Cooking Onions: Newsletter Challenge (09/02/08)

I do not agree with you and GA given to you.

The thread says, onions are put after water is boiled. If onions are put after water boils, due to mass of onion, the water temperature drops down suddenly depending upon the quantity of onions.

If we assume that onion cooks at 100 deg C, we need to bring the water again to boil and then follow all methods you suggested.... putting of flame, Closing lid , insulating etc. (I am not sure at what temperature onion cooks)

By the way flamed onion (burnt) is sweeter than cooked one. I really love it.

Hi Just an Engineer

I gave you a GA because I mostly agree with your methods.

Because onions have a high water content, dropping them into boiling water will have only a momentary effect on the water temperature (unless they're frozen) and turning off the heat and covering the pot with a lid will provide more than enough residual heat to cook the onions to a level that would be acceptable in just a few minutes.

However, I Must say that Boiling onions is probably the most Horrible thing you can do to an onion. You've got to really Hate onions to abuse them in that fashion.

I happen to LOVE onions and would never beat them up in such a manner.

My God, the Inhumanity!!

Whereas most recipes call for about an hour of boiling untill the onions are cooked, I should think that after even an half of an hour [due to ambient heat loss] water will actually be leeching heat from the onion. So;

There fore, while i agree with you that the proper time for boiling onions is defined by a positive number less than zero, I'm afraid it rather cheats the question element "You want to cook some onions."

Also, the answer you reply to from "just a Camper" [to which you gave a GA] should have rather gotten an OT as it doesn't even address the question except in so far has how to defeat it [and yet it has 4 GA's so far.....]

Sorry for the delay in replying...haven't really been paying attention.

.... At this point, you want to conserve as much energy as possible. What should you do? Should you increase the heat so the onions will cook in less time? Explain.

I read the question as asking what you should do to conserve as much energy as possible yet still cook the onions. Increasing the heat is one Option, but is it the Right one? Of course not! Increasing the heat will not cook the onions any faster or decrease the amount of energy necessary to cook them.

I gave Just an Engineer (1) GA because his answer defined an Option for a Standard Method of cookery that is widely used and will Cook the onions using the least amount of energy. I can attest to the fact that this method works well and with items Much harder to cook than onions.

Whereas most recipes call for about an hour of boiling untill the onions are cooked,....

I guess it depends on where you're located....but I can tell you that I've never, in 45 years of cooking, cooked an onion that I wanted to eat, using Any method, longer than 30 minutes with the exception of creating a stock. Then you usually throw the vegetables out because they've "given their all" and are reduced to tasteless mush.

while i agree with you that the proper time for boiling onions is defined by a positive number less than zero,....

???....do you mean Greater than zero? Agreed! But not an hour or even 30 minutes.

Well, I am certainly no expert in boiling onions but one thing I do know is that when water is boiling at sea level, it is at approx 100 degrees centigrade - full stop.

Increasing heat energy at this point only serves to boil off the water faster, it does not increase the temperature of the boiling water and hence cannot decrease cooking time.

My advice is to cover the pot and reduce heat energy to allow simmering for the required cooking time.

I think this is also the advice in most recipe books for anything which requires boiling.

Increasing heat energy at this point only serves to boil off the water faster

Exactly.

To be a little bit whimsical, there is nevertheless a practical issue I have faced while cooking: I noticed that a vigorous boiling cause some types of food (e.g. beens) to get tossed around and consequently boil more evenly. Instead, by choosing to simmer it at low heat, I run the risk to get it burned at the bottom and leave it uncooked at the top! Anyway, I bet this is irrelevant when boiling an onion.

Quite relevant. Vigorous boiling will provide stirring but it will not cook the onions ant faster.

It is always advisable to ensure that there is no direct contact with the hot surface of the pot and so the use of heavy bottomed or copper covered pots which distribute the heat. where starchy materials are concerned they are such poor conductors that they allow the heat to build up so as to cause burning. A proper heating system would keep a temperature difference between the contents of the pot and the source - we need a computerised pot. This would i think be a Δt pot. Here is an opportunity for some one.

If the steam and water are at different temperatures, a vigorous boil will tumble them around and cook them quicker. The question is then whether energy is saved by a vigorous boil and a quicker cooking time. Or a low simmer and longer time. 'Cooked' is in itself a debatable term - fish can be 'cooked' cold in acidic juice. Most people have there own definition of when a steak is 'cooked', so why not the same with onions. For my 2 cents, they'e better caramalized, raw, or pickled (like this question).

If the water returns to the boil shortly after the onions are put in it, can the water get hotter ? Maybe onions float and making the water boil more furiously will ensure the exposed floating part gets turned around/splashed/steamed. Boiled onions sounds gross, but there is a specific type called a "boiling onion" often dropped into stews etc. According to thisarticle, the onions only need 3 minutes boiling, so I'd just put a lid on the pot and turn off the heat when steam started escaping.

Can I opt to use less water? Start with only a small amount in the bottom of the pan thus using less energy to get it to boiling point and at the same time steaming the onions above the water! I don't know what sounds worse, boiled or steamed onions!

If I can't do that because of the rules and regs then can I shred the onions so that the heat available will be in contact with more surface area of the said onions? What ever method, keep the lid on, turn the heat off and insulate the pot!

In all honesty, I'm a bad cook so I will ask the girlfriend later!

Why add the onions once the water is boiling - I've never noticed any disadvantage in cooking from cold? Of course you should maximise the transfer efficiency (method depends on heat source), and minimise the thermal capacity of the pan and the amount of water you use, minimise the venting (not zero, unless you have a pressure cooker - but that seems to be a sure way to wreck the onions themselves), and adopt Just_an_engineer's "wrap it up" approach if you are serious.

Apart from that, there is doubtless an optimum rate to add the heat - too fast and much is wasted by hot air* going up the side of the pan, too slow and much is wasted through evaporation. This will of course depend on the heat source - and maybe individual experimentation will waste more heat than can possibly be saved, so a guessed compromise should be acceptable (taking slightly too long than optimum probably wastes less heat than the same time-amount faster).

As to boiled onions being gross - they are delicious provided that you leave just a little crunchiness. If perchance you overcook them, they are still good in soup (though not as sweet as they would be if you browned them first).

*Remind you of something?

And serve them with a nice cream sauce or hollendaise.

After you drop the onions into the water it will either stop boiling or slow down. After a little while the water will resume boiling or speed up a bit - this is after the onions have come up to the water temperature. If you want to save as much energy as possible cover the pot and reduce the heat so that the water boils s l o w l y. Since you cannot heat the water above the boiling point it makes no sense to turn up the heat. Ed

I stick the onions with just a little water or butter in a bowl and microwave them for about 3 to4 minuites to soften them. When they get soft they release the sugars trapped in the cells and mmmm they are so good on foods or alone.

Espically those big sweet onions from Georgia called Valdialia Onions mmm good.

These are sliced onions now not whole.

Baby stuff but often a subject misunderstood. The water will remain at 100º unless you add some salt to elevate it. Providing you put a lid on then the steam in the kettle would also be at 100º. Same temperature - same time needed.

If pressure is increased then temperature will increase.

The pot will radiate heat (the higher the temp the faster) so heat input will need to equal this. To save energy - use less water as it will take less time to reach boiling point (waterless cooking) or use a pressure cooker - again less water is required but also less time and so less heating.

I find a common problem in industry is that people equate heat with temperature and do not realise that it is calories that count and so the quantity of heated substance must also be taken in to account.

Hazman said

The water will remain at 100º unless you add some salt to elevate it.

I say

The small amount of salt you add will have little if any effect on the boiling point of water. This is a big misconception - the salt in cooking is added for seasoning.

The effect might be negligible but you cannot ignore science - check out

http://en.wikipedia.org/wiki/Boiling-point_elevation

you might like to check out depression of freezing point while you are at it.

Adding salt to the water might add flavour to the eater and onto but not into the onion. IN fact due to Osmosis water might be extracted from the onion - it moves from lower concentration to higher. Any change in the onion will be heat induced.

The question of adding food to water to boiling water is another good one. Temperature differentials affect the heat transfer and change of state will depend upon this. The center of small onions will get to temperature faster than that of larger ones. I doubt that in this case it makes much difference.

In the case of boiling eggs the state of change is such that for a set time you will get a runnier yolk if the egg is put into boiling water as the albumen will solidify faster and become a poorer heat transfer agent. Perhaps the question of whether you put the egg in cold water or boiling water and for how long to get a soft boiled result needs experimentation. I think the possible cracking of the egg when it goes in to boiling water might be a bigger problem.

Other than for making onion soup, I've never cooked onions like this. so this is a guess. First, I'd bring the water around the onions back to a light boil without changing anything. Next, I'd cover the pot and bring the burner temp down to simmer. This will maintain the pot heat and continue to allow the onions to come to the water temp and cook in a light boil, but not burn on the hot pot bottom.

But really what I would like to do is give them a little stir and then rinse them out in cold water and call that a cleaning process. Then cut them up and do them in a pan with oil until golden, seasoning them as I go, and adding the food they are supposed to go with when they are done properly. Or, cut them in halves and quarters and place them around the roast before sealing it up and roasting it in the oven. Or cut them into slices and accross the slices into bits and add them to hamburger meat to make patties with.

Boiled onions? Sounds British. I mean anybody who can eat chip buttees has got to have boiled onions in their diets somewhere!

Urnch!

Mark

Not that I am a great fan and do like them fried but actually served with a white sauce they can be very nice. Stews, broths and soups also benefit from th onions which are only boiled.

In the case of French Onion Soup I find this has the best of both worlds and the onions are browned (fried) before being boiled.

Nothing wrong with chip butties Being of British blood, I am a firm believer of pickling onions and not boiling them! Look to the Germans for boiling onions! They can't get enough of them!

Dear Dear Racism in a small form, and coming from a canadian! Johnny Canuck would be horrified, boiled onions are the basis of sauerkraut, a german dish. We brits dont eat boiled onions either, but chip butties are the stuff of dreams and should never be knocked, especially by a country that can't decide which language to have as its main language. Now my to pennys worth is simple, the answer has already been provided, you don't need boiling water to cook onions, very hot water will suffice as most of the onion is water anyway!

As for my favourite, caramelised onions, frying is fantastic!!!

Sauerkraut is actually made from cabbage - finely shredded and fermented in lactic acid bacteria http://en.wikipedia.org/wiki/Sauerkraut

Personally, I can't stand onions no matter how they are cooked. =]

Haven't you folks ever heard of the Arrhenius equations. Basically they predict the aging of carbon based materials due to various radiation effects. For instance it is the effect of how long one needs to cook meat based on the cooking temperature or how long wire insulation will last when subjected to elevated temperature and ionizing radiation exposure.

Not knowing specifics I suspect that the onion will cook perfectly well at sub boiling temperatures. As adding the onion will cool the water a bit below boiling, how much is not clear and depends on the relative size of the onion and water volumes. In short if there was a look up table for cooking onions charted against temperature, I suspect the onion will cook at sub boiling temperatures, just a bit slower.

Have we got any materials aging experts out there?

I will reduce heat to minimum which is just sufficent to maintain the water at boiling temperature. Because at boiling temperature ir-respective of the heat addition water temperature will not increase so any extra heat will only evaporate the water without increaseing the cooking rate. to further conserve the heat I will cover the pot.

Raman Mahajan

India

Put a lid on it, this will increase the temperature in the pot thus decreasing cooking time.

Don't increase the heat. The water is already at 212F, the boiling point, and won't get any hotter, just create more steam.

That the water will not get any hotter than 100C was going to be my answer too, BUT,

I ~suppose~ that if you raise the temperature of the pan, the ~bottom~ of the onion might cook faster ?

boB K7IQ

Hi, boB K7IQ!

Welcome to the CR4 community! Hope you really enjoy participating with us in future discussions on all kinds of topics.

That's an interesting point about raising the temp of the bottom of the pot. However, since the contents of the pot remain at a constant temp, we would need the temp of the burner and some calorimetric information about the nature of the pot to determine whether and how much different the transfer of energy is into the water and from it through the pot. Isn't it just more practical to postulate the temp of the entire pot at point of contact with the boiling water to be 100^oC? If that's the case, then the onions will not be affected until the water boils off.

Mark

Yes, a higher boiling rate can reduce cooking time in two ways:
First it stirs the contents around.
Second (and possibly more important), it produces saturated water vapour bubbles that contact the onion. Water vapour can penetrate into the bulk of the onion, and then release its latent heat - so the onion both heats faster and retains more moisture, both of which will accelerate softening. This is similar to the difference between a water scald and a steam scald; steam scalds are generally deeper for the same exposure, and this would be even more pronounced if the steam is saturated.

But as to saving energy - not a chance, as the onions will cook even if you turn off the heat and insulate as soon as the water temperature recovers close enough to boiling (the temperature required depends on the relative thermal capacity of the pan and of the onions)

First who will eat boiled onions! The onions once put into the boiling water will take some time to reach 100 degrees after the water returns to a boil and to increase the tempurature do this in a pressure cooker for ever PSI of increased pressure you will get 3 degrees of tempurature once the releif goes of turn off the heat and let cook further to your desired liking

mfire

Hi, Guest!

Not increasing the heat, just keeping it on high to return it to the boil, since the exchange between the onions and the water probably lowered the temp and I assumed the boil largely quit as a result.

Turning the heat down to do a maintenance level after the water returns to the boil (meaning hopefully that the onions are also at 100oC now), and the pot is covered, to maintain a warm pot until the onions are finished . [And I do mean finished! ^^...]

Mark

If you have a lid, you would want to put the lid on the pot. Regardless of whether or not you have a lid, you want to increase the heat to again bring the water to a boil. Once the water is boiling again you would monitor the heat to just keep the water boiling, since any additional heat will not appreciably raise the water temperature(hence cook the onions faster) but rather just cause the water to turn to steam faster.

Once the water reaches boiling, thermodynamics show that until the water is completely evaporated, the temperature of the water will remain at approximately 212 deg F. (No need to factor in sea level variations to temperature as once the water reaches boiling, the temperature at that particular sea level does not change through out the process until the water is completely in the vapor state).

Dropping in the onions will temporarily become a heat sink, but my assumption is the onions will have a lot less mass than the pot of boiling water. Once the heat sink is overcome, the water begins to boil, then all one needs is enough energy to keep the water boiling. There is no need to add more energy in hopes of boiling the onions faster. Won't happen.

It will probably cook somewhat faster - see #39. But it certainly won't save energy.

After placing the onions into the previously boiling water, the water drops below the boiling point. One heats the water fairly rapidly to return to the boiling boint (which will likely be slightly higher than for water alone), and then turn down the heat as low as possible to maintain boiling. Additional heat will not make water rise above ~ 100 C, unless a pressure cooker is used.

The answer here is purely culinary. The moment the onions hit the water they are "cooked" and no longer "raw". The pot may be turned off and onions removed. Further heating of the water will be fruitless. Although I have seen some good ideas as to how to cook them further and consume the potential of the energy already expended. This is the case at any level. At, below, or above the sea.

Hi, seulbog!

And a great big fat jolly WELCOME to the CR4 community.

Thanks for this very interesting contribution. It reminds me of the theory of mixed fluids. Done is done.

Except surely 'how well' done is a consideration?

Mark

Thanx for the welcome mat!

To me, for the sake of this question, "how well done" is surely not a consideration. Our goal is to 1) "cook onions"(not necessarily well done) 2) "conserve energy". That would mean we eat them "Blanched". Or, as many have mentioned, we have them "stewed" at a rate of conserved heat loss (remove heat source and insulate). Any further addition of heat, high or low,for any reason is to further cook them and thus wasting energy as "cooking" is instantaneous.

If "how well done" is a consideration, throw the water out and saute them with butter and mushrooms! That's how I see them as "done well".

Now THAT is a good answer (so voted), although there's something to be said for a baked onion - MMM-mmm-MMM!

It won't work to merely increase the heat to cause faster cooking, because, given an ambient air pressure above the water in the pot (open system, not a pressure cooker, more on that later), the water will only reach 212 f/100 C. This is due to the fact that as you increase the water temperature, you increase vapor production, which wicks off the excess heat. More heat only dissipates the available water quicker. The only way to increase the heat is to put the process in a pressure cooker, which, because of the artificially increased pressure above the water (vapor pressure) allows for boiling at a higher temperature (if memory serves me right, automobile radiators, at 14-18 psi, do NOT boil at temperatures up to about 245 f, for which someone else will have to supply the C equivalent). So, putting the process in a sealed vessel, such as the pressure cooker, will allow for faster cooking, due to higher temperatures. This is one of the reasons why cooking foods for canning is done in pressure cookers. Not only does the higher temperature affect a more effective sterilizing process, but it also allows for much faster cooking of the product.

Micah

Concur with all responses that would not increase or allow the heat source to remain as is, because boiling water does not in fact get hotter, it only evaporates faster. I would reduce the heat to a simmer upon addition of any vegetables, and put a lid on the pot. However, the concerns about uneven cooking of large onions is valid. Unless these are the smaller (bite-size) onions commonly found in stews, I would add a wire rack beneath them to allow the hot water to circulate more completely around the onions. Easier and safer to put it in the pot first, then add water, with perhaps a bit of salt - it doesnt help the water get hotter, but any impurities such as salt or minerals will help it reach the boiling temperature a tad faster. Keep in mind, cooking IS chemistry! Perhaps the first applied science...

Saturated steam is much more dangerous than boiling water. Equivalent applies to cooking onions inside a boiling pan. Quicker, but still wasteful of energy.

Dangerous thinking! They are both damgerous but Boiling water has a higher heat content than steam - unless it is superheated it will be 100º (depending upon altitude) Boiling Salted water will be Higher - not a lot but still higher.

Heat content by volume is higher for water, but heat content by mass is much higher* for steam.

The important features are:
i) that steam will release all the latent heat on contact with material below local boiling point; whereas water will only release the heat corresponding to the temperature difference; and
ii) steam will diffuse through the surface of the onion and so raise the internal temperature directly, rather than relying solely on conduction.

So, the saturated steam in the bubbles of a rolling boil will probably be marginally less effective at the initial part of heating the onion - say from room temperature to about 50^OC. However, as the temperature of the onion approaches boiling the steam will be more effective - and if we rely on conduction alone, the change from 50 to 97 will take rather more than five times longer than the change from 50 to 70.

All the above is rather well borne out by the difference in speed and intensity between steam scalds and water scalds

*The available heat for cooling water from 100-degrees to 25 degrees is about 620-Joules/gm, whereas for steam it is about 2880-Joules/gm

cover tightly to build up pressure then reduce heat to a simmer. Allowing pressure to build moderately will speed up the process by " impregnateing " the workpiece w/ heat.

Hi, wilycoyote!

Very nice point. Putting the lid on immediately and turning the burner down to simmer may very well allow the water to return to a boil without adding more heat because of the buildup of pressure below it. Very good thinking. GA.

Mark

If the temperature does not need to be sustained at or very near boiling for the onion to cook properly, then the first option (turn off the heat and isulate the pot is the most energy efficient.

If the center of the onion needs to reach near 100 degc for proper cooking, then increasing heat may be the most efficient way to cook the onion. Reducing heat to the minimum to maintain 100 degrees will ultimately cook the onion, but heating of the onion would be mostly by conduction.

Increasing heat to the pot will reeult in bubbles causing flow and turbulence around the onion. Increased heat transfer from the bulk fluid to the onion cooks it faster. (This is why many recipies call for a rolling boil).

The question is asking what should you do to conserve energy. Obviously, turn off the heat. The onions will continue to "cook" for a period of time. They do not have to be at 100 DEG C to "cook" very thoroughly. In order to cook thoroughly you only need to seal the pot and insulate well.

This reminds me of how I used to cook cured country hams at Christmas. I would boil the water in a lard can on the wood stove. The ham would be in the lard can at the time. I would only need to boil the water for 1/2 hour. I had all of the blankets I could round up layed out on the floor. Once the 1/2 hour was up, I would seal the lid on the lard can with masking tape and place the lard can on the blankets. Then I would start folding the blankets over one by one until there was a huge mound in the center of the floor. The next morning (Christmas morning) I would unfold all the blankets to get to my prize, a fully cooked ham. Upon opening the lard can I had to be careful because the steam from that water would still burn. This was not only a conservation of energy but the hams were delicious!

Goal)You want to cook some onions.

Method)You start by bringing a pot of water to the boiling point

Goal)you want to conserve as much energy as possible

Second statement does not say boil. When you boil water you lose super heat BTUs with the steam.

So to cook onions and conserve energy do not boil the water. Bring the water almost to a boil and add onions. Bring onions and water almost to a boil and stop adding heat but insulate pot to conserve heat already in use.

Better yet cook in insulated pot to start with and when it reaches 99.9 C turn off.

Brad

I agree with your thinking, but I would have put the onions in the pot at the same time as the water. Then follow your instructions.

if pot is insulated b4 cooking, heat transfer from source into pot is made less efficient.

insulation should be applied *after* addition of heat to pot, not b4. keep heat in, not keep heat out.

Apply the heat inside the water, inside the pot, inside the insulation. If the pot is a better conductor of heat than water use the pot to increase surface area induction. To heat the insulation is absurd.

Brad

As i was teched in high school, i guess its the matter of pressure so the more pressure the faster and sooner it cocks and the increase in heating don't do any good and is not conserving the energy.

Hi, mahyar 6131!

Welcome to CR4 ! Hope you enjoy yourself in here.

How would you increase the pressure on these onions?

Mark

You could give them a few CR4 Challenge Questions and say you want an answer by Friday afternoon!

Hi, Mr. Truman Brain!

OK OK. My arm has been twisted sufficiently!!

GA

Mark

Hi,

Take the cooking process below the sea level, eventually increasing the atm pr.

T proportional to P , u can conserve energy.

Wow!

Creativity to burn! Loved the concept. I'm awarding you my GA, but with the proviso that since we understand the question maintains a location at sea level, your answer's most likely not the one being sought. The GA's for a brilliant suggestion and original thinking !

Mark

Depending on the quantity of onion,choose the vessel in such a way that the onion occupies 60% of the volume of the vessel and it has wider base and narrow opening at the top.Add about 15 % water and leave 25% of the volume of the vessel empty.

As onion by itself contain lot of water, you need to add only little water for boiling.

Now close the lid partially and heat the vessel till the content start boiling.It takes less time as the quantity of water is less. Now close the lid fully and stop heating.Remove the vessel and place it inside an insulating bag,Pull the top string of the bag so that the entire vessel is wrapped tightly.If you remove it after 15 min , you will have fully boiled hot steaming onions with least energy usage.

choose the vessel in such a way that the onion occupies 60% of the volume

I'm having trouble picturing this vessel. It would have to be very tight fitting around the onion (?).

Challenge is to cook the onion with minmum energy.You can pick up any vessel .You are going to fill only 60% volume with onion and add water just to immerse the onion.40% space is still free. No need to fill up even additional 15 % which I mntioned earlier.

Spherical Onion, Vol = 4/3 πr³

Cylindrical pan (height,width = 2r), Vol = 2πr³

Volume of onion = 66.6_r %

To get 60% onion volume, the vessel could be made slightly wider (to allow steam movement) and slightly higher, so yes it works but I've no idea what the water depth would be.

The water level would go all the way to the bottom of the pot!

After putting the onions in wait until water returns to a boil then turn down the flame to maintain a slow boil and cover. The slow boil will maintain the water temperature at its highest point with least amount of fuel consumption so the onions cook in the least amount of time.

Hi, ozzb!

You and me, pal. We agreed on this one.

But anymore I dunno. There are some very cagey responses in here. For example, 31 kinda takes the necessity to return the onions to a boil out of the equation by using a pressurized lid to do that very thing. We're looking for efficiency, so maybe he's gone one better than us.

Mark

I read most of the replies about turning off the heat and insulating. Problem is some have dropped it to an onion when it says onions don't know how many, how big or what kind. Most recipes have an onion cooked from 15 to 30 minutes. A bit of a difference in the time to cook whats called a boiling onion then say a large Vidalia. If the onions are large and there are many the water may not hold enough heat to cook them done thru out.

More and larger onions require more water in larger pot, so more heat capacity. Also relative surface area is smaller, so it is easier to insulate. But you are right that this will probably not work at all if you have the smallest possible pan and amount of water to cover the amount of onion you are cooking, particularly if the water is unsalted. But who in their right mind adds the onions after the water has boiled anyway?