Cloudy is Good--When It Pertains to Citrus
May 7, 1997
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.
USDAs 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 juices 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;