AVALIAÇÃO DAS PROPRIEDADES TÉRMICAS, REOLÓGICAS E ESTRUTURAIS DO AMIDO DE CASTANHA PORTUGUESA (Castanea sativa, Mill) MODIFICADO POR HIDRÓLISE ÁCIDO-ALCOÓLICA

Abstract

The chestnut (Castanea sativa, Mill) has lots of nutrients, including starch that is the main compound and is chemically composed of amylose and amylopectin. The starch is the main storage substance for plants and the main energetic source for humans, providing from 70 to 80% of the required daily calories. It is present in many botanical sources and can be used in various industrial sectors, being an important ingredient for processed foods. It can be used in natura or modified by chemical ways, physical, biological or combined techniques. The modified starch is an alternative under continuous development in order to overcome the limitation for some industrial applications of native starch such as low resistance and high tendency to retrogradation, which makes the starch like native. The objective of this study was the chestnut starch (Castanea sativa, Mill) extraction and to evaluate the modification with HCl in two concentrations (0,1 mol/L e 0,5 mol/L) diluted in alcoholic-acid solutions. The behavior of native and modified starch granules were analyzed by thermoanalytical techniques (TG-DTA and DSC), rheological (RVA), structural (XDR and SEM), and color. Furthermore, physical-chemical analyzes were performed on chestnut flour, like protein, ash, lipids, total dietary fiber, carbohydrates and moisture. The samples presented three major weight losses in the TG-DTA analysis, and showed only on native starch sample a strong oxidative character event. There was an increase in the gelatinisation enthalpy for modified samples if compared to the native one. On the other hand, the viscosity and impasting temperature decreased, this probable happened due to the structural weakening after the modification. The granules modification was observed in the scanning electron microscopy, but in the analysis by x ray diffraction the intensity of the samples had a low variation due to the treatments. In the physical-chemical analysis the chestnut flour presented a high content of fiber and low lipids content. This work by performing the chestnut starch modification allowed the knowledge of granules and noticed a change according to the performed modifications, becoming favorable for food industrial uses (marron glacé and candies), non-food and also as a raw material for futures studies of modified starches.