Starches and fibers treated by dynamic pulsed pressure

Abstract

The effect of dynamic pulsed pressure treatment on water activity, moisture content, water holding capacity (WHC), thermal and rheological properties of corn starch, modified corn starch, microcrystalline cellulose and wheat bran were investigated. Substantial changes in moisture content, water holding capacity, water activity, density, shifts in melting patterns, and reordering of molecules resulted from the pressure treatment. The starches and fibers were made into slurries (starches 200 g/kg; fibers 120 g/kg), fed by gravity into the pressure chamber, and pulsed pressure treated at 120 cycles/min; within chamber residence time for pressure treatment was 1.0 s. Dynamic pulsed pressure of 414 or 620 MPa was generated in the chamber. Slurry flow rate through the pressure chamber ranged from 57 to 100 l/h. 13C NMR analysis of pressure treated starch showed evidence of pressure induced degradation and loss of long range molecular ordering for modified corn starch. Pressure treatment resulted in increases in density and reduction in water holding capacity of cellulose. A 35% reduction in water holding capacity of cellulose was observed, a significant change ( P<0.05) that may potentially increase the amount of cellulose fiber incorporated into foods. Peak melting points of the starches were reduced 10°C at 414 and 620 MPa, and increased with subsequent pressure treatment cycles. The effect of pressure treatment on starches and fibers depend on their source, the degree of pressure treatment, and the number of cycles.