Effect of kaolin impregnated with calico plant extract on properties of starch films.

Starch film has poor tensile properties and poor water resistance. We aimed to improve these properties by adding kaolin impregnated with calico plant extract (CP-Kaolin). UV-Vis spectrophotometry showed that the calico plant extract (CPE) contained 4867.52 mg/L of total phenolic compounds and betacyanins were the predominant constituents. CP-Kaolin was characterized by Fourier transform infrared spectroscopy (FTIR), zeta potential, scanning electron microscopy (SEM) and x-ray diffraction (XRD) analysis. FTIR analysis showed that betacyanins were adsorbed on kaolin via hydrogen bonding. Zeta potential analysis confirmed the adsorption of betacyanins on kaolin. The intercalation of betacyanins between kaolin platelets was observed by XRD. SEM revealed that CP-Kaolin was well dispersed and embedded within the starch matrix. It was found that the addition of 10 wt% of CP-Kaolin increased the water resistance, tensile strength and thermal stability of starch film. Moreover, starch film containing 10 wt% of CP-Kaolin was sensitive to the change in pH of the fish during storage. Therefore, the addition of CP-Kaolin improved the properties of starch film and starch film composite with CP-Kaolin could be applied as a smart packaging in the food industry.

Film coating based on native starch and cationic starch blend improved postharvest quality of mangoes.

This work focused on the preparation and characterization of films and coatings based on native cassava starch cationic cassava starch and a blend of the two. The films and coatings are intended for application as coating materials for mango fruits. Due to the good miscibility between native cassava starch and cationic cassava starch, the starch blend film was more hydrophobic than films produced from unblended native cassava starch and unblended cationic cassava starch. In addition, after storage for 10 days, the mangoes coated with the starch blend film had lost the least weight and exhibited only slight changes in physical appearance. Therefore, the coating of native and cationic cassava starch blend is a promising alternative coating that presents no hazard to consumer health or the environment.

Mechanical and barrier properties of starch blend films enhanced with kaolin for application in food packaging.

Starch blend films of native cassava starch and medium distarch phosphate cassava starch (crosslinked cassava starch) were prepared by solution casting. The effects of kaolin content on the water resistance and mechanical properties of the starch blend films were investigated. The addition of 10 wt% kaolin to the starch blend film lowered water vapor permeability to 3.51 × 10-5 g m day-1 m-2 Pa-1, water solubility to 31.60% and raised tensile strength to 2.99 MPa. At this loading of kaolin, the structural integrity of the starch blend film was maintained during immersion in water and thermal stability was enhanced. Scanning electron microscopy revealed kaolin to be well dispersed and embedded within the starch matrix. In summary, the starch blend film composite with 10 wt% kaolin had interesting properties as a material to replace non-biodegradable synthetic plastics for packaging, particularly sachets for food products.

Synthesis of photodegradable cassava starch-based double network hydrogel with high mechanical stability for effective removal of methylene blue.

Synthetic hydrogel has been widely used in several applications, but poor mechanical stability and biodegradability limit their applications and raise environmental concerns. Here, a biodegradable hydrogel was developed via simple free-radical polymerization of poly(acrylic acid) (PAA) in the presence of cassava starch (CS) and poly(vinyl alcohol). The hydrogel showed exceptional mechanical and physical properties. The structural morphology changed at higher CS content from a dense fiber-like porous network to larger pores with thicker cell walls. Due to the formation of a double network structure via physical entanglement, the compressive modulus significantly increased from 27 kPa (CS 0 wt%) to 127 kPa (CS 50 wt%). Reducing synthetic content (PAA) to 25 wt% and increasing CS content to 50 wt% did not reduce the removal efficiency of the hydrogel toward methylene blue (MB). The maximum adsorption capacity of the CS50 hydrogel was 417.0 mg/g. Data fitting to theoretical models indicated monolayer adsorption of MB on a homogeneous surface via chemisorption. Removal efficiency was higher than 70% at the 5th cycle of adsorption-desorption. The biodegradability and photodegradability of the hydrogel were improved by grafting with CS. The developed hydrogel represents an alternative biodegradable adsorbent for a sustainable system of wastewater treatment.

Structure-properties relationships in alkaline treated rice husk reinforced thermoplastic cassava starch biocomposites.

The study focuses on structure-properties relationships in thermoplastic cassava starch (TPS) based biocomposites comprising 5-20 wt% of untreated and treated rice husk (RH). Alkaline treatment with 11% w/v NaOH removed the hemicellulose layer of RH as confirmed by Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA), and resulted in a larger population of -OH groups exposing on the fibril surface. Consequently, the filler-matrix interactions between treated RH and TPS were enhanced, although Brunauer-Emmett-Teller (BET) surface area analysis indicated that the surface area of treated RH was not increased. Interestingly, the biocomposites contained 20 wt% treated RH showed substantially improved tensile strength by a factor of 220% compared to the neat TPS. The biocomposite at 15 wt% treated RH showed high water absorption. TPS with all treated RH contents showed high biodegradation rate, while the thermal stability of the TPS/treated RH biocomposites was slightly decreased. These novel composites showed promising properties for applications as absorbents.

Highly water resistant cassava starch/poly(vinyl alcohol) films.

Biodegradable films were prepared based on cassava starch (CS) and poly(vinyl alcohol) (PVA). To increase its tensile strength and flexibility, CS (20-60 wt%) was blended with PVA at various weight ratios (80-40 wt%). Triethylamine (TEA) was added as a homogeneous catalyst to increase intermolecular interaction and induce miscibility between CS and PVA. The crystallinity and hydrophobicity of blend films containing 20 wt% CS were promoted by the elimination of residual acetate groups in PVA. The number of hydrogen bonds in these blend films increased, which led to stronger interaction and more compact molecular packing between CS and PVA chains. The poor water resistance that limits the shelf-life and applications of CS blends was improved. The addition of TEA to blend films containing 20 wt% CS increased water resistance by 80% and tensile strength by as much as 440%. The development of greater structural integrity yielded ecologically sustainable, low-cost, biodegradable films with excellent physical and mechanical properties.