Complexation of octenyl succinic anhydride-esterified corn starch/polyphenol-rich Roselle (Hibiscus sabdariffa L.) extract: Structural and digestibility features

Native and octenyl succinic anhydride (OSA; degree of substitution = 0.0164 ± 0.002)-esterified corn starches were employed for the manufacture of the starch-polyphenol V-type complexes. For this, the aqueous extract of Roselle was used as a rich source of polyphenols. Assembled OSA starch-polyphenol VI-type complexes were obtained, primarily due to hydrogen (H)-bond interactions and hydrophobic CH-π interactions between α-(1 → 4) glycosidic chains of the hydrophobic core of amylose helix, which is made up of aliphatic –CH2 groups, and the phenolic (flavonic) rings of the polyphenol-rich Roselle extract. This reduced the apparent amylose content, confirming amylose as the main macromolecule involved in the formation of starch VI-type complexes. The presence of the Roselle extract apparently increases the starch tendency to retrograde. Therefore, a retrograded starch (RS3) and assembled OSA starch-polyphenol VI-type complex (RS5) mixture could be obtained. This fact allowed the manufacture of starchy materials with resistant starch (RS) contents as high as ∼35% and low digestion rate. These findings are interesting for the development of products of potential application in the dietary management of metabolic syndrome, and leave new research questions to be addressed in the field of starch-polyphenol V-type complexes.