Continuous process for enhanced release and recovery of pectic hydrocolloids and phenolics from citrus biomass

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

Submitted to: Journal of Chemical Technology & Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2015
Publication Date: 1/27/2016
Citation: Cameron, R.G., Chau, H.K., Manthey, J.A. 2016. Continuous process for enhanced release and recovery of pectic hydrocolloids and phenolics from citrus biomass. Journal of Chemical Technology & Biotechnology. 91:2597-2606. doi: 10.1002/jctb.4854.

Interpretive Summary: Increased valorization of food wastes is an important component of national and international food security. Agricultural processing wastes, which are an order of magnitude greater than food wastes, provide opportunities for valorization and new product creation. Worldwide citrus processing waste (CPW) was projected to be nearly 4.2 million dry metric tons (MT) for the 2013 – 2014 harvesting season, containing approximately 840,000 MT of pectic material and 190,000 MT of flavonoids and related phenolics. The United States (Florida) CPW for the 2012 – 2013 harvesting season was 550,000 dried MT containing nearly 110,000 MT of pectic material and 25,000 MT of flavonoids and related phenolics. Nearly 95% of oranges grown in Florida are processed for juice. Historically the resulting CPW, largely consisting of citrus peel and smaller amounts of seeds and segment membranes, is converted to a dried animal feed. Production of this material is energy intensive and it is marketed at a relatively low value of about $0.08 - $0.10 per lb. In light of efforts to increase the utility and valorization of CPW we have focused on the two most highly valued classes of compounds it contains, pectic material and phenolics. We have presented data demonstrating the successful application of a continuous pilot scale process to release pectic material and phenolic compounds from citrus processing waste by steam-explosion. The released compounds were subsequently recovered with a simple water wash. Recovery of pectic material ranged from 65% - 80% of the amounts present in steam-exploded CPW. Functionality could be introduced into the steam-exploded CPW by a mild chemical modification of the released pectic material present in the CPW.

Technical Abstract: During the 2012/2013 harvesting season the Florida citrus processing industry produced 0.55 × 106 metric tons (MT) of dried citrus pellets from citrus processing waste (CPW). The citrus pellets were marketed as a low value animal feed which may sell for $0.22 per kg or less. This biomass also contained nearly 110,000 metric tons of pectic hydrocolloids and 25,000 metric tons of flavonoids and related phenolics. A continuous process is required to release and recover these valuable coproducts in order to enable the availability of the functionality they contain. By injecting steam into the flow of citrus peel through a pipe at 150 °C we could release pectic hydrocolloids and phenolic compounds from the waste biomass. The resulting steam exploded peel was washed with water and the pectic hydrocolloids and phenolic compounds were recovered in the wash water. Over two seasons an average of 72% of the pectic hydrocolloids were recovered. Additionally, 41.1% of the polymethoxylated flavones, 11.4% of the flavanone glycosides, 85.2% of the limonoids and 100% of hydroxycinnamates were recovered with the water wash.