salt
If I'm preparing a dish for myself and someone on a low-sodium diet, I will withhold adding salt while cooking. Instead, I'll season my plate after serving. However, I can't seem to get the same flavor from adding salt after-the-fact as I do when I'm salting while preparing the dish.
Is this all in my head or is there actually a difference in how the flavors are affected depending on when the salt is added?
Trying to get to the bottom of the issue, I decided to take a few pictures of a few different types of salt. The pictures shown below were taken by me and are all proportional (the camera was the same distance away from each type of salt, so you are getting an accurate size comparison).
The picture illustrates my suspicions, which is the difference is the surface area (ignoring of course mineral content and different types of grinding salt). Standard table salt is a compact little cube, effective when it’s to be dissolved in a liquid, but not so much when it comes to direct contact with the taste buds. Place one cube on your tongue and you get 1/6th of the surface area in contact, meaning, a lot of salt without much saltiness. Sea salt, with a more rectangular shape is closer to 1/4th the surface area touching your tongue. Ground salt is more like shards of glass, so nearly half of the exposed area could be in contact making things taste that much more salty. Also with a much finer texture, you are left with many more particles in a wider area, meaning, a saltier taste with less salt.
It’s a good way of finishing a dish when the salt is going to be lightly dusted on top or mixed with an oil where it will not dissolve at all. When you are dissolving it in a liquid, it really makes little difference which type you use. When it comes down to it, it’s all about how picky you want to be with it.
Your experience with the curry is normal. Salt helps bring out and enhance existing flavors. This is true for everyone, as far as I know. Different people have different sensitivities, and want different amounts, but the effect is the same. Given that you thought the curry tasted better with it, I wouldn't be surprised if you should also be adding salt to other things - maybe just not as much as recipes typically call for.
Best Answer
Yes, the flavor is definitely affected.
First, there is the point of solubility. Salt doesn't dissolve all that easily in water, and unlike many other crystals, its solubility doesn't improve with heat. So you have to either stir a lot, or let the dish to sit for a longer time after the salt is added, or both. Else you end up with uneven salting in liquid dishes like soups. Thicker things like sauces are very marginal, and if you add salt to cooked dry stuff (steaks, casseroles and whatnot), you're guaranteed to end up with clumps.
But even if you succeed in getting your salt evenly distributed, the flavor is different. The liquid components may be OK, but anything solid (pasta, meat, vegetables, whatever) will not be penetrated by the salt. So if you salt your dish to the point where the liquid tastes normal, you get bland pieces swimming in an OK sauce or broth. At that point, most people just automatically think that it is still bland, and continue to salt, resulting in oversalted broth/sauce with bland veggies, which in my opinion is even worse.
Third, the salt isn't used only to add taste. A saline solution's chemical properties are quite different from those of pure (or tap) water. Marinading with salt (with or without liquid) changes the texture of steaks (but does so rather slowly). Vegetables cook firmer in salty water, instead of getting mushy. And then there are all the amazing things it does to grains (because it affects both starches and gluten). In short, don't bake a yeast dough without a pinch of salt.
Sadly, all this means that there is no way for both of you to eat what you want/should. My advice is that you should definitely salt the food even for the low-sodium eater at the proper cooking time, you just should use a much smaller amount - even a gram of salt per liter of water can be useful for the chemical changes you want, and shouldn't add too much of a sodium load to a normal sized portion. As for bringing your portion to your own taste, you will have to put up with the worse saltening. Just take care not to oversalt as a reaction, it doesn't really help.