1、Designation: D8196 18Standard Practice forDetermination of Water Activity (aw) in Cannabis Flower1This standard is issued under the fixed designation D8196; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、 A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONThe concept of water activity is more than 50 years old. For many years, researchers tried to equatebacterial growth potential with
3、water content. William Jones Scott showed in 1953 that microorgan-isms have a limiting awlevel for growth,2thus being the first to establish that bacterial growthcorrelated with water activity, not water content of organic materials. It is now generally accepted thatawis more closely related to the
4、microbial, chemical, and physical properties of foods and othernatural products than is total moisture.3It is firmly established that growth of specific microbes isinhibited at or below specific water activity values.4Total water content (moisture) measurements do not necessarily reflect water avail
5、able for microbialgrowth and thus are an inaccurate means for controlling microbial growth, because the water contentsufficient for microbial growth is dependent on the substance being tested. Water activity measurementis more accurate than total water content (moisture) measurement as it relates di
6、rectly to the wateravailable to microbes. Safe awlevels are constant relative to particular microbes, regardless of thesubstance being tested.1. Scope1.1 This practice covers the recommended procedure fordetermining the water activity (aw) of a cannabis flowersample.1.2 UnitsThe values stated in SI
7、units are to be regardedas the standard. Water activity is a ratio, and thus is withoutunit designation.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, hea
8、lth, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of Interna
9、tional Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:5D8197 Specification for Maintaining Acceptable Water Ac-tivity (aw) Range (0.55 to 0.65) for Dry Cannabis Flower3. Terminology3.1
10、 Definitions of Terms Specific to This Standard:3.1.1 cannabis flower, nthe flowering or fruiting tops ofthe cannabis plant (excluding seeds and leaves when notaccompanied by flowering or fruiting top) from which the resinhas not been extracted. (adapted from the UN Single Conven-tion on Narcotic Dr
11、ugs, 19616)3.1.2 cultivator container, npackaging used by cannabisgrower/harvester to store and/or ship product in large quantitiesafter drying.3.1.3 dispensary container, npackaging used by acannabis-dispensing establishment to provide the cannabisflower consumer a satisfactory storage container.1T
12、his practice is under the jurisdiction of ASTM Committee D37 on Cannabisand is the direct responsibility of Subcommittee D37.04 on Processing andHandling.Current edition approved May 15, 2018. Published May 2018. DOI: 10.1520/D8196-18.2Scott, W.J., Water relations of Staphylococcus aureus at 30. Aus
13、tralian Journalof Biological Sciences6, 1953, pp 549-564.3Chirife, J. and Fontana, A. J. (2007) Introduction: Historical Highlights ofWater Activity Research, in Water Activity in Foods: Fundamentals and Applica-tions (eds G. V. Barbosa-Cnovas, A. J. Fontana, S. J. Schmidt and T. P. Labuza),Blackwel
14、l Publishing Ltd, Oxford, UK. doi: 10.1002/9780470376454.ch14Russell, N.J., Leistner, L., and Gould, G.W. Solutes and Low Water Activity inFood Preservatives ed N.J. Russell and G.W. Gould, Springer 2012, pp119ff.5For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Cu
15、stomer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.6www.unodc.org/pdf/convention_1961_en.pdf, p1, Accessed 2018.01.23Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocke
16、n, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organizat
17、ion Technical Barriers to Trade (TBT) Committee.13.1.4 packager container, npackaging used by the pack-ager to store and ship product to dispensing establishments.3.1.5 water activity, aw,nthe partial vapor pressure ofwater in a substance divided by the partial vapor pressure ofpure water at the sam
18、e temperature which is calculated bydividing the partial vapor pressure of water in the substance (P)by the partial vapor pressure of pure water at the sametemperature (Po), i.e., aw= P/(Po). This describes quantita-tively the capability of the cannabis flower in a sealed containerto affect the humi
19、dity of the containers headspace air.4. Summary of Practice4.1 The water activity (aw) of freshly sampled cannabisflower should be determined using a calibrated awmeter. Wateractivity values are reported in awunits ranging from 0.00 to1.00.5. Significance and Use5.1 This practice is designed for use
20、 on cannabis flower bycannabis producers, processors, dispensers, testinglaboratories, and end users. awtesting at any point in the supplychain is an important element in ensuring the safety and qualityof cannabis flower. Testing can occur spontaneously at anypoint in the supply chain by regulatory
21、agencies, suppliers, andcustomers.5.2 This practice is an important endpoint in determiningwhether a cannabis flower sample is being stored under optimalstorage conditions (see Specification D8197).5.3 Analysis of water activity should be considered animportant quality control step in ensuring a can
22、nabis flowersample is being stored under optimal storage conditions toprevent mold and/or other microbiological growth and/orbreakage.5.4 Maintaining the requisite awthroughout the supplychain from completion of drying through merchandising en-sures safety and quality for the consumer.5.5 Water acti
23、vity is used in many cases as a critical controlpoint for Hazard Analysis and Critical Control Points(HACCP) programs. Controlling awshould not be seen as a killstep.7Rather control of awfocuses on preventing the growthand proliferation of microorganisms.5.6 This practice is designed for use by trai
24、ned technicalindividuals with minimal knowledge of complex analyticalchemistry procedures.6. Hazards6.1 It is recommended that cannabis flower samples behandled with gloved (oil and moisture resistant) hands or toolsto ensure no direct contact between skin and the sample.7. Testing Facilities and Pe
25、rsonnel7.1 All testing shall be carried out in a location of stabletemperature (constant 61 C and humidity (constant 65%relative humidity) in a temperature/humidity range of 15-50C/50-80 % relative humidity (typically 25 C) that hasminimal drafts.7.2 Personnel shall be trained in the proper handling
26、 ofcannabis flower samples using gloved hands or tools to preventskin contact, operation of the awinstrument, and routinemaintenance of the awinstrument.8. Apparatus8.1 Use gloves of non-absorbent material or tools such astongs or spatula that ensure no contact between skin andsample to prevent tran
27、sfer of water (in the liquid state) to orfrom the sample.8.2 Use an awmeasurement system (also known as a wateractivity meter) capable of: awmeasurement resolution of 0.001aw, awaccuracy of 60.005 aw, temperature measurementresolution of 0.1 C, temperature accuracy of 60.1 C, and anawmeasurement ran
28、ge of 0.40 to 0.80 awor greater. Instrumentmay be test cup based or probe based. Maintain the instrumentper the manufacturers directions.8.3 If sample must be ground, use a cannabis grinder with avolume capacity approximating that of the flower to be groundto minimize impact on awdue to evaporation
29、or compression.9. Calibration9.1 Calibrate the awinstrument per the manufacturersinstructions.9.2 Calibrate using certified 0.50 and 0.76 awstandards tobracket the desired awrange.9.3 Calibration Frequency:9.3.1 If the awinstrument is being used in a single locationat the same temperature (61 C) and
30、 humidity (65 % relativehumidity), calibrate if it has been more than seven consecutivedays since the last calibration.9.3.2 If the awinstrument is physically moved from onelocation to another, calibrate immediately following the move.9.3.3 If the awinstrument has been cleaned, then calibrateimmedia
31、tely following the cleaning.NOTE 1Some operators find it helpful to track room temperature andhumidity by operating the instrument with an empty test cup or a probesuspended in the air to determine the awand temperature of the roomwhere testing is taking place. If questions arise regarding accuracy
32、of testresults, room data can provide insight as to whether water in its liquidstate, (i.e. moisture) may or may not be transferring to or from the sampleduring testing.10. Sampling and Handling Considerations10.1 Sample directly from the original cultivator/packager,dispensary container. The sample
33、 shall be in that containeruntil the testing procedure (11.1) is initiated.10.2 Once removed from the container, testing shall be donein less than 10 minutes to minimize the impact of roomtemperature and relative humidity. Working in a temperatureand humidity controlled glove box is recommended.7htt
34、p:/ “kill step” is the term typically used to describe a point in the foodmanufacturing process where potentially deadly pathogens are eradicated from theproduct (usually by killing the pathogen). Traditionally the “kill step” has involvedcooking, pasteurization, pathogen-killing washes, irradiation
35、, etc. Accessed 2/16/2018.D8196 18210.3 If a specimen of the sample needs to be submitted to alaboratory, select a clean, sealable container with adequatevapor barrier properties (e.g., glass, metal, foil coated orembedded), which holds 1-2 g of sample. With gloved hands orusing appropriate tool(s),
36、 select a representative portion of thematerial to be tested and fill the sealable container. Thecontainer shall be sealed in less than 2 min so that the specimenis not affected by the humidity in the sampling area.11. Procedure11.1 Using gloved hands or a spatula/tongs (avoid directskin contact wit
37、h the sample), select a statistically relevantrepresentative portion of the material to be tested.11.2 Place the sample (complete cannabis flower(s) orground sample) in the test cup and fill the cup approximatelyhalf full ensuring to cover the bottom of the cup. Complete thisstep within 2 min to avo
38、id the humidity of the room influencingthe cannabis flower sample test result.11.3 Place the test cup containing the sample into theinstrument and initiate the test.11.4 Record results reported by the awinstrument.12. Results12.1 Results will be reported in awunits between 0.00 and1.00 to two decima
39、l places.13. Special Considerations13.1 Plant material used in this test should be disposed of inaccordance with regulations set out by authorities havingjurisdiction.14. Keywords14.1 aw; cannabis; cannabis flower; moisture; water activity;water contentREFERENCES(1) “Fungus in Medical Marijuana Eyed
40、 as Possible Cause in CaliforniaMans Death,” http:/ (accessed 2017/09/03).(2) Chirife, J. and Fontana, A. J. (2007) Introduction: Historical High-lights of Water Activity Research, in Water Activity in Foods:Fundamentals and Applications (eds G. V. Barbosa-Cnovas, A. J.Fontana, S. J. Schmidt and T.
41、P. Labuza), Blackwell Publishing Ltd,Oxford, UK. doi: 10.1002/9780470376454.ch1(3) Holmes, M., Vyas, J. M., Steinbach, W., and McPartland, J., andreferences therein, “Microbiological Safety Testing of Cannabis,”Cannabis Safety Institute, May 2015.(4) Ledward, D.A., “Water activity: Theory and applic
42、ations to food (IFTBasic Symposium 85 Series),” Louis B. Rockland and Larry R.Beuchat, Eds., Meat Sci., Vol 21, 1987, pp. 157-86 158.(5) Scott, W.J., Water relations of Staphylococcus aureus at 30. Austra-lian Journal of Biological Sciences6, 1953, pp 549-564.(6) Troller, J. A., “Trends in research
43、related to the influence of “wateractivity” on microorganisms in food,” Adv. Exp. Med. Biol., Vol 302,1991, pp. 305-313.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are express
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