Starch biocomposites based on cellulose microfibers and nanocrystals extracted from alfa fibers (Stipa tenacissima)

Cellulose-based biopolymers have emerged as one of the most promising components to produce sustainable composites as a potential substitutes to fossil-based materials. Herein, the aim of this study is to investigate the reinforcing effect of cellulose microfibers (CMFs) and cellulose nanocrystals (CNCs), extracted from alfa fibers (Stipa tenacissima), on the properties of starch biopolymer extracted from potato. The as-extracted CMFs (D = 5.94 ± 0.96 μm), CNCs (D = 14.29 ± 2.53 nm) and starch were firstly characterized in terms of their physicochemical properties. Afterwards, CMFs and CNCs were separately dispersed in starch at different concentrations, and their reinforcing effects as well as the chemical, thermal, transparency and mechanical properties of the resulted starch-based films were evaluated. Thus, CMFs and CNCs incorporation into starch resulted in a minor impact on the films thermal stability, while a considerable impact on the transparency property was observed. In terms of mechanical properties, the addition of up to 20 wt% CMFs reduced the film's elongation but drastically increased its stiffness by 300 %. On the other hand, in the case of CNCs, a loading of 10 wt% was found to be the most effective in increasing film stiffness (by 57 %), while increasing the loading up to 20 wt% CNCs enhanced the film's ductility (strain-to-failure) by 52 %. This study showed that introduction of cellulosic fibers having different sizes into starch can produce biocomposite materials with a wide range of properties for food packaging application.