Claudia A. Romero-Bastida

Effect of the addition order and amylose content on mechanical, barrier and structural properties of films made with starch and montmorillonite

This study considered the effect of amylose content (30% and 70%), montmorillonite (MMT) fraction (5 and 15%) and preparation method on mechanical and barrier properties of starch/clay nanocomposites prepared by casting. In Method 1, (30% w/w) glycerol was incorporated before starch gelatinization and MMT addition, while in Method 2 after gelatinization and MMT addition. Nanocomposites with higher amount of MMT showed the highest tensile strength and Youngs modulus for both preparation methods. Method 1 favored nanocomposite properties of films with less amylose content, meanwhile Method 2 favored nanocomposites properties with higher amylose content. Water vapor permeability did not decrease significantly in starch films with different amylose content with the two different preparation methods. X-ray diffraction of the starch films indicated intercalated structures. Higher melting temperature (Tm) was found for nanocomposites with Method 2, indicating more ordered structures. Films with 70% amylose content have higher Tm than films with 30% amylose.

Effect of amylose content and nanoclay incorporation order in physicochemical properties of starch/montmorillonite composites

The effects of the amylose content and the preparation sequence in physicochemical properties of starch/montmorillonite (MMT) composites were studied in this work. Native (30%) and high amylose Hylon VII (70%) starches were considered for assessing the effects of amylose content. Glycerol and MMT were used as additives to evaluate the effects of the former as plasticizer and the latter as reinforcer. The glycerol was incorporated before (Method M1) and after (Method M2) the addition of MMT. FTIR studies indicated that water bonding was affected by amylose content. Sorption isotherms indicated that method M2 favoured water adsorption and method M1 reduced water adsorption due to competition for active sites for interaction. TGA showed that method M1 induced a higher degradation rate than method M2. Wettability analysis by contact angle measurements showed that plasticizer promoted the hydrophilicity of the film, whereas MMT promoted a hydrophobic surface for both cases of amylose content.

Rheology of Film‐Forming Solutions Prepared with Modified Banana Starch and Plasticizer

The physical properties of edible films depend to a great extent on those of their components; the biopolymer and the plasticizer, which define its physical changes during heat processing and handling. The aim of this work was to determine the rheological profile of film forming solutions (FFS) composed of native and modified (oxidized) banana starch and the plasticizer glycerol. Samples of FFS, composed by 4%(w/w) of native and oxidized banana starch and glycerol (4%(w/w) were prepared. Two types of rheological tests were undertaken using a strain controlled Rheometer TA Instruments, model AR1000, with a cone and plate system, 60 mm of diameter and angle of 2°: a) isothermal oscillatory (amplitude and frequency) tests at 25 °C, 90 °C and once cooled down, at 25 °C. b) temperature sweeps, run as the samples were heated up from 25 °C to 90 °C and also when cooled down to 25 °C. The isothermal tests showed that all pastes produced, behaved as weak viscoelastic gel‐like materials, with the elastic modulus (G...