Brazilian green banana: A thermal, structural and rheological investigation of resistant starch from different cultivars

Banana is a fruit largely consumed in the world. Unripe banana contains a great quantity of starch, which is in majority the resistant starch type. This biopolymer has several health benefits, and it can be applied in food products and biofilms. The starch properties can vary according to its botanical origin. The aim of this study was to investigate the green banana starch structure obtained from three fruits of two genotypes of genomic groups of banana: Terra Platano (AAB), Caturra Cavendish (AAA) and Prata AnA (AAB). The samples were studied for resistant starch content using differential scanning calorimetry (DSC), thermogravimetric analysis, viscosity analysis (RVA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical microscopy. By the DSC analysis, it was observed that the gelatinization phenomenon occurred at lower temperatures for Caturra Cavendish (AAA) and Prata AnA (AAB) in comparison with Terra Platano (AAB). Thermogravimetric curves showed three mass losses to Terra Platano (AAB) and four losses for Caturra Cavendish (AAA) and Prata AnA (AAB). By RVA it was observed that the starch from Terra Platano (AAB) showed higher viscosity and retrogradation. The XRD indicated that the Caturra Cavendish (AAA) and Prata AnA (AAB) presented the C-type profile and the Terra Platano (AAB) exhibited profile B-type and significantly higher relative crystallinity. SEM analysis and optical microscopy revealed that the granules have ellipsoidal and flattened shape. Considering the thermal and rheological characteristics presented, the use of banana starch in biofilms production and in food exposed to a cooking process is suggested.