Protein is a critical nutrient in cattle, pig, poultry, sheep, horse and pet foods. Although protein supplements are high cost they are sometimes necessary in order to meet the animal’s nutritional requirements. An adequate protein content in feed products is important for animal health and productivity, as well as for ranch profitability. The protein requirements of cattle vary with age, size, and expected performance. During lactation, larger cattle typically require more pounds of crude protein per day than smaller animals, but as a lower percentage of their total dry matter intake. In other words, lighter cattle require higher quality feeds and forages at lower quantities compared with heavier cattle. Cattle requirements for crude protein rise with increasing lactation and rate of gain. Protein is required for milk production and reproductive tract reconditioning after calving

 

In 1883, Johan Kjeldahl introduced his "New Method for the Determination of Nitrogen in Organic Bodies", revolutionising nitrogen analysis and setting new standards. Since then, the method has become indispensable in areas such as food analysis, feed analysis, soil analysis and water analysis. However, it is by no means limited to these areas: This versatile method can also be found in the industrial or in the pharmaceutical sectors and wherever the nitrogen content is important.

 

In the traditional application, manual laboratory heaters are used, as well as round-bottom flasks for digestion and Erlenmeyer flasks for distillation. After the publication of the Kjeldahl method, C. Gerhardt set itself the goal of optimising this classic application. Over the last decades, a large number of different instrument types have been developed for this purpose. It all started with large cast-iron racks; today there are highly precise block digestion units and steam distillation units with result calculation and automatic sample feeding.

 

Kjeldahl is nowadays the most used method for determining nitrogen and protein contents in foods and feeds thanks to the high level of precision and reproducibility and to its simple application. The modern Kjeldahl method consists in a procedure of catalytically supported mineralization of organic material in a boiling mixture of sulfuric acid and sulfate salt at digestion temperatures higher than 400 °C. During the process the organically bonded nitrogen is converted into ammonium sulfate. Alkalizing the digested solution liberates ammonia which is quantitatively steam distilled and determined by titration.

 

In the presence of sulphuric acid and catalyst, the nitrogen atom in the nitrogenous organic compound is converted to ammonium sulphate. The ammonia is then distilled from an alkaline medium and absorbed in boric acid. The ammonia is then determined by titration with a standard mineral acid.



      

The flowchart of the Kjeldahl method protein/nitrogen determination





The VELP Scientific UDK Distillation Units are used to perform nitrogen and protein content analysis according to the Kjeldahl Method in the food and feed industries and for several other applications in environmental control(phenols, nitrogen in water, sludge, soil and lubricant), chemical and pharmaceutical industries after having digested the sample accurately. UDK distillation units work in accordance with a variety of Standards (such as AOAC, ISO, EPA, DIN etc.).  

 


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