Grim's Grub: Vegetable self-defense mechanism backfires when it comes to onions

A chemistry and history lesson in one!

Photo illustration, Shutterstock, Inc.

Human beings are an odd lot when it comes to plant self-defense strategies. Where some animals see painful or toxic consequences, we see delightful variety or a boastful challenge.

Mints become pungent to ward off rodents? Humans see a refreshing tea plant.

Peppers produce capsaicin to become inedible to pests? Humans breed them specifically to be even hotter so we can have bragging rights.

Onions develop fumes that create sulfenic acid in mucous membranes? Humans add them to everything!


Varieties of onions people use frequently to add flavor in food preparation. Photo illustration, Shutterstock, Inc.

This last one is the subject of today's recipes. Why? Because June 22 was National Onion Rings Day, that's why!

So, here's the gist. At some point the allium family, related to lilies, produced variants that were less favorable to some form of pest. The chemical that made these variants less popular among pests was so effective that for generation after generation, the ones with the most of this chemical in them had the biggest chance of reproduction.

This happened after animals consistently turned up their noses (likely literally) at them, further condensing the presence of that chemical.

Think of it like the Grimler family tree. If you trace it back generation by generation, you would likely find that at some point my relatives started to favor potential partners who had: A. broad shoulders; and B. alien-like skulls. If enough of these people pair up together you wind up with my siblings with large hat sizes and broad shoulders in spite of medium to short stature.

In onions, the chemical is an enzyme called Lachrymatory-factor synthase. This enzyme leaps into action in an oxidation reaction when cut or damaged. The more damage, the worse the reaction is.

The enzyme binds with amino acids to create sulfenic acid, which is unstable and breaks down into a chemical called syn-Propanethial-S-oxide, which irritates glands in your face. Hence, your eyes and nose become irritated.


Slicing an onion into rings. Photo illustration, Shutterstock, Inc.

Propanethial-oxide keeps us going back to onions as an omnipresent culinary necessity. This is the chemical responsible for the flavors we are after, the ones we find pleasant in spite of the plant's attempt at self-defense.

It is especially the chemical responsible for our love of onion rings and sauteed onions because once you add heat, the Propanethial-oxide degrades or decomposes into bispropenyl disulfide, which is less pungent and more sweet.

Without this, onions would just be another boring vegetable and so many dishes would be sadly lacking. Of course, that is especially true with onion-centric foods like onion rings, which have existed for perhaps longer than you might have expected.

Kirby's Pig Stand is just one of several U.S. restaurants that claim to have invented onion rings. Sliced and fried onion recipes go back at least as far as 1802. I think this recipe from "The Art of Cookery Made Easy and Refined" will really blow your minds when you ask, "Why don't we do that?"

Homemade deep-fried onion rings. Photo illustration, Shutterstock, Inc.

Onion Rings


From John Mollard's 1802 recipe book, "The Art of Cookery Made Easy and Refined"

  • 6 large white onions (I would reduce this to 3, and perhaps cut them one at a time to avoid waste)
  • 1 cup flour (approximately, do not mix it all in at once)
  • 2 ounces (1/4 cup) cream
  • 3 eggs
  • 1 box lard
  • Salt and pepper, to taste
  • 1/4 pound grated Parmesan cheese

Pare six large, mild onions and cut them into round slices half an inch thick. Then make a batter with flour, half a gill (2 ounces) cream, a little pepper, salt and three eggs. Beat for 10 minutes, after which add a quarter of a pound of Parmesan cheese grated fine and mixed well together, to which add the onions.
Have ready boiling lard (350 degrees recommended); then take the slices of onions out of the batter with a fork singly and fry them gently until done and of a nice brown color. Drain them dry, and serve them up placed around each other. Melt butter with a little mustard in it to be served in a sauce boat.

Mozarrella stuffed onion rings. Photo illustration, Shutterstock, Inc.

Mozzarella (or other cheese) Stuffed Onion Rings

  • 1 large white onion
  • 1-2 slices mozzarella cheese
  • 1 cup flour
  • 3 eggs
  • 1 cups bread crumbs
  • 1/4 cup grated Parmesan
  • Parsley flakes
  • Oil for frying

Slice the cheese into strips approximately 1/2-inch thick. Slice onion into 1/2-centimeter thick slices.
With each slice, separate the rings, keeping those rings together in a pile. Repeat until all the rings are separated. With each pile, separate the rings into twos based on size with one large ring on the outside and one ring small enough to leave space between them on the inside. (For example, the first largest ring followed by the third largest ring; the second largest ring followed by the fourth largest ring.)

Carefully fill the gap between the rings with cheese. Place them on a nonstick sheet and freeze for one hour.

In three bowls sort flour, eggs and a mixture of bread crumbs, Parmesan and parsley flakes. Heat oil over high heat for deep frying.


Dip the stuffed rings in the flour, egg, bread crumbs, egg and bread crumbs again before dropping them into the fryer. Do not over crowd them; do them in small groups. Fry them until golden brown. If you fry them too long the cheese may ooze out, so be careful.

Drain on paper towels and serve.


  • You may lightly score the rings around the outside to prevent the ring from coming out of the breading later by placing very small, shallow slits along the outside every inch or so. Experiment one at a time because if you overdo it, your rings won't stay together. Do not go all the way through or all the way around.
  • Soaking the rings in cold water and then drying them before battering can help to mellow the onion flavor if you want a milder, sweeter taste.
  • You can marinate your onion rings in hot sauce or other sauces the night before you batter and fry them for extra taste.
  • The center of onion rings can be stuffed with meats or other fillings.

Travis Grimler may be reached at 218-855-5853 or Follow him on Facebook and on Twitter at

Travis Grimler began work at the Echo Journal Jan. 2 of 2013 while the publication was still split in two as the Pine River Journal and Lake Country Echo. He is a full time reporter/photographer/videographer for the paper and operates primarily out of the northern stretch of the coverage area (Hackensack to Jenkins).
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