Modified Corn Starches with Improved Comprehensive Properties for Preparing Thermoplastics

Abstract

A novel method of starch modification was developed to obtain thermoplastic starch plastics with improved comprehensive properties. Corn starch was oxidized under mild conditions using sodium periodate to prepare dialdehyde starch, which had an acceptable average molecular weight. The dialdehyde starch with 35.2% carbonyl content was reacted with different alcohols (methanol, ethanol, and glycol) to prepare a series of novel starch derivatives, whose structures were characterized by 1H‐NMR and FT‐IR. The thermogravimetric analysis showed that these starch derivatives had an improved thermal stability compared with dialdehyde starch. Thermoplastic starch and its derivatives were prepared when water and glycerol were added as plasticizers. The modified thermoplastic starch and its derivatives had better mechanical properties than other modified starches, and lower humidity absorption than conventional thermoplastic starches. The highest tensile strength and elongation at break reached 17.5 MPa and 149%, respectively, and the highest humidity absorption was about 37%.

Starch-protein active films for food preservation

“…Nevertheless, the characteristic absorption peak around 1740 cm -1 , corresponding to carbonyl (C=O) stretching vibration, presented a very weak intensity due to the formation of hemiacetal linkage between oxidised and non-oxidised starch residues (Zhang et al, 2007;Zhang et al, 2014). It is remarkable that the absorption peaks in samples with oxidised starch decreased in intensity at a constant wavenumber, as previously described by other authors (Rivero et al (2010) for crosslinked polymer structures, probably associated with the major restrictions for bond vibration.…”

“…The thermoprocessing of these films implies the application of high temperatures, which could extend the interaction between both DAS and proteins, increasing film browning. In addition, the formation of carbonyl groups decreases the thermal stability of DAS Zhang et al, 2007), limiting its application in thermoprocessing methods.…”

“…On the other hand, the reaction between carbonyls of reducing sugars and protein amino groups led to the formation of Maillard compounds, thus resulting in film browning. The increase in the number of carbonyl groups reduced the thermal stability of DAS Zhang et al, 2007), which can compromise the thermoprocessing of DAS-gelatin blends. Heating DAS-gelatin blends could, hence, extend the reaction between both polymers, resulting in an unsuitable material.…”

Properties of Oxidized Starch Prepared by Hydrogen Peroxide, Chlorine Dioxide and Sodium Hypochlorite

“…The spectra show an intense band at 1637 cm-1, which was assigned to deformation vibrations of water molecules absorbed by starch [12]. The broad band at 1735 cm-1 is characteristic of C=O groups (stretching vibration), produced by oxidation of hydroxyl groups to aldehyde and carboxyl groups [13]. FT-IR spectra of oxidized starch prepared with H2O2 ( Figure 1, Curve (a)) exhibited a higher intensity of this absorption peak than other starches (curve (b, c, d)) correlating with its higher carbonyl content as measured by titration (see Table. 1).…”

“…In previous studies, we found that when the hydroxyl groups in glucose ring of starch were oxidized to aldehyde groups, both the mechanical properties and hydrophobicity of thermoplastic starch were improved [5]. In this study, properties of oxidized starch with carboxyl of same content by Hydrogen Peroxide, Chlorine Dioxide and Sodium Hypochlorite were evaluated, and some properties of them were investigated.…”