The presence of γ-linolenic acid, stearidonic acid, tocopherols, tocotrienols, phospholipids, carotenes, minerals as well as terpenoids and β-sitosterols provides an oil phase with superior nutritional value compared to other plant oils 14, 15, 16, 17, 18, 19. HSO is the extracted oil from the seed of Cannabis sativa L. In this study, hemp seed oil (HSO) was selected as the oil phase to produce oil-in-water (O/W) nanoemulsions. Hence, for reducing process time and energy during ultrasonication based nanoemulsion production, this article focuses on bridging the gap amongst these theories and introducing the concept of existence of very similar optimal ultrasound processing times for samples with different volumes produced by various ultrasonic amplitudes. Besides, based on the laws of Rittinger, Bond and Kick, the reduction of particle size is independent of the sample volume 13. It has also been proved that the particle size decreasesd with ultrasonication time but was insensitive to ultrasonication amplitude 10. Thus, it is not necessary to keep increasing processing time to get the smallest particle size 11. Based on previous study 11, the droplet size first decreases exponentially with increasing ultrasonication time, then tended to be stationary after certain minutes. Even though it is essential to know the particle size once it reaches equilibrium during the ultrasonication process, it is vital to understand the dynamic pathways to reduce the processing time and to avoid the over-supply of energy, which may result in higher particle size than expected 12. This processing leads to microjet and shock-wave impacts and collisions between particles, resulting in particle-size reduction 11. In this method, mechanical vibrations from ultrasound waves (> 20 kHz) create sinusoidal pressure variation in the emulsion system 10. This is often made possible by imposing very high shearing stresses upon the liquid that is to be dispersed, wherein the shearing forces break the material into multiple fine particles.Ī widely used high energy method to reduce the droplet size of nanoemulsions is ultrasonication. A high bioavailability for such emulsion systems can be achieved by ensuring small size of the dispersed droplets. Such emulsions can also be used to develop beverages loaded with lipophilic nutraceuticals, like encapsulated β-carotene, curcumin or insulin 2, 3, 6, lipophilic hormones like insulin 7, or as precursors to preparation of encapsulated microcapsules 8, 9. Using nanoemulsions helps hydrophobic drugs dissolve in the water phase and protects protein compounds through gastrointestinal tract 5. Thanks to their high surface area, long shelf life, transparent appearance and tunable rheology, nanoemulsions have been applied across many fields such as drug delivery and food fortification over the past decades 2, 3, 4. Nanoemulsions (NEs) are translucent or cloudy, thermodynamically unstable, and isotropic liquid mixtures of oil and water, often stabilized by a surfactant or a combination of a surfactant-cosurfactant 1. Based on the results of these case studies, it could be theorized that a constant optimum ultrasonication process time exists for the ultrasonication-based size-reduction processes, dependent only on product parameters. Finally, the existence of this constant optimal ultrasonication process time was proven for another emulsion system (olive oil and tween 80). It was found that the optimal ultrasonication process time (defined as time taken to achieve 99% of the ‘maximum possible size reduction’) was 10 min, and was roughly constant regardless of the process parameters (sample volume and ultrasonic amplitude). Magnitude of particle size reduction decreased with increasing ‘ultrasonication process time’ according to a first order relationship, until a minimum particle size was reached beyond which ultrasonication no longer resulted in detectable decrease in particle size. Next, other process parameters (emulsion volume and ultrasonic amplitude) were tested using kinetic experiments. Results revealed that the particle size and emulsion stability was affected significantly ( p 0.05) affected by process parameter (‘ultrasonication process time’). The system parameters during ultrasonication of a hempseed oil nanoemulsion was evaluated by a response surface methodology, comprising lecithin and poloxamer-188 as surfactants. We test the concept using the case of ‘ultrasonic preparation of oil-in-water nanoemulsions’ as model system. This paper theorizes the existence of a constant optimum ultrasound process time for any size-reduction operation, independent of process parameters, and dependent on product parameters.
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