I second Bob's comment.
I'm puzzling over how one reliably gauges acidity of grapes using the pH
measurement. Fruity acids are such weak acids that they don't affect
the pH very much. The amount of potassium in the grapes creates a much
larger swing in the pH. High potassium gives high pH.

The only reliable acidity measurement I know of is TA (total acidity).
I look at pH strictly from the standpoint of stability against spoilage
at the high end (3.7-4.1 pH), and inhibition of ML fermentation at the
low end (<3.3 pH).

Gene

wrote:

> Maybe too some perfectionists those numbers may seem sub-par but too me
> those numbers are great. Hopefully they don't change much.
>
> Bob
>
>
> EnoNut wrote:
>
>>I just tested the plot I wan't to use to crush next weekend. The Brix
>>is 25.1, but the acid seems a bit low at 3.56 pH. The pH/Acid is 318,
>>not exactly the 220 - 260 I wanted. How much would one normally expect
>>those values to change in a week of moderate weather? I don't have a
>>choice on timing, unfortunately the availabilty of equipment and help
>>is going to make next Sat my day. The stems are browning, but not
>>brittle and the seeds are light tan to brown and crunchy. All in all
>>from what I've read it should be OK to pick next week, but probably not
>>optimum.
>
>