For some strange reason, I thought that the purpose of adding salt to water destined for boiling was to increase the number of nucleation sites and thus prevent superheating. I’ve never noticed a difference in flavor between salted water and non-salted water when cooking pasta, which I attribute to the same reason that the boiling temperature isn’t raised to any noticable degree: There’s just not enough.
The main reason I’ve heard for using sea salt when cooking is the better flavor and, apparently more importantly, its ability to measure a “pinch” easier.
So if sea salt doesn’t really impart any health benefits, how about the mineral salts from caves (halotherapy and saltpipes)? My grandfather has a saltshaker labeled “Himalayan”, which he regularly touts as the healthiest salt on Earth…
I’m racking my brain, now. I know that Alton Brown explored the purpose of salt in pasta question on Good Eats, but I can’t remember what the conclusion was. I think it was that the pasta shed less starch out into the boil water if the water was salted, but I can’t swear that I’m remembering it right.
I’m a fan, but the only pasta-in-boiling-water lore I can remember was on the “MythSmasher” episode where he was investigating the practice of adding oil to the water. (I have to say that I don’t think he did a very good job on that particular question.)
When I went backpacking in Colorado at elevations of 9000-11000 feet, we made sure to bring the salt along to cook our pasta. IIRC, water boiled at that altitude at only 190º. Trying to cook pasta at that temperature took about twice as long before it was edible, and it was still rather chewy.
But when salt was added, it increased the boiling point enough to cook the pasta closer to normal time and to make it less chewy.
So Cal radio cooking guru Melinda Lee was just discussing this and says that the foaming issue is due to cheap, i.e. non-semolina wheat pasta and that salt won’t help the pot from foaming over. She maintains that it is strictly for the taste, but she also says that the water must be very salty. No actual proportions are given, but she says the pasta water should taste exactly like seawater. That’s too much salt for me to cook with.
“The main reason I’ve heard for using sea salt when cooking is the better flavor”
I’m not sure about pasta, but I do know the reason you add salt to anything where you have potatoes (such as soup or stew), is because they’re so absorbant. If the only salting occurs after they’ve been put with other ingredients, they will absorb all of the salt - thereby leaving your soup very untasty.
I think that made sense.
Anyway - perhaps that’s the same reason pasta’s salted as well?
As Cecil pointed out in the article, you would have had to add so much salt to make that happen as to make the pasta likely almost inedible from saltiness. :eek:
It may have been an old wive’s tale, but I was once given an explanation (from a fellow professional cook who was more experienced than I) on why we salted the water when making hard-boiled eggs.
The idea, he said, is that the eggshells allow water to pass through (osmosis, I suppose) and that salt dissolved in the water will also make its way through the heat-expanded pores in the shell. When the eggs have finished cooking and begin to cool, the pores in the shells shrink back to their original size, which is still wide enough to allow water to pass, but too small for the salt molecules to pass. This leaves the salt trapped between the egg white and the shell. Therefore, it’s much easier to peel the eggs.
I don’t know how accurate the science is, but I can wholeheartedly agree that eggs boiled in salted water are much easier to peel than those boiled in unsalted water.
Salted water makes blanched vegetables and pasta taste better. Thats good enough for me.
Does anyone have more accurate info on the boiling points of water of various levels of saltiness? I use a pretty hefty amount of salt for blanching, and I suspect that 2 or 3 degrees would really make a difference.
Here in the Philippines, we have an even more peculiar use of salt in cooking rice. We usually cook rice in a pot and when it has already boiled you would want to have it simmer for even cooking. For reasons that still escape me, a lot of people put salt on top of the pot lid (yes - on top of the lid, outside the container) while the rice is simmering -not many, probably a teaspoon. It’s supposed to help in cooking the rice.
Oh joy. After lurking for something like 6 or 7 years (OK, I read Cecil and haven’t been to the message boards since 2003) I have something constructive to add. Below is a column I wrote for a student newspaper in New Zealand about salt in cooking. To be posted in a few minutes once I get it all together is a series of letters I exchanged with a “natural salt” company about the presence and lack of impurities.
(The column was modeled after gurii like Cecil and ran for 3 years)
column starts
Q: Is it true that the reason we add salt to water when cooking is to make the water boil at a higher temperature?
Sounds good doesn’t it? If the salt water boils at a higher temperature then the food in the water will cook more quickly. Remember, as a rough rule of thumb, reactions occur twice as quickly for each 10 degree increase in temperature. (This doesn’t really apply to many of the changes that occur during cooking, but we’ll assume it is true for the moment).
It is true that dissolving things (like table salt) in a solvent (like water) increases the boiling temperature of the resulting solution (and decreases the freezing point). The reason for this isn’t easy to explain in the space I have, but, put simply: Boiling occurs when the vapour pressure of the liquid is greater than the vapour pressure of the air pressing down – this is why water boils at a lower temperature at altitude. Now adding salt (or sugar etc) to water decreases its vapour pressure so the solution must be more strongly heated for the vapour pressure to exceed that of the atmosphere. Adding salt decreases the vapour pressure because (crudely put) the same amount of energy now has to be spread around more molecules (the original water plus the added salt). Thus, we can see that the change in boiling temperature is proportional to how much salt has been added. But is it enough to make a difference when cooking?
In the case of water, the boiling point will be increased by 26 degrees times the fraction of added salt measured in moles. (The mole fraction of salt = (mass salt divided by 58) divided by (this same number plus mass water divided by 18). That is F = (mass salt/58) / [(mass salt/58 + mass water/18)]
Yeah, I didn’t think you’d understand. OK for …
1 litre of water the boiling point will increase by about 1/120th of a degree for each gram of salt you add. So If you add a heaped tablespoon of salt (lets say 60 grams) of salt to a medium pot containing 2 litres of water then the salt water will boil be elevated by 0.4 degrees to 100.4 (and the freezing point decreases by the same amount). This is nowhere near enough to make the slightest bit of difference to how quickly the food cooks, at best it will decrease the time of cooking pasta by around 15 seconds. So, the reason salt is added to water is for taste.
column ends
Oh. 'merkin readers should note that like 95% of the world I use degree C. (Actually I’m a chemist so I use K but you know what I mean).
Now, onto the salt company story.
Darn it. This was 3 years ago and all my email files are in off site archive. Never mind here is the framework of the story:
My local supermarket stocks a natural seasalt.
My training as environmental chemist coupled with general scepticism lead me to read the label.
They claimed the product was UNPROCESSED and UNREFINED (their capitals) sea salt and retained the full quota of minerals etc and even supplied a handy analysis sheet. A quick look showed that the minerals were not in the proportions that would be expected for real unprocessed sea water.
Arsenic (and every other element) is present in seawater. The label listed a few other elements that are found in seawater at levels below that of arsenic - e.g. selenium at 1/10th concentration of arsenic - but did not mention arsenic. Could be selective reporting I thought so I asked about arsenic. The company assured me there was none present. None? I queried. None at all they replied. So, I asked if that is true it means your product has been processed to remove the arsenic? (I also asked about uranium, present at 20x selenium).
At this point they flicked me on to their supplier. Turns out their supplier is the only salt manufacturer in the country. (They make it “fresh” from seawater in evaporation ponds). They hedged around a bit but eventually and curtly told me they supplied a product from partway along the refining process and that while it might contain arsenic it was at levels below those considered safe and therefore did not require reporting.
Of course this isn’t the point but try as I might I couldn’t get the “natural” company to admit that their product was refined and did contain arsenic and uranium. I did write to a food standards body but they said they only dealt with what was IN and not what was OUT unless the company had left out something they claimed was supposed to be there. Then I forgot about it. Must be time to see if it is still on sale and follow up.
Excuse my CS grade answer, but I don’t have any big science to back me up.
I add salt to the pasta water for flavour. It does take a lot of salt for the water to taste salty (a bit less than seawater taste, though). And it does make a big difference in the taste of the cooked pasta (don’t rinse it when you strain the water)
A few thoughts. IANAChemist, but I am a pretty good cook.
Yes, among most foodies, the reason to use unrefined sea salt is flavor rather than health benefits. I’m in the minority who think it’s mostly psychological. To my palate, at least, the difference in flavor is quite small and generally dwarfed by other flavors in the dish.
Yes, salt will provide nucleation sites to avoid superheated water. This is useful, because otherwise your pasta become the nucleation sites and can cause the pot to boil over. But, to get this effect, you add the salt after the water has come to a boil. It’s the granules which bring the dissolved water vapor out of solution. If you dissolve the salt in the water at the beginning, it doesn’t help.
No, you don’t add salt to prevent foaming. For that, you use a little oil. I agree with Melinda Lee that this is unnecessary with good semolina-only pastas and, in fact, I don’t add oil to my pasta cooking water. The only exception is stuffed pasta, e.g., ravioli, and the reason isn’t to prevent foaming but rather to keep them from sticking together when drained.
IMHO, adding salt to the pasta cooking water also improves the flavor of the pasta considerably. I’ve forgotten occasionally and notice the difference immediately. I use what I’d call a moderate amount, about a tbsp for three quarts of water (enough to cook a pound of dried pasta).
You note five taste sensations, implicitly defining taste as the sensory input from taste buds. And, of course, differentiated from smell. But there are several other demonstrably important components to taste, especially if defined as the sensory input from the mouth. There is spiciness, which does, in fact, directly impact taste buds. There is heat and cold, which measurably change the taste sensation of food, both by suppressing some flavor and enhancing other, but also just by the hot/cold sensation. There is aromaticity for things such as menthol and methyl salicylate, which produce an effect similar to cooling. And there is texture, a critically important attribute of food that is intensely felt when chewing. All these contribute to taste but are repeatedly ignored in discussions of taste.
Generally, I enjoy your columns and find them objective, rational, and balanced.
(Note this calc also works for freezing point depression)
Not sure where the error came from.
Must have been in the last step. I suspect I used the earlier figure I wrote of 60 g salt but put it in 1 litre instead of 2L. Thanks for spotting that.
The actual calcs for anyone who wants to follow this for themselves and use other values:
delta T boiling = [( R * T^2)/L] * Nb
R = gas const = 8.314 J K-1 mol-1
T = boiling pt in K = 373 for water
L = latent heat of vaporization = 40896 J mol-1
Nb = mol fraction
delta T = [(8.134 J K-1 mol-1 * 139129 K^2) / 40896 J mol-1] * Nb
delta T = 28.3 K * Nb
I wrote 26 deg instead of 28. Dunno what was with that. Must have rounded in the first calc.
So for 30g NaCl = 30 g / 58 g mol-1 = 0.52 moles
For 1000g water = 1000 g / 18 g mol-1 = 55.56 moles
(In think earlier I must have used 60g salt here to be out by factor of 2).
mol fraction = (0.52) / (0.52 + 55.56) = 9.3 e-3 = 0.0093
So delta T = 28.3 * 0.0093 = 0.26 deg
All you need to know to repeat this calc for any other substance is the latent heat and the molecular mass. Two useful ones are ethanol: mol mass 46 g mol-1 latent heat 43000 J mol-1 and ethylene glycol: mol mass 62 g mol-1 latent heat 66000 J mol-1.