If you’re A COOK, you likely already realize: Onions are key to nearly all savory food. But cooking with onions (or rather, with each kind of onion) is limited if you treat them all alike… Selecting whichever one happens by.
Different varieties of onion has unique profiles of chemical compounds, making some bulbs ideal for particular uses and other ones no good at all. These distinctions is visually apparent in the chart above. That means you won’t need to understand advanced chemistry to know which bulb goes into what bowl.
How to Use Different Onions
For example, yellow onions are your go-to onion; they are the ones you’d cook down in stews, soups, and stocks. They’re hearty workhorse. Their strong flavor comes from high levels of sulfur, which kicks up a bit of bite (the bite subsides when cooked). This makes them extra savory, creating a rich foundation that no other variety can quite provide.
Yellow onions are perfect for long-cooked dishes, the infographic points out, but too harsh for uncooked salads. Why? Because although those sulfur compounds provides depth to a dish like a stew, they’re also what make an onion harsher on, say, a sandwich. When eaten raw, you don’t want that sharpness to overpower anything, it needs to melt away.
Then there is the sweet onion: low in sulfur, high in sweetness. Great for pickling and eating raw, slice up some sweet onion into your salad or on your burger, and enjoy a mellow, juicy crunch without any aggressive bite.
But try using sweet onions to make a stock, and they quickly cook down, lacking the strong savory backbone that makes other onions so good at building up a flavorful soup base. So for all their merits when eaten raw, sweet onions does not make sense for long simmering stocks. If you’re wondering what kind of onion is best for each application, the visual guide help you easily see where sweet onions fit.
Then there are the specialists. Small as they may be, shallots makes excellent additions to pan sauces and vinaigrettes. They are subtle and sweet with enough onion-y backbone to support all those other flavors without stealing the show.
Red onions have great texture (crunchy), good color (vibrant) and really stand up to being chopped and tossed into salsas and salads. The book’s guide says it is best to avoid using red onions when making stock because they will bleed purple pigments in clear broths.
For Mexican cooking, white onions are the go-to. They give a clean, sharp bite that pairs perfectly with the richness of meats in dishes like fajitas without dominating any spice.
Storage is also important. Contrary to intuition: Storing entire bulbs in the fridge will shorten their lifespan and soften their skin. Ideally, treat them like you would potatoes: Store them in a cool, dark, dry place. To minimize gas release and avoid stinging eyes, save the root end for last when it’s time to cut things up.
Timing also plays a crucial role in how to caramelize yellow onions. Onions are sliced and sautéed at low heat for roughly one hour, transforming from clear slices into sweet, jammy brown gold. If you rush things and turn up the heat, you’ll burn off those sugars before they has a chance to develop. That’s when you end up with bitter scraps different than a sweet condiment. To remind yourself that patience is the key ingredient, use the timeline in the graphic above.
Luckily, some savvy substitutes exist if you’re out of one or another variety. Soaking a yellow onion in cold water will give it that same sweetness as a sweet onion. Minced yellow onion and a splash of vinegar will have the same sharp bite than a shallot. The point is, use what you got without sacrificing taste.
That’s why knowing these details makes your food go from good to great. Match the onion to the task, honor the ingredient, and improve the finished product. It all begins by selecting the right bulb for the plate.