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

"At this point, you want to conserve as much energy as possible. What should you?" do?

You should add more heat until it boils again because the salt raises the boiling point and the onions cooled off the water. Then turn off the heat and insulate the pot. After that, lie down and go the sleep until the onions are done.

I would offer to you and some others, that talk of modifying (e.g., insulating) the pot (or even adding salt...and other ingenuous tricks) misconstrues the original question and, therefore, cannot be correct...or reasonably GA.

The challenge mandates both the conditions (tantamount to the actual start-of-cook-time preconditions) and the options available for cooking the onion objects to whatever the subjective condition of "done-ness" might be. The preconditions are:

• Sea level altitude (and water °BP)
• Pot
• Water (that happens to be boiling)
• An adjustable heat source under the pot (i.e., a gas burner or electric element...which we infer [aside from common sense] because the challenge implies that the heat source can be adjusted) which happens to be in an On-at-some-level condition.
• Onions at the ready...which we are constrained to assume are of equal species and size (or even chopped up uniformly)...which is the same as saying that onion properties are to be deemed irrelevant for purpose of answering the challenge.

The available options at and after the time of adding the onions (this is where a bit of challenger deviousness comes into play) are:

• Turn the heat source up (to higher heat output) under the pot, or
• Turn the heat down, or
• Leave the heat input as is; in addition, or not, to:
• Do nothing else, or
• Do anything else which does not alter the challenge mandated conditions (which does not change the premise of the challenge).

Excuse me if I overlooked it but, having glanced over preceding posts before posting here, I am surprised that no one has said or included in their answer: "Put the lid on the pot." Doing that in addition to lowering the heat source fuel consumption are what deductively seem best to me for maximally conserving energy.

LET US EAT ONION UNCOOKED>

This matter is not going to be resolved as, though what we all have said is true, definition of what is "cooked" is also subjective and has no definate instance. Thus, we can not device the DESIGN OF EXPERIMENT and confirm by changing different parameters.

ghusas, if you meant that as a gambit, then I accept...

I cannot agree with your syllogism, which states to the effect:

• A particular cooking method cooks onions to doneness with greatest energy efficiency (i.e., with least fuel consumed).

• CR4 challenge respondents disagree on what constitutes doneness of cooked onions.

• Therefore the most energy-efficient cooking method cannot be decided.

The fallacy is that you have altered the challenge's predicate—..."You want [in the British sense, 'one wants'] to cook some onions" [and by inference...] to some degree of doneness according to personal taste"—into a statement in which many (a collective one rather than an individual one) are (in effect) to judge the onions' doneness as they cook the onions; ...that in addition to adding a requirement not included in the challenge: that the onions must, of necessity, be cooked to some specific degree of doneness.

Since, by inference, the challenge presupposes an arbitrary level of cooked onion doneness according to the individual reader's taste, we are bound to agreement about what "doneness" will mean, and there can be no dispute about when it is that the "cooking experiment" ends and the fuel consumption (after the onions were added to the pot) is measured. We are furthermore only compelled to agree:

1. On the measured amount of consumed and wasted (fuel) energy,
2. That the energy measured for any other cooking method will be greater (than that measured in 1.),
3. That 1. and 2. taken together will hold for all repetitions (all "instances") of the onion cooking "experiment," and
4. That the conditions as established by the challenge were met, and were the same in all instances (as in 3.).

Following such a protocol as this, we will have neither re-devised the "experiment design" given by the challenge nor attempted any parameter change in order to "confirm" or disprove the correctness (of any challenge response); nor did the post to which you responded violate that protocol.

Notwithstanding the above, the exceptive "truth" about which you claim we all agree is unclear to me. You seem to be saying that (before I posted) the matter had already been mutually settled...in terms of an answer to the challenge or the invalidity of the challenge.

I believe that the constraints set in challenge (particularly sea level) are intended to lead to a single answer. So the challenger implies that all initial conditions are independent of procedure, as is the required doneness of the onion.

Nevertheless, I'm not entirely convinced that there is a unique answer to "the best way". Suppose the pan is very thin with a concave base that exactly fits the (say) two onions, and the peeled onions come direct from a near-freezing fridge and are relatively flat-topped and barely covered by the water, plus the onions are required to be cooked to disintegration; I'm not convinced that sufficient heat will be stored to cook the onions that far without some measure of reheating. On the other hand, the answer to "should you increase the heat" is always "no".

Is there a counterpoint in there somewhere?

I can't help sensing a disconnect between where you believe the challange leads us and the possiblities you offer for leading us there.

Hi, CowAnon!

I think several of us have mentioned putting the lid on the pot (e.g. 13). I didn't notice anybody adding in the altitude of the pot and boiling point of the water as points to consider, since the event takes place at sea level (but I might've missed it.)

Perhaps it is part of a shore lunch??

Mark

Hi to you, Mark, and thanks for pointing out what I overlooked; and apologies to all closed-pot proponents.

Others are not to be faulted for not mentioning altitude & boiling point as it is immaterial so long as altitude is the same in all instances of conceptualized onion cooking. I suspect that altitude was thrown in somewhat in the same devious manner as the mention of (possibly) saving fuel by turning up the heat to (supposedly) accelerate cooking and reduce cooktime—a clever conceit meant mostly to mislead.

No, I think altitude was mentioned to ensure a suitable amount of stored heat so the onions could reach cooking temperature without additional heating.

Reductio ad absurdum: I doubt the lid-closing and insulation would work anywhere near the top of Everest if using unsalted water - unless the excess volume of water was rather large.

CowAnon said that he is surprised that no one said to put a lid on it.

#7 Reply Ed " fuzzyE " Kedz said to cover it.

The question didn't even say that the pot had a lid. Our only choice is to turn the heat up or not. It's "Yes" or "No" plus explanation. I say "No" - it won't save energy and I'm in no hurry for stewed onion.

Quite a few replies mentioned lids a few even mentioned pressure cookers. I personally feel that this "challenge" should be on one of the cooking forums.

Water temp cannot exceed water boiling point so the onions' temp cannot exceed water boiling point; so raising heat under pan will be pointless.

When onions are added to water at rolling boil, the water temp will drop to below water boiling point. You will continue at same burner/element setting until water boils again, at which point water and onions will be at water boiling point—the maximum possible temperature for both. At this point, lower burner/element heat so that water continues boiling at simmer. The water, and hence the onions, will remain at water boiling point but with less consumption of heat energy input. (Water boiling "faster" is simply water evaporating faster....with no additional temperature increase of onions.) So that is what you should do: bring water back to boil and then lower the heat to minimum sustained boil level.

There are some true engineering answers on this one. Is this why engineers never end up owning restaurants? I thought of a few answers as I read this article through.

1. Does the type of onion matter?

2. What about the contaminants in the water, I mean, we cannot assume we are exactly at 100 C/ 212F

3. Doesn't matter whether it's the Germans or English taste buds or whoever, the questions were on boiled onions. Do we always weigh in our opinion on that, that doesn't affect us? Yes...we are engineers

4. Designing a pot around an onion....should every vegetable have it's own pot?

5. Salt isn't the only additive you can have here. Some like onions with a spoon of vinegar when boiling.

6. While you are contemplating the onion debate who is watching the fish on the grill?

As to your point #1, I should think it would very much matter. Stew-sized ("boiling") onions or scallions would be done throughout in the time it takes a large "slicing" onion to warm up.

And point #4, absolutely! We (as engineers) should support having carrot pots, cabbage pots, parsnip pots, spinach pots, rutabaga pots, and so on. What do engineers do but design things, right?!?

If engineers were able to design a pot that raises the lid, then why not one that lowers the lid? Wait...huh, what was the topic again?

Let's keep the future "challenges" more scientifically oriented. Look at some of the answers and responses that came out of the woodwork and / or outerspace for this one. I especially liked the one about adding salt to raise the boiling point of the water. It is quite obvious that this moron NEVER cooked much of anything in his life. The small amount of salt added will not raise the temp even ONE FRACTION of a degree - all one needs to do is to consult a cookbook - I have seen many that say the salt is for flavor only - this moron even comes back and states that it is still a scientific fact ... none the less. AND includes a link to PROVE it. I D I O T !!

Ummm, Lemme guess....

You don't agree that changing the SG of water by adding salt, oxygen, onions, or anything else, will alter its boiling point.

Right?

Now, I know it's a confusing point, but sadly, water is very sneaky about just when it will boil, and uses almost any excuse to pick a different temperature each time . What's in the water is the most common excuse for it to shift. The darn stuff even changes its ability to hold up floating things, like ships and so on, depending upon what's in it. It's just not reliable!

Fortunately for us, we have pure water that we can boil at the same temperature each time.

Ummm...unless we try it at a different altitude.

Saaay...who invented that stuff, anyway?

Ah, well, it's the least of our worries.

What's that you say....its not??? We have to worry about water a whole lot????

Find me somewhere to hide! I remember a musical called 'Stop The World! I Want To Get Off'. Now I know how the writer must've felt!

Mark

Well, since the onions are in water, even if you keep adding more heat, water will only boil at 100 C and the temperature would not increase above that. Instead you should cover the pot since the temperature at which a fluid boils is when the vapor pressure equals the atmospheric pressure, thus on cover the pressure within the vessel increases which in turn causes the water to boil at a higher temperature. You cook faster because of the higher temperature.

Close but no cigar—that's an American (English too?) saying (referring to the offer of a cigar to reward a successful endeavor...such as a spouse's delivery of a live child). What you say would hold true if (and only if) it was a pressure cooker being covered with its pressure-regulating lid, but it does not...and the challenge, having stipulated a standard pot, neither contemplates nor allows a pressure cooker. Moreover, placing a lid on a cooking pot does not alter the under-lid pressure from atmospheric in any appreciable degree.

The reason why covering with the lid is effective is twofold and can best be described by contrasting, in each instance, the dynamics as between "lid off" and "lid on" cooking:

1. Principle: The total capacity, both instantaneously and throughout the cooking process, of heat available for transfer to the onions varies as the volume of water in the cooking vessel. This means:
1. That as an open pot boils, water evaporation loss reduces the volume of water, and thus the capacity of heat, available for cooking the onions.
2. That as, in a covered pot, water evaporates, rises, condenses (and otherwise remains [largely] confined as hot vapor [...in cooking parlance, steam]) on the underside of the lid, and then drops back into the vessel, water volume and cooking heat capacity is conserved.
• Please note: It is just this dynamic which makes it possible (in fact necessary in order to curtail lid bumping and boil-over) to lower the heat (to simmer) under a covered pot without extending cooking time.
2. Principle: Heat lost from a cooking vessel is energy not available for transfer to the cooking produce (to the onions), and the rate at which heat is lost varies directly as the tendency towards temperature decrease in the cooking medium (water)—such decrease which must be compensated by increased heat input from underneath the pot. From this can be deduced:
1. That an open cooking pot, losing not only heat conducted and radiated from the vessel, but also heat from the entire cooking medium surface, will require a comparatively greater input of source heat whereas, in contrast...
2. A covered pot, by blocking loss of heat rising from the cooking medium (by limiting heat loss to that radiated from vessel and lid), will require comparatively lesser source heat input.

Sahasushank, I hope you will find these attempted clarifications useful.

Got it boss . I actually realized the pressure cooker thing as soon as submitted my post. If the lid were big and heavy and think and made of lid then it might still have been helpful :P.

Yes the lid does prevent water vapor from exiting into the atmosphere and instead reaches a dynamic equilibrium with the water in the pot thus conserving heat.

* Never play with fire, or steam ... you always get burned (case in point )

Put a lid on the pot, unless the pot is a pressure cooker, it won't do any good to increase the heat. By placing a lid on the pot you are conserving energy and may be able to reduce the heat being applied to it.

To use the least amount of energy, keep the water boiling at the lowest heat imput possible. The water won't get over 212°F and therefore, the onions won't either. To speed up the process and use less energy, put a lid on the pot with a weight to increase the pressure and therefore, the temperture, and shorten the cooking time with less energy used. However, you may get zapped when you remove the lid.

This seems too easy. However, have you seen the pressure cookers deep fat fryers? They've been around for quite some time. It's one of the best examples of false advertising I'ver ever seen. Since the oil doesn't boil in the cooking range of tempertures, there's no pressure to heat it up faster. A woman at WalMart told me that their pressure cooker deep fat fryer's lid broke. They used it without the lid and the chicken cooked just as fast! And it should have.

If the heat content of the water, pot, and stove is enough to cook the onions, then the only correct answer is to reduce the heat source to zero. However, if sufficient cooking requires more heat, then we have a problem. It would seem that any further boiling would be wasted heat because it does not raise the temp of the water but does consume energy which is lost as steam. However, I know from my very limited experience in cooking, that a simmer is required to cook some foods. If the water does not boil at all, the food just sits there and cooks very slowly, if at all.

Greetings: At least 3 entries have said this, but nobody seems to notice: onions do not need anything like 100C to cook - they just need to attain an internal temperature that causes break-down of the cellular structure (which I seem to remember is somewhere about 60C). So long as there is sufficient thermal energy in the water so that the combination of onions & water in the end attains this temperature then the onions will cook - so long as heat-loss to the big wide world is minimised. This is the basis of the the 'straw bale' cooker used in the rural areas of the world for centuries:you heat everything to near-boiling - pop it in the insulated box and some hours later all is cooked - like a slow cooker, only more efficient. Boiling points, salt, pressure and all the other parameters mentioned above are just not important.....

Hello all

As a person who is not an engineer, but was a boy scout at one time, I have cooked in the outdoors several times. The way I always cooked with a minimum amount of fuel was to dig a hole and line it with river rocks. Build the fire in the hole on top of the rocks. Place the pot with the water and other assorted foodstuffs directly on the fire to heat it. Once it comes to a boil put the lid on it and cover it with a sheet of tin foil, and then cover the pot with the dirt you removed when you dug the hole. After a whole day of hiking or fishing you come back to camp and have a very nicely cooked meal after uncovering the pot.

Increasing the heat won't raise the temperature of the water, because the energy is is being used to change the state from water steam. The water temperature will remain at 212 degrees (I guess a little higher because of the onions). You should probably just cover the pot and use just enough heat to boil the water.

While using the energy already in the water to cook the onions in a sealed and insulated situation is the ideal solution, this will only work if the calorific value of the water is sufficient to raise the temperature of the onions to the temperature required to cook them and to also maintain it at this temperature for long enough for them to cook. Without meeting these two requirements you gonna have raw onions. They might be warm, hot even, but not cooked! Additional heat will be required if the amount of onions is large enough for the energy in the water to be insufficient for the onions to reach that cooking temperature and maintain it through whatever heat losses may occur until they are cooked. And if we gonna split hairs we gotta remember that the chemical and physical reactions that take place in cooking can also absorb energy. I could add more about safe cooking temperatures having to be high enough to kill any pathogens present, but that might be outside the remit of this question.

I am growing weary of reading all these posts that state that the water has to be 212 DEG F. to cook the onions and that heat needs to be applied to maintain the water at the boiling point or somewhere near to it to do it. While working at Chick-Fil-A after retirement as a project enginer I picked up some info on cooking stuff. The chicken only has to have an internal temperature of 160 DEG F. to be considered done and suitable for consumption. Admittedly, we usually had higher temperature readings present and there was a time factor of 3 minutes or more involved in the pressurized Henny (deep fryer) but obviously 212 DEG F. was not necessary to cook the chicken. I would say that an onion would be safer to eat than a chicken that was under cooked, wouldn't you? As far as the question is concerned, there is insufficient information to determine what would be considered a correct answer because we do not know the volume of water, the mass of the onions or the temperature that the water would drop to once the unknown quantity of onions were added to the pot. All I know is that to conserve energy, you have to shut off the heat source!

Agreed, onions don't need 212^OF to cook, and so long as you peel them you don't normally need to cook them at all to make them safe. But if you wish to soften the fibres or convert starch to sugars, you may need somewhat higher temperatures than are needed to kill bacteria.

But remember - if you place onions from room-temperature into boiling water and pan of double the onion's thermal mass, the highest temperature the inside of the onion could possibly reach would be 161^OF - and that assumes perfect insulation and no energy lost to the cooking process!

To CR4 passive (regenerative?) cooking proponents—

While the idea embodied in (was it?) straw bale cookers, buried Boy Scout buddy cookers, and such might well be correct—and while those solutions do appear to address what seems to be intentional obfuscation for the purpose of misleading in the Challenge's phrasing—it seems to me that all these "recommendations" are at odds with the Challenge in that they (each) are both different and distinct from the Challenge scenario in several ways:

1. All resort to insulation of some kind to effect heat conservation...whereas, the challenge posits only a pot (by inference: a pot on a range top), and neither contemplates nor allows insulation or movement to insulation. The insulated cooking methods, conversely, do not contemplate heat radiation from the cooking vessel, or heat being sunk by conduction (possibly), even to the cookstove/range itself.
2. In most such passive cooking processes (of a certainty the Boy Scout method), food is prepared by cutting (slicing, dicing, cubing, etc. based on produce hardness and cooking resistance) whereas the challenge makes no mention (and accordingly must be presumed not to include) such preparation of the onions.
3. The no-new-heat recommendations describe a "cookage" finishing process in which, before heat source removal, both water and food item is actively heated to water °bp; in the challenge, unheated onions are added to b-p water under which heat has been already been removed...such that the water has begun cooling even as "cooling food" is added. It cannot be said in this wise that in bringing the water to °bp the onions are thoroughly, or sufficently, cooked, and thus need no more heating.

It is these elements of distinction which, I would offer, must be reconciled in some way...even, as some have suggested, it leads to a discrediting of the challenge itself or of the predetermined "challenge answer" that awaits us all.

This is not to say, as some have cogently opined, that the challenge can have no answer—although it might...unless a valid and provable alternative answer that meets all challenge conditions can be demonstrated. Then again, perhaps there is some mysterious revellation that awaits us all!

Greetings: the Challange mentions no prohibitions about additional equipment - its just asks what to do next: use of an insulator is an abvious way of reducing the energy requirements. I reiterate: so long as the temperature inside the food attains a sufficient degree to cook the food, heat loss is not relevant - the process of insulation is, de facto, one of reducing radiative or conductive energy transfer.

Chopping up food is _not_ important: given sufficient time and little heat loss, the end result will be the same: I have cooked whole hams by this method - it just takes more time than 'shoving it in the oven' (and the loss through shrinkage is greatly reduced).

It is not important that the whole mass of food and fluid be at boiling point (were the centre of the onions at 100C then they would be cooked already......). The sole requirement is that there is sufficient thermal energy in the fluid alone such that when the (initially cold) onions and the fluid reach equilibrium, the inner temperature of the onions is above the 'cooked' state. As onions are (mostly) water, then they will have a specific heat not too different from that of water: if we assume 1kg of onions at 20C added to (say) 2kg of water at 100C, the adiabatic equilibrium state will be at a temperature of over 70C - sufficient to cook the poor onions to a very soggy state.

Onions are (IMHO) much better roasted whole with loads of butter.......

Martin

Martin, thanks for responding in defense of your prior post. Perhaps it is your preference for dry-cooked, and mine for stewed, that brings us to this seeming impasse .

It may well be that the official answer will not be without a surprise that conveniently includes actions apart from those stated and implied as permissible in the challenge; and it wouldn't be the first time a challenge has fallen short in the un-ambiguousness of its presentation.

Accordingly, I can appreciate your view (regarding the actual commencement of onion cooking) that, because nothing apart from the (theretofore) initial "ground rules" and final outcome are explicitly stated, then there is likewise nothing to preclude modifying the pot to confer insulative resistance to loss of heat. It still seems to me, though, that that would be a change of the ground rules; that the taking of any such license to achieve a certain outcome (albeit that it is a personally satisfying outcome) is not something contemplated by the challenge, if it is to be regarded as credible.

And, if such a change were not an overstepping of the ground rules, what then would prevent any other sort of modification that might achieved the same end result: say, spraying the pot black after the onions were added and then focusing free solar energy on it—among any number of "tricks" that could be conceived. By this reasoning, it could be said that your "solution," and its justification, leads not to the challenge answer it purposes but, rather, to an answer not unlike that stated by some others: that conceived as the challenge is, there can be no indisputable answer.

If, however, the challenge does permit of multiple approaches to its singular stated objective, it will be interesting to see how the official answer will be able to be declared without also addressing all of those possible methods...

The simplest solution is to cover the pot and reduce the heat.

The complex solution is to somehow lower and maintain the air pressure in the pot and reduce the heat. Although the temperature of the boiling water and onions will be lowered, the same boiling effect will occur. However it is doubtful any total energy will be conserved due to the energy requirements to lower the air pressure.

Lowering the pressure would cause the water to loose heat faster. This would be a waste of energy. The simple solution is cover the pot, remove from heat, seal the lid and insulate the pot (as with blankets wrapped around it) until the onions are done to your liking.

Do nothing. Just don't stare at the pot.

You want to insulate the pot and boil at a medium temperture.

Thanks to who-ever has given the initial response the GA marks.

There seems to be great controversy developed as to "What is cooked?" so I had a look at various references that I have at home and found a very interesting point.

Almost without fail, they list "cooked" as meaning "Modification of food by adding heat."

That being the case, the onions are by definition "cooked" the moment they hit the hot water. (They have been scalded and thus modified by heat.)

Any further "cooking" then becomes a matter of personal choice. The fact that I tended towards a low energy solution that would "take the sting out" by prolonging the exposure to heat is probably an outcome of my parents anglo/celtic background (stews and casseroles) as opposed to Mediteranean (salads and such).

I still defer to my original suggestion. There is no requirement to add further heat to "cook" the onions.

Maybe, maybe not...is how I view it so far. Would you say that the sufficency of (passive) onion cooking (in cooling-off water) would be enough (i.e., arbitrarily satisfactory), irrespective of the unstated conditions of onion and/or of ambient temperature? ...sSeems that that is the justification that would be required for "deferring" to your own initial answer.

It's possible to cook pasta by putting it in a normal Thermos (vacuum) flask with some boiling water. Somewhere out there is a company that markets a flask just for this purpose (although it's no different to an ordinary drinks flask). Being curious, I tried this. It worked fine (I used some dried spaghetti), although I'm sure I could taste a tang of coffee. The spaghetti packet said it needed about 10 minutes on a slow boil, and the flask got it to an acceptable 'al dente' state. If we had Leeks instead of onions (similar taste/family of veg, more convenient shape) I'd pour the boiling water in a flask and add the veg.

Ya, Chris, you could use one of these,

I'm sure it would work for onions too.

Hey, you found one Bricktop ! I'd seen the thing on one of those 'gadget' catalogues but couldn't remember who made it. My flask experiment left me undecided - the pasta was slightly on the wrong side of al dente, but it was edible. The real 'must-have' is an egg cuber ;

......you need another gadget to enlarge it.

Hell, why stop with square eggs:

Not to sure it would be a good idea to use leeks instead. Why you might ask. Nobody likes to have a leeky thermos!

I 2 tip my hat.

You deserve an award for that !

Well done (pun partially intended) Brick, old Top! For you...

...and...

Turning up the heat won't do anything because the liquid water in which you placed the onions will remain at 100 degrees C - anything above that will turn into steam and be lost outside the system. Put a lid on it.

This question reminds me of a cooking product that was being sold many years ago. I may have some of the details slightly incorrect, but the idea is there.

It was a special pot that you put all the dry/uncooked ingredients for a stew, rice, or pasta dish into the pot. Add water, seal the lid and heat up. It had a gauge that showed when the pot was at the optimum temperature. From memory this took 5 to 10 minutes. Once optimum temperature was reached the pot was placed into another insulated pot that vacuum sealed (I assume by radiant heat driving out air, no pumps). You then left everything for several hours and everything got cooked.

In fact it was claimed that you could leave it all day and that the results would still be perfect. They also claimed that you could put the whole thing in a fridge or freezer and it would still cook.

I can see why this would work, especially for these types of dishes. All you need is boiling or near boiling water, say +90C, for the correct amount of time. That time will vary depending on temperature of the water. The vacuum just keeps everything at a near constant temperature for a long time.

To cook something you just have heat it to the correct temperature and keep it there for an appropriate length of time. The only reason to apply more energy is to overcome any losses in the process. The main losses in boiling onions, once the onions are up to temperature, is loss of heat through steam and radiated heat from the pot and water surface.

So, for this question, it seems that the most energy efficient way to cook(boil) an onion is to boil the water, add the onion, then place an air tight lid on the pot and insulate the pot. Just an Engineer is correct.

Depending on how much water and how much onion you have, you may need to heat the water for a little while after adding the onion to compensate for temperature drop.

The pot and lid should be able to withstand the pressure initially created when sealed. Though if it is not air tight it probably won't matter too much since the water should be hot enough to do the job, holding in steam just decreases the cooking time.

I would probably add the onion to the cold water before boiling so the correct amount of energy is used to bring everything to the boil.

________________________________

Sometimes long explanations are needed for simple answers

You make a lot of sense, guest. Why don't you register so we know who you are. Then, we'll talk.

Unless your pot is a pressure cooker, the water temperature will never go above 100 deg C, so by increasing the amount of heat you will only waste energy by converting water into steam and bleeding it off at the surface. You should regulate the heat that the water temperature remains at just below 100 deg C without actually boiling.

Assuming that the cooking temperature T must be 100°C constant for a definite amount of time t, the only possible strategy is to keep the energy coming from the cooker (flame, heating resistor, whatever) at the absolute minimum to mantain the water in a gently boiling status (up to the point you have boiling water the temperature will be constant). The integral of the energy vs. time (and associated costs) will be minimized.

Stefano, chemist, Rome (ITALY).

There was no basis for any constant temperature in the challenge; nor can there be any. It merely implied boiling point at time of onion insertion; nor was time a paramount consideration...despite the misdirection about turning up the heat. Integrating heat versus time misses the point unless you have a formula for energy loss from the (unknown volume of water) to the onions (versus energy loss to the atmosphere). What is to be optimized is simply the energy consumed for one cooking methodology as against all possible alternative methodologies, given the conditions as they are provided.

Hello.

Once the water is boiling, increasing the heat will not cook the onions any faster. Once water reaches 212 degrees Fahrenheit or 100 Celsius (at sea level), it remains at that temperature and is gradually converted to steam. The only way to increase the boiling temperature of the water would be to put it under pressure, just like in a pressure cooker. Since we're using a regular pot, the best way to conserve energy would be to keep the heat just at the point where the water continues to boil vigorously.

Mike Veach

Hi, Mike!

I don't recall whether anyone actually recommended turning up the heat, so I'm not sure where all this discussion about heat increases originated. Perhaps it happened as a result of the recommendation to allow the onion/water admixture to return to the boil before covering and removing from heat/turning it down to simmer.

Some have recommended that when/if removing the pot from heat, it should be "insulated" to minimize loss into the atmosphere. It's not just a cooking method, it maintains the cooking conditions while saving energy. As legitimate a method as any other, like covering with a lid or resting inside a tea cozy, both of which work to the same end: maximizing your available energy usage. If you can find a pot lid, you can find a tea cozy; and although it's unlikely you're cooking these onions in a barn, you can probably find enough straw someplace to do the same thing. (Poor Raggedy Ann...but never mind, you can re-stuff her later.)

Obviously, since the heat was enough to boil the water in the first place and we are conserving energy, the same amount of heat transfer will re-boil the water after the onions are added, without the need to "turn up the heat".

Mark

Bring the water to boil, drop in onions, put lid on pot and when water begins to boil again (a few seconds usually) REDUCE the flame (heat) to just maintain the boil. The lid retains the heat just fine and no additional insulation is needed because it'd have to be fire retardant. The lid close couples the convection cycle and while the steam condenses on the lid, it only loses a couple of degrees in the process, returning to the pot nearly as hot as when it left saving energy over releasing to the atmosphere and having to heat the balance of the water. My wife has never understood this concept and thinks that a roiling boil with an open pot is both better and faster than closing the lid.

I would bring the onions and water back to a boil and then turn off the stove. The residual energy in the water will cook the onions as it cools. It will take more time, but less energy.

increasing the energy input into boiling water will not increase the water temperature (the temperature of a boiling liquid is independent of heat input unless the pressure changes or the composition of the water changes), it will only cause the water to boil faster. If there is no temperature increase then the onions will not cook any faster unless you decrease the resistance to thermal transfer to the onions. The increase in agitation due to the more rapid boiling is unlikey to increase teh heat transfer to the onions. Options? 1) Add salt to the water to elevate the boiling temperature. 2) Cut the onions in half to increase surface area to volume ratio and to decrease the thermal tranfer distance within the onion. 3) Make sure the pot is a pressure cooker.

immediately stop the cooking process and cover the pot. Measure the decline in temperature. When dT/dt = zero (adiabatic case) or approaches a constant drop, then re-apply heat

The first thing you do is chop the onions into small pieces so that they will cook fast.

You can then pour out some of the water as you will not need as much liquid to cover the onions. This will reduce the energy necessary to boil the remaining water.

Toss in a tablespoon of salt, which will increase the boiling point of the water, also reducing the cook time.

Cover the pan to keep in heat.

In the future, eat the onions raw, which will reduce the cooking energy by 100%.

By some mouthwash, you smelly onion eater.

I thought everybody knew that water boils in order to release any heat above its boiling point and so it would be useless to increase the flame.

I've always wondered, though, and even sort of supposed that all that extra heat travelling through the material you are boiling should raise the temperature a fraction of a degree. Has this been tested?

No, increase the heat means more energy consumption for the water will not exceed 100C at sealevel (it evaporates). I guess heat lost for the onions being cooler wont be expressive enough to be necessarily important to compensate with more heat & consequent energy consumption.

In order to conserve as much enegy as possible turning up the heat will most certainly NOT decrease the cooking time. Let's not get too technical about the issue. Water boils at 100degC (sealevel). Turning up the flame will just result in more heat being dissapated to the atmosphere. It is therefore crucial to keep the flame intensity just high enough to cook the onion. Here other factors do come in play like: at what temperature does an onion cook? Purity of the water. Physical design of the pot. Insulate agains heat loss (Allthough I would have said that if that were to be part of the solution, the insulation would have to be fitted BEFORE the whole experiment started. That way less energy is needed to bring the water to a boil in the first place). But as I said, let's not get too technical about it...

To summarise:

1.) Don't put more heat energy in than what is absolutely necesary.

2.) If insulation is to be part of THIS solution - see to it.

The correct answer is longer than you expect. Water will boil at a lower temperature if the pressure is reduced. The "sea level" bit in the question is the clue. You need only to to heat the pan to about 50 deg. c. then raise it to 30,000ft. It will boil with no more heat added, and should it go off the boil, go higher. What could be more economical? I've given some thought to getting it up. Attaching it to a private jet without telling the C.A.A. would be one way, but owners get a bit funny about a saucepan of tepid water and par boiled onions attached to their aircraft. Commercial flights, although not onion haters generally, get a bit sniffy about anything unusual around their aircraft, and anyway the external pre flight check would put paid to that. No the real solution is to contact N.A.S.A for an external place on a shuttle flight. They'd do it for money and with a transponder and locator beacon on the saucepan it could be recovered from the Pacific by a small frigate specially selected for the occasion. The onions by now would have cooled enough to eat straight from the pan. What could be a more economical way of heating your onions? T. F.

Unfortunately, just because the water is boiling at 50 C because of the increase in altitude, it doesn't mean the onion will still cook. You have to use a pressure cooker if you want a cup of tea up mount Everest as the tea will not infuse in water boiling at the lower temperature. It would be un-nerving however, to be drinking a cup of tea made this way as it would still be boiling in the cup even though it is at drinking temperature.

I too think you have misconstrued the question. It doesn't ask what you need to do to continue boiling the water with minimum energy input - it asks what you need to do to cook the onions.

Even if the question were "how to maintain the water boiling for as long as practical with minimum additional energy input", attachment to a fast-moving and inefficient mode of transport would not hack it. Better to insulate the pot well and give it to someone who is already planning to walk slowly up the adjacent mountainside.

Welcome aboard! I like your solution. It has all of the complexity and none of the convenience that make so many of the other (admittedly more practical) answers so absolutely pedestrian.

Water boils at 100deg C. The bubbles are hotter. Cover the pot with its lid which insulates the bubbles within the pot. (Closed System). Turn down the heat till just simmer. It will be 100 deg C entire contents of pot at greatly reduced energy input.

In my learned opinion there is really only one way to properly cook an onion.

Firstly, one must abandon all preconceived notions of commonality in one's palate.

One is then able to open ones' mind to the laws of conservation of flavour.

Required:

One onion (or more)

100,000 volt source

Glass vacuum and suspension chamber

8 gauge copper coil

THE RECIPE;

Suspend onion(s) in glass chamber. Reduce atmospheric pressure to -10 atmospheres. (Application of Noble gases is ok)

Wrap copper coil around glass chamber.

Apply current.

The RESULT:

Perfectly caramelized outer and inner layers (apply more current to crisp). Inner layers of individual layers will be steam cooked in own juices (no loss of flavour to water, frying etc).

You may also weld magnesium with this method.

Your recipe is remarkably similar to my great aunt Tessie' recipe. To be sure, please tell me the amperage and cooking time you have found yields best results. And what are you using for eye protection?.

Ah yes, thankyou. Most astute of you. I forgot to mention the welding glasses.

At 1/2 amp usually one or two nanoseconds works best.

My deepest apologies to you. Your recipe is indeed different. Aunt Tess was using 60 amps, and 20 min. (She had a tendency to overcook most things. Could be why she never married)

Onion a là Tesla - must try this next July 4th...