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Methods to determine total protein in foods.

Protein determination methods can be classified into two groups:

1. Methods that determine total nitrogen:

First, you will learn how protein values could be calculated based on nitrogen values. Here you will learn about two methods that are often used to determine nitrogen contents of foods:

• Kjeldahl method.

• Dumas method.

2. Methods that determine total protein directly:

• Biuret and other dye binding procedures

• Infrared spectroscopy.

However, since these methods are almost never used to determine values for FCDB, this methods will be explained only shortly and are not covered in depth.

Methods to measure specific amino acids.

In addition to total protein values, some FCDBs contain also values for specific amino acids. Therefore, the second part of this section gives you information on methods for amino acid determination.

Not covered: methods to determine specific proteins or peptides.

Besides this, it is also possible to determine specific proteins or peptides in foods e.g. whey protein or wheat proteins, by for example gel electrophoresis. However, as you learned in the previous part, currently FCDBs do not contain values on specific proteins or peptides. Therefore these methods are not covered in this case.

So far you refreshed your knowledge on the structure and function of proteins and amino acids in foods. You need this knowledge to understand the ins and outs of the methods that are used to obtain the protein and amino acid values for FCDBs. This section has the following structure