Microencapsulation of flaxseed oil in pea protein-gum arabic complex coacervates delays lipid digestion in liquid yoghurt.

Flaxseed oil coacervates were produced by complex coacervation using soluble pea protein and gum arabic as shell materials, followed by either spray or electrostatic spray drying and their incorporation to yoghurt. Three yoghurt formulations were prepared: yoghurt with spray-dried microcapsules (Y-SD); with electrospray-dried microcapsules (Y-ES); with the encapsulation ingredients added in free form (Y). The standardised semi-dynamicin vitrodigestion method (INFOGEST) was employed to study the food digestion. The structure was analysed by confocal laser scanning microscopy and particle size distribution. Protein and lipid digestion were monitored by cumulated protein/free NH2 release and cumulated free fatty acids release, respectively. Stable microcapsules were observed during gastric digestion, but there was no significant difference in protein release/hydrolysis among samples until 55 min of gastric digestion. Formulation Y showed less protein release after 74 min (40.46 %) due to the free SPP being available and positively charged at pH 2-4, resulting in interactions with other constituents of the yoghurt, which delayed its release/hydrolysis. The total release of protein and free NH2 by the end of intestinal digestions ranged between 46.56-61.15 % and 0.83-1.57 µmol/g protein, respectively. A higher release of free fatty acids from formulation Y occurred at the end of intestinal digestion, implying that coacervates promoted the delayed release of encapsulated oil. In summary, incorporating protein-polysaccharides-based coacervates in yoghurt enabled the delay of the digestion of encapsulated lipids but accelerated the digestion of protein, suggesting a promising approach for various food applications.

Electrostatic spray drying: A new alternative for drying of complex coacervates.

Complex coacervation can be used for controlled delivery of bioactive compounds (i.e., flaxseed oil and quercetin). This study investigated the co-encapsulation of flaxseed oil and quercetin by complex coacervation using soluble pea protein (SPP) and gum arabic (GA) as shell materials, followed by innovative electrostatic spray drying (ES). The dried system was analyzed through encapsulation efficiency (EE) and yield (EY), morphological and physicochemical properties, and stability for 60 days. Small droplet size emulsions were produced by GA (in the first step of complex coacervation) due to its greater emulsifying activity than SPP. Oil EY and EE, moisture, and water activity in dried compositions ranged from 75.7 to 75.6, 76.0-73.4 %, 3.4-4.1 %, and 0.1-0.2, respectively. Spherical microcapsules were created with small and aggregated particle size but stable for 60 days. An amount of 8 % of quercetin remained in the dried coacervates after 60 days, with low hydroperoxide production. In summary, when GA is used as the emulsifier and SPP as the second biopolymer in the coacervation process, suitable coacervates for food applications are obtained, with ES being a novel alternative to obtain coacervates in powder, with improved stability for encapsulated compounds. As a result, this study helps provide a new delivery system option and sheds light on how the characteristics of biopolymers and the drying process affect coacervate formation.

Melt processing of paramylon using a water:ionic liquid mixture as plasticizer.

Paramylon is a linear ß-1,3-glucan produced by the microalgae Euglena Gracilis. Due to its native crystalline structure, involving hexagonally packed triple helices, paramylon is neither water soluble nor thermoplastic. While such properties are generally obtained by chemical modification of paramylon, the present work demonstrates that using ionic liquid/water mixtures as solvents or plasticizers may be an alternative: A mixture of water with cholinium glycinate (40:60) allowed: i) obtaining paramylon solutions at 80 °C, that form reversible ionogels upon cooling at 20 °C, when used as a solvent, and ii) the thermomechanical processing of paramylon below 100 °C by extrusion and hot-press into transparent films, when used as a plasticizer. The thermoplastic paramylon obtained consists of an amorphous matrix, self-reinforced by oriented triple helices packed as nanofibers. This results in a storage modulus ranging from 300 to 450 MPa at 25 °C, depending on the plasticizer content, and in a tensile strain at break of 27 %. For storage times larger than 1 month, a recrystallization of paramylon is observed, with an unidentified crystalline structure different from the native one. Recrystallized samples can be reprocessed into amorphous films by hot pressing.

Seawater ultrafiltration: role of particles on organic rejections and permeate fluxes.

The role of natural compounds of seawater and added particles on mechanisms of membrane fouling and organic matter rejection has been investigated. Ultrafiltration (100 kDa) has been conducted in both dead-end (out/in) and tangential (in/out) modes on polysulfone hollow fibre membranes. The permeate fluxes are approximately three times higher for tangential ultrafiltration than for dead-end ultrafiltration without differences between settled and non-settled seawaters (NS-SWs) (51-55 L h(-1) m(-2) for tangential and 17-22 L h(-1) m(-2) for dead-end ultrafiltration). Adding bentonite or kieselguhr from 0.13 to 1.13 g L(-1) of suspended solids to NS-SW does not act significantly on permeate fluxes of dead-end contrary to tangential ultrafiltration. For the latter, an addition of particles induces a slight drop of permeate fluxes. Original particles of reconstituted seawater could increase the cake porosity, whereas bentonite and kieselguhr, compounds smaller than original particles, could participate in the formation of a compact cake. The total organic carbon removal was equal to approximately 80% whatever the mode of ultrafiltration may be and the suspended solid concentration ranged from 0.13 to 1.13 g L(-1). Dissolved organic carbon (DOC) and colloidal organic carbon rejection rates were greater for tangential ultrafiltration (37-49%) compared with dead-end ultrafiltration (30-44%) at different concentrations of added particles. Bentonite or kieselguhr addition induced a slight decrease of DOC removal. In the case of particles addition, the worst DOC rejection is found for bentonite.