How come cookies don't have to be refrigerated if they're made of eggs?

I just baked some cookies, and amongst the ingredients were 4 eggs. Now, I would never leave a meal of scrambled eggs at room temperature for more than a few hours, so how come my cookies can be left at room temperature for days and days without going bad?

I assume it’s because of the various things mixed with the eggs. Scrambled eggs are just a pile of protein, compared to a far less concentrated dose in the cookies.

Did I mention that was a huge WAG?

Not to mention that cookies are baked at a much higher temperature than scrambled eggs. That probably has the greatest effect.

Bacteria need moisture in order to survive and reproduce. Thus, they thrive in foods with high-moisture content, such as eggs or starchy, egg-rich foods. If salmonella is what you are worried about, cooking eggs until the whites are solid should kill any harmful bacteria. I would expect that 8-10 minutes in a 450° cookie oven would do that as well.

And if I remember correctly, an entire batch of cookies (est. 6 dozen) requires only one or two eggs. That means the egg is pretty well diffused through out the batter and will cook all the faster.

As for cooked scrambled eggs that have been left out at room temperature, they’ll probably allow bacteria to set up house after a few hours due to the high moisture content.

I Remeber hearing somewhere that if you cook something long enough, the bacteria gets cooked out. I guess thats why you aren’t suppoesed to eat cookie dough

Also, sugar has preservative properties, which is why you can make jam and jelly and keep it for months without refrigeration.

I’ll go with the “sugar acts as a preservative” WAG.

From Indiana Sugars

After preview, I see DDG has beaten me to it - but that’s the way the cookie crumbles!

It’s odd to me that sugar would act as a preservative. You would think bacteria would find something with sugar to be extra tasty!

Yes, but . . . you have to first sterilize the preserves and everything they come in contact with or else you will definitely get spoilage. Least that’s what I assume that blue fuzzy stuff was on the top of the jam whose sealer didn’t quite take!


Sugar acts as a preservative by reducing the availability of water to microorganisms. The effect is measured as a decrease in the “activity” of the water found in a foodstuff. Here is a brief primer on water activity. The activity of water ranges from 1 for pure water to 0 for a dried out chunk of rock. A water activity of below 0.8 prevents the growth of bacteria and even most molds. As this table of the water activity of various foods shows, cookies, with an activity of 0.3 are far to dry to spoil, even if they do contain eggs.
In the case of the cookie, it is not just the sugar that helps preserve it. The oil, flour, salt, and fat all contribute to the low activity of the water that remains after cooking.