Forget The Eggs, Mashed Potatoes Are The Perfect Way To Bind Meatballs
When you bite into a meatball, you're able to taste more than just meat. It'll differ depending on what ingredients you actually added, but in Italian-style meatballs, usually the flavors of parsley, garlic, and onion are the most prominent ones outside of the meat. You may even be able to taste the bread crumbs if you used the seasoned kind. As for the eggs however, the flavor is virtually unnoticeable in a meatball.
It's no secret that eggs contribute hardly any taste to meatballs, however, they are essential to the texture. Eggs prevent meatballs from falling apart when they cook by acting as a kind of glue to bind together the other ingredients. This is what ultimately gives meatballs their signature consistency, but eggs aren't the only ingredient that can accomplish this. Mashed potatoes can also act as a binder in meatballs, and are perhaps even more effective at preventing them from becoming tough and crumbly.
Why mashed potatoes work better than eggs in meatballs
Eggs may be the traditional binding agent in meatballs, but they're actually not the most foolproof. When eggs cook they get spongy, and while some egg is beneficial to the texture of meatballs, you can easily add too much. If you do, the sponginess of the eggs will cause the meatballs to get waterlogged, and that means they'll be soggy, not juicy.
Mayonnaise and yogurt are some of the most popular egg substitutions for meatballs, but while they are effective at binding the other ingredients together, they risk adding too much moisture, and too much moisture is precisely how you end up with meatballs that are mushy.
That's why mashed potatoes are the ideal option. They aren't liquidy like mayo or yogurt so there's less risk of mushiness, and if you were to add too much, they wouldn't adopt a spongy texture when the meatballs cooked.
How much mashed potatoes should you add to meatballs?
When you use mashed potatoes as the binder in your meatballs, the ratios of the ingredients aren't much different than when you use eggs. One egg can simply be substituted for ¼ cup of mashed potatoes. You may be tempted to add butter or milk to your mashed potatoes like you would if you were serving them as a side dish, but for best results you should consider leaving them plain.
Any type of potato can realistically work, but russet and Yukon gold potatoes are ideal for meatballs because of their neutral flavor and higher starch content, which also helps with binding. You can also use instant mashed potatoes, but you'll need to substitute out both the egg and the breadcrumbs, ¾ cup per pound of beef. Just make sure you are not adding the potato flakes in dry, and you won't need to add any eggs.