Cosmetics testing · Neutralising broth
Modified Letheen Broth – neutralising broth for cosmetics
Modified Letheen Broth is a neutralising broth for the microbiological examination of cosmetics. It is used for sample dilution and enrichment in the ISO methods for cosmetics, for example ISO 21149, and in preservative efficacy testing.
- Neutralises preservatives in cosmetics
- For dilution and enrichment
- Used in ISO methods for cosmetics
How Modified Letheen Broth works
Lecithin and polysorbate 80 neutralise quaternary ammonium compounds, parabens and other preservatives. Peptones and yeast extract support recovery of bacteria, and sodium bisulfite neutralises aldehydes.
Typical growth
| Organism | Growth |
| Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa | Good growth, turbid broth |
Technical data
| Preparation | 42.8 g/L; boil to dissolve, dispense into tubes, autoclave 121 °C 15 min |
| Final pH | 7.2 ± 0.2 |
| Incubation | 32.5 ± 2.5 °C, 24 h |
| Storage | Dry, dark place; keep the container tightly closed |
| Shelf life | 3 years unopened |
Applications and practical notes
Cosmetic products contain preservatives that must be neutralised before counting and detecting micro-organisms. Neutralising media with lecithin and polysorbate 80 are used in the ISO methods for cosmetics, such as ISO 21149. Typical applications include:
- Cosmetics and toiletries
- Products with preservatives
- Disinfectant residues on surfaces
- Personal care and household products
Working with Modified Letheen Broth: Shake the sample thoroughly with the broth and allow a short contact time for neutralisation before plating.
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 pharmacopoeial microbiological testing: the European Pharmacopoeia and the USP describe harmonised methods for non-sterile products – microbial enumeration (Ph. Eur. 2.6.12, USP <61>) and tests for specified micro-organisms (Ph. Eur. 2.6.13, USP <62>) – and the sterility test for sterile products (Ph. Eur. 2.6.1, USP <71>). The chapters define the media, incubation conditions and the growth promotion test that each batch of medium must pass with reference strains. COLO.Science offers the media, diluents, neutralisers and QC strains for these tests from one source.
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.
Modified Letheen Broth is supplied by COLO.Science in the pack sizes listed under Ordering information. For larger quantities, regular deliveries or method-specific sets that include Modified Letheen Broth, please send us a request. With every delivery of Modified Letheen Broth you receive the lot number and expiry date, and on request we send the available documentation for Modified Letheen Broth.
Where Modified Letheen Broth fits in cosmetics testing
- Sample preparation – Buffered Sodium Chloride-Peptone Solution, Tryptic Soy Broth and neutralising diluents
- Microbial enumeration – Tryptic Soy Agar (TAMC) and Sabouraud Dextrose Agar (TYMC)
- Specified micro-organisms – enrichment in Tryptic Soy Broth, then MacConkey, Mannitol Salt, Cetrimide, XLD, VRBG, RCM and Columbia media
- Sterility test – Fluid Thioglycollate Medium and Tryptic Soy Broth, 14 days
See all pharmacopoeial media in the Microbiology Catalogue →
Ordering information
| Product | COLO code | Pack |
|---|---|---|
| Modified Letheen Broth | PRO7507 | 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.
Sales and technical support
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Quotations and technical support for culture media and microbiology products across our international sales territory. B2B prices are net, excluding VAT.
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Need the complete set for your method?
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.
