Esterification and Characterization of Starch From Andean Tubers

Abstract

Starch is isolated from the Andean tubers olluco (Ollucus tuberosus) and oca (Oxalis tuberosa) and modified with octenylsuccinic anhydride (OSA); subsequently, the morphological, molecular, and physicochemical characteristics are evaluated. The isolated starch of olluco and oca results in a powder with a purity of 93.2 and 92.8%, respectively; the amylose content of starch isolated from olluco and oca are 27.1 and 28.2%, respectively. The degree of substitution of OSA starch are 0.015 and 0.016 for olluco and oca, respectively. The peak viscosities of OSA starches ranges from 2.83 to 2.88 Pa · s and are higher than those of native starches. The gelatinization temperature and enthalpy of native starches are higher than those of OSA starches. A B‐type X‐ray diffraction pattern is observed for native and OSA starches, and the crystallinity of OSA starches is less than that of its native counterparts. Fourier transform infrared spectroscopy (FTIR) shows a decrease in the 995/1022 cm−1 ratio in OSA starches but not in native starches, which indicates an alteration of the double helical structure; FTIR shows two new peaks after modification with OSA (1724 and 1572 cm−1). Andean tubers can be used an alternative source for producing chemically modified starch with practical applications.

Effect of the OSA Esterification of Oxalis tuberosa Starch on the Physicochemical, Molecular, and Emulsification Properties

“…Moreover, arrangements of linear amylopectin chains were partially modified in crystalline areas as caused by the incorporation of OSA groups. The results are similar to those obtained by Velásquez‐Barreto, [ 12 ] who reported changes in the crystallinity in pink oca OSA starches, although the reduction in crystallinity was lower than yellow oca OSA starches maybe because the DS was lower too. In general, the reduction in crystallinity in oca OSA starches depends on the DS of the chemically modified starches.…”

“…OSA‐modified banana starches also presented decreased temperatures and enthalpy values after modification with 3% OSA. However, these values were lower than those for OSA‐modified oca starch [ 13 ] and similar to the obtained by OSA‐oca pink obtained by Velásquez‐Barreto et al., [ 12 ] an effect reflecting fine structures of amylopectin in the presence of similar amylose contents and granule sizes.…”

“…Accordingly, higher FV values in OSA‐modified starches were previously related to the increased presence of linear amylose chains. [ 13 ] However, pasting properties of OSA‐oca starch [ 12 ] were higher compared with our results maybe could explain for the difference in DS which was lower in this work. Therefore, the incorporation of OSA groups in starches could affect the structure of amylose and amylopectin and their behavior during the pasting test.…”

“…[ 2–4,12 ] The DS of OSA‐modified oca starch was 0.014, a value that was similar to that of banana starches esterified with 3% OSA [ 13 ] and different to OSA‐oca pink obtained by Velásquez‐Barreto et al. [ 12 ] OSA‐modified starches from non‐conventional sources exhibited similar DS values, indicating similar crystalline arrangements of amylopectin (B‐type) and similar amylose contents (23.0 g per 100 g).…”

“…The estimated mean diameter is in line with values found in a recent reports showing increased mean diameters of OSA‐modified starches of banana and pink oca compared with their native starches after modification with 3% OSA. [ 12,13 ] This slight increase in the size suggests that OSA‐modified granules underwent aggregation process, due maybe to increased hydrophobicity following the addition of OSA groups. [ 8 ]…”