Onions are a unique vegetable and
Onions are mildly spicy compared to other spices. However, the spiciness of onions depends on the type of onions and whether the onions are raw or cooked. The reason is that onions contain an enzyme, isoalliin, that quickly catalyzes the production of thio-compounds (thiosulfinates and thiosolfonates) within the onion to yield the spicy flavor.
Since onions are mildly spicy, it is crucial to understand how to preserve their subtle flavor by learning about the different factors and conditions affecting onion spiciness. So read on to know more!
Are All Onions Equally Spicy?
Not all onions are equally spicy. Essentially, the various types of onions differ in their level of spiciness. For example, red onions are the spiciest among all kinds of onions, noted for their intense, aromatic, and slightly peppery flavor in foods and when in contact with any parts of your body.
Red onions are most likely to make your eyes burn and tear when you cut them open because of their enzyme content and high concentration of sulphonamides. As a result, onions planted in high-sulfur-containing soils possess a more intense flavor.
Additionally, the onion’s time of the year or onion planting season affects their degree of spiciness. For example, onions planted in late Spring are less spicy than the others. In other words, certain factors influence the spiciness of onions. Here they are:
Factors Influencing the Degree of Onions’ Spiciness
- High soil Sulphur content
- Onion Planting season
- Onion physical state (raw or cooked)
- Onion color, etc.
Do Onion Planting Seasons Affect Their Spiciness?
Planting seasons lend different tastes, flavors, and colors to onions year-round. Due to seasonal differences, some onions can be sweet, spicy, mild, aromatic, red, white, or yellow.
Fun Fact: Seasonal differences among onion types are more noticeable in March because of the Fall/Winter transition to Spring/Summer of onions.
Below is a table highlighting basic facts about seasonal onions.
| Onion season | Availability | Onion characteristics | Flavor | Best utility |
| Spring/Summer | March-August | Thin skin Transparent layers Lighter color High water content Shorter shelf-life(30-60days) Easily bruised | Mild-Sweet | Raw Pickled Light cooking Grilling |
| Fall/winter | August-May | Thicker skin Paper-like layers Darker color Lower water content Longer shelf-life. | Mild-Spicy | Roasted Fried Long cooking Caramelizi-ng |
How Spicy Are the Spiciest Types of Onions?
Red onions are the spiciest types of onions, often described as having an aromatic or intense flavor due to their high content of thio-compounds. Their dark-purple coloration adds to their taste, causing them to permeate every food recipe. However, their spiciness is equally toned down when exposed to heat during cooking.
Understanding the science behind onion spiciness helps you decide what to use onions for, whether as part of your recipe or as a medicinal substance.
What Is the Science Behind Onion Spiciness?
You probably didn’t see this coming but believe it or not; there is a science and chemistry behind onion spiciness. The science of onion spiciness allows you to creatively manipulate onions for whatever you want without dealing with their intense flavor. It all starts from the raw onion state and their thiosulfinates.
Understanding the Chemistry of Onion Thiosulfinates
All members of the Allium species have sulfur, and onion is one of them. However, thiosulphinates are the critical compounds behind the spiciness— pungent, aromatic essence of onions. The thiosulphinate compounds are why your eyes burn and tear up when you cut an onion. They also give onions their taste/flavor, odor, and sometimes color.
Fun fact: Interestingly, the raw onions do not inherently contain thiosulphinate compounds. These compounds only form when you do damage to the onions—cutting!
The enzymes in the onions react with thiosulphinate precursor molecules to create the thio-compounds when you slice onions.
Are Onions Spicy Enough To Be Considered a Spice ?
Onions are spicy enough to be considered a spice because they possess the characteristic spicy, somewhat peppery, or hot flavor/feeling as other known spices like peppers, gingers, and garlic.
Your taste buds are not the only determinant of what should be considered a
Moreover, there is also the scientific or taxonomic classification and the general
Examples of spices belonging to the genius Allium include but are not limited to
- Onions
- Garlic
- Chives
- Leek
- Scallion, etc.
So scientifically, onions are
In addition, the general definition of spices by Merriam-Webster’s online dictionary is an aromatic vegetable or product used to season or flavor foods. So, from the dictionary standpoint, onions are spicy enough to be considered a
While there are varying degrees of spiciness, it is essential to know if all onion types have the same degree of spiciness and their related conditions.
How To Regulate the Spice Intensity of Onions
Suppose you do not appreciate the spiciness of onions; you can regulate the intense flavor to suit your preference by controlling the thiosulfinate compounds. Similarly, if you prefer to have higher concentrations of the onion flavor, it’s all within your control. Here is how:
To Get More Spicy Onions
If you are up for it, you can get more spicy onions by cutting and using them raw. Since the odor and flavor only form from fresh cutting, you’ll get a more intense spicy onion if you make more delicate, thinner slices. Moreover, the longer you leave the cut or sliced onions, the stronger the flavor.
To Get Less Spicy Onions
Getting less spicy and even sweeter onions is all about heat treatment. Cooking onions immediately after cutting prevents the enzymatic reaction and formation of the thiosulphinate compounds. Essentially, the longer you cook, the less spicy the onions.
The reason is that heat breaks down the enzyme before it can catalyze the reaction and release the thiosulphinate compounds responsible for onion pepperiness or spiciness.
You can regulate the degree of onion spiciness by subjecting it to varying degrees of temperature. For instance, you will get less spicy or pungent onions under low to medium heat and no onion flavor under high or prolonged heating.
Frequently Asked Questions
Are Onions Spicy or Sour?
Onions are spicy instead of sour due to their pungent rather than tart flavor. They also belong to the same
What Kind of Onion Is the Spiciest?
Red onions are the spiciest of all onion types, with a somewhat peppery feel added to their deep-purple color. They are readily available and are the most used types of onions for preparing most meals or as part of most recipes. Red onions are the sweetest between March and September.
Is Onion Powder Considered a Herb or Spice ?
Onion powder is considered a
Final Thoughts
The degree of onion spiciness rests on a delicate balance between the onion type and the processed state of the onions. However, since everyone’s
