GB/T 7918.2-1987 PDF in English
GB/T 7918.2-1987 (GB/T7918.2-1987, GBT 7918.2-1987, GBT7918.2-1987)
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| GB/T 7918.2-1987 | English | 135 |
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Standard methods of microbiological examination for cosmetics. Standard plate count
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Standards related to (historical): GB/T 7918.2-1987
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GB/T 7918.2-1987: PDF in English (GBT 7918.2-1987) GB 7918.2-1987
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
UDC 668.58:576:85.07
GB 7918.2-87
Standard methods of microbiological examination for
cosmetics - Standard plate count
ISSUED ON: MAY 28, 1987
IMPLEMENTED ON: OCTOBER 01, 1987
Issued by: Ministry of Health of PRC
Table of Contents
1 Method summary ... 3
2 Culture medium and reagents ... 3
3 Instruments ... 4
4 Operation steps ... 4
5 Colony counting method ... 5
6 Colony count and reporting method ... 5
Additional information ... 7
NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA
Standard methods of microbiological
examination for cosmetics -
Standard plate count
The total bacterial count refers to the number of live bacteria contained in 1 g or 1 ml
of cosmetics. Determining the total bacterial count can be used to determine the degree
of bacterial contamination of cosmetics, as well as the raw materials, tools and
equipment, process flow, operator hygiene used by the production organization. It is a
comprehensive basis for the hygienic evaluation of cosmetics.
This standard adopts the standard plate count method.
1 Method summary
The types of bacteria contaminating cosmetics are different; each bacterium has its own
certain physiological characteristics. The nutritional requirements, culture temperature,
culture time, pH value, aerobic properties, etc. during cultivation are different. In actual
work, it is impossible to meet the requirements of all bacteria. Therefore, the results
measured only include the total number of a group of mesophilic aerobic and facultative
anaerobic bacteria grown under the conditions used in this method (cultured at 37 °C
for 48 hours on lecithin and Tween 80 nutrient agar).
2 Culture medium and reagents
2.1 Physiological saline: See GB 7918.1-87 "Standard methods of microbiological
examination for cosmetics - General rules".
2.2 Lecithin, Tween 80 - Nutrient agar medium
Ingredients:
Peptone: 20 g
Beef extract: 3 g
Sodium chloride: 5 g
Agar: 15 g
UDC 668.58:576.85.07
GB 7918.2-87
evenly. After the agar solidifies, turn the plate over and place it in a 37 °C incubator for
48 hours.
5 Colony counting method
First observe with the naked eye and count the number of colonies. Then check with a
magnifying glass of 5 ~ 10 folds to prevent omissions. After recording the number of
colonies on each plate. Calculate the average number of colonies grown on each plate
at the same dilution. If there are colonies in the plate that are connected into sheets or
flower-like colonies that spread and grow, the plate should not be counted. If the sheet-
like colonies are less than half of the plate, whilst the number of colonies in the
remaining half is evenly distributed, THEN, the colony count of this half of the plate
can be multiplied by 2, to represent the number of colonies in the whole plate.
6 Colony count and reporting method
6.1 First, select the plates which have average colony counts between 30 ~ 300, as the
range for total colony count determination. When the average colony count of only one
dilution falls within this range, the plate colony count is multiplied by its dilution
multiple (see Example 1 in the Table).
6.2 If there are two dilutions, meanwhile their average colony counts are both between
30 ~ 300, the ratio of the total colony counts of the two shall be calculated for
determination. If the ratio is less than or equal to 2, the mean shall be reported; if it is
greater than 2, the smaller colony count shall be reported (see examples 2 and 3 in the
Table).
6.3 If the average colony counts of all dilutions are greater than 300, the average colony
count of the highest dilution multiplied by the dilution multiple shall be reported (see
example 4 in the Table).
6.4 If the average colony counts of all dilutions are less than 30, the average colony
count of the lowest dilution multiplied by the dilution multiple shall be reported (see
example 5 in the Table).
6.5 If the average colony count of all dilutions is not between 30 ~ 300, meanwhile one
dilution is greater than 300, whilst the adjacent dilution is less than 30, THEN, the
average colony count close to 30 or 300 multiplied by the dilution multiple shall be
reported (see example 6 in the Table).
6.6 If all dilutions show aseptic growth, the reported number shall be less than 10 per
gram or per milliliter.
6.7 For the report of colony count, when the colony count is within 10, it shall be
reported as the actual value. When it is greater than 100, two significant figures shall
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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