Apr 20 2013

Processing and preparing food for long term storage.

Drying foods for long term storage.

Drying is one of the oldest methods of preservation. In drying, we’re making life more difficult for the micronasties by removing water from their park. And for a very long time, humans have relied heavily upon the drying power of the sun which was widely recognized as having a monopoly on the heating industry. Sun-drying works on a wide rage of things: meat, fish, fruit, grains, vegetables and insects. Indeed, every insect I have ever eaten either did or would have tasted better for sun drying. Or maybe it’s a textural thing. I prefer “crunch” as opposed to “squirt”. Drying goes by a lot of fancier names these days like dehydration and desiccation but the basic methods and utilities are still available. Spread food out on a rock in the sun and wait.

Something to remember! normal food when harvested is between like 90% for fruits and down to like 20% for lean meats. “Drying” is thus a pretty gross term and it means any less moisture content than present when the food was harvested. For practical purposes, dried fruit is somewhere around 15-20% moisture content but it only gets harder then crunchier the lower you go. In desert environments we can get things pretty dry, almost to the level we know call dehydration which is around 3% for fruits and vegetables.

Did you get that last point? Mostly we can only conventionally dry things as dry as the air in which we are drying it. Using a heat source, we can dehumidify an area around our drying food, but let it sit out in the air and it will start re-absorbing moisture. You folks in damper regions know this when your bag of potato chips is stale one day after opening. If you are drying to below-ambient humidity levels, you have to package the food fast just like they seal up your potato chip bag at the processing plant.

Drying meats is kinda different because a lot of moisture is contained in lipidic state, in fats in the meat. It’s possible to totally dessicate meat, it can be dehydrated but it’s generally not all that nice to eat. Meat is totally not supposed to go “crunch”. But for practical purposes, simple drying down to around 7% delivers a longer lasting food source in the field. The new techniques such as commercial dehydration and freeze-drying take this a big step forward.

Moisture content of “raw” foods.

Let’s just think in terms of basics and not list off 100 foods. Water is 100% moisture content (duh, I know) and it’s where our table starts. It ends with freeze dried food under 3%.

Foods Moisture
Water 100%
Cantaloupe, cauliflower, celery, most lettuce 90%
Apples, cherries, potatoes, grapes, apricots 80%
Beef, chicken, fish, bananas, sweet potatoes, ginger 70%
Grains 20%
Honey 15%
Some nuts 10% and lower
Dehydrated and freeze dried foods 3%

So we see most of the fresh foods we eat are in that 70-90% moisture content range. I suppose from the table above, nature is telling us it’s long term storage foods are honey, nuts and grains which is no secret to bees and squirrels and the myriad grain-eating creatures that store up for winter.