In Wine Chemistry

We are all taught how important pH is in winemaking. A low pH makes SO2 perform better by having a larger percentage of molecular SO2, it makes bentonite settle better, it keeps bad bugs at bay, and generally is something to brag about when you are gathered around a barrel at the end of the day. All this has to do with hydrogen ions, iso-electric points, pH tolerances and lots of other stuff we have long forgotten about since learning about it.

The concept of pH was first described by the Danish chemist Søren Peder Lauritz Sørensen in 1909. The notation given by him was at first pH, with the subscript H, being derived from hydrogen, but the exact definition of the P is a subject of speculation to this day.

When I was studying the importance of pH was drilled into us, and ‘till this day everybody will tell you how important it is, but besides keeping it as low as possible, tell me, what on earth can you do about it? It is like worrying about your own death.

If we follow good practices like adjusting juice acidity early, adjusting acidity after fermentation and malo, what can you do about pH? Why do we keep analysing something, and wasting money doing it, when the purpose of acidification is so broadly linked to pH and not linear at all.  We can just as well stop analysing for it.

I want to ask you how often have you seen lab sheets where people fill in the analysis they have done, and only ask for total acid? If you have the pH, what can you do with it? Be philosophical, brag to your mates about your low pH, worry about it?

When people ask Loftie Ellis (a South African winemaking consultant) what the pH of a wine is, he often answers, “it is enough”. To him the microbial condition of a wine is much more important than the pH.

I have heard of winemakers who do pH adjustments, with legal acids as they should, and then deacidify closer to bottling. This is however an extreme, when you have to take into account that the wine will not win a double gold because of your efforts to fight high pH, but because you have good grapes foremost.

Besides good practice which should always strive to keep the pH of the wine as low as possible, while keeping the affect of acid on taste foremost in mind, you do not need to have the pH of a wine analysed.

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