Vol 118 (2005): Proceedings of the Florida State Horticultural Society
Handling & Processing

Effect of seasonal variation on enzymatic hydrolysis of valencia orange peel waste

Mark R. Wilkins
Oklahoma State University
2005 Proceedings of the Florida State Horticultural Society
Published December 1, 2005
  • citrus sinensis,
  • ethanol,
  • peel enzymes,
  • ripening,
  • fruit processing


Approximately 10 million tons of oranges are processed in Florida each year, producing approximately 5 million tons of waste consisting of peel, seeds and segment membranes. Most of this peel is currently dried and pelletized to produce citrus pulp pellets, a low value cattle feed. Several researchers have converted orange peel waste into valuable sugars using enzymatic hydrolysis. After hydrolysis, many of these sugars can be utilized to produce ethanol and other chemicals. This study focuses on the effect of harvest time on sugar yields from enzymatic hydrolyses of Valencia orange peel. Valencia oranges were obtained from the same tree at four times during the 2005 harvest season. A commercial juice extractor was used to extract juice and the processing waste collected for hydrolysis. Cellulose, hemicellulose and pectin were hydrolyzed using pectinase, cellulase and beta-glucosidase enzymes to produce sugars. Arabinose and galacturonic acid yields were affected by the harvest season. Dry matter content of the peel increased over the harvest season. Potential ethanol yields also increased over the harvest season as a result of increased peel dry matter content.