Modification by lipophilic substitution of Mexican Oxalis tuberosa starch and its effect on functional and microstructural properties

The aim of this work was to study the influence of chemical modification of Mexican Oxalis tuberosa starch by lipophilic substitution using OSA (2-octenyl-1-succinic anhydride) on its degree of substitution (DS), color, particle size (CILAS), microstructural and functional properties. The modified starches showed a dose-dependent relationship for DS with respect to the used OSA concentration (0.0167 for 2% and 0.0076 for 0.25%), as well as an increase in the % of succinic groups (from 0.983 to 2.126); high substitution efficiency is associated with the amorphous region formed by amylose, where esterification with OSA and some amylopectin branching points is suggested. An improvement in modified starch (MS1-MS5) functional properties was observed with respect to the native starch (NSO) due to the lipophilic substitution with OSA, which is generated on the molecular structure of starch. The whiteness for modified starch (MS1 to MS5) was higher (91.94–89.84%) than to native starch (87.90%). Microstructural characterization by SEM and CILAS showed starches with ovoid shape and increase in roughness (as the DS increased), the ellipse relationship trend to increasing as the DS increased (2.30–3.26), while the Feret diameter showed an inverse relationship (30.64–25.53), due to OSA chemical modifications. Modified starches of Oxalis tuberosa generated an improvement in their physicochemical, microstructural, and functional properties with respect to the native starch. These properties could be used in the food and pharmaceutical industries in gel formation, encapsulation, emulsification, films, and coatings.