How do food producers measure the exact amount of carbs, proteins, vitamins etc. in a piece of food?
In: Biology
There is so much misinformation in this thread. I worked for a food testing laboratory for over four years and yes companies actually did order nutrition label panels. Look up companies like [Eurofins](https://www.eurofins.com/food-and-feed-testing/) if you want to see what tests are available.
First when I sample is received it is ground up (homogenized) into a paste or slurry. Samples are taken from this so that each of them is representative of the product and you don’t end up with results that don’t make sense.
Protein: Protein was done by Kjeldahl nitrogen. Weigh sample and digest with sulfuric acid at ~400°C. Amino acids are nitrogen containing compounds and during the digestion all of the amino acids get converted into ammonia (a base). This is titrated with an acid. How much acid the ammonia takes to neutralize is proportional to the amount of nitrogen, which is proportional to the amount of protein. Use a conversion factor to get the amount of protein.
Fat: Boil sample in HCl and filter it. Fat will get caught in the filter, while things sugars will go through. Extract fat out of the filter with a [Soxhlet extractor](https://en.wikipedia.org/wiki/Soxhlet_extractor). Solvent will dissolve the fat and deposit it in a beaker. (wt. beaker with fat – wt. beaker without fat) / initial weight of sample = % fat.
Sugars: I didn’t work on this one too much, so I don’t remember the extraction process too well. But I do know that once you extracted the sugars from your sample they were analyzed with an [HPLC](https://en.wikipedia.org/wiki/High-performance_liquid_chromatography). The instrument separates the sugars and produces a [chromatogram](https://www.sigmaaldrich.com/technical-documents/articles/analytical-applications/hplc/hplc-analysis-of-sugars-g005747.html). The order of the sugars is always the same so you can identify by their order. In this example for the setup they have glucose will always come off the instrument after 4mins so if there isn’t a peak there then you know there is no glucose in the sample. The area under the peak is proportional to the amount of glucose in the sample.
Vitamins: Vitamins are extracted differently depending on if they are fat soluble (vitamin D, vitamin E, etc) or water soluble (vitamin C, Vitamin B). But once extracted they are run through an HPLC much like the sugars.
Minerals (sodium, potassium, calcium, etc). The sample is digested in nitric acid with a microwave digestor. The sample is then analyzed by an [ICP-OES](https://en.wikipedia.org/wiki/Inductively_coupled_plasma_atomic_emission_spectroscopy). The sample after digestion gets nebulized and sent through an argon plasma that is ~10000°F. This breaks the sample down to its elemental components. When this happens the elements emit different wavelengths of light. A detector reads these emissions. The specific wavelength identifies the element and the intensity of the emission is equivalent to the concentration of that element.
Calories: We did *not* use a bomb calorimeter. 1 gram of fat has 9 calories. 1 gram of sugar or protein has 4 calories. Take the amount of sugar, protein and fat measured and multiply it by these factors to get the caloric content of the food.
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