The research of starch as a matrix material for manufacturing biodegradable films has been gaining popularity in recent years, indicating its potential and possible limitations. To compete with conventional petroleum-based plastics, an enhancement of their low resistance to water and limited mechanical properties is essential. This review aims to discuss the various types of nanofillers and additives that have been used in plasticized starch films including nanoclays (montmorillonite, halloysite, kaolinite, etc.), poly-saccharide nanofillers (cellulose, starch, chitin, and chitosan nanomaterials), metal oxides (titanium dioxide, zinc oxide, zirconium oxide, etc.), and essential oils (carvacrol, eugenol, cinnamic acid). These reinforcements are frequently used to enhance several physical characteristics including mechanical properties, thermal stability, moisture resistance, oxygen barrier capabilities, and biodegradation rate, providing antimicrobial and antioxidant properties. This paper will provide an overview of the development of starch-based nanocomposite films and coatings applied in food packaging systems through the application of reinforcements and additives.

Nowadays, plastic contamination worldwide is a concerning reality that can be addressed with appropriate society education as well as looking for innovative polymeric alternatives based on the reuse of waste and recycling with a circular economy point of view, thus taking into consideration that a future world without plastic is quite impossible to conceive. In this regard, in this review, we focus on sustainable polymeric materials, biodegradable and bio-based polymers, additives, and micro/nanoparticles to be used to obtain new environmentally friendly polymeric-based materials. Although biodegradable polymers possess poorer overall properties than traditional ones, they have gained a huge interest in many industrial sectors due to their inherent biodegradability in natural environments. Therefore, several strategies have been proposed to improve their properties and extend their industrial applications. Blending strategies, as well as the development of composites and nanocomposites, have shown promising perspectives for improving their performances, emphasizing biopolymeric blend formulations and bio-based micro and nanoparticles to produce fully sustainable polymeric-based materials. The Review also summarizes recent developments in polymeric blends, composites, and nanocomposite plasticization, with a particular focus on naturally derived plasticizers and their chemical modifications to increase their compatibility with the polymeric matrices. The current state of the art of the most important bio-based and biodegradable polymers is also reviewed, mainly focusing on their synthesis and processing methods scalable to the industrial sector, such as melt and solution blending approaches like melt-extrusion, injection molding, film forming as well as solution electrospinning, among others, without neglecting their degradation processes.

Biopolymers derived from biomass can provide the advantages of both biodegradability and functional qualities from a circular economy point of view, where waste is transformed into raw material. In particular, avocado seeds can be considered an interesting residue for biobased packaging applications due to their high starch content. In this work, avocado seed starch (ASS)-based films containing different glycerol concentrations were prepared by solvent casting. Films were also reinforced with starch nanocrystals (SNCs) obtained through the acid hydrolysis of ASS. The characterization of the extracted starch and starch nanocrystals by scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis has been reported. Adding 1% of SNCs increased elastic modulus by 112% and decreased water vapor permeability by 30% with respect to neat matrix. Interestingly, the bioactive compounds from the avocado seed provided the films with high antioxidant capacity. Moreover, considering the long time required for traditional plastic packaging to degrade, all of the ASS-based films disintegrated within 48 h under lab-scale composting conditions. The results of this work support the valorization of food waste byproducts and the development of reinforced biodegradable materials for potential use as active food packaging.

This work aims to develop bio-based and biodegradable materials for active food packaging purposes by comparing the properties of avocado seed flour (ASF) and avocado extracted starch (AES). A 36.4% dry basis yield is obtained for the extracted AES from ASF. ASF presents a higher crystallinity, and SEM images show a mixture of starch granules and other materials, whereas AES presents lower ash, protein, and lipid content relative to ASF. To make a comparison between the two, ASF or AES are mixed with glycerol at different concentrations, then twin-screw extruded and injection-molded to develop thermoplastic starch-based materials. The morphological, mechanical, barrier, antioxidant, antimicrobial, and disintegrability properties are evaluated to compare their different compositions. ASF-based films exhibit better barrier properties and a 134% higher intrinsic antioxidant capacity. Conversely, the homogenous nature of AES-based materials results in better interactions with the plasticizer, allowing a wide range of mechanical properties. Moreover, cinnamon essential oil (CEO) was incorporated into the preferred compositions of both ASF and AES to improve antimicrobial properties. Adding a 5% concentration of CEO to samples was sufficient to completely inhibit the growth of P. expansum. These results support waste valorization for developing active packaging materials with high antioxidant and antimicrobial properties without competing for resources with the food industry.

This study aims to develop a modified starch with menthol (M) or sulfobetaine (S) using 1,6-hexamethyl diisocyanate (HMDI) as a linker to create biodegradable antibacterial materials for active packaging applications. The modification of potato starch is performed in a two-step reaction. First, the starch modifiers are synthesized through an equimolar reaction between HMDI and menthol or the sulfobetaine precursor. Next, the synthesized HMDI derivative is dissolved in a bio-based solvent (methyl-THF) with starch and K₂CO₃ (1:1 weight ratio) to chemically modify the starch. The chemical and thermal properties of the modified starch are analyzed. Starch films containing 25 wt.% glycerol and low amounts (0.5, 1, and 3% wt.) of M- or S-modified starch were successfully produced by extrusion. Although most film properties remain similar to the control, adding 3% of S-modified starch resulted in a 149% increase in Elastic Modulus and a 29% decrease in water vapor permeability. Additionally, just 0.5 wt.% of either M- or S-modified starch effectively inhibits S. aureus growth, indicating its potential as a bioactive compound for active packaging.