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How should dehydrated media and peptones be stored, and how long after opening can they be used?

Written and reviewed by the STBIO technical teamPublished

Unopened

  • Store at 2 to 30 °C, dry and away from light, with the cap or bag tightly sealed.
  • The expiry on the label and specification sheet applies to unopened containers stored correctly.
  • Avoid refrigerator doors and other places where condensation forms; temperature swings do more harm than room temperature itself.

After opening

  • Dehydrated media and peptones are hygroscopic. Reseal immediately after each use; split large packs into smaller portions or add a desiccant to the pack.
  • Use within about six months of opening. If the powder is still free-flowing, the colour and odour are unchanged and the solution is clear, the product is normally still fit for use.
  • Prepared broths and plates have their own shelf life: poured plates typically keep two to four weeks refrigerated, less when they contain antibiotics or dyes.

Signs of deterioration

  • Hard caking or a clearly darker colour.
  • Cloudiness or undissolved particles after preparation.
  • pH outside specification after preparation.
  • Reduced performance: control strains grow less well than before.

Do not use a deteriorated lot for routine testing. Switch to a fresh lot and keep a sample of the old one for investigation.

Written and reviewed by the STBIO technical teamSTBIO MEDIA has produced peptones and microbial culture media since 2002, with ISO 22000 and Halal certification and an in-house QC laboratory.

Further reading

FDA BAM Culture Media Cross-Reference: Which Media Each BAM Chapter Uses and the STBIO EquivalentAerobic plate count, coliforms and E. coli, Salmonella, Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, Vibrio, Clostridium perfringens, yeasts and moulds and Cronobacter: the media named in each FDA Bacteriological Analytical Manual chapter, matched to Taiwan-made dehydrated media for US laboratories qualifying a second source.Read moreWhich Culture Media Do Taiwan FDA Food Microbiology Methods Specify? Cross-Reference for 21 Announced MethodsAerobic plate count, coliforms, E. coli, Enterobacteriaceae, Salmonella, Staphylococcus aureus, Listeria monocytogenes, lactic acid bacteria, yeasts and moulds, Bacillus cereus, Vibrio parahaemolyticus, Clostridium perfringens and Cronobacter: the media named in each Taiwan FDA (TFDA) announced method, matched to Taiwan-made products.Read moreWhat Are Casamino Acids? Casamino Acids vs Tryptone vs Casein PeptoneCasamino acids are casein hydrolysed completely with hydrochloric acid, consisting almost entirely of free amino acids. How they differ from tryptone and enzymatic casein peptone in hydrolysis, tryptophan, salt and use.Read more