Protein Determination in Cereals

Cereal products are one of the most important staple foods and have been so for thousands of years. About two billion tons of cereals are produced in the world annually. The cereal and grains products that most of us eat everyday look very different compared to the grain grown in the field or paddy. Many different processing steps are taken in order to turn the coarse grain into the products on our supermarket shelves.

Cereals contain between 8-15% of different kinds of proteins such as albumins, globulins, prolamines, gliadins, glutelins and glutenins, but also provide carbohydrates, dietary fiber and vitamins.
Protein content in malted barley is an important criterion in evaluating the quality of beer: water-soluble barley proteins play a major role in the formation, stability, and texture of head foams.
 

The Dumas method starts with a combustion furnace (CF) to burn the sample, obtaining elemental compounds.

Water is removed by a first physical trap (WT1 - DriStep™), placed after the combustion, and a second chemical one (WT2). Between the two, the elemental substances pass through a reduction furnace (RF). The auto-regenerative CO2 absorbers (CO2) let pass only the elemental nitrogen that is detected by the LoGas™ innovative thermal Conductivity Detector (TCD) with no requirement for a reference gas.

The NDA 701 is controlled via PC through the intuitive DUMASoft™.

Conclusion
Despite the low homogeneity of the cereal samples, the results are repeatable. The combustion method, relying on the Dumas principle, for the determination of total nitrogen in cereal samples, has been included as an official alternative to the Kjeldahl method. Results have been obtained with the following calibration curve: in a range of 0 - 5 mg N with 5 measurements of EDTA standard (%N = 9.57)

Benefits of Dumas combustion method are:

• High productivity, non-stop performance
• Time-saving, few minutes required
• Moderate running costs
• Totally unsupervised, fully automated
• Omission of harsh and toxic chemicals
• Eco-friendly, low amount of residues and wastes

Several organizations working with standardization and recommendation of chemical methods have approved combustion methods for the determination of nitrogen.
Of those related to brewing, the American Society of Brewing Chemists (ASBC) has approved combustion methods for nitrogen determination in brewing grains as well as in wort and beer.