Electrostatic pectin-pectin interactions and in vitro bioaccessibility of calcium and iron in particulated tomato-based suspensions

Abstract

This study explored the pectin structure-function relationship in tomato-based suspensions. Particularly, electrostatic pectin-interactions were investigated and subsequently linked to the in vitro bioaccessibility of Ca and Fe-ions in tomato-based suspensions. Process tomatoes were either treated at high-pressure (HP) to selectively maintain pectin methylesterase enzyme (PME) or blanched at high temperature (HB) to inactivate all the endogenous pectin-degrading enzymes. The samples were disintergrated into purée and incubated to allow the action of PME (if any). Structure characterisation showed that pectin in HP tomato tissue particles was of a lower degree of methylesterification (DM) compared to pectin in HB tomato tissue particles. Pectin in HP tomato serum was of a lower DM, was less linear and was of a lower molar mass compared to the high DM, highly linear and high molar mass pectin in the HB tomato serum. Exploring the pectin-interactions revealed that Ca2+ mediated pectin-pectin interactions in reconstituted HP tomato-based systems were stronger than in HB tomato-based systems. These interactions were influenced by the molecular structure of pectin in the serum fraction of the tomato suspensions, and improved with increasing Ca2+ and pH. Investigation of the essential mineral content showed that HP and HB tomato-based suspensions contained similar amounts of Ca and Fe-ions (9.8 ± 0.8 and 0.39 ± 0.1 mg/100 g of purée, respectively). Ca and Fe-ions were more bio-accessible in HB tomato-based suspensions (two times) than in HP tomato-based suspensions and the bioaccesibility of ions decreased with increasing electrostatic pectin-interactions.status: publishe