Study of DIC hydrothermal treatment effect on rheological properties of standard maize (SMS), waxy maize (WMS), wheat (WTS) and potato (PTS) starches

International audienceStandard maize (SMS), waxy maize (WMS), wheat (WTS) and potato (PTS) starches were hydrothermally treated by Instantaneous Controlled Pressure Drop (DIC) process at different pressure levels (1, 2 and 3 bar) corresponding to the temperatures of 100, 122 and 136 C, respectively. The rheological properties and particle size of treated starches under various conditions were compared to the native ones. The results showed for all starches, except for WTS, a reduction of the consistency coefficient and the yield stress (s0) with increased intensity of the hydrothermal treatment conditions. Furthermore, s0 vanished for severe treatment conditions. The DIC treatment yielded an increased fluidity and a loss of the conservative modulus of the pastes, as a result of partial gelatinization of starch granules. The extent of the observed effect depended on the botanical origin. Wheat starch exhibited a different behaviour: the consistency coefficient and the conservative modulus being higher for DIC treated starch except for the most severe conditions

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

Solid-state 13 C NMR Study of Scleroglucan Polysaccharide. Effect of the Drying Process and Hydration on Scleroglucan Structure and Dynamics

International audienceHigh-resolution solid-state 13C CP/MAS NMR was used to study the evolution of a polysaccharide (scleroglucan) conformation from the anhydrous to the hydrated form. The influence of a thermo-mechanical treatment applied during the drying process of scleroglucan is analyzed both on the dried and rehydrated product. 13C NMR spectra, 13C relaxation times (T1c) and 1H relaxation times in the rotating frame (T1pH) of scleroglucan dried by using instantaneous controlled pressure drop (Détente Instantanée Controlée®) were analyzed in order to explain the observed differences of rehydration capacity. Although the scleroglucan treated at 6 bar has the same conformational state (triple-helix) as the one treated at 1 bar, it shows two different relaxation times T1c for the C-3 carbon involved in the interglycosidic linkage. The magnetization decay of the hydrated sample exhibits a decrease of two time constants with significant shortening of the spin-lattice relaxation times T1C that accounts for the higher mobility of the chains. High-pressure treatment creates highly rigid and compact domains. Consequently, water molecules cannot readily access the inside of the triple-helix and relax the interchain hydrogen bonds

Effect of instantaneous controlled pressure drop process on the hydration capacity of scleroglucan: optimisation of operating conditions by response surface methodology

International audienceResponse surface methodology was used to evaluate the effect of the processing parameters in the instantaneous controlled pressure drop process (DIC, "Détente Instantanée Contrôlée") on the hydration capacity of scleroglucan. This process involves applying steam pressure of between 1 and 6 bar to scleroglucan for a short period of time and then dropping the pressure instantaneously to a vacuum at 15 mbar. Hydration was determined by measuring the increase in viscosity with rapid stirring. Responses were the initial dissolution rate and the maximum viscometer torque produced during hydration of the dried product. The optimum processing conditions selected for the maximum torque obtained from response surface analysis were as follows: pressure level: 1 bar; moisture content: 0.38 g H2O/g of dry scleroglucan; processing time: 15.5 s. For the initial dissolution the optimum rate was attained at 1 bar for the processing pressure, 0.33 g H2O/g of dry scleroglucan and a processing time of 12 s. Under these conditions, the experimental yields of the maximum torque and the initial dissolution rate were close to the predicted values (0.771 mN m and 0.417 μN m/ s, respectively) calculated from the polynomial response surface model equation. Compared with a sample dried using a standard industrial method, the product treated by instantaneous controlled pressure drop had the same initial dissolution rate but the maximum torque produced (0.758 mN m) was twice that produced by the control sample dried in a rotary vacuum dryer (0.444 mN m). Preliminary measures performed using high resolution solid-state 13C CP/MAS NMR revealed a greater separation of the C-5 from the C-2 line, suggesting that the polysaccharide chain of the sample treated by instantaneous controlled pressure drop undergoes conformational changes. © 2000 Elsevier Science Ltd. All rights reserved

EFFECT OF INSTANTANEOUS CONTROLLED PRESSURE DROP TREATMENT (DIC) ON THE SORPTION ISOTHERMS OF STANDARD MAIZE, WAXY MAIZE, AND POTATO STARCHES

International audienceWe applied The Instantaneous Controlled Pressure Drop process (DIC) for starch heat treatment in order to modify its functional and structural properties. The effect of DIC treatment on the sorption capacity was studied for standard maize (SMS), waxy maize (WMS) and potato (PTS) starches,. The isotherms for native and DIC treated starch were determined at 25°C using a standard gravimetric technique. The isotherm curves obtained have a sigmoidal form; exhibiting behaviour of Type II. The sorption isotherms of DIC treated starches are even below to the sorption isotherms of native starches, and the sorption capacity decreased with increasing processing pressure. The isotherms were analysed according to GAB equation, which distinguish between different physical forms of moisture distribution. The GAB model gave the best fit to the experimental data. W0 values of the mono-layer moisture content for all three starches decreased with an increase of severity of DIC treatment