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This work is aimed at evaluating the ability of the microalgae to partially substitute biodegradable materials with improved physicochemical properties. To this end, starch films containing the microalga Nannochloropsis gaditana sp. ( N. gaditana ) have been developed and characterized. Initially, different ultrasound treatments were evaluated for microalgae cell wall disruption. Although surfactant-aided sonication was the most efficient disruption method, the presence of the surfactant hampered continuous film formation. Subsequently, the ability of intact and ultrasound-treated N. gaditana cells to improve barrier properties of starch films was evaluated. Combined small and wide angle X-ray scattering experiments (SAXS/WAXS, respectively) evidenced slight nanostructural and crystallinity changes induced by the presence of N. gaditana cells. Incorporation of intact or ultrasound-treated microalgae into starch led to more hydrophobic films, with enhanced barrier properties for most of the formulations. However, the films containing the microalgae treated with the greatest ultrasound intensity, did not show any barrier improvement due to the plasticization promoted by the cell components (probably lipids) released during the ultrasound treatment, as suggested by SAXS/WAXS and the mechanical properties. [ABSTRACT FROM AUTHOR]

In this work, a Geoffroea decorticans (chañar) extract very rich in polyphenols and with antioxidant and inhibitory activity against pro-inflammatory enzymes, was microencapsulated in a zein matrix using electrospraying to improve its stability and facilitate its handling as food ingredient. The electrosprayed microcapsules were characterized in terms of morphology, encapsulation efficiency, water sorption ability and release properties at different pH and during an in vitro digestion process. The bioactivity of the encapsulated extract in terms of inhibitory activity on enzymes related to the metabolic syndrome were also evaluated and compared to that of the non-encapsulated ingredient. Results showed that microencapsulation did not affect biological activity and effectively protected the bioactive polyphenols during the simulated digestion process. Therefore, this encapsulation structures could be considered a potential ingredient for functional food development. [ABSTRACT FROM AUTHOR]

The ability of phenolic compounds to bind to dietary polysaccharides such as starch and plant cell wall components impacts their nutritional value. Here, we report interactions between potato cells and three different phenolic compounds (+)-catechin, phloridzin and vanillic acid. The binding interactions of the phenolic compounds with intact potato cells, as well as disrupted cells, cooked cells, isolated cell walls and starch granules was explored varying polyphenol concentration, pH and incubation time. Results showed that binding capacity depends on the type of phenolic compound ((+)-catechin > phloridzin > vanillic acid) as well as the type of substrate, to a maximum of ∼50 µmol/g (dry weight). The observed differences (p < 0.05) were ascribed to the amount and accessibility of potential binding sites in both the phenolic compounds and the polysaccharides. Remarkably, polyphenols could penetrate intact cells and bind the starch within them, suggesting their potential as delivery vehicles, whose loading capacity more than doubled after cooking. [ABSTRACT FROM AUTHOR]

Gelatin and chitosan micro-hydrogels containing a potentially bioactive whey protein hydrolysate were developed through spray drying and the impact of microencapsulation on protection during digestion and peptide stability against lactic acid fermentation during yoghurt manufacturing was assessed. The results showed that the protection exerted by the encapsulation structures during milk fermentation was sequence- and matrix-dependent, being chitosan more effective than gelatin in stabilising the peptides. However, only 5 out of the 21 fermentation-susceptible peptides identified could be protected through encapsulation within chitosan (1 of which was also protected by gelatin). Moreover, the encapsulation within chitosan microparticles did not substantially affect the peptide profile of the digested hydrolysate, and therefore, the peptide bioaccessibility was not expected to be compromised. [ABSTRACT FROM AUTHOR]

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Two bioactive compounds, quercetin and ferulic acid, were encapsulated using the electrospinning technique within hybrid amaranth protein isolate (API):pullulan ultrathin fibers. Initially, the composition of the encapsulation structures was optimized, both in terms of matrix components ratio and to maximize the bioactive loading. The morphology and thermal stability of the developed encapsulation structures were evaluated, as well as the encapsulation efficiency and distribution within the fibers of both antioxidant compounds. Moreover, the release characteristics and protection ability of the encapsulation structures during an in-vitro digestion study were investigated. Smooth ultrathin electrospun fibers were obtained in which the antioxidants were homogeneously distributed. Through this methodology, it was possible to incorporate within the API:pullulan fibers up to 10 and 20% (by weight) of quercetin and ferulic acid, respectively, which were released in a sustained manner during in-vitro digestion, keeping to a greater extent their antioxidant capacity in comparison with the non-encapsulated compounds. [ABSTRACT FROM AUTHOR]

The ability of agar with different purification degrees to produce packaging films has been evaluated and the stability of the obtained materials after prolonged storage has been investigated. The less purified agar resulted in films with higher water vapor permeability and lower mechanical performance than pure commercial agar. However, the commercial agar film required the addition of a plasticizer to produce films that could be manipulated. It has also been observed that prolonged storage at 53 % RH results in a change in the semi-crystalline structure of the agar and in water-polysaccharide interactions. As a result, pure agar films undergo a rigidizing effect resulting in unmanageable films after 7 days of storage. The presence of glycerol improved the stability of the films by limiting the structural changes up to 14 days of storage. In contrast, the films from the least purified agar extract, seemed to be less affected by moisture, showing a higher stability during storage. This points to the potential of the less purified extract to be used as an additive to reduce costs and improve the storage stability of pure agar films. [Display omitted] • Agar purity determines the mechanical and water barrier performance. • The semi-crystalline structure of agar undergoes significant changes upon storage. • Water plays a crucial role in the structural re-organization of agar. • The presence of glycerol improves the stability of the films up to 14 days. • Less purified agar can be used as additive to improve stability upon storage. [ABSTRACT FROM AUTHOR]

Seaweed residues from Alaria esculenta , Saccharina latissima and Ascophyllum nodosum after alginate extraction have been valorized to produce cellulose-based fractions with different purification degrees. The residues were mainly composed of carbohydrates (35–57%) and proteins (12–37%), Alaria and Saccharina being richer in cellulose and Ascophyllum richer in fucoidan. The lower cellulose content in the latter made it unsuitable for the extraction of cellulosic fractions. Self-supporting films were obtained from the cellulosic fractions from Saccharina and Alaria residues. While the higher cellulose purity films presented more desirable characteristics in terms of mechanical properties (with elastic moduli of ca. 5–7 GPa and elongation values of ca. 3–5%) and visual appearance, the presence of non-cellulosic components in the films from less purified fractions reduced their water sensitivity and promoted greater water barrier (with water permeability values of ca. 4–6 kg·m/s·m2·Pa). These results point towards the potential of a simple alkaline extraction to generate cellulose-based films from seaweed residuals with the best compromise between functional properties and economical and environmental efficiency. [Display omitted] • Alginate-extracted brown seaweed biomass is rich in carbohydrates and proteins. • Saccharina and Alaria residues are optimum for the extraction of cellulosic fractions. • Ascophyllum residue is richer in bioactive fucoidan-rich fractions. • Self-supporting cellulosic films were obtained from Saccharina and Alaria residues. • Alkaline extraction yields films with the best performance-sustainability compromise. [ABSTRACT FROM AUTHOR]

Agar-based extracts from Gelidium sesquipedale were obtained by applying a conventional hot water treatment and alternative ultrasound- and microwave-assisted methods, with and without the application of an alkaline pre-treatment. The alkaline pre-treatment produced refined extracts with higher purity; however, extraction yields increased from 2–5% to 7–19% by omitting this step. In particular, the ultrasound-assisted extraction allowed reducing 4-fold the extraction time, while keeping constant or even increasing the yield (up to 19% for the 1 h extraction) with respect to the conventional protocol. Interestingly, the presence of proteins and polyphenols conferred the semi-refined extracts a relatively high antioxidant capacity (19–24 μmol TE/g extract). The refined extract produced by the standard protocol formed the strongest hydrogels (>1000 g/cm2). On the other hand, the semi-refined extracts produced by the alternative protocols formed slightly stronger hydrogels (337–438 g/cm2) than the refined counterparts (224–311 g/cm2), due to their greater molecular weights of the former ones. LCA assessment showed lower global warming potential for the semi-refined extracts, especially the ultrasound-assisted extraction, hence highlighting the potential of this method to produce more sustainable agar-based extracts for food-related applications. [Display omitted] • Alkali pre-treatment produced high-purity extracts but very low extraction yields. • Ultrasound-assisted extraction allowed to reduce 4-fold the extraction time. • The semi-refined extract produced by US-assisted extraction had the highest yield. • Semi-refined extracts presented antioxidant capacity. • LCA assessment showed lower global warming potential for the ultrasound method. [ABSTRACT FROM AUTHOR]

In this study the rheological properties of aqueous suspensions of three microalgae species, Nannochloropsis gaditana , Scenedesmus almeriensis and Spirulina platensis , were investigated as a function of solids content, and related to their composition and microstructure. In addition, the impact of ultrasound processing on their structuring ability was also studied. The less rigid character of the Spirulina platensis cell walls (with very low carbohydrate contents) and the presence of extracellular components promoted cell-cell interactions, yielding suspensions which showed a shear thinning behaviour at lower concentrations than Nannochloropsis gaditana and Scenedesmus almeriensis. It is noteworthy that the three species showed different viscoelastic properties at 25 wt.% total solids. Spirulina platensis suspensions showed a more elastic behaviour and lower frequency dependence, characteristic of weak gels, whilst Nannochloropsis gaditana and Scenedesmus almeriensis behaved more like viscous liquids. The ultrasound treatment did not affect the cell wall integrity, but it promoted the release of intracellular components (some of which could have been partially degraded) and disrupted physical interparticle interactions in Nannochloropsis gaditana and Scenedesmus almeriensis. This has an impact on the rheological properties, increasing the viscosity of Nannochloropsis gaditana suspensions, whilst the viscosity of Scenedesmus almeriensis suspensions was reduced. The outcomes of this work give insights into the exploitation of these microalgae species in soft materials for food, pharma and other technological applications. Unlabelled Image • Scenedesmus and Nannochloropsis were richer in carbohydrates than Spirulina. • The presence of extracellular material was especially evident in Spirulina. • Cell wall composition and structure control the behaviour of concentrated suspensions. • Sonication promoted the release of intracellular components and disrupted cell clusters. • Microalgae suspensions with very different rheological properties can be produced. [ABSTRACT FROM AUTHOR]

Hydrogels from commercial carrageenans (κ-C, ι-C, λ↑-C (high viscosity) and λ↓-C (low viscosity)) were prepared with and without the addition of salts (KCl and CaCl 2). FT-IR and 1H NMR characterization evidenced that while the κ-C and ι-C grades were relatively pure carrageenans, the two λ-C grades were λ-, κ-, θ- and μ-carrageenan hybrids. The effect of carrageenan and salt concentration on the hydrogel strength were evaluated through a response surface design and a detailed structural characterization was carried out by small angle X-ray scattering (SAXS) and rheology. The low amount of sulphate substitution in κ-C enabled intramolecular association, giving rise to strong hydrogels, even in the absence of salts. On the other hand, ι-C, λ↑-C and λ↓-C produced much weaker hydrogels and required the addition of salts to induce intramolecular association by ionic cross-linking. SAXS results suggested the formation of similar structures of double helices in κ-C and ι-C with the addition of salts; however, distinct network structures were attained. In the case of κ-C, a Gauss-Lorentz gel model was suitable to describe the hydrogel structure and the addition of K+ promoted the formation of more ordered and densely packed structures. On the other hand, larger but weaker aggregates, with marked periodicity, were observed in ι-C, with Ca2+ inducing the formation of more densely packed networks. The complex composition of the λ-C grades gave rise to more heterogeneous branched network structures, properly described by a correlation length model, where the gelation mechanism was mostly governed by the κ-carrageenan component. Unlabelled Image • SAXS and rheology were used to explain gelation mechanisms of commercial carrageenans. • Hydrogels from commercial carrageenans were produced with and without added salts. • κ-C formed the strongest hydrogels due to strong intermolecular association. • ι-C with added salts formed larger but weaker, ionically cross-linked, aggregates. • The complex composition of the λ-C grades produced heterogeneous branched networks. [ABSTRACT FROM AUTHOR]

Carrageenan emulsion gels containing sunflower oil were prepared using three different commercial carrageenan grades (κ-C, ι-C and λ-C). The effect of the carrageenan and salt content, as well as the oil:water ratio, on the emulsion gel strength was evaluated through a response surface methodology. Moreover, the rheological properties and the micro- and nanostructure from the stronger emulsion gel formulations were investigated and compared to their analogous hydrogel formulations. Interestingly, emulsion gels formed stronger and more thermally stable networks than the hydrogels, being this effect more evident in ι-C and λ-C. The results indicate that this was mainly due to a polysaccharide concentration effect, as no evidence of interactions between the carrageenan and the oil phase was found. Consequently, the rheological behaviour of the emulsion gels was mostly determined by the type of carrageenan. The association of carrageenan molecular chains was favoured in κ-C and λ-C (due to the presence of κ-carrageenan in the latter) and promoted by the addition of KCl. In contrast, a lower degree of chain association, mostly driven by ionic cross-linking, took place in ι-C. These results evidence the relevance of the gelation mechanism on the properties of emulsion gels and provide the basis for the design of these systems for targeted applications within the food industry. Unlabelled Image • Sunflower oil-filled gels have been produced by gelation of carrageenan emulsions. • Emulsion gels formed stronger and more thermally stable networks that their analogous hydrogels. • No evidence of interactions between the carrageenans and the oil phase was found. • Gelation mechanism and rheological properties were determined by the carrageenan type. • Weaker chain association, driven by ionic cross-linking, occurred in ι-carrageenan. [ABSTRACT FROM AUTHOR]

Abstract This work reports on the production and characterization of agar-based extracts from the seaweed Gelidium sesquipedale by means of simple protocols based on hot water and sonication treatments. The combination of sonication with the hot water treatment reduced 4-fold the extraction time without significantly affecting the extraction yield (ca. 10–12%) and the extracts' properties. Apart from agar, the extracts contained proteins, polyphenols and minerals, which conferred them high antioxidant capacity and led to the production of brownish softer gels. The application of an alkali pre-treatment yielded almost pure agars, with higher molecular weights and crystallinities than commercial agar, resulting in stiffer gels. However, the partial digestion of agar by the alkali led to low extraction yields (ca. 2–3%). These results show the efficiency of the combined heat and sonication method to generate cost-effective agar-based extracts with potential applications within the food industry. Graphical abstract Unlabelled Image Highlights • Agar-based extracts from Gelidium sesquipedale were produced by simple protocols. • Combination of heat and sonication decreased extraction time and unaltered yield. • Alkali pre-treatment produced almost pure agars but very low extraction yields. • Unpurified extracts presented antioxidant capacity. • Softer gels with brownish coloration were obtained from the unpurified extracts. [ABSTRACT FROM AUTHOR]