Ask Wine Wizard

Pressing Issues

TroubleShooting

Jim Skufis — Ann Arbor, Michigan asks,
Q

This past weekend I crushed and pressed two cases of Riesling grapes in my screw-type basket press and my yield of juice was not quite 4 gallons (15 L). The grape skins left in the basket after pressing seemed heavy with remaining juice despite my maximum effort at the press over an extended time. I’ve noticed that I get far more juice from my macerated red grapes (5+ gallons/19+ L per two cases) but maceration isn’t recommended for most white grapes per the references I use for my winemaking. Are there any solutions to improve juice yield when pressing white grapes? I’ve read about adding rice hulls to improve flow. It’s been suggested to me to (1) actually do a cold (40 °F/4 °C) maceration for a few days, (2) try freezing the grapes first, (3) buy a pneumatic press, or (4) give up on pressing white grapes and just buy juice. What would you suggest?

A
You’ve hit on one of the classic difficulties of making wine at home. The equipment we use, from presses to barrels to filters, usually are much smaller than that used by commercial wineries. Yet the size of the grapes and the job we need our equipment to do remain the same. Getting a better press yield out of grapes, both red and white, is tough for home winemakers. The presses are smaller and, especially with hand-operated basket presses, there’s only so much force we can apply to the grapes. Your tale of wet, heavy grape skins tells me that indeed you did leave a lot of juice behind. Fortunately, there are a few things that small-scale winemakers can do to improve juice yields. Think about using a maceration enzyme for white grapes. Enological enzymes are naturally occurring proteins that, when added at the crush stage and before pressing, can help break down the cells in the grape skin and pulp, which improves the press’s ability to release juice. Bottles of enzyme can be purchased from commercial winery labs like Scott
Response by Alison Crowe.