Has anyone tried using lactose to encourage lactobacillus sourness in a simple sour like Berliner weisse or Gose? One would figure giving the lacto a appropriate precursor that there is no competition for could be a winner.
Unless I'm mistaken, lactose can not be fermented - even by souring bacteria. The conventional wisdom is to use maltodextrin, which can be fermented by the souring critters but not by regular beer yeast.
I used a quarter oz. to goose a Berliner I made, my first. It had not soured much at all after four months, despite having a one liter starter made from apple juice and acid malt, plus a slant of WL lacto. D. The sourness took off after adding the lactose (just poured the powder in), but I think it oxidized somehow, because it darkened from a pale straw color to a pale amber. Next time I'll take more care to minimize O2 exposure.
I emailed Wyeast about 2 years ago regarding this very subject after a berliner weiss I brewed with their berliner strain didn't sour up enough. One of the mycologists and I talked about it and he told me that they had never done an experiment with lactose and lactobacillus. I experimented with it by boiling lactose with water with a ratio of 100g to 1 L and pitching that directly into the berliner. I "fermented" it for about 2 months and unlike zentropy, I didn't have any luck with it souring (it remained slightly sweeter). But like zentropy, I have had very good success with an apple juice starter and holding it at 100 degrees F (got that from emailing Vinnie at Russian River).
So my advice, try increasing sourness with an apple juice starter.