The amount of substance dissolved in the solvent determines how much the presence of a solute lowers the freezing point. By the same token, the solute and its concentration immediately affect the vapor pressure depression of the solvent. Utilizing saturated solutions in an isolated system at a specific temperature, this characteristic is used to achieve controlled relative humilities (i.e. partial water-vapor pressures) when utilizing water as the solvent.
The decrease in vapor pressure is also used to extend the shelf life of processed and unpasteurized foods. If the sugar content of a cake is increased, the moisture becomes more tightly bonded, lowering the water-vapor pressure. In turn, this lowers the amount of free moisture required to support microbial activity growth. To compensate, mass-produced “high-ratio” cakes have an excessive sweetness and questionable health benefits.