Extraction of Sugars, Pectic Hydrocolloids, Flavonoids and Peel Oil from Orange Juice Processing Residues By Steam Explosion and Their Potential Value

In the 2016-2017 season, 96 percent or 2.7 million metric tons of oranges produced in the state of Florida were processed into juice leaving behind 1.2 million metric tons of peel, rag, juice sacs and seeds. These orange juice processing residues are currently pressed and dried into low value cattle feed but contain sugars, pectic hydrocolloids, flavonoids and peel oil that if extracted, can be used in high value products. Therefore, we investigated the use of steam explosion for extraction of sugars, pectic hydrocolloids, flavonoids and peel oil from the two major Florida orange juice processing varieties and calculated their potential value. Early and late harvest samples of Hamlin and Valencia juice processing residues from the 2016-2017 season were subjected to steam explosion in a batch system at 130, 150 and 170 degrees Celsius for 1,2,4, and 8 minute hold times. The resulting steam exploded material was then analyzed for sugars, pectic hydrocolloids, flavonoids and peel oil. In general, more than half of the available glucose and fructose was extracted at the highest temperature and longer hold times. This was also the case for the flavanone glycoside, hesperidin. Steam explosion has the potential to volatilize up to 94 percent of the available peel oil. Galacturonic acid, the major constituent of pectic hydrocolloids, could be recovered at higher temperatures and shorter hold times but with increased molecular weight due to suspected aggregation. It was determined that millions of dollars of potential value exist in the residues based on the amount of glucose, hesperidin, peel oil, and galacturonic acid that could be extracted by steam explosion from the residues produced during the 2016-2017 Florida citrus season.