3.2. Structural changes in BRS during ripening
3.2.1. Light microscopy and polarising microscopy
Most starch particles in the Cavendish cultivar were oval in
shape, whereas others were spindly. In contrast, starch granules
in the Pisang Awak cultivar were generally round in shape, while
others were triangular (Figs. 1a and b). In both cultivars, the edges
of the starch particles were completely intact and sharply defined
during the first ripening stage. A subset of starch particles degraded
at subsequent ripening stages; this phenomenon might be
attributed to the enzymatic hydrolysis of banana starches.
Starch particles were observed by polarising microscopy
(Figs. 1c and d). Maltese crosses were evident in these particles under
polarised light, with certain particles exhibiting cross patterns
and other particles displaying X-shaped patterns. The points of
these crosses were located at the top and end of the starch particles.
In the Cavendish cultivar, the Maltese crosses became weak
at ripening stages 4 and 5; in the Pisang Awak cultivar, the crosses
became weak at ripening stage 5. This result revealed that there
were differences in the crystalline structures of RS between the
two cultivars.