Effect of Sand-Frying-Triggered Puffing on the Multi-Scale Structure and Physicochemical Properties of Cassava Starch in Dry Gel

This study revealed the underlying mechanisms involved in the puffing process of dried cassava starch gel by exploring the development of the puffed structure of gel upon sand-frying, chiefly focused on the changes in the multi-scale structure and the physicochemical properties of starch. The results suggested that the sand-frying-induced puffing proceeded very fast, completed in about twenty seconds, which could be described as a two-phase pattern including the warming up (0~6 s) and puffing (7~18 s) stages. In the first stage, no significant changes occurred to the structure or appearance of the starch gel. In the second stage, the cells in the gel network structure were expanded until burst, which brought about a decrease in moisture content, bulk density, and hardness, as well as the increase in porosity and crispness when the surface temperature of gel reached glass transition temperature of 125.28 °C. Upon sand-frying puffing, the crystalline melting and molecular degradation of starch happened simultaneously, of which the latter mainly occurred in the first stage. Along with the increase of puffing time, the thermal stability, peak viscosity, and final viscosity of starch gradually decreased, while the water solubility index increased. Knowing the underlying mechanisms of this process might help manufacturers produce a better quality of starch-based puffed products.

Graphene oxide and starch gel as a hybrid binder for environmentally friendly high-performance supercapacitors

Alternative green binders processable in water are being investigated for the development of more efficient and sustainable supercapacitors. However, their electrochemical performances have fallen within or below the average of commercially available devices. Herein, an optimised gelled mixture of graphene oxide (GO) and starch, a biopolymer belonging to the family of polysaccharides, is proposed. The molecular interactions between the two components enhance electrodes structure and morphology, as well as their thermal stability. GO, thanks to its reduction that is initially triggered by reactions with starch and further progressed by thermal treatment, actively contributes to the charge storage process of the supercapacitors. The optimised electrodes can deliver a specific capacitance up to 173.8 F g−1 while providing good rate capabilities and long-term stability over 17,000 cycles. These are among the best electrochemical performances achieved by environmentally friendly supercapacitors using a biomaterial as a binder.

Effect of Thermal Pretreatments on Phosphorylation of Corypha umbraculifera L. Stem Pith Starch: A Comparative Study Using Dry-Heat, Heat-Moisture and Autoclave Treatments

Talipot starch, a non-conventional starch source with a high yield (76%) from the stem pith of talipot palm (Corypha umbraculifera L.) was subjected to three different thermal treatments (dry-heat, heat-moisture and autoclave treatments) prior to phosphorylation. Upon dual modification of starch with thermal treatments and phosphorylation, the phosphorous content and degree of crosslinking significantly increased (p ≤ 0.05) and was confirmed by the increased peak intensity of P=O and P–O–C stretching vibrations compared to phosphorylated talipot starch in the FT-IR spectrum. The highest degree of crosslinking (0.00418) was observed in the autoclave pretreated phosphorylated talipot starch sample. Thermal pretreatment remarkably changed the granule morphology by creating fissures and grooves. The amylose content and relative crystallinity of all phosphorylated talipot starches significantly decreased (p ≤ 0.05) due to crosslinking by the formation of phosphodiester bonds, reducing the swelling power of dual-modified starches. Among all modified starches, dry-heat pretreated phosphorylated starch gel showed an improved light transmittance value of 28.4%, indicating reduced retrogradation tendency. Pasting and rheological properties represented that the thermal pretreated phosphorylated starch formed stronger gels that improved thermal and shear resistance. Autoclave treatment before phosphorylation of talipot starch showed the highest resistant starch content of 48.08%.

Effects of Citrus Peel Hydrolysates on Retrogradation of Wheat Starch

Retrogradation is the principal cause for bread staling and, therefore, it has attracted a lot of interest from the food industry. In this study, the inhibitory effect of citrus peel hydrolysates (CPH) on retrogradation of wheat starch (WS) in the presence of sucrose was investigated. The pasting properties showed that further addition of CPH caused a lower setback value than the addition of sucrose alone. Hardness of the gel, retrograded at 4 °C for five days, showed a similar tendency, which was reduced more in CPH addition than WS itself or sucrose addition alone. The low retrogradation enthalpy of the CPH including starch gel also indicated the positive effect of CPH on retarding retrogradation. These results suggested that incorporation of CPH in starch-based foods would be effective for inhibiting retrogradation, preventing the deterioration of the quality of food products.