| The dense carbon dioxide extraction from black pepper has been described in the literature several times. A semi-continuous arrangement with solvent flowing through a fixed bed of ground pepper with constant rate was used in all cases. Usually, a yellowish semi-solid mass with a crystalline fraction is obtained.
The apparatus used in the research are showed in following figures.
Figure 46. Complete System Setup for SFE Study
Figure 47. Complete setup of BUCHI Extraction System
Figure 48 inferred that the grinding play a pivotal role to increase the oil yield extracted from black pepper by using SFE technique. When the size decreasing from whole seed to 0.5mm, amount of pepper oil obtained increase tremendously from 2.9% to almost 7.5%. Another important phenomenon can be observed in which, less amount of liquid carbon dioxide was being consume to gain the same level of oil yield.
For getting a better idea on how black pepper size affects the extraction yield, a comparison between this works with previous experimental results is show in Figure 49. All these works were conducted at the same temperature level, but varies in working pressure.
Same conclusion can be drawn like previous finding in which the reduction of particle size tend to increase both the extraction rate and yield. However, it should be bear in mind that the higher extraction rate work was not purely due to the decrease of pepper size. A higher pressure employed should contribute to this observation as well.
Figure 48. Extraction curve for black pepper oil undergo SFE at 200bar, 40°C with 0.8406g/min of CO 2
Figure 49. Comparison of extraction curve for black pepper oil between this study with previous works under different SFE working condition.
17. 2. 1. Empirical Model
The simple empirical equation proposed has been used to describe the experimental data from this study. They represented the extraction yield (Y) against the extraction time (t) in terms of a Langmuir-like-empirical equation:
 (1)
in which, Y is the specific amount of solute (g extract/g solute-free feed), Y ∞ is the maximum yield after an infinite extraction, t is the extraction time, and Y ∞/B is the initial slope of the specific oil yield as a function of time.
Value of B in equation (1) can be determined through linearization of that equation into general linear equation form, Y=mX + C, by simply inverse the mentioned equation:
 (2)
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