TOT: one for you scientists

[The Natural Philosopher]

cost some of the flavours get into the water. microwaveand no water is the BEST way to cook frozen peaks bar non.

[John Rumm]

I suspect there is not much in it, however if speed is the main concern then more boiling water will be faster than less.

If your peas are at freezer temperature (say -15 to -25) and you mix them with boiling water, the peas are going to warm up[1] and the boiling water will cool down until some equilibrium is reached. The less boiling water you add, the less its thermal heat capacity, and the more its temperature will fall in the process. You now need to return the mixture to boiling which, will require replacing the amount of energy in the water which was absorbed by the peas so far, plus an additional amount required to peas the remainder of the way. The amount of heat you need to put back into the water is dictated by the thermal mass of peas rather than anything much to do with the amount of water. However the more boiling water you had to start with, the more initial energy was available to pre heat the peas.

For the ultimate in speed pea cooking, chuck a load of boiling water into the bowl with the peas. Leave it for a little while for the temperature to equalise. Drain off the water, and then microwave the part cooked peas for a few seconds on their own to finish them off.

(microwaving the peas on their own from the start may be slightly slower (although probably the least energy inefficient) since the microwave energy is not absorbed by the ice quite as rapidly as by water, so you can short circuit that process with the boiling water from the kettle)

[1] An amount equal to heating ice from below freezing to freezing point, providing the latent heat of fusion to change the state of said ice to liquid, and then to heat that water further to the equilibrium point.

[David.WE.Roberts]

May have already been suggested, but why not put the peas in the kettle?

Cheers

Dave R

[Owain]

That's so you can't tell how much ice thaws off the peas (which you paid for by weight)

Admittedly I do occasionally come across 'dry' vegetables that benefit from a splash from a kettle to get the process started.

Owain

[ARW]

Anyone got any ideas what happens if you have a variable quantity of frozen peas?

Do frozen peas not have cooking instructions?

Should the time waiting for the kettle to boil not be part of the equation?

Did you like the peas?

[ARW]

Odd menu, but I'll try everything once:-)

[Gib Bogle]

This was not expressed well. Looking at the total heat heat budget, the amount of heat needed is that required to heat the peas, since the water starts at 100 deg, i.e. it contains all the heat it needs. The water is not boiling after it is added, because it is immediately cooled by the peas. My assumption (not necessarily accurate) was that the peas and water equilibrate quickly, i.e. after a short time (shorter than the time needed to bring the water to the boil again) peas and water are at the same temperature. Neglecting evaporation, the heat absorbed up to the boiling point is equal to that needed to heat the peas alone. The amount of evaporation increases with the amount of water added, since the temperature is higher (still less than 100) which means more water takes longer, but before boiling occurs I think evaporation is a small component, therefore the time difference will be small.

[John Williamson]

Squeak!

[polygonum]

Are garden peas the same as petit pois as regards cooking times?

[alan]

Add no extra water and just boil the water in the peas.

[Simon Brown]

Mine don?t.

[Simon Brown]

No, because that just sees more water stopping the microwave energy getting into the peas.

Yes, but that water stops the microwave energy from getting into the peas directly, so the peas will in fact heat up much quicker in the microwave with no added water at all.

That is still going to be slower than just microwaving the peas without any added water at all.

No, it will in fact be the fastest approach.

But that ice is part of the peas you want to heat.

But that takes longer than just microwaving the peas without any added water.

[Ian Field]

A bog roll soaked in bleach works quite well.

[Ian Field]

Mushy peas will - as long as it isn't scaled with lime.

[Ian Field]

Herbal tea is the only thing I can think of that smells nice but doesn't taste nice.

[John Rumm]

I have my doubts, since the water can impart lots of heat very quickly (admittedly this is cheating since you are excluding the kettle heating time for the water from the equation).

However since I have neither the inclination, and I don't like peas anyway I am not about to do the experiment to find out ;-)

So, whatever...

[Simon Brown]

Not as quickly as the microwave can with the much lower thermal mass of the peas with no added water.

I'm not convinced that it's true even when you do that.

Conduction from the hot water is going to be slower than when the microwave is heating the peas with no added water by absorption of the microwave energy.

[polygonum]

Even if you take the ultimate case of an infinitely large amount of boiling water it does take a finite time for the heat to get right through the peas.

And collecting up a portion of peas from the ocean of boiling water could well end up taking longer still...

[Martin Brown]

The latent heat of fusion of ice makes this impractical. You need a pan full of boiling water and a handful of peas and they would cook just like they used to do in boiling water in the old days before microwaves!

But not enough to be worthwhile. Assuming roughly hexagonal close packing of the peas you get a 3:1 peas to water ratio. The boiling water you add to cover them is not enough to get the peas to even melt.

Assuming peas are close to the specific heat of water and a freezer temperature of -18C you would need 3:2 peas to boiling water to end up with thawed peas in water just above freezing. Then you have to heat the entire mass up to 100C. Swings and roundabouts - to first order it makes no difference how much boiling water you add. In practice I suspect a small amount of liquid helps the oven couple to the peas.

It is possible that adding some liquid water will also prevent the peas at the top from dessicating, but choosing the right shaped container to cook them in would make a much larger difference to cooking time.

[Max Demian]

I by far prefer fresh peas when they are in season but Sainsbury's make them ridiculously expensive with their annoying BOGOF offers where you have to buy a bag of peas *and* a bag of broad beans (which they may not have in stock). Or halve the price one week and double it the next.