ASTM D8197-22

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Designation: D8197 − 21 D8197 − 22
Standard Specification for
Maintaining Acceptable Water Activity (a ) Range (0.55 to
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0.65) for Dry Cannabis Flower Intended for Human/Animal
Use
This standard is issued under the fixed designation D8197; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
The concept of water activity is more than 50 years old. For many years, researchers tried to equate
bacterial growth potential with water content. William Jones Scott showed in 1953 that microorgan-
isms have a limiting a level for growth (1), thus being the first to establish that bacterial growth
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correlated with water activity, not water content of organic materials. It is now generally accepted that
a is more closely related to the microbial, chemical, and physical properties of foods and other
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natural products than is total moisture (2). It is firmly established that growth of specific microbes and
metabolism of microbe associated toxins are inhibited at or below specific water activity values (3, 4).
Total water content (moisture) measurements do not necessarily reflect water available for microbial
growth and thus are an inaccurate means for controlling microbial growth, because the water content
sufficient for microbial growth is dependent on the substance being tested. Water activity measurement
is more accurate than total water content measurement as it relates directly to the water available (in
liquid form) to microbes and is constant relative to the particular microbe, regardless of the substance
being tested.
1. Scope
1.1 This specification covers the recommended range of a suitable for safe and efficacious storage of cannabis flowers or portions
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thereof.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.3 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D8196 Practice for Determination of Water Activity (a ) in Cannabis Flower
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This specification is under the jurisdiction of ASTM Committee D37 on Cannabis and is the direct responsibility of Subcommittee D37.04 on Processing and Handling.
Current edition approved Feb. 15, 2021Oct. 1, 2022. Published March 2021November 2022. Originally approved in 2018. Last previous edition approved in 20182021
as D8197 – 18.21. DOI: 10.1520/D8197-21.10.1520/D8197-22.
The boldface numbers in parentheses refer to a list of references at the end of this standard.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
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D8197 − 22
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 water activity, a ,n—the partial vapor pressure of water in a substance divided by the partial vapor pressure of pure water
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at the same temperature which is calculated by dividing the partial vapor pressure of water in the substance (P) by the partial vapor
pressure of pure water at the same temperature (P ), that is, a = P/(P ). This describes quantitatively the capability of the cannabis
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flower in a sealed container to affect the humidity of the container’s headspace air.
4. Significance and Use
4.1 This specification is designed for use on cannabis flower by cannabis producers, processors, dispensers, testing laboratories,
and end users.
4.2 Analysis and control of water activity should be considered an important quality control step in ensuring a cannabis flower
sample is being stored under optimal storage conditions to prevent mold or other microbiological growth and breakage.
4.3 All constituent testing, other than water activity in accordance with Practice D8196, shall be carried out on the cannabis flower
sample that has been equilibrated to this specification in accordance with 6.1 and 6.2.
4.4 Maintaining the requisite a throughout the supply chain from completion of drying through merchandising ensures safety and
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quality for the consumer.
4.5 Water activity (a ) is often used as a critical control point of Hazard Analysis and Critical Control Points (HACCP) programs.
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Controlling a should not be seen as a kill step. Rather control of a focu
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