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Published: 2001-10-20

A friend of ECHO recently wrote to us on behalf of a farmer in Chile who raises naval oranges. Apparently oranges are attheir sweetest when they are still green. When the farmer thinks they have reached the pinnacle of sweetness, he moves them to a greenhouse, where they turn orange. We were asked whether there is a device he can use to test the oranges for sweetness. Danny Blank, ECHO’s farm manager, had this response.

“The least expensive way to accurately test the sugar concentrations in fruits is through an instrument called a refractometer. It is easy to use. A couple drops of juice are placed on a prism glass and then the refractometer is held up to light while a person looks through an eyepiece to get a reading. A certain sweetness should be achieved before certain citrus fruits are harvested. Growers will use the refractometer to get an idea when they can start picking. In Florida, there is an association of growers called Gulf Coast Citrus that has set standards (called brix readings) for each of the different varieties. In another country one would need to come up with his own standards, either ones used in that country or based on taste/experience and comparing taste with refractometer readings.

“FrostProof.com is a good source for obtaining refractometers and other horticultural supplies. They have two models, one for $125.00 and another for $250.00. For sweet oranges, he should get one that ranges between 0-32 degrees Brix.” For more information, contact FrostProof Growers; 512 North Scenic Highway; Frostproof FL 33843; USA. Phone: (863) 635-3620. Fax: (863) 635-3700. E-mail:info@frostproof.com.

Cite as:

ECHO Staff 2001. Citrus Refractometers. ECHO Development Notes no. 73