Reference
Glossary of drying terms
Fifty-plus definitions used across this knowledge base — from the physics of water activity and moisture content to the practical vocabulary of curing, conditioning and shelf life. Search it, or jump by letter.
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The three terms worth learning first
Water activity (aw) — how available the water is, from 0 to 1. The single best predictor of whether dried food is safe and stable. Moisture content — how much water is present, expressed on a wet or dry basis. Conditioning — resting a dried batch in a sealed container so moisture equalises before packaging. Get these three and most of the rest of the vocabulary falls into place.
| Term | Stands for | What it means in practice |
|---|---|---|
| aw | Water activity | Available water, 0–1. Below 0.60 nothing grows; it is the target, not the moisture percentage |
| MC | Moisture content | How much water is present, as a share of either the wet weight (wb) or the dry matter (db) |
| EMC | Equilibrium moisture content | The moisture a food settles at for a given air humidity and temperature — where drying stops by itself |
| RH / ERH | Relative humidity / equilibrium relative humidity | Air humidity as a percentage; ERH ÷ 100 is a cheap approximation of aw in a sealed jar |
| WVTR | Water vapour transmission rate | g of water per m² of film per day at 38 °C and 90ߙ% RH — the number that decides crisp shelf life |
| OTR | Oxygen transmission rate | cm³ of oxygen per m² per day; drives rancidity, browning and vitamin loss |
| IMF | Intermediate-moisture food | aw 0.60–0.85: shelf-stable only with hurdles such as acid, salt, sugar or refrigeration |
| MPR | Moisture : protein ratio | The USDA stability measure for jerky: at or below 0.75 : 1 |
| GAB | Guggenheim–Anderson–de Boer | The three-parameter model that fits a sorption isotherm and predicts aw from moisture |
| D / z value | Decimal reduction time / z-value | Minutes to kill 90ߙ% of an organism at a given temperature; the z-value is the temperature change that changes D tenfold |
| Q10 | Temperature coefficient | How much a reaction speeds up per 10 °C — typically 2–3, which is what makes accelerated shelf-life tests possible |
| HACCP / CCP | Hazard analysis and critical control points | A food-safety system, and the specific steps in your process that must be measured and recorded |
| Brix | Degrees Brix | Sucrose percentage by mass — used for syrups, brines and osmotic pretreatments |
| ppm | Parts per million | Milligrams per kilogram. Sulfite labelling thresholds and residual limits are written this way |