Understanding Amines, Nitrosamines, and the Start of the Concern over Cured Meats

By Eben van Tonder, 28 April 26

Celebrating Dr Eduard Polenske: The First to Uncover the Nitrate to Nitrite Transformation. This image is an imagined scene of a hygienist teaching in Germany in the late 1800s, the era when Dr Eduard Polenske made his discovery.

When I wrote my detailed article “Nitrosamines, Cured Meats, and Human Health – A Critical Review of Risk and Physiology” on EarthwormExpress, it was never meant to be an ordinary piece. It became a long and unusual work because I wanted to break through the confusion surrounding nitrosamines in cured meats and look at the subject honestly, using both historical and scientific insights. However, I realise that not everyone has the time or patience to dig through such a technical document. So, I have decided to create a more accessible version, broken into smaller articles, each telling part of the full story in a way that anyone can follow.

In this series, I will guide you through the key aspects of the nitrosamine issue:

First, we will understand what amines and nitrosamines are, how they form, and why they matter.
Then, we will move into the historical evolution of the nitrosamine concern in meat curing.
After that, we will explore the chemistry behind how nitrosamines actually form.
We will look at the real health implications: separating fear from fact.
Then we will examine the many ways the meat industry and science have found to minimise nitrosamine formation.
We will review how governments and food regulators responded.
And finally, we will think about the future: what new research is teaching us, and how the story continues.

Each article will stand alone but together, they will give a complete, understandable view of the subject, based firmly on the research and historical evidence I presented originally.

Before we dive into the history or the chemistry, we need to start with the basics: understanding amines themselves, because without this, the rest of the story makes no sense.

An amine is a type of organic compound derived from ammonia (NH₃). Think of ammonia as a simple molecule: one nitrogen atom with three hydrogen atoms attached. When one or more of those hydrogens are replaced with carbon groups, we get amines. There are three main types:

Primary amines have one carbon group attached to the nitrogen (like methylamine, CH₃NH₂).
Secondary amines have two carbon groups attached (such as dimethylamine, (CH₃)₂NH).
Tertiary amines have three carbon groups attached (for example, trimethylamine, (CH₃)₃N).

The secondary amines are particularly important for us. They are more chemically active than primary amines because the two carbon groups pull electron density towards the nitrogen atom, making the nitrogen more available for further reactions. This extra reactivity will become central when we talk about nitrosamines.

The discovery of amines is an interesting story in itself. August Wilhelm von Hofmann, a young German chemist, first isolated and studied them in the mid-19th century. Hofmann had been a student of the great Justus von Liebig at the University of Giessen in Germany. After completing his studies under Liebig, Hofmann was invited to London, where he became the first director of the newly founded Royal College of Chemistry. It was during his time there, in London, in 1849, that he made the crucial discoveries about amines (Hofmann, 1849). Working with organic substances and ammonia, Hofmann noticed that when ammonia reacted with certain organic compounds, it produced related but distinct molecules – the amines we now classify as primary, secondary, and tertiary. His work laid the foundation for much of organic chemistry, even though at the time, the full implications were not yet clear.

Now, why does this matter for cured meats?

Meat, being made of protein, naturally contains amines. These amines are released or created during normal protein breakdown processes. When we cure meat, we introduce nitrite – a powerful preservative that prevents bacterial spoilage and maintains the attractive pink colour of cured products like bacon and ham. But under certain conditions, particularly when the meat becomes acidic or is exposed to high heat during cooking (like frying bacon), the nitrite can react with these amines to form nitrosamines.

The chemical reaction is straightforward: Nitrite (NO₂⁻) + Secondary Amine → Nitrosamine.

This reaction is much more likely under acidic conditions, and especially when the food is cooked at high temperatures. That is why concerns about nitrosamines in food often focus not just on how meat is cured, but even more on how it is cooked.

Why worry about nitrosamines? Certain nitrosamines, particularly the group known as N-nitrosamines, have been found to cause cancer in laboratory animals (Lijinsky, 1986). This discovery triggered a wave of concern in the 1970s when researchers started detecting trace amounts of nitrosamines in fried bacon and other cured meats.

However, as I explored in Bacon & the Art of Living on EarthwormExpress, the discovery of nitrosamines was not an indictment of bacon or of meat curing itself. It was a window into a much broader truth: that nitrogen chemistry, when combined with organic compounds and the right environmental conditions, could sometimes produce harmful by-products. Bacon simply became the symbol of the issue because it was beloved, widely consumed, and often cooked at temperatures that favoured nitrosamine formation.

Importantly, the food industry did not sit still. Research led to the addition of blocking agents like ascorbate (vitamin C) and erythorbate, which greatly reduce nitrosamine formation during curing (Cassens, 1997). These substances interrupt the chemical chain reactions that would otherwise lead to nitrosamines.

To tell the story properly, we had to begin here:

Knowing what amines are.
Seeing why secondary amines are special.
Understanding how nitrosamines form.
And remembering how this entire field of study started, with Hofmann’s experiments in London nearly two centuries ago.

In the next article, I will take you through the unfolding historical timeline: how scientists, public health officials, and the meat industry reacted to the discovery of nitrosamines, and how the modern perception of risk evolved from those early days.

Link to all my work on meat curing and human health. / Link zu all meinen Arbeiten über Fleischpökelung und menschliche Gesundheit.

References:

Hofmann, A. W. (1849). On the action of ammonia on organic bodies. Philosophical Transactions of the Royal Society of London, 139, 259–270.
Lijinsky, W. (1986). The significance of nitrosamines as environmental carcinogens. Journal of Environmental Science and Health. Part C, 4(1), 1–45.
Cassens, R. G. (1997). Residual nitrite in cured meat. Advances in Experimental Medicine and Biology, 433, 95–102.
Van Tonder, E. (2024). Nitrosamines, Cured Meats, and Human Health – A Critical Review of Risk and Physiology. EarthwormExpress.
Van Tonder, E. (2024). Bacon & the Art of Living. EarthwormExpress.

Tomorrow’s Article: Short Introduction

Tomorrow, I will continue the story by tracing the historical development of the nitrosamine issue. I will show how the first alarm bells were sounded, how early scientific studies shaped public perceptions, and how the meat industry and regulatory agencies responded.
It was not a story of immediate clarity or action — rather, it was a confused and at times emotional journey through early toxicology research, public fear, and the search for real solutions.
We will step into the world of the 1950s, 60s, and 70s, when the nitrosamine question first burst into public consciousness, and see how it changed everything from sausage recipes to international food law.