Influence of intensity ultrasound on rheological properties and bioactive compounds of araticum (Annona crassiflora) juice.

The use of extracts rich in bioactive compounds is becoming increasingly common in the food, cosmetics, and pharmaceutical industries for the production of functional products. Araticum is a potential fruit to be analyzed due to its content of phenolic compounds, carotenoids and vitamins, with antioxidant properties. Therefore, this study aimed to investigate the effect of ultrasound on total phenolic compounds, total carotenoids, ascorbic acid, color, turbidity and rheology in araticum juice. Response surface methodology based on a central composite design was applied. Araticum juice was subjected to sonication at amplitude levels ranging from 20 to 100 % of the total power (400 W) at a constant frequency of 20 kHz for different durations (2 to 10 min). Morphological analysis was conducted to observe microscopic particles, and viscosity and suitability to rheological models (Newtonian, Power Law, and Herschel-Bulkley) were assessed. The ultrasonic probe extraction method was compared to the control juice. According to the responses, using the desirability function, the optimal conditions for extraction were determined to be low power (low amplitude) applied in a short period of time or low power applied in a prolonged time. These conditions allowed an ultrasonic probe to act on releasing bioactive compounds without degrading them. All three rheological models were suitable, with the Power Law model being the most appropriate, exhibiting non-Newtonian pseudoplastic behavior.

Influence of hemicellulose content and cellulose crystal change on cellulose nanofibers properties.

This study aimed to evaluate the properties of cellulose nanofibers (CNFs) with different hemicellulose contents and cellulose II polymorphs. A link was found between these polysaccharides and the properties of CNFs. A decrease in crystallinity (from 69 to 63%) and changes in the crystalline structure of cellulose subjected to an alkaline environment were observed, promoting the partial conversion of cellulose I to cellulose II (from 2 to 42%) and preventing CNFs production at NaOH concentrations higher than 5%. Most treatments showed pseudoplastic fluid behavior, except for the 10% NaOH treatment over 2 h, which showed Newtonian fluid behavior. The quality index of the reference CNFs (TEMPO-oxidized) was the highest (80 ± 3), followed by that of the 5% NaOH-treated (68 ± 3 and 22% energy savings compared to the untreated sample), and the untreated (63 ± 3) samples; and the 10% NaOH treatments had quality indices of 51 ± 3 and 32 ± 1, respectively.

Eco-friendly laccase and cellulase enzymes pretreatment for optimized production of high content lignin-cellulose nanofibrils.

Lignin-cellulose nanofibrils (LCNF) are of attracting an increasing interest due to the benefits of maintaining the lignin in the nanomaterial composition. The production of LCNF requires considerable energy consumption, which has been suppressed employing pretreatment of biomass, in which it highlights those that employ enzymes that have the advantage of being more environmentally friendly. Some negative aspects of the presence of lignin in the fiber to obtain cellulose nanofibrils is that it can hinder the delamination of the cell wall and act as a physical barrier to the action of cellulase enzymes. This study aimed to evaluate the impact of a combined enzymatic pretreatment of laccase and endoglucanase for high content lignin LCNF production. The morphological and chemical properties, visual aspect and stability, crystallinity, mechanical properties, rheology, barrier properties and quality index were used to characterize the LCNF. The laccase loading used was efficient in modifying the lignin to facilitate the action of the endoglucanase on cellulose without causing the removal of this macromolecule. This pretreatment improved the quality of LCNF (61 ± 3 to 71 ± 2 points) with an energy saving of 42% and, therefore, this pretreatment could be suitable for industrial production for a variety of applications.

Study of morphological properties and rheological parameters of cellulose nanofibrils of cocoa shell (Theobroma cacao L.).

Cocoa shell was evaluated as a precursor for cellulose nanofibrils (NFCs) using mechanical defibrillation. Its morphology was analysed using optical microscopy and scanning electron microscopy with field emission. Rheological and mechanical behaviour were evaluated through flow curves with a strain rate ranging from 0 to 300 s-1 at 25 °C and by means of oscillatory frequency sweeps (0.01 Hz-10 Hz) and shear stress (3 Pa). The thermal-mechanical behaviour was determined by a temperature sweep with a heating rate of 3 °C min-1 and a temperature range of 25 °C-100 °C. Micrographs identified the presence of protoxilem with a mean diameter of 23.34 nm. The flow curve showed the characteristic behaviour of a pseudoplastic fluid. The storage module (G') and the loss modulus (G″) were dependent on the frequency applied, indicating that the material exhibits a weak gel characteristic. The viscoelastic characteristics were influenced by temperature. Therefore, cocoa shell is a new alternative in the production of nanocellulose.

Effects of salts and sucrose on the rheological behavior, thermal stability, and molecular structure of the Pereskia aculeata Miller mucilage.

The rheological behavior, thermogravimetric analysis (TGA), and atomic force microscopy (AFM) of the Pereskia aculeata Miller (OPN) mucilage treated with sodium chloride (NaCl), calcium chloride (CaCl2), and sucrose were evaluated. The experimental design was divided in a fractional factorial 25-1 for the screening of factors (OPN, sucrose, NaCl, CaCl2, and pH) and then in a 5 × 3 × 3 full factorial (OPN, sucrose, and NaCl). The model solutions used for the screening of factors presented shear-thinning behavior and the OPN mucilage concentrations were the factors that had significant effect on the apparent viscosity. Sucrose addition increased the thermal stability of the OPN mucilage solutions. OPN mucilage, sucrose, and NaCl were the variables with significant effect on thermogravimetric responses. The samples presented Newtonian behavior in 0-1.25% OPN mucilage concentrations and non-Newtonian behavior adjusted by power-law in 2.50-5.00% OPN mucilage concentrations with predominance of elastic behavior, contributing to the formation of stronger gels. The presence of sucrose in the systems containing OPN mucilage changed their rheological properties and salt additions caused reduction in viscosity. The AFM results provided a better understanding of the mechanism of OPN mucilage interactions in different solutions that justify the changes in viscosities.

Ultrasound-assisted oil-in-water nanoemulsion produced from Pereskia aculeata Miller mucilage.

For the preparation of nanoemulsions, the correct choice of emulsifiers, together with the emulsification methods, directly influences the final product quality. The present study reports the ultrasound-assisted preparation of oil-in-water nanoemulsions produced with mucilage extracted from leaves of Pereskia aculeata Miller (ora-pro-nobis; OPN). The OPN mucilage (%) and soybean oil (%) concentration range, and the process operating parameters, ultrasonic power amplitude (%) and sonication time (min), were optimized based on the mean droplet diameter (d32). The effect of the mucilage and oil concentrations was also investigated by the response variables such as polydispersity, density, turbidity, viscosity, zeta-potential, and interfacial tension. The higher OPN mucilage concentrations (%) with lower amounts of soybean oil (%) favored nanoemulsion formations (116 ≤ d32 ≤ 171 nm) and increased polydispersity, density, and zeta-potential. On increasing OPN mucilage and soybean oil the turbidity of the dispersions increased. All colloidal systems showed Newtonian behavior, and the viscosity in the systems increased due to the greater OPN mucilage concentration in the aqueous phase at a certain oil concentration. In addition, lower values of equilibrium interfacial tension were found with increasing OPN mucilage concentrations. Finally, from the stability test, it can be pointed out that the OPN mucilage concentration should be between 1.0 and 1.5% and the oil concentration should be less than 5%, so that lower d32 values are maintained over time. Therefore, mucilage extracted from OPN and the ultrasound technique can be used in the preparation of nanoemulsions.

Cold extraction method of chia seed mucilage (Salvia hispanica L.): effect on yield and rheological behavior.

Chia seeds (Salvia hispanica L.) when immersed in water, produce a highly viscous solution due to the release of mucilage, high molecular weight complex carbohydrates with wide application in the food industry. Thus, this study involve development of method for extracting mucilage from chia seed based on mechanical process and low temperature. The method involve extraction by cold pressing and drying by freeze-drying, which was compared to the traditional hot extraction method. The chia seed mucilage cultivated in Brazil was extracted successfully using the previously mentioned extraction method. Rheological analysis including thixotropy, flow curve and frequency sweep of mucilage was done. Microstructure was examined by scanning electron microscopy. The optimal process at 27 °C gave yield of 8.46%. The rheograms showed that the apparent viscosity decreased with increase in shear rate and this effect was most notable in the dispersions obtained by cold extraction and with high concentrations. The gum obtained using CE presented higher values for thixotropic behavior. The storage modulus (G') was consistently higher than the loss modulus (G″) and the data indicated formation of 'weak gel' structure of the dispersions. SEM indicated macroscopic fibrous structure of mucilage obtained through cold extraction process, indicating that the macromolecular network formed by fibrous material contained in mucilage maintained its structure in the process of deep freezing and freeze-drying.

Stability and microstructure of freeze-dried guava pulp (Psidium guajava L.) with added sucrose and pectin.

Freeze-dried guava pulp powders, formulated with the addition of sucrose (0-20 g/100 g pulp) and pectin (0-1.0 g/100 g pulp), were obtained, and their stability was evaluated with respect to the water adsorption isotherms, thermal analysis and microstructure. The GAB (Guggenheim-Anderson-de Boer), Peleg and BET (Brunauer-Emmett-Teller) models were used to evaluate the water adsorption. The microstructure was examined using optical microscopy with polarized light and scanning electron microscopy (SEM). The GAB and BET parameters showed that the moisture content of the monolayer (Xm) increases with increasing pectin concentration in the adsorption isotherms. Optical microscopy micrographs showed that the pulp consisting of sucrose showed crystalline structures present in a higher amount and size, and this behavior is enhanced with increasing relative moisture. SEM showed that the increase in sucrose and pectin concentrations produced powders with lower porosity, providing greater stability to the product. The glass transition temperature increased slightly with increasing pectin concentration and decreased with increasing moisture content in the guava pulp powder. The kinetic curves, ratio of the increase of the water content against the storage time, of the guava pulp treated with 20 g sucrose per 100 g pulp and higher pectin concentration (0.5 or 1.0 g pectin per 100 g pulp) showed reduced adsorption and yielded freeze-dried pulps that were more stable.

Using infrared thermography to evaluate the injuries of cold-stored guava.

This study aimed to identify using the infrared (IR) thermography data the injuries of guavas during cooling and storage at different temperatures. Three experiments were performed at three different temperatures with one storage time. The first experiment was done with static air in a refrigerator at 5 °C, the second experiment was conducted in a tunnel with forced air at 10 °C, and the third experiment was conducted in an air conditioned environment at 20 °C. Mechanical injuries caused by the impact of a pendulum were induced on guava surfaces. The surface temperatures were obtained for bruised and sound tissues during cooling and storage using an Infrared (IR) camera. With thermography, it was possible to distinguish the injured tissues of the fruits that were unaffected at temperatures of 5, 10 and 20 °C in first hours of cooling. The results suggest that the storage of guava fruits at 5 °C in static air resulted in cold-induced injury, while storage at 20 °C resulted in an altered activity pattern. The stored guava fruits were analyzed for mass loss, firmness, color, total sugars, total pectin and solubility. The parameters values were lower during the forced-air cooling and storage at 5 and 10 °C. When stored at 20 °C, there was fruit maturation that caused tissue softening, which makes the fruits more susceptible to deterioration and thermographic readings showed opposite trends.

Fortification with iron chelate and substitution of sucrose by sucralose in light uvaia sherbet (Eugenia pyriformis Cambess): physical, chemical and sensory characteristics.

In this work, iron fortified light uvaia sherbet, with low sucrose content, was developed and its physical, chemical and sensory characteristics were evaluated. The central composite rotational design (CCRD), applicable to the response surface methodology, was used to analyze the formulations. In the formulations, in addition of iron fortification (9 to 15 mg/100 g), the sucrose was substituted by micronized sucralose in a proportion of 66-94 %. The responses were analyzed with respect to changes in pH, total solids, ash, carbohydrates, proteins, calories, overrun, nucleation and thawing temperatures, rheological parameters and sensory attributes. Protein contents and acidity were similar in all formulations. There was a reduction of over 25 % in the caloric value. The rheological results showed pseudoplastic behavior and significant viscosity differences among the tested sherbets. In the overrun and thawing behavior results the sucrose concentration had a significant influence as the formulations with substitution by 28 g of sucralose/kg of sucrose showed greater air incorporation. In the flavor attribute there was not significance in relation to the iron fortification. Sherbets prepared with substitution of sucrose by sucralose and fortified with iron showed good acceptability, more stability and more resistant to thawing.

Effects of added sucrose and pectin on the rheological behavior and freezing kinetics of passion fruit pulp Studied by response surface methodology.

The effects of pectin and sucrose addition on the rheological parameters and freezing kinetic of passion fruit pulp were studied. The effect of the air-blast freezing of passion fruit at -20 °C on the rheological parameters before and after freezing was evaluated. The rheological analyses were carried out using a viscometer at 25 °C, and the readings were converted into rheological measurements using the Mitschka method and fitted to the Ostwald-de Waele model. The freezing kinetics was analyzed using a controlled-temperature cold-stage instrument, which was coupled to a microscope integrated with a video capture system. The concentrations of sucrose and pectin were established using a Composite Rotational Design. The pulps combined with the additives exhibited a pseudoplastic behavior, and the values for the index flow (n) and consistency index (k) before and after freezing differed and were dependent on the additive concentrations. The rates of increase for the frozen areas were evaluated in a microfreezer and were significantly influenced by the additive concentrations. These concentrations were those that presented a lower index flow and a higher consistency index. The results are discussed in terms of the solubility and interaction of the pectin added to the fruit pulp with low pH, the presence of sucrose and low temperature.