Plant phenolics as cross-linkers of gelatin gels and gelatin-based coacervates for use as food ingredients

Polyphenols are known to react under oxidizing conditions with side chain amino groups of peptides, leading to formation of cross-links in proteins. Plant-derived phenolic acids and flavonoids were used to prepare cross-linked gelatin gels in bulk and cross-linked gelatin–pectin coacervates in the form of microparticles for use as food ingredients. Gels cross-linked by these materials had greater mechanical strength, reduced swelling, and fewer free amino groups. Dynamic light scattering analyses showed that such cross-linking results in denser polymeric networks and prevents extension of the peptide chains is when the pH is moved away from the isoelectric point. Coacervated gelatin–pectin microparticles when cross-linked became more lipophilic, and were stable at temperatures up to 200 °C, in contrast to un-cross-linked particles that coalesce and/or disintegrate on heating. These properties of cross-linked gelatin gels and gelatin-based coacervates have applications for the development of novel food ingredients.