Study of Static Steam Explosion of Citrus sinensis Juice Processing Waste for the Isolation of Sugars, Pectic Hydrocolloids, Flavonoids, and Peel Oil
In this work, citrus juice processing waste (CPW) from a local Florida processor was subjected to steam explosion using a static bench scale reactor at 130, 150, and 170 °C for 1, 2, 4, and 8 min 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 CPW, from two harvests each of Hamlin and Valencia oranges, were extracted using water or enzymatic hydrolysis. Hydrolysis resulted in a 32–39% 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 CPW was reduced by as much as 94% using steam explosion and has the potential to be recovered by condensation. More galacturonic acid was recovered at 150 and 170 °C and 1 min treatment time for both Hamlin and Valencia CPW 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 64,611 ppm dw CPW. 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 CPW of the 2016–17 Florida citrus season.
KeywordsSTEX Pectin Glucose Fructose Sucrose Hesperidin
The authors would like to express their gratitude to Sandra Matlack, PeiLing Li, and Veronica Cook for providing technical support for experiments and analyses. The authors would also like to thank Justice Widman for providing technical support for peel oil analyses.
Compliance with Ethical Standards
Conflict of Interest
The authors declare that they have no conflict of interest.
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