Sheet‐extruded films from blends of hydroxypropylated and native corn starches, and their characterization

Abstract

Sheet‐extruded films from the blends of hydroxypropylated normal corn starch (HP) and native normal corn starch (NS) at weight ratios of 100:0, 90:10, 70:30, 50:50, 30:70, and 0:100 were prepared and characterized. Glycerol and water were added as plasticizers at 11 and 27% starch weight, respectively. The highest tensile strength (TS) and longest elongation to break (EB) for dry films were observed at 70:30 HP: NS ratio, which was 25.76 MPa, and 3.97%, respectively. However, TS and EB of this 70:30 blend extruded starch film exhibited low resistance upon wetting for 10s. The film TS and EB were reduced to 13.26 MPa and 3.35%, respectively. Addition of 0.5% (wt/wt starch) succinic acid (SA) as a cross‐linker to 70:30 HP: NS starch blend before film extrusion positively affected both TS and EB of films upon wetting; rather higher TS (16.64 MPa) and EB (4.85%) values were observed, which indicated improvement in water resistance of the films. Sheet‐extruded films from 70:30 HP: NS blends resulted in improved dry strength, and upon cross‐linking with SA, improved wet strength as well. The films had smooth and compact structure, which was explained by esterification/transesterification reactions promoted by SA, and confirmed by Fourier‐transform infrared spectroscopy analysis. Practical Applications Manufacturing packaging films from biological sources, as well as coating materials, would be beneficial to the environment along with wider applications. Biobased packaging materials include both edible coatings and edible films along with primary and secondary packaging materials, and could also have non‐food applications. They are derived from renewable sources and are potentially biodegradable through composting (which is a technique for waste management). Hydroxypropylation of starch results in wider functionality, and sheet‐extrusion can result in more flexible and transparent films. Blends of 70:30 HP: NS resulted in stronger sheet‐extruded films; testing of both dry and wet strengths of films indicated its suitability for both as edible coating (wet application), and other dry coatings/ films. These blend film can be an alternative to synthetic packaging films within their limitations.

Starch Modification with Molecular Transformation, Physicochemical Characteristics, and Industrial Usability: A State-of-the-Art Review

“…They reported that (1) the pasting and peak temperatures decreased with an increase in the hydroxypropyl content, (2) three hydroxypropylated starch samples were characterized by different degrees of swelling, and (3) the hydroxypropylated starch samples were difficult to age and degrade. Hydroxypropylated starch is commonly found in corn [91], amaranth [92], beans [89], rice [93], cassava [94,95], canna [96], etc. Although etherified starches can improve the sensory quality and overall properties of the final product, they are less frequently used in food products because it is difficult to guarantee the safety of etherifying agents added during the modification process.…”

Recent Developments in Starch Modification by Organic Acids: A Review

“…Starch and hydroxypropylated corn starch (70:30) films when crosslinked with different concentrations of SuA (0.38–0.75% w/w) before extrusion showed higher mechanical strength upon wetting and low water vapor permeability. [ 108 ] Field emission scanning electron microscopy showed smoother appearance of SuA acid cross linked films with voids which may due to the interfacial compatibility. FTIR spectra also indicated appearance of peak at 1715 cm –1 in modified films due to esterification and transesterification reactions of SuA acid with starch.…”

Edible and Functionalized Films/Coatings—Performances and Perspectives

“…Sorbitol was used as a plasticizer. In terms of tensile strength, Canna edulis showed higher values, while for In addition, the degree of polymerization varies significantly among sources [78][79][80][81][82][83][84][85][86][87][88][89][90][91][92]. There are some methods for fractionation, separation, and chemical modification to comply with edible films/coatings formulation.…”

“…Total phenolic contents (TPC) (Folin-Ciocalteu reagent) data are expressed in equivalents of mg of gallic acid for 100 g of film (mg GAE/100 g film) [78,[118][119][120]155,156,[215][216][217][218][219][220][221][222][223][224][225][226][227][228].…”