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.

Simplified extraction procedures (avoiding Soxhlet treatment and/or hemicellulose removal) were evaluated to valorize waste biomass from Posidonia oceanica leaves, obtaining cellulosic fractions and nanocrystals, which were subsequently used to produce films from their aqueous suspensions. Cellulose purification significantly improved mechanical and barrier properties of the films obtained from the fractions, while the extracted nanocrystals yielded films with remarkably improved properties, outperforming most benchmark biopolymers. The lipids initially present in the fractions without Soxhlet treatment were not completely digested by the hydrolysis treatment, having a positive impact on the water vapor permeability of the films (up to 63% drop), although negatively impacting oxygen permeability (increased by 20-30-fold).On the contrary, some hemicelluloses present in the less purified fractions, strongly interacting with cellulose, remained in the extracted nanocrystals leading to enhanced mechanical properties (45% higher tensile strength and 2-fold increase in the elongation at break), but lower water barrier (up to 70% higher permeability than the pure cellulose nanocrystals) due to their hydrophilic character. Films produced from the less purified nanocrystals showed the best compromise between mechanical and barrier performance, while offering a great advantage in terms of sustainability and reduced costs.

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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. Preconditioning 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.

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.

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This work shows the characterization of (nano)cellulosic aerogels prepared from Posidonia oceanica waste biomass by means of confocal Raman microscopy (CRM). For this aim, aerogels were prepared by simple freeze-drying of aqueous dispersions of four (nano)cellulosic fractions with different purification degrees, tested at two different concentrations (0.5% and 2%). These were then coated with polylactic acid (PLA) in order to improve their hydrophobicity and subjected to oil sorption-desorption experiments. Both univariate and multivariate analyses, including an approach based on comparing the spectra with those of reference materials and another one based on automatic detection of components, were compared in terms of the quality and the accuracy of the information provided. Univariate analysis only provided accurate information in the simplest systems (native (nano)cellulosic aerogels), while multivariate analyses facilitated the detection of the different components even for the most complex structures. Automatic identification of components was selected as the optimal methodology, although it also underestimated the abundance of the components with the least intense Raman spectra (cellulosic clusters) in the presence of PLA and oil. Comparison with the reference materials resulted in unrealistic images for the most complex systems. Micron-sized regions of concentrated cellulose were detected using CRM, being more abundant in the denser aerogels. Results also confirmed that PLA was preferentially located close to the surface, while oil could penetrate deeper along the matrix. Overall, the results showed the potential of Raman imaging as a novel approach for the characterization of complex biopolymeric aerogels. K E Y W O R D S cellulose, hyperspectral imaging, multivariate analysis, Raman microscopy, renewable 1 | INTRODUCTION Aerogels are extremely light and porous materials with high surface area and low density, which are useful for a wide range of applications due to their high absorption and adsorption capacities. [1-3] Although aerogels have been traditionally made from inorganic materials, [4,5] their application as adsorbent/absorbent structures (pads) in food packaging

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