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High-power ultrasonic system for the enhancement of mass transfer in supercritical CO2 extraction processes


Abstract and Figures

Oil is an important component of almonds and other vegetable substrates that can show an influence on human health. In this work the development and validation of an innovative, robust, stable, reliable and efficient ultrasonic system at pilot scale to assist supercritical CO(2) extraction of oils from different substrates is presented. In the extraction procedure ultrasonic energy represents an efficient way of producing deep agitation enhancing mass transfer processes because of some mechanisms (radiation pressure, streaming, agitation, high amplitude vibrations, etc.). A previous work to this research pointed out the feasibility of integrating an ultrasonic field inside a supercritical extractor without losing a significant volume fraction. This pioneer method enabled to accelerate mass transfer and then, improving supercritical extraction times. To commercially develop the new procedure fulfilling industrial requirements, a new configuration device has been designed, implemented, tested and successfully validated for supercritical fluid extraction of oil from different vegetable substrates.
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High-power ultrasonic system for the enhancement of mass transfer
in supercritical CO
extraction processes
Enrique Riera
, Alfonso Blanco
, José García
, José Benedito
, Antonio Mulet
, Juan A. Gallego-Juárez
Miguel Blasco
Grupo de Ultrasonidos de Potencia, Dpto. Señales, Sistemas y Tecnologías Ultrasónicas, Instituto de Acústica, CSIC, Serrano 144, E28006 Madrid, Spain
Instituto de Física Aplicada, CSIC, Serrano 144, E28006 Madrid, Spain
Centro Tecnológico AINIA, Benjamín Franklin 5-11, E46980 Paterna, Valencia, Spain
Dpto. Tecnología de Alimentos, Universidad Politécnica de Valencia, Camino de Vera s/n, E46022 Valencia, Spain
article info
Article history:
Received 30 June 2009
Received in revised form 16 September
Accepted 16 September 2009
Available online 20 September 2009
Ultrasonic processes
Power ultrasound
Mass transport
Supercritical fluid extraction
Carbon dioxide
Oil is an important component of almonds and other vegetable substrates that can show an influence on
human health. In this work the development and validation of an innovative, robust, stable, reliable and
efficient ultrasonic system at pilot scale to assist supercritical CO
extraction of oils from different sub-
strates is presented. In the extraction procedure ultrasonic energy represents an efficient way of produc-
ing deep agitation enhancing mass transfer processes because of some mechanisms (radiation pressure,
streaming, agitation, high amplitude vibrations, etc.).
A previous work to this research pointed out the feasibility of integrating an ultrasonic field inside a
supercritical extractor without losing a significant volume fraction. This pioneer method enabled to accel-
erate mass transfer and then, improving supercritical extraction times. To commercially develop the new
procedure fulfilling industrial requirements, a new configuration device has been designed, implemented,
tested and successfully validated for supercritical fluid extraction of oil from different vegetable
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
The use of fluids, such as CO
, under supercritical conditions for
extraction is a current useful technique. However, it has some lim-
itations [1,2]. First of all, it requires high-pressure equipment,
which may be considered as the most serious drawback of the
technology in comparison to traditional atmospheric pressure
extraction techniques. High pressure facilities create a potential
safety hazard that has to be carefully managed. Additionally,
uncontrolled release of large quantities of carbon dioxide can
asphyxiate bystanders owing to air displacement. Strict technical
and economical requirements have to be fulfilled to perform super-
critical extraction at large scale. Special and sometimes complex
closures and joints have to be used to stand high pressures and
thus, it is only possible to extract solids under batch modus. Also,
vessel diameters are constrained by mechanical manufacture pro-
cedures and thickness requirements, which make costs increase
exponentially as diameter grows. This way, a 200–1000 l vessel
may be used for industrial purposes. On the other hand, in industry
arrangements of parallel batch extractors of more than 1 m
considered to overcome the batch operating disadvantages and at-
tain a more efficient continuous like operation. Nevertheless, these
facts are not strong enough to avoid supercritical processes or
high-pressure processes and they have been applied at industrial
scale without special problems since decades.
Taking into account that supercritical extraction may be consid-
ered environmentally friendly and a green alternative to the use of
organic solvents, it may be concluded that it is worthy to apply
supercritical fluids for extraction at industrial levels.
In this way supercritical CO
is considered nowadays in the food
sector as an excellent solvent in the product extraction from vege-
tables. Extraction with supercritical carbon dioxide is considered as
a technology which has gained wide acceptance as an alternative to
conventional solvent extraction because of its important advanta-
ges (non-toxic, recyclable, cheap, relatively inert and non-flamma-
ble). Nevertheless, the economics of supercritical fluid extraction
(SFE) is affected by the slow kinetics of the process. Since high pres-
sures are normally used in SFE, mechanical stirring is difficult to be
applied. The application of new techniques such as the use of high-
power ultrasound (HPU) assisting this process has proved impor-
tant benefits as a consequence of the mechanical effects produced
in the supercritical environment through the high amplitude vibra-
tions, radiation pressure, streaming, agitation, etc. [3–7].
0041-624X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
* Corresponding author. Tel.: +34 915618806; fax: +34 914117651.
E-mail address: (E. Riera).
Ultrasonics 50 (2010) 306–309
Contents lists available at ScienceDirect
journal homepage:
Nowadays, high-intensity ultrasound is regarded as an emer-
gent technology in food, chemical and pharmaceutical industries
[8,9]. In particular, ultrasonic energy represents a clean way to
accelerate and improve mass transfer processes. In addition, the
use of energy would permit to obtain economically competitive
high quality food extracts. Previous studies indicate the improve-
ment of the supercritical CO
extraction of almond oil by using
HPU at laboratory scale [10]. Specifically, the application of HPU
to assist extraction process produced a relevant increase in the fi-
nal yield of the oil together with a noticeable reduction of the en-
ergy consumption through the increase of the extraction rate.
This paper deals with the implementation and validation at pi-
lot scale of an innovative ultrasonic system to assist supercritical
extraction which aims to be a robust, stable, reliable and effi-
cient solution to be applied at industrial scale. The ultrasonic de-
vice was designed and built to work at 19 kHz and to overcome
the fluctuations of the specific acoustic impedance of the fluid
medium during the extraction process under the operational con-
ditions (high pressure 6400 bar, temperatures up to 80 °C, mass
flow up to 20 kg/h and density of the CO
6900 g/cm
). The ultra-
sonic applied power was maintained constant during the extrac-
tion trials of oils from different substrates. A specific hardware
and software has been developed, tested and validated to control
and monitoring the parameters involved in the supercritical
extraction process assisted by power ultrasound.
2. Experimental
2.1. Ultrasound-assisted supercritical fluid extraction (USFE) system
As showed in [11] the USFE system is made up of two units: (a)
SFE unit and (b) HPU unit. The SFE pilot plant (AINIA, Valencia) was
built to withstand high pressures up to 350 bar and temperatures
up to 80 °C (see Fig. 1). The major components of SFE include a dia-
phragm pump, a high pressure extraction vessel with 5 L capacity,
two separation units (a cyclone and a decanter) and a set of sensors
to monitor and control temperature, pressure and fluid flow rate.
High purity CO
(99.9%) was used as a solvent in the extractor un-
der supercritical conditions (P
= 73.9 bar; T
= 31.1 °C; D
0.468 g/mL) [12].CO
was used because is the most commonly
used solvent for the extraction of oils from vegetables in supercrit-
ical processes due to its excellent behavior and low cost.
In the previous USFE device [4] an operator was in charge of the
control of the operational conditions in the SFE as well as the con-
trol of the ultrasonic system. Although promising results were ob-
tained in the almond-oil extraction tests, carried out at 280 bar,
55 °C and a flow rate of 20 kg/h with an ultrasonic transducer oper-
ating at a frequency of 18 kHz and a power of 50 W (faster kinetic
curves 30% and higher extraction yields 20%), some instabilities
in its behavior were detected. Those instabilities were caused by
the changes observed in the acoustic impedance of the medium
under supercritical conditions during the extraction process. In
other words, the ultrasonic system exhibited difficulties concern-
ing stability and that made it unable for industrial use. In parallel,
resonance modes of the metallic basket placed inside the extractor
(where the substrate is deposited) were detected in the first proto-
type giving rise to modal interactions that disturb operation. In the
new system such interactions have been eliminated by separating
both basket and transducer resonant frequencies up to a value of
about 1 kHz. To achieve it, the resonant frequency and the shape
of the new transducer was established by finite element methods
(FEM) In this work special attention has been given to the trans-
ducer characteristics (impedance, phase and power spectrum of
the current) as a function of extraction parameters (pressure, tem-
perature, flow rate, density), power applied and time during the
extraction operation.
The ultrasonic system presented here is a new version of the
previous one and can be considered as the second step to scale it
up for larger operation. In fact, the new device implemented defin-
itive advantages related to the automatic control required for
industrial applications.
The present ultrasonic system basically consists of: (a) the
ultrasonic transducer to work at 19 kHz with a maximum power
of about 110 W, (b) a dynamic resonance control unit (controller),
(c) a broadband power amplifier, (d) an impedance matching unit,
(e) a specific developed software to monitor and control the
parameters of the power transducer (voltage V, current I, phase ,
impedance Z , power P and frequency f) and those of the supercrit-
ical fluid (pressure P, temperature T, flow rate F and density D), and
(f) a computer with a data acquisition hardware. To achieve auto-
matic control, the new system, also allows the power characteriza-
tion of the transducer during the extraction process in real time. To
this purpose, a virtual high-power impedance analyzer for contin-
uous operation was developed with LabView code, tested and val-
US Signal
Data Acquisition
V, I, f
T, P, F, D
Fig. 1. Scheme of the SFE pilot plant assisted by power ultrasound. Units: (E) extractors, (S) separators, (C) cooler, (P) high pressure pump, (H) heater, (PT) pressure meter, (FT)
flow meter, (UST) ultrasonic transducer. Electrical parameters: (V) voltage, (I) current, (f) frequency. Extraction parameters: (T) temperature, (P) pressure, (F)CO
flow rate,
(D) density.
E. Riera et al. / Ultrasonics 50 (2010) 306–309
idated experimentally [9]. In this way, the transducer behavior
during the extraction process and the enhancement by ultrasound
on the kinetic curves and the oil extraction yields of two different
products, have been analyzed.
2.2. Materials and methods
Two examples of the potential of HPU in SFE processes are pre-
sented in this work: (a) grounded almonds sieved at 3–4 mm in
size (55% oil content, wet basis), and (b) a second grounded vege-
table product ‘‘cocoa cake” with similar particle size. In both cases,
an amount of about 1500 g, were deposited in the basket placed in
the extractor of 5 L capacity. The selection of the particle size of the
samples (3–4 mm) was done based on our previous results with
grounded almonds which confirm that small particulate size favors
the ultrasonic action. In addition, experimental trials were carried
out with a second substrate cocoa cake. The time for each trial was
about 3.5–4 h. The power output applied to the ultrasonic trans-
ducer was fixed and kept constant at 85 W in all the experiments
here presented. All the experimental trials were carried out with
and without ultrasound application and replicated twice.
3. Results and discussion
The ultrasonic transducer was placed inside the extractor in-
serted on the upper part of the vessel. At low power, an impedance
analyzer was used to measure the admittance response of the
transducer in the frequency range (19–20 kHz). Only one vibration
mode was detected in air at 19,228 Hz with an impedance of 90
The same mode was detected at high excitation but at 19.1 kHz.
The transducer has an estimated power capacity of 110 W.
3.1. Stability of the prototype
The power behavior of the new transducer driven at high-exci-
tation level was studied in air and inside the extractor during the
extraction process with supercritical CO
. First, the stability of
the prototype was tested and validated in air at 100 W during a
long time. The new transducer showed high-stability and good
performance during 8 h of continuous operation at its maximum
power capacity. Such experiment was repeated several times up
to reach a total number of 50 h following the high-power charac-
terization procedure described in [13]. No change was detected
in its behavior during the trials. Therefore, the power characteriza-
tion of this transducer validates it for SFE. In addition, in Fig. 3 it is
shown an example of another kind of driving signals, were applied
to study the transducer behavior in air. One example consisted in
applying a power modulation between 35 W and 90 W to analyze
the transducer response. Fig. 2 shows the response that can be con-
sidered very reliable.
The transducer was also characterized at high level excitation
inside the extractor of the SFE unit in order to study the effect of
the high-pressure conditions on its behavior. Its impedance in-
creases from 90
up to 260
, and the frequency decreases from
19.2 kHz up to 18.9 kHz when the value of the pressure varies from
200 bar up to 320 bar. In Fig. 3 it is plotted the evolution of the
power applied to the transducer versus time along one extraction
trial carried out at 85 W. It is clear from the picture that the re-
sponse of the ultrasonic device is quite stable also in this case.
3.2. Almonds-oil extraction trials
In order to study the effects of USFE in almond-oil extraction,
trials were carried out at various pressures (200–320 bar), two
extraction temperatures (45 and 60 °C), times (up to 3.5 h) and
flow rates (10–15 kg/h). The effect of the extraction pressure
was study. At 200 bar the improvement in the yield extracted
(mass transfer) was only 15% probably due to the low solubility
of the almond-oil in the supercritical CO
. However, the yield ex-
tracted from grounded almond at 320 bar, 45 °C and 10 kg/h gave
rise to 40% larger yields when HPU were applied as it is shown
in Figs. 4 and 5. Even larger improvements between extraction
curves with and without ultrasounds where achieved on experi-
ments carried out at 280 bar, 45 °C and 12.5 kg/h extraction yields
improvements of about 90% were obtained.
12:28 12:57 13:26 13:55 14:24 14:52 15:21 15:50
Power (Watts)
Fig. 2. Example of power modulation applied to the transducer.
12:00 14:2413:12 15:36 16:48
Power (Watts)
Fig. 3. Ultrasonic power versus time in an extraction trial carried out at 250 bar,
60 °C and 15 kg/h.
Time (h)
g extract/100 g product
Fig. 4. Almond-oil extraction curve at 320 bar and 45 °C with (d) and without (s)
308 E. Riera et al. / Ultrasonics 50 (2010) 306–309
3.3. Cocoa cake-oil extraction trials
A third set of trials was carried out with a different substrate,
cocoa beans. Solid samples were prepared for the experiments as
follows: initial substrate was milled and sieved before the treat-
ment in order to have a particle size distribution between 2 and
3.5 mm. Next, the samples were placed in the basket inside the
extractor to begin with the extraction trials at 320 bar and 65 °C.
Good results were also obtained in the oil extraction with ultra-
sound. In fact, as shown in Fig. 6, the application of the ultrasonic
energy increases the extracted yield in around 43%.
4. Conclusions
An innovative system for ultrasonic application in supercritical
extraction processes at pilot plant scale was implemented and val-
idated experimentally. The system has shown to be a robust, sta-
ble, reliable and efficient solution potentially applicable at
industrial scale. The behavior of the system driven at high-power
levels showed high-stability and good performance during the tri-
als. In addition, the power ultrasonic system operates in an auto-
matic way during the extraction process, so that it is not
required any manual intervention by external operator. This fact
represents a relevant advance with respect to our previously devel-
oped ultrasonic device.
The new system confirms the high effect of the application of
ultrasonic energy in the SFE processes. In addition, the high stabil-
ity of such system gave rise to a clear enhancement of the results.
In fact, by using the previous ultrasonic system improvements of
about 20% in almond-oil extraction yields were achieved, while
with the present system the improvements reached up to 90%.
The new system has also been used with other substrates as co-
coa cake obtaining enhancements in the yield extraction of about
Work supported by the National Research Project PETRI-PTR95-
075.OP.02. The authors would like to thank V.M. Acosta for his col-
laboration in the design of the power transducers by FEM and their
[1] E.J. Beckman, Supercritical and near-critical CO
in green chemical synthesis
and processing, Journal of Supercritical Fluids 28 (2004) 121–191.
[2] E. Reverchon, I. De Marco, Supercritical fluid extraction and fractionation of
natural matter, Journal of Supercritical Fluids 38 (2006) 146–166.
[3] C. Jun, Y. Kedie, C. Shulai, T. Adschiri, K. Arai, Effects of ultrasound on mass
transfer in supercritical extraction, in: 4th International Symposium on
Supercritical Fluids, 11–14 May, Sendai, Japan, 1997 pp. 707–710.
[4] E. Riera, Y. Golás, A. Blanco, J.A. Gallego, M. Blasco, A. Mulet, Mass transfer in
supercritical fluids extraction by means of power ultrasound, Ultrasonics
Sonochemistry 11 (2004) 241–244.
[5] S. Balachandran, S.E. Kentish, R. Mawson, M. Ashokkumar, Ultrasonic
enhancement of the supercritical extraction from ginger, Ultrasonics
Sonochemistry 13 (2006) 471–479.
[6] A. Hu, S. Zhao, H. Liang, T. Qiu, G. Chen, Ultrasound assisted supercritical fluid
extraction of oil and coixenolide from adlay seed, Ultrasonics Sonochemistry
14 (2007) 219–224.
[7] M.D. Macías-Sánchez, C. Mantell, M. Rodríguez, E. Martínez de la Ossa, L.M.
Lubián, O. Montero, Comparison of supercritical fluid and ultrasound-assisted
extraction of carotenoids and chlorophyll a from Dunaliella salina, Talanta 77
(2009) 948–952.
[8] T. Mason, E. Riera, A. Vercet, P. Lopez-Buesa, Applications of Ultrasound, in:
DA-Wen Sun (Ed.), Emerging Technologies for Food Processing, Elsevier,
2005, pp. 323–352 (Chapter 13). ISBN 0-12-676757-2.
[9] M. Vinatoru, An overview of the ultrasonically assisted extraction of bioactive
principles from herbs, Ultrasonic Sonochemistry 8 (2001) 303–313.
[10] E. Riera, J.A. Gallego, F. Montoya, A. Blanco, A. Mulet, J.J. Benedito, R. Peña, Y.
Golás, A. Berna, S. Subirats, M. Blasco, J. García, Separation or Extraction
Method Using Supercritical Fluids Assisted by High-intensity Ultrasound,
2004, EP 1547679A1.
[11] E. Riera, A. Blanco, V.M. Acosta, J.A. Gallego-Juárez, M. Blasco, A. Mulet,
Prototype for the use of ultrasound in supercritical media, in: Proceedings of
the International Congress on Acoustics, Madrid (Spain), 2–7 September
[12] S.L. Taylor, N.B.A. Higley, R.K. Bush, Sulphites in food, Advances in Food
Research 30 (1986) 62–64.
[13] E. Riera, J.A. Gallego, A. Blanco, V.M. Acosta, Power characterization of
ultrasonic piezoelectric transducers, in: ICU2007 (International Congress on
Ultrasonics); Electronic Proceedings Paper 1435, Vienna (Austria), 9–13 April,
Time (h)
g extract/100 g product
Fig. 6. Cocoa cake-oil extraction curve at 320 bar and 65 °C with (d) and without
(s) ultrasounds.
01 23
Time (h)
g extract/100 g product
Fig. 5. Almond-oil extraction curve at 280 bar and 45 °C with (d) and without (s)
E. Riera et al. / Ultrasonics 50 (2010) 306–309
... The environmentally friendly supercritical fluid can avoid organic solvent discharge, which promotes the rapid development of SFE. Nonetheless, lipid extraction from the solid matrix with SFE has low kinetics, so UA-SFE is developed to enhance the mass transfer of cellular compounds (dos Hu et al., 2007;Riera et al., 2010). Ultrasound can produce intense mechanical effects in the supercritical fluid to promote the extraction (Riera et al., 2010); namely, ultrasound is not used as a pre-treatment. ...
... Nonetheless, lipid extraction from the solid matrix with SFE has low kinetics, so UA-SFE is developed to enhance the mass transfer of cellular compounds (dos Hu et al., 2007;Riera et al., 2010). Ultrasound can produce intense mechanical effects in the supercritical fluid to promote the extraction (Riera et al., 2010); namely, ultrasound is not used as a pre-treatment. Riera et al. (2010) studied the extraction kinetics of almond oil using UA-SFE, finding that UA-SFE dramatically elevates the mass transfer of SFE thus improving the lipid contents and shortening the extraction time significantly. ...
... Ultrasound can produce intense mechanical effects in the supercritical fluid to promote the extraction (Riera et al., 2010); namely, ultrasound is not used as a pre-treatment. Riera et al. (2010) studied the extraction kinetics of almond oil using UA-SFE, finding that UA-SFE dramatically elevates the mass transfer of SFE thus improving the lipid contents and shortening the extraction time significantly. Wei et al. (2016) obtained 23.31% of lipids contents at 75% duty cycle, temperature of 44.0 • C, pressure of 18.5 MPa, particle size of 0.355 mm, CO 2 flow rate of 1.4 g/min and extraction time of 115 min, higher than the contents of heat reflux extraction for 240 min. ...
Full-text available
Backgrounds Lipids are increasingly attractive in the food industry, resulting in an increasing demand for lipids from edible and non-edible sources. Conventional solvent extraction has drawbacks of low efficiency, long time, and large solvent consumption, and it can negatively impact the lipid quality such as oxidation due to long extraction time and high temperature. Ultrasound-assisted extraction (UAE) can overcome these shortcomings and has received more attention. Whereas, a comprehensive evaluation of ultrasound-assisted lipid extraction is not yet available. Scope and approach This review focuses on an in-depth understanding of ultrasound-assisted lipid extraction, including mechanisms, solvent systems, feedstocks, the impacts of ultrasound on lipid quality (constituents, antioxidant, stability and antibacterial properties), and ultrasound coupled extraction technologies (enzyme, hydrodistillation, microwave and supercritical fluid). Key findings and conclusions The mechanisms of UAE involve cavitation effects, which can destroy cells and enhance mass transfer. Solvent plays a vital role in the extraction process. Different levels of ultrasonic energy release capabilities may occur in various solvents. UAE has good compatibility and is suitable for the treatment of materials from various origins including plants, microalgae, animals and fungi. UAE can improve extraction efficiency and lipid quality. Ultrasonic treatment has a positive influence on the composition, anti-oxidation, stability and antimicrobial properties. Ultrasonic coupled extraction technologies normally extract lipids more efficiently due to the synergistic effect. Therefore, according to current literature, UAE can occupy a very important position in the lipid extraction industry.
... According to Krzyczkowska and Kozłowska (2017), although chloroform/methanol improved oil yield by extraction of both nonpolar and polar lipids, hexane is an ideal solvent for nonpolar lipids extraction and the isolation of all volatile compounds. It should be noted that the unpleasant smells and tastes in the resulting oil and the chemical toxicity related to organic solvents (e.g., chloroform/methanol and hexane) can affect the nutritional compounds of almond oil and lead to big health problems, which make it unsuitable for human consumption unless it is subjected to a refining process (Joshi & Rabadán et al., 2017;Sena-Moreno et al., 2016 Screw press -Deliver the pleasant sensory characteristics of almonds -Used at an industrial scale -Higher oil yield ready for consumption -Possibility of continuous or semi-continuous processes -Environmentally friendly -Shorter processing time -High-quality oil at low temperature -Lower price -Large number of almond kernels required -Heating of the tip could alter the chemical composition and stability of the extracted oil Al Martínez et al., 2013Martínez et al., , 2017Özcan, Al Juhaimi, et al., 2020;Sena-Moreno et al., 2016 Solvent extraction -Most commonly used commercially -Very simple -Cheap -High efficiency -Continuous extraction method -Long extraction time -Large volume of solvent required -Unpleasant smell and taste -Toxicity and highly flammable -Solvent recovery is energy-intensive -Negative environmental impacts Al Miraliakbari & Shahidi, 2008a, 2008bÖzcan, Al Juhaimi et al., 2020 Aqueous extraction process -Simple and eco-friendly -Oil quality much superior to oil obtained by hexane Balvardi et al., 2015;Pićurić-Jovanović & Milovanović, 1993;Souza et al., 2019 Ultrasound-assisted extraction -Reduced extraction time -Reduced solvent consumption -Higher yield -Safe and environmentally friendly technology -Reduce significantly the content of hydrocyanic acid -High power consumption Riera et al., 2010;Roohinejad et al., 2017;Sharma & Gupta, 2004, 2006 Supercritical carbon dioxide extraction -Green technology -Reduced time -High quality -Oil yield increased with increasing pressure, temperature, and flow rate -Very high cost associated with infrastructure investment and process operation -Requires higher pressures and temperatures Femenia et al., 2001;Leo et al., 2005;Marrone et al., 1998;Mericli et al., 2017; Subcritical fluid extraction -Environmentally friendly -Higher yield and phytochemical content -Short extraction time -Better oil quality compared to cold-press and hydraulic press -No required refining -Lower oil moisture content -Safe and cost-effective -Elevated temperature is needed -Thermal degradation of some thermolabile compounds at elevated temperatures -A greater volume of extraction fluid (subcritical water) is needed Qi et al., 2019;Zhang et al., 2020Zhang et al., et al., 2016. Besides, hexane is not recommended due to its negative environmental impacts. ...
... The same authors reported later that a 2-min ultrasonic pretreatment at 70 W significantly increased the oil yield obtained by aqueous enzymatic extraction from 77% to 95% (w/w) and reduced the extraction time from 18 to 6 hr (Sharma & Gupta, 2006). At a laboratory scale, the use of high-power ultrasound assisting supercritical CO 2 extraction process showed an almond oil yield of about 90% (Riera et al., 2010). A recent study by showed that autoclaving treatment before ultrasound-assisted oil extraction increased the oil recovery by 8.69%, without affecting the almond oil composition. ...
Almond oil, a rich source of macronutrients and micronutrients, is extracted for food flavorings and the cosmetics industry. In recent years, the need for high-quality and high-quantity production of almond oil for human consumption has been increased. The present review examines the chemical composition of almond oil, storage conditions, and clinical evidence supporting the health benefits of almond oil. From the reviewed studies, it appears that almond oil contains a significant proportion of poly and monounsaturated fatty acids, with oleic acid as the main compound, and an important amount of tocopherol and phytosterol content. Some variations in almond oil composition can be found depending on the kernel's origin and the extraction system used. Some new technologies such as ultrasonic-assisted extraction, supercritical fluid extraction, subcritical fluid extraction, and salt-assisted aqueous extraction have emerged as the most promising extraction techniques that allow eco-friendly and effective recovery of almond oil. This safe oil was reported by several clinical studies to have potential roles in cardiovascular risk management, glucose homeostasis, oxidative stress reduction, neuroprotection, and many dermatologic and cosmetic applications. However, the anticarcinogenic and fertility benefits of almond oil have yet to be experimentally verified. K E Y W O R D S
... Water is a supercritical substance when its temperature is above 374 C and pressure is above 22.1 MPa and carbon dioxide is above 31.1 C and 7.36 MPa (Fig. 6) [135]. Carbon dioxide is a highly used supercritical fluid because of its low critical conditions, low-cost, non-toxic, nonflammable, eco-friendly, and recyclable properties [136]. ...
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The successful conversion of lignocellulose into value-added products depends on overcoming the recalcitrance of its structure towards enzymatic digestion. The highly crosslinked structure of lignin, crystallinity of cellulose, and low digestibility of hemicellulose create the recalcitrance. Many studies have proved that an appropriate pretreatment method could enhance the digestibility of lignocellulosic biomass by weakening the strong network of its chemical bonds among the cellulose, hemicellulose, and lignin. There are several conventional ways to separate the components from each other, but the requirements of high temperature and pressure, use of strong acids and bases, and expensive instrumentation make the pretreatment methods difficult to use. Greener solvents, e.g. supercritical fluid, ionic liquid, and deep eutectic solvent (DES)-based pretreatment techniques can overcome the difficulties. Although a lot of pilot scale and rigorous studies are required to launch the greener technologies commercially, they have already shown a lot of promise in the field of biomass pretreatments. Among the greener solvents, DESs are cheaper, easily recyclable, environmentally benign, and the efficiency of the DES-based pretreatment can be enhanced manifold by applying microwave and ultrasound. Therefore, DES-based pretreatment could be one of the most popular techniques in the future.
The main objective of this study was to improve the extractability and quality of rice bran oil using different mixtures of ethanol (Eth) and hexane (He). Eth/He ratios of 0:100, 20:80, 40:60, 60:40, 80:20, and 100:0 (%v/v) were used for the extraction. The ultrasound extraction processes were experimented at 2.5 W/g, 30 °C for 15 min. The results indicated that the highest oil extractability was found in the 60:40 (%v/v) Eth/He mixture. Experimental results also showed that the mixture of 60:40 (%v/v) Eth/He had significant effect on the physiochemical properties and phytochemical content of crude rice bran oil (p
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Due to the interest in identifying cost-effective techniques that can guarantee the microbiological, nutritional, and sensorial aspects of food products, this study investigates the effect of CO2 preservation treatment on the sensory quality of pomegranate juice at t0 and after a conservation period of four weeks at 4 °C (t28). The same initial batch of freshly squeezed non-treated (NT) juice was subjected to non-thermal preservation treatments with supercritical carbon dioxide (CO2), and with a combination of supercritical carbon dioxide and ultrasound (CO2-US). As control samples, two other juices were produced from the same NT batch: A juice stabilized with high pressure treatment (HPP) and a juice pasteurized at high temperature (HT), which represent an already established non-thermal preservation technique and the conventional thermal treatment. Projective mapping and check-all-that-apply methodologies were performed to determine the sensory qualitative differences between the juices. The volatile profile of the juices was characterized by gas chromatography-mass spectrometry. The results showed that juices treated with supercritical CO2 could be differentiated from NT, mainly by the perceived odor and volatile compound concentration, with a depletion of alcohols, esters, ketones, and terpenes and an increase in aldehydes. For example, in relation to the NT juice, limonene decreased by 95% and 90%, 1-hexanol decreased by 9% and 17%, and camphene decreased by 94% and 85% in the CO2 and CO2-US treated juices, respectively. Regarding perceived flavor, the CO2-treated juice was not clearly differentiated from NT. Changes in the volatile profile induced by storage at 4 °C led to perceivable differences in the odor quality of all juices, especially the juice treated with CO2-US, which underwent a significant depletion of all major volatile compounds during storage. The results suggest that the supercritical CO2 process conditions need to be optimized to minimize impacts on sensory quality and the volatile profile.
The aim of this study was to analyze the application of supercritical carbon dioxide combined with high-power ultrasound (SC-CO2 + HPU) and the use of a saline solution (SS; 0.85% NaCl) on the microbial inactivation and the quality of dry-cured ham. The effect of temperature, pressure and treatment time was studied using RSM. Physicochemical analyses were carried out after the treatments and during refrigerated storage (30 days / 4 °C). The most significant inactivation of Escherichia coli (3.62 ± 0.20-log CFU/g) was obtained using the SC-CO2 + HPU + SS (25 MPa, 46-°C and 10-min), with temperature being the most important process variable. Fat content showed a significant (p < 0.05) reduction (46%) after the SC-CO2 + HPU treatment. The breakage of the muscle fibers, the disorganization in the myofibrils, as well as the enlargement of the interfibrillar spaces led to the ham softening (avg 26.5%). No significant (p > 0.05) changes in color, texture or pH were found during storage. Thus, ultrasonic-assisted SC-CO2 could be used, in combination or not with SS, to improve the shelf of dry-cured ham. Industrial relevance Supercritical carbon dioxide (SC-CO2) inactivation technology has been shown to be highly efficient at reducing different bacteria in liquid media with minimum effect on food quality. This technology is barely applied to solid products and its use is limited by the long processing times and reduced inactivation capacity. The application of high-power ultrasound (HPU) leads to a shorter process time. This technology is useful for the inactivation of ham microbiota and inoculated E.coli. A liquid medium surrounding the treated solid can enhance microbial inactivation for the purposes of improving the effect of ultrasound cavitation, while only minimally affecting the quality of the samples (color, texture, fat and moisture contents).
Six bioactive flavonoids were isolated from Scutellaria barbata D. Don through heat-reflux, ultrasound-assisted, conventional supercritical CO2 and ultrasound-assisted supercritical CO2 (USC-CO2) extractions using different extraction schemes and parameters. The USC-CO2 extraction method produced higher yields of six flavonoids that were 28.09–29.31, 24.64–27.74 and 18.63–19.03% higher than those of heat-reflux, ultrasound-assisted and conventional supercritical CO2 extractions, respectively, with time durations that were lower by factors of 2.29, 1.14 and 2 than those of the three other extraction techniques and with less-harsh operating conditions. Therefore, the current procedure is a promising technique for the extraction of various bioactive constituents from a wide variety of raw matrixes. Furthermore, a second-order kinetic model and a mass transfer model based on Fick’s second law were successfully correlated with the overall USC-CO2 dynamic extraction of S. barbata D. Don. The results obtained from the second-order kinetic model indicated that the energy barrier in the USC-CO2 procedure was lower than that in the traditional extraction techniques. In addition, the mass transfer model revealed that incrementing the operation temperature from 32 to 52 °C at constant pressure might effectively enhance the mass transfer and diffusion in the current procedure and that the current procedure is dominated by intraparticle diffusion. These results provide very helpful information for the design and development of an efficient procedure to extract bioactive flavonoids from a wide variety of matrixes for future applications in industrial extraction processes.
Background Supercritical CO2 (SCCO2) extraction is a novel technology, with numerous advantages over conventional extraction methods, such as improved kinetics, extract quality, and environmental sustainability. Nevertheless, low yield and high cost relative to conventional extraction methods limit its industrial practicality. Ultrasound assistance may be useful in addressing some of these limitations, although it simultaneously affects multiple aspects of SCCO2 extraction. An understanding of these effects is useful to harness ultrasound to address current limitations of SCCO2 extraction. Scope and approach In this review the mechanisms of ultrasound assistance are considered in the context of supercritical CO2. These mechanisms are further analyzed to describe the effects of ultrasound on extraction kinetics and to determine the effects of ultrasound under different operating conditions. Ultimately, an understanding of these factors provides a basis to observe the effects of ultrasound on the accuracy of mathematical modelling and the commercialization potential of ultrasound-assisted SCCO2 extraction. Key findings and conclusions While there is a promising outlook for ultrasound-assisted SCCO2 extraction, its benefits are not universal across all extraction conditions. Particularly, its effects are lessened when the substrate particle size is optimized. Ultrasound may also increase temperature, leading to reduced extraction efficiency. While preliminary results in some research work indicate that high-power ultrasound for a short duration is effective, future work should continue to address optimal ultrasound operating parameters. Despite notable reductions in the accuracy of mathematical modelling, due to ultrasound, some adapted models have achieved comparable accuracy. To limit the challenges of a coupled ultrasonic SCCO2 process, a hyphenated process may also be suitable.
In China, the rapid development greatly promotes the national economic power and living standard but also inevitably brings a series of environmental problems. In order to resolve these problems fundamentally, Chinese scientists have been undertaking research in the area of green chemical engineering (GCE) for many years and achieved great progresses. In this paper, we reviewed the research progresses related to GCE in China and screened four typical topics related to the Chinese resources characteristics and environmental requirements, i.e. ionic liquids and their applications, biomass utilization and bio-based materials/products, green solvent-mediated extraction technologies, and cold plasmas for coal conversion. Afterwards, the perspectives and development tendencies of GCE were proposed, and the challenges which will be faced while developing available industrial technologies in China were mentioned.
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The development and application of power ultrasonic transducers implies a proper characterization of their behaviour under power operation. As well known, problems such as heating, nonlinear interactions of vibrating modes, fatigue, etc., are specifically produced at high excitation levels. To study the different transducer behaviour at low and high-power conditions a specific system has been developed and tested. Such a system is based on a combination of the electrical excitation with electrical, vibrational and acoustical measurements. Special hardware and software has been developed for the excitation, control and signal recording and processing in real time. The characterization system allows the control and monitoring of the main parameters of the transducer: a) voltage and current sampled on the out-port-side of the impedance matching unit; b) vibration amplitude and phase sampled by a laser scanning vibrometer; c) temperature sampled by thermocouple and infrared probe and, d) acoustic pressure sampled by microphone or hydrophone. Results clearly show the benefits of the developed tool in the re-design and optimization of power ultrasonic transducers for industrial processing.
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Ponencia presentada en el XIX Congreso Internacional de Acústica (ICA2007), Madrid, 2-7 Sep 2007.-- PACS: 43.35.-C. The use of power ultrasound together with supercritical CO2 is a non-conventional promising technique for extraction processes in food industries. Extraction of almond oil, adlay seed oil, pungent from ginger are good examples of the potential use of this novel technology. In fact, power ultrasound represents an efficient manner of producing agitation in the media enhancing mass transfer on supercritical fluids extraction processes. A prototype for the use of ultrasound in supercritical media is presented in this paper. Special attention has been given to the transducer and its behaviour as a function of power and time during operation. Specific software to control and monitoring the parameters involved in the process has been developed. This tool will allow the best conditions for the operation process to be selected. We are grateful for financial support from the National Research Project PETRI-PTR95- 075.OP.02. Peer reviewed
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This paper presents a review of the ultrasonically assisted extraction of bioactive principles from herbs. Much of the work was carried out under European community grants under the COPERNICUS programme and in a COST D10 network. Some aspects of classical and non-conventional extraction procedures are also presented and briefly discussed.
Major mechanical effects of ultrasound are provided when the power is sufficiently high to cause cavitation. Like any sound wave, ultrasound is propagated via a series of compression and rarefaction waves induced in the molecules of the medium through which it passes. At sufficiently high power, the rarefaction cycle may exceed the attractive forces of the molecules of the liquid and cavitation bubbles will form. Such bubbles grow by a process known as rectified diffusion, that is, small amounts of vapor (or gas) from the medium enters the bubble during its expansion phase and is not fully expelled during compression. The effectiveness of ultrasound as a food processing tool has been proven in the laboratory and there are a number of examples of scale-up. In most cases, commercially available frequency is used, that is 20 or 40 kHz, and this has proved quite satisfactory. In such cases, the variable parameters are temperature, treatment time, and acoustic power. Little attention has been paid to the use of different frequencies except in a few cases. One such is the use of ultrasound in food preservation using the bactericidal action of sonication combined with other techniques such as heat, ultraviolet light, and the use of a biocide.
Carbon dioxide is often promoted as a sustainable solvent, as CO2 is non-flammable, exhibits a relatively low toxicity and is naturally abundant. However, injudicious use of carbon dioxide in a process or product can reduce rather than enhance overall sustainability. This review specifically examines the use of CO2 to create greener processes and products, with a focus on research and commercialization efforts performed since 1995. The literature reveals that use of CO2 has permeated almost all facets of the chemical industry and that careful application of CO2 technology can result in products (and processes) that are cleaner, less expensive and of higher quality.
Supercritical extraction and fractionation of natural matter is one of the early and most studied applications in the field of supercritical fluids. In the last 10 years, studies on the extraction of classical compounds like essential and seed oils from various sources: seeds, fruits, leaves, flowers, rhizomes, etc., with or without the addition of a co-solvent have been published. Supercritical extraction of antioxidants, pharmaceuticals, colouring matters, and pesticides has also been studied. The separation of liquid mixtures and the antisolvent extraction are other processes that can perform very interesting separations. Mathematical modelling has also been developed and refined for some of these processes.The objective of this review is to critically analyze traditional and new directions in the research on natural matter separation by supercritical fluids extraction and fractionation.
In the work described here the extraction processes of carotenoids and chlorophylls were analysed using two extraction techniques, namely ultrasound-assisted extraction and supercritical fluid extraction, and the results are compared. The solvents used for the ultrasound-assisted extraction were N,N'-dimethylformamide and methanol and for the supercritical fluid extraction, carbon dioxide. The raw material studied was Dunaliella salina, a microalgae characterized by the high levels of carotenoids present in its cellular structure. The results indicate that the supercritical fluid extraction process is comparable to the ultrasound-assisted extraction when methanol is used as solvent. In addition, the supercritical extraction process is more selective for the recovery of carotenoids than the conventional technique since it leads to higher values for the ratio carotenoids/chlorophylls. Finally, the effects of pressure and temperature on the extraction yields of the supercritical fluid extraction process were studied.