TAHMASB HATAMI
Effects of grinding time, grinding load, and cold pressing on the aromatic compounds content of extract from fennel obtained by supercritical fluid extraction: experimental and mathematical modeling
Efeitos do tempo de moagem, carga de moagem, e prensagem a frio no conteúdo de compostos aromáticos do extrato de funcho obtido por extração com fluido supercrítico: experimental e modelagem matemática
CAMPINAS 2018
EFFECTS OF GRINDING TIME, GRINDING LOAD, AND COLD PRESSING ON THE AROMATIC COMPOUNDS CONTENT OF EXTRACT FROM FENNEL OBTAINED BY SUPERCRITICAL FLUID EXTRACTION: EXPERIMENTAL AND
MATHEMATICAL MODELING
EFEITOS DO TEMPO DE MOAGEM, CARGA DE MOAGEM, E PRENSAGEM A FRIO NO CONTEÚDO DE COMPOSTOS AROMÁTICOS DO EXTRATO DE
FUNCHO OBTIDO POR EXTRAÇÃO COM FLUIDO SUPERCRÍTICO: EXPERIMENTAL E MODELAGEM MATEMÁTICA
PhD thesis presented at the School of Food Engineering, Estate University of Campinas, as part of the requirements for obtaining the title of Doctor in Food Engineering.
Tese de doutorado apresentada à Faculdade de Engenharia de Alimentos, da Universidade Estadual de Campinas, como parte dos requisitos exigidos para obtenção do título de Doutor em Engenharia de Alimentos.
Supervisor: Prof. MARIA ANGELA DE ALMEIDA MEIRELES PETENATE
ESTE EXEMPLAR CORRESPONDE À VERSÃO FINAL DA TESE DEFENDIDA PELO ALUNO: TAHMASB HATAMI E ORIENTADA PELA PROF.ª DR.ª MARIA ANGELA DE ALMEIDA MEIRELES PETENATE
CAMPINAS 2018
Universidade Estadual de Campinas
Biblioteca da Faculdade de Engenharia de Alimentos Claudia Aparecida Romano - CRB 8/5816
Hatami, Tahmasb,
H28e HatEffects of grinding time, grinding load, and cold pressing on the aromatic
compounds content of extract from fennel obtained by supercritical fluid extraction : experimental and mathematical modeling / Tahmasb Hatami. – Campinas, SP : [s.n.], 2018.
HatOrientador: Maria Angela de Almeida Meireles Petenate.
HatTese (doutorado) – Universidade Estadual de Campinas, Faculdade de
Engenharia de Alimentos.
Hat1. Extraçâo supercrítica. 2. Prensagem. 3. Moagem. 4. Modelagem
matemática. 5. Método dos elementos finitos. I. Petenate, Maria Angela de Almeida Meireles. II. Universidade Estadual de Campinas. Faculdade de Engenharia de Alimentos. III. Título.
Informações para Biblioteca Digital
Título em outro idioma: Efeitos do tempo de moagem, carga de moagem, e prensagem a
frio no o conteúdo de compostos aromáticos do extrato de funcho obtido por extração com fluido supercrítico : experimental e modelagem matemática
Palavras-chave em inglês:
Supercritical extraction Pressing
Grinding
Mathematical modeling Finite element method
Área de concentração: Engenharia de Alimentos Titulação: Doutor em Engenharia de Alimentos Banca examinadora:
Maria Angela de Almeida Meireles Petenate [Orientador] Priscilla Carvalho Veggi
Paulo de Tarso Vieira e Rosa Pedro Esteves Duarte Augusto Reginaldo Guirardello
Data de defesa: 30-05-2018
Programa de Pós-Graduação: Engenharia de Alimentos
____________________________________________
Prof.ª Dr.ª Maria Angela de Almeida Meireles Petenate ORIENTADORA – DEA/FEA/UNICAMP
____________________________________________
Prof.ª Dr.ª Priscilla Carvalho Veggi MEMBRO TITULAR - USP
____________________________________________
Prof. Dr. Paulo de Tarso Vieira e Rosa MEMBRO TITULAR – IQ/UNICAMP
____________________________________________
Prof. Dr. Pedro Esteves Duarte Augusto MEMBRO TITULAR - USP
___________________________________________
Prof. Dr. Reginaldo Guirardello MEMBRO TITULAR – FEQ/UNICAMP
A ata da Defesa, assinada pelos membros da Comissão examinadora, consta no processo de vida acadêmica do aluno.
passed many years in abroad without thanking themworthy, but they have never passed even a moment without loving and supporting me continuously. They are the best parents ever.
Angela A. Meireles, for her perfect supervision and valuable guidance. She is the best supervisor I have ever had in my academic life. My sincere thanks also go to Prof. Ozan N. Ciftci, Department of Food Science and Technology, University of Nebraska-Lincoln, USA who provided me an excellent opportunity to join his lively team as a visiting researcher.
I am using this opportunity to thank all professors in School of Food Engineering, UNICAMP, for their patience, motivation, and immense knowledge. In particular, I would like to thanks Prof. Julian Martínez and Prof. Douglas Fernandes Barbin, both from UNICAMP, and Prof. Juliana Martin do Prado, from UFSCAR, for their great comment on the first draft of my thesis.
My honest thanks also go to my colleagues in LASEFI, Ariovaldo Astini, Gislaine Chrystina Nogueira de Faria, Renata Vardanega, Grazielle Náthia Neves, Juliana Queiroz Albarelli, Pedro Ivo Nunes, Ricardo Abel Del Castillo Torres, Diego Tresinari dos Santos, Eric Keven Silva, and Juan Felipe Osorio Tobón. In particular, I am deeply appreciated my friend Júlio Cezar Flores Johner for helping and advising me in every stage of this thesis. I am also appreciated my colleagues in Ciftci lab, Lisbeth Vallecilla Yepez, Junsi Yang, and Ali Ubeyitogullari during my stay in UNL for all the assistance provided in performing experiments and for the fellowship and friendship.
I would like to thank the examination board of my defense meeting for their participation and suggestions that enhanced the quality of thesis.
Last but not the least, I am really grateful my friends, parents, brothers, and sisters for supporting me spiritually throughout not only my PhD program, but also my life.
fluid extraction (SFE) from fennel, and modeled the process mathematically. In the first part of this thesis, the impacts of grinding time (GT) and mass of raw material in mill (ms) were
considered on both global SFE yield from fennel and its main volatile oil content namely anethole and fenchone. For this purpose, the extractor was filled with milled fennel obtained at various values of ms, from 15 g to 35 g, and GT, from 15 s to 20 min. Extractor was
subjected to pressure of 200 bar, temperature of 40 oC, and supercritical CO2 flow rate of
1.67×10-4 kg/s for 10 minutes. Then, extract composition was evaluated by Gas Chromatography (GC) analysis. For better understanding how GT and ms affect SFE yield
and extract composition, their effects were also investigated on temperature raising and diameter of fennel seeds during grinding process. It was found that ms and GT have
considerable effects on anethole and fenchone content of fennel extract. In the second part of this thesis, the effect of GT, from 15 s to 20 min, was investigated on the dynamic yield of SFE from fennel over 80 min extraction. The experimental data was then modeled based on mass conservation law for both fluid and solid phases. Partial differential equations (PDEs) of the model were solved using Galerkin´s method on finite element method (FEM). The main feature of this part of thesis is that it reports a first complete solution strategy to solve the PDEs of SFE model using FEM. In the last part of this thesis, supercritical fluid extraction assisted by pressing (SFEAP) and SFE were compared in terms of fennel extraction kinetics as well as extract fractionation. Extractor was subjected to the pressure of 200 bar, temperature of 40 oC, and solvent to feed ratio of 100 using torques of 40 and 70 N.m. Fennel oil extracted with SFE and SFEAP were then successfully fractionated into the volatile oil and other fractions using two series of equal-sized separators. It was found that despite the superiority of SFEAP over SFE in terms of extraction performance, SFE gave better performance for obtaining volatile extract in the second separator.
Keywords: Supercritical extraction, pressing, grinding, mathematical modeling, finite
com fluido supercrítico (SFE) de funcho e modelou o processo matematicamente. Na primeira parte desta tese, os impactos do tempo de moagem (GT) e da massa de matéria-prima (ms)
foram considerados tanto no rendimento global de SFE a partir de funcho e conteúdo de seu principal óleo volátil, ou seja, anetol e fenchona. Para este propósito, o extrator foi preenchido com funcho moído obtido em vários valores de ms, de 15 g a 35 g, e GT, de 15 a 20 min. O
extrator foi submetido à pressão de 200 bar, temperatura de 40 oC e vazão de CO2 supercrítico
de 1,67 × 10-4 kg / s por 10 minutos. Em seguida, a composição do extrato foi avaliada por análise de cromatográfica gasosa (GC). Além disso, para uma melhor compreensão de como o GT e o ms afetam o rendimento de SFE e a composição do extrato, seus efeitos foram
investigados quanto ao aumento de temperatura e diâmetro das sementes de funcho durante o processo de moagem. Verificou-se que ms e GT têm efeitos consideráveis sobre o teor de
anetol e fenchona do extrato de funcho. Na segunda parte desta tese, o efeito do GT, de 15 s a 20 min, foi investigado sobre o rendimento dinâmico de SFE a partir da extração de funcho durante 80 min. Os dados experimentais foram então modelados com base na lei de conservação de massa para as fases fluida e sólida. Equações diferenciais parciais (PDEs) do modelo foram resolvidas usando o método de Galerkin no método dos elementos finitos (MEF). A principal característica desta parte da tese é que ela relata uma primeira estratégia de solução completa para resolver os PDEs do modelo SFE usando FEM. Na última parte desta tese, a extração com fluido supercrítico assistida por prensagem (SFEAP) e SFE foram comparadas em termos de cinética de extração bem como o fracionamento do extrato de funcho. O extrator foi submetido à pressão de 200 bar, temperatura de 40 oC e uma relação de massa de solvente por massa de matéria-prima de 100 utilizando os torques de 40 e 70 N.m. O óleo de funcho extraído com SFE e SFEAP foi então fracionado com sucesso no óleo volátil e outras frações utilizando duas séries de separadores de tamanho igual. Verificou-se que, apesar da superioridade da SFEAP em relação ao SFE em termos de desempenho de extração, o SFE apresentou melhor desempenho na obtenção de extrato volátil no segundo separador.
Palavras-chave: Extração supercrítica, prensagem, moagem, modelagem matemática,
Figure 3.2 - Schematic diagram of the SFE unit from (a) top view and (b) front view (Johner
and Meireles, 2016)……….………..34
Figure 3.3 - The average size of Fennel particles at various values of GT and ms ...35
Figure 3.4 - The raising temperature of Fennel at the end of grinding process ...35
Figure 3.5 - Fennel distributions inside the crushing chamber of mill ...36
Figure 3.6 - Effect of GT and ms on the overall extraction yield obtained by SFE from Fennel at 200 bar, 313 K, and 1.67×10-4 kg/s during 10 min...36
Figure 3.7 - Effect of GT and ms on the anethol extraction yield obtained by SFE from Fennel at 200 bar, 313 K, and 1.67×10-4 kg/s, during 10 min………...36
Figure 3.8 - Effect of GT and ms on the fenchone extraction yield obtained by SFE from Fennel at 200 bar, 313 K, and 1.67×10-4 kg/s, during 10 min...37
Figure 4.1 - The effect of GT on the temperature increase (ΔT) and the average size of fennel particles (dp) (Hatami et al., 2017)...44
Figure 4.2 - SFE unit used in this study...46
Figure 4.3 - Finite element mesh of the extractor ...49
Figure 4.4 - Comparison between the model results and the experimental data for SFE from fennel ...……….59
Figure 4.5 - Effect of the number of mesh elements (n) on the FEM and FDM results for Exp. 3……….60
Figure 4.6 - The extractor with one element……...61
Figure 5.1 - Schematic diagram of the SFEAP unit: (A1) Pressing system, (A2) Extractor, (B) First separator, (C) Second separator, (D) Outlet of separators, (E) Leadscrew, (F) Socket sliding, (G) Torque meter, (H) Shut-off valve, (I) Micro-metering valve, and (J) Gas flow meter.………...…………. 72
Figure 5.2 - Extraction yield of milled fennel (GT = 6 min) using SFE and SFEAP at 200 bar and 40 °C. …...……….……….74
Figure 5.3 – A schematic of (A) raw material after extraction using SFE, (B) raw material after extraction using SFEAP, (C) SFE extract in Separator 1 (D) SFE extract in Separator 2, (E) SFEAP extract in Separator 1, (F) SFEAP extract in Separator 2……...………..….77
Table 4.2 - The parameters of the SFE model...57 Table 5.1 - The significance of temperature, pressure, S/F, particle diameter, and torque on
the SFE yield from fennel...76
LIST OF TABLES...10
CHAPTER 1 - GENERAL INTRODUCTION, OBJECTIVES AND STRUCTURE OF THE THESIS……….13 1.1. INTRODUCTION...14 1.2. JUSTIFICATION...15 1.3. OBJETIVES...15 1.4. THESIS STRUCTURE...16 REFERENCES...17
CHAPTER 2 - LITERATURE REVIEW...20
1. SFE FROM FENNEL...21
2. MATHEMATICAL MODELING OF SFE...23
3. SFEAP FROM FENNEL...25
REFERENCES...26
CHAPTER 3 - EFFECTS OF GRINDING TIME ON SUPERCRITICAL FLUID EXTRACTION……….30
1. INTRODUCTION...32
2. MATERIALS AND METHODS...33
3. RESULTS AND DISCUSSION...35
4. CONCLUSIONS...37
REFERENCES...37
CHAPTER 4 - MATHEMATICAL MODELING OF SUPERCRITICAL FLUID EXTRACTION……….39
1. INTRODUCTION...42
2. MATERIAL AND METHODS...45
3. RESULTS AND DISCUSSION...57
4. CONCLUSIONS...61
REFERENCES...62
CHAPTER 5 - SUPERCRITICAL FLUID EXTRACTION ASSISTED BY COLD PRESSING………....66
REFERENCES...79
CHAPTER 6 GENERAL DISCUSSIONS...82
CHAPTER 7 GENERAL CONCLUSIONS...85
MEMORANDUM OF THE PhD PERIOD...87
REFERENCES...91
CHAPTER 1
GENERAL INTRODUCTION, OBJECTIVES AND STRUCTURE OF THE THESIS
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CHAPTER 1
General Introduction, Objectives and Structure of the Thesis
1.1. INTRODUCTION
Fennel (Foeniculum vulgare) is a plant belonging to Apiaceae family, which is cultivated in several countries like Brazil, England, Germany, and China (Brender et al., 1997). Fennel extracts can be employed as antispasmodic, anti-inflammatory, expectorant, diuretic, and laxative (Jahromi et al., 2003). It also has applications in treatment of nervous disturbances, carminative, analgesic, and stimulant of gastrointestinal mobility (Jahromi et al., 2003). One of the promising methods for extraction of oil from fennel is supercritical fluid extraction (SFE) (Yamini et al., 2002; Piras et al., 2014; Díaz-Maroto et al., 2005). Supercritical fluids (SCF) have proved to be effective solvents for extraction from solids, and SFE are widely used by many researchers (Mackėla et al., 2017; Conde-Hernández et al., 2017) and industries due to its high mass transfer rate as well as simple separation of solvent from extract at the end of process (Gallo et al., 2017; Antunes-Ricardo et al., 2017). Two of the attractive research areas in the field of SFE from fennel are either maximizing overall extraction yield or maximizing anethole and fenchone content of the volatile oil. The first necessary step for these goals is grinding fennel seeds to increase their specific area. Grinding procedure has not been sufficiently addressed so far in SFE field. Two main key factors in grinding are grinding time and grinding load. Although the effect of grinding time (GT) was already investigated on the SFE yield of other raw materials, researchers limited themselves to small GT (Wilkinson et al., 2014; Yahya et al., 2010). After investigating the effects of grinding time and load on the SFE yield experimentally, it is very important to model the SFE process mathematically (Hatami et al., 2014) in order to evaluate the interaction effects of factors and optimize the process accordingly. To this end, two main SFE models can be found in literature, empirical models, and mass transfer-based models. Although the empirical models have the advantages of simplicity, they are not suitable for scaling-up (del Valle and Fuente, 2006). Mass transfer-based models generally result in two partial differential equations (PDEs), one PDE for fluid phase and the other for solid phase (del Valle and Fuente, 2006; Oliveira et al., 2011). These kinds of models can be solved using numerical techniques such as finite difference method (FDM) or finite element method (FEM).
In addition to grinding procedure, another important preprocessing factor in SFE is cold pressing. Accordingly, a novel extraction technique has been recently developed by Johner et al. (2018), which is called SFEAP. SFEAP stands for supercritical fluid extraction assisted by cold pressing, which performance was successfully evaluated for extraction from pequi (Caryocar brasiliense) (Johner et al., 2018). However, more experiments with various raw materials, like fennel, are still required to evaluate this new technique in comparison with SFE.
1.2. JUSTIFICATION
As effects of milling process on yield and quality of SFE were not fully discussed in literature and researchers limited themselves to small grinding time (GT), the first aim of the current study was to focus on this area for a broad range of GT and various grinding loads. The experimental SFE data was then modeled based on mass conservation law for both fluid and solid phases. The main novelty of modeling part is presenting a systematic FEM technique for solving SFE model, which has not been reported yet. Additionally, most publications of SFE from fennel focused on the effects of temperature and pressures on the SFE performance, but there was no publication about SFEAP from fennel yet. Therefore, the third target of this thesis was to employ SFEAP for the extraction from fennel at constant temperature and pressure, but at different torques. Moreover, this thesis aimed to highlight the fractionation of extracts from SFE and SFEAP into volatile fraction and lipid fraction rich products and compare their composition to literature data.
1.3. OBJECTIVES
1.3.1. General objective
Evaluating the effects of grinding process and cold pressing on the aromatic compounds content of extract from fennel obtained by supercritical fluid extraction.
Studying impacts of grinding time (GT) and mass of raw material in mill (ms) on
both global SFE yield from fennel and its main volatile oil content, namely anethole and fenchone.
Mathematical modeling of SFE from fennel, and providing a step by step solution strategy of the model using finite element method.
Employing supercritical fluid extraction assisted by cold pressing (SFEAP) for extraction and fractionation from fennel.
Evaluating the effects of torque in SFEAP on the overall extraction yield.
1.4. THESIS STRUCTURE
The text is presented in 7 chapters. In chapter 1 - General Introduction,
Objectives and Structure of the Thesis - the most relevant aspects for the formulation of the
work are presented. This chapter presents a brief introduction of the scenario that propitiated the development of this thesis, the justification, the objectives outlined and the planned structure for the development of the works.
In Chapter 2 - Literature Review - a review on the topics covered in the thesis is presented. Literature on the extraction and fractionation from fennel, mathematical modeling, and integrating of cold pressing with SFE are discussed.
In Chapter 3 - Effects of grinding procedure on supercritical fluid extraction
- the article published in Industrial Crops & Products is presented.
In Chapter 4 - Mathematical modeling of supercritical fluid extraction - the article submitted to the Journal of Food Engineering is presented.
In Chapter 5 - Supercritical fluid extraction assisted by cold pressing - the article submitted to Industrial Crops & Products is presented.
Chapter 6 - General Discussion - brings an integrated discussion of the results
obtained in chapters 3, 4 and 5. Finally, chapter 7 - General Conclusions presents the general understandings and outlines obtained in this thesis.
Figure 1.1 shows a flowchart of thesis structure. As depicted in this figure, the thesis contains three main parts, namely the effect of grinding procedure on SFE, mathematical modeling of SFE, and integration of cold pressing with SFE.
Figure 1.1 – Flowchart of thesis structure.
REFERENCES
Antunes-Ricardo, M., Gutiérrez-Uribe, J.A., Guajardo-Flores, D., 2017. Extraction of isorhamnetin conjugates from Opuntia ficus-indica (L.) Mill using supercritical fluids. J. Supercrit. Fluids, 119, 58-63.
Brender, T., Gruenwald, J., Jaenicke, C., 1997. Herbal Remedies, Phytopharm Consulting Institute for Phytopharmaceuticals (2. ed.). Schaper & Brümmer GmbH & Co., Salzgitter, Berlin, Germany.
Conde-Hernández, L.A., Espinosa-Victoria, J.R., Trejo, A., Guerrero-Beltrán, J.Á., 2017. CO2-supercritical extraction, hydrodistillation and steam distillation of essential oil of rosemary (Rosmarinus officinalis). J. Food Eng. 200, 81-86.
del Valle, J.M., Fuente, J.C.D.L., 2006. Supercritical CO2 extraction of oilseeds: review of
kinetic and equilibrium models. Crit. Rev. Food Sci. Nutr. 46, 131-160.
Díaz-Maroto, M.C., Díaz-Maroto Hidalgo, I.J., Sánchez-Palomo, E., Pérez-Coello, M.S., 2005. Volatile components and key odorants of fennel (Foeniculum vulgare Mill.) and thyme (Thymus vulgaris L.) oil extracts obtained by simultaneous distillation− extraction and supercritical fluid extraction. J. Agric. Food Chem. 53(13), 5385-5389.
Gallo, M., Formato, A., Ianniello, D., Andolfi, A., Conte, E., Ciaravolo, M., Varchetta, V., Naviglio, D., 2017. Supercritical fluid extraction of pyrethrins from pyrethrum flowers (Chrysanthemum cinerariifolium) compared to traditional maceration and cyclic pressurization extraction. J. Supercrit. Fluids, 119, 104-112.
Hatami, T., Moura, L.S., Khamforoush, M., Meireles, M.A.A., 2014. Supercritical fluid extraction from Priprioca: Extraction yield and mathematical modeling based on phase equilibria between solid and supercritical phases. J. Supercrit. Fluids, 85, 62-67.
Jahromi, B.N., Tartifizadeh, A., Khabnadideh, S., 2003. Comparison of fennel and mefenamic acid for the treatment of primary dysmenorrhea. Int. J. Gynaecol. Obstet. 80, 153-157.
Johner J.C.F., Hatami, T., Meireles, M.A.A., 2018. Developing a supercritical fluid extraction method assisted by cold pressing for extraction of pequi (Caryocar brasiliense). J. Supercrit. Fluids, 137, 34-39.
Mackėla, I., Andriekus, T., & Venskutonis, P.R., 2017. Biorefining of buckwheat (Fagopyrum esculentum) hulls by using supercritical fluid, Soxhlet, pressurized liquid and enzyme-assisted extraction methods. J. Food Eng. 213, 38-46.
Oliveira, E.L., Silvestre, A.J., Silva, C.M., 2011. Review of kinetic models for supercritical fluid extraction. Chem. Eng. Res. Des. 89, 1104-1117.
Piras, A., Falconieri, D., Porcedda, S., Marongiu, B., Gonçalves, M.J., Cavaleiro, C., Salgueiro, L., 2014. Supercritical CO2 extraction of volatile oils from Sardinian Foeniculum vulgare ssp. vulgare (Apiaceae): chemical composition and biological activity. Nat. Prod. Res. 28(21), 1819-1825.
Wilkinson, N., Hilton, R., Hendry, D., Venkitasamy, C., Jacoby, W., 2014. Study of process variables in supercritical carbon dioxide extraction of soybeans. Food Sci. Technol. Int. 20(1), 63-70.
Yahya, F., Lu, T., Santos, R.C.D., Fryer, P.J., Bakalis, S., 2010. Supercritical carbon dioxide and solvent extraction of 2-acetyl-1-pyrroline from Pandan leaf: The effect of pre-treatment. J. Supercrit. Fluids 55, 200–207.
Yamini, Y., Sefidkon, F., Pourmortazavi, S.M., 2002. Comparison of essential oil composition of Iranian fennel (Foeniculum vulgare) obtained by supercritical carbon dioxide extraction and hydrodistillation methods. Flavour Fragr. J. 17(5), 345-348.
CHAPTER 2
LITERATURE REVIEWCHAPTER 2
1. SFE FROM FENNEL
Fennel (Foeniculum vulgare) is a plant belonging to Apiaceae family, which is cultivated in several countries like Brazil, England, Germany, and China among others (Brender et al., 1997). Fennel extracts can be employed as antispasmodic, anti-inflammatory, expectorant, diuretic and laxative (Jahromi et al., 2003). It also has applications in treatment of nervous disturbances, carminative, analgesic, and stimulant of gastrointestinal mobility (Jahromi et al., 2003). Anethole and fenchone are two of the main compounds in fennel volatile oil that compose, respectively, 40 to 70% and 1 to 20% of it (Bernath et al., 1996; Coşge et al., 2008; Raghavan, 2006). Extraction of volatile oil from fennel is generally carried out by several techniques such as supercritical fluid extraction (SFE), liquid CO2
extraction, soxhlet extraction, accelerated solvent extraction, and steam distillation (Baby and Ranganathan, 2016; Rodríguez-Solana et al., 2014a; Bodsgard et al., 2016; Johner and Meireles, 2016). Among all extraction techniques, SFE is usually a preferable technique for extraction from various raw materials due to its advantages such as high extraction performance, simple separation of solvent from extract, and selectivity capability (Durante et al., 2014; Ding et al., 2017). In a typical SFE process, solvent (CO2) flows slowly through a
bed containing raw material. Extract is then separated from solvent after passing the solvent-extract mixture through a reduction pressure system. SFE from fennel has been reported in various research works. Reverchon et al. (1999) carried out successfully extraction of fennel seeds in two steps including SFE at 90 bar and 50 °C, and SFE at 200 bar and 40 °C using three CO2 mass flow rates of 0.5, 1.0, and 1.5 kg/h. They also modeled the process based on
mass conservation law and demonstrated the reliability of the model by comparing it to experimental data. Yamini et al. (2002) obtained essential oil from Iranian fennel by hydro-distillation and SFE techniques. They investigated the effects of pressure (202.65 and 354.64 bar), temperature (45 and 55 oC), extraction time (30 and 45 min), and modifier (methanol) volume (80 and 400 µl) on the composition of extract at constant supercritical CO2 flow rate
of approximately 0.3–0.4 ml/min. It was found that the optimum operating condition for maximizing percentage of anethole in extract using SFE was the pressure of 354.64 bar, temperature of 55 °C, extraction time of 45 min, and modifier percentage of 5%. Under this
condition, the percentage of anethole in the extract was 90.14%, while the corresponding value using hydro-distillation method was 69.41%. These numbers together with the shorter extraction time of SFE compared to hydro-distillation (4 h), and selectivity of SFE confirmed its superiority over hydro-distillation. They reported that other main components in the extract were fenchone, 6.25% by SFE versus 11.00 % by hydro-distillation, and Limonene, 2.82 % by SFE versus 10.00 % by hydro-distillation. Moura et al. (2005) studied effect of harvesting season, degree of maturation, bed geometry, operating temperature and pressure on SFE yield from fennel. They also studied extraction of fennel by hydro-distillation and low-pressure solvent extraction, and compared their results to SFE. They found that not only SFE process produced larger relative proportion of anethole and fenchone, but also its overall extraction yield was 5.2 larger than that of hydro-distillation (Moura et al., 2005). Díaz-Maroto et al. (2005) compared SFE from fennel to simultaneous distillation-extraction (SDE) at 40 oC and 120 bar during 25 min. Analyzing the extracts by gas chromatography-mass spectrometry (GC-MS) confirmed that trans-anethole had the highest proportion of extract, 63.80% by SFE versus 49.71% by SDE, followed by estragole, 20.33 % by SFE versus 25.84 % by SDE, and fenchone, 12.71 % by SFE versus 19.33 % by SDE. In another relevant paper, Pereira and Meireles (2007) investigated economic analysis for obtaining extracts and essential oils from fennel using SFE and steam distillation. They concluded that in spite of high cost of SFE equipment, it was cheaper than steam distillation due to higher quality of its product, higher extraction yield, and lower energy consumption (Pereira and Meireles, 2007). Another paper in this topic was written by Hammouda et al. (2014), who studied extraction yield and extract quality from fennel using SFE, microwave-assisted extraction (MAE), and hydro-distillation. Their study showed that MAE gave higher overall yield and higher percentage of fenchone than others. SFE, on the other side, gave the maximum percentage of anethole (Hammouda et al., 2014). Piras et al. (2014) employed SFE and hydro-distillation on Sardinian wild fennel and measured composition of volatile extracts using gas chromatography –mass spectrometry. They found that percentage of the main components in SFE extract were 7.1% (fenchone), 34.9% (estragole), and 24.6% ((E)-anethole), while corresponding number for hydro-distillation extract were 8.8%, 42.6%, and 43.4%, respectively. Rodríguez-Solana et al. (2014b) performed oleoresin extraction from fennel seeds using SFE, and optimized the process for the aim of attaining maximum estragole per kg of dry plant. They found the optimal operating condition at the pressure of 240 bar, temperature of 60 oC, extraction
duration of 3.41 h, and methanol percentage of 3%. In this condition, they obtained 1320 ± 260 mg of estragole per kg dry plant. Ivanovic et al. (2014) increased the yield of SFE for
several raw materials by employing different mechanical pretreatment such as flaking, impact plus shearing, and cutting plus grinding. They found flaking as the most convenient method for increasing the SFE yield from fennel seeds.
According to the above literature review, two of the attractive research areas in the field of SFE from fennel are either maximizing overall yield or maximizing anethole and fenchone content of the volatile oil. The first necessary step for attending these goals is, however, grinding the fennel seeds to increase their specific area. Although the effect of grinding time (GT) was already investigated on the SFE yield of other raw materials, they limited themselves to small GT. For example, Wilkinson et al. (2014) investigated the effect of GT on the SFE yield from soybeans at 483 bar and 80 oC. They placed 60 g of soybeans in
a mechanical grinder for different GT from 10 to 60 s. They concluded that increasing GT enhanced the extraction yield due to the reduction of particle sizes. The SFE yield was increased from around 6% to 22% by decreasing the particle diameters from 0.20 mm to 0.07 mm. In another study by Yahya et al. (2010), SFE yield from Pandan leaf increased up to 50% after a pretreatment grinding for 30 s.
2. MATHEMATICAL MODELING OF SFE
After determining the SFE yield experimentally, it is very important to model the process mathematically (Hatami et al., 2014) not only to minimize the required number of experiments for sensitivity analysis, but also to optimize the process. To this end, two main SFE models can be found in literature: 1) empirical models 2) mass transfer-based models. Although the empirical models have the advantages of simplicity, they are not suitable for scaling-up (del Valle and Fuente, 2006). Mass transfer-based models generally result in two partial differential equations (PDEs), one PDE for fluid phase and the other for solid phase (del Valle and Fuente, 2006; Oliveira et al., 2011). Several models were proposed for SFE process in literature. Among all, Madras et al. (1994) proposed one of the general model based on the following assumptions: spherical particles with constant porosity, constant temperature and pressure, axial dispersion flow, unchanged bed porosity, and plug flow pattern for fluid velocity. Accordingly, mass balance equation for bulk fluid phase is:
(1) ∂Cf ∂t + v ∂Cf ∂z − Dl ∂2C f ∂z2 = 3(1 − ε) εR J
At 𝑡 = 0 ⟹ 𝐶𝑓 = 0 𝐴𝑡 𝑧 = 0 ⟹ 𝐷𝑙∂Cf ∂z = 𝑣Cf 𝑎𝑡 𝑧 = 𝐿 ⟹ ∂Cf ∂z = 0 (2)
Mass balance equation for solid phase is:
(3) ∂Cp ∂t + 1 εp ∂Cs ∂t = De r2 ∂ ∂r(r 2∂Cp ∂r )
With the following boundary and initial conditions: At 𝑡 = 0 ⟹ Cp= Cp0 & Cs= Cs0 𝐴𝑡 𝑟 = 0 ⟹ ∂Cp ∂r = 0 & ∂Cs ∂r = 0 𝑎𝑡 𝑟 = 𝑅 ⟹ εpDe∂Cp ∂r = −J (4)
Where, Cf (kg/m3), Cp (kg/m3), and Cs (kg/m3) are solute concentrations in the bulk fluid, pore
of particles, and solid phase, respectively. Relationship between Cp and Cs must be obtained
based on thermodynamic equilibrium between pore and solid of particles. z (m) is axial coordinate along extractor, t (s) is time, Dl (m2/s) is axial dispersion coefficient, De(m2/s) is effective diffusion coefficient in pore of particles, v (m/s) is interstitial velocity, R (m) is particle radius, L (m) is height of the bed, ε is bed porosity, εp is particle porosity, and J is
mass transfer rate, which is calculated as follow: J = kf(Cp|
r=R− Cf) (5)
Where, kf (m/s) is external mass transfer coefficient. To reduce computational cost in this
model, further simplifications may be employed depending on the geometrical and operating factors of the process under consideration. Some of the well-known simplifications are external mass transfer control, internal mass transfer control, no solute dispersion, linear driving force, and steady-state approximations. Each of these assumption changes one or both aforementioned mass balances PDEs of fluid and solid phases. A detail explanation in this issue can be found in a publication by del Valle and Fuente (2006). These kinds of models can be solved using either analytical or numerical techniques. Analytical techniques have been frequently used, and they were explained in literature in detail (Lucas et al., 2007; Mongkholkhajornsilp et al., 2005). As extra simplification is employed for analytical
techniques, such as ignoring axial dispersion effect in the papers by Lucas et al. (2007) and Mongkholkhajornsilp et al. (2005), they always have an inherent error. About numerical techniques, SFE models can be solved by either finite difference method (FDM) or finite element method (FEM). The fundamentals of FDM and FEM can be found in a number of sources (LeVeque, 2007; Kwon and Bang, 2000; Reddy, 1993). FDM partitions the PDE domain, and approximates the partial derivation terms at each point from neighboring values (Causon et al., 2010). FDM has been broadly used in SFE, and it was explained in detail by Meireles et al. (2009). FEM is another powerful numerical technique that had already employed for SFE modeling (Madras et al., 1994; Valderrama and Alarcón, 2009). However, there is no publication in literature yet to explain FEM on SFE model in detail. Such a publication is important for conceptual understanding of the FEM solution of the SFE process, and decreasing the computation cost for future relevant researches in this area.
3. SFEAP FROM FENNEL
Cold pressing is another preprocessing factor that can improve the SFE yield. This improvement of extraction yield is possibly due to the breaking of matrix raw material by applying pressing that consequently more oil liberates from particles, and so more oil exposes to supercritical CO2. SFE assisted by pressing (SFEAP) is a novel technique of extraction that
has been recently developed by Johner et al. (2018). SFEAP is an integration of SFE and cold pressing methods, whose performance was evaluated for extraction from pequi (Caryocar
brasiliense). Prior to study the impact of pressing, they studied SFE yield from pequi at two
isotherms, 313 and 333 K, and pressure from 20 to 40 MPa. It was found that a temperature of 333 K and pressure of 40 MPa, among others, gave the maximum SFE yield, 48 g extract/100 g raw material. So, they investigated the impact of pressing with torque of 40 N.m under the optimum condition of temperature and pressure. Comparing the SFEAP yield at 400 bar, 40
oC to that of SFE revealed that the SFEAP yield was eight times greater than that of SFE
during the first minute of extraction (Johner et al., 2018). According to the analysis of pequi oil, SFEAP did not change the fatty acid composition compared to SFE. As research in SFEAP area is still in the initial phase, there is no publication in literature regarding SFEAP from fennel yet. SFEAP can be also evaluated in terms of fractionation of fennel extract to produce volatile fraction and lipidic fraction rich products. Previous publications about fractionation of fennel extract using SFE revealed that temperature and pressure of extractor and first separator are the most critical factors affecting the fractionation performance. Simandi et al. (1999) fractionated SFE extract from fennel into volatile fraction rich and
lipidic fraction rich products using two subsequent separators. They recommended 80-84 bar and 31-35 °C as the best operating conditions of the first separator to minimize the presence of undesired components. Johner and Meireles (2016) performed extraction and fractionation from fennel using two separators with a flow rate of 2.00×10−4 kg/s of CO2 and solvent per
feed mass ratio (S/F) of 10. Temperature and pressure in the extractor, first separator, and second separator were, respectively, 40 oC and 200 bar, 35 oC and 80 bar, and 8 oC and 20 bar. Analysis of extract showed that from the overall extraction yield of 2.8%, around 97.5% was accumulated in the first separator (waxy phase), and the remaining 2.5% accumulated in the second separator (oily phase containing the volatile compounds).
REFERENCES
Baby, K.C., Ranganathan, T.V., 2016. Effect of enzyme pre-treatment on extraction yield and quality of fennel (Foeniculum vulgare) volatile oil. Biocatal. Agric. Biotechnol. 8, 248-256. Bernath, J., Nemeth, E., Kattaa, A., Hethelyi, E., 1996. Morphological and chemical evaluation of fennel (Foeniculum vulgare Mill.) populations of different origin. J. Essent. Oil Res. 8, 247-253.
Bodsgard, B.R., Lien, N.R., Waulters, Q.T., 2016. Liquid CO2 Extraction and NMR
Characterization of Anethole from Fennel Seed: A General Chemistry Laboratory. J. Chem. Educ. 93, 397-400.
Brender, T., Gruenwald, J., Jaenicke, C., 1997. Herbal Remedies, Phytopharm Consulting Institute for Phytopharmaceuticals. Second ed., Schaper & Brümmer GmbH & Co., Salzgitter, Berlin, Germany.
Causon, D.M., Mingham, C.G., 2010. Introductory finite difference methods for PDEs. Bookboon.
Coşge, B., Kiralan, M., Gürbüz, B., 2008. Characteristics of fatty acids and essential oil from sweet fennel (Foeniculum vulgare Mill. var. dulce) and bitter fennel fruits (F. vulgare Mill. var. vulgare) growing in Turkey. Nat. Prod. Res. 22, 1011-1016.
del Valle, J.M., Fuente, J.C.D.L., 2006. Supercritical CO2 extraction of oilseeds: review of
Díaz-Maroto, M.C., Díaz-Maroto Hidalgo, I.J., Sánchez-Palomo, E., Pérez-Coello, M.S., 2005. Volatile components and key odorants of fennel (Foeniculum vulgare Mill.) and thyme (Thymus vulgaris L.) oil extracts obtained by simultaneous distillation− extraction and supercritical fluid extraction. J. Agric. Food Chem. 53(13), 5385-5389.
Ding, X., Liu, Q., Hou, X., Fang, T., 2017. Supercritical Fluid Extraction of Metal Chelate: A Review. Crit. Rev. Anal. Chem. 47(2), 99-118.
Durante, M., Lenucci, M.S., Mita, G., 2014. Supercritical carbon dioxide extraction of carotenoids from pumpkin (cucurbita spp.): A review. Int. J. Mol. Sci. 15, 6725-6740.
Hammouda, F.M., Saleh, M.A., Abdel-Azim, N.S., Shams, K.A., Ismail, S.I., Shahat, A.A., Saleh, I.A., 2014. Evaluation of the essential oil of foeniculum vulgare mill (fennel) fruits extracted by three different extraction methods by Gc/Ms. Afr. J. Tradit. Complement Altern. Med. 11, 277-279.
Hatami, T., Moura, L.S., Khamforoush, M., Meireles, M.A.A., 2014. Supercritical fluid extraction from Priprioca: Extraction yield and mathematical modeling based on phase equilibria between solid and supercritical phases. J. Supercrit. Fluids, 85, 62-67.
Ivanovic, J., Meyer, F., Stamenic, M., Jaeger, P., Zizovic, I., Eggers, R., 2014. Pretreatment of natural materials used for supercritical fluid extraction of commercial phytopharmaceuticals. Chem. Eng. Technol. 37, 1606-1611.
Jahromi, B.N., Tartifizadeh, A., Khabnadideh, S., 2003. Comparison of fennel and mefenamic acid for the treatment of primary dysmenorrhea. Int. J. Gynaecol. Obstet. 80, 153-157.
Johner J.C.F., Hatami, T., Meireles, M.A.A., 2018. Developing a supercritical fluid extraction method assisted by cold pressing for extraction of pequi (Caryocar brasiliense). J. Supercrit. Fluids, 137, 34-39.
Johner, J.C.F., Meireles, M.A.A., 2016. Construction of a supercritical fluid extraction (SFE) equipment: validation using annatto and fennel and extract analysis by thin layer chromatography coupled to image. Food Sci. Technol. (Campinas) 36(2), 210-247.
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Lucas, S., Calvo, M., Garcia-Serna, J., Palencia, C., Cocero, M., 2007. Two-parameter model for mass transfer processes between solid matrixes and supercritical fluids: Analytical solution. J. Supercrit. Fluids, 41, 257-266.
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Meireles, M.A.A., Zahedi, G., Hatami, T., 2009. Mathematical modeling of supercritical fluid extraction for obtaining extracts from vetiver root. J. Supercrit. Fluids, 49, 23-31.
Mongkholkhajornsilp, D., Douglas, S. Douglas, P.L., Elkamel, A., Teppaitoon, W., Pongamphai, S., 2005. Supercritical CO2 extraction of nimbin from neem seeds––a modelling
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Moura, L.S., Carvalho Jr, R.N., Stefanini, M.B., Ming, L.C., Meireles, M.A.A., 2005. Supercritical fluid extraction from fennel (Foeniculum vulgare): global yield, composition and kinetic data. J. Supercrit. Fluids 35, 212-219.
Oliveira, E.L., Silvestre, A.J., Silva, C.M., 2011. Review of kinetic models for supercritical fluid extraction. Chem. Eng. Res. Des. 89, 1104-1117.
Pereira, C.G., Meireles, M.A.A., 2007. Economic analysis of rosemary, fennel and anise essential oils obtained by supercritical fluid extraction. Flavour Frag. J. 22, 407-413.
Piras, A., Falconieri, D., Porcedda, S., Marongiu, B., Gonçalves, M.J., Cavaleiro,C., Salgueiro, L., 2014. Supercritical CO2 extraction of volatile oils from Sardinian Foeniculum vulgare ssp. vulgare (Apiaceae): chemical composition and biological activity. Nat. Prod. Res. 28, 1819-1825.
Raghavan, S., 2006. Handbook of spices, seasonings, and flavorings. CRC Press. Reddy, J.N., 1993. An introduction to the finite element method, McGraw-Hill.
Reverchon, E., Daghero, J., Marrone, C., Mattea, M., Poletto, M., 1999. Supercritical fractional extraction of fennel seed oil and essential oil: experiments and mathematical modeling. Ind. Eng. Chem. Res. 38, 3069-3075.
Rodríguez-Solana, R., Salgado, J.M., Domínguez, J.M., Cortés-Diéguez, S., 2014a. Characterization of fennel extracts and quantification of estragole: Optimization and comparison of accelerated solvent extraction and Soxhlet techniques. Ind. Crops Prod. 52, 528-536.
Rodríguez-Solana, R., Salgado, J.M., Domínguez, J.M., Cortés-Diéguez, S., 2014b. Estragole quantity optimization from fennel seeds by supercritical fluid extraction (carbon dioxide– methanol) using a Box–Behnken design. Characterization of fennel extracts. Ind. Crops Prod. 60, 186-192.
Simandi B., Deak A., Ronyai E., 1999. Supercritical Carbon Dioxide Extraction and Fractionation of fennel Oil. Journal of Agricultural and Food Chemistry, 47, 1635−1640. Valderrama, J.O. and Alarcón, R.F., 2009. A novel hybrid numerical technique to determine mass transport properties in supercritical fluid extraction processes. IJNMBE 25(2), 173-184.
Wilkinson, N., Hilton, R., Hendry, D., Venkitasamy, C., Jacoby, W., 2014. Study of process variables in supercritical carbon dioxide extraction of soybeans. Food Sci. Technol. Int. 20(1), 63-70.
Yahya, F., Lu, T., Santos, R.C.D., Fryer, P.J., Bakalis, S., 2010. Supercritical carbon dioxide and solvent extraction of 2-acetyl-1-pyrroline from Pandan leaf: The effect of pre-treatment. J. Supercrit. Fluids 55, 200–207.
Yamini, Y., Sefidkon, F., Pourmortazavi, S. M., 2002. Comparison of essential oil composition of Iranian fennel (Foeniculum vulgare) obtained by supercritical carbon dioxide extraction and hydrodistillation methods. Flavour Fragr. J. 17(5), 345-348.
CHAPTER 3
EFFECTS OF GRINDING TIME ON SUPERCRITICAL FLUID EXTRACTION
___________________________________
INVESTIGATING THE EFFECTS OF GRINDING TIME AND GRINDING LOAD ON CONTENT OF TERPENES IN EXTRACT FROM FENNEL OBTAINED BY
SUPERCRITICAL FLUID EXTRACTION
Tahmasb Hatami, Júlio Cezar Flores Johner, Maria Angela de Almeida Meireles
LASEFI/DEA/FEA (School of Food Engineering), UNICAMP (University of Campinas), Campinas, SP, Brazil
Paper published in Industrial Crops & Products, 109: 85–91, Apr.-Aug. 2017.
Industrial Crops & Products
journal homepage:www.elsevier.com/locate/indcrop
Investigating the e
ffects of grinding time and grinding load on content of
terpenes in extract from fennel obtained by supercritical
fluid extraction
Tahmasb Hatamia,b,⁎, Júlio Cezar Flores Johnera, M. Angela A. Meirelesa aLASEFI/DEA/FEA (School of Food Engineering), UNICAMP (University of Campinas), Campinas, Brazil
bDepartment of Chemical Engineering, Faculty of Engineering, University of Kurdistan, 66177 Sanandaj, Iran
A R T I C L E I N F O Keywords: Anethole Fenchone Fennel seeds Grinding effect
Supercriticalfluid extraction
A B S T R A C T
This paper investigated effects of grinding time (GT) and mass of raw material in mill (ms) on both global SFE
yield from Fennel and its main volatile oil content namely Anethol and Fenchone. For this purpose, extractor of SFE equipment wasfilled with milled Fennel obtained at various values of ms, from 15 g to 35 g, and GT, from
15 s to 20 min. Extractor was subjected to pressure of 200 bar, temperature of 313 K, and supercritical CO2flow
rate of 1.67 × 10−4kg/s for 10 min. Then, extract composition was evaluated by Gas Chromatography (GC) analysis. Moreover, for better understanding how GT and msaffect SFE yield and extract composition, their
effects were initially investigated on temperature raising and diameter of Fennel seeds during grinding process. It was found that msand GT have considerable effects on Anethole and Fenchone content of Fennel extract.
1. Introduction
Fennel (Foeniculum vulgare) is a plant belonging to Apiaceae fa-mily, which is cultivated in several countries like Brazil, England, Germany, China and so on (Brender et al., 1997). Fennel extracts can be employed as antispasmodic, anti-inflammatory, expectorant, diuretic, and laxative (Jahromi et al., 2003). It also has applications in treatment of nervous disturbances, carminative, analgesic, and stimulant of gas-trointestinal mobility (Jahromi et al., 2003). Anethole and Fenchone are two of the main ingredients in Fennel volatile oil that compose, respectively, 40–70% and 1–20% of it (Bernath et al., 1996; Coşge et al., 2008; Raghavan, 2006). Extraction of volatile oil from Fennel is generally carried out by several techniques such as SFE, liquid CO2
extraction, Soxhlet extraction, accelerated solvent extraction, and steam distillation (Baby and Ranganathan, 2016; Rodríguez-Solana et al., 2014a,b; Bodsgard et al., 2016; Johner and Meireles, 2016). From them, SFE is usually a preferable technique due to its advantages such as high extraction performance, simple separation of solvent from ex-tract, and its selectivity capability (Durante et al., 2014; Ding et al., 2017). SFE from Fennel have been reported in various research works. Moura et al. (2005)studied effect of harvesting season, degree of ma-turation, bed geometry, operating temperature and pressure on SFE yield from fennel. They also studied extraction of Fennel by hydro-distillation and low-pressure solvent extraction, and compared their results with SFE. They found that not only SFE process produced larger relative proportion of anethole and fenchone, but also its overall
efficiency was 5.2 larger than that of hydrodistillation (Moura et al., 2005). In another relevant paper, Pereira and Meireles (2007) in-vestigated economic analysis for obtaining extracts and essential oils from Rosemary, Fennel, and Anise using SFE and steam distillation. They concluded that in spite of high cost of SFE equipment, it was more economical than steam distillation due to higher quality of its product, higher extraction yield, and lower energy consumption (Pereira and Meireles, 2007). Another paper in this topic was written byHammouda et al. (2014), whom studied extraction yield and extract quality from Fennel using SFE, microwave-assisted extraction (MAE), and hydro-distillation. Their study showed that MAE gave higher overall yield and higher percentage of Fenchone than others. SFE, on the other side, gave the maximum percentage of Anethol (Hammouda et al., 2014). In an-other interesting paper,Johner and Meireles (2016)constructed a la-boratory SFE unit that contained one extractor and two separators. They validated the equipment using SFE from Annatto and Fennel. Fennel extract was obtained by employing 200 bar pressure and 313 K temperature in extractor, 80 bar and 312 K infirst separator, 20 bar and 279 K in second separator, massflow rate of 12 g/min, and solvent per feed ratio of 10. Their results indicated an overall SFE yield of 2.8 g extract/100 g of ground seeds. Moreover, they observed that 97.5% of the whole extract was collected in the first separator (Johner and Meireles, 2016).Reverchon et al. (1999)carried out successfully ex-traction of fennel seeds in two steps including SFE at 90 bar and 50 °C, and SFE at 200 bar and 40 °C using three CO2massflow rates of 0.5,
1.0, and 1.5 kg/h. They also modeled the process based on mass
http://dx.doi.org/10.1016/j.indcrop.2017.08.010
Received 16 April 2017; Received in revised form 21 July 2017; Accepted 7 August 2017
⁎Corresponding author at: LASEFI/DEA/FEA (School of Food Engineering), UNICAMP (University of Campinas), Campinas, Brazil.
E-mail address:[email protected](T. Hatami).
Available online 18 August 2017
0926-6690/ © 2017 Elsevier B.V. All rights reserved.
comparing it with experimental data.Piras et al. (2014)employed SFE and hydrodistillation (HD) on Sardinian wild fennel and measured composition of volatile extracts using gas chromatography −mass spectrometry. They found that percentage of the main components in SFE extract were 7.1% (fenchone), 34.9% (estragole), and 24.6% ((E)-anethole), while corresponding number for HD extract were 8.8%, 42.6%, and 43.4%, respectively.Rodríguez-Solana et al. (2014b) per-formed Oleoresin extraction from fennel seeds using SFE and optimized the process for the aim of attaining maximum estragole per kg of dry plant. They found the optimal operating condition as the pressure of 24 MPa, temperature of 333.15 K, extraction duration of 3.41 h, and methanol percentage of 3%. In this condition, they obtained 1320 ± 260 mg of estragole per kg dry plant.Ivanovic et al. (2014) increased the yield of SFE (increase by up to 1350%) for several plant materials by employing different mechanical pretreatment such as flaking, impact plus shearing, and cutting plus grinding. They found Flaking as the most convenient method for increasing the yield of SFE from fennel seeds.
According to the above literature review, two of the attractive re-search areas in the field of SFE from Fennel are either maximizing overall yield or maximizing Anethole and Fenchone content of the volatile oil. Thefirst necessary step for these goals is, however, grinding the Fennel seeds to increase their specific area. Although the effect of GT was already investigated on the SFE yield of other raw materials, they limited themselves to small GT. For example, Wilkinson et al. (2014)investigated the effect of GT on the SFE yield from soybeans at 48.3 MPa and 80 °C. They placed 60 g of soybeans in a mechanical grinder for different GT from 10 to 60 s. They concluded that increasing the GT enhances the extraction yield due to the reduction of particle sizes. The SFE yield was increased from around 6% to 22% by de-creasing the particle diameters from 0.20 mm to 0.07 mm. In another study byYahya et al. (2010), SFE yield from Pandan leaf increased up to 50% after a pretreatment grinding for 30 s. Grosso et al. (2008) evaluated the effects of mean particle size (0.4, 0.6 and 0.8 mm) to-gether with the effects of pressure, temperature, and CO2flow rate on
the yield and composition of SFE extract from Italian coriander seeds. They found that a decrease in particle size didn’t have a considerable effect on the SFE volatiles composition, but it increased the SFE yield as more ducts were destroyed with longer milling time. Taking into ac-count the yield and composition of the extract, they found the best operating conditions to be the pressure of 90 bar, temperature of 40 °C, CO2flow rate of 1.10 kg/h, and mean particle size of 0.6 mm.Shrigod
et al. (2017)carried out SFE of mint leaves, and they investigated the effects of temperature (35–55 8C), pressure (100–300 bar), extraction time (20–90 min), and particle size (0.2–1.0 mm) on both SFE yield and carvone content in volatile oil. They found that SFE yield was mainly influenced by particle size followed by pressure, temperature, and ex-traction time, however, carvone content in extract was mostly affected by pressure followed by particle size and extraction time. The effect of particle size in SFE process was also studied bySodeifian et al. (2016) andChougle et al. (2016). Nevertheless, as the effect of milling process on yield and quality of SFE from Fennel were not discussed in literature, the current study aimed to focus on this area for a board range of GT and various ms. Using higher GT not only affects the particle sizes, but it
also heats up the raw materials and probably affects volatile compo-nents.
2. Material and methods
This section is organized as follows. First in subsection2.1, the raw material and its pretreatment process are presented. In order to con-ceptual understanding how msand GT affects the SFE yield and extract
composition, their effects should be firstly investigated on the tem-perature raising and diameter of Fennel seeds during grinding process. The method for doing this investigation is fully explained in subsection
2.2. Then, in subsection2.3, the SFE equipment as well as the experi-ments procedure is discussed. Finally, a short description about GC analysis is given in subsection2.4.
2.1. Sample preparation
Dried Fennel seeds were supplied from a municipal market, called “Temperos Brasil”, in Campinas, São Paulo, Brazil, and they were kept in a domestic freezer at 255 K. Prior to each grinding experiment, the raw material were taken out from the freezer to stabilize at the la-boratory temperature, 297 K.
2.2. Grinding raw material
The Fennel seeds were ground in a mill (Marconi, model: MA 340, São Paulo, Brazil), which is shown inFig. 1. Its main parts are a rotor, a crushing chamber, a collector container, and stainless steel knives (cutting edge). It has weight of 58 kg, dimensions of 27 × 48 × 50 cm, electrical power of 1600 W, and afixed speed rotor of 1750 rpm.
An initial study was performed by using the Mill to determine the influence of msand GT on physical properties of Fennel. For this
pur-pose,five levels of GT and three levels of mswere considered. These
levels are 15 s, 2 min, 6 min, 12 min, and 20 min for GT, and 15 g, 25 g, and 35 g for ms. Each grinding process was performed two times to
ensure that the obtained results are reliable. At the end of each run, Fennel temperatures were measured from the top of the crushing chamber by using an infrared thermometer with an uncertainty of 0.1 K. The idea of measuring the Fennel temperature in the central parts of the crushing chamber was not applicable as opening this chamber, for this purpose, took several seconds and, during this period, tem-perature decreased quickly. In the next step of the experiment, the milled Fennel was subjected to a vibratory agitator and sieves (Bertel, model MAGNETICO, Sao Paulo, Brazil) to determine the particle size distribution. In this step, six sieves with mesh sizes of 18, 25, 35, 50, 80, and 100 were employed, and they were vibrated for 15 min to ensure that the material in each sieve didn’t change with time. After that, materials on each sieve and the bottom pan were accurately weighed and recorded. For calculating the mean particle diameter, the Standard ASAE method was used (Standard, 2003).
Fig. 1. Schematic diagram of the Mill.
2.3. SFE from fennel
A schematic diagram of the employed SFE unit is shown inFig. 2, which has total dimensions of 57 × 77 × 115 cm. It has a 100 mL ex-tractor with an internal height per diameter of 19, and two separators each with 90 mL volume. Since extraction from Fennel provides low amount of essential oil (Johner and Meireles, 2016), the mass of oil that remains in the separators, even after recovering the extract oil in the bed, separators, and lines, is significant in comparison with the total mass of extract, and it consequently affects the extraction performance. To overcome this problem, the separators of the SFE unit in the current study were substituted by two glassflasks at atmospheric pressure. The first flask was a separator, but the second flask with cotton inside was used for cleaning the CO2 flow before entering the totalizer.
Char-acteristics of other parts of the SFE equipment such as pump, cooling and heating bath, flow totalize, temperature and pressure indicators, and valves can be found in our previous paper (Johner and Meireles, 2016).
In a typical SFE experiment, the thermostatic bath is turned on one hour before doing the extraction in order to ensure that the system reaches the desired temperature, 313 K. The extractor is then charged with 10 g of milled Fennel. Noticeably, the subjected milled Fennel to the vibratory agitator was not used for SFE as it was possible that
partials of volatile oil evaporated during agitation. In fact, the Fennel seeds for SFE werefirst ground in the mill, and then directly put in the extractor as we had already measured their size distribution separately. This amount of milled Fennel occupies small part of the extractor, and the remaining space isfilled with small glass beads. Next, the pump is turned on to pressurize the system up to the desired pressure, 200 bar. It is required to keep the system in this situation for 10 min before opening the exit valve of the extractor. This 10 min is called static time and it is employed to ensure that the supercriticalfluid reach equili-brium with solid phase. The overall SFE yield is evaluated by collecting and weighing the extract samples at the end of each run. To determine the effect of GT and mson the quality and efficiency of SFE, it is
ne-cessary to perform the experiment with milled Fennel obtained at various values of GT and ms. Each SFE run is performed two times to
ensure that the obtained results are reliable. 2.4. Chromatographic analysis
The compositions of Anethol and Fenchone in the extract were de-termined by using a GC withflame ionization (GC-FID) (SHIMADZU, CG 17-A, Kyoto, Japan) equipped with a fused-silica capillary column ZB-5 (length of 30 m, inner diameter of 0.25 mm, andfilm thickness of 0.25μm, Zebron, USA). For this purpose, the analyzable solution was
2016).
obtained by dissolving 10 mg of extract in 10 mL of ethyl acetate. The carrier gas in GC was helium (99.9% purity, White Martins, Campinas, Brazil) at a totalflow of 26 mL/min and column flow rate of 1.11 mL/ min. Split injection conducted with an injection volume of 1μL and split ratio of 20. The temperature of injector was 493 K, the tempera-ture of detector was 513 K, and the initial temperatempera-ture of column was 333 K. Based on a defined program, the column was heated from 333 K to 513 K at 3 K/min, and then held for 2 min.
In order to measure the amount of Anethol and Fenchone in the extract, it wasfirst required to obtain the calibration curve for both of them. The analyzable solutions, for this purpose, were obtained by dissolving various masses of Anethol (purity: 99%, SIGMA-ALDRICH) and Fenchone (purity ≥98%, SIGMA-ALDRICH) in 10 mL of ethyl acetate, and analyze them with GC.
3. Results and discussion
The average size of Fennel particles with respect to GT and msis
presented inFig. 3. In thisfigure, three distinct regions can be identi-fied. In region l, which is from 15 s to 2 min, the size of particles dropped dramatically with increasing GT, while for region 2, which is from 2 min to 12 min, the size of particles decreased moderately. The size of particles for the last part of the curves, region 3, is approximately constant. As depicted in Fig. 3, this trend is rather similar for three material load, 15 g, 25 g, and 35 g, examined in this study. For the case of 15 g Fennel, the average diameter of particles decreased from 0.43 mm at 15 s to 0.35 mm at 20 min. For the same GT period, the average particles diameter of 35 g Fennel was dropped by 0.11 mm and it leveled off at 0.37 mm. The curve of 25 g Fennel located between the two aforementioned curves.
Fig. 4shows the raising temperature of Fennel at the end of grinding process for various values of GT and ms. It is clear from thisfigure that,
for each value of ms, the temperature increased significantly as the
grinding process proceeds. What’s more, the temperature raising is also affected considerably by the value of ms, and it changed from around
288 K for ms= 15 g to just under 302 K for ms= 35 g. In fact, higher
amount of material inside the mill causes higher friction among them or, in the other words, higher conversion of kinematic energy of par-ticles to internal energy that it consequently leads to more temperature raising. It is worthwhile emphasizing once more that the reported data inFig. 4are not the average temperature raising of Fennel inside the mill, but in fact, they are the temperature raising of material located near the top of the crushing chamber. Evidently, there was a gradient temperature inside the mill so that the material close to the cutting edges was often hotter than the other parts. Thus, the real temperatures raising of material are higher than that of reported inFig. 4.
Material distribution inside the mill is depicted inFig. 5for GT of
15 s and 20 min and msof 15 g and 35 g. These pictures clearly indicate
that as grinding continues, the raw material are moved from the round body of the mill to the cutting edges. It also illustrates that higher percentage of material for the case of ms= 15 g and GT = 20 min
lo-cated close to the cutting edges when it compare with that of ms= 35 g
and GT = 20 min. This concludes that the reported data inFig. 4are more reliable for ms= 35 g and GT = 20 min than ms= 15 g and the
same GT, and the real temperature raising of Fennel for ms= 15 g was
much higher than that ofFig. 4. Probably, the average temperature raising of material for the case of ms= 15 g and GT = 20 min was
higher than that of ms= 35 g and GT = 20 min.
After grinding the raw material, SFE from Fennel was performed using the home-made SFE equipment (Johner and Meireles, 2016). From the whole ms-GT sets in the grinding experiments, three levels of
GT (15 s, 6 min, and 20 min) and two levels of ms(15 g and 35 g) were
chosen for SFE experiments. The reason for this selection was that, as shown inFigs. 3 and 4, employing these sets of ms-GT produced milled
Fennel with clearly different particles size and different temperature raising, and thus it would be possible that they gave extract with dif-ferent volatile oil compositions. Each SFE experiment was performed two times to guarantee the reliability of the results.
Overall extraction yields for ms= 15 g and 35 g are presented in
Fig. 6for GT from 15 s to 20 min. According to thisfigure, increasing GT, for ms= 35 g, leaded to increasing the overall extraction yield. By
contrast, increasing the GT, for ms= 15 g,firstly, raised and then
re-duced the extraction yield. The reason for this phenomenon was that increasing GT affected the extraction yield in two opposite ways. On one hand, the particles diameter decreased according toFig. 3, which it, in turn, had a positive effect on extraction yield due to improving the specific area of particles in the SFE bed. On the other hand, the material temperature in the mill increased according to Fig. 4, and this ac-celerated the evaporating of volatile compound that consequently tended to reduce the SFE yield. Temperature raising, at small to mod-erate values of GT, was not too much, and the particle diameter was the key factor in SFE yield. In this range of GT, as particles diameter for ms= 15 g was smaller than that of ms= 35 g, the SFE yield for
ms= 15 g was higher. At higher values of GT, the situation was
com-pletely different. Despite the small particles size produced in higher GT, the extraction yield did not necessarily increase due to the significant temperature raising and evaporation of volatile compound. For the case of ms= 15 g in higher GT, the temperature raising was the prominent
factor due to the fact that higher percentage of material located close to the cutting edges (Fig. 5), and it, as mentioned, increased the Fennel temperature even much higher than that of shown inFig. 4. For the case of ms= 35 g in higher GT, the particle diameter was still the prominent
factor, and so the extraction yield continued its ascending trend,
0 5 10 15 20 0.32 0.34 0.36 0.38 0.4 0.42 0.44 0.46 0.48 ms = 25g ms = 35g
Fig. 3. The average size of Fennel particles at various values of GT and ms.
0 5 10 15 20 0 5 10 15 20 25 30 ms = 25g ms = 35g
Fig. 4. The raising temperature of Fennel at the end of grinding process.
however, with lower slope due to the evaporation of volatile com-pound. The highest extraction yield of 51.14 and 49.34 mg of extract/g of Fennel were achieved by grinding, respectively, 15 g of raw material for 6 min and 35 g of raw material for 20 min.
Based on GC analysis of extract and using the calibration curves, the effects of GT and mson the Anethol and Fenchone extraction yield are
depicted, respectively, inFigs. 7 and 8. It should be noted that there are error bars on these twofigures, but they are so small that are not seen. Referring to Fig. 7, the Anethol extraction yield increased with in-creasing GT, initially, and then decreased with further inin-creasing GT after reaching the maximum yield of around 6.19 mg of Anethol/g of
Fennel. It can be also interpreted from thisfigure that the effect of in-creasing msfrom 15 g to 35 g on the Anethol extraction yield at small,
moderate, and high values of GT is, respectively, negative, insignificant, and positive. Based onFig. 8, the effect of msin Fenchone yield is
al-most negligible at small and high values of GT, while its effect for the moderate value of GT (6 min) is considerable, which gives the yield of 0.29 mg Fenchone/g Fennel for ms= 15 g and 0.2 mg Fenchone/g
Fennel for ms= 35 g. The difference between trends of Anethol and
Fenchone extraction yield is mainly due to the differences between their Enthalpy of vaporization, which is 61.90 kJ/mol for Anethol (https://www.chemeo.com/cid/44-213-6/Anethole, 2016) and 0 5 10 15 20 30 35 40 45 50 ms = 15g ms = 35g
Fig. 6. Effect of GT and mson the overall extraction yield obtained by SFE from Fennel at
200 bar, 313 K, and 1.67 × 10−4kg/s during 10 min.
0 5 10 15 20 1 2 3 4 5 6 ms = 15g ms = 35g
Fig. 7. Effect of GT and mson the Anethol extraction yield obtained by SFE from Fennel
at 200 bar, 313 K, and 1.67 × 10−4kg/s, during 10 min.