Dehydrated culture media
TOS Propionate Agar Base ISO
In combination with MUP, allows the direct detection of viable bifidobacteria.
- Cat. No.
- LC-2011
- Category
- Dehydrated culture media
- Format
- 500 g
- Storage
- 2 to 25 °C
- Minimum guaranteed shelf life
- 15 months
- Standards
- ISO 29981
TOS Propionate Agar Base is a medium according to ISO 29981 for the direct detection of viable bifidobacteria. The method is applicable to milk products such as fermented and non-fermented milks, milk powders, infant formulae and starter cultures, where these microorganisms are present and viable, and in combination with other lactic acid bacteria.
Supplement to be added: Selective Supplement MUP LC-6074
Key features
Applications
Detection of Bifidobacterium.
Industry
Dairy products.
Standards
ISO 29981.
Preparation
62.5 g in 990 mL of distilled water; boil for one minute, sterilize in autoclave at 115 ± 3 °C for 15 minutes.
Principles and uses
Casein peptone provides nitrogen, vitamins, minerals and amino acids essential for growth. Yeast extract is a source of vitamins, particularly of the B-group. Magnesium sulfate allows the detection of small numbers or injured bifidobacteria. Ammonium sulfate acts as a nitrogen source during growth. Potassium phosphates act as a buffer system. L-cysteine hydrochloride is the reducing agent. Transgalacto-oligosaccharide (TOS) enhances the growth of bifidobacteria used in dairy products, as it is a specific growth factor for all bifidobacteria, whereas other lactic acid bacteria cannot utilize this saccharide. Sodium propionate inhibits the accompanying flora. The antibiotic mupirocin lithium salt (MUP) inhibits the growth of most lactic acid bacteria commonly used in fermented and non-fermented dairy products.
Technical specifications
| Solubility | Without residues |
|---|---|
| Appearance | Fine powder |
| Color of the dehydrated medium | Beige |
| Color of the prepared medium | Amber |
| Final pH (25 °C) | 6.7 ± 0.2 |
| Amount | 62.5 g in 990 mL |
| Storage | 2 to 25 °C |
Formula
| Ingredient | g/L |
|---|---|
| Ammonium sulfate | 3 |
| Bacteriological agar | 15 |
| Casein peptone | 10 |
| Dipotassium phosphate | 4.8 |
| Galactooligosaccharide TOS | 10 |
| L-Cysteine hydrochloride | 0.5 |
| Magnesium sulfate heptahydrate | 0.2 |
| Monopotassium phosphate | 3 |
| Sodium propionate | 15 |
| Yeast extract | 1 |
Typical formula in g/L, adjusted and/or supplemented as required to meet performance criteria.
Preparation and use
Preparation
Suspend 62.5 grams of the medium in 990 mL of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. This medium is heat sensitive. It is recommended to autoclave small quantities (95-190 mL). Sterilize in autoclave at 115 ± 3 °C for 15 minutes. Cool to 48 °C in a water bath and, if desired, aseptically add two vials of MUP Selective Supplement (LC-6074). Homogenize gently and dispense into sterile containers.
Note: after autoclaving, the medium is slightly opalescent. The opalescence disappears when the medium is cooled to 48 ± 1 °C. The base is stable for 4 hours in a water bath.
According to ISO 29981
For the enumeration of presumptive bifidobacteria according to ISO 29981:
- Prepare the initial sample according to the raw material.
- Perform the decimal dilutions.
- Inoculate 1 mL of each dilution on empty Petri dishes. Pour 12-15 mL of the prepared propionate TOS medium. Mix the content without incorporating air.
- When the medium solidifies, incubate the plates in an anaerobic incubator at 37 °C for 72 ± 3 h.
- Counting and confirmation of colonies.
Quality control
Microbiological test
Incubation conditions: 37 °C / 72 ± 3 h.
| Microorganism | Specification | Characteristic reaction |
|---|---|---|
| Bifidobacterium breveATCC 15700 | Good growth | White colonies |
| Streptococcus salivarius subsp. thermophilusATCC 19258 | Total inhibition | |
| Lacticaseibacillus caseiATCC 393 | Total inhibition |
Bibliography
- ISO 29981/IDF 220. Milk products - Enumeration of presumptive bifidobacteria - Colony count technique at 37 °C (2010).
What you receive
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