dehydrating and calorie counting

[Jeff M.]

I've just recently started dehydrating food. I haven't yet used any of the food backpacking. How do I determine the amount of calories the food has once I start planning meals for trips? For example, if I make homemade spaghetti, fruit leather/dried fruit, or jerky (all of which I plan on making).

[Sarah Kirkconnell]

Lets say you make a big pot of spaghetti and you divide it into 4 servings. Add up everything you put into it and then divide. Ta-da! (Consider that for hiking 16 ounces of pasta, sauce, veggies and maybe meat only makes 4 servings. If even that. Some men would eat half the pot!)

Fruit leather? Look up online calories for the fruit or berries used and weigh or measure that, then add in any sugar, etc. Once you get done note how much is a serving and so on.

Jerky is pretty easy – run the calories for weight. Say you dry 2 lbs raw – note how many pieces you get and what an average piece weighs raw. Then when you get done you know how much concentrated meat is in that dry piece. Jerky is low in calories but high in protein – something to think about.

If you look online you can find charts that list the stats for raw foods, either by weight or by measurement, this way you know how many calories in a cup of mushrooms or rice or etc, etc. Diet sites often have them.

[Bob Gross]

Dehydration should theoretically have no effect on calories. If you started with 1000 calories of any wet food, then dehydrate it, all you have lost is the water, so you still have 1000 calories of dry food left. Then once you rehydrate it on the trail, you still have 1000 calories of wet food.

–B.G.–

[Ben Crowell]

Although it is certainly possible to add up all the calories of the ingredients, that can be kind of a pain.

Within a given category of food, energy density doesn't really vary all that much. Here are some sample values for non-cooked food, expressed both as energy per unit mass and energy per unit volume:

calories per gram:

jerky = 2.5
dried fruit = 3
granola = 3
cheese = 4
salami = 4
pesto = 4.4
peanut-granola bar = 4.5
gol popdi = 5.3
nuts = 5.5
cookies = 6
olive oil = 9

calories per milliliter:

granola = 1.5
dried fruit = 2.5
nuts = 3
cheese = 3.5
peanut-granola bar = 3.5
olive oil = 8.5

Once you get a general idea of the energy density of food in a particular category, you can pretty much guess that other foods in the same category will be about the same. For instance, pretty much any cooking oil has the same energy density as olive oil. For fruit leather and jerky, the values above should work. If you like jerky as a luxury food, that's cool, but its energy density is pathetic; hard salami is much more dense. For pasta, I think you could just use the figures from a commercial product, and you'd probably be bang-on. For higher energy density, you might want to consider pasta with pesto rather than pasta with red sauce.

[D G]

Carbohydrates and Protein are 4 calories/gram (113 calories/oz)

Fats are 9 calories/gram (255 calories/oz)

Fats don't dehydrate really well so when you dehydrate food you'll be trying to dry stuff that is mostly lean. Also, you generally won't be removing 100% of the water.

Using a figure of 100 calories/oz for dehydrated food will usually give you a pretty good rough estimate.

I like to take olive oil or butter separately to add to meals for fat calories.

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