I've never been clear on what volumes to test/adjust with respect to
both pH and TA in red must. Having just picked up a 1000lbs of Merlot,
I'm really anxious to get the acid adjustment right before my primary
fermentation ends.

At crush, I took a sample of must, both free-run and grapes, attempted
to press and strain the combined juice, then titrated TA and measured
pH. My results showed:

TA of 4.25 g/L
pH of 3.82
23.25 Brix

I decided to initially raise the acid by 1 gram of tartaric. My first
question is how should that 1 gram per litre be calculated, on the
volume of the must (420L) or the volume of expected juice after
pressing (approx. 310L - according to literature I've read). I chose
the latter and added 310g of tartaric to my must.

I tested the following day using my 'press and strain' technique
and got the following:

TA 5.75
pH 3.63
23.50 Brix

The sample also tasted pretty bland.

I also drew a sample of free-run and tested the pH, which was 3.39.
This sample tasted very tart.

Now, I'm torn on whether or not to add more acid (I started the
ferment last night). I understand starting a ferment above pH 3.5 is a
bad idea, but which number (pressed vs. free-run) has more meaning?
Pressing seems really inaccurate, simply because one can't ensure a
consistent ratio of free-run to berries and the berries don't press
very well. I'm also concerned that dropping the pH of the free-run
any lower will cause problems for my ML, which I plan to inoculate
towards the end of ferment.

Any help would be most graciously appreciated.

Darin

I'd just start the ferment and correct the acidity after ML is finished. Fermenting
itself seems to have unpredictable effects on acidity because of potassium
content and other factors. My pinot this year was around 3.35 pH at the vineyard,
but dropped to 3.1 after primary and is now back up around 3.5 with malo just
about complete. In previous years, petite sirah and mourvedre came in at 3.8, were
3.92 after fermentation and malo, and I adjusted them to 3.6 afterwards with fine
results.

Darin Young wrote:
> I've never been clear on what volumes to test/adjust with respect to
> both pH and TA in red must. Having just picked up a 1000lbs of Merlot,
> I'm really anxious to get the acid adjustment right before my primary
> fermentation ends.
>
> At crush, I took a sample of must, both free-run and grapes, attempted
> to press and strain the combined juice, then titrated TA and measured
> pH. My results showed:
>
> TA of 4.25 g/L
> pH of 3.82
> 23.25 Brix
>
> I decided to initially raise the acid by 1 gram of tartaric. My first
> question is how should that 1 gram per litre be calculated, on the
> volume of the must (420L) or the volume of expected juice after
> pressing (approx. 310L - according to literature I've read). I chose
> the latter and added 310g of tartaric to my must.
>
> I tested the following day using my 'press and strain' technique
> and got the following:
>
> TA 5.75
> pH 3.63
> 23.50 Brix
>
> The sample also tasted pretty bland.
>
> I also drew a sample of free-run and tested the pH, which was 3.39.
> This sample tasted very tart.
>
> Now, I'm torn on whether or not to add more acid (I started the
> ferment last night). I understand starting a ferment above pH 3.5 is a
> bad idea, but which number (pressed vs. free-run) has more meaning?
> Pressing seems really inaccurate, simply because one can't ensure a
> consistent ratio of free-run to berries and the berries don't press
> very well. I'm also concerned that dropping the pH of the free-run
> any lower will cause problems for my ML, which I plan to inoculate
> towards the end of ferment.
>
> Any help would be most graciously appreciated.
>
> Darin
>


--
ernie San Francisco Bay AVA
California, USA
to reply, rack off the lees.