Optimization and characterization of reinforced biodegradable cellulose-based aerogels via polylactic acid/polyhydroxybutyrate coating.

Vine shoots (VS) and waste eucalyptus paperboard (EP) have been used as cellulose sources (in the form of cellulose nanocrystals -CNCs- and cellulosic fibers respectively) for developing cellulose-based aerogels. Two different parameters including cellulose concentration (0.5 % and 2 % w/v) and freezing temperatures (-20 °C and -80 °C) were tested to evaluate differences in the porosity of the aerogels via Brunauer-Emmett-Teller (BET) and thermal conductivity analyses. In addition, a supplementary coating was applied to the raw aerogels by means of dipping the materials in either polylactic acid (PLA) or polyhydroxybutyrate (PHB) solutions (1 % w/v). Their microstructure was observed via SEM and the reinforcing capacity provided by the coating was measured by means of mechanical compressive tests (~10-fold improvement) and water resistance (contact angle >100°). Finally, aerogels' biodegradability was also confirmed according to the standard ISO 20200 thus providing a sustainable and high-performance alternative to conventional materials also following circular economy principles.

Multifunctional cellulosic aerogels from Posidonia oceanica waste biomass with antioxidant properties for meat preservation.

Posidonia oceanica waste biomass has been valorized to develop bioactive multifunctional cellulosic aerogels (HCAG) by simpler and greener protocols. Hydrophobization of cellulosic aerogels was achieved through PLA coating, while bioactivity was imparted by the incorporation of hydrophilic (E2) and hydrophobic extracts (E3) produced from the same biomass. The incorporation of extracts led to denser aerogels, with less porous structures. These aerogels showed outstanding water and oil sorption capacities (1500-1900%), being able to release the adsorbed liquid almost completely after 7 days. Interestingly, all the aerogels showed a positive inhibition effect (23-91%) on the ß-carotene bleaching assay. Moreover, the aerogels loaded with extracts, especially when combining E2 and E3, were able to reduce the oxidation of lipids and oxymyoglobin in red meat after 10 days of storage. This evidences the potential of these multifunctional aerogels as bioactive adsorbing pads to preserve the quality of fresh packaged foods.

Valorisation of vine shoots for the development of cellulose-based biocomposite films with improved performance and bioactivity.

This work reports on the valorization of Tempranillo vine shoots for the development of bio-based packaging materials. Cellulose (F3) and nanocellulose (NANO F3) were produced by the conventional method, while less purified cellulosic fractions (F2A) and nanocrystals (NANO F2A) were extracted by simplified protocols (omitting Soxhlet and alkaline treatments) to reduce production costs and environmental impact and evaluate the potential added functionalities of these less purified materials. Although most of the hemicelluloses in F2A were digested upon acid hydrolysis, a small fraction remained in NANO F2A. On the other hand, the presence of a minor xylan fraction in F3 limited the access of sulphuric acid towards the cellulose microfibrils, hindering hydrolysis and producing heterogeneous fibrillar structures in NANO F3. The obtained materials were used to produce cellulosic films, as well as blends with agar, and their performance properties were evaluated. Overall, NANO F2A films showed the best compromise between performance and sustainability and presented additional antioxidant capacity. The properties of the films could be adjusted by the incorporation of agar, improving their ductility and water permeability.

In-Depth Characterization of Bioactive Extracts from Posidonia oceanica Waste Biomass.

Posidonia oceanica waste biomass has been valorised to produce extracts by means of different methodologies and their bioactive properties have been evaluated. Water-based extracts were produced using ultrasound-assisted and hot water methods and classified according to their ethanol-affinity (E1: ethanol soluble; E2: non-soluble). Moreover, a conventional protocol with organic solvents was applied, yielding E3 extracts. Compositional and structural characterization confirmed that while E1 and E3 extracts were mainly composed of minerals and lipids, respectively, E2 extracts were a mixture of minerals, proteins and carbohydrates. All the extracts showed remarkably high antioxidant capacity, which was not only related to phenolic compounds but also to the presence of proteins and polysaccharides. All E2 and E3 extracts inhibited the growth of several foodborne fungi, while only E3 extracts decreased substantially the infectivity of feline calicivirus and murine norovirus. These results show the potential of P. oceanica waste biomass for the production of bioactive extracts.

High-performance starch biocomposites with celullose from waste biomass: Film properties and retrogradation behaviour.

In this work, the effects of relative humidity (RH) pre-conditioning (53% vs. 85% RH) and incorporation of cellulose fillers (from Posidonia waste biomass) on the properties and retrogradation of melt compounded starch biocomposites were investigated. Pre-conditioning at 85% RH promoted starch gelatinization during processing, leading to more amorphous materials with reduced stiffness but better barrier properties. Furthermore, these films were less stable upon storage due to greater starch retrogradation. Cellulose incorporation improved significantly the mechanical and water barrier performance, especially in the films pre-conditioned at 85% RH due to enhanced filler dispersion. Although incomplete gelatinization of the starch pre-conditioned at 53% RH led to films with bigger cellulose aggregates, their mechanical and water barrier properties were better, outperforming starch-cellulose biocomposites typically reported in the literature. Moreover, the presence of cellulose limited the degree of starch retrogradation upon storage, highlighting the potential of Posidonia biomass as a cheap source of high-performance fillers.

Potential of lignocellulosic fractions from Posidonia oceanica to improve barrier and mechanical properties of bio-based packaging materials.

This work reports on the valorization of residues from Posidonia oceanica leaves for the purpose of obtaining lignocellulosic fractions of interest for the development of bio-based materials for food packaging. The lignocellulosic fractions were characterized, thereby confirming the purification of cellulose and showing increases in crystallinity and thermal stability after the consecutive extraction steps. Subsequently, pure lignocellulosic films were obtained and characterized and the pure cellulose film showed the best properties in terms of mechanical performance and water vapor permeability. Finally, composite starch films containing lignocellulosic fractions were developed by melt compounding and characterized. Although the film containing the pure cellulose additive showed the optimum improvement in terms of mechanical properties (with an increase of 85% in the elastic modulus and 38% in the tensile strength), similar water vapor permeability reduction (~40%) was achieved with the least purified fractions, explained by their effect on starch gelatinization, as evidenced by SAXS/WAXS.