The process of pulling a vacuum causes the liquids to change from liquid to gas. Depending on how deep a vacuum You pull will determine what liquids You turn to gas. Those gasses are forced to expand and exit the vessel through Your pump. with reference to Your steak marinating, Your steak acts as a sponge. You suck all the air, blood, etc out and when You release vacuum the marinade fills the voids. Liquids will turn to a gas "boil" based on temperature and pressure. if water is under HIGH pressure it wont boil at 100 deg.C "212 deg.F" but higher than. if in vacuum it will boil lower temp. alcohol boils at 160 deg.F at atmospheric pressure it will boil at 70 deg.F if under 20ish in. hg. water boils at 70 deg. F 29ish in. hg.