I'm making 6 gallons of wine from welch's concentrates (6 white grape
and peach, 3 white grape, 1 white grape and pear, and I forget what
the rest of the mix was exactly, my notes aren't here with me). So, I
emailed them to find out about whether the concentrates are
standardized to a specific pH, TA, etc, as I thought they probably
would be for consistency sake.

So I got a reply, and here it is:
"Thank you for contacting Welch's.

Welch's product formulas and manufacturing procedures would include
standards
for brix and pH for each product made by our company. This ensures
consistent
flavor and quality.

We appreciate your interest in our products."

They also snail-mailed me two coupons for their juices, so email them
if you're planning to make a wine from their concentrates and save
some cash. :-)

My batch is bubbling away right now, and will be ready for
secondary...whenever I bottle the apple cider that's sitting in my
only 6 gallon carboy.