title: Mango starch degradation. I. A microscopic view of the granule during ripening.
abstract: The starch content of unripe mango Keitt is around 7% (FW), and it is converted to soluble sugars during the ripening of the detached fruit. Despite the importance of starch-to-soluble sugar metabolism for mango quality, little literature is found on this subject and none concerning the physical aspects of starch degradation. This manuscript presents some changes in the physical aspects of the starch granule during ripening, as analyzed by light microscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). According to the analysis, unripe Keitt-mango-starch being spherical in shape and measuring around 15 microm, has A-type X-ray diffraction pattern with a degree of crystallinity around 21% with slight changes after 8 days of ripening. AFM images of the surface of the granules showed ultra microstructures, which are in agreement with a blocklet-based organization of the granules. The AFM-contrast image of growing layers covering the granule showed fibril-like structures, having 20 nm in diameter, transversally connecting the layer to the granule. The appearance of the partially degraded granules and the pattern of degradation were similar to those observed as a result of amylase activity, suggesting a hydrolytic pathway for the degradation of starch from mango cultivar Keitt. These results provide clues to a better understanding of starch degradation in fruits.
authors.affiliation: Programa de Engenharia Metalurgica e de Materiais, COPPE, Universidade Federal do Rio de Janeiro, CT-F 209, Cidade Universitaria, Ilha do Fundao, Caixa Postal 68.505, 21945-970, Rio de Janeiro, RJ, Brazil.
authors.forename: Renata Antoun
authors.initials: RA
authors.lastname: Simão
authors.forename: Ana Paula Fioravante Bernardes
authors.initials: AP
authors.lastname: Silva
authors.forename: Fernanda Helena Gonçalves
authors.initials: FH
authors.lastname: Peroni
authors.forename: João Roberto Oliveira
authors.initials: JR
authors.lastname: do Nascimento
authors.forename: Ricardo Pereira
authors.initials: RP
authors.lastname: Louro
authors.forename: Franco Maria
authors.initials: FM
authors.lastname: Lajolo
authors.forename: Beatriz Rosana
authors.initials: BR
authors.lastname: Cordenunsi
mesh_terms: D050260:Carbohydrate Metabolism; D018360:Crystallography, X-Ray; D003594:Cytoplasmic Granules / Q000737:chemistry / Q000201:enzymology / Q000648:ultrastructure; D005638:Fruit / Q000737:chemistry* / Q000254:growth & development / Q000648:ultrastructure; D031022:Mangifera / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D013213:Starch / Q000032:analysis / Q000378:metabolism* / Q000648:ultrastructure*; D000516:alpha-Amylases / Q000378:metabolism; D001614:beta-Amylase / Q000378:metabolism
chemical_list: D013213:Starch; D000516:alpha-Amylases; D001614:beta-Amylase