With an affordable home vacuum apparatus like a FoodSaver, you can seal up meats and such in plastic bags, for storage or sous-vide cooking. But you can't seal up liquids, or anything that's even somewhat liquidy, because the vacuum slurps the juice right out of the collapsing bag and into its pump.
But a little attachment allows you to vacuum-seal a canning jar, which instantly makes the FoodSaver a lot more useful. Vacuum-sealed in a jar, fresh juice stays remarkably fresh-tasting in the fridge for days on end. The easiest way to make custard, for ice cream or for its own sake, is to cook it sous vide at 82°C (179°F) -- but you need to vacuum-seal the jar to keep it from floating in the bath. It's also a great way to get the carbonation out of beer or champagne, if you want to cook with those ingredients. Just vacuum out a jar full of beer -- you may have to repeat a couple of times -- and it gets as flat as you could ever desire.