Vacuum Pumps

Some sauces or sauce components are best boiled or evaporated under vacuum so that the temperature inside the vessel can remain relatively low. This way, the sauce can be reduced and its more delicate and fleeting components remain intact, since they have not been exposed to high heat. This is especially useful when working with fine wines or delicate gelées in which the finesse of the sauce is particularly important.

While there are many kinds of vacuum pumps, some costing many thousands of dollars, two types are most commonly used in the kitchen. A medical vacuum pump is relatively inexpensive, and convenient to use. Most such pumps come with a separate vessel—a trap—that can be used to condense excess water vapor and thus prevent moisture from entering the pump (which would cause damage). A trap is in essence another flask with a two-holed stopper and two lengths of glass tubing (one for each hole) that is set up between the main flask and the pump. The trap is best submerged in ice water (along with any tubing leading to it) so that it condenses any moisture before it can reach the pump.