Covalent conjugation of bovine serum album and sugar beet pectin through Maillard reaction/laccase catalysis to improve the emulsifying properties

The study aims at improving the emulsifying stability of sugar beet pectin (SBP) by covalent coupling of proteins to polysaccharide. Laccase and Maillard reaction in a controlled dry state condition (85 degrees C, 79% relative humidity for 5 h) were adopted to kinetically control the formation of hetero-covalent linkages between SBP and bovine serum albumin (BSA). The formation of BSA-SBP conjugates was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and peak position using gel permeation chromatography, multi angle laser light scattering and refractive index. The decrease rates of tyrosine and ferulic acid contents were positively correlated with the laccase dosage. The optimum condition of laccase catalysis was 500 U/g sample powder at a BSA/SBP weight ratio of 0.25. Measurements of particle size distribution and average particle size showed that emulsifying performance of BSA-SBP conjugation improved greatly compared with individual BSA and SBP. Emulsions stabilized by BSA-SBP conjugates were less susceptible to environmental stresses, such as at the present of salts, low pH, thermal and freeze-thaw treatments. Covalently conjugated SBP and proteins has greatly potential applications as novel emulsifier in food industry. (C) 2016 Elsevier Ltd. All rights reserved.