The influence of pH and enzyme cross-linking on protein delivery properties of WPI-beet pectin complexes

The incorporation of bioactive proteins and peptides into food is associated with the loss of bioactivity due to deactivation in complex food matrices and in digestion systems. In this study, two different types of protein carriers, i.e. biopolymer complexation and complex coacervation were fabricated using whey protein isolation (WPI, 6 wt%) and beet pectin (BP, 1.25 and 1.00 wt%) at pH 5.5 and 3.5, respectively. The release of the encapsulated FITC-BSA, a model bioactive protein, in both carriers in the absence and presence of laccase was investigated at both pH 7.0 and 4.0. Release of FITC-BSA from both lyophilized WPI-beet pectin biopolymer complexation and complex coacervation were biphasic with an initial burst release followed by a slower release phase. The addition of laccase in biopolymer complexation increased the loading efficiency from 44.95% to 52.15% and slowed down the burst release of FITC-BSA but did change the biphasic release pattern. Laccasecross linked WPI (6 wt%)-BP (1 wt%) complex coacervation had highest FTTC-BSA loading efficiency (96.90%). The release of the embedded FITC-BSA in this carrier at both pH 4 and 7 was in a gradual manner and the profile can be fit to zero order kinetics over the 72 h study period suggesting enzymatically reinforced complex coacervation between the protein and the negatively charged beet pectin can restrain the burst release of FITC-BSA. These results indicate that laccase cross-linked WPI-beet pectin complex coacervation can be a good carrier system for delivering hydrophilic bioactive proteins or peptides successfully with enhanced loading parameters and sustained release profiles.