Microscopic evidence for Ca2+ mediated pectin-pectin interactions in carrot-based suspensions

This study explored the use of fluorescently labeled pectin to obtain evidence for Ca2+ mediated pectin-pectin interactions in situ. Specifically, carrots were either blanched at low temperature (LTB) or blanched at high temperature (HTB) to activate or inactivate endogenous pectin methylesterase, respectively. Consequently, pectin in tissue particles of LTB and HTB carrots exhibited low degree of methylesterification (DM) and high DM, respectively. Pectin present in the LTB carrot serum exhibited a lower DM, was more branched, and showed a higher molar mass compared to HTB carrot serum pectin. Ca2+ mediated pectin-pectin interactions were influenced by serum pectin molecular structure, increased with increasing pH and Ca2+ concentration, and decreasing DM. Presence of more linear pectin in the serum created a competition, leading to less intense interactions between labeled pectin and pectin at tissue particle surfaces. Generally, the most intense Ca2+ mediated pectin-pectin interactions were observed for pectin of LTB carrot particles.