Chemistry Reference
In-Depth Information
is more attractive, capable of providing mild extraction conditions combined with
low energy requirements for solvent recovery. The high selectivity of the extraction
process and the reduced potential for oxidation of the extracted materials makes the
SFE technique highly suitable for the isolation of many of these natural carotenoid
pigments. As an example, pure β-carotene is obtained from tomato paste residue and
from microalgae using SFE. However, to maximize the separation efficiency and
minimize the degradation and loss, the conditions of pressure, temperature, SFE
rate, and the extraction time must be carefully controlled. Specifically, the optimal
temperature range for isolation is 40°C to 65°C. High pressure about 200 to 500
bar pressure is required to condense the supercritical CO
2
fluid as the flow rate is
maintained around 4 kg/h for 2 hours. Further, ethanol is added as the cosolvent,
increasing the yield by 10% to 15%.
Importantly, under conditions of 448 bar and 40°C, the SFE method allows for
the efficient separation of the Z/E isomers of β-carotene. The solubility of the 9Z
isomer is found to be 4 times higher than that of all the E isomers. Routine ana-
lytical analysis to detect β-carotene can be achieved using high-performance liquid
chromatography (HPLC) with ultraviolet-visible (UV-Vis) photodiode array (PDA)
detection. Best conditions require a short analysis time to minimize the isomeriza-
tion and decomposition of these sensitive carotenoids.
Reverse phase C
30
-HPLC with a PDA detector, set from 300 to 700 nm, can
be used to separate the carotenoid isomers.
For example, the carotenoids in man-
goes (
Mangifera indica
L.) are resolved and characterized quantitatively shown in
Figure 11.3. The numbered peaks are identified as follows: (1) all-
trans
β- carotene;
Ml
1
0.3
0.2
2
0.1
10
11
6
7
8
9
13
14
4
3
12
5
0.0
0
10
20
30
40
Time (min)
FIGURE 11.3
HPLC separation of carotenoids found in mangoes.
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