Review of High-Frequency Ultrasounds Emulsification Methods and Oil/Water Interfacial Organization in Absence of any Kind of Stabilizer

Comparative efficacy of chitosan-HPMC-based nanoencapsulation and ultrasonic treatment of thymol-cinnamaldehyde for controlling Rhizopus stolonifer in papaya: In vitro and in vivo studies

This study examines the in vitro antifungal properties and in vivo efficacy of thymol-cinnamaldehyde (TH-CIN) loaded nanocapsules, prepared using chitosan (CH) and hydroxypropyl methylcellulose (H) with varying ultrasonic power (200-600 W), for controlling Rhizopus stolonifer in papaya. Ultrasonic power notably influenced the nanocapsules' antifungal properties, both in vitro and in vivo. Higher ultrasonic power resulted in improved antifungal activity, with NC-CH-400 and NC-CH-H-600 formulations achieving the highest inhibition zones (94.67 % and 93.33 %, respectively) against R. stolonifer in vitro. The Minimum Inhibitory Concentration (MIC) for CH formulations was 6.25 mg/mL, while the Minimum Fungicidal Concentration (MFC) for all formulations was 50 mg/mL. Protein leakage assays demonstrated significant disruption of R. stolonifer cell membranes, with NC-CH-400 and NC-CH-H-600 at MFC reducing intracellular protein concentrations by over 95 %. In vivo tests showed that NC-CH-400 nanocapsule-coated papayas, whether sprayed or dipped, reduced weight loss to 0.54 % and 0.86 %, respectively, and exhibited lower decay severity indices, particularly during storage. Spraying was more effective than dipping in preventing decay. Peel color analysis revealed that coated fruits maintained acceptable ripeness levels over 10 days, indicating delayed maturation. Coated fruits also exhibited better color consistency and were preferred in sensory evaluations for improved taste, aroma, color, and texture, particularly with NC-CH-400 and NC-CH-H-600 coatings.

Microfluidic systems and ultrasonics for emulsion-based biopolymers: A comprehensive review of techniques, challenges, and future directions

Over the past decade, the advancement of microfluidic technology associated with ultrasonics had received a considerate impact across the field, especially in biomedical and polymer synthesis applications. Nevertheless, there are much hindrance remained unsolved, to achieve simple processing, high scalability and high yield biopolymer products that stabilize during the process. In this review, we discuss the underlying physics for both microfluidic and ultrasonic integration in the synthesis of emulsion-based biopolymer and application. The current progress was outlined, focus on its related applications. We also summarized the current strengths and weakness of the microfluidic-ultrasonic integrated technology, aiming to contribute into SDG 12 for responsible consumption and production.

Hydroxide and Hydrophobic Tetrabutylammonium Ions at the Hydrophobe-Water Interface

Water and oil do not mix. This essential statement of the hydrophobic effect explains why oil-in-water (O/W) emulsions are unstable and why energy must be supplied to form such emulsions. Breaking O/W emulsions is an exothermic event. Yet metastable O/W emulsions can be prepared with only water acting as the stabilizer by the adsorption of hydroxide ions formed from the enhanced autolysis of interfacial water. The heat of desorption of the hydroxide ions from the oil-water interface is not directly accessible but is obtained from the difference between the heat of reaction and the sum of the neutralization and interfacial heats when an emulsion is broken by the addition of acid. This experimental value of 28.4 kBT is in good agreement with the theoretical estimate of 16-20 kBT made from the fluctuation/correlation model of the hydrophobic force and the value of 14 kBT obtained recently from surface spectroscopy. Subsequent verification of the force driving ions to hydrophobic surfaces is shown for tetrabutylammonium bromide with a dielectric decrement value of 26 M-1 compared to 20 M-1 for NaOH. The positive cation preferentially adsorbs at the oil-water interface over hydroxide ions in agreement with the predicted model.

An Alternative Hypothesis on Enhanced Deep Supercooling of Water: Nucleator Inhibition via Bicarbonate Adsorption

Supercooling allows for retarding water crystallization toward negative Celsius temperatures. Previous findings of CO2 molecules shifting into bicarbonate species upon freezing, the latter which naturally adsorb on hydrophobic interfaces, are put in perspective here to interpret earlier published data. Since it has been shown that ice nucleation is unlikely on negatively charged surfaces, I propose that bicarbonates adsorb on most solid particles present in water that act as nucleators, thus retarding freezing and enhancing supercooling. This hypothesis can now explain the deep supercooling observed for sealed and boiled water samples and oil-topped water samples, promoting both more bicarbonate generation and adsorption. Such an explanation opens new directions for access to cryopreservation.

Experimental and numerical analysis of the emulsification of oil droplets in water with high frequency focused ultrasound

Focused high frequency ultrasound emulsification provides significant benefits such as enhanced stability, finer droplets, elevated focal pressure, lowered power usage, minimal surfactant usage and improved dispersion. Hence, in this study, the high frequency focused ultrasound emulsification of oil droplets in water was investigated through experiments and numerical modeling. The effect of transducer power (74-400 W), frequency (1.1 and 3.3 MHz), oil viscosity (10.6-512 mPas), interfacial tension (25-250 mN/m) and initial droplet radius (10-750 µm) on the emulsification process was assessed. In addition, the mechanism of droplet break-up was examined. The experiments showed that the acoustic pressure increased from 9.01 MPa to 26.24 MPa as the power was raised from 74 W to 400 W. At 74 W, the Weber number (We) at the surface and focal zone are 0.5 and 939.8, respectively. However, at 400 W, the We at the transducer surface and focal region reached 2.7 and 6451.8, respectively. Thus, bulb-like and weak catastrophic break up dominates the emulsification at 74 W. The catastrophic break up at 400 W is more vigorous because the ultrasound disruptive stress and We are higher. The time for the catastrophic dispersion of a single droplet at We = 939.8 and We = 6451.8 are 1.01 ms and 0.45 ms, respectively. The numerical model gives reasonable prediction of the trend and magnitude of the experimental acoustic pressure data. The surface and focal pressure amplitudes were estimated with errors of ∼ 6.5% and ∼ 10%, respectively. The predicted Reynolds number (Re) between 74 and 400 W were 8442 and 21364, respectively. The acoustic pressure at the focal region were ∼ 26 MPa and ∼ 69 MPa at frequencies of 1.1 MHz and 3.3 MHz, respectively. Moreover, the acoustic velocities were ∼ 16 m/s and ∼ 42 m/s at 1.1 MHz and 3.3 MHz, respectively. Hence, smaller droplets could be attained at higher frequency excitation under intense catastrophic modes. The Ohnesorge number (Oh) increased from 0.062 to 3.12 with the viscosity between 10.6 mPas and 530 mPas. However, the We remained constant at 856.14 for the studied range. Generally, higher critical We is required for the different breakup stages as the viscosity ratio is elevated. Moreover, the We increased from 25.68 to 1284.22 as the droplet radius was elevated from 15 to 750 µm. Larger droplets allow for higher possibility and intensity of breakup due to diminished viscous and interfacial resistance.

Stability of Aqueous Suspensions of COOH-Decorated Carbon Nanotubes to Organic Solvents, Esterification, and Decarboxylation

Carbon nanotubes are among the most widely used nanosystems, and stability of carbon nanotube suspensions is critical for nanotechnology and environmental science. Remaining in aqueous environment alone misses important factors that regulate colloidal stability in the presence of electrolytes. Indeed, introduction of (80-95) vol % organic solvents leads to sharp changes in suspension properties depending on the solvent. For example, the critical coagulation concentrations for a given inorganic or organic coagulating ion can change by 2 orders of magnitude when going from dimethyl sulfoxide to acetonitrile. We establish and explain these trends by Lewis acid-base interactions and show that a strong interaction extending beyond the standard theory of aggregation plays an important role.