Impact of high pressure processing on the rheological, thermal and morphological characteristics of mango kernel starch

The effect of high pressure (HP) processing at selected pressures (300, 450 & 600 MPa) for 10 min on physico-chemical and morphological properties of mango kernel starch (MKS) were studied. Peak viscosity of MKS increased with the increase in pressure up to 400 MPa, and then decreased at 600 MPa. During frequency sweep, native and pressurized pastes exhibited predominantly solid-like behaviour in frequency range (0.1-100 rad/s), with G' > G″. Temperature sweep test showed G' and G″ values of native MKS of 1568 and 224 Pa, respectively; pressurization decreased values for both the moduli. tan δ of starches was <1, indicating their elastic behaviour. Shear stress versus shear rate plots for all starch pastes showed shear-thinning behaviour. Thermal properties showed elevation in onset and peak temperatures after pressurization. HP treatment also resulted in narrowing the range (T_c-T_o) for pressurized MKS. Native MKS had ∆H_gel of 5.23 J/g, which upon pressurization reduced significantly (p < 0.05). The endothermic peak, even at 600 MPa did not completely disappear, indicating incomplete gelatinization of starch. The granular structure was not affected by pressure treatment even after 600 MPa. The surface of native MKS appeared smooth whereas HP treatment resulted in rough surface of the starch granules.