How does it work with finding out the nutritional facts in food?

Question

i dont get how they know an egg has 80cals or w/e it has and 6g fat 6g protein or how whole milk has 8g fat and 8g protein and 12g carbs and w/e the cals are how do they actually know this...what do they do to find this out.

Answer 1

This is all done in a lab.

Calories:

This is a measure using a technique known as calorimetry.  This is the measure of heat energy given off by the food during combustion and is measured with a calorimeter.  A calorie is defined as the amount of heat it takes to increase 1 gram of water by 1°C.  When calorie is used with food, it is actually kilocalorie or Calorie (big c), which is the amount of heat it takes to increase 1 kg of water by 1°C.

Determination of proteins, carbs, and fats:

There are two ways that this can be done...

1.  The FDA requires that food manufactures place the ingredients AND the composition on the packaging.  As the manufacturers know what they are placing into a certain product, they know how many total grams of each constituent go into the package.  Divide that by the number of servings and you have the count.

2.  In the case of the example that you cave above, such as an egg or other naturally occurring food that is not a "pure" constituent, there will be a combination of two methods used.

--  Qualitative analysis:  This will tell what constituents are in the sample

--  Quantitative analysis:  This will tell how much of each of the found constituents are in the sample.

There are many different test that can be run to determine these as effectively you have to separate/ destroy everything except what you are hoping to find.  The test methods generically include but are not limited to the means of; heat, cold, acids, bases, hydrolysis, combustion, etc...

Good luck!!