I just got a kitchenaid stand mixer and the bread bible for Mother’s day - happiest about the bread bible since our book store told me it was out of print yet another store same chain found one for me - on line stores are reluctant or refuse to ship heavy books to Canada.  So with my bible in hand and my kitchenaid and Zojirushi bread maker ready I would like to try a pumpernickel bread.  I of course do not have some of the ingredients in the recipe (no pumpernickel flour but have dark rye, no caramel colouring)  I am wondering what is the purpose of the vinegar in the recipe.  I had tried to make a pumpernickel loaf with my old bread maker - before the kneading was finished that baby walked off my granite counter and broke the lid so have no idea how it would have turned out but it did not call for colouring or vinegar.
Raised in Montreal I love good rye bread and good pumpernickel.

SHIRLEY:
  Good morning to you & welcome to our baking forum. The use of vinegar in a baked product such as in a Yeasred bread is to give it additional flavor…that is if not to much is used. It also discourages gluten formation that is why you should not use to much. However, in pie dough it is an advantage to use there.. It is okay to employ it just do not use too much of it.
  I hope this answers your inquiry. Good luck in your bread baking & have a nice day young lady.

~FRESHKID.

Read your post on the main blog. Agree with Freshkid, it isn’t essential, but does add something to this bread, so I would use it considering you can usually get cider vinegar for under a $1. The coloring is completely optional, and only makes the bread darker. It will be a light chocolate color without it, but deep dark chocolate with it. Personally, I think its worth it (order from King Arthur), but don’t let it keep you from making this bread, one of my faves in the book!