Structural modifications and thermal transitions of standard maize starch after DIC hydrothermal treatment

International audienceStandard 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

Thermisation de farine par MICRO-ONDES ; application à la désinsectisation, à la correction (a-am.) et aux farines fonctionnelles

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Effect of spray-drying and storage conditions on the physical and functional properties of standard and n3 enriched egg yolk powders

This study aimed to evaluate the effect of the processing and storage conditions on the physical and functionalproperties of egg yolk (EY) powders. The spray-drying temperature (160 C vs. 180 C), storage temperature (15 C vs. 30 C) and time (1, 2, 4 and 8 months) and n 3 enrichment through hen diet were investigated. The spray drying temperature and storage conditions modified the water content, water activity and the particle size distribution of EY powders. Flowability of the powders and the emulsifying properties were not significantly affected from an industrial point of view. On the opposite, the viscosity increased with the spray-drying temperature as well as the temperature and time of storage in rehydrated powders. Powders prepared with n 3 enriched egg yolks exhibited lower melting peaks temperatures, a marked yellow colour and higher fluidity of the solutions, but the overall properties remained unchanged. This study clearly attests the possibility of an industrial production of n 3 enriched EY powder