Ultrasound assisted extraction (UAE) is the process of passing waves of ultrasonic energy through a liquid suspension containing solid particles. A force parallel or perpendicular to the material's surface is produced as the waves collide with it.[1]

Shock waves with a pressure equivalent to several thousand atmospheres are produced when sonic energy is transformed into mechanical energy. This abrupt, localized rise in temperature and pressure causes the cellular membranes to fission which makes it easier for the solvent to enter the cell and extract the desired component. Some industries use UAE to extract bioactive ingredients from botanicals, including vitamins, polyphenols, polysaccharides, cannabinoids, and other phytochemicals.[2] Superior extract yields are obtained quickly due to the total extraction achieved by sonication.

An ultrasonic bath or an ultrasonic probe system is used for extraction. For instance, this technique was suggested to remove isoflavones from soybeans and phenolic compounds from wheat bran and coconut shell powder.[3] The outcomes differ for every raw material and solvent utilized, in addition to the other extraction techniques. Acoustic or ultrasonic cavitation is the basis for the operation of ultrasound-assisted extraction.[4]

Principle

The process of ultrasound-assisted extraction involves the coupling of low-frequency, high-power ultrasound waves into a botanical material slurry in a solvent. Using a probe-style ultrasonic processor, high-power ultrasonic waves are coupled into the slurry. Acoustic cavitation is the result of highly energetic ultrasound waves traveling through the liquid and producing alternating cycles of high and low pressure. Localized extremes in temperature, pressure, heating/cooling rates, pressure differentials, and shear forces in the medium can result from acoustic or ultrasonic cavitation. Micro-jets and inter-particular collisions cause effects like surface peeling, erosion, particle breakdown, sonoporation (the perforation of cell walls and cell membranes), and cell disruption when cavitation bubbles implode on the surface of solids.[2]

In liquid media, the implosion of cavitation bubbles produces micro-mixing and macro-turbulence. Since sonication causes cavitation and its associated mechanisms, such as micro-movement by liquid jets, compression, and decompression in the material with the consequent disruption of cell walls, as well as high heating and cooling rates. To produce significant cavitation, probe-type ultrasonicators can produce very high amplitudes. Flow cells and pressurized ultrasonic reactors are utilized to increase cavitation. The destructiveness of cavitation and cavitational shear forces increases with pressure.[2][5]

Associated mechanisms

Fragmentation refers to the process of dividing matrix particles into tinier fragments using ultrasound. This occurs as particles impact each other and shockwaves are produced by the bursting of solution bubbles.[6]

Erosion is based on the collapse of cavitation bubbles, which release solid structures into the extractive solvent from the matrix.[6]

The extraction rate is increased by the increased solvent penetration into the matrix's pores and canals because of the ultrasonic capillary effect.[7] Ultrasounds are used to break up solid matrices.[7]

Through the formation of membrane pores, sonoporation increases the permeability of cell membranes, facilitating the release of intracellular products into the extractive medium.[8]

Applying ultrasonic waves to liquid media causes shear forces to be applied to the matrix surface, which in turn causes the structures to rupture and release inner compounds into the solvent.[6]

Associated parameters

The extraction yields attributed to UAE are dependent on a number of variables, these can be divided into three categories: physical parameters, medium and matrix effects parameters, and others.[9]

Physical parameters

The physical parameters are linked to the equipment used for the extraction process as well as the ultrasonic waves used during UAE. In this sense, ultrasonic wave parameters are power, frequency, and ultrasound intensity (UI), while ultrasonic equipment parameters are extraction time (ET) and the size and shape of ultrasonic reactors. Equation (1) defines power as the rate of sound energy emission per unit of time. Power is dependent on solvent mass (m), solvent heat capacity at constant pressure (Cp), and T variation with time. High power values typically result in higher UAE efficiency in terms of yield and extract composition; multiple studies have suggested that this is partly due to the creation of strong shear forces.

P = m × Cp × (dT/d) | (1)[5]

As a result, this parameter needs to be methodically optimized while creating production plans for the food sector. Frequency influences the physical and biochemical consequences of bubble collapse during the extraction process, reducing rarefaction cycles and increasing cavitation. Low frequencies between 20-100 kHz cause high-intensity bubble collapses with an increased propagation of shearing forces within the solvent, requiring lower power values to achieve cavitation.

Increasing ET increases extraction yields; however, long runs can lead to overexposure to ultrasonic waves. The majority of ultrasound devices display ET, which can range from a few minutes to an hour.[5]

Medium parameters

The space where ultrasonic waves are transmitted from the emitting source to the matrix is called the medium parameter. Solvent dissolves the content released from matrices. Solvent polarity may be used to ensure that the target analytes are soluble. Consequently, the target compound determines the solvent to be used. For instance, water is the most often used solvent when extracting polar compounds like protein and carbohydrates.[5]

Higher UI values are required for solvents with high surface tension or viscosity to reach the cavitation threshold. Solvent vapor pressure lower values allow for more easily propagated bubble collapse power within the medium.[8]

While a rise in temperature (T) can result in a decrease in solvent viscosity and surface tension, it can also cause an increase in solvent vapor pressure. That in turn can lead to more gas entering bubbles and lessening their collapse and expansion. High T therefore does not increase the extractive yield of compounds from a matrix in ultrasonic devices. An increase in T accelerates diffusion rates and breaks down the matrix's external chemical bonds.

Matrix parameters

With UAE, a wide range of matrices, including those from microbial, marine, and plant sources, have been successfully extracted. Some studies have found that using a matrix in a wet or dry manner leads to higher recovery rates when extracting algae.[5]

Effects

  • Disruption of ultrasonic cells and enhancement of mass transfer by disrupting cells and improving mass transfer in the boundary layer encircling the solid matrix.
  • Ultrasound-induced cavitation has mechanical effects, causing variations in temperature and pressure, shock waves, shear forces, liquid jets, and microstreaming. These effects facilitate the transfer of intercellular materials into the solvent and enhance the solvent's penetration into the cell's interior.
  • Sonoporation is a process that involves puncturing cell walls and membranes to increase their permeability. It is frequently used as a transitional step before sonication completely disrupts the cells.[5]

References

  1. ↑ Mussatto, Solange (2014-11-04). "Generating Biomedical Polyphenolic Compounds from Spent Coffee or Silverskin". Coffee in Health and Disease Prevention: 93-106. doi:10.1016/B978-0-12-409517-5.00011-5. ISBN 9780124095175. Retrieved 2023-11-10.
  2. 1 2 3 Idoudi, Sourour; Ben Othman, Khadija; Bouajila, Jalloul; Tourrette, Audrey; Romdhane, Mehrez; Elfalleh, Walid (2023-03-29). "Influence of Extraction Techniques and Solvents on the Antioxidant and Biological Potential of Different Parts of Scorzonera undulata". Life. 13 (4): 904. Bibcode:2023Life...13..904I. doi:10.3390/life13040904. PMC 10140856. PMID 37109433.
  3. ↑ Catherin Vaska, Susan; Muralakar, Pavankumar; H.S, Arunkumar; D, Manoj; Nadiger, Seemantini; D, Jeevitha; Chimmalagi, Umesh; T V, Vinay; M, Nagaraju (2023-07-04). "CURRENT TRENDS IN PRODUCTION AND PROCESSING OF FISH OILS & ITS CHEMICAL ANALYTICAL TECHNIQUES: AN OVERVIEW". European Chemical Bulletin. 12 (5): 1705-1725. doi:10.48047/ecb/2023.12.si5a.049 (inactive 2023-11-26).{{cite journal}}: CS1 maint: DOI inactive as of November 2023 (link)
  4. ↑ Petigny, Loïc; Périno-Issartier, Sandrine; Wajsman, Joël; Chemat, Farid (2013-03-12). "Batch and Continuous Ultrasound Assisted Extraction of Boldo Leaves (Peumus boldus Mol.)". International Journal of Molecular Sciences. 14 (3): 5750–5764. doi:10.3390/ijms14035750. PMC 3634473. PMID 23481637.
  5. 1 2 3 4 5 6 Carreira-Casais, Anxo; Otero, Paz; Garcia-Perez, Pascual; Garcia-Oliveira, Paula; G. Pereira, Antia; Carpena, Maria; Soria-Lopez, Anton; Simal-Gandara, Jesus; A. Prieto, Miguel (2021-08-30). "Benefits and Drawbacks of Ultrasound-Assisted Extraction for the Recovery of Bioactive Compounds from Marine Algae". International Journal of Environmental Research and Public Health. 18 (17): 9153. doi:10.3390/ijerph18179153. PMC 8431298. PMID 34501743.
  6. 1 2 3 Chemat, Farid; Rombaut, Natacha; Fabiano-Tixier, Anne-Sylvie; Abert-Vian, Maryline; Meullemiestre, Alice; Sicaire, Anne-Gaëlle (2016-06-23). "Ultrasound assisted extraction of food and natural products. Mechanisms, techniques, combinations, protocols and applications. A review". Ultrasonics Sonochemistry. 34: 540–560. doi:10.1016/j.ultsonch.2016.06.035. PMID 27773280.
  7. 1 2 Pingret Kipman, Daniella; Fabiano-Tixier, Anne-Sylvie; Le Bourvellec, Carine; M G C Renard, Catherine; Chemat, Farid (2012-02-06). "Lab and pilot-scale ultrasound-assisted water extraction of polyphenols from apple pomace" (PDF). Journal of Food Engineering. 111 (1): 73-81. doi:10.1016/j.jfoodeng.2012.01.026. S2CID 98836013.
  8. 1 2 Meullemiestre, Alice; Breil, Cassandra; Abert-Vian, Maryline; Chemat, Farid (2016-03-18). "Microwave, ultrasound, thermal treatments, and bead milling as intensification techniques for extraction of lipids from oleaginous Yarrowia lipolytica yeast for a biojetfuel application" (PDF). Bioresource Technology. 211: 190–199. doi:10.1016/j.biortech.2016.03.040. PMID 27017129. S2CID 206147471.
  9. ↑ Carreira-Casais, Anxo; Carpena, Maria; Pereira, Antia G.; Chamorro, Franklin; Soria-Lopez, Anton; Perez, Pascual Garcia; Otero, Paz; Cao, Hui; Xiao, Jianbo; Simal-Gandara, Jesus; Prieto, Miguel A. (2021). "Critical Variables Influencing the Ultrasound-Assisted Extraction of Bioactive Compounds—A Review". Chemistry Proceedings. 5 (1): 50. doi:10.3390/CSAC2021-10562. ISSN 2673-4583.
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