Onion FAQs | Oldershaw Group

Frequently Asked Questions

What are the benefits of eating onions?

Although all vegetables have important health giving properties, onions have more than most. Onions are high in vitamins and minerals and low in calories. They act as a powerful antioxidant due to their high concentration of Quercetin. This can help reduce cholesterol levels which may lower the risk of heart disease. Red onions in particular contain high levels of anthocyanins, the pigment that gives the onions their red colour. Studies show that consuming higher levels of anthocyanins have a reduced risk of heart disease.

The suphur compounds in onions and garlic have also shown to have cancer fighting properties. The flavanoids Quercitin and fisetin found in onions have been proven to inhibit tumour growth.

It's not just milk and dairy products that contribute to healthy bones. Studies show that consuming onions improves bone mineral density. Onions may also help prevent osteoporosis through reducing oxidative stress.

Onions have also been shown to have antibacterial properties, inhibiting the growth of harmful bacterial such as E. coli and S. aureos.

Finally, the consumption of onions helps people suffering from diabetes by controlling blood sugar. Sulfur compounds and quercetin found in onions possess antidiabetic properties.

So to answer the question, is eating onions good for you, the simple is answer is yes! Try and get them into as many meals as you can and live a long and healthy life.

What are the side effects of eating onions?

Onion Allergy
Some unfortunate people are allergic to onions. If you are, you may experience an itchy rash or itchy eyes when you come into contact with an onion. Although there are no serious allergic reactions reported, if you experience difficulty breathing,, swelling to the throat or severe redness to the skin, you should seek advice from your doctor.

Heartburn
If you regularly suffer from heartburn, eating raw onions can worsen your symptoms so they are best limited in your diet.

Wind
Onions contain fructose, a sugar which is not easily digested by the gut. Fructose will pass into the intestine to be broken down which in turn, for some people, can produce gas. Gas production can lead to abdominal bloat and increased flatulence.

Do onions burn fat?

Onions are a great source of soluble fibre. This makes them a powerful prebiotic food. Soluble fibre promotes a healthy gut and is crucial for belly fat loss.

How long have people eaten onion for?

Onions have been part of the human diet for over 7,000 years. Traces of onions have been discovered by archaeologists which date back to 5000 B.C.

Are onions safe for dogs?

Onions can weaken a dog's red blood cells, leading to anaemia. In severe cases, this could result in death. Symptoms of anaemia in your dog include weakness, vomiting, loss of appetite and breathlessness.

Can onions help you sleep?

Counting sheep not working for you? How about eating onions? Onions contain L-tryptophan, an amino acid which is a natural sedative. The effect of lowering the blood sugar levels, lowers your activity level, making onions great for insomnia.

Why do onions make you cry?

One of the most commonly asked questions of the humble onion. How can they be so good for us but also make us cry? Before they are cut or damaged in any way, onions are no more likely to make you cry than any other vegetable. However, once they are chopped and the cells are damaged, amino acid sulphoxides are released. Enzymes are released in your eyes do to your brain thinking your eyes are under attack. The enzymes react with the sulphoxides to form sulphonic acids. This in turn brings on the tears as your bodies natural defence to these compounds.

Do onions cure colds?

It's a popular misconception that placing a cut onion in your room will absorb the bacteria and viruses associated with the common cold. Unfortunately, it isn't scientifically possible for an onion to absorb germs from a person. In fact onions have antibacterial properties which even if it were possible, would make them a bad host for any cold causing nasties.

Are raw onions good for you?

Onions contain folic acid and fibre, helping your body make healthy new cells. Raw onions have a higher level of organic sulphur compounds but the health benefits are there whether eaten raw or cooked.

Do onions attract bacteria?

You will find many examples on the internet of cut onions being put in the bedroom while people sleep and them turning black by the morning, supposedly absorbing bacteria from an ill person while they sleep. This happens because the cells start to break down as soon as the onion is cut and eventually the onion will rot. It is not because it is absorbing bacteria.

How should I store onions?

Onions should be stored in a cool, dry, and well-ventilated place, such as a pantry or cupboard. Avoid storing onions in the refrigerator as it can make them go soft and damp. If you bought the onions in a plastic bag, do not store them in the bag. Onions like airflow around them. Keeping them confined to a plastic bag can lead to moisture build up inside the bag. This in turn can lead to mould growth.

How are onions graded and sorted before packing?

Onions go through a series of grading processes after harvest. They are first cleaned and dried, then passed over riddle beds or roller tables that sort them by size. Optical grading technology, including near-infrared (NIR) systems, can detect internal defects such as rot or discolouration that are invisible to the naked eye. Onions that meet the specification for size, shape, and quality are then packed to order.

What is the difference between white and brown onions?

White onions have a thinner, papery white skin and a much stronger, hotter flavour than brown onions. They are commonly used in Mexican cuisine, salsas, and dishes where a less pungent flavour is preferred. Brown onions have a more robust flavour, thicker outer skin, and are the standard all-purpose cooking onion used across most British and European cooking.

What causes the strong smell when cooking onions?

The smell comes from sulphur compounds released when onion cells are broken down by heat. These compounds evaporate during cooking and are particularly noticeable when onions are first added to a hot pan. As cooking continues, the sulphur compounds break down further and transform into sweeter-smelling compounds, which is why cooked onions smell markedly different from raw ones.

Can I grow my own onions from a shop-bought onion?

You can replant a sprouting onion and it will continue to grow greens, but it will not reliably produce a new full-sized onion bulb. For growing onions from scratch, it is better to use onion sets (small immature bulbs) or seed specifically sold for growing. Onion sets are the easiest method for home growers and are widely available from garden centres.

What is peeled garlic and how is it produced?

Peeled garlic is whole garlic cloves that have had their papery skin removed and are packed ready to use. The peeling process uses air or water pressure to remove the skins without damaging the cloves. It is popular with food manufacturers and food service operators who need convenience and speed in preparation without sacrificing quality.

What is the shelf life of a fresh onion?

A whole, unpeeled onion stored in a cool, dry and well-ventilated environment will typically last between four and eight weeks. Once cut, an onion should be wrapped and refrigerated and used within five to seven days. The shelf life reduces significantly in warm, humid conditions or if stored in sealed plastic packaging.

Why do some onions have brown rings inside?

Brown or discoloured internal rings are usually a sign of Fusarium basal rot or another fungal infection that develops in the field or during storage. The damage is often invisible externally, which is one of the key challenges in onion quality management. The affected tissue should be cut away and the rest of the onion is typically still usable if the browning is limited.

What is the difference between organic and conventional onions?

Organic onions are grown without synthetic pesticides, herbicides, or artificial fertilisers, under a certified organic system. Conventional onions can use approved crop protection products and fertilisers to maximise yield and reduce disease pressure. Both are subject to strict food safety standards. The flavour difference is minimal, though some consumers prefer organic for environmental or personal health reasons.

Where do UK onions come from?

The UK onion season typically runs from August through to April or May of the following year, with British-grown onions dominating supply through that period. The main growing regions are Lincolnshire, Norfolk, and the Fens. Outside the UK season, onions are imported from countries including Spain, Egypt and New Zealand, to maintain year-round availability.

Are onions safe for dogs or cats?

No. Onions are toxic to both dogs and cats. They contain compounds called thiosulfates that damage red blood cells and can cause haemolytic anaemia. This applies to raw, cooked, and powdered onions. Even small amounts consumed regularly can be harmful. If you suspect your pet has eaten onions, contact a vet promptly.

What is the best onion to use in a French onion soup?

Brown or yellow onions are the traditional choice for French onion soup. Their high sulphur content and natural sugars make them ideal for long, slow caramelisation, producing the deep, rich flavour the dish is known for. Using a mix of brown and a few shallots adds extra complexity to the base.

How do I know if an onion has gone bad?

Signs that an onion has gone bad include soft or mushy patches, dark spots, a slimy texture, or a noticeably unpleasant smell beyond the normal onion scent. A small amount of sprouting is fine and the onion is still usable. If the outer layers are damaged, peel them back and check whether the inner layers are still firm and healthy.

Why are onions sometimes sold in nets?

Net packaging allows air to circulate around the onions, which helps to keep them dry and extends their shelf life. Moisture is the main cause of onion deterioration, so ventilated packaging is preferable to sealed bags. Nets also allow consumers to see the product clearly before purchase.

What is a Supasweet onion?

Supasweet is a trademarked variety of sweet onion with a significantly lower pyruvate content than standard varieties, which is what gives most onions their pungent smell and taste. The result is a mild, sweet flavour that makes them pleasant to eat raw. They are grown in specific conditions that encourage high sugar levels and low sulphur uptake.

Can I freeze onions?

Yes, onions freeze well once chopped or sliced. Blanching is not necessary. Spread the pieces on a tray to freeze individually before transferring to a freezer bag, or simply freeze in portions ready for cooking. Frozen onions are best used in cooked dishes rather than eaten raw, as freezing softens their texture.

How do I caramelise onions properly?

Slice onions thinly and cook them slowly in butter or oil over a low heat, stirring occasionally. The process takes 30 to 45 minutes to do properly. The natural sugars in the onion break down and develop a deep golden-brown colour and a rich, sweet flavour. Rushing the process over high heat produces soft onions but not true caramelisation.

What is the difference between a pickling onion and a standard onion?

Pickling onions are small, pearl-like onions harvested young and before they fully mature. They have a crisp texture, a punchy flavour, and a thin skin that makes them ideal for preserving in vinegar. Standard onions are larger, more versatile, and used across a much wider range of cooking applications.

How do I stop my onions from sprouting?

Onions sprout when they are stored in warm or humid conditions. To slow sprouting, keep them in a cool, dark, well-ventilated spot and avoid storing them near potatoes, which release moisture and ethylene gas that accelerates sprouting. Sprouted onions are still safe to eat, though the flavour may be slightly more bitter.

What is an echalion?

An echalion, also known as a banana shallot, is an elongated variety of shallot that is larger and easier to peel than traditional round shallots. It has a mild, sweet flavour and is popular in restaurant kitchens and home cooking alike. Echalions are versatile and work well roasted whole, sliced into dressings, or caramelised.

What is a shallot and how does it differ from an onion?

Shallots are a member of the allium family, closely related to onions but with a distinctly milder, sweeter and more complex flavour. They grow in clusters of small bulbs rather than as single bulbs and have a finer texture, making them particularly well suited to dressings, sauces, and delicate dishes where a standard onion might be too overpowering.

Are onions good for you?

Yes. Onions are a rich source of vitamins C and B6, folate, potassium, and dietary fibre. They also contain quercetin, a powerful antioxidant, and compounds with anti-inflammatory and antibacterial properties. Regular consumption has been linked to improvements in heart health, blood sugar regulation, and immune function.

Can you eat onions raw?

Yes. Raw onions have a sharp, pungent flavour and are a great addition to salads, salsas, sandwiches and pickles. Red and white onions are the most commonly eaten raw. If you find the flavour too strong, soaking sliced onions in cold water for 10 to 15 minutes before eating will mellow them out significantly.

What is the difference between brown and red onions?

Brown onions are the most widely used variety and have a strong, pungent flavour that sweetens and deepens when cooked. They are ideal for soups, stews, roasting and frying. Red onions have a milder, slightly sweeter flavour and are often eaten raw in salads and sandwiches. They also hold their colour well when pickled.

Why do onions make you cry?

When you cut an onion, you break open its cells, releasing enzymes that react with naturally occurring compounds to produce a gas called syn-propanethial-S-oxide. This gas irritates the tear glands in your eyes, causing them to water. Chilling the onion before cutting can slow the reaction and reduce the effect.

How should I store onions at home?

Store onions in a cool, dry, well-ventilated place away from direct sunlight. A kitchen cupboard, pantry, or garage shelf works well. Avoid storing them in plastic bags as this traps moisture and causes them to rot faster. Whole onions can last several weeks when stored correctly.

Are onions toxic to dogs?

Yes, onions are toxic to dogs and should not be ingested. Onions contain a toxic principle known as N-propyl disulfide. This compound causes a breakdown of red blood cells, leading to anemia in dogs. The toxin causes oxidative damage to your dog's red blood cells by attaching to the oxygen molecules in those cells.

Can onions cause bad breath?

Yes, onions can cause bad breath. This is due to the sulphur compounds in onions, which are released when they are cut or eaten. To reduce onion breath, try chewing on fresh parsley or mint leaves, or drinking lemon water.

Do onions have health benefits?

Yes, onions are a nutritious vegetable that is high in vitamins C and B6, as well as antioxidants. They may also help to lower the risk of certain types of cancer and improve heart health.

How do I use onions in cooking?

Onions are a versatile ingredient that can be used in a wide variety of dishes, including soups, stews, casseroles, salads, and stir-fries. They can be sautéed, caramelised, roasted, or grilled.

How do I caramelise onions?

To caramelise onions, slice them thinly and cook them slowly in a pan with butter or oil over low heat until they turn a deep golden-brown colour. This process can take up to 45 minutes. Be careful not to burn them.

Can I freeze onions?

Yes, you can freeze onions. Simply chop the onions and place them in a freezer-safe container or bag. Frozen onions are great for adding to soups, stews, and casseroles.

Are there different types of onions?

Yes, there are many different types of onions, including red onions, brown onions, white onions, and sweet onions. Each variety has its own unique flavour and culinary use.

How do I cut onions without crying?

To reduce tears while cutting onions, try refrigerating the onion for 30 minutes before cutting, cutting the onion under running water, or using a sharp knife to make clean cuts. Alternatively, use Sunions, the tearless onion!

Can I eat onions raw?

Yes, you can eat onions raw. They can be sliced thinly and added to salads, sandwiches, or used as a garnish. Raw onions can also be pickled or used to make salsa.

How do I choose the best onions?

Look for onions that are firm and have dry, papery skins. Avoid onions that are soft, sprouting, or have signs of mould.

How should I store onions?

Onions should be stored in a cool, dry, and well-ventilated place, such as a pantry or cellar. Avoid storing onions in the refrigerator as it can make them go soft and damp. If you have bought the onions in a plastic bag, ensure you remove them from the bag to store them. Onions keep best with they are dry and well-ventilated so keeping them in plastic packaging can encourage mould as the onion respires and gives off moisture.