Postharvest Challenges for Organically GrownOrchard FruitPenelope Perkins-Veazie

USDA -ARS, South Central Agricultural Research Laboratory, 911 Highway 3 West, Lane, OK 74555Gene Lester

USDA -ARS, SARC, Crop Quality and Fruit Insects Research Unit, 2413 E. Highway 83,Building 200, Weslaco, TX 78596

Additional index words, production system, grapefruit, antioxidant, National Organic Program

Abstract. Switching from conventional to organic production requires a philosophical shift and recognition of differentproduction system inputs plus postharvest handling challenges. First, and most obvious, is the replacement of common andreadily available manufactured chemical inputs with approved "natural" or "nature-made compounds" (i.e., organic) fororganic production. Many of these organic inputs may require new knowledge for successful implementation or may be lesseffective than conventional counterparts. Good orchard practices (e.g., cleanliness, bookkeeping) must be followed in anorganic system just as they are in a conventional system. In addition, if processing (cider, sauces, or frozen fruit-sectioningpreparations) is going to be part of the harvested operation, approved organic products will have to be used, and strictguidelines followed and documented. Organic versus conventional production system inputs can affect changes in thephytochemical and nutrient content of foods, and even change ripening patterns, which can affect harvest operations,marketing qualities, and consumer acceptance.

For both conventional and organic pro-duction systems, market-quality factors arethe same. Fruit should be free of injury anddecay, have appropriate color and shape,and have typical texture and flavor. Althoughconsumers may be willing to overlook a fewblemishes at fruit stands or farmers' markets,retail market-destined fruit must be of goodquality and of varietal recognition. For exam-ple, 'Red Delicious' apples should be fully redand of elongated shape, not green and round.Fruit with puncture wounds or bruising leadsto fungal colonization and must be regularlyculled to eliminate contamination of adjacentfruit and to retain food safety. Retail-mar-keted fruit need to be of U.S. Department ofAgriculture (USDA) No. 1 or Fancy gradesfor production-type fruits because competi-tion for purchasing needs to justify not onlythe price differential on the one hand, but thepesticide residue issues on the other.

POSTHARVEST HANDLINGPRACTICES

Postharvest and handling systems ofcleanliness and temperature storage are gen-erally the same for conventional and organicorchards, and good practices must be fol-lowed and documented (Suslow, 2000). Fruitshould be of the proper maturity. Dependingon the species, a crop may ripen earlier orlater in an organic system compared with aconventional system. Thus, if organic fruitare being handled and stored for the first time,careful monitoring of the fruit should be donefor the first few production and handlingcycles until a clear ripening or storage pro-tocol pattern emerges. Effective coolingshould be done in both systems.

In a certified organic system, integrity ofthe organic product must be maintained fromorchard to consumer. The most important

Received for publication 12 Jan. 2007. Acceptedfor publication 17 May 2007.

aspect of this is that an organic system planmust be in place and adhered to, and recordsmust be maintained. No comingling oforganic and conventional products isallowed. Although this rule doesn't preventorganic and conventional produce beingshipped in the same semi truck, it doesmandate that organic fruit be packed inseparate boxes preventing contact with con-ventional products and be labeled as organic.In addition, the packaging materials fororganic fruit cannot contain prohibited sub-stances. For instance, packing materialimpregnated with a nonorganic, but U.S.Food and Drug Administration-approvedfungicide allowable for conventional pro-duce, cannot be used in organic producepackaging systems (Federal Register, 2006).

Conventional practices and chemicalsacceptable for use in a postharvest organicprogram include controlled-atmosphere (CA)storage, sulfur dioxide, and ethylene gas(Table 1). Chlorine, which is used exten-sively in conventional systems for washingproduce, can be used for organic systemsif the residual chlorine level does not exceed4 ppm. Substances allowed under conven-tional practices must be checked to make surethey are in compliance with organic regula-tions. For instance, waxes with syntheticsubstances are not allowed in postharvesthandling of organically certified fruit, andthe shipping container must be labeled withthe wax used (Suslow, 2000). In some cases,approval of treatments has not been done,such as in the use of ultraviolet light forsanitizing fruit surfaces. Guidelines ofapproved substances and a listing of com-pounds that may be approved for use can befound in the Federal Register (2005).

For processing operations, an organicsystems plan (OSP) must be in effect. Thisplan is similar to Hazard Analysis and CriticalPoints (HAACP), but the critical points in anOSP are the recognition and eliminationof places where nonorganic material contam-

ination could occur (Plotto and Narciso,2006). Processed organic products can beblended with nonorganic products, but themixture no longer can be sold as 100%organic, and cannot carry the USDA organiclabel. Nevertheless there are four categories oforganic products, depending on the amount oforganic product present. They include 100%organic, organic (95%), made with organicingredients (70% to 95% organic), and noorganic (more than 70% nonorganic). In thearena of processing, the formulations andprocessing systems need to be verified bythe Organic Materials Review Institute,because many areas of confusion and compli-cation abound. In addition, import regulationsfor processed organic products differ fromcountry to country, thus organic requirementsof the perspective country should be checkedbefore export (Plotto and Narciso, 2006).

As with conventional systems, surfacesused for fresh or processed product prepara-tion should be kept clean. However, thecleaning agents can differ between organicand conventional systems. For instance, qua-ternary ammonia products are not allowed inorganic systems on food contact surfacesbecause they leave a residual sanitizer (Plottoand Narciso, 2006; Suslow, 2000). Make sureall practices are documented as per standardsanitation operating procedure.

Food safety issues are a concern with allhorticultural crops. In organic and conven-tional systems, use of animal manure orcompost teas, although strictly regulated(Organic Foods Production Act of 2005),continues to pose safety issue concerns toconsumers. In comparisons of organic andconventional production systems, the microbi-ological load was found to be more dependenton the crop than on the system (Mukheijeeet al., 2004). Escherichia coli (not the 01 57:H7serotype) prevalence in certified organic pro-duce from samples taken across differentcommodities in Minnesota was not statistically

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different between organic versus conventionalsamples (Mukherjee et al., 2006).

ANTIOXIDANTS, NUTRIENTS, ANDPHYTOCHEMICALS

Brandt and Mølgaard (2001) have chal-lenged conventional thought by stating fruitsand vegetables contribute to human healthprimarily through secondary metabolites,rather than through proteins, carbohydrates,or minerals. Secondary metabolites can beeither helpful or harmful, depending on typeand dosage. They may include the well-known health-risking glycoalkaloids foundin tomato and potato, or health-promotingfiavonoids found in berries, as well as thewell-known healthful carotenoids found inmany fruits and vegetables. Antioxidantssuch a ascorbic acid, 3-carotene, and pheno-lic compounds (fiavonoids, fiavones, pheno-lic acids) are considered plant—human health-bioactive compounds that are efficient scav-engers of free oxygen radicals, or of freeradicals with strong oxidizing power such assome carcinogens. In addition, some of thesecondary metabolites, which also have anti-oxidant functions, are also considered vita-mins or vitamin precursors, such as ascorbicacid (vitamin C) and 3-carotene (provitaminA). Tests for individual antioxidant com-pounds, or an overall assessment of theantioxidant status of a fruit or vegetable caneasily be determined using total phenoliccontent, oxygen radical absorbing capacity,thiobarbituric acid reactive substances, total

oxyradical scavenging capacity, and ferric-reducing absorbing power assays (Table 2).

The relative merit of conventional versusorganic production systems on antioxidantlevels of fruit is one of the most prevalentthemes in the literature (Lester, 2006; Mag-kos et al., 2003; Woese et al., 1997; Wor-thington, 2001; Zhao et al., 2006). Bourneand Prescott, (2002) pointed out to determineproduce content differences critically in anti-oxidant levels arising from organic versusconventional production systems there is aneed for well-controlled research studies inthe human health bioactive compound arena,as well as in sensory quality and food safetystudies. Also, careful documentation andcommon production input usage continuesto be an issue (Lester, 2006; Zhao et al.,2006). Organically produced fruit is oftenbelieved to be higher in some healthfulantioxidants as a result of environmentalstresses stimulating plant defense systems,many of which contain antioxidants known tohave beneficial human health attributes(Brandt and Mo!gaard, 2001). For instance,plant fungal diseases can stimulate the shiki-mic acid or pheny!propanoid pathway, whichcan in turn stimulate phenylalanine ammonialyase, a key enzyme in phenylpropanoidsynthesis (Taiz and Zeiger, 1998). Pheny!-propanoids include anthocyanins, tannins,lignans, sti!benes, and a host of other pheno-lic compounds, many of which have reportedhealth attributes (Taiz and Zeiger, 1998).

The most common problem encounteredevaluating fruit from conventional versusorganic systems is in matching all production

variables common to both production sys-tems. The most common pitfalls are I) usingdifferent cultivars; 2) using fruit from onlyone production system, generally the organicsystem to determine phytochemicals; and3) using the same cu!tivar in each system,but systems are not matched for soil type,microenvironment, orchard age, or generalproduction (e.g., irrigation) or harvest (e.g.,fruit size, time of day, or position within thecanopy) practices. Although it is acceptableto compare organically produced fruit withpreviously published values for convention-ally grown fruit, it is cautioned that thesevalues are only a reference and not a truecomparison. Another potential pitfall inorganic versus conventional comparisons isavoiding bias for or against organic systems.

When comparing produce, both pre- andpostharvest variables need to be considered.When initiating a study, orchards should havethe same variety, soil type, and age of trees. Asample size should be similar and preferablyfrom a commercial orchard where inherentvariation can be minimized because of thelarge number of trees. Fruit should be har-vested at the same time, and replicates andlocation should be the same (e.g., trees incenter of orchard vs. outside, shaded vs. sunfruit). Postharvest handling and treatmentsshould be as similar as possible (same shad-ing, packaging, storage temperature, humid-ity, light, and duration). DeE!! and Prange(1992) did a comprehensive comparison ofapples from conventionally and organicallymanaged 'McIntosh' and 'Cortland' orchardsthat were located as closely to each other aspossible, and held apples in storage with orwithout CA. They found that cu!tivar andstorage significantly affected firmnessregardless of production system. Sensorypanelists were unable to detect significantdifferences in production method with regardto soluble solids content or titratable acidityafter storage, and no difference in applequality after storage was seen with produc-tion systems. Although not measured, it ispossible that a component such as vitamin Cor phenolic content was altered by the pro-duction system.

A scientific study example that matchedcommon production and harvest variables,incorporated antioxidant tests was conductedusing 'Rio Red' grapefruit, and providedmultiple orchard harvests over the entire pro-duction period (Lester, 2006; Lester et al.,2007) with 2 years of harvests. This 'RioRed' grapefruit study used orchards as sim-ilar as possible, with differences in produc-tion limited to those required for certifiedorganic and conventional systems (Table 3).A summary of the published results is pre-sented in Table 4. Organically producedgrapefruit had smaller fruit; a thinner, greenerpeel; and a higher juice yield than con-ventional fruit. Although juice from organi-cally grown grapefruit was higher in sugars,it was also higher in the bitter principle(naringin) and higher in acidity, and thereforerated more tart and less preferred by tastepanelists. Ascorbic acid was higher, and

Table 1. Storage/treatments for postharvest organic produce allowed under the National Organic Program(Federal Register, 2006).

Storage treatmentsControlled-atmosphere (CA) storage (high CO 2/I0w 02)Low-temperature storage (<5 °C)Forced air coolingHigh-temperature and CA storage for insect quarantineApplication of some volatiles (acetaldehyde, hydrogen peroxide)EthyleneFumigants based on naturally occurring forms, and from natural sourcesWaxes from camauba or wood-extracted sources without synthetic substancesSulfur dioxide

Sanitizers/Cleaners/DisinfectantsChlorine (when used at or below current state and federal water quality standards)OzoneHydrogen peroxidePeroxyacetic acidAcetic acidEthyl alcohol (must be from organic source)CA, controlled atmosphere.

Table 2. Comparative tests reported for evaluating antioxidant status of organically and conventionallygrown tree fruit (Lester et al.. 2007; Woese et al., 1997; Zhao et al., 2006).

MineralsVitamins Other Antioxidants'phylochemicalsP Vitamin CProtein Beta caroteneCaVitamin EDry matter LuteinMgVitamin ASugar compositionLycopeneNitrateB vitaminsDietary fiberAnthocyaninsP Acidity FuranocoumarinsFe Organic acidsFlavonoidsZn pH Oxygen radical absorbing capacityCu Free amino acidsFerric-reducing absorbing power

Thiobarbituric acid reactive substancesTotal oxyradical scavenging capacityTotal phenolic content

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lycopene content lower, in organic juicewhen compared with conventional juice fromfruit harvest at the same time. Lester et al.(2007) pointed out that ascorbic acid, lyco-pene, and sugars are all produced in thechloroplasts, with ascorbic acid synthesizedfrom glucose, and lycopene synthesis occur-ring as chloroplasts break down to chromo-plasts. Thus, the more green peel color oforganic grapefruit indicates more chloro-plasts, which means active photosynthesisproducing more glucose to be converted tomore ascorbic acid, and less lycopenebecause of more intact chloroplasts.

SUMMARY

Postharvest handling of fruit from organicorchards must be rethought and possiblyretooled. Although the basics of orchard

management are the same for conventionaland organic systems, the treatments andmethods of production system inputs radi-cally differ. Currently, the greatest unknownand potentially the most challenging topic toresearch is to determine whether organicallyproduced fruit will inherently have reducedpostharvest shelf life problems and perhapsbetter quality compared with conventionallyproduced fruit. Postharvest shelf life prob-lems that are of minor importance today as aresult of research-developed synthetic chem-ical treatments may reemerge as major prob-lems with certified organic systems,disallowing these treatments. Thus, thismay require novel approaches to solvingpossible shelf life issues in an organic system.Also, it is possible that postharvest practicesapproved for certified organic fruit may alterproduct appearance, human health bioactive

Bourne, E. and J. Prescott. 2002. A comparison ofthe nutritional value, sensory qualities, andfood safety of organically and conventionallyproduced foods. Crit. Rev. Food Sci. Nutr.47:1-34.

Brandt, K. and J.P. Mølgaard. 2001. Organicagriculture: Does it enhance or reduce thenutritional value of plant foods? J. Sci. FoodAgr. 81:924-931.

DeEll, J.R. and R.K. Prange. 1992. Postharvestquality and sensory attributes of organicallyand conventionally grown apples. HortScience27:1096-1099.

Federal Register. 2005. Docket no. TM-04-07.National Organic Program, Sunset Review.116[701, 35177-35182. 1917.

Federal Register. 2006. Docket no. TM504-OIFR.National Organic Program. Amendments to thenational list of allowed and prohibited substan-ces (crops and processing). 175[71], 53299-53303. 9-11-2006.

Lester, G. 2006. Organic versus conventionallygrown produce: Quality differences, and guide-lines for comparison studies. HortScience41:296-300.

Lester, G.E., J. Manthey, and B.S. Buslig. 2007.Organic vs. conventionally grown 'Rio Red'grapefruit: Comparison of production inputs,market quality, consumer acceptance, andhuman health-bioactive compounds. J. Agr.Food Chem. 55:4474-4480.

Magkos, F., F. Arvaniti, and A. Zampelas. 2003.Organic food: Nutritious food or food forthought? A review of the evidence. Intl. J. FoodSci. Nutr. 54:357-371.

Mukherjee, A., D. Speh, E. Dyck, and F. Diez-Gonzalez. 2004. Preharvest evaluation of coli-forms, Escherichia co/i, Salmonella, andEscherichia co/i 0157:H7 in organic and con-ventional produce grown by Minnesota farm-ers. J. Food Prot. 67:894-900.

Mukherjee, A., D. Speh, A.T. Jones, K.M. Buesing,and F. Diez-Gonzalez. 2006. Longitudinalmicrobiological survey of fresh produce grownby farmers in the upper Midwest. J. Food Prot.69:1928-1936.

Plotto, A. and J.A. Narciso. 2006. Guidelines andacceptable postharvest practices for organicallygrown produce. HortScience 41:287-291.

Suslow, T. 2000. Postharvest handling for organiccrops. Univ. California. PubI. 7254:1-8, Univ.California, Oakland, CA.

Taiz, L. and E. Zeiger. 1998. Plant physiology, p.347-376. 2nd ed. Sinauer Associates, Sunder-land, MA.

Woese, K., D. Lange, C. Boess, and W. Bdgl. 1997.A comparison of organically and conventionallygrown foods: Results of a review of the relevantliterature. J. Sci. Food Agr. 74:281 293.

Worthington, V. 2001. Nutritional quality of organicversus conventional fruits, vegetables and grains.3. Alt. Complementary Med. 7:161-173.

Zhao, X., E.E. Carey, W. Want, and C.B. Raja-shekar. 2006. Does organic production enhancephytochemical content of fruit and vegetables?Current knowledge and prospects for research.HortTechnology 16:449-456.

Table 3. Factors in production systems of conventional and organic 'Rio Red' grapefruit orchards.Production System

Factor Organic ConventionalContinuous cropping (y) 14 18Previous crop Grapefruit CitrusIrrigation source Rio Grande River Rio Grande RiverFertilizer Compost N-P-K, S

FishilizerTrace minerals

Soil (0-120 cm) Clay loam to silty clay; Silty clay loam, clay loam;pH, 6.9 to 7.7 pH, 7.2 to 8.0

Weed control Cultivation Active PlusDirexSemazine

Insect control Compost tea Agrimek

Flowable S Citrus oilEnableLorsbanVendexR-56

Table 4. Statistically significant differences in 'Rio Red' grapefruit produced conventionally or organically(averaged for commercial early-, mid-, and late-season harvests) (Lester et al., 2007).

Significance (organic relative to conventional)Factor External (peel) Internal (juice)Fruit weight LowerSpecific gravity Higher HigherPeel thickness LowerColor

Lightness Higher HigherChroma Lower LowerHue Higher (more green) Higher (more green)

Total N, NO 3- LowerJuice yield (%) HigherAscorbic acid HigherLycopene LowerTitratable acidity - HigherpH LowerTotal sugars - HigherSoluble solids content - HigherConsumer preference

Tartness - More tartSweetness - Less sweetOverall Less liked

Phenol contentFlavonoid (Naringin) - HigherFuranocoumarins LowerBergaptol Higher

compound content and bioavailability, andconsumer acceptance (sensory quality), all ofwhich are areas of potentially critical scien-tific study.

Literature Cited

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