How Come Mexicans Don’t Refrigerate Eggs?

And is this safe?

We see eggs at the local market sitting there at room temperature. Many of us want to rush over and sweep them into a fridge. But do we need to?

The question is about salmonella, a type of bacteria that lives in the intestines of many warm blooded animals. It's perfectly safe when contained within the animal's intestinal tract, but it can cause serious illness if it enters the food supply. An infection from salmonella can cause vomiting and diarrhea and be especially dangerous — even fatal — for the very old, the very young or those with compromised immune systems.

The most common sources of salmonella are alfalfa sprouts, peanut butter, chicken and eggs. In fact eggs have been found to be responsible for 77% of salmonella in the US. An egg can be contaminated with salmonella externally, if bacteria penetrate the eggshell, or internally, if the hen herself carries salmonella and the bacteria was transferred into the egg before the shell formed.

How eggs are handled, stored and cooked is essential for preventing salmonella from contaminated eggs. For example, storing eggs below 40°F halts the growth of salmonella, and cooking eggs to at least 160°F kills any bacteria that is present. While eggs aren't any different in the US or Mexico, the way they're treated for salmonella is. In the US, salmonella is mostly treated externally; before eggs are sold they go through a sterilization process. They are washed in hot, soapy water and sprayed with a disinfectant, killing any bacteria that might be on the shell. A handful of other countries, treat eggs the same way and this method is highly effective at killing the bacteria found on egg shells. Unfortunately, it does nothing to kill bacteria that may already be present inside the egg, which is often what makes people sick. The washing process may also remove the cuticle of the egg, which is a thin layer on the eggshell that helps protect it. If the cuticle is removed, any bacteria that come into contact with the egg after sterilization will more easily be able to penetrate the shell and contaminate the egg.

While refrigeration does not kill bacteria, it reduces the likelihood of you becoming sick because it keeps the number of bacteria that may be present limited.

However, there is another important reason that eggs are supposed to be kept in the refrigerator in the US. To keep bacteria to a minimum, the FDA requires commercially sold eggs to be stored and transported below 45°F, and once eggs have been refrigerated, they must always be kept refrigerated to prevent them from forming condensation if they warm up. The moisture makes it easier for bacteria to penetrate the eggshell.

Eggs don’t have to be refrigerated in Mexico, even though they experienced the same big epidemic of salmonella in the 1980s that freaked out Americans so much. While the US chose to control salmonella through washing eggs and refrigeration, many countries have chosen to improve sanitation and vaccinate hens against salmonella, preventing infection in the first place. Is Mexico doing that? Well, many, many eggs are the product of backyard projects and sold to nearby stores, so good luck with that.

When Mexicans don’t wash eggs, the egg cuticle and shell are left undamaged, functioning as a layer of defense against bacteria. In addition to the cuticle, egg whites also have natural defenses against bacteria, which can help protect the egg for up to three weeks. Because eggs in Mexico are treated differently than in the US, it's fine to keep eggs out of the refrigerator as long as you plan to use them soon, although refrigeration can double an egg's shelf life. While a fresh egg stored at room temperature will start to decline in quality after a few days and need to be used within one to three weeks, eggs kept in the refrigerator will maintain quality and freshness for at least twice as long.

I see we have one more chicken/egg question from the floor, you in the back, yes? Why are Mexican yolks more orange than US yolks, you ask?

You are what you eat, even if you are a chicken. Typically the orange yolk contains more vitamin A and beta carotene. The yolks become orange for a similar reason that carrots, also high in beta carotene, are orange. This color change and improved vitamin content is directly related to the quality of food the hen consumes, with chickens who are just tossed out into the yard consistently eating the highest quality of forage. The hens scratch for worms and bugs, while also eating vegetation, and grains. It’s considered by many to be the best diet for chickens. And makes the yolks orange.