Though, actually, apparently adding salt decreases the “specific heat capacity” of water, so that increasing it by N degrees requires less heat to be added (and therefore takes less stove time). The numbers in this article suggest that this makes a larger difference than the increased boiling point would.
(Though, again, the effect size seems to be epsilon for realistic amounts of salt people would add.)
The article has an egregious typo where they say “The pot containing a 20% salt concentration will heat up over 25 times faster”. I think they meant “over 25% faster”, which is either true or close-to-true. I’m not sure about the conclusion that cooking time goes (slightly) down; I think they’re holding total-mass fixed, but if we’re talking about “adding salt” then we should hold water-mass fixed instead, which adds onto the boiling point elevation effect and might tip the balance. I didn’t do the calculation because it’s entirely pointless. :-P
The graphs look like straight lines within the range from 0-5% salt concentration, so I’ll use the numbers at 5% and assume they scale down to the epsilon of salt one would actually add.
Density appears to increase by 4%.
Specific heat appears to go from 4200 to 3930 (edit: not 3850, whoops), a decrease of ~7%.
Boiling point … not present in your link, but this says approximately +0.5° C per 2.9% of salt, so let’s say at 5% salt it becomes 100.8°C. The delta from a starting point of, say, 21°C thus increases by about 1%.
Conclusion: time to boiling is multiplied by 1.04∗.93∗1.01=0.98, a (tiny) decrease.
Addendum: I see recommendations of 1 tablespoon of salt per gallon of water, which is 0.4% by mass, so in practice the time to boiling would be multiplied by more like 0.998.
I think you meant 3950 not 3850? And if we hold water-mass fixed instead of total-volume (i.e. the water is already in the pot and we’re deciding whether to add salt or not) we should use 5% not 4% (density doesn’t matter, because we don’t care whether the volume goes up a bit upon adding salt). Seems awfully close to even.
(I don’t know much about physics, but...) Raising the boiling point just means raising the maximal temperature of the water. Since during normal (saltless) cooking that maximum is usually reached at some time x before the pasta is done, raising the boiling point with salt means the water becomes overall hotter after x, which means you have to cook (a tiny bit) shorter. What makes the pasta done is not the boiling, just the temperature of the water and the time it has some temperature.
Im pretty sure, though I cannot find data on it, that cooking in salt water simply causes salt to interact chemically with the pasta, “tenderizing” it, the same way salt tenderizes meat, vegetables etc.
I assume we could perform an experiment in which we submerge identical amounts of pasta in cold tap water, and in an equal volume of salt water, and wait until it becomes soft enough to eat. My assumption is that waterlogging pasta in salt water would soften it much faster.
Right, but if you wait for the water to boil before you put the pasta in, then you are waiting a little longer before adding the pasta. Then cooking the pasta slightly shorter after you put it in.
Yeah. And many people do indeed recommend one should add pasta only after the water is boiling. For example:
Don’t add the noodles until the water has come to a rolling boil, or they’ll end up getting soggy and mushy.
Except … they don’t get soggy.
I would know, I made a lot of pasta in spring of 2020!
While we’re at it, they also say
Bring a large pot of water to a boil.
which other sources also tend to recommend. This is usually justified by saying that by using a lot of water the pasta will thereby stick together less. But as I said, I consider myself a noodle expert now, I optimized the process, and using a larger pot just increases the cooking time (since more water takes longer to get hot), but has no measurable influence on stickiness.
Also you would have to add back in additional time to get the water to its (new, higher) boiling point in the first place...
Though, actually, apparently adding salt decreases the “specific heat capacity” of water, so that increasing it by N degrees requires less heat to be added (and therefore takes less stove time). The numbers in this article suggest that this makes a larger difference than the increased boiling point would.
(Though, again, the effect size seems to be epsilon for realistic amounts of salt people would add.)
The article has an egregious typo where they say “The pot containing a 20% salt concentration will heat up over 25 times faster”. I think they meant “over 25% faster”, which is either true or close-to-true. I’m not sure about the conclusion that cooking time goes (slightly) down; I think they’re holding total-mass fixed, but if we’re talking about “adding salt” then we should hold water-mass fixed instead, which adds onto the boiling point elevation effect and might tip the balance. I didn’t do the calculation because it’s entirely pointless. :-P
Doing the math because I have the urge:
The graphs look like straight lines within the range from 0-5% salt concentration, so I’ll use the numbers at 5% and assume they scale down to the epsilon of salt one would actually add.
Density appears to increase by 4%.
Specific heat appears to go from 4200 to 3930 (edit: not 3850, whoops), a decrease of ~7%.
Boiling point … not present in your link, but this says approximately +0.5° C per 2.9% of salt, so let’s say at 5% salt it becomes 100.8°C. The delta from a starting point of, say, 21°C thus increases by about 1%.
Conclusion: time to boiling is multiplied by 1.04∗.93∗1.01=0.98, a (tiny) decrease.
Addendum: I see recommendations of 1 tablespoon of salt per gallon of water, which is 0.4% by mass, so in practice the time to boiling would be multiplied by more like 0.998.
I think you meant 3950 not 3850? And if we hold water-mass fixed instead of total-volume (i.e. the water is already in the pot and we’re deciding whether to add salt or not) we should use 5% not 4% (density doesn’t matter, because we don’t care whether the volume goes up a bit upon adding salt). Seems awfully close to even.
(I don’t know much about physics, but...) Raising the boiling point just means raising the maximal temperature of the water. Since during normal (saltless) cooking that maximum is usually reached at some time x before the pasta is done, raising the boiling point with salt means the water becomes overall hotter after x, which means you have to cook (a tiny bit) shorter. What makes the pasta done is not the boiling, just the temperature of the water and the time it has some temperature.
Im pretty sure, though I cannot find data on it, that cooking in salt water simply causes salt to interact chemically with the pasta, “tenderizing” it, the same way salt tenderizes meat, vegetables etc.
I assume we could perform an experiment in which we submerge identical amounts of pasta in cold tap water, and in an equal volume of salt water, and wait until it becomes soft enough to eat. My assumption is that waterlogging pasta in salt water would soften it much faster.
Right, but if you wait for the water to boil before you put the pasta in, then you are waiting a little longer before adding the pasta. Then cooking the pasta slightly shorter after you put it in.
Yeah. And many people do indeed recommend one should add pasta only after the water is boiling. For example:
Except … they don’t get soggy.
I would know, I made a lot of pasta in spring of 2020!
While we’re at it, they also say
which other sources also tend to recommend. This is usually justified by saying that by using a lot of water the pasta will thereby stick together less. But as I said, I consider myself a noodle expert now, I optimized the process, and using a larger pot just increases the cooking time (since more water takes longer to get hot), but has no measurable influence on stickiness.
And to add the salt.
If you’re adding the salt after you turn on the burner then it doesn’t actually add to the heating+cooking time.