Selective detection of starch in banana fruit with Raman spectroscopy.

To develop an analytical method for rapid quantification of starch in agricultural produce, we measured the Raman spectra of ripening banana fruit and compared the obtained data to those of standard starch, sugar, and fiber chemical samples. Standard starches exhibited distinctive Raman bands, which were similar to the spectral features in green banana before ripening. Moreover, these banana-derived Raman bands gradually weakened during 10 d of storage. Standard sugars (glucose, sucrose, and fructose) exhibited Raman bands in both solid and liquid states, whereas standard fibers exhibited broad spectra and no such bands. Although the sugar content increased, no sugar bands were observed in the banana fruit even after ripening. A correlation was found between the Raman bands and starch content obtained by chemical analysis. These results demonstrate that Raman spectroscopy can selectively provide information regarding starch in banana fruit and be applied as an analytical method for rapid starch quantification.