High pressure-induced tapioca starch gels: physico-chemical characterization and stability

Gelatinization of tapioca starch (25% dry basis) was induced by high hydrostatic pressure processing (HPP) at 600 MPa under different time and temperature regimes (30 degrees C for 10, 20 and 30 min; 50 degrees C for 10 min; 80 degrees C for 10 min). Textural, thermal and structural properties of the gels were studied and their stability was evaluated after 28 days of refrigerated (4 degrees C) and frozen (-18 degrees C) storage. Thermally induced gels (90 +/- 1 degrees C, 20 min, gel-T) were used as controls. HPP resulted in the formation of harder gels than thermal processing (more significantly at lower processing temperatures) partially preserving the granular structure of the native starch. Longer HPP treatments caused only a slight decrease in hardness that was significant only at longer processing times (30 min). DSC thermograms of high pressure-induced samples showed a more asymmetrical ice-melting peak than that of thermally induced gels. Asymmetry of the peak of HP treated samples was more pronounced in samples processed at lower than at higher temperature. A different starch-water and/or starch/starch interaction may be hypothesized. During storage, all samples became stiffer and the amylopectin recrystallization increased, more extensively in thermally induced than in HPP samples where a stronger starch-starch and/or starch/water interactions may have hindered the recrystallization process.