Structural modifications and thermal transitions of standard maize starch after DIC hydrothermal treatmentReport as inadecuate




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* Corresponding author 1 LEPTIAB - Laboratoire d-Étude des Phénomènes de Transfert et de l-Instantanéité : Agro-industrie et Bâtiment 2 LMTAI - Laboratoire Maîtrise des Technologies Agro-Industrielles 3 GEPEA - Laboratoire de génie des procédés - environnement - agroalimentaire 4 Institut National de la Recherche Agronomique, Centre de Recherches Agroalimentaires

Abstract : Standard maize starch was hydrothermally treated by Instantaneous Controlled Pressure Drop DIC process at three pressure levels 1, 2 and 3 bar corresponding to the temperatures of 100, 122 and 135 C at 13–27% moisture, respectively. The structural effects of various hydrothermal conditions were examined with differential scanning calorimetry DSC and wide-angle X-ray diffraction. In order to understand the changes that occur during DIC treatment, melting endotherms of native maize starch at various moisture contents were determined. The gelatinization temperatures of DIC treated standard maize starch increased with DIC treatment. The transition temperatures To, Tp are closely related to the combined effect of pressure and processing time. At approximately 10 min of processing time, To and Tp were 65.7 and 72.3, 68.8 and 73.6 C, 74.8 and 79.8 C for pressure levels of 1, 2 and 3 bar, respectively against 63.1 and 69.6 C for native starch. DIC treatment narrowed the gelatinization temperature range and decreased gelatinization enthalpy DH, as the severity of processing conditions increased. DH decreased from 11.4 J g1 native to 11.0 1 bar, 9.0 2 bar and 1.7 J g1 3 bar for treated maize starch during approximately 10 min. Relative crystallinity of hydrothermally treated starch decreased with increasing DIC conditions. The A-type crystalline pattern was progressively lost at pressure level P2 bar and substituted by the Vh-type X-ray diffraction pattern, corresponding to the formation of amylose–lipid complexes. For severe DIC conditions pressure level of 3 bar, the substitution was completed. Microscopic observations revealed progressive loss of the birefringence of DIC treated starch granules except at low pressure 1 bar, while the integrity of starch granules was preserved for all the conditions. These modifications that reveal important changes in the crystalline organization of the starch granules are related to their functional properties.

Keywords : Standard maize starch DIC hydrothermal treatment Thermal transition X-ray diffraction





Author: Zoulikha Maache-Rezzoug - Ikbal Zarguili - Catherine Loisel - D. Queveau - Alain Buleon -

Source: https://hal.archives-ouvertes.fr/



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