Enhanced electrostatic interactions in tomato cell suspensions

The natural consistency of processed tomato products arises from cell wall particles and the interactions between them. In this study, ion exchange resins were used to investigate these interactions. Two types of resins were used, a hydrogen form cation exchange resin and an anion resin in the hydroxide form. Serum phase of tomato suspensions were treated with either a cationic or an anionic resin to exchange various ionic compounds with hydrogen and hydroxide ion respectively. The treated serum was then reconstituted to the tomato pulp and the suspension was re-suspended with shear. The linear storage modulus varied with the different types of resin treatment. Samples treated with the anion exchange resin resulted in a higher modulus than the untreated tomato puree and the puree treated with the cation resin. Effect of the resins was dependent on the concentration of resin used. The anion treated sample resulted in a network formation which was quite sensitive to pH and was attributed to long range electrostatic interactions caused by protein–pectin interactions. Using Infrared spectroscopy the conformational changes in the protein structure as a result of resin treatment was detected by analyzing the amide-I and amide-II regions.