However, I'm aware that many liqueurs get their heart and sould from fine suspensions of fruit material. Using serious filters will be a ginger and cautious process, as I try to figure out the proper balance to use between bad suspensions and essential ones. Each liqueur will be different. Sulphite Sulphite is essentially a preservative. You find it used on dried fruits to preserve coloration, and you find it in wine.
Oxidation is among the greatest threats to wine.
If you don't have your carboys filled right up to the neck, the extra surface area exposed to that tiny amount of air can ruin the whole batch. If your wine gets poured through the air without great precaution, the same problem can happen. That's why so much wine-processing happens in plastic tubes and glass containers. Liqueurs are very different from wines in this regard, though. While liqueurs are certainly susceptible to oxidation over long periods of time, air is no immediate threat to them.