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  • ORIGINAL PAPER

    Evaluating the Effectiveness of β-Carotene Extraction from Pulsed Electric Field-Treated Carrot Pomace Using Oil-in-Water Microemulsion

    S. Roohinejad & I. Oey & D. W. Everett & B. E. Niven

    Received: 2 January 2014 /Accepted: 8 May 2014 /Published online: 18 May 2014 # Springer Science+Business Media New York 2014

    Abstract Thermodynamically stable microemulsions were used to extract β-carotene from pulsed electric field (PEF)- treated carrot pomace. In this study, a three-level Box– Behnken design was used to predict the effect of extraction time (10–110 min), extraction temperature (30–70 °C) and carrot/microemulsion ratio (1:30–1:90w/w) on the β-carotene content, polydispersity index (PDI) and particle size of the microemulsions. The β-carotene extracted from PEF-treated carrot pomace using microemulsions was higher than untreat- ed carrot pomace. The extraction efficiency of β-carotene using microemulsions was higher compared to 100 % hexane or 100 % glycerol monocaprylocaprate oil. A mathematical model was developed to predict the optimal extraction condi- tions using transparent microemulsions with high loading of β-carotene, low PDI and small microemulsion particle size. The model predicted that an extraction time of 49.4 min, temperature of 52.2 °C and carrot/microemulsion ratio of 1:70 (w/w) would result in microemulsions with β-carotene loading of 19.6 μg/g, PDI of 0.27 and particle size of 74 nm. This study demonstrates the potential of using oil-in-water microemulsions as extraction media for β-carotene.

    Keywords Microemulsion . Extraction . Polydispersity index . Particle size . Optimization .β-Carotene

    Introduction

    Interest in the replacement of synthetic pigments by natural colourants extracted from plant materials for making transparent beverages has been and is increasing in recent years due to high consumer demand for ‘more natural’ and healthy beverages (Cai et al. 2005; López et al. 2009). β-Carotene is the most abundant caroten- oid, which is found in high concentrations in many fresh fruits and vegetables, such as carrots. The impor- tance of β-carotene in food goes beyond their role as natural colourants; there are well-documented biological activities such as strengthening the immune system, decreasing the risk of cancer and reducing the risk of coronary heart diseases (Van Poppel and Goldbohm 1995; Kritchevsky 1999).

    The physical state and location of carotenoids in plants strongly affects their accessibility during diges- tion, which subsequently limits release and absorption. This can occur due to deposition of carotenoids in crystalline form in the chromoplasts, or carotene crys- tals being stabilized by other components (Reiter et al. 2003). Various techniques can be used to break down plant cell structure and improve the release of caroten- oids, such as mechanical homogenization and heat treatment (Hedrén et al. 2002); however, these tech- niques may promote reactions that cause the degrada- tion of carotenoids (Fratianni et al. 2010; Talcott and Howard 1999).

    Organic solvents are normally used to extract oil-soluble compounds from cellular structures after employing physical methods to improve extractability. Conventional carotenoid extraction methods require large amounts of organic solvents, which are costly, environmentally hazardous, and require expensive disposal procedures (Mustafa et al. 2012). Furthermore, the traditional extraction of carotenoids is no

    S. Roohinejad : I. Oey (*) :D. W. Everett Department of Food Science, University of Otago, PO Box 56, Dunedin 9054, New Zealand e-mail: indrawati.oey@otago.ac.nz

    D. W. Everett Riddet Institute, Private Bag 11 222, Palmerston North 4442, New Zealand

    B. E. Niven Centre for Application of Statistics and Mathematics, University of Otago, PO Box 56, Dunedin 9054, New Zealand

    Food Bioprocess Technol (2014) 7:3336–3348 DOI 10.1007/s11947-014-1334-6

  • longer recommended because of the risk of organic solvent residues and loss of carotenoids as a consequence of solvent evaporation (Illés et al. 1999). Recently, alternative non- thermal processing methods such as pulsed electric field (PEF) have emerged to improve the release of carotenoids through increasing the permeabilization of cells (Grimi et al. 2007; Roohinejad et al. 2014) without any significant effect on the stability of β-carotene or total carotenoid content (Sanchez-Moreno et al. 2005). Moreover, the use of inexpen- sive and efficient alternate extraction systems, such as microemulsions, might be suitable to replace the use of or- ganic solvents.

    Microemulsions are defined as a system formed by the dispersion of microdroplets of two immiscible liq- uids, stabilized by an interfacial membrane formed by surfactants. They are thermodynamically stable, homo- geneous and optically isotropic solutions with an aver- age droplet size less than 100 nm. These delivery sys- tems are of great technological and scientific interest because of their potential to incorporate a wide range of bioactives (hydrophilic and hydrophobic) due to the presence of both lipophilic and hydrophilic domains. These adaptable delivery systems provide protection against oxidation, enzymatic hydrolysis and improve the solubilization of lipophilic bioactives, hence enhance their bioavailability (Talegaonkar et al. 2008; Flanagan and Singh 2006).

    Previous studies reported on the ability of microemulsions to protect carotenoids against oxidation and increase solubili- zation (Arvanitoyannis 2009; Spernath et al. 2002). Moreover, microemulsions have attracted attention because of their ca- pability for selective extraction of biomolecules and metal ions in liquid–liquid systems (Cortez et al. 2004; Dantas et al. 2003) and DNA condensation (Budker et al. 2002); however, there are very few reports on the potential of microemulsions to extract food components from food com- plex mixtures (Paul and Moulik 2001). The utilization of microemulsified systems for β-carotene extraction might be a preferable alternative to conventional solvent extraction due to less hazardous solvents and lower energy consumption.

    This study was designed to (1) evaluate the effectiveness of oil-in-water (o/w) microemulsions as a potential alternative to replace the use of organic solvents for extracting β-carotene from carrot pomace and (2) optimize the process conditions (extraction time, temperature and ratio) on dependent re- sponses (β-carotene content, polydispersity index (PDI) and particle size) using a Box–Behnken design. The effect of PEF treatment on the extractability of β-carotene from carrot pom- ace using microemulsions was initially compared to non-PEF- treated carrot pomace. The optimized extraction conditions to obtain the maximum β-carotene content, minimum PDI and small particle size were determined. To our knowledge, this is the first study that has used microemulsions as an

    environmentally friendly mixture for extraction of β- carotene from plant materials for use in making transparent beverages.

    Materials and Methods

    Reagents

    Methyl t-butyl ether and Tween 80 (polyoxyethylene sorbitan monooleate) were purchased from Sigma-Aldrich (St. Louis, MO, USA) and n-hexane from J.T. Baker (Phillipsburg, NJ, USA). Glycerol monocaprylocaprate (Capmul MCM; CAS no. 26402-26-6) was kindly donated by Abitec Corporation (Janesville, WI, USA). The fatty acid composition of Capmul MCM consists of caprylic acid (C8), capric acid (C10) and lauric acid (C12) in the ratio of 97.3:2.6:0.1. Ethanol (95 %), methanol (HPLC-grade) and acetone were purchased from Biolab (Scoresby, Victoria, Australia). A β-carotene standard for HPLC analysis was purchased from CaroteNature (Lupsingen, Switzerland). All solvents used in this experiment were HPLC-grade, with the exception of ethanol.

    Preparation of Pulsed Electric Field-Treated Carrot Pomace

    Fresh carrots (Daucus carota cv. Nantes) harvested between June and July 2013 were purchased from a supplier of locally grown products (Kaan's Catering Supplies Ltd., Dunedin, New Zealand). Samples were washed, sliced and processed into a purée by mixing with distilled water (1:1 ratio). PEF treatment was carried out and compared with untreated sam- ples (control) of the corresponding batches. Carrot purée was treated using an ELRACK-HVP 5 PEF unit (Quakenbrück, Germany) in a batch treatment configuration. For each PEF treatment, carrot purée (100 g) was placed inside the PEF chamber of dimensions 80×100×50 mm with a sample ca- pacity of 400 mL, consisting of two stainless steel parallel plate electrodes with a gap of 80 mm. The treatment was applied according to the following optimum conditions: elec- tric field strength of 0.6 kV/cm with constant frequency of 5 Hz, pulse width of 20 μs and treatment time of 3 ms, as determined from a previous study (Roohinejad et al. 2014). The temperature of the carrot purée was measured prior to and after PEF treatment, using an electric thermometer (BAT-10 thermometer, Physitemp, Clifton, NJ, USA). All samples were treated using bipolar square pulses. PEF-treated carrot purée was centrifuged twice at 15,300×g for 30 min at 4 °C, and the solid phase (pomace) was separated and freeze-dried. After this process, the dehydrated carrot pomace (carrot fibre) was milled, passed through a 14 mesh (1.19 mm) sieve and stored at −18 °C for later use. Untreated carrot pomace was also freeze-dried, milled, sieved and stored as for the PEF-treated carrot pomace.

    Food Bioprocess Technol (2014) 7:3336–3348 3337

  • Experimental Design

    A preliminary study was carried out to determine the optimal β-carotene extraction efficiency from untreated carrot pomace