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I went out to buy flour for making regular western bread (perhaps sourdough if I can make the starter) and the only flour I could find was a 5kg Chakki Atta (medium) from a generic brand in my local supermarket. The package has no extra information about the contents.

That got me thinking: how do i find out what's the protein percentage in a particular flour without resorting to the package label? For sure there must be a scientific way, but how can I do it at home?

  • Beside the scientific way, this may be a good occasion to improve your cooking skills by just going by feel instead of a recipe - I really believe that the best cooks are those who have transcended the needs for recipe because they can tell by feel if a dough is right, and now you have a nice occasion to train :) The volcano method is a good place to start. – rumtscho Mar 27 at 11:45
  • @rumtscho definitely! I was just really wondering since I'm new to sourdough, in case I have to troubleshoot later at least I get this one variable checked. – Luciano Mar 30 at 8:18
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The lay person's procedure is: Take your flour and weigh a sample, then wash away the starch and weigh the sample.

Here is a video showing a procedure that you can do at home. I would suggest doing this procedure with a control sample (a flour where you know the protein content to determine your accuracy) before doing with your target sample.

https://www.youtube.com/watch?v=i6oQNo4gpeE

Here is a more scientific approach:

The amount of protein in a food material is usually determined by measuring the nitrogen content of the material and multiplying that value by a factor. The nitrogen content of a given protein varies depending on its source. For milk products a factor of 6.38 is used, for most cereal grains the factor is 6.25, and in wheat products the factor is 5.70. These factors depend on the percentage of nitrogen in the respective proteins.

The flour protein content is an important parameter for bread flour. Flours containing higher protein contents are more expensive than flours of lower protein content. Likewise, flours with very low proteins for cakes are also more expensive. There is usually, but not always, a good correlation between protein content and bakery performance of a flour.

The classic procedure to determine the nitrogen was the Kjeldahl procedure. This involved digesting the sample in concentrated sulfuric acid, then neutralizing the acid with concentrated sodium hydroxide, followed by distillation of the ammonia (derived from the nitrogen in the protein) into a standard acid. The procedure worked well, however it was an environmental nightmare. In addition to the strong acid and base, the catalysts used to speed the digestion included such materials as mercury and selenium. It should surprise no one that the procedure is seldom used today.

The Kjeldahl procedure has been replaced by the Dumas combustion procedure. In the original Dumas procedure the sample is mixed with cupric oxide and heated in a stream of carbon dioxide in a combustion tube packed with cupric oxide and copper metal. The organic material is converted to carbon dioxide, water and nitrogen. The gas stream is led into 50% potassium hydroxide. This absorbs the carbon dioxide and any oxides of sulfur, leaving only nitrogen as a gas. The volume of nitrogen is then determined. Various machines have been developed to carry out the analysis automatically. The percent nitrogen is then converted to protein using the appropriate factor. Both the Dumas combustion and the Kjeldahl procedures estimate the quantity (total amount) of protein and not the protein quality. As discussed elsewhere, the quantity of protein is extremely important in the baking performance of a flour.

source: https://www.ndsu.edu/faculty/simsek/wheat/flour.html

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Although you don't get a definitive, scientific answer this way I often compare brands when answering this type of question, looking at average and variation between them. If there is a great deal of variation the reliability of the average goes down.

I looked at several brands of Chakki Atta online and they all had 12% protein, there was zero variation, so it is likely that your flour has somewhere around 12% protein as well.

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  • yeah I saw another brand that was 12%, but I was wondering what would be a good method to figure out in case I find some unspecified type (let's say if I borrow from a neighbour that has 'random wheat flour' in the cupboard) – Luciano Mar 30 at 8:21

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