Effect of Process Conditions on Composition and Properties of Pectin and Apparent Viscosity of Sterilized and Concentrated Pulp of Tomatoes

Abstract

Tomato pulp treated at industrial unit conditions was utilized to determine the physical and chemical changes on pectin substances properties and its correlation to the consistency of tomato pulp, hot break pretreated product, concentrated pulp at 70oC/30 min and sterilized pulp at 102oC/10 min. The assays carried out were: apparent viscosity, serum separation degree, precipitate weight ratio, insoluble solids and pectic substances as uronic acid, fractionated according to their solubility in water, 0.2% ammonium oxalate, 0.05N hydrochloric acid and 0.05N sodium hydroxide solutions. Concentration and sterilization cause reduction in the apparent viscosity, the precipitate weight ratio and increasing of the serum separation degree of the suspension compare to tomato pulp submitted only to pre-treatment and those conditions didn’t affect significantly the total uronic acid and insoluble solids in water. However, changes occurred on chemical composition, detected into fractions of pectic substances expressed as uronic acid in all samples; results for pre-treated pulp sample to sterilized pulp samples (final product) show a high water solubilization of the fractions of the pectic substances, around 31%, confirmed by an increment of 24% in the water soluble fraction. A high correlation was established between the concentration of water-insoluble fractions and apparent viscosity, precipitate weight ratio and serum separation degree.