Yeasts and moulds · Count agar (aw ≤ 0.95)
Dichloran Glycerol Agar Base – DG18 for dry and low-moisture foods
Dichloran Glycerol (DG18) Agar Base is the medium of ISO 21527-2 for counting xerophilic moulds and osmophilic yeasts in foods with a water activity of 0.95 or less, such as cereals, flour, nuts, spices, dried fruit and honey. Glycerol is added before autoclaving.
- Medium of ISO 21527-2 (aw ≤ 0.95)
- 18 % glycerol lowers the water activity
- For cereals, spices, dried fruit and honey
How Dichloran Glycerol Agar Base works
Glycerol reduces the water activity of the medium to about 0.955, which favours xerophilic fungi. Dichloran restricts colony spreading and chloramphenicol suppresses bacteria. Osmophilic yeasts grow well, while the spreading of moulds is limited.
Typical colony appearance
| Organism | Colonies |
| Saccharomyces cerevisiae | Cream colonies |
| Aspergillus brasiliensis | Growth with restricted spreading |
| Bacteria | Inhibited |
Technical data
| Preparation | 31.6 g/L; boil to dissolve, add 200 g glycerol, autoclave 121 °C 15 min |
| Final pH | 5.6 ± 0.2 |
| Incubation | 25 ± 1 °C, 5–7 days |
| Storage | Dry, dark place; keep the container tightly closed |
| Shelf life | 3 years unopened |
Applications and practical notes
Yeast and mould counts are part of the routine quality control of food, feed, beverages and raw materials, for example according to ISO 21527-1 and FDA BAM Chapter 18. Typical applications include:
- Yeast and mould counts in food and feed
- Dairy products, bakery products, fruit and vegetables
- Spices, cereals, flour and dried foods
- Raw-material and finished-product quality control
Working with Dichloran Glycerol Agar Base: Add the glycerol before autoclaving and mix well, and incubate the plates for the full period, because xerophilic fungi grow slowly.
Good practice with dehydrated media: keep the bottle tightly closed in a cool, dry place, weigh the powder quickly to avoid moisture uptake, and use fresh distilled or deionised water. Check the pH of each new batch after preparation and before use, and label prepared media with the date. Performance of each lot can be verified with reference strains according to ISO 11133, the standard for the preparation, production, storage and performance testing of culture media.
About yeast and mould methods: in the food chain, yeasts and moulds are counted by spread plating on DRBC Agar for products with a water activity above 0.95 according to ISO 21527-1, and on DG18 Agar for drier products according to ISO 21527-2. The FDA BAM Chapter 18 describes similar plate count methods. In pharmaceutical microbiology, the total yeast and mould count (TYMC) and the test for Candida albicans use Sabouraud media according to EP 2.6.12 / 2.6.13 and USP <61> / <62>. COLO.Science offers counting media, identification media, supplements and reference strains for every step.
Complete sets from one supplier: COLO.Science supplies culture media, supplements, rapid tests, identification kits and QC strains as complete sets for the method you follow. Send us your sample types and standards, and we will prepare an offer with the matching products and documentation.
Dichloran Glycerol Agar Base is supplied by COLO.Science in the pack sizes listed under Ordering information. For larger quantities, regular deliveries or method-specific sets that include Dichloran Glycerol Agar Base, please send us a request. With every delivery of Dichloran Glycerol Agar Base you receive the lot number and expiry date, and on request we send the available documentation for Dichloran Glycerol Agar Base.
Where Dichloran Glycerol Agar Base fits in yeast and mould testing
- Food and feed counts – DRBC Agar for aw > 0.95 (ISO 21527-1) and DG18 Agar for aw ≤ 0.95 (ISO 21527-2); alternatives: Rose Bengal Chloramphenicol, PDA with chloramphenicol, YGC for dairy products
- Pharmaceutical products – Sabouraud Dextrose Agar and Broth for TYMC and the Candida albicans test (EP 2.6.12 / 2.6.13, USP <61> / <62>)
- Cultivation and identification – PDA, Malt Extract and Czapek-Dox Agar for moulds; Corn Meal, chromogenic Candida and BIGGY Agar, Yeast Nitrogen Base for yeasts
- Fermentation and QC – WL Nutrient, Wort Agar and YPD for brewing and culture yeasts; C. albicans and A. brasiliensis reference strains for media testing
See the complete yeast and mould set in the Microbiology Catalogue →
Ordering information
| Product | COLO code | Pack |
|---|---|---|
| Dichloran Glycerol Agar Base (DG18) | PRO7571 | 500 g |
Product notice: preparation, storage conditions and shelf life are given on the label. Technical data on this page are for orientation; the label and the lot documentation apply. B2B prices are quoted net, excluding VAT.
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Send the sample type, target organism and the standard you follow. COLO.Science will put together the media, supplements, QC strains and confirmation tests for the whole procedure.
