Supercritical extraction and fractionation of natural matter is one of the early and most studied applications in the field of supercritical fluids In the last 10 years, studies on the extraction of classical compounds like essential and seed oils from various sources: seeds, fruits, leaves, flowers, rhizomes, etc, with or without the addition of a co-solvent have been published Supercritical extraction of antioxidants, pharmaceuticals, colouring matters, and pesticides has also been studied The separation of liquid mixtures and the antisolvent extraction are other processes that can perform very interesting separations Mathematical modelling has also been developed and refined for some of these processes The objective of this review is to critically analyze traditional and new directions in the research on natural matter separation by supercritical fluids extraction and fractionation

Supercritical fluid extraction and fractionation of natural matter

The influence of the height of the particle bed on the kinetics of supercritical fluid extraction (SFE) of essential oil from orange peel is analyzed in this article. Peel of dehydrated oranges of the satsuma and naveline cultivars was used. A series of experiments were designed wherein, for the same conditions, particle height varied widely. These experiments were also carried out on different scales with extraction volumes of 0.5 and 5 l. The results of the experiments were interpreted using Sovova's extended flow model as has been done in previous studies. The bibliography indicates that a number of phenomena may distort the process. One of these phenomena is the formation of masses of particles, due to their oil content, which increases resistance to mass transfer inside the particle. However, this phenomenon was barely noticeable in our experiments. Also, some reordering of the particles may take place due to the differing densities of the two phases and a certain drag effect exercised on the particles by the fluid. This situation can cause a lack of homogeneity in the fluid, further reducing the effectiveness of the process. In the experiments with the satsuma cultivar, where the bed-height range was broader, a base of diatomaceous earth was added in the extractor in order to reduce the lack of homogeneity in the fluid flow. Very similar behavior was found in all the experiments and we can, therefore, conclude that where there is homogeneous flow the height of the bed has very little effect, at least on the same scale of operation.

Supercritical CO2 extraction of essential oil from orange peel; effect of the height of the bed

In this work supercritical deterpenation of orange peel oil with carbon dioxide is studied. Optimal schemes and operating conditions are determined through the formulation of a nonlinear programming model that includes reliable thermodynamic predictions with a group contribution equation of state and rigorous unit models. A detailed comparison of binary and ternary equilibrium predictions with available experimental data is reported. Simulation results are in agreement with previous laboratory-scale separation values. Different solvent cycle schemes have been included in the mathematical model. Net profit is maximized taking into account capital and operating costs associated to the complete deterpenation process. Numerical results show that a compression cycle is the optimal solvent recovery system in all cases. Furthermore, optimal operating conditions have been determined in main units (extractor and separator), for the production of both a five-fold concentrate and a high purity aroma, as raffinate, respectively.

Citrus peel oil deterpenation with supercritical fluids: Optimal process and solvent cycle design

In the first part of this contribution, an overview is given of some of the main developments in food process engineering in the last 25 years of the 20th century. This overview is, of course, colored by the personal experience of the authors, but a sincere effort was made to maintain a general perspective. Topics that will be briefly discussed are: progress in understanding how to control food microstructure formation during processing, separation processes, conversion processes and stabilization processes, progress in flavor technology and understanding of flavor retention during processing and release. In the 2nd part, in our view, the most exiting future developments are briefly discussed. The major items here are: processing requirements for functional foods, integrated process design approaches, application of novel‘fields’in food processes,‘precision’processing, supply chain approaches to food manufacturing, and more.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1541-4337.2003.tb00015.x

Food Process Engineering: The Last 25 Years and Challenges Ahead

Development and state of the art of counter-current separation, in particular for liquids, with supercritical fluids, is reviewed, covering principles, early development, actual and possible applications, and counter-current separation as published in the Journal of Supercritical Fluids. A description of processes (continuous counter-current flow, mixer-settler principle, the role of co-solvents), necessary fundamentals, design procedure (including gas cycles), a summary of the methodical knowledge, and cost calculation are covered. A discussion and a comparison to competitive processes and an outlook on future perspectives conclude the review.

Counter-current separations

The separation of terpene hydrocarbons from oxygenated aroma components was investigated by using supercritical carbon dioxide to fractionate orange peel oil. To understand the behavior of this multicomponent system, phase equilibrium measurements, countercurrent column experiments and flooding-point measurements were carried out. Conditions were set within a temperature range from 323 to 343 K and pressures from around 8 MPa up to 13 MPa. Separation factors for the two groups of oil components, `terpenes' and `aroma', were obtained for the system CO2+orange peel oil depending on temperature and pressure. Moreover, fractionated products from countercurrent experiments were used to study the influence of product composition on both selectivity and mutual solubility. A stage calculation method based on the Janecke diagram was applied to evaluate VLE data. Due to the fact that the operating costs of a continuous process depend on the solvent-to-feed ratio, this parameter was used to determine the optimal conditions for multistage extraction. For a given separation task at a fixed temperature, the required solvent-to-feed ratio was found to decrease with increasing pressure. This is explained by the increase in loading of the solvent and the possibility of enhancing the extract reflux which predominates the effect of decreasing separation factors at a higher loading. After passing a minimum, the required solvent-to-feed ratio increases near the critical point of the mixture.

S. Heilig

Papers

Countercurrent deterpenation of citrus oils with supercritical CO2