Carbon and Nitrogen Determination in Food and Beverages

Nitrogen is everywhere. It is one of the fundamental building blocks of life, continuously circulating through the environment in what is known as the nitrogen cycle. From atmospheric nitrogen fixation to plant uptake, from animal metabolism to human nutrition, nitrogen defines biological growth and energy transfer.

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In the food and beverage industry, this universal element plays a particularly important role, as it forms the foundation of proteins.

Proteins are not only essential nutrients but also key economic indicators, quality markers, and regulatory parameters. Whether in cereals, meat, dairy, plant-based alternatives, or beverages, nitrogen content directly translates into protein content. This relationship makes nitrogen determination one of the most critical analytical tasks in modern food production.

At the same time, the food industry is undergoing a transformation. The emergence of “new proteins” - including plant-based substitutes, insect protein, algae-derived ingredients, and fermentation-based products - is redefining both raw materials and finished goods. These innovations are driven by sustainability goals, economic efficiency, and changing consumer preferences.

However, they also introduce new analytical challenges. Different matrices, varying nitrogen compositions, and alternative protein conversion factors require precise, reliable, and flexible analytical methods. In this evolving landscape, accurate nitrogen and carbon determination is not just a laboratory task; it is a cornerstone of product integrity, regulatory compliance, and economic success.

Why Carbon and Nitrogen Determination Matters

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Nitrogen as an Indicator of Protein Content

Protein content is one of the most important values displayed on a food label. In the European Union, the Food Information to Consumers Regulation (EU) No 1169/2011 (LMIV) defines how protein must be declared. According to this regulation, protein content is calculated as:

Protein (%) = Nitrogen (%) × conversion factor

The default conversion factor is 6.25, based on the assumption that proteins contain approximately 16 % of nitrogen. However, this factor is not universal. For example:

• Wheat and cereals often use 5.7 %
• Dairy products use 6.38 %
• Other matrices may require specific factors depending on amino acid composition

Carbon as an Indicator of Consistency

Carbon is the main structural element of all organic compounds: carbohydrates, fats, proteins, or organic acids. The amount of total carbon (TC) is, therefore, a direct indicator of the total organic content in a food sample.

This can be used to set nutritional values for the end customer, document batch-to-batch consistency, or detect formulation deviations. For example, stable carbon values in flour or starch products indicate consistent carbohydrate composition, which in turn stands for consistent quality. In processed foods, changes in total carbon content may reflect variations in composition, such as moisture loss or formulation differences. In certain applications, carbon analysis can support process monitoring, for example in roasted cereal products, coffee, or baked goods.

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This means that accurate carbon and nitrogen measurement is the foundation of correct nutritional labeling. Errors in their determination directly translate into incorrect protein values or formulation changes, which can lead to regulatory issues, product recalls, or financial losses. Beyond labeling, carbon and nitrogen analysis plays a critical role in:

Raw Material Purchasing and Pricing

Protein content directly affects the value of commodities such as grain, soy, dairy products, and meat.

Process Control

Monitoring protein levels ensures consistency in production processes such as baking, fermentation, or extrusion.

Quality Assurance

Nitrogen plays an important role in verifying product specifications and detecting deviations, especially in batch-to-batch consistency.

Sustainability and Efficiency

Precise formulation optimizes resource use and reduces waste.

Compliance with International Standards

This includes AOAC, ISO, DIN EN ISO, and industry-specific methods.

Beyond regulatory compliance, component analysis plays a decisive role in industrial practice. In grain trading, for example, protein and carbon content determine classification and price. Even small analytical deviations can translate into significant financial differences across large volumes.

Similarly, in food production, incorrect values may lead to batch rejection or costly reformulation, particularly in tightly controlled processes such as baking or plant-based product manufacturing.

Carbon and nitrogen determination is therefore not simply an analytical parameter; it acts as a link between laboratory measurement and economic decision-making. It ensures that raw materials meet contractual specifications, that processes remain stable, and that final products comply with both internal and external requirements.

Analytical Challenges in Modern Protein Determination

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As the food industry evolves, so do the challenges associated with nitrogen and protein analysis. Traditional food matrices already require careful handling, but the rise of alternative proteins introduces an additional layer of complexity: the diversity of modern food products and the importance of matrix effects increase.

High-fat samples behave differently during combustion to fiber-rich plant materials, and processed foods may contain multiple components with varying thermal and chemical properties. These differences influence combustion efficiency and gas release, ultimately affecting measurement stability.

Another limitation arises from the use of generalized conversion factors. While convenient, they do not fully account for the variability in protein composition across different sources. This becomes particularly relevant for novel protein ingredients, where standardized factors may not yet be fully established.

Taken together, these aspects highlight a key reality: protein determination is no longer a simple calculation, but a matrix-dependent analytical task that requires robust and reproducible measurement methods.

From Kjeldahl to Dumas: Evolution of Nitrogen (and Carbon) Analysis

For more than a century, the Kjeldahl method has been a reference method in many standards. The procedure requires the handling of concentrated acids, involves multiple manual steps, and typically takes several hours per analysis.

Figure 1. Comparison of nitrogen analysis with the Kjeldahl and the Duma method. Analysis time for Dumas is based on using an ELEMENTRAC CN-r from Eltra. Image Credit: ELTRA

The Dumas combustion method, on the other hand, represents a modern, automated alternative. By combusting the sample at high temperature in an oxygen atmosphere and directly measuring the resulting gases, the method eliminates the need for hazardous chemicals and significantly reduces analysis time.

It additionally enables the simultaneous determination of carbon and nitrogen. Results are typically available within minutes, enabling high-throughput operation in routine laboratories.

In addition, the cost per sample is generally lower with the Dumas method compared to Kjeldahl. While Kjeldahl requires significant amounts of chemicals (such as concentrated acids and catalysts) as well as labor-intensive handling, the Dumas method mainly relies on consumables like carrier gases and combustion tubes, resulting in reduced operating costs over time.

A further advantage becomes evident when considering laboratory throughput. Within an eight-hour working day, the Kjeldahl method typically allows for the analysis of approximately 40–80 samples, depending on the level of automation and parallel digestion capacity.

In contrast, a modern Dumas analyzer such as the ELEMENTRAC CN-r can process roughly 160 samples in the same time frame, as each analysis only takes a few minutes and requires minimal manual intervention. This makes the Dumas method particularly attractive for high-throughput routine laboratories.

Dumas Combustion Designed for Food Laboratories

ELEMENTRAC CN-r – Next-Generation Carbon, Nitrogen & Protein Analyzer. Video Credit: ELTRA GmbH

The ELEMENTRAC CN-r applies to the Dumas principle in a way that is particularly suited to the demands of food and beverage laboratories. Food samples are often heterogeneous, containing varying proportions of proteins, fats, carbohydrates, and moisture. The integrated ballast and aliquot system ensure that the measured gas fraction is representative, which significantly improves reproducibility even for complex matrices.

At the same time, the use of excess oxygen ensures complete combustion, independent of the sample type. Combined with the absence of wet chemical reagents, this contributes to a safer and more sustainable laboratory environment. The short analysis time of two-and-a-half minutes per sample allows laboratories to integrate carbon and nitrogen determination directly into production and workflows.

Application in Food Matrices: From Sample to Result

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The reliability of carbon and nitrogen determination depends heavily on how the sample is prepared. Regardless of whether the material is a cereal, a meat product, milk, wine, or a plant-based alternative, the goal is always the same: to obtain a representative and homogeneous sample.

In routine laboratories, this often means grinding solid samples to a defined particle size, typically between 800 and 1000 µm (e.g., for wheat analysis according to DIN EN ISO 16634-2). This ensures consistent combustion behavior and stable analytical signals. At the same time, care must be taken to avoid excessive heat during grinding, as this can alter the sample composition.

For more complex matrices such as meat or high-moisture products, thorough homogenization is essential. For example, in milk analysis, proper homogenization is essential, as milk is a complex oil-in-water emulsion consisting of dispersed fat globules within an aqueous protein phase. Such samples are particularly sensitive to storage effects, which is why analysis should ideally be carried out immediately after preparation.

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Once the sample is prepared, an operator simply weighs the sample into tin foil or tin capsule, places it in an autosampler, and the analyzer does the rest. The ELEMENTRAC CN-r is built for continuous high-throughput operation: its maintenance mode allows rapid replacement of consumables and reagents in about 15 minutes–all while the analyzer remains in a ready state.

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In high-throughput laboratory environments, analytical performance is not only defined by measurement accuracy, but also by operational efficiency. Routine analysis often involves large sample volumes across diverse matrices, making instrument uptime a critical factor. For this reason, maintenance procedures must be fast, simple, and reproducible. This ensures continuous operation and reduces downtime, allowing nitrogen determination to be fully integrated into daily laboratory workflows without becoming a bottleneck.

For example, exchanging regular consumables in the ELEMENTRAC CN-r like the crucible, is done within one minute, and exchanging the whole combustion quartz tube only takes about two minutes. Exchanging all consumables takes about 15 minutes, while the analyzer is in a ready state.

Video Credit: ELTRA

Sustainability and Efficiency from a Circular Perspective

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The discussion of nitrogen in food systems ultimately returns to its origin: the nitrogen cycle. As industries move toward more sustainable production methods and alternative protein sources, analytical techniques must also evolve.

Modern combustion methods contribute to this transition by reducing the need for chemical reagents and minimizing waste. Faster analysis times not only improve laboratory efficiency but also reduce energy consumption per sample. More importantly, precise carbon and nitrogen determination enable better control of formulations, helping to avoid overuse of raw materials and reduce food waste.

In this way, analytical accuracy becomes part of a larger system of resource efficiency. It connects raw material use, process optimization, and final product quality, closing the loop between environmental responsibility and industrial performance.

As food systems evolve, analytical precision becomes more than a lab metric. Discover how advanced combustion methods are helping connect sustainability, efficiency, and product quality.

Talk to Eltra's experts about solutions tailored to your application here.

References

1. FAO (2011). Dietary protein quality evaluation in human nutrition Report of an FAO Expert Consultation. Available at: https://www.fao.org/3/i3124e/i3124e.pdf.
2. van Huis, A., et al. (2013). Edible insects Future prospects for food and feed security Edible insects Future prospects for food and feed security. Available at: https://www.fao.org/3/i3253e/i3253e.pdf.
3. FAO (2013). A Global Assessment of Emissions and mitigAtion Opportunities Tackling Climate Change Through Livestock. Available at: https://www.fao.org/3/i3437e/i3437e.pdf.
4. OECD (2023). OECD-FAO Agricultural Outlook 2023-2032. OECD. Available at: https://www.oecd.org/en/publications/oecd-fao-agricultural-outlook-2023-2032_08801ab7-en.html.
5. European Union (2011). EUR-Lex - 32011R1169 - EN - EUR-Lex. European Union. Available at: https://eur-lex.europa.eu/eli/reg/2011/1169/oj/eng.

This information has been sourced, reviewed, and adapted from materials provided by ELTRA.

For more information on this source, please visit ELTRA.