Decaffeination of yerba mate by supercritical fluid extraction: Improvement, mathematical modelling and infusion analysis

https://doi.org/10.1016/j.supflu.2020.105096Get rights and content

Highlights

  • Decaffeination of yerba mate leaves by supercritical fluid extraction.

  • Supercritical CO2 extractions performed at 300 bar and 60 °C with ethanol as cosolvent.

  • Box-Behnken design result: CO2 flow (950 g/h); ethanol flow (106 g/h); time (4.25 h).

  • Caffeine does not influence in the antioxidant capacity and cell viability of esophageal.

  • Caffeine concentration in infusion of the decaffeinated yerba mate is 0.030% ± 0.005%

Abstract

This work aimed to improve yerba mate caffeine extraction process, considering three independent variables, carbon dioxide flow, ethanol flow and extraction time, in three levels. The following process parameters were kept constant: pressure (300 bar), temperature (60 °C), and particle size (0.428 mm). The Box-Behnken experimental design was carried out for 15 extractions and the optimized condition to obtain decaffeinated yerba mate was as follows: 950 g/h of the carbon dioxide flow; 106 g/h of the ethanol flow; 4.25 h of the time. Under these conditions, it was possible to obtain processed yerba mate with 0.16% ± 0.06% (gcaffeine/gyerba mate). Furthermore, the removal of caffeine from yerba mate did not decrease the antioxidant capacity of extracts obtained by infusion, as well as cell viability tests showed that both extracts decreased cell viability in esophageal cancer. These results indicate that decaffeinated yerba mate maintains that properties found in traditional yerba mate.

Introduction

Discovered in 1820, caffeine is one of the most consumed stimulating substances worldwide [1] and is part of the everyday lives of most people in different countries [2]. Caffeine is capable of stimulating the nervous, muscular and circulatory systems [3], increasing mental focus; and acting against fatigue [4]. Several drinks contain caffeine, including coffee, tea, infusions such as chimarrão and tereré, guarana and cola sodas [5,6]. The consumption of these caffeine-containing products is not always recommended for everyone, since they can have undesirable health effects. The most affected groups are children, pregnant women and individuals with a higher sensibility to the effects of caffeine on the nervous system. These side effects range from insomnia, elevation of blood pressure, increasing metabolic rate, and diuresis [7]. Therefore, decaffeination of these products is important from a health perspective, while it is also economically attractive since it promotes obtaining decaffeinated products as well as natural caffeine, which is frequently used in pharmaceutical industries and in the production of energy drinks [8].

Yerba mate (Ilex paraguariensis St Hill) has a caffeine mass concentration of 0.5–2.0% in its dried leaves [9] and ingestion of this alkaloid usually occurs in the form of an infusion of crushed leaves and branches in hot or cold water, which are beverages called chimarrão or tereré, respectively [10]. As part of the Aquifoliaceae family, this species grows naturally in the subtropical regions of South America and is mainly found in Brazil, Argentina, Paraguay and Uruguay [11]. Several studies of yerba mate evaluate the chemical composition of the extracts, especially groups of compounds, such as flavonoids, saponins phenolic compounds and methylxanthines, including caffeine [6,12]. However, a number of factors can alter the extract chemical composition, including the planting and harvesting season, growing site and even industrial processing that the vegetable material is subjected to before being sold [6,13].

To decaffeinate leaves and seeds of different plant materials, different processes can be used: extraction with hot or cold water [14], extraction with organic solvents [15],and extraction with supercritical solvents [[16], [17], [18]]. In a comparison of these approaches, extraction with supercritical solvents has the advantage of being more selective than the other approaches and avoids the loss of important compounds to the final product [19]. It is important to highlight that the great majority of studies about decaffeination, using supercritical fluid extraction, usually have different types of teas and coffees as its main object of study [17,20]. Supercritical extraction of caffeine from yerba mate has been discussed in the works of Saldaña et al. [21], Cassel et al. [16], and Vieitez et al. [22].

This study aims to reduce the extraction time and solvent consumption of yerba mate decaffeination process, using ethanol as a co-solvent. Thus, the process variables CO2 flow, ethanol flow and extraction time will be evaluated under the following process conditions: 300 bar, 60 °C. High Performance Liquid Chromatography (HPLC) was used to analyze the caffeine content on the plant before and after the extraction process yerba mate decaffeination. Furthermore, the effects of caffeine concentration in the infusions were evaluated on cell viability in different cell lines of human esophageal cancer, and on antioxidant activity. This malignancy is the eighth most common cancer in the world [23,24] and, in Southern Brazil, is a recurrent disease among consumers of yerba mate infusions. Amigo-Benavent et al. [25] reported that consumption of yerba mate does not increase proliferation of cancer cells, suggesting yerba mate might have interesting anti-proliferative potential in cancer prevention due to bioactive compounds as phenolic compounds. Therefore, we highlight the effects of phenolic compounds and methylxanthines on esophageal cancer.

Section snippets

Yerba mate

Yerba mate leaves were provided by Baldo S.A, located in São Mateus do Sul - Brazil. As for processing step, the plant material used in this study was recovery after the roasting or zapecado [13]. The mean particle diameter of the leaves used in the experiments was 0.428 mm, evaluated using 5 sieves from the Tyler series with mesh sizes ranging from 16/46 plus the pan, with 15 min of agitation. The moisture content of each sample was determined by the principle of thermogravimetry and the

Results and discussion

The data obtained for studied properties of yerba mate leaves used in supercritical extraction process, moisture content and experimental density, are 4.6000 ± 0.0004% (m/m) = 1.3140 ± 0.0015 g/cm3, respectively, as well as the initial caffeine concentration in yerba mate leaves for the experimental design was 2.1% (gcaffeine/gyerba mate).

The results for supercritical extractions performed with 140 g of yerba mate at 300 bar and 60 °C and as independent variables: carbon dioxide flow (700, 950,

Conclusion

The study on process variables of yerba mate decaffeination by supercritical fluid extraction at 300 bar and 60 °C concluded that the caffeine extraction was more influenced to variables time extraction and ethanol flow (co-solvent) than CO2 flow. As well as the use of a yerba mate from another source than that used at experimental design, resulted in a caffeine concentration of 0.163% ± 0.06% (gcaffeine/gyerba mate), validating the results of the Box-Behnken experimental design. In relation to

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors are grateful to the Brazilian agencies CAPES, CNPq and FAPERGS for the financial support. Special thanks are given to Baldo S.A. for the technical and financial support.

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