20Dried Fruits and Tree Nuts

Judy A. Johnson, Elhadi M. Yahia, and David G. Brandl

CONTENTS20.1 Introduction 50720.2 Applications for Insect Control. 508

20.2.1 Dried Fruits 51120.2.2 Tree Nuts 51520.2.3 Combinations with Other Treatments 517

20.3 E(fects on Quality 51920.3.1 Almonds (Prunus dulcis) 51920.3.2 Apricots (Prunus armeniaca) 51920.3.3 Chestnuts (Castanea sativa) 52020.3.4 Dates (Phoenix dactylifera) 52020.3.5 Figs (Ficus carica) 52020.3.6 Hazelnuts, Filberts (Corylus spp.) 52120.3.7 Macadamia (Macadamia integrifolia) 52120.3.8 Peéan (Carya illinoinsis) 52120.3.9 Pine Nuts (Araucaria spp.) 52120.3.10 Pistachio (Pistacia vera) 52120.3.11 Raisins (Vitus vinifera) 52220.3.12 Walnuts (Juglans regia) 522

20.4 Conclusions 52220.5 Future Research Needs 523References 523

20.1 Introduction

'Dried fruits and tree nuts are relatively high-value products used primarily for snack foodsor as confectionary ingredients, and their successful marketing requires strict attention toquality control. The United States alone produces nearly 1.5million metric tons each yearof almonds, hazelnuts, macadamias, pecans, pistachios, walnuts, dates, figs, prunes,raisins, and dried apricots, worth more than $3 billion (USDA, 2007). These are alsovaluable products for the foreign export market, important to the economies of suchmajor producers as the United States and Turkey.Dried fruit and tree nuts typically have one or more preharvest insect pests that feed

directIy on the product and are capable of causing considerable damage and quality loss(Simmons and Nelson, 1975). Although many of these may be present at the time of

507

508 Modified and Controlled Atmospheres

--Dried Fruits and Tree j

harvest and are often brought into storage, they generally do not reproduce under storageconditions (Johnson et al., 2002). However, because they may continue to feed and causeadditional damage, and often present phytosanitary problems for processors, they areconsidered postharvest pests. Feeding damage by these insects also may provide entry toaflatoxin-producing molds (Aspergillus spp.) (Campbell et al., 2003).lnitial disinfestation ofan incoming product is sufficient to control these pests and reduce their damage. Thesecommodities are also susceptible to attack by a number of common stored product mothsand beetIes, the most serious being the Indianmeal moth, Plodia interpunctella (Simmonsand Nelson, 1975).Because stored product pests are capable of repeated infestation duringstorage, long-term protective treatments or repeated disinfestation treatments are neces-sary for their control.

Current insect control measures for dried fruit and nuts depend largely on fumigation todisinfect large volumes of incoming product during harvest, as well as to control storageinfestation (Johnson, 2004). Methyl bromide, a fumigant used in a wide range of post-harvest applications, is scheduled for worldwide withdrawal from routine use as afumigant in 2015 under the Montreal Protocol on ozone-depleting substances (UNEP,2006), and its use has already been severely restricted in developed countries. Resistanceto phosphine, often used as an altemative to methyl bromide for dried fruit and nut cropsin developed countries, has been documented in many insect populations (Benhalimaet al., 2004), and some regulatory agencies have expressed concems over worker safetywith this compound (Bell, 2000). Sulfuryl fluoride, long used for structural fumigation,has recentIy been registered for commodity fumigation in several countries including theUnited States (Prabhakaran and Williams, 2007), but reduced toxicity of this compoundagainst insect eggs and at lower temperatures (Bell and Savvidou, 1999) may limit itsapplicability. Moreover, there is a mounting pressure against the general use of chemicalfumigants due to atmospheric emissions, safety, or health concems, and an increasedinterest in organic food production, resulting in efforts to develop nonchemical technologiesas altemative control methods for insects. Among these technologies are low and hightemperatures, irradiation, and modified atmosphere (MA)and controlled atmosphere (CA).

Dried fruits and nuts, like most low-moisture, durable commodities, often tolerateextreme MA and CA (very high CO2 andjor very low O2) at levels used to control insects.More than 25 years ago, the U.S. Environmental Protection Agency approved carbondioxide, nitrogen, and combustion product gases as a means to manage insects infestingraw and processed agricultural products, including dried fruits and tree nuts (Johnson,1980, 1981). While current insect control measures for dried fruits and nuts still rely onfumigation, there is some limited commercial use of MA and CA for these products,primarily for organic product lines. This chapter will discuss the potential applicationsand effect on product quality of MA and CA treatments for insect control in dried fruitsand tree nuts.

20.2 Applications for Insect ControlA variety of insects, infesting the product either in the field or during storage, may befound in postharvest dried fruits and nuts (Table 20.1).Although infestations cause directdamage through feeding and by contaminating product with excreta, webbing, andexuvia, these loses are relatively low. Increased losses occur when infestations cause theimplementation of regulatory actions or, worse yet, loss of consumer confidence.The presence of any live insects may impact trade, particularly to foreign markets. Somestates and countries consider certain field pests, such as codling moth, filbertworm, and

TABLE 20.1

Postharvest Insect Pests

CommonName

Field pests (do not normal!Carob mothCodling mothDried fruit beetles

FilbertwormNavel orangewormRaisin mothTropical nut borerVarious nut weevils

Postharvest Storage Pests~AlmondmothIndianmeal moth

Grain and flour beetles

Various beetles

Vinegar flies

Curculio Spp., to be qlof product to preventproducts are cosmoposubject to quarantineinspectors.

Correctly appliedprates for fieldpests,buprevent further damalreproduce in storage,stored product insectlconditions. Driedfruilstorage formonthsorI

by storage pests.Stratments are effectiveinerely on one or moredi

Disinfestation treatprocessing and storalresidues on marketedmental and workersalfruit and nut producthandled, no singledFumigants are cornrnwide range of applicaany altemative treatmtoo costIy. For some i

controlled atrnosphenThe volumes ofdrie

of time to meet thedel

Curculio spp., to be quarantine pests, and as such require specific disinfestation treatmentsof product to prevent pest introductions. While most of the storage insects found in theseproducts are cosmopolitan in distribution (Simmons and Nelson, 1975),and are not usuallysubject to quarantine restrictions, they can cause the rejection of product when found byinspectors.

Correctly applied preharvest pest management practices result in very low infestationrates for field pests, but disinfestation treatments shortly after harvest are often necessary toprevent further damage and meet phytosanitary standards. Because most field pests rarelyreproduce in storage, a single treatment is sufficient. In contrast, populations of commonstored product insects such as the Indianmeal moth may increase rapidly under storageconditions. Dried fruits and tree nuts are considered durable products, and may be held instorage for months or even years, during which the product is always at risk of reinfestationby storage pests. Strategies emphasizing exclusion, sanitation, and use of protective treat-ments are effective in controlling storage pests, but dried fruit and nut processors commonlyrely on one or more disinfestation treatments to ensure insect-free products.

Disinfestation treatments must be efficacious, economical, applicable to the existingprocessing and storage system, and must not harm product quality or leave chemicalresidues on marketed producto AIso, for treatments to be completely accepted, environ-mental and worker safety concerns should be manageable. Because of the diversity of driedfruit and nut products, their production, storage, and marketing methods, and volumeshandled, no single disinfestation method is suitable for all situations (Johnson, 2004).Fumigants are commonly used because of their efficacy, economy, and suitability to awide range of applications (Hagstrum and Subramanyam, 2006). To be widely adopted,any altemative treatment must be as effective and practical as fumigants, and must not betoo costly. For some applications within the dried fruit and nut industry, modified andcontrolled atmospheres may be useful.

The volumes of dried fruits and nuts that must be treated within relatively short periodsof time to meet the demands of various markets are sometimes quite large when compared

TABLE 20.1

Postharvest Insect Pests of Dried Fruits and Nuts

Pest Status

509

Pest of dried fruits and nutsQuarantine pest in walnutsField pests in dates, figs, and on dryingfruits, norrnally reproduces in storageonly under high moisture conditions

Pest of hazelnutsPest in California tree nuts and figsFound on drying fruits, occasionally nutsPest of macadamiasPests of pecans, chestnuts, hazelnuts,and acoms

Common in nut productsMost serious storage pest, cornmonon all dried fruits and nuts

Cornmon in stored dried fruitsand nuts

Occasionally pests of dried fruitsand nuts

Cornmon in dried fruits

Scientific Name

Cydia latiferreanaAmyelois transitellaEphestia figulilellaHypothenemus obscurusCurcu/io spp.

Oryzaephilus spp. and Tribo/iumspp.Cryptolestes spp., Cryptophagusspp., and Trogoderma spp.Drosophila spp.

Various beetles

Vinegar flies

Grain and flour beetles

FilbertwormNavel orangewormRaisin mothTropical nut borerVarious nut weevils

Dried Fruits and Tree Nuts

CommonName

Field pests (do not normally reproduce in storage)Carob moth Ectomyelois ceratoniaeCodling moth Cydia pomonellaDried fruit beetles Carpophilus spp.

Postharvest Storage Pests (primarily found in storage)Almond moth Cadra cautellaIndianmeal moth Plodia interpunctella

510 Modified and Controlled Atmospheres Dried Fruits and TTl

to fresh horticultural commodities. MA and CA treatments are successful in replacingchemical fumigants only when they can be applied in a practical, timely, and economicalmanner to these large volumes. ConsequentIy, research has concentrated on the applica-tion of MA or CA to existing processing methods and storage systems (Figures 20.1 and20.2), in order to avoid drastic changes to facilities and to keep costs low. The methodsused to generate treatment atmospheres include gas from cylinders (Figure 20.3), exother-mically generated low oxygen atmospheres (GLOA) using combustion to reduce oxygenlevels (Storey, 1975),and gas separation systems (Johnson et al., 1998, 2002; Figure 20.4).Another form of modified atmosphere treatment is the use of low pressures to obtainreduced oxygen tensions (Navarro et al., 2003; Figure 20.5).

FIGURE 20.1some examples of dried fruit and nut storage found in the central valley of California. Clockwise from top:walnut silos, Fibreen covered raisin stacks; and plastic covered almond piles.

FIGURE 20.2Cornmon method of sun drying raisins on paper trays.

FIGURE 20.3Almond silosbeingtre¡

FIGURE 20.4Hollow fibermembram

20.2.1 Dried Frui

Sun-dried fruits SI

a variety ofinsectsand vinegar fliesnitidulid beetlesal

of excessivemoistlmoth, almond IDO

(Tribolium castaneualso be found (Sin

Sun-dried fruits such as raisins or figs are susceptible to attack as the product dries bya variety of insects such as raisin moth (Cadra figulilella), nitidulid beetles (Carpophilus spp.),and vinegar flies (Drosophila spp.) (Simmons and Nelson, 1975). Some, in particular,nitidulid beetles and vinegar flies, may continue to reproduce in storage under conditionsof excessivemoisture. The most common pests infesting product in storage are Indianmealmoth, almond moth (Cadra cautella), grain beetles (Oryzaephilus spp.), and red flour beetle(Tribolium castaneum), a1though a variety of additional common stored product insects mayalso be found (Simmons and Nelson, 1975).

Dried Fruits and Tree Nuts

FIGURE 20.3Almond silos being treated with CO2.

FIGURE 20.4Hollow fiber membrane gas separation system.

20.2.1 Dried Fruits

511

512 Modified and Controlled Atmospheres Dried Fruits and Ir,

TABLE 20.2Efficacyof GLOATreatments in Two Different Sizesof Fibreen-Covered Raisin StacksParameters 3308 m3 Stack 1869m3 Stack

Soderstrom and Brandl (1984a) treated raisins using GLOA, with a combustion atmos-phere of 0.5 kPa O2, 12-14 kPa CO2, 1.0 kPa argon, and the balance nitrogen. Stacks ofraisin bins were treated under either polyethylene sheeting or Fibreen, a weatherproofpaper laminated with tar and reinforced with fiberglass. The latter is commonly used forcommercial raisin storage, and was secured to a wooden framework built aroundstacked raisin bins and sealed to the ground with oiled dirt. Using a continuous purgerate of 12.7 m3/h, oxygen levels in small raisin stacks (34 m3

) covered with polyethylenedropped to 0.5 kPa in about 15 h. When adult Oryzaephilus mercator, adult red flour beetleand Indianmeal moth pupae were treated in these stacks, complete mortality was reachedat 48,72, and 96 h after purging began, respectively. Larger-scale tests used two Fibreen-covered raisin stacks, 1869 and 3308 m3

, treated at an initial purge rate of 283 m3/h toreduce oxygen to the target level of <0.5 kPa (Table 20.2). Of the insects treated, Drosophila

melanogaster pupaeand more than 2 Wi

raisins may be stOItimes are not unatreatment requires

An economicanibromide, phosphinthe GLOA system'and further costsalplant heating systerefined analysis (5<slightly lower thanwas the least cosbrornide has increéProtocol. MethylbJ400% from 1995towith the furnigant.

While early GL<about safety, risingof relatively inexpEthe demand for orlaltemative, and beyard stacks.

Researchers in tlatmospheres to trEhermetic storage,aplastic containersdor GrainPro Cocoo:system to apply e60-85 kPa CO2 anda 151 m3 chambetemperatures of 285 kPa CO2 was 01pressure, and was 1

60 kPa CO2 for 4.5effectively controllEbetween the treatel

Related laborato:low pressures «1;rate comparable tetreatments, whichdisinfestation, witlexposure. Howeveneeded to cause ea

Another study udates (Hussain, 19í10-20 kPa, insectn

The effect of GLet al. (1998).An ex(shipping containerwere infested witl

120h72h>336h120 h

283 m3/h24h14-17 m3/hWC

Saurce: From soderstrom, E.L. and Brand!, D.G., J. Ecan. Entamal., 77,440, 1984a.

Initial purge rate 283 m3/hTime to 0.5 kPa O2 48 hMaintenance purge rate 17 m3/hAverage temperature 27°CExposure needed for 100%mortality (time is from the beginning of initial purge)Cadra figuli/ella pupae 72 hPladia interpunctella pupae 48 hDrasaphila melanagaster pupae 120hCarpaphilus hemipterus rnixed cultures 60 hOryzaephilus surinamensis adults 48 hO. surinamensis larvae 48 hTriba/ium castaneum adults 48 hT. castaneum larvae 60 h

FIGURE 20.5Flexible,plastic treatment container under vacuum.

melanogaster pupae proved to be the most tolerant, requiring 5 days (120h) at around 27°C,and more than 2 weeks at around 16°C.Although these treatment times may seem lengthy,raisins may be stored in Fibreen-covered stacks for several months, and such treatmentstimes are not unacceptable. Phosphine is the fumigant of choice for such stacks andtreatment requires a minimum of 3 days at 27°C (Soderstrom et al., 1984).

An economic analysis was made of CA treatment of raisins, comparing costs for methylbromide, phosphine, GLOA, and nitrogen (Gardner et al., 1982).At the time of the analysis,the GLOA system was found to be competitive with both methyl bromide and phosphine,and further cost savings were seen when heat from the generators was recovered for use inplant heating systems. Use of liquefied nitrogen was found to be the most costly. A morerefined analysis (Soderstrom et al., 1984)found the cost of GLOA ($9.66-$10.64jMT) to beslightly lower than phosphine ($1O.76jMT).At the time of this analysis, methyl bromidewas the least costIy ($8.39jMT). Since these studies were done, the cost of methylbromide has increased considerably, largely due to restrictions imposed by the MontrealProtocol. Methyl bromide prices in the west coast of the United States increased by about400%from 1995 to 2001 (UNEPjTEAP, 2001), and may have made CA more competitivewith the fumigant.

While early GLOA systems were shown to be efficacious and cost effective, concernsabout safety, rising natural gas prices, environmental issues, and the continued availabilityof relatively inexpensive fumigants prevented adoption of the method by processors. Asthe demand for organic raisins increased, some processors revisited CA treatments as analtemative, and began using liquid nitrogen to disinfest raisins stored in Fibreen-coveredyard stacks.

Researchers in the Middle East have used a variety of methods to generate modifiedatmospheres to treat durable commodities such as dried fruits, including liquid CO2,hermetic storage, and vacuum treatments. Treatments were often applied within flexible,plastic containers developed for low cost, portable grain storage, known as Volcani Cubesor GrainPro Cocoons (Donahaye et al., 1991).Navarro et al., (1998a)used such a containersystem to apply CA treatments to disinfest dates of nitidulid beetles. An atmosphere of60-85 kPa CO2and 4-7 kPa O2generated from cylinderized liquid CO2was applied withina 151 m3 chamber partially filled with 30 t of dates stacked in crates on pallets attemperatures of 22°C-28°C. During the initial purge, a CO2 concentration of about85 kPa CO2 was obtained in the chamber within 1 h by introducing the gas under highpressure, and was maintained for 10 days. After that, CO2levels were maintained at about60 kPa CO2for 4.5 months using approximately 0.8 kg C02jday. Insect populations wereeffectivelycontrolled using this regimen, and no significant difference in quality was foundbetween the treated dates and controls stored at -18°C.

Related laboratory studies showed that C02levels >20 kPa, low 02levels «7 kPa) andlow pressures «170 mmHg) caused Carpophilus hemipterus to leave artificial refuges at arate comparable to methyl bromide treatments (Navarro et al., 1989). The low pressuretreatments, which provided O2 levels of <4.7 kPa, were the most effective means ofdisinfestation, with more than 80% of the beetles leaving refuges after just 10 min ofexposure. However, exposure periods for these treatments in excess of 24 h would beneeded to cause complete mortality (Navarro et al., 1998b)

Another study used storage under low pressure to control insect infestation in storeddates (Hussain, 1974).When infested dates are packed in polyethylene bags at pressures of10-20 kPa, insect mortality was 100%after 2 days.

The effect of GLOA on Cadra cautella infestation in dried figs was studied by Damarliet al. (1998).An exothermic generator that maintained 1 kPa O2and 10-15 kPa CO2in a 6 mshipping container was used at 25°C-35°Cfor 24-72 h. Dried fig samples of 3-4 kg to 8.5 twere infested with C. cautella larvae (16-22 days old) and eggs (24, 48, and 72 h old).

Dried Fruits and Tree Nuts 513

514 Modified and Controlled Atmospheres Dried Fruits and Il

There was 100% mortality of all stages in small-scale experiments at 35°C after 24 hexposure. Complete mortality of all stages infesting 8.5 t of dried figs was obtained at35°C after 30 h exposure. This exposure was comparable to the 24 h methyl bromidetreatment recommended to disinfest figs of C. cautella.

Laboratory studies (Meyvaci et al., 2003a) investigating methyl bromide altemativesshowed that 5 days of exposure to high C02levels (90-96 kPa) caused complete mortalityof C. cautella eggs, larvae, pupae, and adults at 25°C-35°C. Mixed-stage cultures of the figmite (Carpoglyphus lactis) required 6 days at these temperatures. Results for low-pressure(4.3 kPa) treatments were less consistent, but found that 3 day exposures at 25°C and2 day exposures at 30°C and 35°C was sufficient to control C. cautella, but 3 day exposuresat 30°C and 35°C were needed to control fig mites. In a related field study, Emekci et al.(2003) applied cylinderized CO2 to a 36 m3 flexible plastic storage container loaded withabout 15 MT of dried figs. CO2 and O2 levels were >95 kPa and <1 kPa, respectively, andremained stable throughout the 5 day treatment. Test insects included C. cautella eggs,P. interpunctella larvae, O. surinamensis pupae and adults, and mixed stages of C. hemipterusand C. lactis. The treatment was done at an average temperature of 28°C, and was sufficientto kill all test insects.

Mills et al. (2003) considered CO2 ('2:40 kPa) as an altemative to methyl bromidefumigation for disinfesting dried dates of carob moth (Ectomyelois ceratoniae). Use of CO2

under vacuum did not improve insect control and was not considered to be practical.CO2 treatment of dates in heated freight containers was more successful, providingadequate insect control after 4 days of exposure. The application of CO2 to dates underplastic cover was also considered successful and recommended when container capacity isinadequate.

Increasing CO2 concentrations (60-98 kPa) or decreasing O2 concentrations (0.5-5 kPa)caused progressively greater mortality of red flour beetle larvae (Soderstrom et al., 1992).Mortality was also increased by increasing temperature (38°C-42°C). However, pretreat-ment conditioning at 38°C for 24 or 48 h significantly reduced mortalities for the highestCO2 and lowest O2 treatments. These results suggest that temperatures above 38°C couldbe useful in reducing treatment times for CA, but wam that prior exposure to elevatedtemperatures should be avoided. Donahaye et al. (1994) also showed the effect of increas-ing temperature on efficacy of low O2 treatments for nitidulid beetles (Carpophilus hemi-pterus and Urophorus humeralis). For both species LT9ss for 1 kPa and 2 kPa O2 at 35°C wereusually less than half those at 26°C.

Tarr and Clingeleffer (2005) treated eggs, pupae, and adults of the red flour beetle inhermetically heat-sealed gas barrier bags containing 500 g of golden-colored, sultanaraisins, with or without the addition of a commercial O2 absorber. The bags were held at30°C for 9 days, 22SC for 20 days, or 15°C for 45 days. These times exceeded the minimumtime recommended by Annis (1987) for population extinction of red flour beetle under lowO2 conditions. O2 levels in the bags with or without the O2 absorber were ~1.7 kPa, and2.9-16.3 kPa, respectively. All fruit samples treated with O2 absorbers produced 100%mortality, with no occurrence of a second-generation population, when incubated post-treatment at 27°C for 60 days. Fruit stored in hermetically sealed bags without O2 absorbersat 22SC and 30°C produced 100% adult mortality but eggs and pupae survived. Results at15°C were confounded by complete control mortality of eggs and pupae, suggesting thatthe low temperature alone had a great effect. The low O2 atmosphere was also found tominimize raisin color change during storage.

The psocid Liposcelis bostrychophila is a common insect pest, which infests a varietyof processed and unprocessed stored foods in households, granaries, and warehouses.Psocids are highIy resistant to most forms of pest control, and their populations in storedfoods have increased alarmingly in some regions of Asia. Ding et al. (2002) examined the

effects of repeatec4-14 h) and the Íl

0.3 mgjmL for 24phila. Psocid pOplperiod with CA,untreated populalDDVP alone conbtreatments resulte¡alone. After sixex]increased 1.8- andincreased resistancwith insecticideappsocids in stored f

20.2.2 Tree Nuts

As with dried fruicrops such as alrncrelatívely Iow temFand may be a ph~nearly all tree nutsIndianmeal moth, :

In California, thmajor tree nut era]navel orangeworrrdamage by movinlStorey and Sodelnavel orangeworn9-9.5 kPa CO2, witmost tolerant to lo'and 38 and 37 h aorangeworm wereadults were expo!mortality.

Brandl et al. (1'orangeworrn mor!treatment times ti:action of O2 conceto control navel (their response; Inwhile navel orangthat navel orange1content, is less tolEstorage environrnE

The effect of lo\'Sodertrom and Britreated for 20 h \\contained in the nCO2 (40 kPa) signimore susceptible,the storage at the 1

effects of repeated exposures to low O2 CA (1 kPa O2, 35 kPa CO2, and 64 kPa N2 for4-14 h) and the insecticide dichlorvos (dimethyl dichloro-vinyl phosphate, DDVP 80%,0.3 mgjmL for 24 h) on population growth and development of resistance of L. bostrycho-phila. Psocid populations were treated and evaluated every 2 weeks over an 11 weekperiod with CA, with DDVP, or with altemating treatments of CA and DDVP. Anuntreated population increased 48.1-fold over the 11 week periodo Neither CA norDDVP alone controlled psocid population growth. However, altemating CA and DDVPtreatments resulted in a significant increase in mortality compared with either treatmentalone. After six exposures, resistance in populations exposed to either CA or DDVP aloneincreased 1.8- and 2-fold, respectively, and probit analysis of data suggested that furtherincreased resistance was possible. Results of this study have indicated that altemating CAwith insecticide applications could be a more effective management measure for control ofpsocids in stored foods than use of these treatments alone.

20.2.2 Tree Nuts

As with dried fruits, tree nuts may be infested with field pests during harvest. For nutcrops such as almonds, that are most often sun dried, or walnuts, which are dehydrated atrelatively low temperatures, these field pests are capable of continued damage in storage,and may be a phytosanitary concern in exported product (Johnson, 2004). In addition,nearly all tree nuts are susceptible to infestation by common stored product insects such asIndianmeal moth, grain beetIes, and red flour beetles.

In California, the navel orangeworm, Amyelois transitella, is a serious pest of the threemajor tree nut crops: almonds, pistachios, and walnuts. Although primarily a field pest,navel orangeworm may be brought into storage where younger larvae may continue todamage by moving to uninfested nuts (Curtis et al., 1984; Soderstrom and Brandl, 1984b).Storey and Soderstrom (1977) began investigations on the use of CA to controlnavel orangeworm using an exothermically generated low O2 atmosphere «1 kPa O2,

9-9.5 kPa CO2, with the balance mostIy N2). Pupae and mature larvae were found to be themost tolerant to low oxygen treatments, with LT9Ss of 145 and 138 h at 18°C, respectively,and 38 and 37 h at 27°C, respectively. Sublethal exposures of low oxygen to adult navelorangeworm were found to reduce their progeny number; no progeny were produced afteradults were exposed for 8 h, while 24 h exposures were required for complete adultmortality.

Brandl et al. (1983) examined the effect of various levels of O2 and CO2 on navelorangeworm mortality and determined that low O2 was more important in reducingtreatment times than CO2• Further study (Soderstrom et al., 1986) looked at the inter-action of O2 concentration, temperature, and relative humidity (RH) on the time neededto control navel orangeworm and Indianmeal moth. The two test species differed intheir response; Indianmeal moth was more affected by changes in O2 concentrationswhile navel orangeworm responded more strongly to changes in RH. It was suggestedthat navel orangeworm, as a pest that feeds mainly on product with a higher moisturecontent, is less tolerant to changes in relative humidities. Indianmeal moth, found in drierstorage environments, is better able to survive low relative humidities.

The effect oí low O2 or elevated CO2 atmospheres on insect feeding was examined bySodertrom and Brandl (1982). Feeding of navel orangeworm and Indianmeal moth larvaetreated for 20 h with various levels of O2 and CO2 was determined through a red dyecontained in the rearing medium. Both the lowest level oí O2 (1 kPa) and highest level ofCO2 (40 kPa) significantly reduced larval feeding of both species. Navel orangeworm wasmore susceptible, particularly to high CO2. Therefore, these results indicate that purgingthe storage at the beginning of nut filling operation would be beneficial in reducing insect

Dried Fruits and Tree Nuts 515

516 Modified and Controlled Atmospheres

--Dried Fruits and II

damage to the nuts. CO2 treatments were considered more practical beca use it was thoughtthat 40 kPa CO2 would be easier and cheaper to obtain in a rapid purge of treatmentcontainers.

Soderstrom and Brandl (1984b) conducted a series of successful tests using GLOA totreat bulk stored almonds under plastic covers, in a 3000 fe steel silo, and in 30 m by 7.3 mdiameter concrete silos containing 450 MT of inshell almonds. The initial purging of theconcrete silo took 8 h, and 100% mortality of Indianmeal moth and navel orangewormpupae was reached at 36 and 60 h after purging, respectively.

Codling moth (Cydia pomonella L.), is a common field pest of California walnuts.Although it does not reproduce in storage, it is considered a quarantine pest by somecountries, and processors have relied on methyl bromide to disinfest incoming product(Johnson, 2004). Diapausing codling moth larva e may be present in harvested walnuts, andwere found to be the most tolerant life stage to both low O2 and high CO2 atmospheresat 25°C, with the lowest LT95 (13.6 d) obtained at 60 kPa CO2 and 60% relative humidity(Soderstrom et al., 1990). Such extended treatment times are not acceptable to processors,who must quickly disinfest incoming product to meet market demands. To reduce treat-ment times, high-temperature CA treatments were investigated as a methyl bromidealtemative for codling moth in inshell walnuts (Soderstrom et al., 1996a). Temperatures(39°C, 41°C, 43°C, and 45°C) selected were those suitable for walnut dehydration withoutadversely affecting quality. Treatment atmospheres were 98 kPa CO2 in air, 0.5 kPa O2 inN2, and a simulated combustion atmosphere of 0.5 kPa O2, 10 kPa CO2, and the balance N2.

Elevated temperatures dramatically reduced treatment times for all atmospheres, includ-ing normal air. The most effective treatment tested was 98 kPa CO2 and 60% RH, withestimated probit 9 values of 3.6 and 6.6 h for 45°C and 43°C, respectively.

Based on the results found in Soderstrom et al. (1996a), a prototype treatment chamberfor rapid application of high temperature alone or with CA was designed and tested fordisinfesting walnuts of diapausing codling moth larvae (Soderstrom et al., 1996b). Thechamber was made of fiberglass insulated polyvinyl chloride pipe, and was designed toallow quick heating and controlled atmosphere recirculation under air tight conditions.The chamber held a mass of about 30 kg of inshell walnuts that was 1.2 m deep and 0.3 min diameter. Air flow during the initial heating phase was 5.7 m3 jmin, which was reducedto 1.4 m3 jmin during temperature maintenance. Target temperatures were reached inabout 1 h. Treatments evaluated were normal air, 0.5 kPa O2 (in nitrogen), or 98 kPa CO2

(balance air) at 43°C, and treatment exposures were based on estimated LT95 levelsderived from Soderstrom et al. (1996a) (45.2 h for air, 14.6 h for 0.5 kPa O2, and 5.2 h for98 kPa CO2). All treatments exceeded 95% mortality, and any surviving larvae weremoribund and subsequently died.

An early economic analysis of the use of ionizing radiation as an altemative to chemicalfumigants for dried fruit and nut disinfestation used scenarios that included GLOA treat-ments (Rhodes and Baritelle, 1986). Although considerably more expensive thanfumigants,GLOA treatments had a clear advantage over irradiation for almonds, walnuts, raisins,and prunes during long-term storage. A more current economic analysis was carried outfor commercially available methyl bromide altemative treatments for disinfestation ofalmonds and walnuts, including phosphine fumigation, ionizing irradiation, and CA stor-age (Aegerter and Folwell, 2001). Costs for each altemative were estimated and compared tobenchmark methyl bromide fumigation costs. Irradiation costs ranged from 2x to 14x thebenchmark, while CA storage ranged from 1.7 x to 2.5 x the benchmark costs. PH3 was usedonly to treat almonds, and its costs were only slight1y higher than the benchmark. In allscenarios, CA was less expensive than irradiation. It was concluded that while thesealtemative treatments could effectively control insect populations in walnuts and almondsat a level comparable to methyl bromide, further research is needed to obtain approval for

their use as quaradone have improv

Navarro et al. (treatrnent times fatreatrnent containlcontrol in durableexposures to loweggs, diapausing 1the most tolerant aplastic containers(inshell alrnondsrequired extendedtreatments at 25°(

Pecans are ofterand aids invasionatrnospheres to diatmosphere of 30tions and compleelevated CO2 leve

Macadamia nutnut borer, Hypothtmoisture nuts on .may continue toincluding CA treéTreatment chamhwith either N2 DI

mortality was lo~the gas by the husmortality of adultconcentration WhEpest mortality, thlA 14 day treatmeHolding nuts undat the peak of the

20.2.3 Combinat

Combining an inistorage treatmentaltemative insectraisins (Johnson Ebrane gas separalbags and sealed teinitial CA disinfesof in-shell nuts) wTest insects for thl(Cadra figulilella),four bins of prod\a preparation co:storage, or mainbstorage pest of dI

20.2.3 Combinations with Other Treatments

Combining an initial, short-term CA disinfestation treatment with long-term protectivestorage treatments in an integrated control program was shown to be promising as analtemative insect control strategy for walnuts (JoOOson et al., 1998) and for almonds andraisins (JoOOson et al., 2002). CA atmospheres were obtained with a hollow fiber mem-brane gas separation system in treatment rooms equipped with standard air expansionbags and sealed to a pressure half-life of 1 min after being pressurized to 0.245 kPa. For theinitial CA disinfestation treatment, 8 bins of product (3.6 MT of field-run raisins, or 1.8 MTof in-shell nuts) were treated at 0.4 kPa O2 for 6 days at 25°C after a purge period of 2 days.Test insects for the initial disinfestation treatment were navel orangeworm and raisin moth(Cadra figulilella), both common field pests of these products. After initial disinfestation,four bins of product were moved to protected storage environments, either treatment witha preparation containing Indianmeal moth granulosis virus, low temperature (:S;10°C)storage, or maintenance CA (5 kPa O2), Mated female Indianmeal moths, the most seriousstorage pest of dried fruits and nuts, were added to the storage rooms each week.

their use as quarantine treatments. Again, rising fumigant prices since this analysis wasdone have improved the competitiveness of CA treatments relative to methyl bromide.

Navarro et al. (2003) showed the effectiveness of increased temperatures at reducingtreatment times for both CO2 and vacuum, and demonstrated the utility of flexible plastictreatment containers for the application of vacuum treatments for stored product insectcontrol in durable commodities. JoOOson and Valero (2005) showed that relatively shortexposures to low pressures of 6.66 kPa could control tree nut pests. Nave! orangewormeggs, diapausing Indianmeal moth, and diapausing codling moth larvae were found to bethe most tolerant at temperatures of 25°C and 30°C. Field trials treating almonds in flexibleplastic containers were done under both winter (nutmeats in wooden bins) and summer(inshell almonds in 50 kg poly bags) conditions. Winter treatments at 6.3°C-10SCrequired extended treatment times of more than 13 days to get complete control. Summertreatments at 25°C-29SC provided complete control with a 48 h exposure.

Pecans are often infested with pecan weevil (Curculio caryae), which damages nutmeatsand aids invasion of mold (Wells and Payne, 1983). Wells and Payne (1980) used high CO2

atmospheres to disinfest pecans of this pest, and reduce the level of storage fungi. Anatmosphere of 30 kPa CO2 and 21 kPa O2 in N2 was effective at reducing fungal popula-tions and completely killed weevils, but low O2 atmospheres (1 kPa) with or withoutelevated CO2 levels was noto

Macadamia nuts produced on the island of Hawaii are often infested with the tropicalnut borer, Hypothenemus obscurus (F.) (Delate et al., 1994). The beetle prefers to attack lowmoisture nuts on the ground or "sticktight" nuts remaining on the tree, and populationsmay continue to increase in nuts waiting processing. Postharvest control techniques,including CA treatments, were evaluated for control of this pest (Delate et al., 1994).Treatment chambers containing infested nuts and held at 24°C-30°C were flushed dailywith either N2 or CO2 to maintain gas concentrations of 2':95 kPa. Tropical nut borermortality was lower in nuts with the husk than without, possibly due to absorption ofthe gas by the husk. Unhusked nuts treated with 2':95kPa CO2 for 6 days resulted in 97.3%mortality of adult beetles, while all adult insects were killed at this exposure time andconcentration when nuts were husked. Although CO2 treatments provided slightly higherpest mortality, there were concerns over reduced nut quality after extended exposures.A 14 day treatment of 2':95 kPa N2 was required for 100% mortality in unhusked nuts.Holding nuts under CA storage was suggested as a means of alleviating processing loadsat the peak of the season without increasing damage due to the beetle.

Dried Fruits and Tree Nuts 517

518 Modified and Controlled Atmospheres Dried Fruits and In

TABLE 20.3

Survival of Target Insects after Disinfestation Treatment of 0.4 kPa O2

for 6 Days at 25°C

Number of Insects Treated Adults Emerged Survival ('Yo)Treabnent

Almonds (navel orangeworm as test insect)"Untreated control 403CA 800

Walnuts (navel orangeworm as test insect)bUntreated control 604CA 1194

Raisins (raisin moth as test insect)"Untreated control 400CA 800

393.0 97.540.0 5.0

487.0 80.64.0 0.3

251.0 62.7O O

20.3 Effects onAlthough most of tare far short-terrnsuggested as mearBecause tree nutsrancidity (Watkins,ment of rancidity. jto improve the sheeffects of controllednecessary for insectrancidity, MAs incl

a Johnson et al. (2002).b Johnson et al. (1998).

The initial disinfestation treatment was effective in controlling both test insects(Table 20.3), although there was some evidence that longer exposures might be necessaryagainst raisin moth, or against diapausing navel orangeworm (JoOOson et al., 2002). Allprotective treatments were effective in controlling Indianmeal moth (Table 20.4) andoverall product quality was unaffected by any storage treatment. Storage under CA wasthe most efficacious in preventing infestation by Indianmeal moth, but the sealed storageprevented ready access to the product and the low O2 atmosphere conditions presentworker safety considerations that do not exist for the other methods. Extensive sealing offacilities and equipment for generating CA would be required to provide the neededstorage conditions, and would result in considerable expense to processors. However,use of new tecOOologies such as flexible plastic storage containers may help to bringthese costs down.

TABLE 20.4

Indianmeal Moth Incidence and Related Damage in Almonds, Walnuts,and Raisins after Extended Storage at 5 kPa O2

20.3.1 Almonds (1

Kader (1996)statestorage, and that 1

growth. The effec86-89 kPa N2, ancshelled and inshell(Guadagni et al., 1~stable than alrnondlow O2 atrnosphenstability during stofor both meats and

The storage beha'Nonpareil') was irspheres (air and NPascual, 2003).N2

were observed beta-tocopherol contelthe increase of thecontents were alwa

Note: Each week mated females (5 for almonds and walnuts, and 15 for raisins) wereadded to the stored producto

a Johnson et al. (2002).b Johnson et al. (1998).

Raisins (samples taken after 40 weeks)aUntreated control 3.2CA O

Almonds (samples taken after 16 weeks)"Untreated control 482.5eA O

Walnuts (samples taken after 16 weeks)bUntreated control 81.0CA O

20.3.2 Apricots ('

The effects of dryifresh apricot tissuealso monitored dlapricots. Apricots\Dehydrated aprica(100 kPa N2, 20 kl40 kPa N2, 100kP,during drying pretIn particular, acetidegradation of pe<perature used. eAair. The content oflosses were observ

Minor Serious

4.4 28.0O O

12.6 35.1O O

13.2O

Indianmeal Moth DamageLive Indianmeal

MothTreatment

20.3 Effects on Quality

Although most of the uses of controlled atmospheres on bulk-stored dried fruits and nutsare for short-term insect disinfestation, modified or controlled atmospheres are oftensuggested as means to improve shelf life in these products, particularly for tree nuts.Because tree nuts are high in polyunsaturated lipids they are susceptible to oxidativerancidity (Watkins, 2005). Storage under low O2 conditions may greatIy slow the develop-ment of rancidity. As such, vacuum packaging or N2 flushed packaging is often suggestedto improve the shelf life of tree nuts. ConsequentIy, much of the research on the qualityeffects of controlled atmospheres on tree nuts deals with exposures much longer than thosenecessary for insect disinfestation treatments. A1though dried fruit quality is less affected byrancidity, MAs including elevated CO2 may reduce fruit darkening and improve shelf life.

20.3.2 Apricots (Prunus armeniaca)

The effects of drying, dehydration, and storage under CA on cell wall components offresh apricot tissues were studied by Femenia et al. (1998). The degree of browning wasalso monitored during storage by measuring color and S02 content of dehydratedapricots. Apricots were treated with Na2S20S and acetic acid solutions before dehydration.Dehydrated apricots were then stored at 25°C in air or in five different CA treatments(100 kPa N2, 20 kPa CO2 and 80 kPa N2, 40 kPa CO2 and 60 kPa N2, 60 kPa CO2 and40 kPa N2, 100 kPa CO2). The yield of apricot cell wall material decreased substantiallyduring drying pretreatments and also during dehydration, by 9.5% and 4.7%, respectively.In particular, acetic acid solubilized a large amount of pectic polysaccharides. Furtherdegradation of pectic substances occurred during drying, probably due to the high tem-perature used. CA storage retarded browning in comparison to the sample stored underair. The content of S02 decreased markedly for the sample stored in air, whereas graduallosses were observed for CA-stored samples. In general, samples stored in CA containing

20.3.1 Almonds (Prunus dulcis)

Kader (1996) states that O2 is the most important atmospheric component in almondstorage, and that high O2 concentrations result in an increase in rancidity and moldgrowth. The effect of insecticidal GLOA treatments (>1 kPa O2, 9-9.5 kPa CO2,86-89 kPa N2, and 1 kPa Ar) on almond flavor quality was determined by exposingshelled and inshell 'Nonpareil' almonds continuously to the atmosphere for 1-12 months(Guadagni et al., 1978a). At normal atmospheres, inshell almonds were found to be morestable than almond meats at both 18SC and 27°C, but no differences were detected underlow O2 atmospheres. Low O2 was as effective as low temperature (18°C) in maintainingstability during storage, and caused less off-flavor development than normal atmospherefor both meats and inshell almonds.

The storage behavior of four varieties of almond ('Marcona,' 'Planeta,' 'Desmayo,' and'Nonpareil') was investigated at two temperatures (8°C and 36°C), two packaging atmo-spheres (air and N2) and two treatments (raw and roasted) for up to 9 months (Garcia-Pascual, 2003). N2 packaging resulted in O2 levels <0.25 kPa. No significant differenceswere observed between air and N2 packaging for moisture, fat content, peroxide value,u-tocopherol content, and level of aflatoxins. A significant relationship was found betweenthe increase of the peroxide value and the decrease of a-tocopherol contento The aflatoxincontents were always lower than 0.5 µg/kg.

519i Dried Fruits and Tree Nuts

520 Modified and Controlled Atmospheres Dried Fruits and T;

low e02 levels (20 and 40 kPa) showed minor disruption of cell wall components andbetter initial characteristics of dehydrated apricots.

20.3.3 Chestnuts (Castanea sativa)

Anelli et al. (1982) reported that chestnuts stored in 2 kPa O2 plus 20 kPa e02 at osehad an increased rate of sugar metabolismo These chestnuts have also been reported tohave lower glutamine content as the CO2 level increased from 5 to 20 kPa. A prestoragetreatment of 80 kPa CO2 for 10 days followed by 80-90 days of storage at O°Cwas the bestmethod of reducing Sclerotinia rot in chestnuts (Bertolini and Tonini, 1983). Rouves andPrunet (2002) examined various storage tecOOiques for chestnuts, including low tempera-ture CA (2 kPa O2 plus 5 kPa CO2 at -1°C or 1°C). For the varieties 'Marigoule' and'Bouche de Betizac' water loss was prevented, mold reduced, and taste maintained.The varieties 'Comballe' and 'Marron de Goujonac' did not benefit from CA storage.ehestnuts kept under 20 kPa CO2 and 2 kPa O2 had lower rot and insect developmentafter 150 days of storage, while treatment with 2.5 kPa CO2 and 1.5 kPa O2 was lesseffective (Mignani and Vercesi, 2003).

20.3.4 Dates (Phoenix dactylifera)

Rygg (1975) suggested inert gas or vacuum packing for storage of high-moisture dates.Mohsen et al. (2003) noted that vacuum packaging is a useful technique for reducingdarkening of the date for long-term storage. Mutlak and Mann (1984) reported thatbrowning can be inhibited at low oxygen potentials. CA (5, 10, or 20 kPa CO2) at ooeextended storage period and maintained quality of fully mature 'Bahri' date fruit(AI-Redhaiman, 2005). The quality of fruit stored under 20 kPa COz was maintainedfor up to 26 weeks compared to 17 weeks for fruit held under 5 and 10 kPa CO2 andonly 7 weeks for fruit kept in normal air. A 20 kPa CO2 maintained acceptable levels of fruitsoluble solids, total sugar, total tannins, and caffeoylshikimic acid.

20.3.5 Figs (Ficus carica)

The effect of insecticidal GLOA treatments on the quality of dried figs was studied byDamarli et al. (1998). An exothermic generator that maintained 1 kPa O2 and 10-15 kPa e02

atmosphere composition at 35°e for 30 h was used to treat 8.6 MT of producto Under theseconditions, considered to be optimal for controlling insect populations, there were noobserved negative effects on fruit weight, moisture, color, total sugar content, or acidity.Similarly, the effect of e02 proposed for insecticidal treatments on dried fig quality wasexamined by Meyvaci et al. (2003a). Exposure to 100 kPa CO2 for 45 days caused colorchanges as measured on the Hunter color scale with a colorimeter. In the Hunter scale,L measures lightness and varies from 100 for perfect white to zero for black, a measuresredness when positive, gray when zero, and greenness when negative, and b measuresyellowness when positive, gray when zero, and blueness when negative. In CA-treatedfigs, mean L values decreased from 57.9 to 51.7, a values increased from 9.8 to 11.7, andb values decreased from 30.6 to 27.7. In studies to improve shelf life of dried figs, Meyvaciet al. (2003b), packaging in 100 kPa N2, 20 kPa e02 in N2, or under vacuum was examinedfor up to 7.5 months of storage. Figs stored under N2 were darker than figs stored innormal air, while e02 storage reduced darkening slight1y. Figs stored under N2 alsohad increased sugar formation. Vacuum packaging resulted in the darkest fruit, butreduced sugar formation. Storage under either N2 or CO2 controlled mold growth inrehydrated figs for 3 months more than storage at ambient conditions.

20.3.6 Hazelnuts

Hazelnut is charalin unsaturated fal2001). Storage conhelp preserve quaprotective measUI1 year or more (Estore 'Piemontesenitrogen (~99.5kJable to that resul(3°C-6°C, 50%-60'CA conditions bystored with diffen(7°C and 25°C),aring the peroxide "acids and sensorycaused significantsignificantly redw

20.3.7 Macadami

As with other nut!or nitrogen flush(

20.3.8 Pecan(ea

Shelf life of pecanusing CO2 as the Ithe developmentpackaging materiapackaging can Offl

20.3.9 Pine Nuts

Pine nuts (piñone:with volcanic dustained their moislcondition (Estevez

20.3.10 Pistachio

A1though pistachi,O2 «0.5 kPa), v,stability {Labavitcpistachio nuts weJat the monolayer 1

content for storagambient conditiorfatty acid loss at ]prediction of the ri

20.3.7 Macadamia (Macadamia integrifolia)

As with other nuts, prolonged exposure to O2 results in rancidity, and vacuum packagingor nitrogen flush offers protection from O2 (Cavaletto, 2004).

20.3.9 Pine Nuts (Araucaria spp.)

Pine nuts (piñones), Araucaria araucana, stored in different MA (polyethylene bags linedwith volcanic dust) and CA (10-5 kPa CO2-02, and 20-5 kPa COT02) conditions main-tained their moisture and starch content, and 20-5 kPa COT02 was the optimum CAcondition (Estevez and Galletti, 1997).

20.3.8 Pecan (Carya iIIinoinsis)

Shelf life of pecans may be increased by storage in 2-3 kPa O2 in N2, and less frequentIyusing CO2 as the balance gas (Maness, 2004).Storage in <2 kPa O2 for 52 days can causethe development of a "fruity" flavor (Santerre et al., 1990). O2 transmission rates forpackaging materials should be >0.08 mL/IOOcm per 24 h (Dull and Kays, 1988).Vacuumpackaging can offer a further benefit of protection from breakage.

521Dried Fruits and Tree Nuts

20.3.6 Hazelnuts, Filberts (Corylus spp,)

Hazelnut is characterized by high oil content (about 65% of its kernel weight) and is richin unsaturated fatty acids, and therefore highly sensitive to rancidity (San Martin et al.,2001).Storage conditions that are capable of retarding lipid oxidation and hydrolysis willhelp preserve quality. Reduced temperature may be effective in combination with otherprotective measures such as vacuum packaging in extending roasted kernel shelf life to1 year or more (Ebraheim et al., 1994).Keme et al. (1983) reported that it is possible tostore 'Piemonteses,' 'Roman,' and 'Ákcakoca' hazelnuts at ambient temperature undernitrogen (:2:99.5kPa) for prolonged periods of time with a loss of quality that is compar-able to that resulting from storage conditions at low temperatures and controlled RH(3°C-6°C,50%-60%RH). Hazelnut ('Negret') quality was studied after storage in selectedCA conditions by San Martin et al. (2001). The shelled and unshelled hazelnuts werestored with different oxygen levels (1, 5, 10, and 20 kPa O2) at two different temperatures(7°Cand 25°C),and quality of the hazelnuts during storage was monitored by determin-ing the peroxide value, acid value, K232 and K270 indices, percentage of unsaturated fattyacids and sensory analysis. After 1 year in storage, none of the storage conditions testedcaused significant rancidity. Storage in atmospheres with O2 levels lower than 10 kPasignificantIy reduced autoxidation and the low temperature delayed lipid rancidity.

20.3.10 Pistachio (Pistacia vera)

Although pistachios are fairly stable stored in normal air at 20°C, storage under reducedO2 «0.5 kPa), vacuum packaging or N2 flushed packaging further improves flavorstability (Labavitch, 2004a). Changes in fatty acid composition and peroxide value ofpistachio nuts were studied during storage at 10°C-30°Cunder either air or 98 kPa CO2

at the monolayer moisture content of pistachios (considered to be the most stable moisturecontent for storage of dehydrated products), and were compared to those stored underambient conditions (Maskan and Karatas, 1998).Use of the Arrhenius model to predictfatty acid loss at 10°C,20°C, and 30°C under both atmospheric conditions, together withprediction of the rate and extent of oxidation during storage, was also investigated. Storage

522 Modified and Controlled Atmospheres

TI

--Dried Fruits and 1

of pistachio nuts under CO2 provided the greatest stability in relation to fatty acid loss,peroxide values, and free fatty acid formation, especially at 10°C. The Arrhenius modelrevealed that storage of nuts under CO2 was more temperature sensitive, and morelinolenic acid was lost by oxidation than linoleic acid. Comparison of samples stored atambient conditions with those stored at or near the monolayer moisture content and underCO2 storage showed the latter samples to be more stable.

Storage stability, oil characteristics, and chemical composition of whole-split pistachionuts (Pistachia vera L.) were determined on samples stored in CA (2 kPa air, 98 kPa CO2),

air at the monolayer value at 10°C, 20°C, 30°C, and at ambient conditions (Medeni andSukru, 1999). Most oxidation was observed under ambient storage conditions. CO2 espe-cial1yimproved the storage stability at low temperatures. Using the reaction rate constantsof peroxide formation, it was revealed that as temperature increased, the ratio of rateconstants (air /C02) approached 1, which means that no significant difference existedbetween air and CO2 storages at 30°C. The oxidation activation energies were 8.33 and13.39 kcal/mol under air and CO2 storage, respectively.

20.3.11 Raisins (Vitus vinifera)

Guadagni et al. (1978b) examined the effect of long-term exposure to insecticidal GLOAtreatments on flavor stability of field-run Thompson seedless raisins. After 12 monthstorage under GLOA (>1 kPa O2, 9-9.5 kPa CO2, 86-89 kPa N2, and 1 kPa Ar) at 18SCand 27°C, raisin flavor, based on taste panel evaluations, was equal or superior to that ofraisins stored under normal air.

The effect of a low O2 atmosphere generated by the addition of a commercial O2

absorber on fruit color of golden-colored, sultana raisins stored in hermetically heat-sealedgas barrier bags at 15°C, 22SC, and 30°C was assessed over a 28, 56, or 84 day storageperiod (Tarr and Clingeleffer, 2005). Fruit color changes were measured using the cmtristimulus L, a, b measuring system. Low storage temperature (15°C) and low O2 atmos-phere both maintained fruit color during the experimental storage regimes. There weresignificant negative effects on fruit color at the higher temperature (30°C) and longerstorage period without a low O2 atmosphere.

20.3.12 Walnuts (Juglans regia)

Shelf life can be extended by storage in <1 kPa O2, O2 <0.5 kPa (balance N2) or C02levelsabove 80 kPa in air can be effective in insect control (Labavitch, 2004b).

20.4 Conc1usions

Low moisture dried fruits and tree nuts are relatively tolerant of many kinds of MA or CA,making their use for insecticidal treatments or for shelf life extension attractive. AlthoughCA treatment times for bulk-stored product are usually much longer than those for methylbromide, at temperatures ;::::30°C,they are often comparable to phosphine fumigation.For applications that do not require rapid tumaround of product, such as yard stacks ofraisins, CA treatments may be appropriate. CurrentIy, the biggest barrier to widescaleadoption of CA for disinfestation of bulk dried fruits and nuts is the increased costs,although for high-value organic product, the added cost is more acceptable. MA inpackaging (N2 flushed or vacuum packed) as a means of improving shelf life is currentIyused, most often by processors of tree nut products.

20.5 Future RI

Much of the cost I

either building nIleaks in poorly se,sive, flexibleplaslthe use of eA trereduced by moreFurther researchiAn important disifor insect control.times, but may aMethods to cheaFneeded.

ReferencesAegerter, A.F. and

and quarantinProcessing and

Al-Redhaiman, K.Nphere eonditio

Anelli, G., F. Meneal'impiego delll

Annis, P.C, 1987.1knowledge. InConference onpp. 128-148.

Bell, CH. 2000. FunBell, CH. and N. S

of the Medite:233-247.

Benhalima, H., M.eproduet insec1Products Reseal

Bertolini, P. and GSclorotinia psetof Refrigeration

Brandl, D.e., E.L.Siing differentAmyelois tram828-830.

Campbell, B.C, R.J.harvest aflato:Toxin Reviews

Cavaletto, CG. 20Q.Nursery Stoc~No. 66, http://

Curtis, CE., R.K. CPyralidae) inflEnvironmental

References

Much of the cost of eA treatments for bulk-stored dried fruits and nuts is associated witheither building new gastight storage structures or retrofitting old storage facilities. Gasleaks in poorly sealed storages also drive up the cost. The recent development of inexpen-sive, flexible plastic containers capable of maintaining treatment gas levels should makethe use of CA treatments more affordable. Costs for bulk CA treatment may be furtherreduced by more fully exploring the use of vacuum under these flexible plastic containers.Further research is needed to integrate this tecOOology with existing processing methods.An important disadvantage to CA bulk treatments is the lengthy treatment times neededfor insect control. Treatment at elevated temperatures is well known to decrease treatmenttimes, but may add considerably to the cost or result in product quality degradation.Methods to cheaply apply CA at high temperatures and protect product quality are alsoneeded.

Aegerter, A.F. and RJ. Folwell. 2001. Selected altematives to methyl bromide in the postharvestand quarantine treatment of almonds and walnuts: An economic perspective. Journal of FoodProcessing and Preservation 25: 389--410.

Al-Redhaiman, KN. 2005.Chemical changes during storage of 'Barhi' dates under controlled atmos-phere conditions. HortScience 40: 1413-1415.

Anelli, G., F. Mencarelli, F. Nardin, and e. Stingop. 1982.La conservazione delle castagne mediantel'impiego delle atmosfere controllate. Industrie Alimentari 21: 217-220.

Annis, P.e., 1987. Towards rational controlled atmosphere dosage schedules: A review of currentknowledge. In: Donahaye, E., Navarro, S. (Eds.), Proceedings of the Fourth International WorkingConference on Stored-Product Protection, Tel Aviv, Israel, September 21-26, 1986. Bet Dagen,pp. 128-148.

Bell,CH. 2000.Fumigation in the 21st century. Crop Protection 19:563-569.8ell, CH. and N. Savvidou. 1999. The toxicity of Vikane (sulfuryl fluoride) to age groups of eggs

of the Mediterranean flour moth (Ephestia kuehniella). Journal of Stored Products Research 35:233-247.

Benhalima, H., M.Q. Chaudhry, KA. Mills, and N.R Price. 2004. Phosphine resistance in stored-product insects collected from various grain storage facilities in Morocco. Journal of StoredProducts Research 40: 241-249.

Bertolini, P. and G. Tonini. 1983. Prestorage, high carbon dioxide treatment for the control ofSclorotinia pseudotuberosa (Rehm) rot in chestnuts. Proceedings of the 16th International Congressof Refrigeration, Paris, France, pp. 231-236.

Brandl, D.G., E.L.Soderstrom, and F.E. Schreiber. 1983.Effects of low-oxygen atmospheres contain-ing different concentrations of carbon dioxide on mortality of the navel orangeworm,Amyelois transitella (Walker) (Lepidoptera: Pyralidae). Journal of Economic Entomology 76:828-830.

Campbell, B.e., RJ. Molyneux, and T.F. Schatzki. 2003.Current research on reducing pre- and post-harvest aflatoxin contamination of US almond, pistachio, and walnut. Journal of Toxicology:Toxin Reviews 22: 225-266.

Cavaletto, e.G. 2004. Macadamia nut. In: The Commercial Storage of Fruits, Vegetables, and Florist andNursery Stocks, Ke. Gross, CY. Wang, and M. Saltveit (Eds.), USDA Agricultural HandbookNo. 66, http://www.ba.ars.usda.gov/hb66/contents.html

Curtis, e.E., RK Curtis, and KL. Andrews. 1984. Progression of navel orangeworm (Lepidoptera:Pyralidae) infestation and damage of almonds on the ground and on the tree during harvest.Environmental Entomology 13: 146-149.

523Dried Fruits and Tree Nuts

20.5 Future Research Needs

524 Modified and Controlled Atmospheres

T1

---Dried Fruits and T

Damarli, E., G. Gun, G. Ozay, S. Bulbul, and P. Oechsle. 1998. An alternative method instead ofmethyl bromide for insect disinfestation of dried figs: Controlled atmosphere. Acta Horticulturae480: 209-214.

Delate, KM., J.W. Armstrong, and V.P. Jones. 1994. Postharvest control treatments for Hypothenemusobscurus (F.) (Coleoptera: Scolytidae) in macadamia nuts. ¡ournal of Economic Entomology8: 120-126.

Ding, W., J.-J. Wang, Z.-M. Zhao, and J.H. Tsai. 2002. Effects of controlled atmosphere and DDVP onpopulation growth and resistance development by the psocid, Liposcelis bostrychophila Badonnel(Psocoptera: Liposcelididae). ¡ournal of Stored Products Research 38: 229-237.

Donahaye, E., S. Navarro, and M. Rinder. 1994. The influence of temperature on the sensitivity of twonitidulid beetles to low oxygen concentrations. Proceedings of the 6th lnternational WorkingConference on Stored Product Protection, Canberra, Australia, ApriI17-23, 1994, pp. 88-90.

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21EconomicStorage all

Edmund K. Mup

CONTENTS21.1 Backgrour21.2 lntroducti(21.3 The Fruit!

21.3.1 u.~21.3.2 Cal21.3.3 Dis21.3.4 Ap21.3.5 Sto

21.4 Modified 1

21.5 Packaging21.6 RegulatoI')21.7 Industry P21.8 Consumer21.9 Surnrnary.21.10 Future Re!References ..

21.1 Backgro\

This chapter diseland modified atITheir uses span ¡

fruit and vegetabland other cook-dproducts; (f) cookhas economic irn]socioeconornic al

by demand for 1

globalization of 1

distances and thTlcompetitive foodenhanced produ<