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Sugar Conversion Tables

TroubleShooting

Bob Currul — Lake Como, Florida asks,
Q

I am fairly new to home winemaking having only made a few kits and three batches of Muscadine wine. I have been using Daniel Pambianchi’s book Techniques in Home Winemaking as my primary reference and have recently acquired The Winemakers Answer Book. My confusion arises from a disparity in the Brix/SG/PA tables. Techniques in Home Winemaking lists an SG of 1.09 as 21.6 °Brix with a PA of 11.2 while The Winemakers Answer Book lists SG 1.09 as 22 °Brix with a PA of 12.7. Why the large difference?

A
For the Answer Book I referenced the Table 1-2, Appendix 1, from Wine Analysis and Production, Zoecklein et al, 1995 for the Specific Gravity to Brix tables. Note that this conversion is at a specific temperature — 20 °C (68 °F). Daniel’s table may have been slightly different, or just a choice in how the table calculation he referenced rounded the decimal points. As far as the potential alcohol, I know I’ve answered this before — even “experts” (wine chemists, etc.) will tell you that it’s really hard to accurately predict potential alcohol 100% of the time when you start with Brix or Specific Gravity (SG) — all you can get is within a range of perhaps 1.0%, depending on your fermentation. The number I chose for 22 °Brix was the average of the range. What’s maddening is that SG and Brix are really just quick and dirty estimates of the amount of sugar in a wine — really just the density. They take into account all dissolved matter in the juice, which is more than just glucose and fructose,
Response by Alison Crowe.