This study investigated the effects of sodium hypochlorite oxidation and a heat-moisture treatment of potato starch on the physicochemical, pasting and textural properties of potato starches in addition to the water vapour permeability (WVP) and mechanical properties of potato starch films produced from these starches. The carbonyl contents, carboxyl contents, swelling power, solubility, pasting properties and gel texture of the native, oxidised and heat-moisture treated (HMT) starches were evaluated. The films made of native, oxidised and HMT starches were characterised by thickness, water solubility, colour, opacity, mechanical properties and WVP. The oxidised and HMT starches had lower viscosity and swelling power compared to the native starch. The films produced from oxidised potato starch had decreased solubility, elongation and WVP values in addition to increased tensile strength compared to the native starch films. The HMT starch increased the tensile strength and WVP of the starch films compared to the native starch.

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). Fourier-transformed 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.

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The high-, medium-, and low-amylose rice starches were isolated by the alkaline method and acetylated by using acetic anhydride for 10, 30, and 90 min of reaction. The degree of substitution (DS), the Fourier-transformed infrared spectroscopy (FTIR), the X-ray diffractograms, the thermal, morphological, and pasting properties, and the swelling power and solubility of native and acetylated starches were evaluated. The DS of the low-amylose rice starch was higher than the DS of the medium- and the high-amylose rice starches. The introduction of acetyl groups was confirmed by FTIR spectroscopy. The acetylation treatment reduced the crystallinity, the viscosity, the swelling power, and the solubility of rice starch; however, there was an increase in the thermal stability of rice starch modified by acetylation.

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The objective of this study was to evaluate the effects of acid and oxidation modifications on sorghum starch, as well as the effect of dual modification of starch on the physical, morphological, mechanical, and barrier properties of biodegradable films. The acid modification was performed with 3% lactic acid and the oxidation was performed with 1.5% active chlorine. For dual modification, the acid modification was performed first, followed by oxidation under the same conditions as above. Both films of the oxidized starches, single and dual, had increased stiffness, providing a higher tensile strength and lower elongation when compared to films based on native and single acid modified starches. However, the dual modification increased the water vapor permeability of the films without changing their solubility. The increase in sorghum starch concentration in the filmogenic solution increased the thickness, water vapor permeability, and elongation of the films.

a b s t r a c tThe objective of this study was to evaluate the effects of oxidation with sodium hypochlorite at different concentrations of active chlorine (0.5, 1.0 and 1.5 g/100 g) on the physicochemical, morphological, pasting, thermal and gel texture properties of potato starch. The native and oxidized starches were used in different concentrations (3.0, 4.0 and 5.0 g starch/100 mL) for the preparation of biodegradable films using glycerol as plasticizer. The films were evaluated for their mechanical properties, color, water solubility and permeability of water vapor. The degree of oxidation potato starches was more intense as there was an increased concentration of active chlorine in the reaction. Films made with oxidized starch with the highest level of active chlorine had lower tensile strength when compared to native starch films. Also, these films had a lower water solubility and water vapor permeability as compared to the native starch films.

The commercial cellulose fibers and cellulose fibers extracted from rice and oat husks were analyzed by chemical composition, morphology, functional groups, crystallinity and thermal properties. The cellulose fibers from rice and oat husks were used to produce hydrogels with poly (vinyl alcohol). The fibers presented different structural, crystallinity, and thermal properties, depending on the cellulose source. The hydrogel from rice cellulose fibers had a network structure with a similar agglomeration sponge, with more homogeneous pores compared to the hydrogel from oat cellulose fibers. The hydrogels prepared from the cellulose extracted from rice and oat husks showed water absorption capacity of 141.6-392.1% and high opacity. The highest water absorption capacity and maximum stress the compression were presented by rice cellulose hydrogel at 25°C. These results show that the use of agro-industrial residues is promising for the biomaterial field, especially in the preparation of hydrogels.