Review
Esntial oils:their antibacterial properties and potential
applications in foods—a review
Sara Burt *
Department of Public Health and Food Safety,Faculty of Veterinary Medicine,University of Utrecht,P .O.Box 80175,
3508TD Utrecht,The Netherlands
Received 14November 2003;accepted 3March 2004
Abstract
In vitro studies have demonstrated antibacterial activity of esntial oils (EOs)against Listeria monocytogenes ,Salmonella typhimurium ,Escherichia coli O157:H7,Shigella dynteria ,Bacillus cereus and Staphylococcus aureus at levels between 0.2and 10A l ml À1.Gram-negative organisms ar
e slightly less susceptible than gram-positive bacteria.A number of EO components has been identified as effective arvacrol,thymol,eugenol,perillaldehyde,cinnamaldehyde and cinnamic acid,having minimum inhibitory concentrations (MICs)of 0.05–5A l ml À1in vitro.A higher concentration is needed to achieve the same effect in foods.Studies with fresh meat,meat products,fish,milk,dairy products,vegetables,fruit and cooked rice have shown that the concentration needed to achieve a significant antibacterial effect is around 0.5–20A l g À1in foods and about 0.1–10A l ml À1in solutions for washing fruit and vegetables.EOs compri a large number of components and it is likely that their mode of action involves veral targets in the bacterial cell.The hydrophobicity of EOs enables them to partition in the lipids of the cell membrane and mitochondria,rendering them permeable and leading to leakage of cell contents.Physical conditions that improve the action of EOs are low pH,low temperature and low oxygen levels.Synergism has been obrved between carvacrol and its precursor p -cymene and between cinnamaldehyde and eugenol.Synergy between EO components and mild prervation methods has also been obrved.Some EO components are legally registered flavourings in the EU and the USA.Undesirable organoleptic effects can be limited by careful lection of EOs according to the type of food.D 2004Elvier B.V .All rights rerved.
Keywords:Esntial oils;Antibacterial;Prervatives;Food borne pathogens
1.Introduction
In spite of modern improvements in slaughter hygiene and food production techniques,food safety is an increasingly important public health issue (WHO,2002a).It has been estimated that as many as 30%of people in industrialid countries suffer
from a food borne dia each year and in 2000at least two million people died from diarrhoeal dia worldwide (WHO,2002a).There is therefore still a need for new methods of reducing or eliminating food borne pathogens,possibly in combination with exist-ing methods (the hurdle principle;Leistner,1978).At the same time,Western society appears to be experi-encing a trend of ‘green’consumerism (Tuley de Silva,1996;Smid and Gorris,1999),desiring fewer synthetic food additives and products with a smaller
0168-1605/$-e front matter D 2004Elvier B.V .All rights rerved.doi:10.1016/j.ijfoodmicro.2004.03.022
*Tel.:+31-30-2535350;fax:+31-30-2532365.E-mail address:s.a.burt@vet.uu.nl (S.Burt).
/locate/ijfoodmicro
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International Journal of Food Microbiology 94(2004)223–
253
impact on the environment.Furthermore,the World Health Organization has recently called for a world-wide reduction in the consumption of salt in order to reduce the incidence of cardio-vascular dia (WHO,2002b).If the level of salt in procesd foods is reduced,it is possible that other additives will be needed to maintain the safety of foods.There is therefore scope for new methods of making food safe which have a natural or‘green’image.One such possibility is the u of esntial oils as antibacterial additives.
Esntial oils(EOs)(also called volatile or ethereal oils;Guenther,1948)are aromatic oily liquids ob-tained from plant material(flowers,buds,eds, leaves,twigs,bark,herbs,wood,fruits and roots). They can be obtained by expression,fermentation, enfleurage or extraction but the method of steam distill
ation is most commonly ud for commercial production of EOs(Van de Braak and Leijten,1999). The term‘esntial oil’is thought to derive from the name coined in the16th century by the Swiss reform-er of medicine,Paracelsus von Hohenheim;he named the effective component of a drug Quinta esntia (Guenther,1948).An estimated3000EOs are known, of which about300are commercially important—destined chiefly for the flavours and fragrances market (Van de Braak and Leijten,1999).It has long been recognid that some EOs have antimicrobial proper-ties(Guenther,1948;Boyle,1955)and the have been reviewed in the past(Shelef,1983;Nychas, 1995)as have the antimicrobial properties of spices (Shelef,1983)but the relatively recent enhancement of interest in‘green’consumerism has lead to a renewal of scientific interest in the substances (Nychas,1995;Tuley de Silva,1996).Besides anti-bacterial properties(Deans and Ritchie,1987;Carson et al.,1995a;Mourey and Canillac,2002),EOs or their components have been shown to exhibit antiviral (Bishop,1995),antimycotic(Azzouz and Bullerman, 1982;Akgu¨l and Kivancß,1988;Jayashree and Sub-ramanyam,1999;Mari et al.,2003),antitoxigenic (Akgu¨l et al.,1991;Ultee and Smid,2001;Juglal et al.,2002),antiparasitic(Pandey et al.,2000;Pessoa et al.,2002),and incticidal(Konstantopoulou et al., 1992;Karpouhtsis et al.,1998)properties.The characteristics are possibly related to the function of the compounds in plants(Guenther,1948;Mah-moud and Croteau,2002).
The purpo of this paper is to provide an overview of the published data on the antibacterial activity of tho EOs and their components that could be con-sidered suitable for application in or on foods,and to describe their possible modes of action.The current knowledge on potential antagonists and synergists is prented;legal and safety aspects are discusd and areas for future rearch are propod.Although some data are prented on spoilage flora,this paper will focus chiefly on the antibacterial effect of EOs on food borne pathogens and,in particular,tho for which food animals are the major rervoir.
1.1.Historical u of esntial oilsit职业
Although spices have been ud for their perfume, flavour and prervative properties since antiquity (Bauer et al.,2001),of the known EOs,only oil of turpentine was mentioned by Greek and Roman historians(Guenther,1948).Distillation as a method of producing EOs was first ud in the East(Egypt, India and Persia)(Guenther,1948)more than2000 years ago and was improved in the9th century by the Arabs(Bauer et al.,2001).The first authentic written account of distillation of esntial oil is ascribed to Villanova(ca.1235–1311),a Catalan physician (Guenther,1948).By the13th century EOs were being made by pharmacies and their pharmacological effects were described in pharmacopoeias(Bauer et al.,2001)but their u does not appear to have been widespread in Europ
e until the16th century,from which time they were traded in the City of London (Crosthwaite,1998).Publishing parately in that century on the distillation and u of EOs,two Strassburg physicians,Brunschwig and Reiff,mention only a relatively small number of oils between them; turpentine,juniper wood,romary,spike(lavender), clove,mace,nutmeg,ani and cinnamon(Guenther, 1948).According to the French physician,Du Chesne (Quercetanus),in the17th century the preparation of EOs was well known and pharmacies generally stocked15–20different oils(Guenther,1948).The u of tea tree oil for medical purpos has been documented since the colonisation of Australia at the end of the18th century,although it is likely to have been ud by the native Australians before that (Carson and Riley,1993).The first experimental measurement of the bactericidal properties of the安全生产述职报告
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vapours of EO is said to have been carried out by De la Croix in1881(Boyle,1955).However,in the cour of the19th and20th centuries the u of EOs in medicine gradually became condary to their u for flavour and aroma(Guenther,1948).
1.2.Current u of EOs
川端康成简介
旋转楼梯设计图The greatest u of EOs in the European Union(EU) is in food(as flavourings),perfumes(fragrances and aftershaves)and pharmaceuticals(for their functional properties)(Bauer and Garbe,1985;Van Welie,1997; Van de Braak and Leijten,1999).The well-known u of EO in aromatherapy constitutes little more than2% of the total market(Van de Braak and Leijten,1999). Individual components of EOs are also ud as food flavourings,either extracted from plant material or synthetically manufactured(Oosterhaven et al.,1995).
The antibacterial properties of esntial oils and their components are exploited in such diver com-mercial products as dental root canal alers(Manabe et al.,1987),antiptics(Bauer and Garbe,1985;Cox et al.,2000)and feed supplements for lactating sows and weaned piglets(Van Krimpen and Binnendijk, 2001;Ilsley et al.,2002).A few prervatives con-taining EOs are already commercially available.‘DMC Ba Natural’is a food prervative produced by DOMCA S.A.,Alhendı´n,Granada,Spain and compris50%esntial oils from romary,sage and citrus and50%glycerol(Mendoza-Yepes et al., 1997).‘Protecta One’and‘Protecta Two’are blended herb extracts produced by Bavaria Corp.Apopka,FL, USA and are clasd as generally recognized as safe (GRAS)food additives in the US.Although the preci contents are not made known by the manu-facturer,the extracts probably contain one or more EOs and are disperd in solutions of sodiu
m citrate and sodium chloride,respectively(Cutter,2000). Further physiological effects of EOs are made u of in widely differing products such as commercial potato sprout suppressants(Hartmans et al.,1995) and inct repellents(Carson and Riley,1993).
2.Composition of EOs
Steam distillation is the most commonly ud method for producing EOs on a commercial basis.Extraction by means of liquid carbon dioxide under low temperature and high pressure produces a more natural organoleptic profile but is much more expen-sive(Moyler,1998).The difference in organoleptic profile indicates a difference in the composition of oils obtained by solvent extraction as oppod to distilla-tion and this may also influence antimicrobial prop-erties.This would appear to be confirmed by the fact that herb EOs extracted by hexane have been shown to exhibit greater antimicrobial activity than the corresponding steam distilled EOs(Packiyasothy and Kyle,2002).EOs are volatile and therefore need to be stored in airtight containers in the dark in order to prevent compositional changes.
Numerous publications have prented data on the composition of the various EOs.The major compo-nents of the economically interesting EOs are summar-id by Bauer et al.(2001).Detailed co
mpositional analysis is achieved by gas chromatography and mass spectrometry of the EO or its headspace(Salzer,1977; Scheffer and Baerheim Svendn,1981;Wilkins and Madn,1991;Daferera et al.,2000;Juliano et al., 2000;Jerkovic et al.,2001;Delaquis et al.,2002).EOs can compri more than sixty individual components (Senatore,1996;Russo et al.,1998).Major compo-nents can constitute up to85%of the EO,whereas other components are prent only as a trace(Senatore,1996; Bauer et al.,2001).The phenolic components are chiefly responsible for the antibacterial properties of EOs(Contino et al.,1999).The major components of a number of EOs with antibacterial properties are prented in Table1and the structural formulae of a number of antibacterial components are prented in Fig.1.The components have either been shown to have antibacterial activity or the data on their mode of action is discusd in this paper.There is some evi-dence that minor components have a critical part to play in antibacterial activity,possibly by producing a syn-ergistic effect between other components.This has been found to be the ca for sage(Marino et al., 2001),certain species of Thymus(Lattaoui and Tan-taoui-Elaraki,1994;Paster et al.,1995;Marino et al., 1999)and oregano(Paster et al.,1995).
The composition of EOs from a particular species of plant can differ between harvesting asons and between geographical sources(Arras and Grella,1992; Marotti et al.,1994;McGimpy et al.,1994;Con-tino et al.,1999;Marino et al.,1999;Juliano et al.,
S.Burt/International Journal of Food Microbiology94(2004)223–253225
公务员晋升2000;Faleiro et al.,2002).This can be explained,at least in part,by the formation of antibacterial substances from their precursors.p -Cymene (1-meth-yl-4-(1-methylethyl)-benzene)and g -terpinene (1-methyl-4-(1-methylethyl)-1,4-cyclohexadiene)are the precursors of carvacrol (2-methyl-5-(1-methylethyl)-phenol)and thymol (5-methyl-2-(1-methylethyl)phe-nol)in species of Origanum and Thymus (Contino et al.,1999;Jerkovic et al.,2001;Ultee et al.,2002).The sum of the amounts of the four compounds prent in Greek oregano plants has been found to be almost equal in specimens derived from different geographi-cal regions (Kokkini et al.,1997)and to remain stable in plants harvested during different asons (Jerkovic et al.,2001).The same is true of Thymus vulgaris from Italy (Marino et al.,1999).This indicates that the four compounds are biologically and functionally cloly associated and supports the theory that thymol is formed via p -cymene from g -terpinene in T.vulgaris
(Kokkini et al.,1997).Generally,EOs produced from herbs harvested during or immediately after flowering posss the strongest antimicrobial activity (McGimp-y et al.,1994;Marino et al.,1999).Enantiomers of EO components have been shown to exhibit antimi-crobial activity to different extents (Lis-Balchin et al.,1999).The composition of EOs from different parts of the same pl
ant can also differ widely.For example,EO obtained from the eds of coriander (Coriandrum sativum L.)has a quite different composition to EO of cilantro,which is obtained from the immature leaves of the same plant (Delaquis et al.,2002).
3.In vitro tests of antibacterial activity
Tests of antimicrobial activity can be classified as diffusion,dilution or bioautographic methods (Rios et al.,1988).The principles and practice of the test
Table 1
Major components of lected a EOs that exhibit antibacterial properties Common name of EO Latin name of plant source Major components Approximate %composition b References
Cilantro Coriandrum sativum Linalool 26%(Delaquis et al.,2002)(immature leaves)
E-2-decanal 20%Coriander Coriandrum sativum (eds)Linalool 70%(Delaquis et al.,2002)
E-2-decanal
–Cinnamon Cinnamomum zeylandicum Trans-cinnamaldehyde 65%
研究背景怎么写
(Lens-Lisbonne et al.,1987)
挂面怎么做
Oregano
Origanum vulgare
Carvacrol Trace-80%(Lawrence,1984;Prudent et al.,1995;
Thymol Trace-64%Charai et al.,1996;Sivropoulou et al.,1996;g -Terpinene 2–52%Kokkini et al.,1997;Russo et al.,1998;p-Cymene Trace-52%Daferera et al.,2000;Demetzos and Perdetzoglou,2001;Marino et al.,2001)
Romary Rosmarinus officinalis
a -pinene
2–25%(Daferera et al.,2000,2003;Pintore et al.,2002)
Bornyl acetate 0–17%Camphor 2–14%1,8-cineole 3–89%Sage Salvia officinalis L.Camphor 6–15%(Marino et al.,2001)
a -Pinene 4–5%h -pinene 2–10%1,8-cineole 6–14%a -tujone 20–42%Clove (bud)Syzygium aromaticum Eugenol
75–85%(Bauer et al.,2001)
Eugenyl acetate 8–15%Thyme
Thymus vulgaris
Thymol 10–64%(Lens-Lisbonne et al.,1987;Carvacrol 2–11%McGimpy et al.,1994;
g -Terpinene 2–31%Contino et al.,1999;Marino et al.,1999;p-Cymene
10–56%
Daferera et al.,2000;Juliano et al.,2000)
a
EOs which have been shown to exert antibacterial properties in vitro or in food models and for which the composition could be found in the literature.
b
Percentages of total volatiles rounded up to the nearest whole number.
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methods are explained in the literature (Barry,1976;Davidson and Parish,1989;Hodges and Hanlon,1991)but it appears that no standardid test has been developed for evaluating the antibacterial activity of possible prervatives against food-related microor-ganisms,although the need for such has been indicated (Davidson and Parish,1989).The NCCLS method for antibacterial susceptibility testing,which is principally aimed at the testing of antibiotics has been modified for testing EOs (Hammer et al.,1999;NCCLS,2000).Rearchers adapt experimental methods to better reprent possible future applications in their particular field.However,since the outcome of a test can be affected by factors such as the method ud to extract the EO from plant material,the volume of inoculum,growth pha,culture medium ud,pH of the media and incubation time and temperature (Rios et al.,1988),comparison of published data is complicated (Jansn et al.,1987;Friedman et al.,2002).A number of reviewers have surveyed the methods ud for antibacte
rial activity studies carried out with EOs (Koedam,1977a,b;Shelef,1983;Jansn et al.,1987;Rios et al.,1988;Nychas,1995).In papers published since,the number of variations on culture medium,size of inoculum,choice of emulsifier and basic test method has further incread.
The minimum inhibitory concentration (MIC)is cited by most rearchers as a measure of the anti-bacterial performance of EOs.The definition of the MIC differs between publications and this is another obstacle to comparison between studies.In some cas,the minimum bactericidal
concentration
Fig.1.Structural formulae of lected components of EOs.
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