Extraction optimization, biological activities, and application in O/W emulsion of deep eutectic solvents-based phenolic extracts from olive pomace.

This study evaluated the phenolic compound extraction from olive pomace with deep eutectic solvents (DES) prepared with choline chloride ([Ch]Cl) and four (poly-)carboxylic acids. Temperature, water addition in the solvent, and solid-liquid ratio were evaluate in total phenolic content and antioxidant activity of extracts obtained with DES and ethanol, as control. Moreover, the antimicrobial activities of solvents and extracts were evaluated. Oil-in-water emulsion with DES extract was prepared, characterized and its oxidative stability analyzed. The extract with the highest total phenolic content was obtained with [Ch]Cl:malonic acid. Under optimal conditions, DES extracted 9 % more total phenolic content than ethanol. DES extract showed superior antibacterial activity to the ethanolic extract, and its presence in oil-in-water emulsion increased the induction time in 10-fold when compared to the one prepared with water. These results reinforce that DES are a potential solvent for phenolic compound extraction from olive pomace with antibacterial and technological benefits.

Microfluidics-based production of chitosan-gellan nanocomplexes encapsulating caffeine.

Electrostatic complexes produced by interactions between polysaccharides have promising applications in the medical, pharmaceutical and food fields. In this light, for the development of such particles, microfluidics emerges as a promising technique in which processes occur at a strict laminar flow regime, allowing diffusion-dominated transport and particle formation in highly-controlled conditions. As a proof of concept, we compared bulk versus microfluidic (different devices simulating a range of residence times) processes for the production of electrostatic complexes of gellan with either chitosan (molecular weight âˆ¼ 28 kDa) or hydrolyzed chitosan (molecular weight âˆ¼ 3 kDa). Regardless of the process, polysaccharide solutions (pH 4.5) were mixed in pre-defined concentrations (polysaccharide ratios) to form electrostatic complexes that were used to encapsulate caffeine. These complexes were characterized by zeta potential measurements and particle size distribution. Overall, microfluidics produced complexes with improved characteristics such as lower polydispersity index (PDI âˆ¼ 0.1) and mean size (∼200 nm) when compared to the conventional bulk process (PDI âˆ¼ 0.3 and mean size âˆ¼ 400 nm). Moreover, hydrolyzed chitosan (HC) contributed to an even smaller size and PDI value of the complexes. Such outcome is associated with the lower molecular weight and higher solubility of HC when comparing to conventional chitosan, which in turn improves electrostatic complexation. Caffeine could also be encapsulated in all complexes, but the highest encapsulation efficiency was achieved using microfluidics (70%) and with the geometry that provided a longer residence time. Therefore, we were able to demonstrate that microfluidics is clearly an effective strategy for generating electrostatic complexes with improved properties. Ultimately, this technique demonstrated a high potential for the production of vehicles of bioactive compounds.

Modulating properties of polysaccharides nanocomplexes from enzymatic hydrolysis of chitosan.

Synthesis of nanocomplexes is a simple and low-cost technique for the production of encapsulation systems aiming industrial applications, based on the interaction of at least two oppositely charged molecules. Gellan gum (anionic) is a water-soluble biopolymer resistant to stomach pH conditions, therefore an interesting alternative as an encapsulating matrix. Chitosan (cationic) is also widely used due to its biocompatibility and mucoadhesive properties, although its low water solubility is an important step to be overcome for the production of the complexes. To improve this property, many techniques have been employed, but most of them use unsustainable techniques and chemical agents. The enzymatic hydrolysis of chitosan using proteases emerges as an alternative to these drawbacks and, therefore, this study aimed to evaluate the electrostatic nanocomplexation of native (C) or hydrolyzed (HC) chitosan (by porcine pepsin protease) with gellan gum (G). Polysaccharides and nanocomplexes formed with different G:C or G:HC ratio were evaluated by zeta potential measurements, particle size distribution, X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Transmission Electron Microscopy (STEM), intrinsic viscosity and turbidity analyses. Chitosan hydrolysis allowed the formation of a smaller (445.3 nm in pH 4.5) and more soluble structure (3 kDa), which positively influenced the formation of the complexes. The ratios G:HC of 7:3 and 8:2 formed complexes with lower values of zeta potential (13.9 mV and -5.0 mV, respectively), particle size (635.8 nm and 533.6 nm, respectively) and polydispersity (0.28 and 0.23) compared to complexes formed with native chitosan. Overall, our results show that enzymatic hydrolysis of chitosan favored the formation of electrostatic complexes with reduced size and low polydispersity, which can be used as efficient encapsulating matrices for improved targeted delivery and controlled release of bioactive compounds.

Rheological behavior of cellulose nanofibers from cassava peel obtained by combination of chemical and physical processes.

This work aimed to produce and characterize cellulose nanofibers obtained from cassava peel with a combination of pre-treatments with acid hydrolysis or TEMPO-mediated oxidation and ultrasonic disintegration. All nanofibers presented nanometric diameter (5-16 nm) and high negative zeta potential values (around -30 mV). Oscillatory rheology showed a gel-like behavior of the aqueous suspensions of nanofibers (1.0-1.8 % w/w), indicating their use as reinforcement for nanocomposite or as a thickening agent. Additionally aqueous suspensions of nanofibers obtained by acid hydrolysis presented higher gel strength than those produced by TEMPO-mediated oxidation. However, ultrasound application increased even more viscoelastic properties. Flow curves showed that suspensions of nanofibers obtained by acid hydrolysis presented a thixotropy behavior and viscosity profile with three regions. Therefore our results showed that it is possible to tune mechanical properties of cellulose nanofibers choosing and modifying chemical and physical process conditions in order to allow a number of applications.