Nutrients lost in cooking - how much? - VeggieBoards
Forum Jump: 
 
Thread Tools
#1 Old 09-30-2010, 08:41 AM
Beginner
 
kari_lynn222's Avatar
 
Join Date: Jul 2010
Posts: 554
Does anyone know how much, if any nutrients are retained in cooking vegetables? There are several veggies dishes that I enjoy very much, but require cooking. Sometimes even roasting in the oven for 45 minutes.

I am just curious, do you think that there are even nutrients left in the vegetables at that point? I just feel like cooking them completely renders them useless in terms of vitamins and minerals, especially the ones that require long cooking times... but don't want to limit myself to strictly raw.

What are your thoughts? Any nutrition experts??

-Kari, Minnesota mommy, wife and vegetarian. treatyourbodyright.blogspot.com
kari_lynn222 is offline  
Sponsored Links
Advertisement
 
#2 Old 09-30-2010, 08:55 AM
Beginner
 
runnerveggie's Avatar
 
Join Date: Jul 2010
Posts: 1,547
I don't know the answer, and it depends on the particular vegetable, how it is cooked, and what it is cooked with. But, I do know that while cooking can reduce some nutrients, it makes many nutrients more accessible to the body. When I have more time I'll look for some more specific info.

ETA: Harvard article on microwave cooking and nutrition - this lists a couple examples. For example, vitamin C breaks down when exposed to heat (microwave or otherwise), but boiling carrots actually increased their carotenoid content.
runnerveggie is online now  
#3 Old 10-05-2010, 02:40 PM
Banned
 
Join Date: Oct 2001
Posts: 10,764
Indeed, boil or steam a vegetable, and lots of its nutrients leave the solid portion of the cooking vegetable, and migrate into the cooking water. If you taste the water, this becomes obvious. Just steam some carrots and taste the water. The water will have a sweet taste, from the sugar in the carrots. Same with beets. Steam some sliced or diced potato - the water will become viscous with starch, that left the potato, and is migrated to the water. It is recommended that when you cook vegetables, you steam them in a small amount of water at the bottom of the pot, and that you consume the water. In some cases, more nutrients are in the water than in the solid vegetable. It makes little difference if you put the vegetables in the pot, or raise them above on a steaming rack - the nutrients will go into the water just the same. You must consume the water. There are a few exceptions. Some foods have toxic or irritating constituents, which leave the vegetable and go into the water. This is the case with artichokes, and (dry) beans with red, brown, or black skin. Especially the red skins. The skins contain irritating amounts of tannic acid. It migrates to the water. It is better to discard the water. That is why I always get beans with white skins - so I can serve the beans and the water. The water gets a substantial amount of bean protein in it. You can see this if you put the water in the fridge. You will see a substance that congeals, due to the protein or starch in it becoming a gel rather than a sol, at cooler temperatures.

If all these macronutrients go into the water, one could easily hypothesize that much of the micronutrients also migrate into the water. And in fact, this is what nutritionists say is what happens.

Because oil will reach a higher temperature than water, frying a vegetable subjects them to much higher temperatures than steaming, and not only do nutrients leave the vegetables and go into the oil, but more micronutrients are decomposed, due to the higher heat.

Baking also subjects vegetables to slightly higher heat than steaming or boiling, because air will reach a higher temperature than water. However the water contained in the vegetables, moderates the temperature. Frying is worse, becuase it causes the water to leave the vegetable and be replace by oil, allowing the solid part of the vegetable to reach temperatures as hot as the oil. We are talking over 400 degrees F (the point at which oil smokes, or ignites), while water-cooked vegetables reach only a little above 212 degrees F (the boiling point of water).

And yes, cooking also makes some nutrients more easily accessible to human digestion and assimilation. It many cases it partly digests them, meaning we have to do less digestion work (energy consuming), and thus can get more net calories from the vegetable (energy providing). Same thing goes for making the amino acids in some proteins, more available to us. So yea, you wouldn't get much nutrients from eating dry bean flour mixed with water. But cook the mixture, and eat both the water and the bean flour, or eat both beans and the water you cook them in, and you get more nutrients, than if you cook the beans in water and discard the water. Assuming you have white beans, that you can do this with.
soilman is offline  
#4 Old 10-05-2010, 09:33 PM
Beginner
 
Doktormartini's Avatar
 
Join Date: Jul 2007
Posts: 3,457
Calcium is water soluble so if you boil a calcium rich food in water and don't use the water you're losing a lot of the calcium. Many phytochemicals are also lost during the heating process.

“May all sentient beings be free of pain and suffering.  May all sentient beings experience eternal joy and happiness.  gate gate pāragate pārasaṃgate bodhi svāhā.”
http://www.facebook.com/doktormartini
http://twitter.com/#!/MartyBaureis
http://doktormartini.tumblr.com

Doktormartini is offline  
#5 Old 10-14-2010, 08:14 AM
Beginner
 
BellaVega's Avatar
 
Join Date: Oct 2010
Posts: 5
Is there a better way to cook a vegetable besides steaming them that would keep the nutrients and vitamins in the food? I always thought steaming was good because it was more healthier than frying in oil. What about grilling vegetables? Would that retain more of the nutrients or perhaps roasting? Or is raw the best way although not practical with some vegetables like potatoes. -Bella Vega, Golden Rule

Bella Vega, Golden Rule
BellaVega is offline  
#6 Old 10-14-2010, 10:49 AM
Beginner
 
Doktormartini's Avatar
 
Join Date: Jul 2007
Posts: 3,457
Raw is the best way If you are raw, you most likely won't eat potatoes but most raw fooders substitute Jicama in place because you can eat them raw and make fries out of them even.

“May all sentient beings be free of pain and suffering.  May all sentient beings experience eternal joy and happiness.  gate gate pāragate pārasaṃgate bodhi svāhā.”
http://www.facebook.com/doktormartini
http://twitter.com/#!/MartyBaureis
http://doktormartini.tumblr.com

Doktormartini is offline  
#7 Old 10-14-2010, 09:05 PM
Banned
 
Join Date: Oct 2001
Posts: 10,764
Doktorm
Quote:
If you are raw, you most likely won't eat potatoes but most raw fooders substitute Jicama in place because you can eat them raw and make fries out of them even.

I can't think of any recipe where I would want to substitute a jicama for a potato. Besides costing about 3 times as much per pound, and looking a little bit like a potato, the flavor has no relationship.Jicama is much lower in calories, having almost none. Potatoes are an easy to grow staple that one can depend upon for calories. I don't know how jicama is grown. Raw, jicama it has a nice crunch, something you rarely look to a potato for. Lots of water - like celery or water chestnut. A slice of jicama is a nice, slightly sweet, rigid device to scoop up dip with, like celery, but has little calories of its own. But if you are concerned about being able to make sure you have enough calories to meet your energy requirement, you would definitly want to grown potato, but not jicama. I just don't see how jicama is any kind of "substitution" for a potato.

"Raw fooders substitute jicama... because you can make fries out of them?"

Not making sense. As soon as you make fries out of them, and eat them, then you are not a raw fooder anymore.
soilman is offline  
#8 Old 10-14-2010, 09:56 PM
Beginner
 
RBG09's Avatar
 
Join Date: May 2009
Posts: 236
A lot of people may disagree with me on this, but I actually think one of the best ways to prepare vegetables is to heat them quickly inside the microwave. There is a lot of fear over microwave cooking, but when you consider the small amount of time you have to have vegetables in there to heat them up, you're probably losing LESS nutrients than with other cooking methods that require you to heat them longer. Just think about it - if the main cause of lost nutrients is heat damage and transmission into water, wouldn't a microwave, which is the fastest, and requires very little water, be a really good method? That's the way I look at it.
RBG09 is offline  
#9 Old 10-15-2010, 07:06 AM
Banned
 
Join Date: Oct 2001
Posts: 10,764
Quote:
Originally Posted by RBG09 View Post

A lot of people may disagree with me on this, but I actually think one of the best ways to prepare vegetables is to heat them quickly inside the microwave. There is a lot of fear over microwave cooking, but when you consider the small amount of time you have to have vegetables in there to heat them up, you're probably losing LESS nutrients than with other cooking methods that require you to heat them longer. Just think about it - if the main cause of lost nutrients is heat damage and transmission into water, wouldn't a microwave, which is the fastest, and requires very little water, be a really good method? That's the way I look at it.

Possibly but there are few more factors to consider. The amount of nutrients that migrate from solid part of vegetables to the cooking water, probably has little to do with the amount of water you are cooking the vegetables in, or whether the vegetables are sitting in the water or on a platform above it. To support this claim, I did the following experiment. I cooked same kind and same amount of vegetables in small amount of water (1/3 cup), and in large amount of water (2/3 cup), then tasted the water. The water from the vegetables cooked in smaller amount of water, had a much stronger taste than the water from the vegetables cooked in the larger amount of water, suggesting that more nutrients do not leave the vegetables, if they are cooked in a larger amount of water. Most likely the same amount of nutrients leave the vegetables, either way. However the time did have a great effect on the taste of the water. The longer I cooked, the stronger the water tasted.

I have read that temperature effects nutrient loss. Higher temp, more loss. However water will not go more than a hair above 100 degrees C (its boiling point) and steam from boiled water is about the same temp. Water that is gently simmering is the same temp as water that is rapidly boiling. From what I can tell, the food in a "slow cooker" is kept at just about the boiling point of water. It is not kept at a lower temperature than that. That is why "slow cooking" is a "slow cooker" is a misnomer, and is really just longer cooking. One way to increase water temp is to put the water under pressure, use a pressure cooker. The temperature of the water under pressure (and any steam that occurs) may reach 120 degrees C. You will probably not have much greater nutrient loss due to pressure cooking, because the cooking time is shorter, making up for the slightly higher temperature. However certain nutrients may show faster acceleration of decompostion, as you raise temperature, than other nutrients. The big change is not between pressure cooking and regular steaming or boiling, but between cooking in water and cooking in oil. Temp of oil is much higher than temp of water. 200 degrees C or more, as compared to 100.

Microwaving also raises water temp (of the water inside the vegetables) slightly higher than ordinary boiling of water over a flame. However this may possibly be compensated for, by the shorter cooking time. All in all, I think microwaving is about the same as steaming or boiling. It does appear that if I cook vegetables in the same amount of water, those cooked in the microwave (inside a plastic container with a cover, with holes in the top to allow steam to escape) have less strongly tasting water. This is moot, if you consume the water. If you cook in a coverd plastic container, make sure the cover is microwavable.

The main disadvantage of microwaving in plastic is that more toxic substances enter the food - toxic substances are leached from the plastic. The gov regulators say if the container is microwavable, the amount is negligable. I am skeptical. I would suggest microwaving in pyrex glass or ceramic containers.

Stainless steel allows only a small amount of iron and nicke to enter food. The iron is at non-toxic levels (our bodily iron requirements exceed the amount leached from the steel). Nickel is also at a very safe level. You should avoid scrubbing the pots with abrasive scrubbers, or if you do, wash them with detergent and water afterwards, and rinse very very thoroughly. You should gnerally not need to use abrasives on stainless steel after steaming or boiling. Only after frying, does food stick.

Boiling and steaming cook by raising the natural water inside vegetable, to the same temperature as the water they are steamed or boiled in. This causes cell walls to break down, and nutrients, and flavoring substances, to leave the vegetables, and go into the water. Microwaves cook by causing the natural water inside vegetables, to boil (you should never microwave dehydrated food, as this will both decrease the life of the oven, and cause excessive microwave leakage from the oven). This brings the vegetables to the same temperature that immersing them in boiling water or steam brings them to, and has the same effect, except that when boiling water or steam, the temp of the vegetables rises, from the outside first, then after a time the vegetable piece gets hotter toward the center. Microwaves penetrate vegetable pieces, and the outside and center of the vegetable pieces get hot at about the same time. This is why they cook faster in a microwave oven. Both the outside and the inside are cooked for about the same length of time. With boiling or steaming, the outside of the veg piece ends up being cooked for a longer time than the inside. This can be mostly avoided, made negligable, by cutting into small pieces before cooking. Microwaving allows you the luxury of not having to cut vegetable pieces as small. To me that is not a big deal as I dice vegetables very fast using a chef's knife and cutting board. Cleaning these after dicing vegetables is a matter of wiping the board with a damp cloth and rinsing the knife off under running water for a moment, then drying and putting in a wooden knife holder (to protect the knife edge). Quality stainless steel knives, with houshold use, only need to be sharpened once a month or so. While it does require a bit of know-how, timewise, this is a matter of running a whetstone over the knife edge, a few times, then cleaning the knife.

When you bake in a conventional oven the air in the oven gets much higher in temp than the temp of boiling water, however, the water inside the vegetable you are cooking will not get any higher. Only the dried out edge of the veg will get higher in temp. Animal flesh, on the other hand because it contains so much fat, can get a bit higher in temperature, as the fat will reach higher temp than water will reach, and as the water inside the flesh boils away, the dry solids of the flesh reach the temperature of the fat. We are talking about 200 degrees C, or about the same temperature as the air in the oven, 150 to 200 degrees C.
soilman is offline  
#10 Old 10-15-2010, 11:34 AM
Beginner
 
delicioso's Avatar
 
Join Date: Aug 2010
Posts: 2,945
I try to eat about 50% raw, but I will never go all the way. I love cooked food too much. One of my favorite meals is steamed kale and cornbread dipped in the water. Nothing goes to waste.
delicioso is offline  
#11 Old 10-15-2010, 12:09 PM
Beginner
 
RBG09's Avatar
 
Join Date: May 2009
Posts: 236
Well soilman, you've definitely devoted a lot of time to figuring all this out.

I think I microwave vegetables in a fairly safe way. I avoid plastic completely in the microwave, I always put food in a microwave safe glass dish. As long as you follow some simple safety guidelines I think it's more than acceptable, and it definitely wins when it comes to convenience. I eat more vegetables now than I did when I cooked them on the stove, so it's actually increased the amount of veggies I consume, and that's a definite advantage.
RBG09 is offline  
#12 Old 10-15-2010, 01:29 PM
Banned
 
Join Date: Dec 2007
Posts: 7,160
I always cook vegetables in spices, so that I can eat everything in the pan and don't have to throw away the water they were cooked in.
Earthling is offline  
#13 Old 10-16-2010, 11:21 AM
Beginner
 
Doktormartini's Avatar
 
Join Date: Jul 2007
Posts: 3,457
Quote:
Originally Posted by soilman View Post

Doktorm

I can't think of any recipe where I would want to substitute a jicama for a potato. Besides costing about 3 times as much per pound, and looking a little bit like a potato, the flavor has no relationship.Jicama is much lower in calories, having almost none. Potatoes are an easy to grow staple that one can depend upon for calories. I don't know how jicama is grown. Raw, jicama it has a nice crunch, something you rarely look to a potato for. Lots of water - like celery or water chestnut. A slice of jicama is a nice, slightly sweet, rigid device to scoop up dip with, like celery, but has little calories of its own. But if you are concerned about being able to make sure you have enough calories to meet your energy requirement, you would definitly want to grown potato, but not jicama. I just don't see how jicama is any kind of "substitution" for a potato.

"Raw fooders substitute jicama... because you can make fries out of them?"

Not making sense. As soon as you make fries out of them, and eat them, then you are not a raw fooder anymore.

Yes you cut the jicama into stips like fries and eat them raw. You don't heat them. You can also use it to make mashed potatoes.

When I ate fries, I liked them more crunchy so the jicama is fine for me.

“May all sentient beings be free of pain and suffering.  May all sentient beings experience eternal joy and happiness.  gate gate pāragate pārasaṃgate bodhi svāhā.”
http://www.facebook.com/doktormartini
http://twitter.com/#!/MartyBaureis
http://doktormartini.tumblr.com

Doktormartini is offline  
#14 Old 10-19-2010, 09:01 AM
Banned
 
Join Date: Oct 2001
Posts: 10,764
"Yes you cut the jicama into stips like fries and eat them raw."

These would taste like jicama, not liked fried potatoes. One is not a substitute for the other. Also raw jicama provides much less energy, and much less building material, than cooked potatoes.
soilman is offline  
#15 Old 10-20-2010, 05:16 AM
Beginner
 
rabid_child's Avatar
 
Join Date: Jul 2003
Posts: 12,283
Let's all just agree that nothing can replace a nice, fried potato in flavor or texture or for satisfying a craving for something nice and greasy and starchy, k? Great.

Now that that's settled.... some nutrients in produce are MORE available once heated, like licopene in tomatoes. I think overall, the most important part is that you're going to eat your veggies. For me, I just don't eat a lot of raw veggies. They upset my stomach a good bit. Eating them in conjunction with cooked food mitigates this effect (i.e. a salad with pasta), but just eating raw veg causes a ton of pain. Ergo, if I just had to eat my veggies raw, I'd probably eat a ton less of them and it's better to eat them than not, cooked or no. That said, less processed is better. Lightly steamed fresh peas > canned peas. Sauteeing is better than boiling, and leaving things "tender crisp" is better than cooking the life out of them.

http://megatarian.blogspot.com
rabid_child is offline  
#16 Old 10-20-2010, 07:46 AM
Banned
 
Join Date: Oct 2001
Posts: 10,764
rabid_child
Quote:
Sauteeing is better than boiling

I disagree. I could be mistaken, but since oil will reach over 200 degrees C (over 400 degrees F), and water only 100 degrees C (only 212 degrees F), sauteeing will bring part or all of your vegetables up to 200 degrees, decomposing more nutrients. Further, the heated oil itself may be more damaging to you than non-heated oil, esp if the oil is brought to such a high temp, as 200 degrees C, as it normally is when sauteeing (same as with frying, there is really no difference, the oil penetrates the vegetables, replaces much of the water, and brings the veg temp up toward the oil temperature). The longer you sautee, the worse it is. Esp if you sautee in an uncoverd pan, so that the water in the vegetables can evaporate away. Also, the oil itself may possibly become carcinogenic. The main difference between ordinary frying and sauteeing is that you throw some excess oil away, after you finish frying. But the amount that enters the food, and the changes it causes in the food, is about the same for sauteeing or frying. Pan fry, deep fry, sautee - all are about the same. Even "bake fry" where you light brush oil over vegetables before baking, is only slightly better than the other 3, as most likely the oil temp does not reach quite as high (the air is not as hot as the oil over a direct flame or electric burner), and you use less oil. If you bake fry in a puddle of oil - no good.

Stir-frying - where a large amount of water is continually dumped into the wok, and only a small amount of oil is used, and the pot is kept covered much of the time - to allow the vegetables to steam in the steam arising from the water - is a compromise between sauteeing and steaming. The vegetables reach a higher temp than when cooked in plain water, esp their surface layer, but not as high as when cooked in plain oil. Ideal cooking method for preservation of nutrients is boiling or steaming and consuming the water, or microwaving.

Anything you make crisp, with heat, you destroy more nutrients in, and create more harmful substance in, than something you simply make tender. Crispiness is a result of removing nearly all the water, and allowing the temperature to go very high. Crisp as in raw-crisp, is obviously a different story.

If you mean briefly sauteeing, as compared to long frying, yes, it is better, but brief deep-frying is not a lot worse than brief sauteeing.
soilman is offline  
#17 Old 10-20-2010, 02:13 PM
Beginner
 
rabid_child's Avatar
 
Join Date: Jul 2003
Posts: 12,283
Quote:
Originally Posted by soilman View Post

Anything you make crisp, with heat, you destroy more nutrients in, and create more harmful substance in, than something you simply make tender. Crispiness is a result of removing nearly all the water, and allowing the temperature to go very high. Crisp as in raw-crisp, is obviously a different story.

No, this would be charred. Charred is not the same as crisp. Crisp means closer to raw than cooked. Basically, heat 'til bright green (or bright orange, or bright whatever color you're cooking). When I sautee veggies, I take a large pan, heat a little oil (and likely some garlic), toss in the veggies, swish 'em around a little bit, add a bit of water, drop the lid on it and leave it for a few minutes, then eat.

Just because oil CAN reach 200 degrees doesn't mean you have to cook with it that hot.

And you have to consider, people who boil vegetables do not routinely drink the water afterward. In fact, I'd assume the vast majority of people who do boil veggies, discard the water afterward. The "best solution" is useless if people won't do it.

Quote:
Originally Posted by Peggy O'Shea Kochenbach, registered dietitian View Post

The ideal way to eat vegetables and preserve the biggest amount of nutrients is to eat them raw, but if you are cooking your vegetables, try steaming them either in a steamer or in the microwave. Stir frying also can be a good way to preserve the nutrients. Always use as little water as possible, and avoid boiling vegetables, as the vitamins, minerals and phytochemicals will escape into the water rather than remaining in the vegetables. Also try to keep the vegetables in larger pieces when cooking. The more their surface is exposed to air and/or water, the more likely you will lose those important vitamins and minerals.

Quote:
Originally Posted by Cornell Cooperative Extension View Post

Cooking methods that minimize the time, temperature, and amount of water needed will help to preserve nutrients. Steaming is a great way to cook vegetables quickly and retain valuable nutrients. Microwave cooking is also good because it uses minimal water, and the cooking time is very short. Stir frying is another way to quickly cook a variety of vegetables.... Cook vegetables until crisp. Don't overcook.

Quote:
Originally Posted by www.fruitandveggieguru.com View Post

Microwaving is one of the best ways to prepare vegetables. Boiling probably is the worst way. When you microwave, use little water and be sure to cover the container to keep the steam in the dish. Experiment to find the least amount of time to microwave the vegetable to heat it through completely.
Think of the other ways you prepare vegetables that require little time and water. Steaming is an excellent way to prepare vegetables. You lose hardly any of the nutrients in the water.
Try eating the vegetables a little on the tender/crisp side.
Stir-fry – because it is quick – also is one of the more healthful ways to prepare vegetables. Remember to avoid cooking until the vegetables are mushy.


http://megatarian.blogspot.com
rabid_child is offline  
#18 Old 10-20-2010, 03:10 PM
Beginner
 
Doktormartini's Avatar
 
Join Date: Jul 2007
Posts: 3,457
Lycopene is more available in tomatoes in cooking and that is the most often used example but there are a number of things with this. First, lycopene is not an essential nutrient so you're not going to die if you don't get it. However, it is an antioxidant and has many health benefits so it should be consumed. While cooking does raise the lycopene output in tomatoes, it does so at the loss of other things (some vitamins and phytochemicals). Also, even if you eat the tomato raw you're still getting some of the lycopene and some is better than not eating it at all. And lastly, lycopene is in lots of other things besides tomatoes. It's in watermelon, which is most often eaten uncooked.

Point being? You can eat both raw and cooked veggies, however I still believe raw is best.

“May all sentient beings be free of pain and suffering.  May all sentient beings experience eternal joy and happiness.  gate gate pāragate pārasaṃgate bodhi svāhā.”
http://www.facebook.com/doktormartini
http://twitter.com/#!/MartyBaureis
http://doktormartini.tumblr.com

Doktormartini is offline  
#19 Old 10-20-2010, 04:28 PM
Banned
 
Join Date: Oct 2001
Posts: 10,764
rabid_child
Quote:
when I sautee veggies, I take a large pan, heat a little oil (and likely some garlic), toss in the veggies, swish 'em around a little bit, add a bit of water, drop the lid on it and leave it for a few minutes, then eat.

The addition of water and use of a cover makes what you are doing more like stir frying than like sauteeing. The water keeps the oil and the vegetables in it from getting as hot as it would otherwise get if there was no water. Some of the excess heat is absorbed by the water and is used to turn the water to water vapor (to boil) rather than used to increase the temp of the oil.

Quote:
just because oil can reach 200 degrees doesn't mean...

It is hard to keep the temperature under 175 or so. Overwhelmingly, it is the mixture of substances in the pot or pan, the substances themselves, and their amount, that decides the temperature they will reach. Oil for frying or sauteeing (but not for deep frying) reaches about 200 degrees C in a matter of a couple of minutes, on a cooking burner. Lower the burner, and it takes a little longer, but it still reaches the same temp. A big pot of oil for deep frying takes maybe 10-15 minutes to reach 200 degrees C. If you turn down the burner, it takes maybe 25 to 30 minutes, but it reaches the same temp - the max temp that it will reach, before smoking, burning off. If you take the pot off the burner before that happens, you can keep the temp a bit lower, but for all practical purposes, not a lot lower. Mayber 175 instead of 200. If you are using just a few tablespoons of oil in a pan to fry or sautee, it is a matter of only seconds before the temperature changes from 150 degrees to 200 degrees.

A quarter of a cup or so of water, for steaming vegetables, reaches about 100 deg C in a couple minutes. Once it reaches about 100 degrees C, it stays at that temp. As soon as you see the water start to simmer, it means it has reached about 100 degrees C. Bring the water to a hard boil - and it is still 100 degrees C. Only way to increase its temp above the boiling point is to use a pressure cooker. Why? Because if water reaches higher than about 100 degrees it isn't water any more, it is water vapor. If it is water vapor, it can't stay in the pot any longer (unless the pot is totally air-tight, which it won't be, unless it's a pressure cooker). So it can't heat your food. The only way to lower its temp below the boiling point is to remove the source of heat when the water reaches the temp you want it to be.

An analogy: heating a pot of water is much like filling a pot with water from a faucet. The amount of water, the volume of water in liters, can't be more than the size of the pot in liters. It can be less, but only if you turn the water faucet off at some point (or if you put the water in so slowly, that the water actually evaporates faster than the pot fills). The liters are like the degrees C. The faucet is like the burner. If the faucet runs slower, the liter amount of water in the pot will take longer to reach the liter size of the pot, but once the liters of water in the pot reach the liter size of the pot, the amount of liters of water in the pot stays the same. Any extra just pours over the side. To keep the water amount less than the liter size of the pot, you have to shut off the faucet before the pot gets filled (analagous to shutting off the burner).

For heat, if the burner is smaller, the temp of the water in the pot will take longer to reach the boiling point of water, but once the water temperature reaches the boiling point, the temperature of the water in the pot stays the same, at the boiling point of water. The only way to keep the temp below 100 degrees is to turn off the burner (or turn it down to practically nothing) before the water reaches 100 degrees C. Then when the temp gets too low, you turn the burner back on again.

Things work similarly with oil, except it is the smoking point rather than the boiling point that controls the oil temp. That is why deep fryers have thermostats, and people sauteeing lift the pot off the burner - to keep the temp around 175 instead of 200. The oil doesn't smoke, and it is slightly lower than 200 degrees, but its temp is still much higher than the boiling point of water.

The water or oil in the pot keeps the temperature of whatever is in the water or oil — from getting any higher or lower than the temperature of the water or oil.

Oh, one more thing regarding the analogy. Imagine that pot having a tiny leak in it. Water leaks out very slowly, at a constant rate, but the rate is much slower than the normal speed of the faucet, and as well, turning the faucet as slow as you can make it go, won't make it go slower than the leak in the pot. To make the pot have a net loss of water, you have to turn the faucet completely off. Once you turn off the faucet, the number of liters of water in the pot slowly gets less and less. Analgous to turning off the burner, and the temp of the water in the pot slowly gets lower and lower. Turn the faucet (burner) back on, as slow as it will go, and the liters of water (temperature) gets rapidly higher. The leak is small and constant. The faucet is variable. So it is hard to keep the water at a steady temperature, with the burner on. To keep the water hovering around a certain tempearture, you have to turn the burner on and off by hand or by using a thermostat.
soilman is offline  
#20 Old 10-20-2010, 05:06 PM
Beginner
 
penny79's Avatar
 
Join Date: Nov 2005
Posts: 4,947
Quote:
Originally Posted by Doktormartini View Post

Lycopene is more available in tomatoes in cooking and that is the most often used example but there are a number of things with this. First, lycopene is not an essential nutrient so you're not going to die if you don't get it. However, it is an antioxidant and has many health benefits so it should be consumed. While cooking does raise the lycopene output in tomatoes, it does so at the loss of other things (some vitamins and phytochemicals). Also, even if you eat the tomato raw you're still getting some of the lycopene and some is better than not eating it at all. And lastly, lycopene is in lots of other things besides tomatoes. It's in watermelon, which is most often eaten uncooked.

Point being? You can eat both raw and cooked veggies, however I still believe raw is best.

agreed, lycopene is brought up, but how many thousands of nutrients are damaged in that cooked tomato. i'm not going to change how i eat and introduce cooked foods in favor of ONE nutrient out of thousands or more.
penny79 is offline  
#21 Old 10-20-2010, 09:26 PM
Banned
 
Join Date: Oct 2001
Posts: 10,764
Jeez why are you areguing whether to eat tomatoes raw or cooked? One of my favorite dishes is raw tomatoes with cooked tomato sauce. My cooked tomato sauce has raw cilantro added after it cools down. Then I pour it over tomato slices, or cherry tomatoes, cut in half, and presented face up. Incidently, my cooked tomato sauce is made with tomatoes just cooked through. Takes about 3 minutes to cook. Garlic, tomatoes, touch of hot pepper, sesame oil, olive oil, sugar, salt. Throw everything in pan except cilantro and oil (use just a tiny bit of the oil during cooking, add the rest later - not too much. Cook tomatoes until just cooked thru. You don't need to put any water in the pan. The 'matos steam in their own juices. After it cools add cilantro and a tiny bit of sesame tahini to thicken.
soilman is offline  
Reply

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off