I looked it up, nicotine below pH 8 is largely protonated but in the ionic state does not like to cross membranes according to a quick literature search. Meaning acidic tobaccos such as VA flakes I assume would provide less of a hit than more alkaline ones I suppose burleys? Just reading up here. Vinegar casing would then help done down blends. Then again: A persons pH in the mouth would dominate the absorptionpH does not affect nicotine content, however, it seems to affect the nicotine absorption and/or makes the absorption, however little there is, more noticeable.
Think of it like a mixed alcoholic drink that is sweet tends to hide from the consumer the amount of alcohol they are actually consuming, whereas with unmixed drinks, it's more noticeable.