What purpose could baking soda and cream of tartar serve in a meatball recipe? I came across a recipe for Italian-style meatballs today that includes two ingredients I've never seen used in any meatball recipe before: baking soda and cream of tartar. It also does not include any sort of bread or breadcrumbs, as is generally customary.

What could be the purpose of adding these ingredients? Does it somehow go hand-in-hand with omitting a bread filler?

Recipe ingredients:


1/4 teaspoon baking soda
1/2 teaspoon cream of tartar 
1 tablespoon water 
1 pound ground beef 
1 tablespoon balsamic vinegar 
2 cloves garlic, minced (about 2 teaspoons) 
1/2 cup fresh parsley leaves, minced (about 2 tablespoons)
1/2 teaspoon salt 
1/4 teaspoon crushed red pepper flakes 
1/2 teaspoon Italian herb blend (or oregano)
According to Cook's Illustrated's article Tenderizing Meat with Baking Soda (possible paywall):


  Briefly soaking meat in a solution of baking soda and water raises the pH on the meat’s surface, making it more difficult for the proteins to bond excessively, which keeps the meat tender and moist when it’s cooked. 


This is almost certainly the effect of the baking powder:  to help create a more tender product.   This is probably especially necessary given the lack of bread products (which provides starch that physically interferes with protein linking, and helps retain moisture in the, thus producing a more tender meatball).

The tartaric acid is probably there because recipe authors are used to pairing it with baking soda which is necessary when it is used to create leavening in baked goods.  In the meatballs, it will simply tend to help make them more acidic, although it will also neutralize some of the baking soda.

I have surveyed several recipes on the web which include baking soda in meatball recipes; they variously claim that it helps make the meatballs lighter or more tender.