Study on extract yield of papaya leaf powder using a supercritical fluid extraction technique

Introduction

The superfluid extraction method is often used for extraction. Owing to the low density, high diffusivity and viscosity of supercritical carbon dioxide gas, the supercritical extraction method has become an alternative to conventional extraction methods such as the Soxhlet extraction method. Moreover, carbon dioxide has no side effects on the environment because it is nonflammable and is a "green" gas, and the influence of pressure on the solubility of desired compounds may increase the extraction efficiency. When the pressure and temperature are optimized, carbon dioxide may be preferable. There is no chance of mixing carbon dioxide in the final product received from supercritical sources, as carbon dioxide can be removed by depressurizing during the collection of extracts (Katarzyna, et al., 2018) [3] . When a fluid (most often carbon dioxide) is subjected to a desirable combination of pressure and temperature, it can possess critical properties for the selective extraction of fat. Under controlled conditions of time, temperature, and pressure, the sample is exposed to supercritical fluid to allow dissolution of the fat from the sample in a supercritical fluid extraction system. The dissolved fat is then separated from the supercritical solvent by a significant drop in solution pressure (Saneha, et al.,2009) [8] . Supercritical fluids have been used as solvents for a wide variety of applications, such as essential oil extraction, metal cation extraction, polymer synthesis and particle nucleation. Most analytical supercritical extraction systems are used for the extraction of fat or compounds, with carbon dioxide having several benefits. Carbon dioxide is relatively inexpensive, highly pure, nontoxic and nonflammable. Carbon dioxide can be removed easily from the extract, which is best for lipophilic compounds. It has a relatively low critical pressure and temperature. (Pourmortazavi and Hajimirsadeghi, 2007) [6] Materials & Methods A sample of papaya leaves was prepared. This powder was obtained from papaya leaves that had been tray-dried at 50 °C. The objective of the experiment was to achieve a high yield of extraction using the supercritical fluid extraction system.

Supercritical fluid extraction technique

The supercritical fluid extraction assembly (Make: Applied Separations, USA) (Plate 3.9) has five components: a reciprocating compressor, a CO 2 cylinder, a CO 2 pump, an oven module and a chiller. Compressed air is necessary to drive the CO 2 pump, for which a reciprocating compressor (make: Anest Iwata, Noida) was used. It was provided with a 3-phase squirrel cage induction motor of 4 HPs with a rpm of 1424. The capacity of the reciprocating compressor is 180 L. The CO 2 cylinder (46.7 liter capacity) was connected to a CO 2 pump. This pump is used to pressurize CO 2 at the required pressure with a maximum limit of 690 bar. From the pump, pressurized CO 2 enters the oven module. The SFE oven module (Plate 3.21) consists of a rectangular chamber in which the sample holding vessel is fixed at the required temperature. In the oven, two sample holding vessels can be fixed at a time. The oven temperature, micrometering valve temperature, vessel temperature and set temperature are displayed in the bottom panel of the oven module. The CO 2 inlet valve and vent valve are located at the left sidewall of the oven, and the CO 2 outlet valve and micrometering valve are located at the right sidewall of the oven. The inlet valves are shut-off valves that supply supercritical CO 2 from the pump module to the extractor vessels, whereas the outlet valves are shut-off valves that supply supercritical CO 2 from the extraction vessel to the metering valves. The vent valves are used to vent the supercritical CO 2 from the extractor vessels to the atmosphere. The micrometer valves are flow control valves used to release supercritical CO 2 to the atmosphere. A thermocouple is placed inside the oven module to measure the temperature of the vessel. The extract is collected in a glass vial, which is fixed below the micrometering valve. A chiller is used for the recirculating coolant and is connected to the pump module. A recirculating coolant is required by the pump module for CO 2 pressurization. The recirculating coolant should be maintained at a controlled temperature of 0 °C or less. A mixture of ethylene glycol and water is used as a cooling medium.

Results & discussion

Supercritical extraction Effect of supercritical fluid extraction parameters on extract yield

Experiments on the supercritical fluid extraction of papaya leaf powder were conducted. The extraction yield was analyzed from the extracted yield of the papaya leaves. The optimized combination of temperature, pressure, dynamic time and particle size was selected on the basis of the maximum yield recovery. The yield content was influenced by temperature, pressure, dynamic time and particle size. The yield of the papaya leaf powder (%) varied from 0.12 to 6.27%. The maximum yield was obtained at 40 °C and 250 bar pressure, and the minimum yield was obtained at 70 °C and 100 bar pressure. An analysis of variance was conducted on the experimental data, and the effects of temperature, pressure, dynamic time and particle size, as well as their interactions with yield, phenol, flavonoid and antioxidant activity, were estimated. The quadratic model was fitted to the experimental data, and the statistical significance of the linear, quadratic and interaction effects was calculated for each response (Table 1). The Model F value of 15.42 implies that the model is significant in the case of yield. There is only a 0.01% chance that an F value that is this large could occur due to noise. P values less than 0.0500 indicate that the model terms are significant. In this case, A, B, C, AD, BC, A², and B² are significant model terms. Values greater than 0.1000 indicate that the model terms are not significant. If there are many insignificant model terms, model reduction may improve the model. The lack of fit F value of 3.75 implies that there is a 7.86% chance that a lack of fit F value could occur due to noise. The predicted R² of 0.7155 is in reasonable agreement with the adjusted R² of 0.8744; i.e., the difference is less than 0.2. Adeq Precision measures the signal-to-noise ratio. A ratio greater than 4 is desirable. In the present study, a ratio of 14.232 indicates an adequate signal. This model can be used to navigate the design space.

Effects of temperature and pressure on yield

The effects of temperature and pressure on the extract yield are shown in Fig. 2. The influence of pressure was more prominent than that of temperature. When the pressure increased, the extraction yield increased. At a constant temperature, an increase in pressure increases the density of SC-CO 2 . The solvent strength of SC-CO 2 increases with increasing density of CO 2 . As the density increases, the distance between the molecules decreases; therefore, the interaction between the analyte and CO 2 increases, leading to greater solubility of the analyte in CO 2 (De Castro et al., 1994) [2] . An increase in pressure also accelerates the mass transfer of analytes and solvents in supercritical extractor vessels and improves the extraction yield (De Castro et al., 1994) [2] . At higher pressures of 175 and 250 bar and lower temperatures of 40 and 55 °C, the extract obtained was viscous, waxy, dark green and yellow in color. Reverchon (1992) [7] reported that it is not simple to investigate extraction from herbaceous substrates because they contain many families of lipophilic solutes that have a high affinity for supercritical CO 2 . In addition, other extractable compounds, such as fatty acids, vegetable wax, coloring matter, and resinoids, are also present. Therefore, it can be presumed that the waxy extract obtained was due to the presence of hydrocarbon compounds. When the pressure was reduced and the temperature increased, the extract was less viscous, and the color was yellow. The graph clearly shows that as the pressure increased, the yield of the extract also increased with increasing temperature. Minimum extract of 0. 12% was obtained at 70 °C, 100 bar for a dynamic time of 30 min and a 0.5 mm particle size. 2015) [1] and Katarzyna et al. (2018) [3] .

Effects of temperature and time on yield

The influences of temperature and dynamic time on yield are shown in the figure . The RSM graph reveals that with increasing time, the yield (%) increased. The graph also indicates that at different temperatures, the yield varies. There was no specific trend observed for the temperature.

Compared with relatively high temperatures, moderate temperatures resulted in greater extract yields. The temperature at constant pressure and the same particle size had no major effect on the yield. An extract of 1.68% was obtained at 70 °C, 250 bar for a dynamic time of 30 min and a 0.5 mm particle size, whereas an extract yield of 5.35%

was obtained at 70 °C, 250 bar for 120 min and a 0.5 particle size. This finding revealed that at the same temperature and different times, the yield was different. These results are also in accordance with those of Sardar et al. (2018) [9] , who worked on supercritical fluid extraction from ajwain seeds. From this figure, it can be concluded that when the yield was changed at different temperatures, a particular particle size was used. For example, at 40 °C, with a 0.5 mm particle size at constant pressure and time, the yield was 2.12%, whereas it was 0.112% at 70 °C and 0.5 mm in size. At a particular temperature, the yield also changed with different particle sizes at the same pressure and time, i.e., at 55 °C, the yield varied from 2.75 and 1.71% at 0.5 and 2 mm, respectively. The temperature index was controlled at approximately 55 °C for a relatively high yield. The findings of this study are similar to those of Nehul (2015) [5] . [4] are quite similar to the present observations.

Effects of pressure and particle size on yield

An increase in the extraction yield of papaya leaves was recorded with increasing pressure, whereas there was no significant decrease in the extraction yield of papaya leaves with increasing particle size. This finding cannot be attributed to the fact that, owing to an increase in particle size, less surface area is available for extraction; therefore, the yield was greater, but the effect remained almost the same. Pressure is the main factor affecting the extraction of papaya leaf extracts. The effects of pressure and particle size on the extraction yield of papaya leaves are shown in Fig. 6.

Pressure had a dominant effect on the extraction yield, as reported by Liza et al. (2010) [4] .

Effect of time and particle size on yield

The effects of dynamic time and particle size on the percent extraction yield of papaya leaves are shown in Figure 7. The extraction yield increased with increasing dynamic time.

However, the extraction yield had no effect on the particle size. Similar trends in the yields of the extracts of papaya leaves were found for different particle sizes. The effects of dynamic time and particle size on the percent extraction yield of papaya leaves are shown in Figure 7. The extraction yield increased with increasing dynamic time.

However, the extraction yield had no effect on the particle size. Similar trends in the yields of the extracts of papaya leaves were found for different particle sizes.

References

1. Bermejo DV, Ibanez E, Reglero G, Turner C, Fornari T, Rodriguez-Meizoso I. High catechins/low caffeine powder from green tea leaves by pressurized liquid extraction and supercritical antisolvent precipitation. J Sep Purif Technol. 2015;148:49-56.
2. Katarzyna T, Marcin K, Edward R. The application of supercritical fluid extraction in phenolic compound isolation from natural plant studies. Molecules. 2018;23(1):1-27.