About Onions

This week’s lesson: Onions!

Onions belong to the lily family, and have been used for food and medicine for thousands of years. They are a very popular crop among gardeners, because they can be stored for a long time after harvesting. Plus, there are over 300 varieties in different colors, shapes, and flavors, so it is fun to experiment with them and find your favorites. Red and white bulb onions tend to be sweeter than the more pungent yellow ones. Green onions (also called “scallions”) are just the young shoots of these bulb onions, harvested before the bulbs mature, and they have a milder onion flavor.

How do you know when they are ready to harvest? 
The size of the mature onion bulb is dependent on the number and size of the tops. For each leaf, there will be a ring of onion; the larger the leaf, the larger the ring will be. When onions start to mature, the tops become yellow and begin to fall over. At that point, bend the tops down or even stomp on them to speed the final ripening process. Loosen the soil to encourage drying, and after a few days, turn them up and let them dry out on the ground. Always handle them very carefully — the slightest bruise will encourage rot to set in. When tops are brown, pull the onions and spread them out on an open screen or netting, off the ground, to allow air to circulate on all sides. Allow onions to dry for several weeks before storing them. Drying them is important, as it prevents rotting and mold growth, and allows you to keep them for much longer periods of time.

How do you store them?
Once dried, bulb onions will store for several months in a cool, dry ventilated place (40 to 50 degrees F) with the stems braided or broken off. Note: Don’t store the mature, dry skinned onions next to apples or potatoes, because it will cause them to spoil. Once onions are cut, store them in the fridge tightly wrapped in plastic, or in a sealed container, so that they don’t transfer their flavor to other foods. Scallions can be stored in the fridge, unwashed, wrapped in a damp cloth and placed in a sealed plastic bag. They will last for about 1 week this way.

How do you cook them?
It is no secret that cutting onions can make you all teary-eyed, but don’t let your emotions take over, it’s just the sulphuric compounds in the onion playing tricks on you. To reduce eye irritation, try chilling onions for 30 minutes before cutting, or leave the root on, as the root contains the largest amount of sulphuric compounds. Always remove the dry outer skin before cutting, and cut the root off last, just prior to cooking or eating. Whatever you do, don’t waste your money on things like onion goggles- it might cause your friends to cry from laughter.

Onions are extremely versatile, and can be eaten raw in salads, on top of sandwiches, or cooked almost any way imaginable. The longer onions cook, the sweeter they become. To caramelize onions, slice them thinly and cook them in a pan on low heat with butter, stirring often until onions are browned. Green onions (scallions) are a great garnish, and are commonly paired with potatoes, or used in Asian cuisine.


When it comes to nutrition, variety is key, and when it comes to variety and vegetables, onions come to mind. The variety of colors and flavors correlate with the variety of nutrients found in this versatile and aromatic vegetable. Red onions contain the carotenoid, lycopene, which supports heart health, immunity, and may reduce cancer risk. Allicin, a compound found in white onions and garlic has also been found to promote heart health and reduce cancer risk. Green onions contain a considerable amount of vitamin K, a nutrient that may help prevent bone loss. Another important component of onions is inulin which belongs to a class of dietary fibers called fructans. Inulin acts as a prebiotic, providing energy for the healthy bacteria found in our gut. Prebiotic-rich foods like onions, together with probiotics found in yogurt and supplements indirectly promote immunity by supporting gut health. So next time you think of onions, don’t cry! Think nutrition!

Emily Berg MS, RD, LDN
Swedish Covenant Hospital Clinical Dietitian


Making onion jam is a great way to use up an excess of onions and extend their shelf life even longer. Onion jam is delicious on sandwiches, paired with cheese, served atop grilled meat, or spread on pizza as a tasty alternative to pizza sauce.

Caramelized onion jam
Makes about 2½ cups

3 tablespoons olive oil
4 pounds onions, halved and sliced through root end into ¼-inch-thick pieces
Salt and pepper
¾ cup ruby port (can substitute any wine)
½ cup water
⅓ cup sugar
¼ cup white wine vinegar (can substitute any vinegar)
2 teaspoons minced fresh thyme

Adjust oven rack to lower-middle position and heat oven to 400 degrees. Coat inside of Dutch oven with vegetable oil spray. Heat oil in prepared Dutch oven over medium heat until shimmering. Stir in onions and 1 teaspoon salt. Cover, place pot in oven, and cook for 1 hour. (The onions will be moist and slightly reduced in volume.)

Remove pot from oven and stir onions, scraping bottom and sides of pot. Return pot to oven, partially covered, and continue to cook, until onions are deep golden brown, 1½ to 1¾ hours, stirring onions and scraping bottom and sides of pot every 30 minutes. Transfer onions to cutting board, let cool slightly, and then chop into rough 1-inch pieces.

Transfer chopped onions to large saucepan, stir in port, water, sugar, vinegar, and thyme and bring to simmer over medium heat. Cook until liquid is reduced and rubber spatula or wooden spoon leaves distinct trail when dragged across bottom of saucepan, 8 to 10 minutes. Season with salt and pepper to taste.

Transfer jam to jar with tight-fitting lid, let cool to room temperature, then cover and refrigerate. Jam can be refrigerated for up to 2 weeks. Bring to room temperature before using.

Recipe source: America’s Test Kitchen