1. Introduction

Separation technologies with fluids at high pressures are essentially vital to get new natural products of vegetable or marine origin that have biological activity, so-called bioactive extracts. Among the developed technologies, the supercritical fluid technology offers products free of residual solvent and that typically present high quality, when compared to products obtained by conventional techniques. The extracts of bioactive compounds can be obtained by extraction

© The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

distribution, and eproduction in any medium, provided the original work is properly cited.

of solid matrices (leaves, seeds, pulps, etc.) or by extraction/fractionation of liquid mixtures (aqueous solutions, fish oils, microalgae oils, vegetable oil, deodorize distillates, etc.) [1–5]. In processes at high pressures, which are near or above the critical point (pressure and temperature), the solvent density increases drastically and this is the most important parameter associated to the solvent power. As illustrated in Figure 1, carbon dioxide, a non-toxic substance, acting as solvent, co-solvent, or anti-solvent, is the most important fluid used in the supercritical fluid technology in extraction, separation, fractionation, micronization, and encapsulation processes applied to obtain extracts concentrated with bioactive compounds for food, pharmaceutical, and cosmetic applications [6–9].

involved in various processes. The cubic equations of state are the most commonly applied models for the correlation and prediction of phase equilibrium at high pressures and are available in major commercial process simulators. In addition, they are used to calculate other thermodynamic properties, for both pure substances and mixtures, among which, the liquid

Carbon Dioxide Use in High-Pressure Extraction Processes

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This chapter intends to show the recent application scenarios of the carbon dioxide use at high pressures as solvent, to obtain natural extracts enriched with bioactive compounds, including the use of water as co-solvent to enhance the mixture solvating power. In this chapter, the description of the experimental strategy used for the supercritical carbon dioxide extraction of bioactive compounds from açaí berry pulp was emphasized. The primary properties of pure

The pressure versus temperature (P-T) diagram describes the different aggregation states of

Figure 2 is a schematic representation of the P-T diagrams for carbon dioxide and the substances most commonly employed as co-solvent, ethanol, and water, in high-pressure extraction processes

Figure 2. Solid-liquid-gas-supercritical fluid phase diagram. TP = triple point. CP = critical point. Pc = critical pressure.

Tc = critical temperature. Tt = triple point temperature. Pt = triple point pressure.

carbon dioxide were also described and calculated using equations of state.

and vapor phases density, enthalpy, and entropy.

2. Diagrams of pure substances

pure substances called solid, liquid, and vapor/gas.

2.1. P-T diagram

Carbon dioxide has a critical temperature near to room temperature, contributing to the operating conditions (pressure and temperature) to extract thermolabile substances, such as bioactive compounds. In addition, this substance is non-polar and to enlarge the application spectrum to extract bioactive compounds, ethanol, water, or both are usually used as cosolvents. Moreover, carbon dioxide acts as co-solvent when in the mixture it is used more than 60% of ethanol or water, and as anti-solvent, when the solute extract is not soluble in carbon dioxide during the depressurizing step.

The information accuracy related to the physical (pressure, temperature, and density) and transport properties (diffusivity, viscosity) and the accuracy of thermodynamic and mass transfer relations used for the solvent, co-solvent, and solute reach directly the costs of investment in extraction/separation units in supercritical conditions. The thermodynamic phase equilibrium determines the limits for the mass transfer among different phases, which are

Figure 1. Carbon dioxide applications.

involved in various processes. The cubic equations of state are the most commonly applied models for the correlation and prediction of phase equilibrium at high pressures and are available in major commercial process simulators. In addition, they are used to calculate other thermodynamic properties, for both pure substances and mixtures, among which, the liquid and vapor phases density, enthalpy, and entropy.

This chapter intends to show the recent application scenarios of the carbon dioxide use at high pressures as solvent, to obtain natural extracts enriched with bioactive compounds, including the use of water as co-solvent to enhance the mixture solvating power. In this chapter, the description of the experimental strategy used for the supercritical carbon dioxide extraction of bioactive compounds from açaí berry pulp was emphasized. The primary properties of pure carbon dioxide were also described and calculated using equations of state.
