Barrier and mechanical properties of modified starches

Abstract

The study addressed starch-based coatings on paper and fabrics. Coated materials and free starch films containing different amounts of a well-established plasticizer (glycerol) or potential plasticizer (mainly polyols) were tested with respect to water vapour permeance (WVPe), water vapour permeability (WVP), glass transition temperature (T g ), and mechanical strength (tensile tests). Both normal and high-amylose potato starch were used. These starches were modified by (a) oxidation, (b) oxidation and hydroxypropylation or (c) oxidation and hydrophobically modified by reaction with octenyl-or alkenyl-substituted succinic acid anhydride. Free films of hydroxypropylated high-amylose potato starch showed a lower WVP than did the corresponding starches based on regular potato starch. The WVP of the hydrophobically modified regular potato starches was substantially higher than that of films of the corresponding hydroxypropylated starches. The expected hydrophobic effect of the succinic acid anhydrides in terms of a reduced WVP could not be observed. When glycerol was used as a plasticizer, about 30 parts (by wt.) per hundred parts of starch were needed in order to reduce the T g and to cause observable changes in the mechanical properties of the free films.

Effects of film forming and hydrophobic properties of starches on surface sized packaging paper

“…The effect of different plasticizers that coexist in a starch film depends on their relative concentration. 5 Jansson and Järnström 6 showed that WVP was lower for hydroxypropylated starch films plasticized with glycerol than with other plasticizers such as alkyl polyglucoside. Furthermore, they showed that the glass transition temperature (Tg) decreased as the glycerol content in the free films increased, all in accordance to theoretical values of Tg.…”

Biopolymer Coatings for Paper and Paperboard

“…Due to the hydrophilic character of biopolymers, they must generally be combined with hydrophobic materials, such as fatty acids and waxes. Two primary preparation methods exist for lipid based bio-films; emulsion films and bilayer films, the latter being a better barrier for oxygen and water vapour [34][35][36][37][38][39].…”

“…The polysaccharide polymers in particular will be highlighted in this review. Biopolymer films for use as packaging materials based on starch [33][34][35][36][37][38], chitosan [57][58], cellulose derivatives [63,[77][78][79][80][81][82], and hemicelluloses [43][44][45][46] are described in detail in the literature. Bio-based materials have also been used, for example, in composite formulations (e.g., starch/low-density polyethylene (LDPE) blends) [24,25].…”

“…Incorporation of hydrophilic hydroxypropyl groups improves the low-temperature stability (retrogradation), the stability of the dispersion viscosity and the flexibility of the resulting films. Hydroxypropylated starches have found use in both food and non-food applications, and show excellent film-forming properties along with a high adhesive strength and beneficial rheological properties [34]. The linear amylose fraction in starch is able to form continuous, strong and flexible films through hydrogen bonding.…”

New ways to enhance the functionality of paperboard by surface treatment – a review

“…The addition of a plasticizer such as glycerol can improve the mechanical properties, but at high levels, the plasticizer can increase the mobility of amylose chains at a degree which leads to increased crystallinity. 88 The effect of the formation of a close-packed structure with linear amylose on the barrier properties was illustrated by Jansson and Järnström,96 who showed that the water vapour permeability of a high amylose starch fi lm was about 10 times lower than for that of a normal potato starch.…”