Normally I put onions on a low heat and slowly cook them for an hour or more to get them into that sticky syrup like consistancy.

However with the cost of electric and gas going through the roof I wondered if there is another way ? Can you put the heat up full and stir like mad? or can you seal them with a lid and allow the steam to help but not have it to high so they burn ?.....

how do you all do yours?

Steve

I was thinking just thinking this the other day when I started on a marathon French Onion Soup session!

For that a spoonful of sugar does the trick, in fact you need to be extra careful due to the extra heat generated that the onions don't burn too quickly!

For curries a teaspoon of salt could help by dehydrating the onions so they cook quickly. I would not put a lid on as the onions would end up steaming in their juices rather than frying.

Can't see any reason though for cooking as many onions as possible in a large pan and putting some in the 'fridge or freezer for another day?

Also any views on the best cooking method i.e. butter/ghee or what type of oil or mixture of?

Adding a tiny amount of sugar, just like in French Onion Soup, does work well. I have not tried adding salt. I am cooking a few things today that require browning onions and will give it a try.

Mamta

I did an experiment once when I heated some diced onion in oil, noting the temperature of the oil and the weight loss of the onion/oil mix, over time. I found the onions lost weight linearly with time, up to the point where they were nearly totally dehydrated (over an hours cooking time), that the temperature of the oil did not rise significantly above 100?C for most of that time, and the only burnt bits of onion I observed were those out of the oil.

My suggestions, based on these observations is that you heat your onions (small dice would be best, unless your recipe says otherwise) in a shallow pan, and let the steam escape, unhindered, without a cover. I would not add sugar (but this is a personal preference) or salt (which hinders the browning of food in general), it will not draw water out of cooking onions, though it may do so from raw onions, so you could try that first, then wash the salt off before frying.

I don't know why you are frying the onions, if it is for the start of a curry, then they don't need to be too brown, just golden, about twenty minutes on medium heat.

Hi,

If I can give a bit of a scientific gloss to what happens when you heat onions in fat. At first, the onions' cell structure begins to break down releasing water, and allowing them to become soft. If you heat very gently, the moisture stays around the onion and as their cell structure breaks down further, you get a sloppy sort of mess. If you heat fiercely right from the beginning, but without a large excess of oil, the water released from the onions evaporates relatively quickly and doesn't build up round them. However the breakdown of the cell structure doesn't take place much more quickly and the cells continue to give out water.

Either way, gentle or fierce, the temperature of the onion mass will be almost exactly that of the boiling point of water, as it takes so much more heat to evaporate water than it does to increase the temperature of the mass. Eventually all the water contained in in the onion will have gone, the temperature will start to rise. If you had cooked your onions very slowly at first, the breakdown will happen more or less evenly throughout the mass, and the onion mass will dry out more or less evenly whether you stir or not. If you try to heat fiercely without stirring what happens is that the onion at the bottom will have lost their water, and therefore the temperature will rise but just where the onions are touching. Above you will have relatively cool, water containing onions at 100C. If on the other hand you stir all the time, the fact that the heat is on higher, will make the water evaporate quicker, which is why they can take colour quicker.

Anyway, the colour comes from the sugars in the onions caramelising, and the reason this happens more quickly and more easily is simply because there's more free sugar present.

It's true that salt does tend to stop meat browning evenly. By sucking moisture to the surface of meats it can tend to cause the meat fo keep cooler because it's taking heat to evaporate moisture from the surface, and as it's not warming up so hot in some places, it's not browning there. However on onions, salt has no such effect. If anything it will encourage the moisture to escape from the cells, and make it less necessary to stir during the earlier stages.

The only way that onions will start to brown while still containing quite a lot of water, is if they are heated so fast that the outside of the onion can crust up before the centre of the onion bits has broken down. This can be encouraged by using large pieces of onion. Stir frying in commercial Chinese kitchens id a good example. Alternatively, deep frying onion rings can have the same effect. In both cases the rate at which heat can reach the outside of the bits of onion is greater than the cooling effect of the evaporation of water coming from cell breakdown.

Hope that explains some of the physical chemistry behind our good old browned onions.

All the Best

Ian

Thanks everyone, that's helped clear it up now !...

Steve