ASTM D8196-22

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it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D8196 − 20 D8196 − 22
Standard Practice for
Determination of Water Activity (a ) in Cannabis Flower
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This standard is issued under the fixed designation D8196; 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 is
inhibited at or below specific water activity values (3).
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 (moisture) measurement as it relates directly to the water
available to microbes. Safe a levels are constant relative to particular microbes, regardless of the
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substance being tested.
1. Scope
1.1 This practice covers the recommended procedure for determining the water activity (a ) of a cannabis flower sample.
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1.2 Units—The values stated in SI units are to be regarded as the standard. Water activity is a ratio, and thus is without unit
designation.
1.3 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.
1.4 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:
This practice 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 Dec. 1, 2020Oct. 1, 2022. Published December 2020November 2022. Originally approved in 2018. Last previous edition approved in 20182020
as D8196 – 18.20. DOI: 10.1520/D8196-20.10.1520/D8196-22.
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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D8196 − 22
D8197 Specification for Maintaining Acceptable Water Activity (a ) Range (0.55 to 0.65) for Dry Cannabis Flower Intended for
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Human/Animal Use
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 cannabis flower, n—the flowering or fruiting tops of the cannabis plant (excluding seeds and leaves when not accompanied
by flowering or fruiting top) from which the resin has not been extracted. (adapted from the UN Single Convention on Narcotic
Drugs, 1961 )
3.1.2 cultivator container, n—packaging used by cannabis grower/harvester to store and/or ship product in large quantities after
drying.
3.1.3 dispensary container, n—packaging used by a cannabis-dispensing establishment to provide the cannabis flower consumer
a satisfactory storage container.
3.1.4 packager container, n—packaging used by the packager to store and ship product to dispensing establishments.
3.1.5 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. Summary of Practice
4.1 The water activity (a ) of freshly sampled cannabis flower should be determined using a calibrated a meter. Water activity
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values are reported in a units ranging from 0.00 to 1.00.
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5. Significance and Use
5.1 This practice is designed for use on cannabis flower by cannabis producers, processors, dispensers, testing laboratories, and
end users. a testing at any point in the supply chain is an important element in ensuring the safety and quality of cannabis flower.
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Testing can occur spontaneously at any point in the supply chain by regulatory agencies, suppliers, and customers.
5.2 This practice is an important endpoint in determining whether a cannabis flower sample is being stored under optimal storage
conditions (see Specification D8197).
5.3 Analysis 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 and/or other microbiological growth and/or breakage.
5.4 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.
5.5 Water activity is used in many cases as a critical control point for Hazard Analysis and Critical Control Points (HACCP)
programs. Controlling a should not be seen as a kill step. Rather control of a focuses on preventing the growth and proliferation
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of microorganisms.
5.6 This practice is designed for use by trained technical individuals with minimal knowledge of complex analytical chemistry
procedures.
www.unodc.org/pdf/convention_1961_en.pdf, p1, accessed 2018.01.23
http://www.foodsafetynews.com/2009/12/the-kill-step-consumer/#.WodgT6jwY2w “kill step” is the term typically used to describe a point in the food manufacturing
process where potentially deadly pathogens are eradicated from the product (usually by killing the pathogen). Traditionally the “kill step” has involved cooking, pasteurization,
pathogen-killing washes, irradiation, etc. Accessed 2/16/2018.
D8196 − 22
6. Hazards
6.1 It is recommended
...