Onions contain a variety of acids, but the most prominent ones differ depending on the context of the question. Let's clarify:
1. The Acid that Makes You Cry: Sulfenic Acid
When you cut an onion, its cells release sulfenic acid. This unstable acid quickly breaks down into a volatile gas, which irritates your eyes, causing them to water. This gas eventually reacts with water in your eyes to form a dilute solution of sulfuric acid, further contributing to the irritation. Multiple sources confirm this process: Why do we get tears when we cut onion? - Quora, Why does cutting onions make our eyes tear? : Central Customs ..., Just Ask: Why Do Onions Make Us Cry? | PBS News, and What are the chemicals in onions that make your eyes water when ....
2. Predominant Organic Acids: Glutamic, Citric, and Malic Acids
Research indicates that the major organic acids in onions are glutamic acid, followed by citric acid and malic acid. This information comes from several studies, including Organic Acid Contents in Onion Cultivars (Allium cepa L.) | Journal ... and Organic Acid Contents in Onion Cultivars (Allium cepa L.) | Request .... These acids contribute to the onion's overall flavor profile.
In short, while sulfenic acid is responsible for the eye-watering effect, the dominant organic acids impacting the taste are glutamic, citric, and malic acids.
