Submitted to: Proceedings of Florida State Horticultural Society
Publication Type: Proceedings
Publication Acceptance Date: February 13, 2004
Publication Date: April 1, 2004
Citation: Cameron, R.G., Grohmann, K., Hotchkiss, A.T. 2003. Separation and detection of oligogalacturonides. Proceedings Of Florida State Horticultural Society. 116:413-417. Interpretive Summary: Pectin, extracted from citrus fruit peel, is used in the food industry as a gelling and stabilizing agent. Potential industrial uses for pectin, modified pectin or pectin containing bio-based products include additives for a variety of manufactured products, ion exchange resins, flavor or aroma encapsulators and as coatings. The functional properties of pectin depend on its chemical structure. Small changes in its structural properties can produce very different functional properties. To characterize these small structural changes we must separate and measure very small fragments of the original material. Detecting and quantifying these small fragments has been especially difficult. The techniques described in this work improve our ability to both detect and to quantify these small fragments. These techniques will allow us to reconstruct the modified structural features that resulted in new or improved functional qualities.
Technical Abstract: A high performance size exclusion chromatographic method incorporating an evaporative light scattering detector (ELSD) was developed to quantify galacturonic acid (GA) oligomers. Values of k for GA monomer ranged from 0.16 in water to 0.67 in 100 mM acetic acid. In 40 mM acetic acid calibration curves for GA monomer, dimer and trimer were nearly identical and linear up to a concentration of 0.75% (w/v). However, this buffer precipitated polygalacturonic acid (PGA) and it could not be eluted from the column. An NH4OAc buffer at pH 3.7 also produced baseline resolution and linear calibration curves for mono-, di- and tri-GA, and could be used to estimate the concentration of tetrameric, pentameric and hexameric GA. With an NH4OAc mobile phase both pectin and PGA could be detected. A high performance ion exchange chromatography method also was pioneered for use with the ELSD. Both ammonium acetate and ammonium formate gradient buffer systems were developed for use with the ELSD. Over thirty chromatographic peaks, representing oligogalacturonides of increasing degrees of polymerization were separated with the ammonium formate buffer system.