Ultrasonic treatment changes the rheological properties of strawberry pulp via alterations in particle size and the physicochemical properties of pectin.

To investigate the impact of different ultrasonic power densities (2.7, 4.5, 6.3, and 8.1 W/mL) on the rheological properties of strawberry pulp, the changes in physical properties of the pulp and the physicochemical and structural attributes of three pectin fractions in the pulp, water-soluble pectin (WSP), chelator-soluble pectin (CSP), and Na 2 CO 3 -soluble pectin (NSP) were analyzed. Increased power densities damaged the cell fragments in pulp, leading to a decrease in particle size. The apparent viscosity of the pulp initially increased, but subsequently decreased with further increases in power densities. The molecular weight (Mw) of three pectin fractions decreased with increasing power densities, accompanied by structural disintegration and a gradual reduction in apparent viscosity. However, the proportional changes in the monosaccharide composition between the three pectin fractions after ultrasonic treatment were inconsistent. Subsequent analyses showed that the increase in the apparent viscosity of pulp after ultrasonic treatment was related to the reduction in the particle size. Meanwhile, the decrease in the M W of pectin and the disruption of the pectin structure by ultrasonic treatment led to a decrease in the apparent viscosity of both pectin and pulp. [Display omitted] • The particle size of strawberry pulp decreased with ultrasonic power densities. • Pulp's viscosity increased gradually before rapidly decreasing with power densities. • The structures of pectin were affected and their M w decreased after ultrasound. • The apparent viscosity of three pectin fractions decreased after ultrasound. • Particle size and pectin jointly influenced the rheological properties of pulp. [ABSTRACT FROM AUTHOR]