Short Note #21: Protein Determination in Cheese According to the Kjeldahl Method

Buchi Kjeldahl Solutions - Food & Beverage

Buchi Kjeldahl Solutions - Food & Beverage

The determination of protein in food is a routine procedure for quality assurance and labeling and is one of the key analyses performed in the food industry. A simple and fast procedure for protein determination in cheese, as described in the DIN EN ISO 8968:2001 appendix A regulations, is introduced in this short note. Download the short note on the protein determination in cheese and review our Kjeldahl Applications database to request or download our other short notes.

The samples require digestion with sulfuric acid to convert nitrogen into ammonium sulfate. After conversion to ammonia through the alkalinization with sodium hydroxide, the sample is distilled into a boric acid receiver by steam distillation, followed by a titration with sulphuric acid solution. The nitrogen content is multiplied by a sample-specific factor (6.38 for cheese) to obtain the protein content.

SpeedDigester K-436, K-439, Kjeldahl Sampler System K-370/K-371

Cream cheese and Emmentaler cheese, grinded, labeled protein contents 6 % and 33 %, respectively.