The short answer
The real difference in sorbet vs sherbet comes down to milk. Sherbet has a small, fixed amount of it under federal law. Sorbet has none. Sorbet also has no federal definition of its own, so the closest legal match is a food the rules call water ice.
What federal law says
Sherbet has a U.S. standard of identity in 21 CFR 135.140. The core rule, 21 CFR 135.140(a)(2), begins: “Sherbet weighs not less than 6 pounds to the gallon. The milkfat content is not less than 1 percent nor more than 2 percent.” The same paragraph sets nonfat milk solids at no less than 1 percent and total milk solids at 2 to 5 percent of the finished food. For fruit sherbets it adds: “Sherbet that is characterized by a fruit ingredient shall have a titratable acidity, calculated as lactic acid, of not less than 0.35 percent.”
Fruit sherbets also need a minimum amount of fruit or juice under 135.140(d). The floor is 2 percent for citrus, 6 percent for berries and 10 percent for other fruits. Sherbet can also be flavored with nonfruit ingredients such as spice, coffee or tea, chocolate, confectionery or liqueur (135.140(e)). The label reads ”______ sherbet” with the flavor in the blank, so you see names like orange sherbet.
Sorbet has no U.S. standard of identity. We found no FDA text on the word sorbet at all. The closest standardized food is water ice, 21 CFR 135.160. Under 135.160(a), water ices are made from the same ingredients and in the same way as sherbets, “except that the mix need not be pasteurized.” They use no milk, no dairy ingredient and no egg other than egg white. They are named ”______ ice.”
Fat and milk solids
Sherbet sits in a narrow band: 1 to 2 percent milkfat and 2 to 5 percent total milk solids. For comparison, ice cream needs at least 10 percent milkfat. Water ice, the legal stand-in for sorbet, has no milkfat because it uses no dairy.
The University of Guelph’s Ice Cream Technology e-Book gives example sherbet mixes with 0.5 to 1.5 percent milk fat, 2.0 to 3.5 percent milk solids-not-fat, 24 percent sucrose and 6 to 9 percent corn syrup solids, with fruit added at about 25 percent. For sorbet, it says to leave out the milk and the skim powder.
USDA FoodData Central shows how this plays out in a finished product. It lists orange sherbet at 144 kcal, 2 g fat and 24.3 g sugars per 100 g. Regular vanilla ice cream comes in at 207 kcal, 11 g fat and 21.2 g sugars.
Air and weight
Overrun is the air whipped into a frozen dessert as it churns. More air means a lighter carton. The federal rules control air indirectly, through a minimum weight per gallon.
- Sherbet must weigh at least 6 pounds per gallon.
- Water ice follows the sherbet rules, including the same 6-pound floor.
- Ice cream must weigh at least 4.5 pounds per gallon. By our arithmetic, that caps overrun near 104 percent at a typical mix density. Guelph gives about 100 to 120 percent for standard ice cream.
We found no sourced overrun percentage for sherbet or sorbet. The heavier weight floor does mean both have less room for air than ice cream is allowed.
Serving temperature and how each is made
We found no sourced serving temperature for sherbet or sorbet. The only figure in our sources is for ice cream, which Guelph puts at about 3 °F (-16 °C).
Sherbet starts with fruit or another flavor, sweeteners and 2 to 5 percent milk solids. The mix is frozen while it is stirred, the same basic method used for ice cream. The federal sherbet text sets no egg yolk limit. Water ice is made the same way without the dairy, the mix does not have to be pasteurized, and the only egg ingredient allowed is egg white. At home, both are frozen while stirred, usually in an ice cream machine.
Where the sources disagree
Guelph’s example sherbet mixes start at 0.5 percent milk fat. That is below the federal floor of 1 percent in 21 CFR 135.140(a)(2). The two sources are doing different jobs: Guelph shows sample formulas, and the eCFR sets what can be sold as sherbet. For the legal definition, use the federal numbers.