Why add baking soda to soup just before serving?

I have a cream of tomato soup recipe that calls for assembling everything then holding the soup in a double broiler until ready to serve....Then at that point adding a pinch of baking soda & some milk just before serving. Why would this be? What is the baking soda doing?

usclious
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4 Comments

Sam1148
Sam1148 March 16, 2016
A pinch of baking also rounds out a tomato sauce that's a bit to acidic.
It's also a trick used for sweet iced tea to smooth out a bitter tea.
 
LeBec F.
LeBec F. March 16, 2016
well if that isn't the darndest! Who knew?.............
 
702551
702551 March 14, 2016
It keeps the milk from curdling.
 
702551
702551 March 14, 2016
Source: Fannie Farmer cookbook (1996 centennial edition)

https://books.google.com/books?id=oioeRpagr_kC&pg=PA95&dq=fannie+farmer+cream+of+tomato&hl=en&sa=X&ved=0ahUKEwitvf2N8sDLAhUY2mMKHbcSDAsQ6AEIMDAA#v=onepage&q=fannie%20farmer%20cream%20of%20tomato&f=false

Note that the baking soda has always been present in this recipe, dating back to the original 1896 edition. The head note explaining the baking soda's action appeared more recently.
 
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