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.

Polysaccharide composition of raw and cooked chayote (Sechium edule Sw.) fruits and tuberous roots

“…6C). Similar results were presented by Hernandez-Uribe, Agama-Acevedo, Gonzalez-Soto, Bello-Perez, and Vargas-Torres (2011), who also described chayote tuber starch as oval and polygonal in shape with sizes between 10 and 25 m. Similar morphology has been found for mango, cassava, sweet potato and ginger starches, with average sizes of their round, truncated and polygonal shapes of ca.15 m (Peroni, Rocha, Franco, 2006;Simão et al, 2008) On the other hand, Jiménez-Hernández, Salazar-Montoya, and Ramos-Ramírez (2007) described chayote tuber granules as having sizes of a larger range of between 7 and 50 m. By comparison, potato starch granules range in size from 10 to 85 m (Jane, Kasemsuwan, Leas, Zobel, & Robyt, 1994).…”

Effect of Cultivar and Ripening Stage on Quality and Microstructure of Frozen Mangoes (Mangifera indicaLinn.)

“…The soluble sugars found in the fruit are glucose and fructose, but in lower amounts than sucrose. [25] An apparent decrease in AIR during fruit ripening was also reported in the Dashehari mango, [26] Zebda and Baladi mango, [9] and the Tommy Atkins and Keitt mangoes. [27] In this study, we also found that the softening of mangoes during ripening ( Table 2) was accompanied by a rapid decrease in AIR.…”

Microstructural and physicochemical properties of heat-moisture treated waxy and normal starches

“…Between the macromolecules and the growth ring structure, another structural level termed the 'blocklet' has been stated since 1937 by Badenhuizen (1937). This concept is strongly supported by the recent atomic force microscopy study performed by several workers (Ayoub et al, 2006;Baker et al, 2001;Gallant et al, 1997;Ridout et al, 2002Ridout et al, , 2003Simão et al, 2008;Sujka and Jamroz, 2009;Szymoń ska and Krok, 2003;Tang et al, 2006). The blocklet is similar in shape (elongated) but differs in size with the plant (20-400 nm), and is believed to be primarily organized by the crystalline and amorphous lamellae from the amylopectin (Gallant et al, 1997;Tang et al, 2006).…”