The effect of ternary anthocyanin-iron ion-pectin interactions on spectral properties and stability
** Lecture will be given in English**
Abstract:
In recent years, the shift toward healthier eating habits has also promoted the search for natural food additives, such as natural food colorants, as alternatives to synthetic ones due to possible negative effects. Anthocyanins, a subgroup of polyphenolic natural pigments, are promising options because of their vivid colors and potential health benefits. However, their use as natural blue colorants is limited by their pH-dependent structural changes, especially in acidic environments, and chemical instability. Although polysaccharide-based stabilization is often investigated, maintaining a stable blue hue remains a major challenge.
This research introduces a novel approach using ternary Pectin-Iron ion-Anthocyanin (PIrA) complexes. By utilizing apple pectin enriched with iron ions as molecular anchoring sites for anthocyanins, we successfully increased anthocyanin binding and enhanced blue color stability. The complexation of selected anthocyanins with the iron in the iron-enriched pectin was studied in both single and multi-component models. This complexation was found to be structure-dependent, with the number of hydroxyl groups on the B-ring and the size of the conjugated sugar significantly influencing binding affinity and spectral properties.
To assess the practical potential of this system, pre-formed PIrA complexes were incorporated into a fermented dairy gel matrix. At an acidic pH of approximately 4.3, the complexes successfully maintained a stable blue color and prevented the precipitation seen in systems without pre-complexing. Finally, in vitro simulated gastrointestinal digestion showed that PIrA complexation significantly lowered anthocyanin bioaccessibility in the upper gastrointestinal tract. This indicates that the anthocyanins stay associated with the matrix, potentially enhancing their delivery to the colon for subsequent colonic absorption metabolism.
Overall, the ternary system represents a versatile strategy for both achieving stable natural blue colors in complex food matrices and modulating the digestive fate of polyphenols.
