Reader John writes:
That’s an excellent question, John. The short answer is that no, that small amount of vinegar probably won’t make a significant difference in your cookies. But then I’m generally all about the long answer, and for that we need to go and compare the KA version to the classic recipe.
First thing to notice is that they are very similar, save for a few tweaks. KA swaps out some of the butter and replaces it with shortening. That helps give their cookies height and volume, as shortening doesn’t melt and spread quite as readily as butter (but it also likely gives them a somewhat greasy mouthfeel).
Next thing to notice is that the entire recipe is scaled back a bit compared to the original, with slightly less mass, which is to say, sugar and flour. Yet the amount of leavening remains the same. And that, combined with the shortening, probably also helps give these cookies a bit more volume.
But to the question at hand: the vinegar. There is no vinegar in the original Nestlē recipe. It relies solely on the small amount of acid in the brown sugar (plus the oven heat) to give it its “pop”. And that, generally speaking, is enough. However it has to be admitted that sometimes a little of the soda in the classic recipe can combine with some the fat to create a bit of soap (a process known as saponification). And that can occasionally give classic chocolate cookies a faintly bitter, off flavor.
KA is taking no chances with that. Thus the added vinegar, which is of course quite acidic. The acid helps ensure that all the soda in the recipe is fully reacted, giving their cookies a cleaner flavor. It also works to set the egg proteins a bit faster, preventing spreading, which again contributes to height and volume.
Will all those subtleties make a major difference in the cookies? My gut says…not really. However there’s really only one way to find out: make them and see! Thanks for a great question, John!