I brewed a lambic last December using a highly unfermentable wort, and fermented with a "house culture" that I grew up from commercial dregs. I just took a sample a couple of days ago and while the Brett character is amazing, there is virtually no sourness at all. Right now it is still sitting at 1.015 nearly a year into fermentation, and the acidity level is just slightly more than my saison typically is. I didn't take a pH reading, but my guess is about 3.8, give or take. I'd really like this in the low 3's.
For my wort, I had a short, high temp mash of pilsner malt and I also separately steeped some torrified wheat. I combined the two and boiled for 90 minutes. The idea was that by steeping the wheat separately I'd (hopefully) produce a starchy wort similar to a turbid mash. My gravity was pretty low post-boil, so I added a mix of DME and maltodextrin to boost my OG to about 1.045.
This is my first time brewing a lambic, and it's also my first time using this culture in primary fermentation. I'm wondering if this beer just needs more time to sour, or whether I need to intervene somehow (I was thinking of adding Pediococcus).
I've used this culture in secondary for a Flanders Red once before. That one turned out sour, but it was quite acetic. I don't have enough experience with this culture to know if it just doesn't produce enough lactic acid with its current mix of bugs. The culture is dregs from Red Poppy, Gueuze Girardin and Gueuze Fond Tradition that were stepped up twice in the bottle then pitched to a "mother" DME culture that I have been maintaining.