Biosorption properties of citrus peel derived oligogalacturonides, enzyme-modified pectin and peel hydrolysis residues

Randall G. Cameron, Gary A. Luzio, Wilbur W. Widmer, Muhammad Iqbal

Abstract


A citrus processing industry priority is obtaining added value from fruit peel. Approximately one-half of each processed fruit is added to the waste stream. Peel residue is composed mainly of water (~80%), the remaining 20% (solid fraction) consists of pectin, soluble sugars, cellulose, proteins, phenolics, etc. Viewing these constituents in light of exploiting potential functionality and creating added value at the same time as diverting material away from the feed mill or land fill, pectin provides enormous opportunity. To create a new technology centered on pectin structure and concomitant functionality, we are investigating methods to precisely engineer pectin structure and correlate it to function. A valuable pectin functionality, resulting from its polyanionic character, is its biosorption capabilities. In the past several years we have developed analytical techniques and biochemical methods to enzymatically modify pectin structure, characterize these structural alterations and determine their effect on rheology and calcium sensitivity. Here we present data on the biosorption properties of modified pectins and pectin fragments using lead as a model cation. The greatest Pb sorption capacity (Mean = 373.3 mg·g–1; S.E. = 1.595; P > 0.001) was observed in the Medium DP size-class of galacturonic acid oligomers. A comparison of enzymatically demethylated (blockwise) homogalacturonans indicated that the 60% and 50% DM pectins treated at pH 4.5 had a significantly greater sorption capacity than higher DM or pH 7.5 treated samples.

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283