Acetylation and oxidation are chemical modifications which alter the properties of starch. The degree of
modification of acetylated and oxidized starches is dependent on the catalyst and active chlorine concentrations,
respectively.
The objective of this study was to evaluate the effect of acetylation and oxidation
on the structural, morphological, physical–chemical, thermal and pasting properties of barley starch.
Barley starches were acetylated at different catalyst levels (11%, 17%, and 23% of NaOH solution) and oxidized
at different sodium hypochlorite concentrations (1.0%, 1.5%, and 2.0% of active chlorine).
Fouriertransformed
infrared spectroscopy (FTIR), X-ray diffractograms, thermal, morphological, and pasting
properties, swelling power and solubility of starches were evaluated. The degree of substitution (DS)
of the acetylated starches increased with the rise in catalyst concentration. The percentage of carbonyl
(CO) and carboxyl (COOH) groups in oxidized starches also increased with the rise of active chlorine level.
The presence of hydrophobic acetyl groups, carbonyl and carboxyl groups caused a partial disorganization
and depolymerization of starch granules. The structural, morphological and functional changes in
acetylated and oxidized starches varied according to reaction conditions.
Acetylation makes barley starch
more hydrophobic by the insertion of acetyl groups. Also the oxidation promotes low retrogradation and
viscosity. All these characteristics are important for biodegradable film production.