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I like to use old recipes. I made a lasagna from a 1970's era recipe of mine. It was very (too) salty. I used Italian sausage (Johnson brand), ground beef, tomato paste, mozzarella cheese (Rouse's brand), ricotta, an egg, and only added 2 teaspoons salt. I should have known better than to add salt, but I don't recall the recipe being that salty. Is there more sodium in prepared foods (I'm thinking cheese and tomato paste) these days?
I think that it's more likely that your taste buds have learned to be more sensitive to salt over the last few years. For many that can be the case. Where recipes used to contain this level of added salt that's less true now. We know that over time when eating less salt your taste buds will adjust to the lower sodium levels (see: The Health of It All: Do Your Taste Buds Learn?)
Many of the ingredients in this recipe are higher in salt, including the sausage, tomato paste and mozzarella. Combining those with the two teaspoons of salt can make the recipe pretty salty tasting.
Of these ingredients the easiest to control are the added salt itself and the tomato paste. There are lower sodium sausages on the market, but you have to look carefully at the package. Interestingly, I have found that sausages made by smaller, family owned firms are lower in salt. Low sodium cheese is tasteless and the salt actually aids in the texture.
I would start by using no salt added tomato paste and lower the added salt to one teaspoon. When I am creating recipes I use the guide of 1/8 teaspoon of salt per serving, which is about 300 mg of sodium. By using that amount, generally the other ingredients (depending on their amounts) will add more sodium to the dish.
Thanks for your very interesting question,
Timothy S. Harlan, MD, FACP