Non-Sugar Solids in Various Varieties of California Grapes

¹ United Vintners, Inc., Research and Quality Control Laboratory, Asti, California.

The non-sugar solids in California grapes, as determined by practical procedures on a fairly large sampling during the vintages 1961-1963, vary more directly with the variety than with the season or region of growth. The wet stems and dry pomace of the wine varieties tested averaged 8.12%, the table varieties 6.03%, and Thompson Seedless 4.32%. The 1963 average non-sugar dissolved solids (L-S) of all the grapes analyzed was 2.16%. The average glucose-fructose ratios in 1963, calculated from the results of sugar analysis by two methods, ranged from 1.70 to 0.82. It all the sugar is accounted for, 0.47 g/g is a good practical figure for converting grape sugar to equivalent alcohol.

If the grapes received at a winery fall into the general categories discussed in this report, and the relative quantities of each are known, the net amount of reducing sugar, or equivalent proof-gallons, could be calculated closely (plus or minus 1-2%) with no other analysis than an accurate degree Brix of the clear juice, using the non-sugar solids figures (L-S) in the accompanying tables.