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.

Modulating in vitro digestibility of Pickering emulsions stabilized by food-grade polysaccharides particles.

An in vitro digestibility protocol was used to elucidate the role of different emulsifying polysaccharides particles on the lipid digestion rate of oil-in-water Pickering emulsions. Emulsions stabilized by cellulose crystals (CCrys), cellulose nanofibers (CNFs), chitosan particles and a conventional emulsifier (Tween 80) were evaluated concerning microstructure, droplet size, zeta potential and free fatty acids released during digestion. After gastric step, the high positive charge of chitosan-stabilized emulsions favored the droplets disaggregation resulting in a mild effect of bridging flocculation by particles sharing and displacement of the size curve distribution toward lower size. After passing through the intestinal condition, these emulsions presented few droplets and chitosan aggregates with a monomodal size distribution and high mean droplet size (D4,3 = 197 ±â€¯8 µm). On the other hand, Tween 80, CCrys and CNFs were able to inhibit lipid digestion and no changes on mean droplet size were observed following intestinal step. CNFs-stabilized emulsion showed the lowest lipid digestion, whereas the strong adherence of the CCrys particles onto the droplet interface became them resistant to displacement by surface-active components (i.e. bile salts and lipase enzyme). On the other hand, a slow lipid hydrolysis could be observed in chitosan-stabilized emulsions promoted by competition between chitosan aggregates and intestinal fluids by the oil droplet interface. Studying the emulsions stabilized using different polysaccharides particles on gastrointestinal conditions we could elucidate important features for their potential application as control systems of lipid digestion rate, as well as, as delivery systems of lipophilic compounds.

Cellulose nanofibers from banana peels as a Pickering emulsifier: High-energy emulsification processes.

Cellulose nanofibers (CNFs) from banana peels was evaluated as promising stabilizer for oil-in-water emulsions. CNFs were treated using ultrasound and high-pressure homogenizer. Changes on the size, crystallinity index and zeta potential of CNFs were associated with the intense effects of cavitation phenomenon and shear forces promoted by mechanical treatments. CNFs-stabilized emulsions were produced under the same process conditions as the particles. Coalescence phenomenon was observed in the emulsions produced using high-pressure homogenizer, whereas droplets flocculation occurred in emulsions processed by ultrasound. In the latter, coalescence stability was associated with effects of cavitation forces acting on the CNFs breakup. Thus, smaller droplets created during the ultrasonication process could be recovered by particles that acted as an effective barrier against droplets coalescence. Our results improved understanding about the relationship between the choice of emulsification process and their effects on the CNFs properties influencing the potential application of CNFs as a food emulsifier.

Nanocomposites based on banana starch reinforced with cellulose nanofibers isolated from banana peels.

Cellulose nanofibers were isolated from banana peel using a combination of chemical and mechanical treatments with different number of passages through the high-pressure homogenizer (0, 3, 5, and 7 passages). New nanocomposites were then prepared from a mixed suspension of banana starch and cellulose nanofibers using the casting method and the effect of the addition of these nanofibers on the properties of the resulting nanocomposites was investigated. The cellulose nanofibers homogeneously dispersed in the starch matrix increased the glass transition temperature, due to the strong intermolecular interactions occurring between the starch and cellulose. The nanocomposites exhibited significantly increased the tensile strength, Young's modulus, water-resistance, opacity, and crystallinity as the number of passages through the homogenizer augmented. However, a more drastic mechanical treatment (seven passages) caused defects in nanofibers, deteriorating the nanocomposite properties. The most suitable mechanical treatment condition for the preparation of cellulose nanofibers and the corresponding nanocomposite was five passages through the high-pressure homogenizer. In general, the cellulose nanofibers improved the features of the starch-based material and are potentially applicable as reinforcing elements in a variety of polymer composites.

Isolation and characterization of cellulose nanofibers from cassava root bagasse and peelings.

This work aimed to obtain and characterize nanofibers from cassava bagasse and peelings, which are waste originating from cassava starch extraction. To isolate the nanofibers, a combination of pre-treatments (alkaline treatment, Q-chelating treatment, bleaching), acid hydrolysis, and a final ultrasonic disintegration step were used. Acidic hydrolysis was conducted at a constant temperature of 60°C; the acid concentration (30, 40, and 50%) and the treatment time (30, 60, and 90min) were varied. The nanofibers were characterized for their morphology, surface charge, crystallinity index (XRD), and functional groups (FTIR). The diameters of the nanofibers ranged from 2.3nm to 5.4nm. The zeta potential values were lower than -47.7mV. As expected, all the products derived from acid hydrolysis displayed high crystallinity index. Finally, FTIR analysis confirmed that the isolation processes effectively removed amorphous materials such as lignin and hemicellulose from the nanofibers.

Achira as a source of biodegradable materials: Isolation and characterization of nanofibers.

In this study, variations in the delignification and bleaching stages, acid hydrolysis and high-pressure homogenization, led to the development of 12 different treatments applied for obtaining nanofibers using fibrous residues arising from the starch extraction process from the achira rhizomes. The treatments were evaluated based on some properties and characteristics of nanofibers such as: morphology and size (by means of transmission electron microscopy), surface charge (by means of zeta potential measurements), crystallinity index (by means of X-ray diffraction analysis) and functional groups (by means of infrared spectroscopy). In general, the nanofibers showed particle diameters between 13.8 and 37.2nm, length between 832.8 and 2223.8nm and high crystallinity index (57.5% and 69.8%) compared with achira fibrous residue (17.3%). The results evidenced that fibrous residue from achira rhizomes can be used as a source of biodegradable materials of commercial interest.

Amaranthus cruentus flour edible films: influence of stearic acid addition, plasticizer concentration, and emulsion stirring speed on water vapor permeability and mechanical properties.

Films forming solutions composed of Amaranth (Amaranthus cruentus) flour (4.0 g/100 mL), stearic acid (5-15 g/100 g of flour), and glycerol (25-35 g/100 g of flour) were prepared by an emulsification process, with varying stirring speed values (6640-13360 rpm). The influence of these parameters (stearic acid and glycerol concentrations and stirring speed) on the water vapor barrier and mechanical properties of films was evaluated using the response surface methodology (RSM). Other characterizations, including microstructure, water solubility, and oxygen permeability, were performed in optimized films. According to statistical analysis results, the optimized conditions corresponded to 10 g of stearic acid/100 g of flour, 26 g of glycerol/100 g of flour, and a stirring speed of 12 000 rpm. The films produced under these conditions exhibited superior mechanical properties (2.5 N puncture force, 2.6 MPa tensile strength, and 148% elongation at break) in comparison to those of other protein and polysaccharide composite films, low solubility (15.2%), and optimal barrier properties (WVP of 8.9 x 10(- 11) g m(- 1) s(- 1) Pa(- 1) and oxygen permeability of 2.36 x 10(- 13) cm3 m(-1) s(-1) Pa(-1)).