Effect of temperature and pressure on the extraction of strawberry receptacles with a mixture of supercritical carbon dioxide and entrainers

doi:10.1016/j.supflu.2017.07.011

The Journal of Supercritical Fluids

Volume 130, December 2017, Pages 23-29

https://doi.org/10.1016/j.supflu.2017.07.011 Get rights and content

Highlights

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Extraction of strawberries was conducted with supercritical CO₂ and entrainers.
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Ethanol, acetone and water improved the antioxidant capacity.
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The extracted saccharides increased with increasing temperature and pressure.
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The extracted cinnamic acid increased with increasing temperature and pressure.
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The optimal condition for antioxidant capacity was proposed.

Abstract

Strawberries are one of the most popular fruits in Japan and they have a high antioxidant content. In this study, the contents in strawberry receptacles were extracted with supercritical carbon dioxide and entrainers. Using ethanol, acetone, and water as entrainers improved the antioxidant capacity and increased the amounts of total saccharides and cinnamic acid in the extract. In supercritical carbon dioxide + ethanol, the extract yield increased slightly with increasing pressure up to 20 MPa at 313 K whereas the extract yield was almost constant against temperature. The amounts of total saccharides and cinnamic acid increased with increasing temperature and pressure. The antioxidant capacity increased, and then decreased with increasing temperature at 20 MPa and increasing pressure at 313 K. The optimal conditions for antioxidant capacity were 313 K and 20 MPa.

Graphical abstract

Introduction

Strawberries are one of the most popular fruits in Japan and about 160,000 tons are produced each year. Strawberries have high antioxidant properties because they contain antioxidants such as phenolics, anthocyanins, and vitamin C [1], [2], [3], [4]. Strawberry receptacle is red and main edible part of it. The main content of strawberry receptacles is moisture (90 wt%), and the amount of total phenolics is a few hundred micrograms per 100 g of sample. The extraction of useful fractions, such as antioxidant components from strawberries, is expected to be developed for new health foods and supplements.

Supercritical carbon dioxide (sc-CO₂) is a useful solvent for extracting natural products [5]. sc-CO₂ is an inert, non-toxic, and environment-friendly solvent and its critical temperature and pressure are 304.2 K and 7.4 MPa, respectively. The critical temperature and pressure are low enough to enable sc-CO₂ extraction at low temperatures and pressures, which suppresses the thermal denaturation of the extract that occurs at high temperatures and makes the construction of extraction systems easier. sc-CO₂ is rapidly taken up by osmosis into samples to achieve effective extraction because of its high diffusivity and low density, viscosity, and surface tension compared with those of liquid CO₂. Furthermore, the sc-CO₂ density changes greatly with temperature and pressure, which alters the solubility of compounds. sc-CO₂ dissolves lipophilic compounds because it is a nonpolar solvent. The addition of a polar entrainer, such as methanol, ethanol, or water, allows the extraction of polar components that are difficult to dissolve in pure sc-CO₂.

The extraction of berries with sc-CO₂ has been reported previously (Table 1). In these studies, the temperature was from 303 to 333 K and the pressure was from 8 to 45 MPa. These studies are classified as using an entrainer or not using an entrainer. Without the entrainer, the seed extracts of various northern berries, including strawberries, contain seed oil including fatty acids and tocopherols or tocotrienols [6]. The antioxidant activity of blueberry, cranberry, and raspberry extracts is as large as that of conventional solvent extracts, and the trends in the amounts of extract and phenolics against pressure depend on the type of berry [7]. For raspberries, the amount of extract increases with increasing pressure [8]. Entrainers can be used to improve the extraction. The mixture 90% CO₂ + 5% H₂O + 5% ethanol gives the highest amount of anthocyanins in the extraction of blueberries because anthocyanins are water-soluble [9]. In the extraction of sea buckthorn berries, both the antioxidant activity and the amount of carotene in the extract obtained with methanol as the entrainer are larger than those obtained with ethanol and 2-propanol [10]. In the extraction of elderberry pomace in the presence of ethanol and water, the solvent composition affects the extract yield and the properties of the extract, such as the total amount of phenolic compounds. These results indicate that ethanol and water play an important role in the extraction of anthocyanins [11]. Pretreatment with sc-CO₂ and sc-CO₂ + ethanol before extracting elderberries with ethanol or ethanol aqueous solution is effective for extracting polyphenols [12]. The extraction of blackberries was enhanced by ultrasonication [13] in sc-CO₂ + ethanol or water. For strawberries, extraction has been performed on the seeds at only a single temperature and pressure. The extraction of strawberry receptacles has not been studied; therefore, the effect of solvent properties on the extraction is not known.

In this study, we examined the extraction of strawberry receptacles with sc-CO₂ and sc-CO₂ + entrainer. The extracts obtained with sc-CO₂ and sc-CO₂ + entrainer were compared to elucidate the effect of the entrainers. The dependence of the temperature and pressure on the extract yield, antioxidant capacity, and the amount of product were evaluated at 20 MPa and 313 K, respectively.

Section snippets

Experimental

Strawberry receptacles grown in Tochigi Prefecture in Japan were harvested and frozen. The moisture content of the strawberry receptacles was determined as 89.7 wt% by a moisture analyzer (MOC-120H, Shimadzu Corp.). The frozen strawberry receptacles were defrosted at room temperature and cut up. Ethanol (>99.5%) and acetone (>99.5%) were purchased from Wako Pure Chemical Industries Ltd. or Kanto Chemical Co., Inc. 1,1-Diphenyl-2-picrylhydrazyl (DPPH; >97%) was purchased from Tokyo Chemical

Results and discussion

Table 2 shows the extract yield, antioxidant capacity, amount of total saccharides, and amount of cinnamic acid at 313 K and 20 MPa in sc-CO₂ with an entrainer at a molar ratio of entrainer to CO₂ of 0.1 and without an entrainer. This condition gave the highest antioxidant capacity in the extraction with sc-CO₂ + ethanol as explained afterwards. The system was probably homogeneous for sc-CO₂, sc-CO₂ + ethanol [15], and sc-CO₂ + acetone [16]. Phase separation probably occurred in sc-CO₂ + H₂O into a CO₂

Conclusion

Strawberry receptacles were extracted with sc-CO₂ and sc-CO₂ + ethanol, acetone, and water. Extraction at 313 K, 20 MPa, an entrainer molar ratio to solvent of 0.1 and 3.95 × 10⁻⁵ mol/s of CO₂ flow rate for 120 min produced an extract yield of around 0.25 wt% regardless of the conditions. The entrainer increased the antioxidant capacity and the amounts of total saccharides and cinnamic acid in the extract. The detailed kinetics of the extraction were evaluated for the sc-CO₂ + ethanol system. The

Acknowledgement

This work was partially supported by the Regional Innovation Strategy Support Program, MEXT, Japan.

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Effect of temperature and pressure on the extraction of strawberry receptacles with a mixture of supercritical carbon dioxide and entrainers

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Experimental

Results and discussion

Conclusion

Acknowledgement

Bioactive compounds and quantification of total ellagic acid in strawberries (Fragaria x ananassa Duch.)

Food Chem.

E-Cinnamic acid derivatives and phenolics from chilean strawberry fruits, Fragaria chiloensis ssp. chiloensis

J. Agric. Food Chem.

1,2-Propanediol in strawberries and its role as a flavor precursor

Food Chem.

Assasy systems for screening food and natural substances that have anti-hyperuricemic activity: uric acid production in cultured hepatocytes and purine bodies-induced hyperuricemic model mice

Cytotechnology

Application of supercritical CO2 in lipid extraction—a review

J. Food Eng.

Composition and antioxidative activities of supercritical CO2-extracted oils from seeds and soft parts of northern berries

Food Res. Int.

Extraction of antioxidants from several berries pressing wastes using conventional and supercritical solvents

Eur. Food Res. Technol.

Optimization of high pressure extraction processes for the separation of raspberry pomace into lipophilic and hydrophilic fractions

J. Supercrit. Fluids

Extraction of phenolic compounds and anthocyanins from blueberry (Vaccinium myrtillus L.) residues using supercritical CO2 and pressurized liquids

J. Supercrit. Fluids

Antioxidant-rich extract from dehydrated Sea buckthorn berries by supercritical carbon dioxide extraction

Food Bioprocess Technol.

Effect of solvent (CO2/ethanol/H2O) on the fractionated enhanced solvent extraction of anthocyanins from elderberry pomace

J. Supercrit. Fluids

Extraction of phenolic compounds from elder berry and different grape marc varieties using organic solvents and/or supercritical carbon dioxide

J. Food Eng.

Application of supercritical CO₂ in lipid extraction—a review

Composition and antioxidative activities of supercritical CO₂-extracted oils from seeds and soft parts of northern berries

Extraction of phenolic compounds and anthocyanins from blueberry (Vaccinium myrtillus L.) residues using supercritical CO₂ and pressurized liquids

Effect of solvent (CO₂/ethanol/H₂O) on the fractionated enhanced solvent extraction of anthocyanins from elderberry pomace