Studies on Rye Starch Properties and Modification. Part III: Viscograph Pasting Characteristics of Rye Starches

Effect of Some Hydrocolloids on the Rheological Properties of Rye Starch

The effect of three non-starch hydrocolloids (guar, carob and arabic gums) on some rheological properties of rye starch pastes/gels at a constant 6.5% concentration of polysaccharides was determined throughout: (i) pasting characteristics, (ii) flow curves and apparent viscosity–shear time curves at 50 C and (iii) mechanical spectra at 25 C. The presence of gums in the system modified the rheological properties of rye starch pastes/gels and these alterations depended on the type and concentration of the gum. The systems with guar and carob gums exhibited higher apparent viscosities during pasting and higher shear stresses during flow than the paste of native starch. The viscosity of the system with carob was bigger than the one with guar gum. The presence of arabic gum decreased the apparent viscosity of the system both during pasting and during flow. Replacing part of starch with a gum modified the viscoelastic properties of gels, the changes depended on the kind and concentration of the gum.

The impact of heat-moisture treatment on molecular structures and properties of starches isolated from different botanical sources

Heat-moisture treatment is a hydrothermal treatment that changes the physicochemical properties of starches by facilitating starch chain interactions within the amorphous and crystalline domains and/or by disrupting starch crystallites. The extent of these changes is influenced by starch composition, moisture content and temperature during treatment, and by the organization of amylose and amylopectin chains within native starch granules. During heat-moisture treatment starch granules at low moisture levels [(<35% water (w/w)] are heated at a temperature above the glass transition temperature (T(g)) but below the gelatinization temperature for a fixed period of time. Significant progress in heat-moisture treatment has been made during the last 15 years, as reflected by numerous publications on this subject. Therefore, this review summarizes the current knowledge on the impact of heat-moisture treatment on the composition, granule morphology, crystallinity, X-ray pattern, granular swelling, amylose leaching, pasting properties, gelatinization and retrogradation parameters, and susceptibility towards α-amylase and acid hydrolysis. The application of heat-moisture treatment in the food industry is also reviewed. Recommendations for future research are outlined.