scientific measurement?

Question

I know this is probably going to be a very vague question, but i barely undestand it myself. I need to know how scientists measure the amount of carbs, proteins, etc. on the back of food labels. Please and thank you!

Answer 1

I don't know how they ANALYZE them, but when they're creating the labels, it's as simple as knowing what's going into the product and saying it based on the amount of product in the can, box, shrinkwrap..

IE:
A pound of cookies contains1 cup of cugar, 1 cup of chocolate chips 3 eggs, 2 cups of flour, a tablespoon of salt, etc..
The scienist (nutritionist?) knows the sugar has 150 grams of carbs, and the chocolate has 50, the flour has 150, the eggs have 2. The eggs have 40 grams of protein, the flour has 10, the chocolate has 2. The eggs have 20 grams of fat, the butter has 150, the chocolate has 20.
The total:
carb 350
fat - 190
protein - 52
This is per pound of cookies.
Ifthe serving size is 1/2 pound
you'd have
175 grams of carbs
95 - fat
26 protein

These numbers are totally made up, but I believe that's the process...

Answer 2

They use a variety of measurements, ranging from the physical amounts of various elements in the food to the amount of energy that will be produced by the food (calories).
They use another measure as well, and that is what percentage of the listed item is, compared to your daily requirements. For example, a tin of condensed soup willl provide something like 35% of your daily requirement of salt. 70% if you eat the whole tin by yourself.
It really is very complicated and you have to pay close attention. I've been looking at salt content on labels recently and it is absolutely horrifying. I was happy to see that the baking powder i put in my waffels and pancakes only contained 2% of my daily salt requirement. Then I looked more closely, and it said that 1/8 of a teaspoon contained 2%, which means 1 teaspoon contains 16% and the 2 teaspoons called for in the recipe added up to a whopping 32% of my daily requirement for salt.
If you add up what you eat during the day, it comes to about 150-175% of what you require, and that's without ever adding salt while you cook or adding it to your food at the table.
Sorry for the rant. To get back to your question, is is very difficult to give a precise answer because they use so many different kinds of measurements. I think the bottom line is they are complying with government regulations, but not in a way that the average person can understand.

Answer 3

These items are determined by chemical analysis. There are many methods used: chemical reactions, mass spectrometry, etc. Basic constituents are analyzed, but combinations of ingredients are just the sum of their constituents.

You can get information on the methods from the USDA; start here, and explore the site: http://www.nal.usda.gov/fnic/foodcomp/search/