A Conversation for SEx - Science Explained

SEx: Cooking without a lid

Post 1

DaveBlackeye

When boiling stuff, I usually put a lid on the pan to keep the heat in, which allows me to turn the gas down.

But many recipes specifically tell you to cook uncovered. Why would this be? What possible difference could it make to the food?


SEx: Cooking without a lid

Post 2

sigsfried

Reduces the liquid increasing the flavor.


SEx: Cooking without a lid

Post 3

DaveBlackeye

I'm talking about boiling or simmering stuff, not reducing sauces etc.


SEx: Cooking without a lid

Post 4

Arnie Appleaide - Inspector General of the Defenders of Freedom

Hi, could you provide a specific example/food that you're preparing with this instruction?


SEx: Cooking without a lid

Post 5

DaveBlackeye

Hmm. Not off-hand, I'll have a look later. I seem to remember it applies to par-boiling potatoes bfore you roast them, sprouts, maybe ham? I definitely seen it in a load of cook books.


SEx: Cooking without a lid

Post 6

Mu Beta

A lower temperature won't deconstruct cells as quickly, allowing you to preserve flavour while making sure things are soft enough to eat?

Just a guess.

B


SEx: Cooking without a lid

Post 7

Alfster



And a bad guess...sorry!smiley - sadface

When a liquid boils it does so at one temperature. Simmering is still boiling and therefore it is at the same temperature as it would be if it was 'boiling'. The cooking phrase 'bring to boil and then turn down to a simmer.' is a bit misleading. Simmering is boiling erm...slower!

i.e. you are vapourising the liquid into a gas at a slower rate. It might be that the amount of heat input is lower and therefore does not turn the food to a mush, which maybe what you getting at.

By putting in a smaller amount of heat, the heat will more readily be converted into latent heat of vapourisation and boil off the liquid rather than putting in a lot of heat, when the heat input is higher than the mass transfer rate from the surface and therefore the heat not used latently is used as sensible heat which is absorbed by the food.

Water will then get into the structure and breakdown bulk of the food which makes it fall apart. (which is probably what you meant by cell deconstruction, MB?).

Also, if you put a lid on the pressure above the liquid would increase and therefore the boiling temperature would also increase. High pressure means higher temperature.

You do get some wierd two phase boiling systems with foods. That is when you get a pan filling with the bubbles and 'boiling over'. It is due to the surface tension of the liquid increasing due to the starches etc coming out of the food creating bubbles that do not break easily and therefore it keeps building up and up until the pan over flows with the bubble 'mass'.

Hope this helps!


SEx: Cooking without a lid

Post 8

Philious

ok! Is anything simple?


SEx: Cooking without a lid

Post 9

Squirrel


Well..

I was taught to put lid on the pan to 'keep the goodness in'.

This is based on the principle that many water soluble vitamins escape in the steam. By having a lid, the steam is condensed and returns to the cooking liquid with it's disolved vitamins.

The exceptions being: As mentioned, when 'reducing' (eg a sauce) one wishes to 'drive the water off'. & When not cooking in water, eg frying.

Does that make sense? I think it does.

Reduction in energy use (eg in pressure cooking) also makes sense in these days of climate change worry smiley - winkeye


SEx: Cooking without a lid

Post 10

Mu Beta

"A lower temperature won't deconstruct cells as quickly, allowing you to preserve flavour while making sure things are soft enough to eat?"

"Also, if you put a lid on the pressure above the liquid would increase and therefore the boiling temperature would also increase. High pressure means higher temperature."

Isn't that just saying exactly the same thing? It's more or less what I was getting at.

Keeping a lid off the pan means there is a lower temperature of boiling. All chemical processes in living cells work within a certain temperature range. The aim of cooking food is to soften it sufficiently to eat, kill any bacteria, but preserve a sufficient amount of the original cellular structure so that the food tastes good. If you cook - say - green beans, the cellulose cell walls are weakened, but the cooking time is so brief that the integral structure of the bean is unharmed.

Keeping the lid on makes it much more likely that the bean will be over-cooked and broken down. Plus it makes it harder to see what you're doing, which is probably another valid reason for boiling uncovered.

B


SEx: Cooking without a lid

Post 11

Squirrel



It also probably depends where you are and the climate..

Condensation is a problem with too much steam in the kitchen!

..I know, 'that's what extractor fans are for' - I refer you back to the original point about energy use.

So, why do saucepans have lids?


SEx: Cooking without a lid

Post 12

Blatherskite the Mugwump - Bandwidth Bandit

I can give you a perfect example of how you'd use both boiling methods on one dish.

Cooking with the lid on is most appropriate for when you want to retain moisture, and/or when you want to cook slowly, since it reduces the boiling temperature. Both of these are factors when you make a pot of spaghetti sauce... you want all the ingredients to simmer for a long period of time, but you don't want to boil it all off.

Cooking with the lid off is most appropriate for when you want to boil off moisture, and/or when you want to cook quickly. A good application for this is spaghetti noodles... the faster the noodles cook, the firmer they'll be. Boil noodles at a low temperature and they absorb too much water, turning to mush.


SEx: Cooking without a lid

Post 13

Arnie Appleaide - Inspector General of the Defenders of Freedom

why does cooking with the lid on reduce the boiling temperature?


SEx: Cooking without a lid

Post 14

Effers;England.

Sorry this is no way a scientific answer but on various cooking programmes I have heard it said that certain green vegetables, eg peas, should always be boiled with the lid off to preserve their colour. I'm sure someone else can provide the scientific reason for this.


SEx: Cooking without a lid

Post 15

sigsfried

Cooking with the lid of has a lower boiling temp because the pressure can't build up. Build up of pressure makes the bpt higher.


SEx: Cooking without a lid

Post 16

Traveller in Time Reporting Bugs -o-o- Broken the chain of Pliny -o-o- Hired

Traveller in Time smiley - tit on his head
"Thought the pressure difference is neglectable as boiling 'point' is dependend on concentration of solved substances as well.

Think the aromas escaping when the lid is off does contribute most to the cooking. "


SEx: Cooking without a lid

Post 17

DaveBlackeye

Interesting answers. I referred to my Leith's Cookery School book last night which said that if you leave the lid off, certain enzymes that would otherwise discolour the vegetables, are allowed to escape. I think this sounds like a made-up excuse to justify an age-old practice; I see no reason why these enzymes should evaporate with the water. I guess the same applies to "keeping the vitamins from escaping" - even if true, you'd be chucking the vitamins out with the water anyway.

Also, I don't subscribe to the theory that the water temperature is the same regardless of how much energy you put in. Clearly the (average) temperature of the water is always somewhere at or below 100 degrees, otherwise it would not be water. The more energy you put in, the higher the temperature and the more is turned to steam.

Anyhow, I seriously doubt that the slight increase in pressure in a covered pan would affect the temperature by much, pressure cookers aside. Perhaps counterintuitively, leaving the lid off allows a faster (hotter) boil, purely because it lets the steam escape rather than causing the pan to boil over, thereby letting you add more energy. Am I right?

And if so, what sort of temperature difference are we talking about? Would it really make any difference?


SEx: Cooking without a lid

Post 18

sigsfried

Stuff cooks slower without a pan lid. Last term at uni I hadn't got one of my pan lids I noticed that stuff cooked slower.


SEx: Cooking without a lid

Post 19

Blatherskite the Mugwump - Bandwidth Bandit

Yeah, I had that backwards. Sorry. That's what I get for double-checking my facts with unreliable internet sources. If I'd just thought about how a pressure cooker works for a second, I wouldn't have had to bother. The lid on increases temperature.

<>

That sounds like it should be the opposite, actually. Steamed vegetables always have better color and flavor than boiled, and you can't steam without the lid on.


SEx: Cooking without a lid

Post 20

Alfster

Mu Beta

<"A lower temperature won't deconstruct cells as quickly, allowing you to preserve flavour while making sure things are soft enough to eat?"

"Also, if you put a lid on the pressure above the liquid would increase and therefore the boiling temperature would also increase. High pressure means higher temperature."

Isn't that just saying exactly the same thing? It's more or less what I was getting at.

Keeping a lid off the pan means there is a lower temperature of boiling.>

No, that is the point keeping the lid on does not mean a lower temperature of boiling. A liquid at under the same atmospheric pressure boils at the same temperature.



No, it doesn't. Technically, the temperature would be slightly higher as the pressure above the liquid would be slightly higher.

When you heat water from room temperature and pressure the temperature of the bulk liquid will rise to as near 100DegC as the local atmospheric pressure will allow (this heating is called sensible heating ie. increasing the bulk temperature of the water). It will then remain at 100DegC. The heat being used to vapourise the water is latent heat of vapourisation/evaporation. You cannot change the temperature of a continually boiling liquid unless you alter the pressure above it or add something to the liquid (solid etc) to alter the actual boiling point)



It seems we are talking macro and micro. Micro being actual cell structure and MAcro being the matrix in which the cells are held creating the shape of the food itself.


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