Making Mayo at Home: Cheaper, Tastier, and Salmonella-Free?

Mayonnaise is one of those kitchen staples we all have in the fridge, whether it’s for spreading on a sandwich, serving as a base for sauces, or even as a hair mask. Yes, I know it sounds odd, but I promise I tried it when I was fifteen. The result was surprisingly soft hair… though the smell was unforgettable for less-than-pleasant reasons.

But what is mayonnaise made of?

Mayonnaise is made with just four basic ingredients: eggs, oil, vinegar or lemon juice (or lime if you prefer a fresher flavour), and salt. While these ingredients are enough to make a simple mayonnaise, adding mustard is highly recommended. Not only does it add an incredible flavour, but it also helps keep bacteria at bay. Yes, it’s a natural preservative!

Now, before you get too excited about making homemade mayonnaise and start experimenting with avocado or olive oil for a healthier version, with lemon or lime juice, or even different types of vinegar to create unique flavours with varying acids—or simply adjusting the amount of salt to reduce sodium—let’s talk about the less glamorous side of this kitchen staple: the risks.

Is homemade mayonnaise safe? Everything you need to know about the risks and how to avoid them

Here’s where things get a little tricky. Raw eggs can pose a risk of Salmonella, a bacteria that can cause food poisoning. According to the Public Health Agency of Canada, Salmonella can be found both on the eggshell and inside the egg itself. They also recommend using pasteurized eggs for any recipe that won’t be cooked, like mayonnaise.

While researching this topic, I came across a rather fascinating study—although, to be honest, I didn’t finish reading it (because, let’s be real, it was dense). This study delves into the risks of contracting Salmonella from consuming raw eggs and even presents a mathematical formula to calculate this risk. The essential takeaway is something important: if we use pasteurized eggs, we significantly reduce the risk. If you’re scientifically curious and want to dive into the details, you can check out the full study here.

How can we make mayonnaise at home safely?

It’s very simple. You can use pasteurized eggs, liquid egg whites in a carton (which should also be pasteurized), or powdered eggs as a practical and safe alternative, even though they’re not very well-known.

What about the texture? Of course, egg yolks are what give mayonnaise its creamy consistency, thanks to their high-fat content and emulsifying properties. But don’t worry—I’ve added an extra ingredient: potato starch. It stabilizes the emulsion and helps achieve a very similar texture, even without the yolks.

Vinegar not only provides acidity but also acts as an antimicrobial agent and has other interesting properties, though that’s a topic for another post.

The Science Behind It

Mayonnaise is essentially an emulsion, which is a fancy word for describing the mixture of two liquids that normally don’t get along, such as water and oil. In this case, we’re talking about vinegar and oil.

Why don’t vinegar and oil mix?

If you combine vinegar and oil in a container, at first it might seem like they mix, but after a few minutes of resting, you’ll notice they separate into two distinct layers. This happens because oil is insoluble in water, meaning it cannot dissolve in it.

A good example to understand this difference is salt. Salt is soluble in water (to a certain extent, depending on the concentration, but that’s another story). If you mix water and salt, you’ll get a homogeneous liquid where you can’t distinguish one from the other. However, with oil and vinegar, the molecules simply don’t mix. That’s why we need something extra to bring them together: a third ingredient, an emulsifier.

The Role of the Emulsifier

An emulsifier, also known as a surfactant, has fascinating properties. One side of its molecule repels water (hydrophobic), while the other side attracts water (hydrophilic). This dual behaviour allows it to bind with both water and oil at the same time, breaking the surface tension that prevents it from mixing. Here’s where the magic of eggs comes in—specifically the yolk, which acts as the emulsifier in this recipe.

When we mix egg yolk, vinegar, and oil, something incredible happens. The droplets of oil, which were once large and easily separated, break into tiny particles surrounded by a layer of yolk and vinegar. This is called an “oil-in-water” emulsion, and this structure allows the mixture to remain stable, smooth, and creamy. In fact, this microscopic arrangement of dispersed droplets is why mayonnaise looks opaque and white: light scatters in all directions as it passes through the emulsion.

The stability of this mixture can be preserved as long as the conditions are carefully managed. Avoid sudden temperature changes and keep the mayonnaise refrigerated to enjoy it for a longer time. Of course, like everything, the emulsion has its limits and can break over time or under certain circumstances. But until then, we can enjoy this fascinating chemical phenomenon in the kitchen.

Isn’t it amazing? The kitchen is full of little scientific wonders like this, and mayonnaise is just one of many. Are you ready to try it yourself? At the end of this article, I’ve included an experiment for curious kids and adults alike.

If you’d like to learn more about emulsions and explore this topic with spectacular visuals, I recommend visiting this link I found: How Mayonnaise is Made: The Chemistry Behind It.