Harvest & Post-Harvest
Representative Water-Activity Sampling
Water-activity measurements are only as useful as the sample plan. Uneven drying, flower size, canopy position, package location, temperature, and equilibration can make one reading unrepresentative of an entire lot.
Key concepts
- Water activity measures available water rather than total moisture mass
- A heterogeneous lot requires a representative sampling plan
- Instrument calibration and sample temperature influence data quality
- Acceptance criteria should follow the relevant jurisdiction, standard, or product specification
What to measure or observe
- Define how many samples and where they come from
- Use a calibrated meter and documented procedure
- Allow the sample to equilibrate according to the instrument method
- Record lot, package, sample, time, temperature, and meter identity
Common mistakes
- Testing only the driest-looking flower
- Using one reading for a large uneven lot
- Comparing measurements taken with different procedures without noting the difference
- Applying a universal acceptance number without checking the governing standard
Visuals this lesson still needs
- Representative lot-sampling map
- Water activity versus moisture-content diagram
- Meter workflow
- Sampling-bias comparison