Question: Yesterday I made bread based on a recipe I found on the flour bag. It contained both rye and wheat flour but also three tablespoons of vinegar. I've never seen it used in bread before, why is it there?

Answer: 
When I asked this question - [Is there anything I can add to homemade bread to preserve it?](https://cooking.stackexchange.com/questions/7804/is-there-anything-i-can-add-to-homemade-bread-to-preserve-it) - Arafangion said that one commercial bread company now uses vinegar as a preservative. This is his answer to my question: 

> 
> "One commercial bread company has
>  switched preservatives... They use
>  vinegar (I suspect ordinary white
>  vinegar).
> 
> 
> Maybe you could give a little bit of
>  vinegar a go and see how that works?
>  You can still smell it if you sniff
>  and sandwiches do have a faint vinegar
>  flavour, but it seems to work well
>  enough for the company and it
>  apparently hasn't sabotaged the
>  product line...
> 
> 
> Then again, it /is/ commercial
>  bread..."
> 
> 
>
In making faster no-Knead bread Jim Lahey suggest adding 4 drops or up to 1/4 tsp of red wine vinegar to the basic recipe. Improve gluten development and flavor. See the video with Mark Bittman here:
<http://www.nytimes.com/2008/10/08/dining/08mini.html?ref=dining>