Obviously there’s scientifical instruments to get precise measures but at home we combine measurement with observation. Your basic “dried fruit” at around 20% moisture content is still flexible. Down around dehydration levels, 3%, it’s brittle and snappy (apple chips! Yum!). Dried fruit has, for lack of better description, a desiccated look to it. Properly sundried peppers should make a “tap” sound when bounced off a surface. Beef Jerky at around 12% is still flexible. Weighing food is a good method of calculating how much H2O is gone if you have a scale because we calculate H2O content in food by weight rather than volume but when you have several tons of food, this can be a heck of a chore.
For grains and stuff like dried beans, moisture content becomes pretty crucial. Experience is the old mountain method, but there’s a bit of hedging of bets going on. With drying of seed grains, moisture content massively effects their viability so we’d pull seeds from drying in batches, marking how long each batch had dried on the paper envelopes we kept them in and from what dates so we kind of had a bracket. At least some of the seeds were reasonably sure to be just about perfect. Oddly, preserving seeds, which are food for a germinating young plant, is pretty much like preserving our own food even though in much of this discussion, seeds are our food. Moisture, heat, sunlight are our mutual enemies as far as long term seed storage or even preservation until next season.
However, with weight we can do a decent job of determining moisture content in our food as it’s drying, and we can extrapolate by comparing it to the rest of our stocks by observation of color, texture, smell and flavor. And we can continue to “bracket” our drying to further insure our protection.
To roughly determine moisture content of your drying foods, we can use the following method.
- Weigh a portion of the food before drying.
- Immediately start drying this portion to whatever point you think is good.
- Weight it again.
- Subtract the dry weight from the wet weight, divide this by dry weight and multiply the result by 100.
- This will be the moisture content in %.
- So the percentage of water in a food is ((wet-dry)/wet)*100.
- From here you can use your senses to determine your rough moisture content by comparing color, texture and weight for
the rest of this type of food for that drying session.
- Be aware your drying times will vary from day to day (or day to night) depending on humidity.
Scales for determining moisture content of long term food stores and commerce.
It becomes pretty obvious that some things like grain grinders or mills come in handy for long term storage foods. Scales are really handy too. Keep your eyes peeled for old, still functional scales. Obviously the big ones we want are getting hard to find. Smaller scales force us to weigh a single shipment or harvest multiple times leading to increased inaccuracy. Take care to clean, lubricate and calibrate your scales or you’ll be running around in circles. For commerce, barter and packaging we also have to be accurate. For measuring H2O content we have to be really accurate. Postal scales were designed to be accurate to within 1 gram and should be calibratable. These come in many different sizes.