Sustainable methods in modern nutritional analysis

Microwave-based fat determination in food and feed

The classical methods for fat determination (e.g. Röse-Gottlieb or Weibull-Stoldt) are gravimetric and are based on the hydrolysis of a sample with acid and the subsequent extraction of the fat with an organic solvent. This is time-consuming and involves a high consumption of chemicals and electricity.
In microwave-based fat determination, these chemical reaction steps are carried out in parallel in a closed vessel within a microwave (closed-vessel technology). This shortens the analysis time and reduces chemical consumption by 70%. Both methods are identical in terms of accuracy, sensitivity and robustness. However, the power consumption and space requirements of the microwave-based method are lower than those of the classical method.

Dumas for determining the protein content of food and feed

The Kjeldahl method has long been the most common method for determining the protein content of food, but in recent years the Dumas method has also gained in importance. It is based on the combustion of a sample and the subsequent determination of its total nitrogen content and offers a faster and safer alternative to the Kjeldahl method based on "green chemistry". This means that no aggressive acids, alkalis or SVHC (Substances of Very High Concern), which are on the candidate list for authorisation under the REACH regulation) are used in the Dumas analysis. The analysis per sample only takes about 5 minutes and not several hours as with the Kjeldahl method.

Dumas as an internationally recognised method

The Dumas method has been recognised for more than 25 years and is now validated by a number of international organisations including AOAC, AACC, ISO, AOCS and OIV. There are ISO standards for numerous food that use this method for the determination of proteins. In addition, Commission Regulation (EC) No 152/2009 states that the Dumas method may be used as a routine method for the analysis of crude protein in feed provided that it gives results comparable to those of the Kjeldahl method.

According to the European Labelling Regulation (EU) No. 1169/2011, the protein content to be declared is calculated using the formula “total nitrogen according to Kjeldahl x 6.25”. However, the regulation does not specify that the nitrogen has to be determined according to Kjeldahl, but primarily defines a standardised multiplication factor for all food types to calculate the protein content from nitrogen. As long as the nitrogen content determined according to Dumas is comparable to the nitrogen content according to Kjeldahl, the determined protein content meets the requirements of the labelling regulation. The Dumas method is currently being developed by us and is expected to be accredited by the DAkkS in spring 2025.

NIR for parallel fat, water, protein and BEFFE determination

NIR spectroscopy (near infrared spectroscopy) enables the combined determination of water, fat, protein and BEFFE content in a single analysis method. The sample is irradiated with light, the absorption spectrum is measured and the spectra are used to quantitatively determine the contents using a database. In contrast to the classic wet-chemical methods for water (drying oven), fat (Weibull-Stoldt), protein (Kjeldahl) and BEFFE (photometric determination), the analysis time of NIR spectroscopy is only a few minutes for all 4 parameters. In addition, it requires no chemicals, produces no waste and is non-destructive, so the sample material can be used for further analysis after NIR spectroscopy. We already offer accredited NIR spectroscopy for routine analysis of meat and cheese products. We are happy to extend the method for you by purchasing additional databases for other matrices such as baked goods, beverages, cereals and dairy products.