Calculating food Carb %

Has anyone seen this calculator?

http://www.scheyderweb.com/cats/catfood.html

Is it any good?

 

I was thinking that since it uses the min values from the can, that it would yield a "Max" carb %. Not the actual carb %.

Might be useful for companies that absolutely refuse to give real numbers.

I was also thinking, I could look at the javascript "guts" of it and rewrite a different version that would be more useful to people here. I could see people getting % of carbs confused with % of calories from carbs.

 

Here is the "formula"

When we talk about "less than 10% carbs" we are reffering to the fact that the food has say 8% of it's calories from carbohydrates. The actual carbohydrate amount (scientifically Nitrogen free extract=NfE) in the orginal or dry substance is calculated as follows using as fed values (not the Minimum and maximim given on most labels)

Subtract the as fed values of protien, fat, ash, fiber, and moisure from 100%

100% - crude protien% - crude fat% - ash% - crude fiber% - moisture% = NfE (carbohydrate)%

example canned food: 100% - 10% - 5,5% - 2,5% - 1,0% - 79% = 2% NfE
example dry food: 100% - 30% - 10% - 6,5% - 2,5% - 9% = 42% NfE



To calculate the carbohydrate content in the dry substance



canned food: 100% - 79% moisture = 21% dry matter (DM) = 0,21
dry food: 100% - 9% moisture = 91% dry matter (DM) = 0,91


Then divide the carbohydrate procent by the DM

canned food: 2% NfE / 0,21 = 9,52% carbs in the dry substance
dry food: 42% NfE / 0,91 = 46,15% carbs in the dry substance


To calculate calories each component has a differnt calorie value (depending on digestability typically the modified Atwater-Factor is used:
Protein: 3,5 kcal/g, Fat: 8,5 kcal/g, NfE (carbohydrates): 3,5 kcal/g

The Energy in kcal / 100 g Food is calculated as follows:

(%Protein * 3,5 kcal/g) + (%Fat * 8,5 kcal/g) + (%NfE * 3,5 kcal/g)