How do food producers measure the exact amount of carbs, proteins, vitamins etc. in a piece of food?
In: Biology
We run biochemical assays that tell us exact amount of each nutrient or it’s metabolites that gives the nutrition information
Food producers don’t usually measure exact amounts, but rather go by references for foods or ingredients provided by suppliers or labs. I think the lab part is pretty interesting, and here is what I know about that:
If you burn the food and measure the energy it puts out, you know the calorie content.
Labs measure fat of a food by first extracting the fat with a solvent and measuring it. We know that fats contain about 9 calories per gram.
Protein can measured by how much nitrogen is in a food. The amount of nitrogen found in protein is generally similar enough among all proteins to make this estimation. We know that protein contains about 4 calories per gram.
Since a food’s total caloric intake is fat calories + protein calories + carb calories, we can take the total energy it puts out by burning, subtract extracted fat * 9, and subtract protein estimated * 4 to get the calories provided as carbohydrates.
If you incinerate the food to ash, you can measure minerals like iron and zinc much easier. To be honest, I don’t know much more than that when it comes to micro nutrient measurements.
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.
Carbs is done by burning said fuel to heat a certain amount of water. There is a chemistry equation that takes change in temperature divided by amount of water plus some other Hocus Pocus to derive cal content of said item that was burnt.
[removed]
I work in a lab that does this analysis. Basically the manufacturers send us their food products and we carry out the testing based on the nutrition facts they want. The lab uses different analysers for different components, including the amount of vitamins.
On a unprocessed beef sample.. if you run moisture, fat, protein and Ash it will add up to 100%. I can tell you that.
Moisture is easy. Weigh a sample put it in the oven for 4 hrs at 125C when it cools off weigh it back.
Ash weigh a crucible.. weigh in a sample.. ash at 550C until it’s ashed .. weigh it back
Fat.. weigh a sample then dry it. Weigh a flask Then using an extractor using petroleum ether to extract the fat into the flask for 4 hrs. Then dry off the ether. And weigh the flask to determine how much fat is extracted
Protein.. weigh a sample into a kjeldahl flask. Add in a catalyst and sulphuric acid and digest for 2hrs. When done add water and add sodium hydroxide to neutralize the acid and distill into a .2N acid flask. Then titrate with .2N base till the endpoint. Then you calculate the titration. Then calculate the amount of nitrogen in the sample. From that you can calculate the amount of protein.
The other things you asked about also have laboratory tests to determine.
There are standard methods. Most things have a method making organization. AOAC ( Association of Official Analytical Chemists) is a large one that encompasses this stuff. Pretty much anything bought and sold has a standards organization. This makes sure that everyone is on the same level. So when you buy x you get x.
Food scientist here. There are different tests for every type of component in food. For instance, protein is typically measured using the Kjeldahl or Dumas method, which does measure the nitrogen in food then uses a conversion factor to get from nitrogen to protein. Typically, the only nitrogen in food is from amino acids, which are the building blocks of protein. Proteins, water, ash (vitamins and minerals), and lipids (oils and fats) are measured in food. Then, you take 100 – the sum of those to get the % that is carbs. There is no simple way to measure the entirety of carbohydrates because they are so complex (sugars, starches, fibers, etc).
All in all, food is typically very complex and heterogeneous, so it is difficult to analyze. There are many tests that you have to do to fully analyze food. But I remember in my food analysis class in grad school, for our final project we got an unknown amount of food and had to analyze it over the course of two weeks to create an accurate nutrition label for it. Fun stuff.
Edit: reading the comments, nobody has any idea how to analyze food
[removed]
[removed]
Latest Answers