Caracterização físico-química e morfológica de amidos do tipo ceroso de genótipos selecionados de mandioca (Manihot esculenta Crantz)

Abstract

Starch is a polysaccharide, consisting of linear chains (amylose) and branched chains (amylopectin). Waxy starch has a high percentage of amylopectin (greater than 95%) in its composition and can be found in nature without the need for chemical modifications and generation of residues; has a great potential of use in the industry as thickening agent, with low retrogradation. Cassava (Manihot esculenta Crantz) is a native tuberous root widely cultivated in tropical regions, as in Latin America, and is widely used as a source of starch. Embrapa has the cassava germplasm bank, to be exploited in the production of starch for industrial use, being of fundamental importance new knowledge related to the characterization of these starches as subsidies in the sustainable production of new ingredients with differentiated technological properties. Thus, from the pre-selection of 803 genotypes of the brazilian cassava germplasm bank, using principal component analysis (PCA) and determination of the best number of groups (NbClust), it was possible to define 17 starches of different genotypes of cassava starch that came closest to the paste properties of the reference cassava waxy starch (7734-7WX and 7745-5WX). After selection of the genotypes of interest, the physicochemical and morphological characterization of these starches was performed, comparing them with waxy maize starches (WX-Maize) and commercial starches by means of the determination of paste properties, electron microscopy scanning, optical microscopy, relative crystallinity, branched chain length distribution of amylopectin, swelling power and solubility index. The analysis of the results allowed the identification of genotypes with characteristics close to the reference waxy samples, such as genotypes BGM0975, BGM0996, BGM1733, BGM1884, BGM0083, BGM1637, BGM0995, because they have low viscosity in the cooling cycle or retrograde viscosity, suggesting the functionality of these starches similar to reference waxy starches, for use in the soups, creams and beverages industry, as thickening agents because they exhibit very low retrogradation. The morphological analysis allowed the identification of granules with rounded shapes and similar diameters, already for waxy maize starches and commercial maize starches, polyhedral formats. For the crystallinity results relative to the analyzed samples, there were no significant difference when compared to the reference samples. In the analysis of branched chain length distribution of amylopectin, genotype BGM0036 obtained results closer to the cassava waxy starch sample. The increase in temperature resulted in increased solubility and increased swelling power, except in BGM1773 which is the largest granule. Therefore, this study aimed at the selection and physical-chemical and morphological characterization of waxy-type starches from genotypes selected from the brazilian cassava germplasm bank.