. APHA, Washington, D.C.

3. APHA Technical Committee on Microbiological Methods for Foods. Compendium of Methods for the Microbiological Examination of Foods. APHA, Washington, D.C.

4. U.S. Food and Drug Administration. Bacteriological Analytical Manual. AOAC, Arlington, VA.

5. American Public Health Association. Standard methods for the Examination of Water and Wasterwater. APHA, Washington, D.C.

ATCC is a registered trademark of the American Type Culture Collection.
Compact Dry is a trademark of Nissui Pharmaceutical Co., Ltd.


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