Approximately 0.7 - 1 � 106 dry tons of citrus processing waste (CPW) are produced annually in the United States.  CPW is sold as animal feed but often the financial return does not exceed the production cost.  Polysaccharides comprise 40% of the total CPW dry matter of which the hydrocolloid pectin is the major component. CPW was steam treated to extract pectic fragments (PFs) as a value added co-product.  PFs were extracted in high yields (~ 70% of available galacturonic acid), along with other polymeric hydrocolloids � arabinans (50% � 70% of available arabinose), galactans (70% � 85% of available galactose) and arabinogalactans. The extracted hydrocolloids ranged in size from small oligomers to polymers of ~ 700,000 g mol-1. Acidified treatments led to greater fragmentation of water soluble hydrocolloids compared to non-acidified treatments (39,230 g mol-1 vs.552,400 g mol-1 for a two min treatment).  Steam treatment of CPW provides for rapid, efficient fragmentation of protopectin into PFs with a high degree of methylesterification (DM) that, along with arabinans and galactans, can be recovered by ethanol precipitation.  Alternatively, enzymatic treatment produced PFs with a very low DM that can be recovered and purified by precipitation with dilute HCl.  Calcium mediated functionality following in-situ demethylesterification of released PFs was explored by oscillatory testing.  G' and G� values obtained from enzymatically demethylesterified CPW demonstrated the formation of weak gels possessing psuedoplastic properties often associated with pectin.  The steaming process for preparation of PFs is environmentally friendly and no toxic chemicals are introduced.  Extracted sugars can be used in beverages or fermentations to produce ethanol and other compounds.

Extraction, recovery, and functionality of pectic hydrocolloids from citrus processing waste

248th National Meeting (2014)

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