Sciencemadness Discussion Board

Chemical purity grade food

jenijjun - 2-8-2021 at 00:09

What would be appropriate chem grade for use in food preparation? I have some p.a. for analysis 99% solvents.

Oxy - 2-8-2021 at 00:33

Purity for food is much higher than "for analysis". Food grade chemicals must be prepared with a different standards and can't be contaminated with toxic, mutagenic or harmful in general materials. It also means that the process of transferring and packaging must be safe and can't contaminate the product. Also packaging must be chemically safe.

Don't know where do you live but I suspect that if you would use chemically grade chemicals for food preparation in EU you could end in prison.

Sulaiman - 2-8-2021 at 01:28

Quote: Originally posted by Oxy  
Purity for food is much higher than "for analysis".

I disagree;

I buy many of my chemicals as 'food grade'
it does not mean 'pure',
it means 'safe for human consumption'
Many food grade chemicals are far from pure.

Analytical grade implies high purity and a knowledge of what impurities are present in what quantities.

If you are using chemicals for human consumption then it is best to use 'food grade'

Both 'food' and 'analytical' grades may contain preservatives and/or stabilisers.

karlosĀ³ - 2-8-2021 at 01:52

Quote: Originally posted by jenijjun  
What would be appropriate chem grade for use in food preparation? I have some p.a. for analysis 99% solvents.

Food grade, as the name says :D

I just had a look at one supplier, and interestingly, the purity is of different importance, as to what is and what isn't food grade, I think it depends on the nature of the other impurities.
Because there are some 98% pure substances designated as food grade(eg potassium gluconate) and other food grade substances are given at 99,9% purity.
Definitely not analytical grade.

Don't we have a food chemist among us, as to what makes a chemical qualify for food grade?
Percentual purity obviously isn't the marker for it.

unionised - 2-8-2021 at 02:19

I know a guy who worked in a sugar factory. He's quite proud of the fact that the sugar they sold by the lorry-load for food use in 2 pound bags exceeded the specifications for analytical reagent grade sucrose.

But the criteria for lab and food use are different.
I don't greatly care about bacterial counts in analytical chemicals, but I need to know their degree of hydration.
If I'm adding a teaspoon of citric acid to my homebrew, the priorities are reversed.

Food grade sodium chloride has impurities added deliberately.

Fyndium - 2-8-2021 at 03:13

The main difference would be that analytical grade stuff must be pure enough from any contamination, food grade stuff must be free of toxic stuff, but it can contain significant amounts of potable impurities. So food grade stuff can be chemically impure, but analytical grade chemical can be unsuitable for consumption.

You could do anhydrous ethanol with benzene azeotropic distillation, but it would be unsuitable for any sort of consumption. Azeotropic food grade ethanol must be prepared using stuff that itself is not harmful to health.

Another example if phosphoric acid used in food. It is made by distilling elemental phosphorus and then reacting it to eventually form pure phosphoric acid. Techical grade phosphoric acid can be made by simpler means, for example reacting phosphates with sulfuric acid.

Reactions that do not involve toxic reagents can be used both food and chemical industry. Also, there are some reactions that toxic stuff is inherently needed, but can be eliminated to sub-threshold by a certain purification processes.

Herr Haber - 2-8-2021 at 06:20

Quote: Originally posted by karlosĀ³  

Percentual purity obviously isn't the marker for it.

The best example I can think of being Stevia (which is 91% Erythritol)

The above comment about the stabilizer is also true. I've never seen hydrogen peroxide without BHT.

@Unionised: Iodine. You certainly know the reasons why. Taking action took almost a century, the investigation itself took much less though. Very interesting story.

happyfooddance - 2-8-2021 at 14:21

The standards that govern food quality differ from region to region and from product to product. In general, natural (biological) origin, free from hazardous compounds and heavy metals, and a completely traceable origins are what make a product "food grade."

Some food grade chemicals are more pure than their lab counterparts, some are less so.

Some (like KOH and NaOH) are often identical, made and packed at the same plant.

rockyit98 - 2-8-2021 at 17:42

do you mean " food grade purity Chemicals" ?

macckone - 3-8-2021 at 06:42

In the US, USP and ACS reagent grade are usually but not always identical.
USP grade can contain more impurities provided they aren't harmful.
While ACS grade can contain impurities that are harmful but won't impact reactions or analysis

For the vast majority under the ACS reagent chemicals 11th edition, will be equal to or more pure than USP grade.
ACS and USP work together on the standards which is why there isn't a lot of difference.

BP and EP are also mostly the same.

maldi-tof - 16-8-2021 at 22:47

It has to do not only with the "purity" (assay), but for the possible impurities.
For example, many products in the FCC (food chemical codex) and EU 231/2012 have arsenic, lead, cadmium and mercury specifications in their monography. Almost always, below 0.0001% (1 ppm).
In the EP/USP, usually, there is no limit for these elements in the monograph because there is a specific ICH guideline (ICH Q3D Elemental impurities) that covers it (mainly for the risk analysis of the final drug substance).
As said before, certificates for food grade products cover not only the production, but also the packaging, for example, having a metal detector in the final step to make sure that there are not any screws, blades, scissors...

macckone - 20-8-2021 at 08:40


ACS grade also have limits on heavy metals.
In older versions they are listed as 'titrated as lead' or similar.
USP and ACS grades are codified in collaboration, so the tests and limits are close to identical.
Food grades are generally no where near the purity of USP or ACS grades and the impurities allowed are generally higher.
Food grade sodium hydroxide (lye) for example (used in pretzels) has the same basic specifications.
Differences, USP/ACS grade requires 97% sodium hydroxide, FCC requires 95%.
Potassium is limited to 0.5% in FCC but 0.02% in USP/ACS grade.
Carbonate is limited to 1% in USP/ACS grade but 3% in FCC.

Mercury is limited to 0.1 ppm in ACS grade.
Food limitation is 0.5 ppm according to international standard and food grade additives can be higher provided the final product is expected to be below 0.5ppm.
US federal limit is 1ppm on mercury in food and additives.
For FCC and USP/ACS grade it is the same.