Thanks for help, everybody. Per Tom's, Dave's and Bill's suggestion,
I've done another test on the Pinot Blanc, with 2 samples - one
degassed and one not. Yes, the degassed sample was lower by 0.5g/L, so
my initial post-ferment measurement was indeed artificially higher.
I'll watch this from now on.

Given the correct value is 7.5g/L, I'm still 1g/L above the expected
value of 6.5g/L. This could be the succinic acid, as Lum suggested.
But I'm still wondering about the initial measurement - it came at
4g/L, with pH 3.4, but it didn't taste particularly flabby. The juice
came in frozen, I've defrosted it, mixed pretty thoroughly and let
settle in the fridge for a day, then measured. Is it possible there
was some bitartrate in the juice that went back into tartaric acid
during fermentation? And if yes, how do I avoid getting this error
again - should I heat the initial sample as well?

Thx,

Pp

(pp) wrote in message . com>...
> Hi:
>
> I've been having a pretty consistent problem with titrating white
> juice before fermentation, adding tartaric acid based on the results,
> and then titrating after fermentation that the TA level is way too
> high. Latest example: Pinot Blanc juice measured at 4g/L, acid added
> to raise to 6.5g/L, now measured at 8g/L after relatively cold (around
> 15C) fermentation. I really don't know what's going on because:
> - I'm using the same method (pH meter to 8.2) before and after
> fermentation;
> - the juice is fresh, so all acid should be measurable before
> fermentation;
> - it can't be sodium hydroxide losing strength because then the
> measurement would be artificially higher, not lower;
> - the error seems to be consistent, so that cancels any possible
> accidents, like wrong sample size.
>
> I'm stumped at this point, and I'd really appreciate any help on this,
> as I don't enjoy wines that are too heavy on acid.
>
> Thx,
>
> Pp