Renewable Citrus Products Association

Renewable Citrus Products Association

Frequently Asked Questions


Q: Where do citrus oils come from?

A:  The peel is the source of the major portion of the fruit’s essential oils. The primary constituent of these oils is the terpene d-limonene.

Q: Where in the peel are the citrus oils stored?

A:  Citrus peel contains oblate-shaped oil glands in the flavedo, which extend to different depths into the albedo of all the different citrus fruits. These cells contain chemicals discharged by metabolic processes of the fruit, which give each type of citrus a characteristic aroma and flavor. (Braddock 1999)

Q: What are the ingredients for citrus oils?

A:  Citrus trees send water up from the roots by osmosis to the leaves and bring carbon dioxide into the leaves through pores called stoma. These chemical building blocks along with sunlight for photosynthesis allow the oils to form and concentrate in the peel of the fruit. Citrus oils are expressed from the peel during the juicing process.

Q: Where did citrus originate?

A:  Citrus originated in Southeast Asia. Citrus was noted in literature in China in 1000 BC. The Chou dynasty references kumquats and mandarin. It spread to India, East Africa, Mediterranean, and Canary Islands. Columbus is credited with bringing citrus plants to the Americas.

Q: What were the early collection methods for citrus oils?

A:  Lemon oils were made for centuries in Sicily by pressing peel in wooden screw presses or by hand squeezing oil-saturated sponges touched against scarified fruit. Early commercial recovery of orange oil in the United States used the hand-sponge technique. (Braddock 1999)

Q: What is the distribution of varieties of citrus?

A:  Statistics on world citrus production show: oranges 64%, tangerines 21%, lemon/limes 11%, and grapefruits 4%.

Q: What percent of oranges are used for juice?

A:  Florida and Brazil are the largest orange producers, growing 60% of the world’s oranges and processing 85% of their production into juice and citrus oils. (Braddock 1999)

Q: What kind of orange varieties are grown in Florida?

A:  The Hamlin, Pineapple Oranges, Navel, Temple, and Valencia have overlapping seasons that lasts mid-September through the end of July in Florida. Brazil grows mostly the Pera orange ripening June through December. Nearly the entire California crop goes to market as fresh fruit.

Q: Is d-limonene used in food products?

A:  Citrus oils are commonly found in baked goods, beverages, chewing gum, frozen diary, hard candy, pudding, and of course orange juice.

Q: What are some of the non-food applications for

A:  Citrus oils are commonly used in air fresheners, fragrances, general purpose degreasers and cleaners, hand cleaners, insect repellents, household cleaners, pharmaceutical applications, and plastic recycling operations.

Q: What are terpenes?

A:  Nature makes the isoprene molecule (C5H8) that has five carbons and eight hydrogen atoms from carbon dioxide absorbed from the air and water. Two isoprene molecules can combine in various forms to produce terpenes. The d-limonene found in citrus oils is one of many different kinds of terpenes.

Q:  I saw a picture of a citrus tree that had both full-size fruit and blossoms on the same branch.  How can that be?

A:  Citrus trees are some of the few fruit trees in the world that bloom and ripe concurrently - that is, they have blossoms and fruit on the same tree at the same time.

In most citrus there is only one blooming period, about 2-4 weeks after winter dormancy, while in some cases, like in limes and partially in lemons, several blooms occur throughout the year. Trees in particularly temperate areas can have fruit ripening year-round (or almost). Commercial trees, however, tend to be harvested once or more often during their season, which is about 6 months long.

Citrus fruits are modified berries known as hesperidia.  Fruit growth duration is different according to the species or varieties, from some mandarins that will need less than five months from flowering to maturation, to some sweet oranges( Valencia) that need more than one year.

Out of the three citrus tree genera Poncirus, Fortunella and Citrus, only Poncirus is deciduous while the two other are evergreen.  Several leaf flushes occur around the year, depending on the climate.  Leaves usually stay on the trees for a period between 9-24 months or even more.

Renewable Citrus Products Association 1101 17th Street NW, Suite 700, Washington, DC, 20036
Ph: 202-293-5800 Fax: 202-463-8998