The texture of sorbetto is controlled by the sugar content of its sugar syrup. If the sugar content is too low, the sorbetto will be grainy. If the sugar content is too high, the mixture will not freeze properly. Because different types of fruit and other ingredients have different sugar contents, there is no standard amount of sugar that should be added to a sorbetto mixture. The sweetness of a sorbetto base is adjusted by the addition of either water or sugar syrup. In a professional kitchen, testing the sweetness of a sorbetto base mixture is most easily done by using a refractometer, which registers the sugar density of the mixture. Refractometers measure in degrees Brix, which represents the sugar content as a percentage. A mixture registering 26° Brix contains 26 percent sugar. Sorbetti should range from 24° to 28° Brix. If no refractometer is available, follow the recipe and, if necessary, thaw the finished sorbetto mixture and adjust the sugar level—up by adding sugar syrup, or down by adding water.