Laccase mediated conjugation of sugar beet pectin and the effect on emulsion stability

Laccase catalyzes intermolecular cross-links between ferulic acid of sugar beet pectin (SBP). Conjugation of SBP by laccase was confirmed by increased molecular weight, monitored by size exclusion chromatography, combined with multi-angle laser light scattering (SEC-MALLS), by reduced ferulic acid concentration detected at UV 325 nm, as well as by increased particle size. In addition, cross-linked SBP developed a more compact, branched structure as verified by a smaller root mean square (RMS) when molecular weight increased. Emulsions prepared with conjugated SBP had significantly smaller d(4,3) diameter and uniform droplet size, with more negative zeta-potential than non-treated SBP, during 30 days storage at 37 degrees C. The d(4,3) diameter was 5.3 mu m and 3.8 mu m for SBP and conjugated SBP, respectively. Covalently conjugated SBP has increased functionality and improved emulsion stability, most likely attributable to development of thick layer at the oil interface. (C) 2011 Elsevier Ltd. All rights reserved.