Nutrition info for food. How?

So I’m eating and check the nutrition label of the mixed nuts. I see Manganese, phosphorus, etc listed.

How do “they” determine the amounts of vitamins and minerals in a serving? I know calories are based on burning food for energy released (clarify that one if you want).

Do they actually break foods down by molecules and determine vitamin amounts, or is it some sort of guesswork?

Please enlighten me.

Good question… bump

I always just assumed they added the nutritional information for each of the food’s components (of course scaling everything in the right proportions for that food’s ingredients) and came up with that total. Am I wrong?

IANA Food Chemist (I worked in pharmaceuticals for a few years), but there is some overlap in the spirit, if not the practice of product testing.

In some cases the ingredients are known; food is prepared according to a set recipe, and so you know how much salt, for example, got put into something. The raw material (the bulk salt) was likely tested chemically as being 99% pure or whatever standard is necessary for food consumption. Likewise, bacterial levels for raw materials are typically laboratory tested, for safety reasons. By knowing that your salt has 1% KCl (totally making this up, btw!), and you put 10kg of salt into the mix that has a total ingredient weight of 2045kg, and the final product weighs 200g each… well, you can determine the amount of K+ (potassium) in the final product!

There are also (probably) chemical tests which will isolate and quantitate other ingredients, and a set number of samples from a given production batch or food item is tested and averaged to give the nutritional content. Calorie content is based on bomb calorimetry.

As I said, I don’t know of specific tests, since it wasn’t ever my field, but there are specialty labs which can do this testing for you. Bodycote is one that I know does this type of work - you can likely google many more.

Manganese and phosphorus are both elements, so they’d be very straightforward to measure. Take a sample of the food, vaporize it, and run it through a mass spectrometer, and you can find exactly how much of each element is in it.

Complicated molecules like vitamins would be more difficult, though… I don’t know how they do those. Probably some clever chemist has come up with a substance which changes color when exposed to a certain concentration of Vitamin C, or whatever, and you dilute the food until it’s just enough to change color.

I have only tested vitamins in medicinal form (injectable), but there are HPLC assays developed for vitamins. Extraction of the vitamins from foods is, I think, relatively well known and developed at this point.

This might be a good reference: http://books.google.ca/books?id=mcwdkygB0FQC&pg=PA321&lpg=PA321&dq=vitamin+extraction+from+food&source=web&ots=3lxumO5f7o&sig=2epHXCUQ_uoyhz_s3ZfqQd-G7fY&hl=en&sa=X&oi=book_result&resnum=3&ct=result

I do recall that most of the assays are pretty easy other than the fact that many pure vitamins (E, K, A palmitate for sure) are very viscous yellowish liquids at room temperature, making them pretty much impossible to pipette, and hard to weigh in order to get a good set of standards made! Oh, and cyano- and hydroxo- cobalamin (common Vit B-12 forms) are blood red when in solution.