Functional, Thermal and Structural Properties of Green Banana Flour (cv. Giant Cavendish) by De-astringency, Enzymatic and Hydrothermal Treatments.

Green banana fruit with high resistant starch (RS) content has a potential to be a nutraceutical ingredient despite having an unpleasant astringency taste and is yet to be fully explored. In this study, the green banana after de-astringency treatment was employed for flour production, and the resulting flour was subjected to modification by the combined treatments of pullulanase debranching and annealing. The banana flour (BF) and the modified flour (MF) were compared with each other by evaluating their functional, thermal and structural properties. The BF showed a restricted-swelling pasting profile, behaving like a slightly chemically cross-linked starch; the MF exhibited less pronounced changes in pasting behavior with increased solubility and decreased swelling power and dispersed volume fraction at elevated temperatures. As compared with the BF, an enhanced thermal stability of the MF was observed, reflected in the endotherm shifting to higher temperatures with increased enthalpy. The BF displayed a C-type polymorph, while the MF comprised a mixture of B- and V-type polymorphs with increased crystallinity. The MF showed an increased molecular order, reflected in an increase in short-range double helical order detected in the starch fingerprint regions of FT-IR spectra, and along with increased crystallinity, underlying its enhanced thermal stability. The modification treatment resulted in irregularly shaped flour particles with a more compact structure as revealed by morphological characters. The results of this study can provide useful information for the development of food products using the modified green banana flour with improved thermal stability and functional properties as a health-promoting ingredient.