Nitrogen/Protein Determination of Insect Food and Animal Feed by Dumas Method

Significance of the Topic

The accurate measurement of protein content in food and feed is critical for regulatory compliance, nutritional labeling and quality control. As insect-based foods and feeds gain traction due to their high protein content and sustainable production, reliable protein determination methods are essential to ensure product safety, traceability and economic value.

Objectives and Study Overview

This work evaluates the Dumas combustion method for nitrogen/protein analysis of various insect-based food and animal feed samples. It compares performance using helium and argon as carrier gases and benchmarks results against official method requirements.

Methodology and Used Instrumentation

The study employed dynamic flash combustion of homogenized samples in a Thermo Scientific™ FlashSmart™ Elemental Analyzer with the following setup:

• Sample preparation: Tin capsules, ball-mill homogenization.
• Autosampler: Thermo Scientific™ MAS Plus.
• Combustion: Pure oxygen injection optimized by OxyTune™.
• Gas flow: Helium or argon carrier gas.
• Post-combustion: Copper reduction reactor, CO₂/H₂O traps, GC column.
• Detection: Thermal Conductivity Detector (TCD).
• Software: EagerSmart™ Data Handling for parameter control, automatic nitrogen-to-protein conversion (factor 6.25).
• Calibration: Nicotinamide (22.94% N) and aspartic acid (10.52% N) standards using K-factor method.

Main Results and Discussion

Both carrier gases delivered comparable nitrogen and protein results across a broad concentration range of insect samples:

• Repeatability (RSD) consistently below 2%—meeting or exceeding official method criteria.
• No memory effects observed, indicating full combustion and accurate detection regardless of sample matrix.
• Protein values aligned closely whether helium or argon was used, validating argon as a cost-effective alternative.

Benefits and Practical Applications

The FlashSmart Elemental Analyzer offers several advantages over traditional Kjeldahl analyses:

• Full automation: streamlines sample throughput and reduces manual handling.
• Faster cycle times: dynamic flash combustion accelerates analysis.
• Matrix-independent performance: no sample-specific adjustments needed.
• Cost efficiency: argon use eliminates potential helium shortages and cost spikes.

Future Trends and Opportunities

As insect-based ingredients expand in global markets, rapid and reliable protein analysis will be in growing demand. Future developments may include:

• Integration with online process monitoring for real-time quality control.
• Miniaturized analyzers for decentralized testing in farms and feed mills.
• Enhanced software analytics using machine learning for predictive maintenance and auto-optimization.

Conclusion

The Dumas combustion method implemented on the FlashSmart Elemental Analyzer delivers accurate, reproducible nitrogen/protein determinations for insect-derived foods and feeds. Using argon as a carrier gas provides a cost-effective alternative to helium without sacrificing performance, fulfilling official method requirements and offering laboratories a robust solution for high-throughput protein analysis.

References

AOAC Official Method 990.03. Protein (Crude) in Animal Feed, 4.2.08.
AACC Approved Methods of Analysis.
AOCS Official Methods and Recommended Practices.
IDF Standard Methods.
ISO Standard Methods for Nitrogen Determination.
IFFO Protein and Amino Acid Standards.