Explain Osmotic Pressure

Osmosis, as you may already know, refers to the flow of solvent into a solution, or from a more dilute solution to a more concentrated solution, when the two liquids are separated from each other by a semi-permeable membrane.  The membrane contains minute pores through which the solvent molecules can travel.  The phenomenon of osmosis causes a change in the relative volume of the two liquids separated by the semipermeable membrane. The volume of the solution that  becomes more dilute increases. Osmotic pressure is the pressure required to prevent that increase in volume or osmosis. Unlike solutions, colloids have little or no osmotic pressure. Hence, there is no passage of colloidal particles through animal membranes or cellulose walls.

The phenomenon of osmosis occurs in food.  For e.g. when you stew fruits, the fruit increases in size, as the water flows with the fruit tissues. When the sugar concentration becomes higher than that of the fruit, the  fruit will shrink due to the passage of water through the skin of the fruit into the syrup.