Kjeldahl Method: Estimate the protein content in food

Kjeldahl Method
Time to complete course: 52 min.

About Kjeldahl Method: Estimate the protein content in food Virtual Lab Simulation

In the Kjeldahl Method simulation, you will learn how to use the Kjeldahl method to determine the protein content of a food sample, and how to use LC-MS/MS to investigate if the sample has been adulterated to make the protein content seem higher than it is.

Analyze a milk powder sample

Your lab has received batch samples of milk powder from 3 different producers. Your mission is to analyze a sample from one of the batches using the Kjeldahl method, in order to determine the exact protein content, and to make sure this is consistent with the reported value.

Tracing the steps of the Kjeldahl method

An animation will introduce you to each step of the analysis, and show what goes on at the molecular level.You will then perform the acid digestion, steam distillation and finally a colorimetric titration, before being challenged with the calculations needed to transfer the lab result to a protein content in the sample.

Is everything what it appears to be?

How can you be certain that your findings are correct? There might be ways to fool the Kjeldahl method! In the second half of the simulation, you will look into how this can happen, and explore the powerful technique LC-MS/MS, which can be used to detect if a known adulterant has been added to any of the received milk powder batches.

Will you be able to safely release the milk powder batches for consumers around the world?

Get Started Now

Measure the protein content in a food sample with the Kjeldahl method, and investigate whether the apparent result has been tampered with by using LC-MS/MS.

Techniques In Lab

  • Kjeldahl method
  • LC-MS/MS chromatogram interpretation

Learning Objectives

At the end of this simulation, you will be able to…

  • Describe the steps involved in the Kjeldahl method
  • Analyze the nitrogen content of a food sample
  • Calculate the protein content of a sample from the determined nitrogen content
  • Explain why the Kjeldahl method cannot be used to identify milk powder that was cut with melamine
  • Apply the principles of spiking and recovery in analytical chemistry
  • Interpret basic LC-MS/MS data
  • Describe the fundamentals of an LC-MS/MS analysis
  • Argue whether food fraud has been conducted based on available data

Screenshots of Kjeldahl Method: Estimate the protein content in foodVirtual Lab Simulation


Dr. Melanie M. Erzinger

Dr. Melanie M. Erzinger

Laboratory of Food Biochemistry
ETH Zürich
Dr. Samy Boulos

Dr. Samy Boulos

Laboratory of Food Biochemistry
ETH Zürich
Sarah Frédérickx

Sarah Frédérickx

Dep. of Health Sciences and Technology
ETH Zürich
Dr. Laura Nyström

Dr. Laura Nyström

Dep. of Health Sciences and Technology
ETH Zürich

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