Citrus Essential Oils E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 608

Veröffentlichungsjahr: 2011

Beschreibung

Commercially used for food flavorings, toiletry products, cosmetics, and perfumes, among others, citrus essential oil has recently been applied physiologically, like for chemoprevention against cancer and in aromatherapy.  Citrus Essential Oils: Flavor and Fragrance presents an overview of citrus essential oils, covering the basics, methodology, and applications involved in recent topics of citrus essential oils research. The concepts, analytical methods, and properties of these oils are described and the chapters detail techniques for oil extraction, compositional analysis, functional properties, and industrial uses. This book is an unparalleled resource for food and flavor scientists and chemists.

Leseprobe

Table of Contents

Cover

Table of Contents

Title page

Copyright page

PREFACE

CONTRIBUTORS

1 INTRODUCTION AND OVERVIEW

2 TECHNIQUES FOR OIL EXTRACTION

2.1 STEAM AND HYDRODISTILLATION

2.2 SOLVENT- AND WATER-FREE MICROWAVE EXTRACTION

2.3 ULTRASOUND-ACCELERATED SOLVENT EXTRACTION

2.4 SOLID-PHASE MICROEXTRACTION

2.5 COLD PRESSING

3 COMPOSITIONAL ANALYSIS

3.1 ANALYTICAL METHOD: GC-FID, GC-MS, AND GC × GC

3.2 AFRICA

3.3 THE AMERICAS?

3.4 ASIA

3.5 EUROPE

4 ENANTIOMERIC AND STABLE ISOTOPE ANALYSIS

4.1 ENANTIOMERIC ANALYSIS

4.2 STABLE ISOTOPE RATIO ANALYSIS

4.3 APPLICATION IN AUTHENTICITY CONTROL OF ESSENTIAL OIL FROM DIFFERENT ORIGINS

5 GAS CHROMATOGRAPHY–OLFACTOMETRY AND AROMA-ACTIVE COMPONENTS IN CITRUS ESSENTIAL OILS

5.1 GAS CHROMATOGRAPHY–OLFACTOMETRY

5.2 FLAVOR AND ODOR/AROMA IMPACT COMPOUNDS IN CITRUS ESSENTIAL OILS

5.3 FUNCTIONAL GROUPS RELATED TO CITRUS FLAVOR ACTIVITY

5.4 PROSPECTS FOR GC-O

5.5 CLOSING REMARKS

6 FUNCTIONAL PROPERTIES

6.1 ANTIOXIDATIVE ACTIVITY

6.2 INHIBITORY FORMATION OF CARCINOGEN

6.3 ANTIMICROBIOLOGY

7 AROMATHERAPY

7.1 APPLICATION FOR THERAPEUTIC EFFECT

7.2 AGEING OF ESSENTIAL OILS

8 INDUSTRIAL VIEW

8.1 FORMULATION OF ESSENTIAL OILS FOR PROCESSED FOODS: PRODUCTION, TREND, AND MICROCAPSULATION

8.2 ECO-CONSCIOUS SYSTEM OF OIL EXTRACTION FROM CITRUS PEEL WASTES

Index

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Published simultaneously in Canada.

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Library of Congress Cataloging-in-Publication Data:

Citrus essential oils : flavor and fragrance / edited by Masayoshi Sawamura.

p. cm.

 ISBN 978-0-470-37218-0 (cloth)

 ISBN 978-1-118-07438-1 (epub)

 1. Citrus oils. I. Sawamura, Masayoshi.

 TP959.C54C58 2010

 661′.806—dc22

2009045874

PREFACE

Masayoshi Sawamura

Today, citrus fruit is widely grown from temperate to tropical zones in the northern and southern hemispheres. Citrus fruit has been first ranked in the annual amount of world fruit production since 1992, meaning that it is the favorite type of fruit worldwide. It has pleasant taste and aroma, and is also an important source of vitamin C. Essential oil of citrus fruit is intensively accumulated in oil glands of the peel, accounting for approximately 1% of fruit weight on average. Citrus essential oil is also the most popular of natural essential oils. The oil is commercially used for food flavorings, toiletry products, cosmetics, perfumes, and so forth. Recently, citrus essential oil has been known not only for its aromatic functions, but also for its physiological properties, such as chemoprevention against cancer and aromatherapy effects. There are more than 10,000 varieties of citrus fruit. However, many citrus varieties are not familiar to us. Each aroma is unique and quite different even among those varieties. There has been lack of information on the overall characteristics of the Citrus genus. Citrus fruit is an important aromatic resource and its value will increase in the future. There is much useful information to be gleaned about the creative aromatic character and functional properties. This book provides an overview of citrus essential oils from various aspects covering basic and methodological application and recent topics of citrus essential oils research.

We hope that this book will provide inspiration and creative ideas for flavor and fragrance professionals and researchers. The book is intended for professionals as well as advanced students active in the food sciences, flavor chemistry, and aromatherapy. We believe our readers would benefit from a book that describes concepts, analytical methods, and diverse properties.

I owe a debt of gratitude to all the authors of this volume, who are leading specialists in their fields.

CONTRIBUTORS

Prof. Farid Chemat Université d’Avignon et des Pays de Vaucluse, UMR A 408 INRA-UPAV, 84000 Avignon, France

Hyang-Sook Choi, Ph.D. Asst. Prof., Department of Food Nutrition and Culinary Art, Kyungin Women’s College, 101 Gyesangil Kyeyanggu, Inchon 407-740, Korea

Dr. Hisakatsu Iwabuchi San-Ei Gen F.F.I., Inc., 1-1-11 Sanwa-cho, Toyonaka, Osaka 561-8588, Japan

Dr. Takehiro Kashiwagi Assoc. Prof., Major of Food Science, Faculty of Agriculture, Kochi University, B-200 Monobe, Nankoku, Kochi 783-8502, Japan

Dr. Chizu Kumagai Palliative Care Unit, Municipal Ida Hospital, City of Kawasaki 2-27-1 Ida, Nakahara-ku, Kawasaki, Kanagawa, Japan 211-0035

Nguyen Thi Lan-Phi, Ph.D. Faculty of Chemical Engineering, Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Vietnam

Nguyen Thi Minh-Tu, Ph.D. Institute of Biological and Food Technology, Hanoi University of Technology, 1 Dai Co, Viet Road, Hanoi, Vietnam

Simon Muhoho Njoroge, Ph.D. Assoc. Prof., Department of Food Science and Technology, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya

Prof. Marco Poiana Dipartimento di Biotecnologie per il Monitoraggio Agroalimentare ed Ambientale, Facoltà di Agraria, Università Degli Studi di Reggio Calabria, 89124, Reggio Calabria, Italy

Dr. Atsushi Satake Research and Development Center, Nagaoka Perfumary Co. Ltd., 1-3-30, Itsukaichi, Ibaraki, Osaka 567-0005, Japan

Prof. Masayoshi Sawamura Tosa Food Business Creator Project Team, Kochi University, B-200 Monobe, Nankoku, Kochi 783-8502, Japan

Masaki Shimada, M.Eng. San-Ei Gen F.F.I., Inc., 1-1-11 Sanwa-cho, Toyonaka, Osaka 561-8588, Japan

U-Sun Son, M.Agr. Flavor Part/Scent Berry Perfume House, LG Household & Health Care Ltd., Seoul National University, San 56-1, Silim-dong, Gwanak-gu, Seoul 151-742, Korea

Hee-Sun Song, Ph.D. Assoc. Prof., Department of Food and Nutrition, Gwangju Health College, 688-3, Shinchang-dong, Gwangsan-gu, GwangJu, 506-701, Korea

Nguyen Thi Thao, Ph.D. Institute of Biological and Food Technology, Hanoi University of Technology, 1 Dai Co, Viet Road, Hanoi, Vietnam

Prof. C. Hanny Wijaya Department of Food Science and Technology, Faculty of Agricultural Technology, Bogor Agricultural University, Kampus IPB Damaga, Bogor 16002, Indonesia

Xiaolin Yu, M.Agr. Assoc. Prof., Department of Food Science, South China Agricultural University, Wushan, Guangzhou 510642, China

Dr. Chiyoki Yukawa San-Ei Gen F.F.I., Inc., 1-1-11 Sanwa-cho, Toyonaka, Osaka 561-8588, Japan

1

INTRODUCTION AND OVERVIEW

Masayoshi Sawamura

Kochi UniversityKochi, Japan

There are a great number of Citrus varieties widely distributed in the world. It is said that the Citrus genus originated near Assam in India about 30 or 40 million years ago (Iwamasa, 1976). The Citrus fruits that spread to the West migrated to the Middle East and the Mediterranean, crossed the Atlantic Ocean, and finally reached America via the West Indies. Others, spreading to the East, migrated to Thailand, Malaysia, China and other Southeast Asian countries. Nowadays, most citrus fruits are grown extensively in the temperate and tropical zones of the northern and southern hemispheres.

Citrus can be propagated and new varieties can be produced by asexual nuclear or chance seedlings, by crossing, and by mutation. In addition to these natural forms of propagation, many new artificially crossed cultivars have been created by Citrus breeders. The classification of this expanding family is complex and is becoming confused. The best-known taxonomies of genus Citrus are those of Swingle (1943) and Tanaka (1969a,b). These two taxonomies differ greatly in the number of species admitted: Swingle identified 16 species, Tanaka 159. Although the basic concept underlying the two taxonomies is different, assignment is almost the same.

The four major fruit types commercially produced worldwide are citrus fruit, bananas, apples and grapes, followed by pears, peaches, and plums. Citrus fruit finally replaced grapes as the world’s most-produced fruit in 1991. The recent production volume of major fruits is shown in Figure 1.1. The production of citrus fruit accounts for more than 65% of fruits produced. The total world production of citrus fruit in 2008 was about 79.6 million tons; major citrus-producing countries are shown in Figure 1.2. The greatest producer is China, followed by Brazil, the United States, the EU, Mexico, and Turkey. Citrus essential oils have also long been the most popular source of perfume and fragrance essences. There are four reasons why citrus fruit is the most popular fruit in the world: (1) good sour and sweet tastes; (2) pleasant, refreshing aroma; (3) good source of vitamin C; and (4) extensive growing areas worldwide. There are two categories of citrus fruit in terms of food chemistry: sweet citrus fruit, with a sugar/acid ratio of approximately 10, and sour citrus fruit, with a ratio of less than 1. Sweet citrus fruit such as orange, grapefruit, Satsuma mandarin, and pummelo are popular varieties. Sour citrus fruit, on the other hand, such as lemon, lime, bergamot, and yuzu, are less produced, but they are popular in culinary materials such as fruit juice vinegar, and their essential oils are also frequently used in flavoring, cosmetics, and perfume.

Figure 1.1. Worldwide production of major fruits.

Figure 1.2. Major citrus fruits production in 2007.

The aim of flavor or aroma research is to determine a fruit’s composition, aroma characteristics, functionality, and industrial or commercial value. The concept of flavor research is outlined in Figure 1.3. First, essential oil is extracted from raw material such as citrus fruits. Then, aroma samples are analyzed using modern instruments, organoleptic procedures, and/or mechanical sensors. The resulting information can give a detailed understanding of the fruit and can be used in further studies of aroma or flavor.

Figure 1.3. Flowchart of flavor research.

The Citrus genus is said to have more than 10,000 varieties and to be produced more than any other kind of fruit in the world. Citrus essential oils account for the largest proportion of commercial natural flavors and fragrances. Essential oils from citrus peel are natural flavoring materials of commercial importance. They have been used in beverages, confectioneries, pharmaceuticals, cosmetics, and perfumes. The quality, freshness, and uniqueness of citrus oils are major factors contributing to their value and application. Citrus fruits, with their unique and attractive individual aromas, are popularly accepted worldwide, and citrus essential oils are a large and important aroma resource. Quantitative data concerning the volatile components of a number of citrus essential oils (Shaw, 1979; Sawamura, 2000) and their wide commercial use are presented in this book.

The twenty-first century has been referred to as “the era of fragrance.” We live in an atmosphere greatly enriched by aromas and fragrances. Everyday items such as fresh and cooked foods, perfumes, cosmetic and toiletry goods, medicines, and insecticides contain natural or artificial fragrances. Aroma commonly gives us a strong impact in trace amounts. The characteristic odor of an individual substance is composed of roughly a thousand compounds. It is almost impossible to blend every compound of an odor in the exact proportion required to reconstruct the original. It has been determined, however, that there are usually one or two or a few key compounds that can accurately simulate the original odor. One goal of flavor research is to elucidate key aroma compounds by means of a combination of instrumental and organoleptic analyses. Many flavor researchers have tried to find the key aroma compounds of various kinds of citrus. Gas chromatography–olfactomery (GC-O) is a superior method for such studies (Acree, 1993).

Aroma is one of the functional properties of food because aroma compounds stimulate us physically and physiologically (this is referred to as organoleptic effects). A great number of aroma compounds have been identified in a variety of foods to date. Such studies have been a major theme in flavor research. Aroma compounds have a number of properties other than odor production, including antibiotic, deodorant, and blood vessel stimulation. Aromatherapeutic effect also falls into this category. Antioxidants have been investigated most intensively as constituents preventing diseases associated with oxidative damage, and decreasing lipid oxidation during the processing and storage of seafood (Pisano, 1986). Synthetic antioxidants such as butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), and propyl gallate (PG) are used as food additives to inhibit the actions of toxic and carcinogenic substances (Chang et al., 1977). Natural antioxidants from natural foods such as herbs (Boyd et al., 1993; Pizzocaro et al., 1994), vegetables (Tsushida et al., 1994; Vinson et al., 1998), fruits (Nogata et al., 1996), oilseeds (Medina et al., 1999), spices (Shahidi et al., 1994), green tea (Amarowicz and Shahidi, 1996), and cereals (Hendelman et al., 1999) have been studied, and some of them, such as ascorbate and tocopherols, are currently used in a variety of food products. In recent reports much attention has been given to citrus components, since they present various pharmaceutical activities including anticarcinogenicity, antimutagenicity, antioxidative activity, antiaging, and radical-scavenging (Nogata et al., 1996; Rapisarda et al., 1999; Choi et al., 2000; Sawamura et al., 1999, 2005). Grapefruit oil and lemon extracts have been suggested as effective natural antioxidative compounds (Tokoro, 1997). It has been recently discovered that some foods or foodstuffs serve to inhibit the formation of carcinogens. Essential oils containing terpenoids are well known to have some physiological and pharmaceutical effects, and it is known that citrus essential oils have antimicrobiological (Griffin et al., 1999) and chemopreventive properties (Crowell, 1997; Gould, 1997; Kawaii et al., 1999). The major component of citrus essential oils is terpenes, whose basic structure is isoprenoid (C5H8). The most typical terpenes are limonene, citrus-like odor; γ-terpinene, waxy; terpinolene, green; α-pinene and β-pinene, pine-like. These compounds have been reported to inhibit the growth of cancer cells. One carcinogen, nitrosodimethylamine, which is formed with dimethylamine and nitrite in an acidic condition, has been noted in this regard. Dimethylamine and nitrite are commonly present in meats and vegetables, respectively. It was suggested that some foods or foodstuffs might contain cancer-inhibitory and -preventive compounds as well as cancer-inducing substances (Sawamura et al., 1999, 2005).

Aromatherapy, a medical treatment intended to stimulate or calm the mind, is an applied therapy using the functional properties of essential oils. A variety of vegetable essential oils have been widely used in aromatherapy. Essential oils are extracted from the flowers, leaves, stems, roots, and fruits of various plants and purified for commercial use. Aromatherapy originated in Europe in the eighteenth century and has grown popular in many countries recently, but the most famous essential oil products are still produced in Europe. There are currently seven kinds of commercial citrus essential oils used in aromatherapy: orange, mandarin, lemon, lime, bergamot, grapefruit, and neroli. Yuzu (Citrus junos Sieb. ex Tanaka), a typical Japanese sour citrus fruit, has attracted the interest of aroma therapists over the past ten years. Recently, the effect of yuzu essential oil on the autonomic nervous system has been studied (Sawamura et al., 2009). It is expected that yuzu essential oil will soon be adopted for use in aromatherapy. One obstacle to such application for aromatherapy is that the composition of essential oils changes readily. It has been pointed out that the composition of yuzu (Njoroge et al., 1996) and lemon essential oils (Sawamura et al., 2004) can change considerably under different storage conditions. It is important to carefully consider quality change in commercial essential oil products intended for therapeutic use. This book presents a few attractive studies of functional citrus properties, including aromatherapy.

Recently, food safety or reliability has been a prominent concern, along with food quality. All Japanese foods and products, for example, are controlled under standards such as the European Union regulations regarding food safety and traceability, Japanese Agricultural Standard (JAS), and other regulations governing responsibility to consumers and manufacturers in the United States, Canada, Australia, and England. However, there are few methods for discriminating as to the quality and characteristics of crops from various producing districts. One of the most reliable methods is isotope analysis of food constituents by mass spectrometry. In nature, the isotopes of each element are distributed in a fixed ratio. Plants on the earth first convert solar energy into biochemical energy; the food chain begins with plants. Higher plants fix CO2 by the Calvin-Benson cycle to biosynthesize various organic compounds for their constituents. It is known that the enzyme ribulose-1,5-diphosphate carboxylase differentiates a small mass difference between 12CO2 and 13CO2, when it fixes CO2 in the atmosphere (O’Leary, 1981). This function is referred to as the isotope effect. It is thought that the isotope effect could occur in every enzyme involved in biosynthetic and metabolic pathways. Thus, we can see that this effect should also be applicable to the essential oils comprising terpene compounds. Every species, variety, or strain of a plant has some substantially distinct characteristics. Even among the same cultivars, different growing conditions such as annual atmosphere and moisture, or soil and fertilizers, can bring about small but appreciable differences in composition. Several researchers (Faber et al., 1995; Faulharber et al., 1997; Sawamura et al., 2001; Thao et al., 2007) have tried to distinguish these isotope differences of biological constituents. Some sections of this book discuss methods of verifying the genuineness of food.

Finally, fundamental and academic information about citrus essential oils have contributed to commercial development. In the references section on this chapter, several experts present the reader with attractive topics regarding the wide utilization of citrus essential oils.

REFERENCES

Acree, T.E. (1993). Bioassays for flavor. In: Acree, T.E., Teranishi, R. (eds.), Flavor science. Washington, DC: American Chemical Society, pp. 1–18.

Amarowicz, R., Shahidi, F. (1996). A rapid chromatographic method for separation of individual catechins from green tea. Food Research International 29: 71–76.

Boyd, L.C., Green, D.P., Giesbrecht, F.B., King, M.F. (1993). Inhibition of oxidative rancidity in frozen cooked fish flakes by tert-butylhydroquinone and rosemary extract. Journal of the Science of Food and Agriculture 61: 87–93.

Chang, S.S., Ostric-Matijasevic, B., Hsieh, O.A., Chang, C.L. (1977). Natural antioxidants from rosemary and sage. Journal of Food Science 42: 1102–1106.

Choi, H.S., Song, H.S., Ukeda, H., Sawamura, M. (2000). Radical-scavenging activities of citrus essential oils and their components: Detection using 1,1-diphenyl-2- picrylhydrazyl. Journal of Agricultural and Food Chemistry 48: 4156–4161.

Crowell, P.L. (1997). Monoterpenes in breast cancer chemoprevention. Breast Cancer Research Treatment 46: 191–197.

Faber, B., Krause, B., Dietrich, A., Mosandl, A. (1995). Gas chromatography–isotope ratio mass spectrometry in the analysis of peppermint oil and its importance in the authenticity control. Journal of Essential Oil Research 7: 123–131.

Faulharber, S., Hener, U., Mosandl, A. (1997). GC-IRMS analysis of mandarin essential oils. 2. d13CPDB values of characteristic flavor components. Journal of Agricultural and Food Chemistry 45: 4719–4725.

Gould, M.N. (1997). Cancer chemoprevention and therapy by monoterpenes. Environmental Health Perspectives 105: 977–979.

Griffin, S.G., Wyllie, S.G., Markham, J.L., Leach, D.N. (1999). The role of structure and molecular properties of terpenoids in determining their antimicrobial activity. Flavour Fragrance Journal 14: 322–332.

Hendelman, G.J., Cao, G., Walter, M.F., Nightingale, Z.D., Paul, G.L., Prior, R.L., Blumberg, J.B. (1999). Antioxidant capacity of oat (Avena sativa L.) extracts. 1. Inhibition of low-density lipoprotein oxidation and oxygen radical absorbance capacity. Journal of Agricultural and Food Chemistry 47: 4888–4893.

Iwamasa, M. (1976). Citrus varieties. Shizuoka: Shizuoka Prefectural Citrus Agricultural Cooperative Association, p. 30.

Kawaii, S., Tomono, Y., Katase, E., Ogawa, K., Yano, M. (1999). Quantitation of flavonoid constituents in Citrus fruits. Journal of Agricultural and Food Chemistry 47: 3565–3571.

Medina, I.M., Satué-Gracia, T., German, J.B., Frankel, E.N. (1999). Comparison of natural polyphenol antioxidants from extra virgin olive oil with synthetic antioxidants in tuna lipids during thermal oxidation. Journal of Agricultural and Food Chemistry 47: 4873–4879.

Njoroge, S.M., Ukeda, H., Sawamura, M. (1996). Changes in the volatile composition of yuzu (Citrus junos Tanaka) cold-pressed oil during storage. Journal of Agricultural and Food Chemistry 44: 550–556.

Nogata, Y., Yoza, K., Kusumoto, K., Kohyama, N., Sekiya, K., Ohta, H. (1996). Screening for inhibitory activity of citrus fruit extracts against platelet cyclooxigenase and lipoxigenase. Journal of Agricultural and Food Chemistry 44: 725–729.

O’Leary, M.H. (1981). Carbon isotope fractionation in plants. Phytochemistry 20: 553–567.

Pisano, R.C. (1986). The future of natural essential oils in the flavor and fragrance industry. Perfumer and Flavorist 11: 35–41.

Pizzocaro, F., Senesi, E., Babbini, G. (1994). Protective effect of rosemary and sage on frozen beef hamburgers. Industrie Alimentari 33: 289–294.

Rapisarda, P., Tomaino, A., Lo Cascio, C., Bonina, F., Saijo, A., De Pasquale, A. (1999). Antioxidant effectiveness as influenced by phenolic content of fresh orange juices. Journal of Agricultural and Food Chemistry 47: 4718–4723.

Sawamura, M., Song, H.S., Ozaki, K., Ishikawa, J., Ukeda, H. (1999). Inhibitory effects of citrus essential oils and their components on the formation of N-nitrosodimethylamine. Journal of Agricultural and Food Chemistry 47: 4868–4872.

Sawamura, M. (2000). Volatile components of essential oils of the Citrus genus. In: Pandalai, S.G. (ed.), Recent research developments in agricultural and food chemistry, Vol. 4. Trivandrum, India: Research Signpost, pp. 131–164.

Sawamura, M., Ito, T., Une, A., Ukeda, H., Yamasaki, Y. (2001). Isotope ratio by HRGC-MS of Citrus junos Tanaka (yuzu) essential oils: m/z 137/136 of terpene hydrocarbons. Bioscience, Biotechnology, and Biochemistry 65: 2622–2629.

Sawamura, M., Son, U.S., Choi, H.S., Lee Kim, M.S., Lan Phi, N.T., Fears, M., Kumagai, C. (2004). Compositional changes in commercial lemon essential oil for aromatherapy. International Journal of Aromatherapy 14: 27–36.

Sawamura, M., Wu, Y., Fujiwara, C., Urushibata, M. (2005). Inhibitory effects of yuzu essential oil on the formation of N-nitrosodimethylamine in vegetables. Journal of Agricultural and Food Chemistry 53: 4281–4287.

Sawamura, M., Fukata, J., Kumagai, C., Lan Phi, N.T., Mizushima, N., Hori, N., Wada, M., Kamano, S. (2009). Functional activities of Japanese yuzu essential oil. Japanese Journal of Aromatherapy 9: 1–11.

Shahidi, F., Wanasundara, U.N., Amarowicz, R. (1994). Natural antioxidants from low-pungency mustard flour. Food Research International 27: 489–493.

Shaw, P.E. (1979). Review of quantitative analyses of citrus essential oils. Journal of Agricultural and Food Chemistry 27: 246–257.

Swingle, W.T. (1943). The botany of Citrus and its wild relatives. In: Webber, H.J., Batchelor, L.D. (eds.), The citrus industry, Vol. 1. Berkeley, FL: University of California Press, pp. 190–430.

Tanaka, T. (1969a). Taxonomic problem of citrus fruits in the orient. Bulletin of University of Osaka Prefecture B 21: 133–138.

Tanaka, T. (1969b). Misunderstanding with regard to citrus classification and nomenclature. Bulletin of University of Osaka Prefecture B 21: 139–145.

Thao, N.T., Kashiwagi, T., Sawamura, M. (2007). Characterization by GC-MS of Vietnamese citrus species and hybrids based on the isotope ratio of monoterpene hydrocarbons. Bioscience, Biotechnology, and Biochemistry 71: 2155–2161.

Tokoro, K. (1997). Antioxidants in grapefruit oil. Aromatopia 24: 42–44.

Tsushida, T., Suzuki, M., Kurogi, M. (1994). Evaluation of antioxidant activity of vegetable extracts and determination of some active compounds. Nippon Shokuhin Kogyo Gakkaishi 41: 611–618.

Vinson, J.A., Hao, Y., Su, X., Zubik, L. (1998). Phenol antioxidant quantity and quality in foods: Vegetables. Journal of Agricultural and Food Chemistry 46: 3630–3634.

2

TECHNIQUES FOR OIL EXTRACTION

Farid Chemat

Université d’Avignon Avignon, France

Essential oils have been used probably since the discovery of fire. Egyptians and Phoenicians, Jews, Arabs, Indians, Chinese, Greeks, Romans, and even Mayans and Aztecs all possessed a fragrance culture of great refinement. The Egyptian art of perfumery was preeminent in the civilized antique world, hence the use of aromatic fumigation in religious ceremonies and in mummification. The advent of Christianity and the fall of the Roman Empire caused the art and science of perfumery to move into the Arabic world, where it reached an unequalled level of refinement. During the Middle Ages, the Crusaders introduced the art of alchemy to Europe (Guenther, 1948). The process used by alchemists was the distillation technique using the alambic to produce spirit or Quinta essentia, precisely what we know today as essential oils (French, 1651). Essential oils are also known as volatile oils in contrast to fatty vegetable, animal, and mineral oils. Thus, a drop of essential oil on a piece of cloth or paper disappears within a few minutes or a few days at most, depending on the temperature, which is not the case for fatty oils.

The traditional way of isolating volatile compounds as essential oils from Citrus is performed mostly by cold pressing the Citrus peels. Steam distillation is also used to recover citrus essential oils but principally for production of limonene used as green solvent. Not only are citrus fruits completely used but all of the citrus tree could be valorized, for example, by steam distillation of orange flowers to get neroli oil and the by-product orange flower water. With increasing energy prices, it was not economical to perform steam distillation of citrus leaves and twigs to get petitgrain oil and the by-product eau de brouts (Figure 2.1). Citrus essential oils have been applied in many products such as foods, beverages, cosmetics, and medicines, as flavoring agents as well as for aromatherapy. They are also used for their germicidal, antioxidant, and anticarcinogenic properties (Mukhopadhyay, 2000).

Figure 2.1. Complete valorization of citrus trees.

Essential oils and aromas are complex mixtures of volatile substances generally present at low concentrations. Before such substances can be used or analyzed, they have to be extracted from the plant matrix. Different methods can be used for this purpose (e.g., hydrodistillation, steam distillation, cold pressing, solvent extraction, and simultaneous distillation-extraction). Losses of some volatile compounds, low extraction efficiency, degradation of unsaturated or ester compounds through thermal or hydrolytic effects, and toxic solvent residue in the extract may be encountered using these extraction methods. Citrus essential oils are a mixture of volatile compounds and consist mainly of monoterpene hydrocarbons that possess high levels of unsaturation and are generally unstable due to many factors such as light, heat, oxidation, and hydration. These shortcomings have led to the consideration of the use of new “green” techniques in essential oil extraction, which typically use less solvent and energy, such as microwave extraction, supercritical fluid extraction, ultrasound extraction, and subcritical water extraction. Alternatives to conventional extraction procedures may increase production efficiency and contribute to environmental preservation by reducing the use of solvents and fossil energy and the generation of hazardous substances.