What’s a good rule of thumb for O2 levels before filling tankers?
Short answer is, you’ll do well to get below 1 ppm, and 4 ppm is where most wineries panic and sparge w N2 upon receipt. I hate this procedure, which strips volatiles, so let’s avoid pickup in the first place.
Let’s first talk about how you achieve this, then some debunking with theory.
Tips for loading a wine while minimizing DO pickup:
- Always ship full compartments if you can. If multiple compartments, top the biggest one and go partial on the other smaller volume.
- Lay down a layer of inert gas approximately 1 foot high. Calculate the number of standard cubic feet this will take by measuring the length and width of the compartment at its widest, for example 20’ long X 8’ wide x 1’ deep = 160 SCF. The best way to lay down a layer is with pelletized dry ice. This disperses in a small amount of wine, so it doesn’t boost your dissolved CO2 very much, and is still a good practice for reds. One pound of dry ice converts to 30 SCF, so in this example, throw in 5-6 pounds. Next best is to deliver this gas in a laminar fashion through the sending line.
- Always inert the lines. Any gas will do, but the heavier than air (CO2, Ar) are better blanketers. Go right through your centrifugal pump. Any flow up to 1000 SCFH will lay laminar into the truck, creating a blanket because the gas is cold. This layer will persist long enough for the pumping to occur.
- The best loading pumps are magnetic-driven closed housing centrifugals. Your standard winery centrifugal has a spring-compressed carbon seal which sucks in air, especially if the seal has been scored by particulates. If you have one of these, keep your seals ground smooth and replace your springs every year or two.
- If you have a partial tank, your blanket will disperse in transit, so you have to gas the headspace. Laminar argon is best for this because it’s faster to deliver 1.25 volumes of argon than 4 volumes of N2 (see Argon, What A Gas). CO2 may be used if you don’t mind the pickup.
- Measure, measure, measure. Measure the wine in the tank at start and in the truck at finish. Measure the top of the headspace as you evacuate with laminar flow. Measure the DO upon arrival.
What is missing from all this standard dogma? The simple question: “Why do you care?” Big young reds will gobble up 4 ppm in a few hours, and often benefit from the experience. A delicate Sauvignon Blanc, however, may be completely transformed by that amount of pickup. Know your wines’ Oxygen Appetites, which vary 10,000-fold. Yes, that’s a plug. But as you well know, oxygen is not always the enemy.