1 Method summary
The nutritional requirements, culture temperature, culture time, pH value and aerobic properties are different during culture as there are different kinds of bacteria contaminated in cosmetics, and each kind of bacteria has its own physiological characteristics. It is impossible to meet the requirements for all bacteria during practical work, so the measured results only take into account the total number of mesophilic aerobic and facultative anaerobic bacteria grown under the conditions (cultured on lecithin and Tween 80 nutrient agar at 37℃ for 48 h) used in this method.
2 Culture media and reagents
2.1 Normal saline: see GB 7918.1-87 Standard methods of microbiological examination for cosmetics - General rules.
2.2 Lecithin and Tween 80-nutrient agar medium
Composition: Peptone 20g
Beef extract 3g
Sodium chloride 5g
Agar 15g
Lecithin 1g
Tween 80 7g
Distilled water 1,000ml
Preparation method: Add lecithin to a small amount of distilled water, and heat to dissolve it; add Tween 80, and add other components (excluding agar) to the rest of distilled water, and dissolve them; add the dissolved lecithin and Tween 80, mix the mixture well, adjust pH value to 7.1~7.4, add agar, autoclave at 121℃ (151b) for 20 min, and store it in a cold and dark place for later use.
Foreword i
1 Method summary
2 Culture media and reagents
3 Apparatus
4 Operation steps
5 Method for counting colonies
6 Colony counting and methods for reporting
