64
Z. Xiao et al.
a second-order polynomial model. The highest extraction yield of oil is 94.07% at
the condition of 133.59 °C, 32.03 min, 10.79 mL/g with the tea saponin yield of
71.38%, and the highest extraction of tea saponin is 74.21% with the oil yield of
91.27% of the total content at the condition of 121.11 °C, 32.07 min, 8.33 mL/g.
It is concluded that Camellia oil and tea saponin could be co-extracted with a good
yield at optimal conditions for camellia oil and tea saponin. The chemical profile of
the oils was determined by GC–MS. The fatty acid compositions were compared to
those obtained by the Soxhlet extraction (SE) method. The fatty acid profiles were of
no differences with those of the cold SE oils. FT-IR analysis indicates the similarity
of SCW oils and SE oils is 96.54%. This similarity indicates that subcritical water
also extracts the same FAs as those extracted by the conventional SE methodology.
Furthermore, it was determined that the oil extracted by SCW was even more resistant to lipid oxidation and more abundant valuable bioactive compounds than the
cold-pressed oils. It is proved that the SWE method is an alternative and greener
processing method for the simultaneous extract of oil and saponin from the Camellia
oleosa seeds.
2.6.1.1 Single-Factor Experimental Analysis
To study the effect of extraction conditions on the Camellia oil and the saponin yield,
the single-factor was first adopted. Effects of extraction temperature (°C), extraction
time (min), extraction pressure (MPa), and solvent/solid ratio (mL/g) on the extraction yield of oil and saponin are depicted in Fig. 2.4. A series of experiments were
performed under the conditions of extraction time of 30 min, pressure of 3 MPa,
solvent to material ratio of 10:1 (mL/g) in the presence of a nitrogen flow to evaluate
the effect of temperature on the yield of the oil and the saponin. The optimal temperature for the oil extraction and tea saponin is 125 °C, while the extraction ratio
at 100 °C (81.53%, 66.42%) and 140 °C (87.64%, 64.18%) were a little lower than
that of 120 °C (92.42%, 71.67%, Fig. 2.4a). As the temperature increased, the yield
of the saponin and oil were reduced. The increase of temperature could lead to the
degradation of the saponin and the oil, or the denaturation of starch and protein. The
deformed starch and protein would wrap and adsorb the oil in the cake, and hence
reduce the oil yield. Therefore, 125 °C was considered to be the optimum. The effect
of reaction time on the yield of oil and saponin was investigated under the condition
of temperature 125 °C, pressure 3 MPa, solvent to material ratio 10:1 (mL/g), and the
results are shown in Fig. 2.4b. The oil and saponin yield reached 93.24%, 73.28%
at 30 min, respectively. Furthermore, the yield of the oil slightly decreased when
the extraction time was increased from 30 to 60 min, the corresponding decrease in
saponin yield was from 73.28 to 59.31%, indicating that under the above experimental conditions, the saponin had the tendency to be hydrolyzed. Therefore, 30 min
was selected as the optimal extraction time. The influence of pressure and solvent
to material ratio on the yield of oils and saponin were investigated by varying the
pressure and solvent to materials ratio respectively and the results are displayed in
Fig. 2.4c, d, respectively. It was first observed the yield of both oils and saponin
Z. Xiao et al.
a second-order polynomial model. The highest extraction yield of oil is 94.07% at
the condition of 133.59 °C, 32.03 min, 10.79 mL/g with the tea saponin yield of
71.38%, and the highest extraction of tea saponin is 74.21% with the oil yield of
91.27% of the total content at the condition of 121.11 °C, 32.07 min, 8.33 mL/g.
It is concluded that Camellia oil and tea saponin could be co-extracted with a good
yield at optimal conditions for camellia oil and tea saponin. The chemical profile of
the oils was determined by GC–MS. The fatty acid compositions were compared to
those obtained by the Soxhlet extraction (SE) method. The fatty acid profiles were of
no differences with those of the cold SE oils. FT-IR analysis indicates the similarity
of SCW oils and SE oils is 96.54%. This similarity indicates that subcritical water
also extracts the same FAs as those extracted by the conventional SE methodology.
Furthermore, it was determined that the oil extracted by SCW was even more resistant to lipid oxidation and more abundant valuable bioactive compounds than the
cold-pressed oils. It is proved that the SWE method is an alternative and greener
processing method for the simultaneous extract of oil and saponin from the Camellia
oleosa seeds.
2.6.1.1 Single-Factor Experimental Analysis
To study the effect of extraction conditions on the Camellia oil and the saponin yield,
the single-factor was first adopted. Effects of extraction temperature (°C), extraction
time (min), extraction pressure (MPa), and solvent/solid ratio (mL/g) on the extraction yield of oil and saponin are depicted in Fig. 2.4. A series of experiments were
performed under the conditions of extraction time of 30 min, pressure of 3 MPa,
solvent to material ratio of 10:1 (mL/g) in the presence of a nitrogen flow to evaluate
the effect of temperature on the yield of the oil and the saponin. The optimal temperature for the oil extraction and tea saponin is 125 °C, while the extraction ratio
at 100 °C (81.53%, 66.42%) and 140 °C (87.64%, 64.18%) were a little lower than
that of 120 °C (92.42%, 71.67%, Fig. 2.4a). As the temperature increased, the yield
of the saponin and oil were reduced. The increase of temperature could lead to the
degradation of the saponin and the oil, or the denaturation of starch and protein. The
deformed starch and protein would wrap and adsorb the oil in the cake, and hence
reduce the oil yield. Therefore, 125 °C was considered to be the optimum. The effect
of reaction time on the yield of oil and saponin was investigated under the condition
of temperature 125 °C, pressure 3 MPa, solvent to material ratio 10:1 (mL/g), and the
results are shown in Fig. 2.4b. The oil and saponin yield reached 93.24%, 73.28%
at 30 min, respectively. Furthermore, the yield of the oil slightly decreased when
the extraction time was increased from 30 to 60 min, the corresponding decrease in
saponin yield was from 73.28 to 59.31%, indicating that under the above experimental conditions, the saponin had the tendency to be hydrolyzed. Therefore, 30 min
was selected as the optimal extraction time. The influence of pressure and solvent
to material ratio on the yield of oils and saponin were investigated by varying the
pressure and solvent to materials ratio respectively and the results are displayed in
Fig. 2.4c, d, respectively. It was first observed the yield of both oils and saponin