Cloudy is Good--When It Pertains to Citrus Juices

Believe it or not, we like our orange juice cloudy. A pitcher of orange juice sitting in the refrigerator that has separated into a layer of solids at the bottom and clear liquid at the top is considered spoiled. Consumers tend to think that clear, unclouded juice has been watered down or lacks freshness. The marketing of fresh citrus juices is severely restricted because an enzyme present in citrus peel and fruit clarifies the juice, eliminating the cloud.

U.S. Department of Agriculture scientists in Winter Haven, Fla. discovered that a form of the enzyme pectinmethylesterase in citrus peel causes the most rapid juice cloud breakdown. Forms of the enzyme present in the fruit itself work more slowly to decloud juice. The enzyme also causes frozen concentrated citrus juice to gel and causes bits of solid matter to form in beverages containing citrus juices.

USDA’s Agricultural Research Service has signed a Cooperative Research and Development Agreement with FMC Corporation, Lakeland, Fla., to see if levels of the peel enzyme in juice are affected by the way the juice is extracted from fruit. FMC is a major producer of machinery used in processing juice from fruit.

If the research leads to a juice extraction method that cuts the amount of peel enzyme in juice, it would extend juice’s shelf life, increasing the geographic market area for fresh citrus juices.

Scientific contact: Randall C. Cameron, ARS Citrus and Subtropical, Products Laboratory, Winter Haven, Fla; phone (941) 293-4133, fax (941) 299-8678; rcameron@asrr.arsusda.gov