Recovery of pectic hydrocolloids and phenolics from Huanglongbing related dropped citrus fruit

Authors: Cameron, Randall - Randy; Chau, Hoa - Rose; Hotchkiss, Arland; Manthey, John

Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2017
Publication Date: 3/12/2017
Citation: Cameron, R.G., Chau, H.K., Hotchkiss, A.T., Manthey, J.A. 2017. Recovery of pectic hydrocolloids and phenolics from Huanglongbing related dropped citrus fruit. Journal of the Science of Food and Agriculture. 97:4467-4475. https://doi.org/10.1002/jsfa.8310.
DOI: https://doi.org/10.1002/jsfa.8310

Interpretive Summary: The Florida citrus industry is in dire straits. Harvests have been reduced nearly 75% since 2003. Growers and juice processors are both suffering. The cause is a bacteria spread by a sucking insect. To date there is no cure, only stop gap, temporary and poorly performing fixes. A major symptom of this disease is known as Preharvest Fruit Drop. The number of fruit that fall from the trees prior to harvesting has increased dramatically. Recovering this fruit and using it to create value added byproducts would benefit the entire industry. We have demonstrated that this fruit can be used as a feedstock in our newly developed continuous, steam-explosion process enabling the recovery of highly valued pectic hydrocolloids and phenolic compounds using a simple water wash. Implementation of this technology and the proper marketing of the resulting products would provide much needed income for the industry.

Technical Abstract: Citrus fruit drop has dramatically increased concomitantly with continued declining tree health and crop harvest size caused by HLB infection. This loss of harvestable fruit has been detrimental to both growers and processors. If this fruit could be recovered and converted to alternative value added coproducts the citrus industry would benefit. Therefore, we have explored the potential of using this fruit as a feedstock in our newly developed pilot scale continuous steam explosion process. This new process releases highly functional pectic hydrocolloids and several major classes of phenolic compounds from their intracellular entrapment allowing them to be recovered by a simple water wash. It also facilitates the recovery of limonene. To explore the potential of this process to gain value from dropped fruit we collected dropped Hamlin fruit from the USDA, Ft. Pierce, Picos Rd. farm in December of 2014. Approximately 250 kg of dropped fruit was collected. Whole fruits (~130 kg) were converted to steam exploded tissue using our continuous pilot scale process. Sugar composition of raw fruit and steam exploded mass was determined. Recovered pectic hydrocolloids and phenolic compounds were characterized. Pectic hydrocolloids comprised 7.8% of the dry material in the dropped fruit. Following the steam explosion process nearly all of the pectic hydrocolloids were recoverable. The pectic hydrocolloids could be functionalized in-situ or separated from the milieu. In addition, ˜40% of the polymethoxylated flavones, ˜10% of the flavanone glycosides, ˜85% of the limonoids and nearly ˜100% of hydroxycinnamates were recovered with the water wash.