Topic: Know your Onions!

[SnS]

What makes an onion work?

Cut it, and it explodes with strong smells, hot flavours, and irritating vapours. But detonate the firepower, and it can be meek and mild - even sweet. The key is to understand an onion's structure.

With this knowledge, any cook can manipulate this versatile bulb to achieve pleasingly specific results.

Onion structure and onion chemistry

Onions come in many different colours and sizes, but all are the same species. The dry bulbs, the vegetable we're exploring here, are 89 percent water and 8 to 9 percent soluble sugars; the rest is minerals, fats, proteins, and sulphur compounds.

The sulphur compounds produce distinctive flavour and an aroma that can be difficult to disguise once you've eaten or touched onions. These oil-soluble compounds easily remain in the oils on your skin. They're also blood-soluble and so can be detected in breath and perspiration.

Some onion compounds do not form until you break cell membranes. As soon as a cell is broken, as by peeling, bruising, or cutting, a definite sequence of reactions follows. A key component is the enzyme alliinase. The degree to which this enzyme is activated affects the intensity of the response.

First, sulphur-containing compounds are produced; these are responsible for irritating vapours, one of which stimulates a tear response, and for a biting astringency. These compounds quickly break down into others, which ultimately yield the onion flavour and aroma. In raw or partially cooked onions, these compounds mask sugars and dominate taste.

How to control onion behaviour

Cutting or breaking the cell membranes develops compounds associated with flavour, aroma, and bitterness. With more disruption, more of these compounds, including lachrymator (tear producer), will be formed. To minimize this effect, peel onions under running water so you rinse away vapours and lachrymator as they are created. Chilling onions before you cut also slows the release of tear producer.

When you chop onions in a food processor, more cells are bruised than when you mince onions by hand--so the flavour is stronger and more bitter.

Cooking time and heat intensity both affect flavour. A short period of high heat brings out strong onion characteristics more quickly. But long cooking over low heat diminishes the strong taste, enhancing the onion's natural sweetness.

Using too high a temperature for too long a time develops bitterness, which is somewhat different from a burnt flavour.

Saute: most flavour (not hot)

Sauteing or stir-frying cut onion over medium-high heat brings out the most flavour. The high temperature volatilizes the first set of compounds, this speeds production of other compounds associated with onion flavour and aroma. Sugars in the onion caramelize, which lends colour and flavour to sauces and stocks.

Slow-cook: sweet, mild, limp

Slow-cook sliced onions in oil over moderate heat until they become very limp and golden. Slicing brings forth flavour components; long gentle cooking dissipates them, unmasking natural sweetness. Some of the soluble onion sugars caramelize during cooking, deepening and enriching flavour.

Whole: mellow and mild

If onion is cooked uncut, hot flavour from its enzyme, alliinase, never develops; you get only mild onion flavour with slight sweetness.

Boil whole: sweet, mild

When small, whole, peeled onions are boiled in water, the onion produces a compound much sweeter than sugar. As with baked whole onions, alliinase's hot flavour doesn't develop.

Deep-fry: crisp, sweet, golden

Cut onion into thin shreds, lightly dust with flour, and fry in a generous amount of oil. The large surface area exposes sulphur compounds. The hot oil drives off many of them and much of the onion's moisture, leaving crisp sweet shreds.

Now you all know about onions!

SnS  ;D

[Domi]

Adding a little salt to your chopped onion will also cut down on the bitterness as it releases the natural sugars.

[haldi]

Thanks Sns
That explains why any recipe using fried pureed raw onions, tastes so bitter
I have a Pat Chapman recipe using it (I think it was CTM from his first restaurant cookbook)
I thought I did something wrong, but I guess the recipe could never have gone right

Adding a little salt to your chopped onion will also cut down on the bitterness as it releases the natural sugars.

Hi Domi
        I noticed how salt affected the sweetness of a base I was cooking
It was one of those "experimental curry base days"
The second base version I made that day,used double the salt
It didn't turn out saltier, just loads sweeter
It does seem strange, doesn't it?

[SnS]

Some interesting reading about onions on this forum here

http://forums.egullet.org/index.php?showtopic=75013

SnS  ;D

[Bobby Bhuna]

Great post SnS - thanks! ;D

[ast]

Thanks for the info SnS!  Great stuff! ;D

[Domi]

Has anyone tried sprinkling their uncooked onion with a quarter teaspoon of asafoetida before frying? I add asafoetida to all my dishes and I think this is the best way to fully make use of the spice, I've added it in the spice mix and after cooking the onion but I really do think it makes more of a difference when added to the onion before it's cooked...

or am I just kidding meself that it works better?

[SnS]

Hi Domi

I always thought Asafoetida was used instead of onion, but I guess if you use them both together that's gonna create one hell of an onion taste. ;D

[Domi]

Hi Domi

I guess if you use them both together that's gonna create one hell of an onion taste. ;D

No it doesn't SnS, if anything it makes the fried onion taste more mellow, deeper, or more rounded....I only ever use a quarter teaspoon (or thereabouts) not enough to overpower it in any way, it just enhances the flavour. By the way, asafoetida does stink, but once it hits the onion the farty smell disappears instantly and can't be smelt during the cooking process either. Asafoetida (the plant, not the dried spice) is used as a substitute for onion and garlic, which is why I think it really enhances the flavour....it's a natural marriage for me.

More info on asafoetida:

http://www.macasafoetida.com/infozone.asp

[hidden]

Can anyone tell me some nice herbs or spices I could add while frying my onions to make a chicken tikka have a more flavourful taste? Lately I have found that something is missing.

Also thanks for all this useful infomation on onions it will help me in later dishes.