Characterization of the properties of modified avocado seed starches by heat-moisture treatment, cross-linking and oxidation and their applications in packaging film.

Abstract

In this study, modification of avocado seed starch (via heat-moisture treatment, cross-linking, and oxidation) was carried out, and then films were produced using modified starches. Native and treated starches were examined for physicochemical, digestibility, pasting, structural, thermal, and morphological properties. Native avocado seed starch had high amylose content (33.67 %) and resistant starch content (84.67 %). FT-IR spectra revealed that no new chemical bonds were formed after the modifications, and X-ray diffractograms indicated that the crystal pattern remained unaffected by the modifications. Cross-linking and oxidation increased thermal stability of avocado seed starch. Micrographs of the modified starches showed aggregations in the starch granules. Solubility decreased considerably by heat-moisture and oxidation treatments, and swelling power increased by cross-linking. All modification techniques reduced the amount of rapidly digestible starch. The highest peak viscosity and trough viscosity were observed in cross-linked starch and heat-moisture and cross-linked starches formed stable starch pastes. The modifications also improved the water resistance of the films by reducing the water vapor permeability from 0.86 g·mm/m2·h·kPa to 0.72-0.84 g·mm/m2·h·kPa. Furthermore, films produced with modified starches had better transparency and mechanical strength. As a result of heat-moisture treatment, cross-linking, and oxidation, avocado seed starches with distinct physicochemical properties were obtained, leading to enhanced potential for application in biopolymer film production.