Replacing EDTA: Challenges and Advances in Low pH Affinity Screening Techniques

The replacement of synthetic antioxidants like EDTA with natural, metal chelating antioxidants is of significant interest, especially for use in low pH, high-fat products such as mayonnaise. Traditional screening methods for metal chelating antioxidant activity typically involve time-consuming storage experiments in basic food systems, where ferrous iron is added as a prooxidant. However, these experiments usually do not clarify the antioxidant mechanisms. My Ph.D. research focuses on employing both established and novel techniques to assess the metal chelating activity of peptides and hydrolysates, particularly in challenging low pH conditions.

A significant aspect of this research involved modifying Immobilized Metal Affinity Chromatography (IMAC) and Surface Plasmon Resonance (SPR) for use at low pH, departing from their standard use at neutral pH. In particular, the use of IMAC at pH 4 allowed for screening for Ni2+ and Fe3+ chelating activities in new potential antioxidants among synthetic peptides. Our findings revealed no correlation between the chelating activities of peptides for Ni2+ and Fe3+, and similarly, no direct correlation between Fe3+ chelating activity and antioxidative efficacy in mayonnaise, highlighting the complexities involved in applying these findings to food systems.

Moreover, the adaptation of SPR to low pH for metal ion affinity analysis proved challenging due to unexpected interactions with the sensor chip, illustrating the need for careful modification of these techniques for acidic conditions.

These outcomes emphasize the importance of methodological adaptation and innovation in analytical chemistry within food science. The research demonstrates that adapting techniques like IMAC and SPR to low pH environments not only provide new insights but also introduces unique challenges. This study contributes to a more nuanced understanding of the complexities involved in screening for metal chelating activity in potential natural antioxidants, highlighting the critical role of tailored analytical approaches for specific food matrix conditions.