A highly efficient enzymatic technique for peeling oranges and other citrus that produces cleaner fruit more cheaply than current manual peeling has been developed by chemists at the U.S. Department of Agriculture's laboratory in Winter Haven, Fla. The technique could reverse the decline in the U.S. peeling and sectioning industry caused by lower labor costs overseas. Only two peeling and sectioning plants now operate in the United States, compared to 12 in the 1970s.
Citrus to be peeled are first scored with a knife, then immersed in a dilute solution of pectinase, an enzyme widely used in jams and jellies, according to USDA's Robert A. Baker. Brief exposure to a vacuum pulls air out of the citrus, allowing the enzyme to be sucked back under the skin when pressure is restored. In 15 minutes to an hour, the enzyme dissolves pectin in the albedo, the white fleshy membrane inside the peel.
The peel then virtually falls off, Baker said, and individual sections can be readily separated. There is no loss of edible fruit, he said, and the enzyme does not alter its taste.