b) Specific gravity: As fruit mature, their specific gravity increases. This parameter is rarely used in practice to determine when to harvest a crop but it could be where it is possible to develop a suitable sampling technique. It is used, however, to grade crops into different maturities. To do this the fruit or vegetable is placed in a tank of water; those that float will be less mature that those that sink. To give greater flexibility to the test and make it more precise, a salt or sugar solution can be used in place of water. This changes the density of the liquid, resulting in fruits or vegetables that would have sunk in water floating in the salt or sugar solution.