Effects of Sucrose Replacement by Polyols on the Dough-Biscuit Transition: Understanding by Model Systems

This study investigated the impacts of the complete substitution of sucrose by maltitol and/or sorbitol on the dough-crumb transition in biscuits. To this end, the phenomena of starch gelatinization/melting were studied at different moisture contents, both in the biscuit dough and model systems, by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and by environmental scanning electron microscopy (ESEM). Observation of doughs in ESEM revealed sorbitol had a structure very different from sucrose and maltitol crystals. After forming the dough pieces, it could be seen that at least some sugar and maltitol crystals were still present while sorbitol flakes were solubilized. At a limiting real water content (~20% dry basis), adding sweeteners to the mixture increased the gelatinization temperature, more markedly for sucrose and maltitol, as well as increasing the enthalpy. These results were confirmed by the model systems analyses. The calorimetric study with mixing batch cells revealed that sorbitol dissolved completely while maltitol and sucrose competed with the flour constituents to capture water. The proportion of water available for the sorption of the starch grain and its gelatinization was therefore different according to the affinity of the sweetener for water, and might influence the degree and temperature of starch gelatinization/melting.

The retrogradation kinetics of starches of different botanical origin in the presence of glucose syrup

The influence of glucose syrup on the retrogradation of cereal starches was investigated. Laboratory isolated starches from wheat (WS) and oats (OS - oat starch and ROS - residual oat starch) were used in this research. ROS was isolated from the flour left after the industrial separation of β-glucans. Gelatinization temperature of oat starches (63.82°C and 64.01°C for OS and ROS, respectively) was higher than for WS (62.26°C), whereas gelatinization enthalpy for oat starches (8.87J/g and 9.09J/g for OS and ROS, respectively) was lower than for WS (9.99J/g). Moreover, retrogradation percentage (%R) was similar for both oat starches (29.76% and 27.72% for OS and ROS, respectively), and was substantially lower than for WS (42.04%). The introduction of glucose syrup into system reduced the extent of the retrogradation. Rate of the process was suppressed for WS and ROS, whereas for OS it was increased. β-Glucan production process had no significant effect on the gelatinization and retrogradation of oat starch.

Phase Transition of Waxy and Normal Wheat Starch Granules during Gelatinization

The phase transition of waxy and normal wheat starches was systematically studied by light microscopy (LM) with a hot-stage, confocal laser scanning microscopy (CLSM) and differential scanning calorimetry (DSC). While being heated in water, waxy wheat starch showed a higher gelatinization enthalpy than that for the normal starch, which was also verified by the changes in birefringence. As confirmed by LM and CLSM, starch granules displayed an increased swelling degree with temperature increasing, and the gelatinization initially occurred at the hilum (botanical center) of the granules and then spread rapidly to the periphery. While the temperature range of birefringence was narrower than that of granule size change, the crystalline structure was melted at lower temperatures than those for the molecular orders. These results indicate that starch gelatinization was a complex process rather than a simple order-to-disorder granule transition.