Structural features of banana starches using HPSEC-MALLS-RI

An analytical method to quantify the amylose content and to characterize the structures of the banana starch molecules is reported. This study consists of two parts: Part 1 describes the individual chains present in the starch granules, as the chain-length distribution, and Part 2 characterizes the molecular structure of the starch components by high performance size exclusion chromatography coupled with multi-angle laser light scattering and refractive index detection (HPSECMALLS- RI). The quantification of amylose using two methods (HPSEC-RI and Concanavalin A) is in agreement with the percentage reported. In addition, the ratio Fr III/Fr. II (Fr. II represents amylopectin long B chains and Fr. III represents amylopectin A and B short chains), shows structural differences among banana starches, with more branching in Morado banana starch and less branching in Macho banana starch. A recognition that amylose has significant branching, and thus is not linear, led to the characterization of two populations of amylose: one that is highly branched and the other, which is essentially linear, as established by the HPSEC-MALLS-RI method. Morado amylose has the highest M_w of the branched starches while Macho amylose has the highest M_w and R_z values consistent with differences in the structures of banana starches.