Applications

Nitrogen and protein determination in dairy products

Nitrogen and Protein Determination in Dairy Products (Kjeldahl Tablets)

Protein determination is one of the key analyses performed in the food industry. The samples require digestion with sulfuric acid to convert nitrogen into ammonium sulfate. Hydrogen peroxide is used to accelerate the digestion process. 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 sulfuric acid solution. The nitrogen content is multiplied by a sample-specific protein factor (6.38 for dairy products) to obtain the protein content.

Nitrogen and Protein Determination in Bran Products

Protein determination is one of the key analyses performed in the food industry. 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 sulfuric acid solution. The nitrogen content is multiplied by a sample-specific factor (5.7 for wheat and oat) to obtain the protein content.

Nitrogen and protein determination in dairy products

Protein determination in plant-based meat alternatives

Plant-based meat alternatives are gaining popularity as a result of growing health and climate concerns. Being based on proteins derived from plants instead of traditional protein sources of animal origin, these products are being critically evaluated not only for their taste and texture but also for their nutritional value. An easy and reliable Kjeldahl method for the determination of total nitrogen and protein in plant-based meat alternatives, is presented below. In this method, samples are digested using the KjelDigester K-449. Distillation and boric acid titration are performed with the KjelMaster K-375 and KjelSampler K-377. A combination of the KjelDigester K-449 and KjelMaster system K-375/K-377 offers high sample throughput.

Nitrogen determination in soil

Nitrogen determination in diphtheria and tetanus toxoids according to Pharmacopoeia using back titration and boric acid titration

Nitrogen and total protein determination in pharmaceutical products are described in the European Pharmacopoeia (Ph. Eur.) and in the Pharmacopoeia of the United States (USP). Therein, different titration techniques are specified. The Ph.Eur. is using back titration in the presence of the indicator methyl red mixed solution and the USP is using potentiometric and colorimetric boric acid titration.In this application note, the three different titration techniques were compared and the reproducibility was determined. The nitrogen content of two toxoid samples was determined by sulfuric acid digestion using the KjelDigester K-449 followed by steam distillation and titration applying the BUCHI KjelMaster System K-375 / K-376.

Nitrogen and protein determination in dairy products

Nitrogen determination in Tobacco

It is considered that flavour and taste of smoke is correlated with the nitrogenous constituents. Accordingto Indian Central Tobacco Reseach Institute (CTRI) fluecured tobacco containing 1.6 to 2.3 % total nitrogen gives the most satisfying smoke, whereas the acceptable limit of total nitrogen is 1.0-3.0 %.High level of nitrogen in tobacco is associated with a high level of nicotine. A low nitrogen content would result in ‘washed out’, pale coloured leaf, lacking in rich colour characteristic of good tobacco. Therefore, the determination of total nitrogen is an important quality control measure in the tobacco industry.Here, the determination of nitrogen in tobacco is performed using the SpeedDigester K-425 and KjelMaster K-375.

Nitrogen & protein determination in starch and gluten

Accelerated nitrogen and protein determination in dairy products

Selective nitrogen determination methods related to Kjeldahl

85 % of the world's nitrogen demand for fertilizer is primarily derived from ammonia in the form of urea, ammonium nitrate, phosphate and sulfate. Ammoniacal components can also be found in soil, sludge and bio waste. In those sample matrices, a mixture of several nitrogen containing compounds as urea, nitrogen from other organic origin such as amino acids, proteins, nitrate, nitrite and ammonium can be found.Using the Kjeldahl equipment, selective nitrogen determination of the Total Kjeldahl Nitrogen (TKN and TKN+), the ammonium (ammonium distillation) and the nitrate concentration (Devarda distillation) of a sample is possible. In addition, to these parameters, the organic nitrogen content can be calculated.

Nitrogen and Protein Determination in Animal Feed according to the Kjeldahl method

Nitrogen & protein determination in corn, flour and soy

An easy and reliable method for the determination of total nitrogen and protein in corn, flour and soy, according to ISO 20483:2006 and LFGB §64 L15.00-3, is introduced below. The samples are digested using the KjelDigester K-449. The distillation and boric acid titration are performed with the KjelMaster K-375 with KjelSampler K-376. The combination of the KjelDigester and the KjelMaster system K-375/K-376 increases the sample throughput.

Nitrogen and protein determination in dairy products

The determination of protein in food is a routine procedure for quality assurance and labelling. A simple and fast procedure for protein determination in dairy products, according to ISO 8968-3 and AOAC 991.20 is introduced below. The sample is digested with sulfuric acid, the Kjeldahl Tablet Titanium and hydrogen peroxide using the KjelDigester K-449 – followed by distillation and titration with the KjelMaster system K-375 / K-376. The determined protein contents correspond to the labelled values. 

Find out more in this application note No. 197/2015.

Nitrogen determination in sodium nitrate and fertilizer

An easy, quick and sensitive method for the analysis of nitrogen in sodium nitrate using the Devarda method is described in this application note. Devarda distillation with the steam distillation unit MultiKjel was followed by boric acid titration on the Metrohm Eco Titrator. The Devarda method is used for the determination of nitrogen as sum parameter in nitrate and nitrite. However, this method is not suitable in the presence of organic compounds, calcium cyanamide or carbamide. Devarda’s alloy reacts with sodium hydroxide to form hydrogen. The produced hydrogen reduces the nitrate and nitrite to ammonia. The ammonia is then trapped in boric acid solution and titrated with standard sulfuric acid.

Nitrogen and urea determination in cosmetics

Nitrogen and Protein Determination in Animal Feed with Kjeldahl Tablets and Hydrogen Peroxide

Accelerated nitrogen & protein determination in beer and malt

An easy and reliable method for the determination of total nitrogen and protein in beer and malt by the use of hydrogen peroxide, is introduced below. The samples are digested using the KjelDigester K-449. The distillation and boric acid titration are performed with the KjelMaster K-375 with KjelSampler K-376. The combination of the accelerated digestion method, using the Kjeldahl Tablet Titanium in combination with hydrogen peroxide, and the KjelMaster system K-375/K-376 increases the sample throughput.

Nitrogen and Protein Determination in Milk by Digestion

The digestion with hydrogen peroxide 30% instead of Kjeldahl tablets for nitrogen and protein determination [1] is a very fast (30 min instead of 85 min (K-439) or 100 min (K-436)) and environmentally friendly (free of any heavy metal) alternative to the classical Kjeldahl methods.