ASTM D7819-12(2021)

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.
Designation: D7819 − 12 (Reapproved 2021)
Standard Test Method for
Enumeration of Yeast and Mold on Fresh (Uncured) Hides
and Skins
This standard is issued under the fixed designation D7819; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Significance and Use
1.1 This test method covers the enumeration of yeast and 4.1 This test method enumerates yeast and mold. Yeast and
mold on fresh (uncured) hides and skins. This test method is mold have been known to cause damage to hides and skins.
applicable to uncured hides and skins.
5. Apparatus
1.2 The values stated in SI units are to be regarded as
5.1 Incubator, 20–25 °C.
standard. No other units of measurement are included in this
standard.
5.2 Colony counter (not mandatory, but highly recom-
mended).
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
5.3 Sterile pipets.
responsibility of the user of this standard to establish appro-
5.4 Stomacher, for mixing initial dilution. (If stomacher is
priate safety, health, and environmental practices and deter-
unavailable, hand-mix.)
mine the applicability of regulatory limitations prior to use.
5.5 Balance.
1.4 This international standard was developed in accor-
dance with internationally recognized principles on standard-
5.6 Sterile petri dishes.
ization established in the Decision on Principles for the
5.7 Autoclave (sterilizer). (Check the effectiveness of ster-
Development of International Standards, Guides and Recom-
ilizationweekly.Forexample,placesporesuspensionsorstrips
mendations issued by the World Trade Organization Technical
of Bacillus stearothermophilus(commerciallyavailable)inside
Barriers to Trade (TBT) Committee.
glassware for a full autoclave cycle. Follow manufacturer’s
directions for sterilization of specific media.)
2. Referenced Documents
5.8 pH meter.
2.1 ASTM Standards:
D6715Practice for Sampling and Preparation of Fresh or
5.9 Waterbath, 45 6 1 °C.
Salt-Preserved (Cured) Hides and Skins for Chemical and
5.10 Stomacher bags, or sterile, sealable quart plastic bag
Physical Tests
(for example, food storage type, sterile bag).
E691Practice for Conducting an Interlaboratory Study to
5.11 Cutting tool, sterile (for example, scalpel blade and
Determine the Precision of a Test Method
forcep, as needed for cutting cured hides and skins).
E177Practice for Use of the Terms Precision and Bias in
ASTM Test Methods
5.12 Vortex mixer, for mixing dilution tubes (optional).
5.13 Autoclave thermometer, or equivalent for monitoring
3. Summary of Test Method
autoclave temperature.
3.1 Samples of uncured hides and skins are serially diluted
andplatedonagarcontaininganantibioticsolution.Theplates
6. Reagents and Materials
are incubated at 20–25 °C for 5 days.
6.1 Butterfield’s Phosphate Stock Solution: Dissolve 34 g
KH PO (Potassium Phosphate monobasic) in 500 mL DI
2 4
ThistestmethodisunderthejurisdictionofASTMCommitteeD31onLeather
water.Adjust the pH to 7.2 6 0.1 with 1N – 6N NaOH. Bring
and is the direct responsibility of Subcommittee D31.02 on Wet Blue.
volume to 1 L with DI water. Sterilize for 15 min at 121 °C.
Current edition approved Sept. 1, 2021. Published October 2021. Originally
NOTE 1—Typical autoclave setting is 120–124 °C at 15 psi. (See 5.7.)
approved in 2012. Last previous edition approved in 2016 as D7819–12 (2016).
DOI: 10.1520/D7819-12R21.
6.2 Butterfield’s Phosphate Diluent (BPD):Take1.25mLof
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Butterfield’s Phosphate Stock solution (6.1) and bring to 1 L
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
with DI water. Dispense into 1-litre bottles and 9-mL dilution
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. tubes. Sterilize for 15 min at 121 °C. (See Note 1.)
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7819 − 12 (2021)
6.3 Potato Dextrose Agar (PDA). 9.2 Suspend 39 g of Potato Dextrose Agar in 1 litre of
3 deionized or distilled water and heat to boiling to dissolve
6.4 Antibiotic solution (Chloramphenicol) – (needed to
completely.
inhibit bacterial growth on agar).
9.3 Add 10 mL of chloramphenicol stock solution per litre
6.5 Distilled or deionized water.
of agar to give a concentration of 100 ppm. Sterilize in the
6.6 NaOH, 1N – 6N.
autoclave for 15 min at 121 °C. (See Note 1.) Cool to 45 6 1
6.7 Bacillus stearothermophilus spore suspensions or strips
°C in a waterbath. Once medium has been tempered, it can be
(commercially available), or equivalent.
held for 2–3 h before use, provided the water level in the
waterbath is 2–3 cm above the surface of the agar. Final pH
7. Hazards
of the agar: 5.6 6 0.2.
7.1 Allreagentsandchemicalsshouldbehandledwithcare.
10. Procedure
Before using any chemical, read and follow all safety precau-
tions and instructions on the manufacturer’s label or MSDS
10.1 Using a sterile scalpel, aseptically obtain a 20 6 0.1 g
(Material Safety Data Sheet).
specimen that includes both the flesh side and the hair side.
Weighitintoasterilebag.Add180gofBPD(6.2)diluentinto
8. Sampling
thesamesterilebag.Stomachorhand-massagefor1min.This
8.1 The specimen shall be sampled in accordance with
provides a 1:10 dilution.
Practice D6715, and placed in sterile containers.
-2 -3 -4
10.2 Preparethefollowingsampledilutions:10 ,10 ,10 ,
-5 -6 -7
10 ,10 , and 10 (see Fig. 1).
9. Preparation of Potato Dextrose Agar and Antibiotic
-2 -1
Example:Toobtaina10 dilution,mixthe10 dilutionand
Solution
-1
pipet 1 mL of that 10 dilution into a 9-mL dilution tube.
9.1 Prepare the antibiotic stock (10 000 ppm) solution by
NOTE 2—When transferring the aliquots between the tubes, the analyst
dissolving1gof chloramphenicol in 100 mLsterile deionized
must use a different pipet or pipet tip for each transfer.
or distilled water. Store this stock solution in a dark location at
10.3 Pipet 1 mL of each dilution into the appropriate,
≤5 °C for up to two months.
separate petri dishes.
10.4 Pour prepared agar (9.3) that has been previously
tempered to 45 6 1 °C into the dish.
The sole source of supply known to the committee at this time is Sigma-
NOTE 3—Add agar within 1–2 min after adding dilution to avoid
Aldrich, Cat. # C0378 (25 g). If you are aware of alternative suppliers, please
adherence of sample to bottom of dish. Do not pour agar directly on the
provide this information toASTM International Headquarters.Your comments will
sample. Replace the cover.
receive careful consideration at a meeting of the responsible technical committee,
which you may attend.
FIG. 1 Plating
D7819 − 12 (2021)
NOTE 9—When requested, the counts for yeast and mold may be
10.5 Swirltheplategentlyinafigure-eightmotiontoevenly
combined as one count, and reported as
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