I pulled this data just to highlight the type of variation you might see with must analysis. Having the TA and pH is part of the picture, and better than nothing, but the data shows partly why it is not so straight forward to make adjustments to acid and pH pre-fermentation. I'm not trying to provide any in-depth explanation here, many factors too complicated for me, but mainly this is just a conversation piece.
You can see a fairly wide variation in the malic acid content, and this represents what will be converted to lactic during the ML, so the reduction in TA post ML is a variable we don't normally know. The malic acid content will vary by grape, growing conditions, and harvest date etc.
In the cases where the tartaric acid and the malic acid were determined, you can see that they add up to greater than the TA. The potassium content plays a role here.
A different subject is the nutrient content (YAN); huge variation at the extremes with one must at 450 and another at 47. This might explain partly why you can still have H2S or stuck fermentation issues even when adding nutrients.
Another subject is the brix by refractometer vs. the glucose plus fructose content; the glucose and fructose are the primary fermentable sugars. In one must you measure 23.9 brix, but you really have 25.1 (251g/l), in another you measure 22.3, but you really have 23 (230g/l). Not massive differences, but they are different.
I'll still measure what I can, and will try to do the best I can with what I have, but numbers are just numbers, and you may not have what you think you have.
