Added fruit, what activity should I be expecting?

Last Saturday I added several lbs of fruit to a couple of gallons of Lambic. Actually I did 2 lots, with different fruit; one was with 'fresh' fruit that had been frozen and pasteurized at 150 F before adding. The other was with dried fruit, which I also pasteurized at 150 F before adding.

I added some water to the fruit in the pan to be able to heat it up, and added some LME to effectively bring the gravity to the same as the Lambic (1.056). I assumed that fresh fruit has about 10% sugar per lb.

Overall both batches had plenty of new fermentables.

The Lambic is 7 months old, had a gravity of 1.010, tasted great; reasonable sourness, but not over the top.

Today, 3 days on, there is very little activity happening. The one with fresh fruit bubbles about every 5 to 10 minutes. The one with dried fruit is showing some activity (as can be seen from level changes in the airlock) but I have yet to see a bubble. Looking thru the side of the fermenters there are only a few bubbles showing around the edge, I can't see well enough to see the surface.

Is this what I should be expecting, or should there be a lot more activity. I have a Brett starter on hand ready for brewing this coming weekend, and I could add some of that to help it along.

Is this normal? Should I be concerned? I calculate the alcohol level of both batches to be about 4% abv after the addition of the fruit/liquid/LME, which should provide plenty of protection.

Slow down, at this point there isnt much sacch left (acidity + time killed it) so what you have left is (hopefully) lots of bacteria, brett, and sherry flor working away.

When you add the fruit it wont start to ferment like gangbusters right away, it may take some time. Also you should know that airlock activity isnt an indicator of anything.

Im not quite sure why you felt you had to "pasteurize" the fruit prior to adding. You definitely changed the fruit flavor (cooked fruit = jam like) and it wasnt needed. Your adding fruit to a sour beer that should have a very active culture, alcohol, and a low pH. Not much would survive this transition

The one thing you didnt say was what type of fruit you used?

I made my first fruit addition to lambic about five months ago (raspberries). I also expected to see some rapid activity but it never took off. Actually I racked some into a new carboy and some on the raspberries and the plain carboy formed a new pellicle in about a week. The raspberries had some positive pressure against the airlock for a few days but it took a couple of months before the pellicle started to form. I'm not sure if that's an indication of CO2 slowly being released from fermenting the fruit or if it just took a while for the pedio and brett to build up enough population to handle the sudden influx of sugar.

Either way, I wouldn't be concerned with slow activity.

After 6 days, the activity has really picked up. Each batch (2.5 gallons each) is producing a bubble every 20 seconds. I have not added anything. I assume this is the sacc yeast waking up.