Physical and Mechanical Properties of High‐amylose Rice and Pea Starch Films as Affected by Relative Humidity and Plasticizer

Abstract

The tensile properties, water vapor permeability, oxygen permeability at different relative humidities (RH), and water solubility of edible films made of high-amylose rice starch (RS) or pea starch (PS) were measured and compared with the most commonly used edible films. Photomicrography of starch films shows amylopectin-rich gels and amylose-rich granules. The addition of glycerol into starch films made amylose-rich granules swollen and continuously dispersed between amylopectin-rich gels. Tensile strength of RS and PS films decreased when RH increased from 51% to 90%, whereas elongation-at-break (E) of both films increased when RH increased. Water vapor permeabilities of both films were similar, resulting in 130 to 150 g mm/m 2 /d / kPa. Oxygen permeability of RS and PS were very low (< 0.5 cm 3 m/m 2 /d/kPa) below 40% RH, and 1.2 to 1.4 at 45% RH. Water solubility of PS film was 32.0%, which is lower than that of RS film (44.4%). Overall high-amylose rice and pea starch films possess an excellent oxygen barrier property with extremely high stretchability.

Development and Optimisation of Cassava Starch-Zinc-Nanocomposite Film for Potential Application in Food Packaging

“…It can be seen that the thermal decomposition of the films occurred in three main steps, which generally conforms to the three thermal degradation phenomena of most starch-based films reported in literature [29][30][31]. The initial stage of the thermal degradation of the films occurred at temperature less than 100°C.…”

“…Where, N = number of equivalent biomaterials (500 g), a= surface area of the mould mm 2 , e = allowance (assumed 600 mm 2 ) and TSA = total surface area of the mould (mm 2 ).…”

“…Where, P max = maximum load, A c = contact area (nm 2 ), h c = contact depth (nm), H = hardness of the nanocomposite film.…”

“…The addition of nanoparticles to renewable materials like starch and protein results in the formation of nanocomposite materials often transformed into flexible films [1][2][3][4]. The techniques involved in actualising this transformation are well understood, but their application in the food industry is greatly limited due to their poor service performance, especially in prolonging the shelf-life of food [5].…”

Biopolymer films synthesis and characterisation

“…The lipid biofilms are commonly used as coatings to protect food from moisture loss and to increase the gloss. Since lipids have water vapour permeability values, close to those of synthetic plastic films (Pérez-Gago and Rhim, 2014), they are usually combined with other biopolymers (hydrocolloids) as emulsion particles or multi-layer coatings in order to increase water vapour resistance (Mehyar et al, 2004). Hydrophobic substances used for biopolymer film synthesis include natural wax (beeswax, carnauba wax, candelilla wax); petroleum-based waxes (paraffin and polyethylene wax); petroleum, mineral and plant oils; fatty acids and resins (shellac and wood rosin) (Pérez-Gago and Rhim 2014; Rhim and Shellhammer, 2005).…”