Circular economy approach for various agrowaste-based bioplastic and biocomposite systems with potential applications in the protection of food products and extension of their shelf life.

In order to evaluate the potentiality of novel formulations based on starch to be used as agricultural mulch films, native and oxidized corn starch nanocomposites were prepared by extrusion using natural (Bent) and chitosan-modified bentonite (Bent-CS) fillers. Nanocomposites interaction with water was studied by means of moisture content (MC) determination, water solubility (WS), water vapor permeability (WVP) and contact angle (CA). The light transmission spectra were analyzed in order to determine the transparency and radiometric properties of films. Mechanical properties are also included and related with the cryo-fractured surface morphology observed by scanning electron microscopy (SEM). Finally, the antimicrobial action of developed nanocomposites was investigated against the phytopathogen bacterium Pseudomonas syringae pv. tomato DC3000 (Psy). Results suggest that starch oxidation leads to a reduction in polarity and transparency. The incorporation of nanoclays improved water resistance, but did not produce a significant effect in WVP and mechanical properties and new strategies are required to improve the nanocomposites performance. However, the incorporation of Bent-CS exerted antibacterial activity on nanocomposites, which is an encouraging result.

Highly stretchable biobased and biodegradable agricultural mulch films based on polylactic acid (PLA) and 10, 20, or 30 wt % various nonedible vegetable wastes such as spinach stems (SS), tomato pomace (TP), and cocoa shells (CS) are prepared and characterized in this work. The results demonstrate that appropriate PLA plasticization and vegetable waste addition allow for obtaining films suitable for mulching with tensile strengths in the 10-24 MPa range and elongations at break up to 460%, depending on the kind and amount of vegetable waste incorporated. Additionally, the developed mulches show low water solubility (1-15 wt %) and moisture content (1-3 wt %) with a water vapor permeability of up to 3 × 10^-10 g s^-1 m^-1 Pa^-1, similar to that of Mater-Bi. In addition, the type of vegetable waste added as filler were demonstrated to significantly affect not only the films' mentioned properties but also their biodegradability. For instance, films prepared with 20 wt % SS were demonstrated to improve PLA soil biodegradability, which increased from 0 to 38 wt % for PLA composites after 6 months of a soil burial experiment. Lastly, the developed composites contain different amounts of plant micro- and macronutrients, indicating their potential as fertilizers. The results found in this work represent a sustainable, fully biobased alternative to other mulches already in the market.

The industrial processing of avocados annually generates more than 1.2 million tons of avocado peels (APs) and avocado seeds (ASs) that have great potential in the production of active bioplastics, although they have never been considered for this aim until now. Separately, the APs and ASs, as well as a combination of avocado peels and seeds (APSs), were evaluated here for the first time for the preparation of antioxidant films, with application in food packaging. Films were prepared by casting, after their processing by three different methods: (1) hydrolysis in acid media, (2) hydrolysis followed by plasticization, and (3) hydrolysis and plasticization followed by blending with pectin polymers in different proportions (25 and 50 wt %). The results indicate that the combination of hydrolysis, plasticization, and pectin blending is essential to obtain materials with competitive mechanical properties, optical clarity, excellent oxygen barrier properties, high antioxidant activity, biodegradability, and migration of components in TENAX suitable for food contact applications. In addition, the materials prepared with APSs are advantageous from the point of view of the industrial waste valorization, since the entire avocado wastes are used for the production of bioplastics, avoiding further separation processes for their valorization.

The growing global food demand, coupled with the limitations of traditional pest control methods, has driven the search for innovative and sustainable solutions in agricultural pest management. In this review, we highlight polymeric nanocarriers for their potential to deliver double-stranded RNA (dsRNA) and control pests through the gene-silencing mechanism of RNA interference (RNAi). Polymer-dsRNA systems have shown promise in protecting dsRNA, facilitating cellular uptake, and ensuring precise release. Despite these advances, challenges such as scalability, cost-efficiency, regulatory approval, and public acceptance persist, necessitating further research to overcome these obstacles and fully unlock the potential of RNAi in sustainable agriculture.