Submitted to: Food and Bioprocess Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/2019
Publication Date: 6/14/2019
Citation: Dorado, C., Cameron, R.G., Manthey, J.A. 2019. Study of static steam explosion of Citrus sinensis juice processing waste for the isolation of sugars, pectic hydrocolloids, flavonoids and peel oil. Food and Bioprocess Technology. 12(8):1293-1303. https://doi.org/10.1007/s11947-019-02300-3.
Interpretive Summary: The majority of oranges grown in Florida are processed into juice. The material that remains after the orange is processed is known as citrus juice processing waste or CPW and is made up of the peel, membrane and seeds. CPW contains sugars, pectin, flavonoids and peel oil that can be used to make various high value products. This work describes the use of a steam explosion system that introduces steam to the CPW under increased temperature and pressure followed by rapid decompression. This causes the CPW to explode into small fragments making the sugars, pectin, flavonoids and peel oil within the CPW more accessible for extraction with water. The goal of this work was to determine the temperature and time needed for steam treatment of CPW in order to get the maximum amount of sugar, pectin, flavonoids or peel oil from the CPW of two major varieties of Florida citrus over the course of the 2016-17 season.
Technical Abstract: In this work citrus juice processing waste from a local Florida processor was subjected to steam explosion using a static bench scale reactor at 130, 150 and 170 degrees Celsius for 1, 2, 4, and 8 minute hold times with the aim of identifying conditions necessary for maximizing the recovery of sugars, pectic hydrocolloids, flavonoids and peel oil. Sugars in steam exploded citrus juice processing waste, from two harvests each of Hamlin and Valencia oranges, were extracted using water or enzymatic hydrolysis. Hydrolysis resulted in a 32-39 percent increase in total sugars. While hydrolysis increased the amount of glucose or fructose it did not necessarily reduce the temperatures and or hold times at which the maximum amounts of sugar were recovered. Peel oil in raw citrus juice processing waste was reduced by as much as 94 percent using steam explosion and has the potential to be recovered by condensation. More galacturonic acid was recovered at 150 and 170 degrees Celsius and 1 minute treatment time for both Hamlin and Valencia citrus juice processing waste but led to increased molecular weight, suspected to be caused by aggregation, and decreased intrinsic viscosity. The higher temperatures and hold times also allowed vastly improved recoveries of the otherwise insoluble flavanone glycoside, hesperidin, with a maximum yield of 64611 parts per million dry weight citrus juice processing waste. Other potential value-added materials such as hydroxycinnamates and the health-benefiting polymethoxylated flavones are also recoverable in high percent yields in the water washes after steam explosion. Estimates are provided of the value of these recoverable products in the citrus juice processing waste of the 2016-17 Florida citrus season.