new global challenges to the use of gaseous treatments in...

Fumigation and Control Atmosphere

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KPS6-1

New global challenges to the use of gaseous treatments in storedproducts

S. Navarro1

1 Department of Food Science, Agricultural Research Organization, the Volcani Center. P. O. Box 6, Bet Dagan 50250,

Israel. Fax: +972-3-5582069. e-mail: [email protected]

Abstract

Concerns over the adverse effects of fumigantresidues in food and the environment have ledregulatory agencies to take actions by imposingstrict limitations on fumigant registration. Of thelong list of fumigants two decades ago, very fewremain today. MB has a relatively quick killingeffect on insects, but because of its contributionto stratospheric ozone depletion has been phasedout in developed countries since 2005, and indeveloping countries phase out will take placeby 2015. In contrast, phosphine remains popular,even though insects have developed resistanceto it. These restrictions on the use of fumigantshave posed new global challenges to the foodindustry, and have resulted in efforts to registernew fumigants, and in the development of newtechnologies as alternative control methods.Among the newly considered fumigants aresulfuryl fluoride, carbonyl sulphide, propyleneoxide, methyl iodide, ozone, ethyl formate, andhydrogen cyanide. Sulfuryl fluoride seems toemerge as a promising candidate fumigant fordisinfesting stored food commodities, food-processing facilities and as a quarantine fumigant.Other registered fumigants suffer from thelimitation that they may be useful for treating aparticular type of commodity or for applicationin a specific situation only. The potential use ofvolatiles of botanical origin shows promise butrequires both commercial scale trials and

registration procedure before they can be employedin practice. Among the new gaseous applicationtechnologies that have successfully replacedfumigants are the manipulation of modifiedatmospheres (MAs) alone or at high temperatures,and high pressure carbon dioxide that needs to befurther explored for specific applications. A recentdevelopment is the use of MAs in a low-pressureenvironment. These niche applications of MAs thathave resulted in very promising application treatmentswith market acceptability, should serve as modelsfor global challenges for new application methods.

Key words: fumigation, methyl bromidealternatives, phosphine, gaseous treatments,modified atmospheres.

Introduction

Fumigants are widely used for pestelimination in all stored products that includecereals, oilseeds, pulses, spices, dried fruits, treenuts and their processed foods, to preventeconomic and quality losses due to insect pestattack. Fumigants may be used; a) as a hygienicmeasure during storage; b) to provide wholesomefood for the consumer; and c) as a mandatoryrequirement in trade and in quarantine(Rajendran, 2001).

Increased public concern over the adverseeffects of pesticide residues in food and the

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environment has led to the partial substitution byalternative control methods. Therefore, non-chemicaland environmentally user-friendly methods of pestcontrol in the post harvest sector are becomingincreasingly important. It is worth noting that of the16 fumigants listed in common use some 22 yearsago by Bond (1984), only very few remain today.Most of these fumigants have been withdrawn ordiscontinued on the grounds of environmental safety,cost, carcinogenicity and other factors. Methylbromide (MB) has been phased out in developedcountries since 2005 and will be phased out indeveloping countries by 2015, because of itscontribution to stratospheric ozone depletion(UNEP, 2002). Although there are exemptions forquarantine and pre-shipment purposes, as well asthe possibility to apply for exemptions where noalternative exists, the applicant has to demonstratethat every effort is being made to research alternativetreatments. In contrast; phosphine remains popular,particularly in developing countries, because it iseasier to apply than MB. However, many insectshave developed resistance to phosphine over thelast decade (Cao et al., 2003; Savvidou et al.,2003).

Food industries and particularly exporters aredependent on fumigation as a quick and effectivetool for insect pest control in food commodities.Following on the WTO and Free Trade Policies,trade traffic of foodstuffs across the world hasbeen considerably increased. Consequently,fumigation for disinfesting stored foodcommodities has been playing a significant role.Some developed countries have adopted theapproach of zero tolerance of insect pests in foodcommodities. On the other hand, the fumigationtechnology that is required to obtain this zeroinfestation has been facing threats/constraintsbecause of regulatory implementation and thedevelopment of resistance (Arthur and Rogers,.2003).

The aim of the present paper is to elucidatethe new global challenges to the use of gaseoustreatments in stored products. These challengesderive from the increased demand of competitivemarkets for quality in food commodities freefrom pest and pesticide contaminants on the one

hand, and the need to find and the cost involvedin adopting alternative control measures on theother. They have resulted in efforts to registernew fumigants in several countries, and in thedevelopment of new technologies as alternativecontrol methods.

The gaseous treatments

The gaseous treatments may be categorizedinto three groups; a) residue-leaving fumigantsthat are synthetically produced volatilechemicals; b) volatile essential oils of botanicalorigin; and c) non-residual modified atmospheres(MAs).

a) Fumigants and their current status:The chemical treatments discussed in this

presentation are categorized under structuraltreatments and commodity fumigations. Amongthe synthetic chemical treatments, the list todayis limited to MB, phosphine, sulfuryl fluoride,propylene oxide, carbonyl sulphide, ethylformate, hydrogen cyanide, carbon disulphide,methyl iodide, ozone, and carbon dioxide.

The current most commonly usedfumigants

Methyl bromide

One of the main features that make MB acommercially desirable fumigant is its speed ofaction. In addition, MB has a number ofadditional desirable features including itsrecognition by quarantine authorities, and itsbroad registration for use; it also has goodpenetration ability, and the commodity airsrapidly after exposure. When consideringalternatives, the above properties need to beviewed against a background of MB as a highlytoxic, odorless gas with substantial ozone-depleting potential and adverse effects on anumber of durables, particularly loss of viability,quality changes, taint and residues.


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MB plays an important role in pest control indurable and perishable commodities andparticularly in quarantine treatments. TheMontreal Protocol, an international treatydeveloped to protect the earth from thedetrimental effects of ozone depletion and signedby 175 countries, is now phasing out ozonedepleting compounds including MB on aworldwide basis. Accordingly, legislativechanges have been made in different countriesto control the use of MB, which has an averageozone depleting potential of 0.4. The ban on MBcurrently exempts quarantine and pre-shipment(QPS) treatments, emergency uses and certaincritical uses where no alternatives have yet beendeveloped (TEAP, 2000). However, theseexemptions will be reviewed periodically ininternational meetings and they might notcontinue forever. In the absence of suitablealternatives, this loss of MB as a fumigant couldseriously affect the protection of stored andexported food commodities from pest organisms.To combat this situation, one approach has beento accept the use of MB where no alternativesexist, but, after fumigation, to absorb the gas forrecycling or to destroy it instead of releasing itto the atmosphere. There has been some limitedimplementation of recovery and recycling forMB, mainly in North America and Europe.Recovery and recycling systems are generallycomplex and expensive to install compared withthe cost of the fumigation facility itself. Thesesystems would also require a level of technicalcompetence not normally found at fumigationfacilities. Therefore, examples of recovery andrecycle in current commercial use are few.

Phosphine

Phosphine is available in solid preparationsof aluminium or magnesium phosphide and incylinders containing carbon dioxide ECO2

FUME® or nitrogen FRISIN®. Lately, on-sitephosphine generators that can release thefumigant up to the rate of 5 kg h–1 are availablein some countries (Argentina, Chile, China andUSA). Metal phosphide formulations with slow

or altered rates of phosphine release have beendeveloped and tested in Australia (Waterford andAsher, 2000) and India (Rajendran, 2001).Improved application techniques such as the“Closed Loop System” in the USA, SIROFLO®

and SIROCIRC® in Australia and PHYTOEXPLO® in Europe have been developed forapplication in different storage situations. Insectresistance is a serious concern that threatens thecontinued effective use of phosphine. Phosphinefumigation protocols have been revised indifferent countries to tackle the problem of insectresistance to the fumigant. Two major restrictionsof phosphine are that it requires several days ofexposure to achieve the same level of control asthat of MB, and that it corrodes copper and itsalloys and therefore electrical and electronicitems need protection from exposure to thefumigant. Phosphine also reacts to certainmetallic salts, which are contained in sensitiveitems such as photographic film and someinorganic pigments.

Newly considered fumigants

Sulfuryl fluoride

Sulfuryl fluoride has been used as a structuralfumigant for dry wood termite control for thepast 45 years, but it also has potential applicationsin disinfesting flour mills and food factories (Bellet al., 1999). Although it can be used effectivelyfor insect pest control in dry tree nuts and foodgrain, data are scarce on the effect of sulfurylfluoride on quality of the treated commodity andpersistence of residues. The fumigant is morepenetrative into treated commodities than MB.Insect eggs are the most tolerant stage for sulfurylfluoride. The relative egg tolerance can beovercome by increasing the exposure period andby raising the treatment temperature (Bell et al.,1999). Sulfuryl fluoride has been registered andused as a structural fumigant in Germany,Sweden and the USA. Sulfuryl fluoride isavailable under the trade name “Vikane”containing 99.8 % sulfuryl fluoride and 0.2 % inert


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materials. Apart from the USA, China has beenproducing sulfuryl fluoride (trade name“Xunmiejin”) since 1983 (Guogan et al., 1999).Also, sulfuryl fluoride can be applied underreduced pressure so that the exposure period canbe drastically reduced (Zettler and Arthur, 2000).The fumigant was noted as highly toxic todiapausing larvae of the codling moth, Cydiapomonella in stored walnuts (Zettler et al.,1999). Sulfuryl fluoride is now registered underthe new trade name “ProFume®” for the protectionof stored food commodities (Schneider et al.,2003). ProFume® is registered in the US to allowvirtually all mills and food processing facilities totest, adapt and consider adoption as an alternativeto MB. Additionally, registration coverage in ECcountries for numerous milling and foodprocessing applications is broad, and increasing(TEAP, 2006).

Propylene oxide

Propylene oxide (PPO) is a colorless andflammable liquid, and is used as a foodemulsifier, surfactant, cosmetics and starchmodifier. Under normal temperature and pressurePPO has a relatively low boiling point (35 oC)and a noticeable ether odor (Weast et al., 1986).It is a safe fumigant for use on food; it isregistered and used in the USA as a sterilant forcommodities such as dry and shelled walnuts,spices, cocoa powder and nutmeats (Griffith,1999). A disadvantage of PPO is that it isflammable at from 3 to 37 % in air, and therefore,to avoid flammability it should be applied underlow pressure or in CO2 -enriched atmospheres.Griffith (1999), in preliminary tests on somestored product pests, indicated that PPO hasinsecticidal properties under vacuum conditionsas a fumigant. Navarro et al. (2004) studied therelative effectiveness of PPO alone, and incombination with low pressure or CO2.

Carbonyl sulphide

Carbonyl sulfide (COS) is naturally presentat low levels in food grains, vegetables (Brassica

spp.) and cheese. Research work on carbonylsulfide in Australia, Germany and the USA revealthat the egg stage is highly tolerant to thefumigant. Reports from Australia indicate thatthe fumigant does not affect the quality of wheat,and germination is not affected. However,investigations on carbonyl sulfide carried out inChina showed contradictory results. Xianchanget al. (1999) reported that carbonyl sulfide affectsgermination of cereals except sorghum andbarley, and imparts off-odour. Milled rice aftertreatment of paddy rice with carbonyl sulfide atthe above dosages had an undesirable odour.Change in colour was also observed in fumigatedsoybeans. Zettler et al. (1999) also noticed anoff-odour during the first 24 h of aeration inwalnuts that were fumigated with carbonylsulfide. It is suspected that hydrogen sulfidepresent in the supplied product, as an impurity,is partly responsible for the off-odour problem(Desmarchelier, 1998).

Ethyl formate

Ethyl formate is known as a solvent and isused as a flavoring agent in the food industry. Itis naturally present in certain fruits, wine andhoney. In India, extensive laboratory tests againstinsect pests of food commodities and field trialson bagged cereals, spices, pulses, dry fruits andoilcakes have been carried out on the fumigant(Muthu et al., 1984). Currently ethyl formate isbeing used for the protection of dried fruits inAustralia. It has been found suitable for in-package treatment of dried fruits. Studies inAustralia indicate that, unlike phosphine, ethylformate is rapidly toxic to storage insectsincluding psocids (Annis and Graver, 2000).

Hydrogen cyanide

Hydrogen cyanide (HCN) is currentlyregistered only in India, New Zealand and withsevere restrictions in Germany. HCN was one ofthe first fumigants to be used extensively under“modern” conditions. Its use for treating treesunder tents against scale insects was developed


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in California in 1886 (Woglum, 1949). The highdermal toxicity of the gas makes it hazardous toapplicators. HCN is one of the most toxic ofinsect fumigants; it is very soluble in water. HCNmay be employed for fumigating many dryfoodstuffs, grains, and seeds. Although HCN isstrongly sorbed by many materials, this action isusually reversible when they are dry, and, giventime, all the fumigant vapours are desorbed. Withmany foodstuffs, little, if any, chemical reactionoccurs, and there is no detectable permanentresidue. Because of the high degree of sorptionat atmospheric pressure, HCN does not penetratewell through the bulk of some commodities.

Carbon disulphide

Carbon disulfide (CS2), an old fumigant, isused at the farm level in some parts of Australiaand to a limited extent in China (TEAP, 2000).The major advantage of carbon disulfide is itssmall effect on seed germination. However,residues of carbon disulfide persist in treatedcommodities for a longer period than that of otherfumigants (Haritos et al., 1999). The reductionin baking quality of wheat treated with thisfumigant was shown by Calderon et al. (1970).Some of the limitations of the fumigant includehigh flammability, long exposure period,persistence in the treated commodity, lack ofresidue limits set by Codex Alimentarius and highhuman toxicity.

Methyl iodide

Methyl iodide has been patented as a pre-plantsoil fumigant for control of a broad range oforganisms including nematodes, fungi, andweeds (Grech et al., 1996) and the patent hassubsequently been expanded to include structuralfumigation against termites and wood rottingfungi (Ohr et al., 1998). Methyl iodide’s potentialas a fumigant for postharvest pest control hasbeen known for more than 68 years (Lindgren,1938). However, economic considerations at thattime precluded its development in favor of the

less-expensive MB.Methyl iodide was found to be very effective

as a space fumigant (Shaaya et al., 2003; Zettleret al., 1999), being most toxic to eggs and leasttoxic to adults of Tribolium confusum (Tebbetset al., 1986). Yokoyama et al. (1987) showedthat methyl iodide could prove valuable as aquarantine treatment for Carpocapsa pomonellain fresh fruits and as a rapid commoditydisinfestation treatment of 24h or less. The factthat the US Environmental Protection Agency haslisted methyl iodide as a possible humancarcinogen could preclude registration in the US,particularly in California where it is listed as acompound known to cause cancer (EPA, 1998).

Cyanogen

Cyanogen (C2N2) is a colorless gas withalmond like odor and was patented as a newfumigant effective against insects andmicroorganisms (Yong and Trang, 2003). It ishighly toxic to stored product insects and is fastacting. It has a good penetration through the grainmass and it desorbs quickly. It is phytotoxic andaffects germination of treated seeds. But, it haspotential for space and flour/rice mill fumigationsand disinfestations. Yong and Trang, (2003)compared the contrasting characteristics ofcyanogen, MB and phosphine as fumigants.

Ozone

Ozone, a known sterilant, can be used as aninsect control agent in food commodities at levelsless than 45 ppm. Ozone is readily generatedfrom atmospheric oxygen and is safe to theenvironment when used for fumigation.However it is highly unstable and breaks downto molecular oxygen quickly. A majordisadvantage with ozone is its corrosive propertytowards most of the metals (Mason et al., 1999).Active research is going on to exploit ozone as apotential quarantine treatment for controllingstored-product pests (Hollingsworth, andArmstrong, 2005).


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b) Volatile essential oils of botanical origin:The application of botanical extracts as

fumigants in the protection of stored productsfrom insect attack is in its infancy (Cox, 2002). Therehave been many plant extracts tested for theirfumigant toxicity effect on stored product insects.Pascual-Villalobos (2003) studied the insecticidaleffects of a group of plant essential oils (caraway,coriander, sweet basil, and garland chrysanthemum)against the damaging legume and cereal storagepests. Essential oils containing monoterpenoideswere noted to be toxic to some stored productinsects and comparable to MB (Isman, 2000; Shaayaet al., 2003; Tunc et al., 2000; Weaver andSubramanyam, 2000). The tested volatile plantextracts have the characteristics of essential oils witha typical aromatic scent from the plant from whichthey were extracted. Therefore, because of theiraromatic nature, plant extracts may be applied inempty premises or to commodities such as seedswhere the scent of the volatile essential oil wouldnot present a restriction after the treatment. Moststudies on volatile plant extracts have shown theirefficacy in empty fumigation chambers. Due to theirstrong absorption, their application in bulk storedcommodities is associated with poor penetrationability into the deep layers. Large scaleapplications that demonstrate the penetrationcapacity of these volatile oils are lacking in theliterature. A major delaying factor to the use ofthese oils is that such alternatives of plant originrequire toxicological and safety data forregistration for use as fumigants.

c) Non-residual gaseous treatments,modified atmospheres (MAs):

The objective of MA treatments is to attain acomposition of atmospheric gases rich in CO2 and lowin O2, or a combination of these two gases at normalor altered atmospheric pressure within the treatmentenclosure, for the exposure time necessary to controlthe storage pests and preserve the quality of thecommodity. Terms used in reference to MA storagefor the control of storage insect pests or for thepreservation of food have appeared in the literature asCA, as sealed storage, or atmospheres used at high

or low pressures to define the same method oftreatment but using different means.

New application technologies thathave successfully replaced fumigants

Cereal grain preservation

The initial research carried out during recentdecades was concentrated first on the possibleapplication of the MA technology to cereal grains(Adler et al., 2000; Banks and Annis, 1990;Navarro, 2006a).

Tree nuts and dried fruits preservation

The possibility of applying MAs to control insectsin dried fruits and tree nuts has been reviewed bySoderstrom and Brandl (1990). The influence of lowO2 or high CO2 atmospheres as alternatives tofumigation of dried fruits has also been investigated bySoderstrom, and Brandl (1984); and Tarr et al. (1994).Ferizli and Emekci (2000) applied CO2 for treatingdried figs in a gastight flexible storage unit loaded with2.5 tonnes of dried figs in perforated plastic boxes.These conditions resulted in complete mortality of bothinsects and mites. Full scale commercial application oforganic raisins is being applied in California since 1984(Navarro, 2000).

Disinfestation of dates

As a potential alternative to MB fumigation,the influence of different CAs in causingemigration of Carpophilus spp. larvae from dateswas compared with that of MB by Donahaye etal. (1991) and Navarro et al. (1989). Aconcentration of 35 % CO2 was found to cause asimilar emigration to that by MB. This methodhas been in use in a large packing house in Israel(Navarro, 2006b).

Application of MAs at elevatedtemperatures

The influence of temperature on the length of time


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necessary to obtain good control with MAs is asimportant as with conventional fumigants. Navarroand Calderon (1980) compared the effect oftemperature on the exposure time required toproduce the mortality of adults of three storageinsects in MAs. Donahaye et al. (1994) reportedon responses of larval, pupal, and adult stages oftwo nitidulid beetles exposed to simulated burner-gas concentrations at three temperatures of 26, 30,and 35 °C. Soderstrom et al. (1992) examined theinfluence of temperature over the range of 38–42°C on the effects of hypoxia and hypercarbia onTribolium castaneum adults. Their results clearlyindicate that raised temperatures could be used toreduce treatment duration. Navarro et al. (2003)showed the strong influence of temperatures of 35 o,40 o, and 45 oC on mortality of all four developmentstages of Ephestia cautella when the insects wereexposed to CO2 concentrations varying from 60to 90 % in air. Bell and Conyers (2002)investigated the potential to kill pests using MAsat raised temperatures to increase their speed ofaction. These works led to the application of MAsat elevated temperatures by ECO2 in Hollandwith the objective to reduce the exposure timescommercially to control pests in importedtobacco products, cocoa beans, rice, cereals,grains, nuts, peanuts, pulses, seeds and spices,as well as furniture and artifacts.

Vacuum treatment and V-HF technology

In a low-pressure environment, there is a closecorrelation between the partial pressure of theremaining O2 and the rate of kill. Until recently,this treatment could only be carried out inspecially constructed rigid and expensive vacuumchambers. A practical solution has been proposednamed the vacuum hermetic fumigation (V-HF)process that uses flexible liners (Finkelman etal., 2003). To achieve this, sufficiently lowpressures (25-50 mmHg absolute pressure) canbe obtained (using a commercial vacuum pump)and maintained for indefinite periods (Figure1).This technology is currently in use at commerciallevel for pest treatment of organic soybeans andflours in Israel.

Figure 1. A V-HF CocoonTM holding cocoa beansin bags, under a pressure of 50 mm Hg connectedto the vacuum pump in a trial site in Boston,Massachusetts (courtesy of GrainPro Inc.).

High pressure carbon dioxide treatment(HPCT)

Carbon dioxide still remains slower-actingand more expensive than phosphine or MB. CO2

treatments can be significantly shortened toexposure times that may be measured in hoursusing increased pressure (10-37 bar) applied inspecially designed metal chambers that withstandthe high pressures. Prozell et al. (1997) exposedcocoa beans, hazel nuts and tobacco to a quickdisinfestation process of exposure to carbondioxide under pressure of 20-40 bars. Becauseof the high initial capital investment, these high-pressure chamber treatments are practical forhigh value products such as spices, nuts,medicinal herbs and other special commodities.A number of countries have adopted the use ofthis technology; among them are Germany andTurkey.

Modified Atmosphere Packaging (MAP)

Modified Atmosphere Packaging (MAP) is atechnique used for prolonging the shelf-life periodof fresh or minimally processed foods. In thispreservation technique the air surrounding thefood in the package is modified to a composition


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of low oxygen or a combination of low oxygenand high carbon dioxide. The interest in modifiedatmosphere packaging (MAP) has grown dueconsumer demand. This has led to advances in thedesign and manufacturing of polymeric films suitablefor MAP. Under MA, products such as bakerygoods, and dried foods are packaged. The effectsof storage temperature and packaging atmosphere(air and N2) on the quality of almonds were studiedby Garcia-Pascual et al. (2003). Guidelines for usingmodified atmospheres in packaged food, with specialemphasis on microbiological and nutritional aspects,have been published by the Council of Europe(Anonymous, 1999).

Museum Artifacts

The possibilities of controlling pests inartifacts using inert gases were reported byReichmuth et al. (1991, 1993). Museumsthroughout the world face the challenge offinding non-toxic methods to control insect pests.Recently several publications focus on practicalrather than theoretical issues in the use of oxygen-free environments, presenting a detailed, hands-on guide to the use of oxygen-free environmentsin the eradication of museum insect pests(Maekawa and Elert, 2002; Selwitz andMaekawa, 1998).

As interest in modified atmospheres for foodpreservation peaked, conservation scientistsbegan to study how this technology could beadapted to museum needs (Selwitz andMaekawa, 1998). Although a carbon dioxideatmosphere had been favored for thepreservation of foodstuffs, conservators sawmore advantages in using nitrogen with lowoxygen concentrations to treat museumartifacts, collectively termed “cultural property”because anoxia provides a higher degree ofinertness and is easier to establish for small-scale operations. The technology of MA hasreceived the specific terminology of “anoxia”for the treatment of museum-artifacts, libraries,and among the manufacturers and suppliers of

material and equipment for the use of nitrogen.

Fresh storage of fruits and vegetables

Fresh fruits and vegetables may be shippedor stored in controlled atmospheres. This topicis covered in depth in the book of Calderon andBarkai-Golan (1990) and in a more recentlypublished chapter by Ben-Yehoshua, et al.(2005).

Narcissus bulbs treatments

The large narcissus fly Merodon eques F.attacks narcissus bulbs and also bulbs of othergeophytes. This species is a quarantine pestwhere complete mortality is required prior toexport from Israel. Fumigation with MB hasbeen used to eliminate narcissus fly infestationin flower bulbs due to its rapid killing time(4 h). However, MB is also known for itsphytotoxic effect on the bulbs and its use isdiscouraged even for quarantine purposes indeveloped countries.

In experimental procedures, Donahaye et al.(1997) found that there was an extremely rapiddepletion of O2 within the sealed gastightenclosures in which the narcissus bulbs wereplaced for fumigation, due to the respirationof the newly harvested bulbs. This procedurealso revealed the significant anoxia achievedwithin less than 20 hours (less than 0.1 % O2

and about 15 % CO2) during treatment at 28 °Cto 30 °C and the possibility of using it aloneas a control measure. The possibility ofobtaining a bio-generated modifiedatmosphere utilizing the bulb respiration alonewas adopted by Israeli farmers as a practicalsolution using specially designed flexibletreatment chambers (Figure 2) (Navarro andDonahaye, 2005; Navarro, 2006a). This MAmethod has been successfully applied by thenarcissus bulb growers in Israel and fullyreplaced the use of MB since 2003.


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Conclusions

No fumigant that has a broad spectrum of actionlike MB, and is inexpensive like phosphine, ispresently available. Although there is no doubt thatfumigation technology is extremely important for theprotection of stored products, many demands arerequired from potential alternative fumigants, fromthe sensitivity and lack of resistance of target peststo requirements for registration of new fumigants andre-registration to maintain the use of old fumigants.However, there is increasing public concern overthe adverse effects of pesticide residues in food andthe environment. Existing gaseous alternatives to MBand phosphine suffer from the limitation that theymay be useful for treating a particular type ofcommodity or for application in a specific situationonly. Sulfuryl fluoride seems to emerge as apromising candidate fumigant for disinfesting storedfood commodities, food-processing facilities and asa quarantine fumigant. Other fumigants are suitableto specific uses, such as propylene oxide for dryand shelled walnuts, spices, cocoa powder andnutmeats, ethyl formate can be suitable for driedfruits, carbon disulfide for seed materials, andcarbonyl sulfide for grains. Plant extract essentialoils and other volatiles of plant origin will need largescale demonstration of their penetration capacity, inaddition to toxicological and safety data for

registration for use as fumigants. The only gaseoustreatment that retains the special capacity offumigation for in-situ treatment of storedcommodities, as well as offering a similar diversityof application technologies, is the MA method. MAsoffer an alternative that is sustainable, safe, andenvironmentally benign to the use of conventionalresidue-producing chemical fumigants. Theapplication of MA in several fields of applicationhas already received recognition and successfullyreplaced MB and phosphine. The major fieldsof application of MAs are: grain and pulses storedin bulk, protection of organic products, use ofanoxia for museum artifacts, and libraries, anduse of MAP for the food packaging industry.Newly developed MA methods for nicheapplications, have resulted in very promisingapplications such as for the treatment of seeds,narcissus bulbs, cocoa beans, dried fruits andnuts. The global challenges in stored productsare the development of new and safer gaseoustreatments, and new application methods of MAsthat are commercially feasible.

Acknowledgements

The author thanks his colleagues Dr. E.Donahaye, Dr. S. Finkelman, and Dr. S. Angelformer researchers at the Volcani Center, the Israel

Figure 2. Narcissus bulbs in standard boxes before loading on pallets (upper left), loading thepallets containing the narcissus bulbs (left), and the general view of two sealed V-HF CocoonsTM

under treatment (right) (courtesy of GrainPro Inc.).

Agricultural Research Organization, and currently,FTIC (Food Technology International Consultancy)Ltd. for reading the manuscript and making valuablecomments.

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