30D-9 |
Thermal analysis of high-pressure processed starches of different amylose content |
F. FERNÁNDEZ-MARTÍN1, G. Tabilo-Munizaga2, and G. V. Barbosa-Cánovas2. (1) Departamento de Ingeniería, Instituto del Frío (CSIC), Ciudad Universitaria, E-28040-Madrid, Spain, (2) Biological Systems Engineering, Washington State University, P. O. Box 6120, Pullman, WA 99164-6120 Application of high pressure on starches has been studied, so far, in terms of gelatinization and retrogradation phenomena, structure and rheological properties. The objective of this study was to evaluate thermal properties of high pressure treated starches with different amylose content. 30% starch suspensions with amylose contents ranging from 25 to 75% were treated at different pressures from 150 to 650 MPa for 30 min at room temperature. Native and processed samples were physically characterized by their thermal behavior using differential scanning calorimetry (DSC). When thermally processed, common corn starch presented a typical DSC pattern with a gelatinization peak centered at ~72 °C followed by a reversible, broad transition (~85 to 110 °C) of amylose-lipid complexes. Pea starch exhibited, however, the main transition at ~65 °C overlapping a second, irreversible, broad transition extended to ~130 °C. The two high-amylose starches exhibited multimodal DSC traces which included the above lipidic transition. When pressure treated, the two low-amylose starches partially gelatinized from 400 MPa and up, but the two samples with high amylose content did not gelatinized at all, even at 650 MPa. The three high-amylose starches treated at 650 MPa exhibited complex endotherms clearly indicating that they were progressively resistant to high hydrostatic pressure. Retrogradation, as shown by an amylopectin-melting endotherm centered at ~55 °C, was contemporary to gelatinization induced by high-pressure processing, in contrast to the deferred, time-dependent thermal retrogradation observed nearly 10 degrees higher on heated alone samples. DSC demonstrated that thermal and pressure-induced gelatinization were totally different processes. Whatever the process, gelatinization temperatures were not related to the starches amylose content. Except for the first one, higher dilutions than 70% may be required for the other starches to gelatinize in a single transition when thermally processed and likely to be susceptible of pressure processing at current pressures.
Session 30D, Food Engineering: Physical and chemical properties
|