THERMAL ANALYSIS, RHEOLOGY, X-RAY DIFFRACTOMETRY AND ATOMIC FORCE MICROSCOPY IN THE EVALUATION OF BINARY MIXTURES OF “STARCH-HYDROCOLLOIDS”

Abstract

Starch is arguably the most investigated biopolymer in the world and the cassava starch that is extracted from Manihot esculenta Crantz, represents an important vegetal crop in tropical countries, where its roots and derivatives serve as food and a source of energy. The main composition of these roots is 70-80% water, 16-24% starch and small quantities (<4%) of protein, lipids vitamins and minerals. Hydrocolloids, or gums, are substances consisting of a hydrophilic long-chain with colloidal properties that, in water-based systems, produce gels. Starches and hydrocolloids are often used together in food systems to provide texture, water mobility, control moisture, improve product quality and stability, facilitate processing and reduce costs. In this study, the interactions between cassava and starch-hydrocolloids (1% of the following gums: CMC, jatahy, pectin and xanthan) were investigated. The TG/DTG method made it possible to determine the thermal decomposition of each sample, which under air atmosphere occurs in three steps. Little difference was observed in the degree of relative crystallinity (XRD) and in the average roughness or average diameter of the starch granules (NC-AFM). The viscosity and pasting properties (RVA) increased, and were higher for starch treated with jatahy gum. A large decrease was observed in peak temperature and gelatinisation enthalpy for the treated samples (DSC).