Avaliação das propriedades térmicas e estruturais de amido de semente de nêspera (Eriobotrya japonica Lindl.) modificado fisicamente

Abstract

The loquat seed starch (Eriobotrya japonica Lindl.) was isolated, characterized, and subjected to physical modifications by ultrasound technique (at amplitudes of 40%, 50%, 60%, and 70%). After proximate analysis, the native starch presented a moisture content (5.48%), lipid content (0.19%), protein content (3.56%), dietary fiber content (4.51%), exhibited a fiber content (1.37%), and carbohydrates by difference (84.77%). Three main mass loss events were detected by thermogravimetry (TG/DTG) for all samples. The lowest onset temperature of degradation was observed in native starch, recording 156.40°C, while the highest temperature was 235.18°C for the US40% sample. Changes in the L*, a*, and b* parameters were observed between native and sonicated samples. A decrease in the initial and peak temperatures during the gelatinization process was observed for sonicated samples. Relative crystallinity was lower for starches modified by ultrasound. The native loquat starch showed a reduction in paste temperature as the vibration amplitude for US modification increased. Peak viscosity showed a more pronounced increase up to the 50% treatment, gradually decreasing when it reached the 70% amplitude. The isolated starches were observed using polarized light and scanning electron microscopy which revealed a mixture of irregular, truncated, and spherical granules. The molecular structure of the starch remained unchanged regardless of the treatment method applied, as confirmed by the unchanged functional groups in the FT-IR spectra. However, the intensity of characteristic peaks was affected by the different treatments.