J. of Supercritical Fluids 54 (2010) 22–29 Contents lists available at ScienceDirect The Journal of Supercritical Fluids journal homepage: www.elsevier.com/locate/supflu Supercritical fluid fractionation of liquid oleoresin capsicum: Statistical analysis and solubility parameters M.P. Fernández-Ronco, C. Ortega-Noblejas, I. Gracia, A. De Lucas, M.T. García, J.F. Rodríguez ∗ Departamento de Ingeniería Química, Facultad de C.C. Químicas, Universidad de Castilla-La Mancha, Avda. Camilo José Cela 12, 13071 Ciudad Real, Spain article info Article history: Received 11 January 2010 Received in revised form 26 March 2010 Accepted 27 March 2010 Keywords: Carbon dioxide Capsicum Factorial design Solubility Supercritical extraction abstract Supercritical fluid extraction (SFE) of liquid oleoresins (Capsicum annuum L. and Capsicum frutescens L.) was carried out in order to improve properties of oleoresins obtained by traditional processes using organic solvents. SFE allowed us to fractionate the different compounds present in oleoresins recovering both, an extract and a raffinate which can fulfill trader’s needs. The aim of this work was to study the effect of pressure (140–300 bar) and temperature (313–333 K) affecting the yield and the commercial value of oleoresins extracts and raffinates, expressed in terms of parameters such as colour (SCU), pungency (SHU) and carotenoids and capsaicinoids concentration. A set of previous experiments was carried out to select the most suitable type of oleoresin and the initial ratio CO 2 /oleoresin which assures initial conditions in the biphasic area of CO 2 /oleoresin diagram to produce fractionation. A response surface methodology (RSM) was used to evaluate the effect of the factors over the variables and different linear correlations were proposed and validated to describe the responses studied. 300 bar and 333 K were selected as the best operational conditions to obtain fractionation. Finally, solubility parameters were obtained and correlated with semi-empirical models in order to obtain correlations which will be useful in subsequent stages of scaling-up. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Nowadays, the interest of natural additives such as carotenoid and capsaicinoid pigments is increasing due to the restrictive regulations in food, cosmetic and pharmaceutical industries. Red peppers have been used as a source of pigments in both forms: paprika powder and oleoresin. Oleoresin is obtained by solvent extraction of natural strains of paprika powder and contains the major colouring principles of this spice [1]. It can also contain pun- gency when capsaicinoid compounds are present. There are three main types of oleoresins prepared from the dried fruits of capsicum species [2]. Table 1 shows the main types and their characteristics. The quality of oleoresins, and therefore their commercial value, increases with their colouring capacity [3,4], which is caused by carotenoid pigments, essentially capsanthin and capsorubin [5,6]. Moreover, the pungency of an oleoresin, which is caused by cap- saicinoid pigments, is another quality factor to take into account because of the wide range of medical applications that these com- pounds present [7]. Therefore, industrial oleoresins overall quality is expressed in terms of colour units: ASTA, SCU and Tint value ∗ Corresponding author. Tel.: +34 926295300x6345; fax: +34 926295256. E-mail address: Juan.RRomero@uclm.es (J.F. Rodríguez). parameters, and in terms of pungency units: Scoville Heat Units (SHU). Although the traditional method to produce oleoresins is based on the extraction of paprika powder with organic solvents, spe- cially n-hexane [8], the problems associated to the use of organic solvents in addition to the inability of this procedure to obtain an oleoresin with the desired characteristics, which depend exclu- sively on the variety of paprika powder, increases the interest for the development of an alternative production process. Supercritical fluid extraction of the oleoresin obtained after the traditional process seems an interesting alternative to mod- ify the properties of the oleoresin in the way that trader needs. Furthermore, the fractionation of pigments present in oleoresin (carotenoids and capsaicinoids) could produce extracts and raffi- nates enriched in those compounds which can be sold for different applications improving their initial commercial value and solving some problems associated to the pollination of peppers occurs in many plantations of India. Despite some previous researches [1,9–11] based exclusively on the application of SFE to paprika powder in order to produce liq- uid oleoresin without using organic solvents, the results obtained were not enough to determine the economical feasibility of this technique compared to the traditional process. In addition, no infor- mation about the extract quality expressed in terms of parameters such as SCU or SHU used to determine the industrial quality of oleoresins is showed in previous researches. 0896-8446/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.supflu.2010.03.011