It is a presentation about the application of Supercritical Gas Extration techniques in the food processing engineering.

1. SAM HIGGINBOTTOM INSTITUTE OF AGRICULTURE,
TECHNOLOGY AND SCIENCE
FOOD PROCESSING ENGINEERING DEPARTMENT
Paper presentation by
KAMILU ABUBAKAR MAIGALURA
13MTAEPF019
and
MUSTAPHA MUHAMMAD NASIRU
13MTAEPF018
APFE 806: ADVANCED FOOD TECHNOLOGY

2. SUPERCRITICAL GAS
EXTRACTION

3. Introduction
 Discovery of supercritical fluids (SCF)
 Supercritical fluid extraction (SFE)
 Supercritical fluid chromatography (SFC)
 Column chromatography (CC)
 Gas chromatography (GC)
 High-performance liquid chromatography
(HPLC).

4. Cont. (Introduction)
The technology of (SCFS) and (SFE)
 Improve recovery
 Increase reproducibility
 Decrease the use of halogenated solvents
 Fast
 Efficiency
 Quantitative and free of contamination

5. Historical Background of Supercritical Fluids
The first reporter was Baron Cagniad de la Tour in 1822.
Hany and Hogarth in 1979. studied the solubilities of
Cobalt (II) Chloride, Potassium Bromide, and Potassium
iodide in supercritical ethanol Tc = 243 oC, Pc = 63 atm).
They found that the concentrations of the metal chlorides
in supercritical ethanol were much higher than their vapour
pressures. They also found that increasing the pressure
caused solutes to dissolve and decreasing the pressure
caused the dissolved materials precipitate as “snow”.

6. Cont. (Historical background)
In 1936 Wilson, Keith and Haylett devised a propane
deasphalting process for refining lubricating oils.
Solexol process was developed for the purification and
separation of vegetable and fish oils.
Zosel patent In 1970, reported the decaffeination of
green coffee with CO2. This process was accomplished by
soaking the beans in water and then immersing them in
supercritical CO2. The presence of water was essential for
efficient extraction of the caffeine from the bean.

7. Cont. (Historical background)
Since 1980, there has been rapid development of supercritical fluid
extraction of:
Hops (Hubert and Vitzthum 1980)
Cholesterol from butter (Krukonis 1988)
Perfumes and flavours from natural products (Adasoglu et al 1983)
Residual solvents and monomers from polymers (Krukonis 1985)
Unsaturated fatty acids from fish oils (Krukonis 1988).
SCF technology has become an interdisciplinary field shared by chemical
engineer, chemists, food scientists, agronomists, biotechnology and environmental
control and in many areas.

8. Definition
A supercritical fluid is the phase of a material at critical temperature and critical
pressure of a material.
Critical temperature is the temperature at which a gas cannot become liquid as
long as there is no extra pressure.
Critical pressure is the minimum amount of pressure to liquefy a gas at its
critical temperature.
Supercritical fluids combine useful properties of gas and liquid phases.
it takes the shape of the container.
The motions of the molecules are quite similar to gas molecules.

9. In order to understand the definition of SF better, a simple phase diagram can be
used. The figure below displays an ideal phase diagram.

10. 1. Here we can see the separate phases of carbon dioxide.
The meniscus is easily observed.
2. With an increase in temperature the meniscus begins to
diminish.
3. Increasing the temperature further causes the gas and
liquid densities to become more similar. The meniscus is
less easily observed but still exists.
4. Once the critical temperature and pressure have been
reached, the two distinct phases of liquid and gas are no
longer visible. The meniscus can no longer be seen. One
homogenous phase called the "supercritical fluid" phase
occurs.
1
2
3
4
Tc Pc

11. Properties of Supercritical Fluids
Supercritical Fluid shares some common properties with both gases and
liquids. These properties are:
Density
Viscosity
Diffusivity
Table 1: Order of density, viscosity and diffusivity of gases, liquids and supercritical
fluids.
Properties Liquid Supercritical fluid Gas
Density (kg/m3) 1 000 200 – 800
1
Viscosity (mPas) 0.5 –1.0 0.05 – 0.1
0.01
Diffusivity (cm2/s) 10-5 10-4 – 10-3 0.1

12. Table 2: Critical points for typical solvents
Solvent Tc (oC) Pc (Bar) ρc (g/ml)
Ammonia 132.5 113.5 0.24
Benzene 289.0 48.9 0.30
n-Butane 152.0 38.0 0.23
Carbon dioxide 31.1 73.8 0.45
Chlorotrifluoromethane 28.8 39.5 0.58
Dichlorodifluoromethane I 11.7 39.9 0.56
Ethane 32.2 48.9 0.20
Ethanol 243.4 63.8 0.28
Ethylene 9.3 50.4 0.22
Isopropanol 235.3 47.6 0.27
Methanol 240.5 79.9 0.27
Nitrous oxide 36.5 72.3 0.46
n-Propane 96.8 42.6 0.22
Propylene 91.9 46.2 0.23
Toluene 318.6 41.1 0.29
Water 374.2 221.2 0.34

13. Advantages of working with SFC
The physical properties of supercritical fluids between liquids and gases enable
the SFC technique to combine with the best aspects of HPLC and GC, as lower
viscosity of supercritical fluids makes SFC a faster method than HPLC. Lower
viscosity leads to high flow speed for the mobile phase.
Thanks to the critical pressure of supercritical fluids, some fragile materials that
are sensitive to high temperature can be analyzed through SFC.
High pressure conditions provide a chance to work with lower temperature than
normally needed. Hence, the temperature-sensitive components can be analyzed
via SFC.
In addition, the diffusion of the components flowing through a supercritical fluid
is higher than observed in HPLC due to the higher diffusivity of supercritical
fluids over traditional liquids mobile phases. This results in better distribution into
the mobile phase and better separation.

14. Applications of SFC
The applications of SFC range from food to environmental to pharmaceutical
industries. In this manner, pesticides, herbicides, polymers, explosives and fossil
fuels are all classes of compounds that can be analyzed. SFC can be used to
analyze a wide variety of drug compounds such as antibiotics, prostaglandins,
steroids, taxol, vitamins, barbiturates, non-steroidal anti-inflammatory agents, etc.
Chiral separations can be performed for many pharmaceutical compounds. SFC is
dominantly used for non-polar compounds because of the low efficiency of
carbon dioxide, which is the most common supercritical fluid mobile phase, for
dissolving polar solutes. SFC is used in the petroleum industry for the
determination of total aromatic content analysis as well as other hydrocarbon
separations.

15. Application of SFC in Food Processing
Food processing is the most widely investigated industrial application of
supercritical fluid technology. Carbon dioxide is a particularly suitable solvent for
food processing applications, because its moderate critical temperature (Tc = 31.1
°C), and critical pressure (Pc = 73.8 bar) enables the extraction of thermally labile
food compounds. Additionally, it is non-toxic, odourless, environmentally
acceptable (does not damage the ozone layer, and does not produce smoke), and
relatively inexpensive, and does not have photochemical reaction. Compared with
conventional solvents such as hexane, carbon dioxide does not leave any harmful
solvent residue after extraction. The food material to be extracted is often solid, and
therefore semi-batch extraction is frequently used. A schematic picture of a semi-
batch supercritical fluid extraction system is presented in Figure 2.

16. Figure 2: Operating principle of a semi-batch supercritical fluid extraction system.

17. Extraction of supercritical fluids
The unique physical properties of supercritical fluids, having values for density,
diffusivity and viscosity values between liquids and gases, enables supercritical
fluid extraction to be used for the extraction processes which cannot be done by
liquids due to their high density and low diffusivity and by gases due to their
inadequate density in order to extract and carry the components out.
Complicated mixtures containing many components should be subject to an
extraction process before they are separated via chromatography. An ideal
extraction procedure should be fast, simple, and inexpensive. In addition,
sample loss or decomposition should not be experienced at the end of the
extraction. Following extraction, there should be a quantitative collection of
each component.

18. The higher diffusivity and lower viscosity of supercritical fluids, as compared to
regular extraction liquids, help the components to be extracted faster than other
techniques. Thus, an extraction process can take just 10-60 minutes with SFE,
while it would take hours or even days with classical methods. The dissolving
efficiency of a supercritical fluid can be altered by temperature and pressure. In
contrast, liquids are not affected by temperature and pressure changes as much.
Therefore, SFE has the potential to be optimized to provide a better dissolving
capacity. In classical methods, heating is required to get rid of the extraction liquid.
However, this step causes the temperature-sensitive materials to decompose. For
SFE, when the critical pressure is removed, a supercritical fluid transforms to gas
phase. Because supercritical fluid solvents are chemically inert, harmless and
inexpensive; they can be released to atmosphere without leaving any waste.
Through this, extracted components can be obtained much more easily and sample
loss is minimized.
Cont. (Extraction of SCF)

19. Instrumentation for SFE
The necessary apparatus for a SFE setup is simple. Figure 3 depicts the basic
elements of a SFE instrument, which is composed of a reservoir of supercritical
fluid, a pressure tuning injection unit, two pumps (to take the components in the
mobile phase in and to send them out of the extraction cell), and a collection
chamber.
Figure 3: Scheme of an idealized supercritical fluid extraction instrument.

20. There are two principle modes to run the instrument:
Static extraction.
Dynamic extraction.
In dynamic extraction, the second pump sending the materials out to the
collection chamber is always open during the extraction process. Thus, the
mobile phase reaches the extraction cell and extracts components in order to take
them out consistently.
In the static extraction experiment, there are two distinct steps in the process:
Step 1. The mobile phase fills the extraction cell and interacts with the sample.
Step 2. The second pump is opened and the extracted substances are taken out at
once.

21. Extraction modes
Off-line extraction.
On-line extraction.
Off-line extraction is done by taking the mobile phase out with the extracted
components and directing them towards the collection chamber. At this point,
supercritical fluid phase is evaporated and released to atmosphere and the
components are captured in a solution or a convenient adsorption surface. Then
the extracted fragments are processed and prepared for a separation method. This
extra manipulation step between extractor and chromatography instrument can
cause errors.

22. Cont. (Extraction methods)
The on-line method is more sensitive because it directly transfers all extracted
materials to a separation unit, mostly a chromatography instrument, without
taking them out of the mobile phase. In this extraction/detection type, there is no
extra sample preparation after extraction for separation process. This minimizes
the errors coming from manipulation steps. Additionally, sample loss does not
occur and sensitivity increases.

23. Applications of SFE
SFE can be applied to a broad range of materials such as:
 Polymers,
 Oils and lipids,
 Carbohydrates,
 Pesticides,
 Organic pollutants,
 Volatile toxins,
 Polyaromatic hydrocarbons,
 Biomolecules,
 Foods,
 Flavours,
 Pharmaceutical metabolites,
 Explosives, and
 Organometallics, etc.

24. Cont. (Applications of SFE)
Common Industrial Applications include:
 The pharmaceutical and biochemical industry,
 The polymer industry,
 Industrial synthesis and extraction,
 Natural product chemistry, and
 the food industry.
Application in Food Analyses:
caffeine, peroxides, oils, acids, cholesterol, etc. are extracted from samples such as
coffee, olive oil, lemon, cereals, wheat, potatoes and dog feed.

25. Cont. (Applications of SFE)
Examples of Materials Analyzed in Environmental Applications:
Oils And Fats,
Pesticides,
Alkanes,
Organic Pollutants,
Volatile Toxins,
Herbicides,
Nicotine,
Phenanthrene,
Fatty Acids,
Aromatic Surfactants in samples from clay to petroleum waste, from soil to river
sediments.

26. Conclusion
The technology of supercritical fluid extraction (SFE) using supercritical
fluids (SCFs) is an alternative to conventional liquid extraction due to its use
of environmentally compatible fluids, oxygen free environment, shorter
extraction times, etc. Among SCFs, because of being mostly used due to its
many advantages, supercritical CO2 (SCCO2) is the reagent used to extract
plenty of materials. The special properties of SCFs bring certain advantages to
chemical separation techniques. Several applications have been fully
developed and commercialized. Some of them are food and flavouring,
pharmaceutical industry, environmental protection for volatile and lipid
soluble compounds, extraction of high-value oils, isolation of lipids soluble
compounds, extraction of high-value natural aromas, recovery of aromas from
fruits, meat, and fish, etc.