|Potassium phosphate monobasic||1.0 g|
|Magnesium sulfate heptahydrate||0.5 g|
(0.2% in ethanol, w/v)
|Distilled water||800 ml|
Mix above items and steam to dissolve agar, then bring volume to 1000 ml with distilled water. Add 220 g glycerol and sterilize by autoclaving at 121°C for 15 min. The final pH should be 5.6 and the final aw, 0.955.
This medium is used as a general purpose mold enumeration medium and is preferred when the aw of the analyzed food is 0.95 or lower. The low water activity of this medium reduces interference by bacteria and fast-growing fungi. When both yeasts and molds must be enumerated, DRBC agar should be used.
Original Source: Bacteriological Analytical Manual, 8th Edition, Revision A, 1998.