Dehydrated culture media
ESTY Broth
For the cultivation of Streptococcus thermophilus in yogurt.
- Cat. No.
- LC-1254
- Category
- Dehydrated culture media
- Format
- 500 g
- Storage
- 2 to 25 °C
- Minimum guaranteed shelf life
- 15 months
ESTY Broth is a medium recommended for the growth of lactic streptococci and their bacteriophages from yogurt and other dairy products.
Key features
Applications
Selective isolation of Streptococcus.
Industry
Dairy products, food.
Preparation
37.25 g in 950 mL of distilled water; boil for one minute, sterilize in autoclave at 121 °C for 15 minutes, add 5 g of lactose.
Principles and uses
This medium is recommended for Streptococcus thermophilus isolation and enumeration in yogurt. Lactic streptococci produce acid and are difficult to grow. They are nutritionally fastidious and demand complex culture media for optimum growth. The glycerophosphate present in high concentrations acts as a pH regulator and inhibits Lactobacillus bulgaricus development, while the ascorbic acid promotes the growth of lactic streptococci. It is recommended for the maintenance of the starter cultures that produce acids in their metabolism.
Beef extract, tryptone and soy peptone provide nitrogen, vitamins, minerals and amino acids essential for growth. Yeast extract is a source of vitamins, particularly of the B-group. Disodium glycerophosphate is a buffering agent. Ascorbic acid promotes the growth of lactic streptococci. Magnesium sulphate is a magnesium ion required in a large variety of enzymatic reactions, including DNA replication, and also acts as a buffer. Bacteriological agar is the solidifying agent.
Technical specifications
| Solubility | Without residues |
|---|---|
| Appearance | Fine powder |
| Color of the dehydrated medium | Beige |
| Color of the prepared medium | Amber |
| Final pH (25 °C) | 6.9 ± 0.2 |
| Amount | 37.25 g in 950 mL |
| Storage | 2 to 25 °C |
Formula
| Ingredient | g/L |
|---|---|
| Ascorbic acid | 0.5 |
| Beef extract | 5 |
| Disodium glycerophosphate | 19 |
| Magnesium sulfate | 0.25 |
| Soy peptone | 5 |
| Tryptone | 5 |
| Yeast extract | 2.5 |
Preparation and use
Preparation
Suspend 37.25 grams of the medium in 950 mL of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. Dispense into appropriate containers and sterilize in autoclave at 121 °C for 15 minutes. Cool to 45-50 °C and aseptically add 5 grams of lactose, previously reconstituted in 50 mL of distilled water. Sterilize the lactose solution by membrane filtration.
Instructions for use
- Inoculate with 1 mL of inoculum and incubate at 30 ± 2 °C for 72 hours.
- For Streptococcus thermophilus, at 35 ± 2 °C for 24-48 hours.
Quality control
Microbiological test
Incubation conditions: 35 ± 2 °C / 24-48 h.
| Microorganism | Specification |
|---|---|
| Lactobacillus bulgaricusATCC 11842 | Inhibited growth |
| Streptococcus salivarius subsp. thermophilusATCC 19258 | Good growth |
Bibliography
- Reiter B., and J.D. Oram. 1962. Nutritional studies on cheese starters. I. Vitamin and aminoacid requirements of single strain starters. J. Dairy Res.
- International Dairy Federation 1981. Identification and enumeration of microorganisms in fermented milks.
What you receive
The product
Shipped under controlled temperature when the product requires it.
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