Ask Wine Wizard

How do I allow for suspended solids when taking hydrometer readings?


Ray Ruthenberg — Galena, IL asks,

I have been making wines for more than 20 years, but I have a problem with initial sugar determinations, added sugar requirements and subsequent alcohol content. Hydrometer readings on the initial crushed fruit may be way off, depending on how well the crush goes. Much could still be locked up in the uncrushed portion, especially on plums, cherries, and other hard to crush fruit. Would destoning, say one pound, and running the pulp through a blender and checking the specific gravity on the strained juice give a fairly accurate sugar content? Should I deduct a certain percentage for non-sugar solids?

You’ve hit the nail on he head — a hydrometer reading does depend on the amount of suspended solids in the juice that you’re measuring. As sugar is more dense than water, the more sugar (the riper your fruit is) in the juice the higher up the hydrometer will float in your sample. It’s easy to see that if you’ve got lots of little bits of suspended pulp helping the hydrometer to float well above what would be its natural level you’re going to get an artificially high reading. This is why it is so important to measure juice that has as little suspended solids as possible. I don’t recommend you invest in a battery of strainers, settlers and centrifuges. That would be silly because if you follow the tips below you will have juice that is just fine to measure — the extra degree of precision that these tools of paranoia could buy you would be minimal indeed and certainly not worth your time or money. I always always follows the same procedure when checking my sugars: soak, sample,
Response by Alison Crowe.