Fructooligosaccharides (FOS) are considered functional compounds of the food due to their effects at reducing risk of many diseases. The aim of this work was to characterize and to quantify, during the ripening, the FOS of different banana cultivars from the most common genomic groups cultivated on Brazil.
The samples were monitored in relation to ethylene and CO2 production during the ripening. Sugar contents were analyzed by HPAEC-PAD (High Performance Anion Exchange Chromatography-Pulsed Amperometric Detection) and GC-MS (Gas Chromatography/Mass Spectrometry).
The onset of FOS synthesis was related to changes of some biochemical events that take place soon after the endogen ethylene evolution, like the increase of the respiration rates and the onset of sucrose and 1-kestose synthesis.
The results indicated significant differences among five of eight banana cultivars investigated, and did not present a direct correlation between FOS levels and genomic group, neither with FOS and sucrose quantity. The 1-kestose was found in all bananas analyzed, but the nystose was confirmed only in banana cv. Prata. A considerable difference was observed of the 1-kestose levels among banana cultivars. For instance, in Mysore cultivar the 1-kestose level was 1292 mg/g of Dry Mass (D.M), while in Terra cultivar was 297 mg/g D.M.. However, the nystose had to be quantified by GC-MS, because its levels (105 mg/g D.M on average) were below of the detection limit of the pulsed amperometric detector, which is 20 ppm (aprox. 200mg/g). The mass spectra of 1-kestose and nystose showed the same abundant and characteristic fragmentation ions at m/z 217 and 361, but the relation between them was different for each one, being 1.2 to 1-kestose and 1.8 to nystose.
The GC-MS presented a higher sensitivity than HPAEC-PAD and, besides, it allowed an accurate identification of the FOS, in spite of the high reproducibility presented by HPAEC-PAD.
It was conclued that the FOS determination by GC-MS was very interesting to analyse food with low fructans level, and the FOS synthesis seems to be an event independent of well-known parameters of banana ripening.
Supported by FAPESP and CAPES