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I'm currently in the Republic of Georgia, and locals sell farmer cottage cheeses at the markets. These cheeses are albumin-based "nadugi" and casein-based "hacho". No nutritional info is available for them. I would like to measure protein content of the cheeses I buy, even if approximately. Is there a way to do this at home?

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    Simple answer: no. Even simple methods are going to require chemistry equipment, chemicals, and lab equipment. And even then you have to be aware of the error bars associated with the measurements, some methods work better on some foods than others etc etc.
    – eps
    Aug 22, 2022 at 14:04
  • Eps: that's an answer.
    – FuzzyChef
    Aug 22, 2022 at 15:13
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    I wonder whether one can do that by the exclusion. Measure the water and fat content (is that easy without lab equipment?) Apart from that there are small amounts of sugar and salt in cheese, everything else must be protein.
    – quarague
    Aug 23, 2022 at 11:01
  • I don't see why not. I could hang the cottage cheese up in a cloth sack above a source of heat hoping that the heat melts the milk fat, and then maybe lightly fry the resultant product to evaporate the water? Aug 27, 2022 at 18:22

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No, this is not something you can do at home (except if you are Walter White). Here is a good overview of common methods: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7597951/pdf/foods-09-01340.pdf

Below is a chart from page 2 which summarizes the methods:

Table 1. Protein quantification methods—advantages and disadvantages.

Protein Quantification Method Advantages Disadvantages
Kjeldahl method—digestion of food with a strong acid so that nitrogen is released which is then quantified using a titration technique. Considered the standard method globally and therefore easy to compare results with other laboratories Does not measure true protein and overestimations of protein can result due to use of standard nitrogen correction factor 6.25
Dumas method Fast and does not use chemicals; can measure several samples at a time Costly to set up and is not very accurate as it does not measure true protein.
UV spectroscopy methods Simple, does not require any assay agents Highly error prone due to other compounds that absorb at the selected absorbance wavelength (280 nm)
Biuret methods—protein–copper chelation and secondary detection of reduced copper, includes the bicinchoninic acid (BCA) and Lowry assay methods Less protein–protein variation than the Coomassie dye-based assays; compatible with most surfactants used for protein extraction Incompatible with copper-reducing surfactants and reducing agents including DTT
Bradford Coomassie Blue assay method—protein–dye binding and direct detection of the color change Fast, performed at room temperature, compatible with most solvents High protein–protein variation; incompatible with detergents
Fluorescent dye methods—protein–dye binding and direct detection of increase in fluorescence associated with the bound dye includes the Qubit assay and EZQ TM assay Very sensitive and uses less protein Requires a fluorescence detector
Direct amino acid analysis using hydrolysis and HPLC quantification Accurate Initial investment in HPLC equipment required; hydrolysis step required; time consuming

I'm not going to pretend to understand all of that, but the takeaway is that you either need semi-hazardous and (relatively) hard to obtain chemicals or access to expensive analyzers (often both).

You may consider contacting local universities' food science or chemistry departments. It's possible they will programs set up where they perform this sort of analysis for a fee or perhaps such analysis was already done and the university library can locate the journal article.

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    The best bet for home use would be the colorimetric BCA/Biuret/Bradford methods. The dyes (at least coomassie) are relatively simple to acquire and don't require expensive instruments to measure, just visual against standards would be enough. However, I don't know how the fats in cheese might affect these. Standards could be made from protein (e.g. egg powder, casein powder) in a salt solution.
    – bob1
    Aug 22, 2022 at 21:14
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    FWIW, I looked at how cheesemakers do this. While they have a variety of approximate methods that don't require chemicals, all of them require having complete knowledge of the ingredients that went into the cheese in the first place.
    – FuzzyChef
    Aug 22, 2022 at 21:55

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