PACKINGHOUSE NEWSLETTER

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1 Cooprativ Extnsion Srvic Institut of Food and Agricultural Scincs PACKINGHOUSE NEWSLETTER Mark Ritnour Packinghous Nwslttr No. 192 Indian Rivr REC Dcmbr 29, South Rock Road Ft. Pirc, FL Phon: (561) FAX: (561) Ky Indx Words: Quatrnary Ammonia, Pl Injury, Chlorination, Rcirculatd Watr Elctronic Availability of th Packinghous Nwslttr Mark Ritnour, Indian Rivr REC, Ft. Pirc All prvious and prsnt Packinghous Nwslttrs (PHNL) ar now availabl on th Intrnt at th Univrsity of Florida s postharvst wb sit ( and can also b accssd through our citrus rsourcs wb sit ( Thos of you who signd up to rciv th PHNL via -mail should hav alrady rcivd a copy lctronically. Plas contact m if you wish to sign up for lctronic dlivry or if you signd up but did not rciv your lctronic copy. Printd copis will continu to b maild out to all rcipints whil w complt th transition. Quatrnary Ammonia Injury on Grapfruit Pl Mark Ritnour, Indian Rivr REC, Ft. Pirc Tofilo Ng-Sanchz, FMC FoodTch, Ft. Pirc D. Frank Klsy, FMC FoodTch, Lakland This sason, thr hav bn occasional rports of quatrnary ammonia injury on citrus pl. Though apparntly not a widsprad problm, with incrasd us of quatrnary ammonia to sanitiz quipmnt and bins for cankr control, th potntial for injury to citrus fruit has also incrasd. Prvious xprimnts provid th following conclusions: 1) Dirct contact with 100 to 2000 parts pr million (ppm) quatrnary ammonia solutions will injur citrus pl if allowd to rmain on fruit surfacs. 2) Rsidus of 2000 ppm quatrnary ammonia solution on plastic surfacs touching fruit can injur citrus pl if r-dissolvd by watr on wt fruit or from condnsation.

2 Packinghous Nwslttr No Dcmbr, ) Quatrnary ammonia injury can dvlop within 24 to 36 hours with symptoms ranging from vry slight discoloration to svr, dark brown to black pl (Fig. 1). 4) Similar rsults wr obtaind whn using any of thr diffrnt quatrnary ammonia products at 2000 ppm. Discoloration (2) Slight Ncrosis (3) Modrat Injury (4) Svr Injury (5) Figur 1. Quatrnary ammonia injury on Marsh grapfruit. Numbrs in parnthss indicats rlation to th injury rating scal usd (1 = no injury; 5 = svr injury). Quatrnary ammonia is not approvd for dirct fruit contact. Th top manifolds of grov cankr spray stations should b turnd off whn trucks xit grovs so that only th truck undrcarriag, and not th fruit, rcivs th sanitizing tratmnt. In th packinghous, th Florida Dpartmnt of Agricultur and Consumr Srvics prmits bins to b rinsd with frsh watr shortly aftr quatrnary ammonia applications to rduc th potntial for this injury. Som packinghouss ar now sanitizing bins with 200 ppm chlorin instad of quatrnary ammonia to rduc quatrnary ammonia rsidus on bins. Bcaus rins stations may not rmov all th quatrnary ammonia rsidu (rsidus of 200 to 400 ppm hav bn masurd aftr th rins), an xprimnt was conductd to assss fruit injury from quatrnary ammonia rsidus on bins and fruit xpctd undr commrcial conditions. Exprimntal Dsign Quatrnary ammonia solutions of 0 (watr alon), 100, 300, 500, 1000, and 2000 ppm wr prpard from a commrcial quatrnary ammonia product (21.7 % quatrnary ammonia + surfactant). Eithr Marsh whit grapfruit or plastic ptri plats wr dippd in on of th abov quatrnary ammonia solutions and th solutions wr allowd to drip from both for 5 sconds. Th dippd fruit wr thn placd on clan, dry ptri plats or untratd, dry fruit wr placd on th wt rsidu rmaining on th dippd ptri plats. An additional tratmnt usd a dippd ptri plat whr th rmaining 2000 ppm quatrnary ammonia solution was drid with a forcd-air dryr bfor placing

3 Packinghous Nwslttr No Dcmbr, 2000 th dry, untratd fruit on th plat. Pl injury was valuatd on a scal of 1 (no injury) to 5 (svr injury; Fig. 1) aftr fiv days of storag at 85 o F (29.5 o C) with 95% RH (to simulat dgrning conditions). Exprimnts wr conductd using a compltly random dsign with 10 rplicats (fruit) pr tratmnt. Rsults Whn ithr ptri plats or fruit wr dippd in quatrnary ammonia solutions, no significant injury was dtctd until quatrnary ammonia concntration ros abov 300 ppm (Fig. 2). On plats dippd in concntrations btwn 500 and 2000 ppm, ach succssiv incras in quatrnary ammonia concntration rsultd in significantly mor pl injury. Fruit dippd in quatrnary ammonia solutions of 500 or 1000 ppm dvlopd slight ncrotic lsions whil fruit dippd in 2000 ppm solutions dvlopd significantly mor injury. Fruit did not dvlop injury if placd in ptri plats that wr drid aftr dipping in th 2000 ppm quatrnary ammonia solution. Quatrnary Ammonia Injury d bc a Watr Watr Dry 2000 Dippd Plat Dippd Fruit Tratmnts Figur 2. Pl injury on Marsh whit grapfruit that wr dippd in quatrnary ammonia solutions or placd on plastic ptri plats dippd in quatrnary ammonia solutions. Quatrnary ammonia concntrations ar indicatd as 100, 300, 500, 1000, and 2000 ppm. For th dry tratmnt, rmaining quatrnary ammonia solution on dippd ptri plats was drid bfor fruit wr placd on th plat. Bars associatd with diffrnt lttrs ar significantly diffrnt by Duncan's multipl rang tst at p<0.05. cd cd b

4 Packinghous Nwslttr No Dcmbr, 2000 Conclusions!" Quatrnary ammonia injury to citrus has occasionally bn obsrvd this sason but currntly dos not appar to b a widsprad problm.!" To rduc potntial injury from quatrnary ammonia rsidus, rins bins with frsh watr aftr quatrnary ammonia tratmnts in th packinghous. Altrnativly, sanitiz bins with 200 ppm chlorin (ph btwn 6 and 7.5) instad of using quatrnary ammonia.!" Contact with quatrnary ammonia solutions of 500 ppm or gratr or thir r-dissolvd rsidu can rsult in blmishs on grapfruit pl. Most bin rins oprations rduc rsidual quatrnary ammonia concntrations to blow this lvl.!" Assur that th top manifolds of grov cankr spray stations ar turnd off whn trucks hauling fruit xit grovs so that only th truck undrcarriag, and not th fruit, rcivs th sanitizing tratmnt. Application dirctly to th fruit can rsult in svr damag.!" Contact of dry fruit with dry quatrnary ammonia rsidu dos not normally rsult in pl injury. Chlorin Us In Citrus Packinghouss Mark A. Ritnour, Indian Rivr REC, Ft. Pirc Stvn A. Sargnt, Horticultural Scincs Dpartmnt, Univrsity of Florida, Gainsvill Jrry A. Bartz, Plant Pathology Dpartmnt, Univrsity of Florida, Gainsvill Introduction Many postharvst dcay problms rsult from th inffctiv sanitizing of packinghous dump tanks and flums. Evn halthy looking products from th fild can harbor larg populations of pathogns, particularly during warm, rainy wathr. Pathogns prsnt on frshly harvstd citrus accumulat in rcirculatd watr handling systms. Whn citrus coms in contact with watr containing pathogns, fruit oftn bcom infctd and subsquntly dcay during shipping and handling. Although many packrs routinly add chlorin to thir watr handling systms, failur to follow th IFAS guidlins for packinghous watr sanitation may gratly rduc th ffctivnss of this tratmnt in rducing postharvst dcay. For citrus, IFAS rcommnds maintaining a minimum concntration of 75 parts pr million (ppm) of fr chlorin and ph btwn 6.5 and 7.5. Rcnt studis suggst that gratr than 100 ppm chlorin is ndd to ffctivly kill som pathogns in dump tanks. Thr is a good possibility that dcay problms will aris during handling and shipping whnvr product contacts rcirculatd watr that is not maintaind undr ths conditions. In this articl, w outlin principls for ffctivly using chlorin for watr sanitation. Forms Of Chlorin Th main forms of chlorin usd in packinghouss ar sodium hypochlorit (NaOCl), calcium hypochlorit (Ca(OCl) 2 ) and chlorin gas (Cl 2 ). Sodium hypochlorit is typically sold as 12

5 Packinghous Nwslttr No Dcmbr, 2000 to 15 % solutions. Calcium hypochlorit usually is sold as a powdr or tablts in formulations of 65%. Howvr, it dos not dissolv radily (spcially in cold watr) and undissolvd particls can injur fruits and vgtabls. To prvnt this, dissolv th powdr or granuls in a small amount of warm watr bfor adding it to th tank. If using tablts for continuous, slow rlas of chlorin, nsur that th tablts ar placd whr watr circulats wll around thm. Chlorin gas coms in prssurizd gas cylindrs and should b handld with caution according to labl instructions. Factors Influncing Chlorin Activity Watr ph: Whn sodium hypochlorit is addd to watr, it forms sodium hydroxid (NaOH) and hypochlorous acid (HOCl). All thr forms of chlorin produc hypochlorous acid (also calld availabl chlorin or activ chlorin). Hypochlorous acid is what kills pathogns. In high ph solutions, most of th hypochlorous acid disassociats to form hypochlorit ion (OCl-) which is not an ffctiv sanitizr. Tsting kits for fr chlorin masur both hypochlorous acid and hypochlorit ion and alon do not indicat th quantity of availabl chlorin that kills pathogns. Chlorin solutions with ph abov 8 ar rlativly inffctiv against pathogns. Blow ph 6, chlorin is mor corrosiv to quipmnt and activity is rapidly lost. A ph of around 7 will maintain about 80% of th chlorin in th availabl (hypochlorous acid) form with vry littl gas formd (s insrt). Thus, in ordr to know th sanitizing strngth of on s chlorin solution, both ph and fr chlorin must b masurd. % Chlorin in Availabl Form OC (32F) 20C (68F) 30C (86F) Both watr sourc and form of SOLUTION ph chlorin usd will affct ph managmnt. Frsh watr in Florida may hav a ph abov 8.0 du to dissolvd calcium carbonat. Adding ithr sodium hypochlorit or calcium hypochlorit will incras ph, whil adding chlorin gas will dcras ph. Aftr adding commrcial chlorin, adjust th ph of th watr to 7 by adding ithr acid or bas. Muriatic (HCl) or citric acid ar commonly usd to lowr ph whil sodium hydroxid (ly) will rais ph. Th ph of watr can b dtrmind by using an lctronic ph mtr or color-changing papr indicator. Chlorin concntration: Although low concntrations of hypochlorous acid (< 40 ppm) hav bn rportd to kill most pathogns within 1 minut, highr concntrations ( ppm) ar commonly usd to compnsat for various losss of availabl chlorin in th tank. Exposur tim: High availabl chlorin concntrations kill pathogns aftr short xposur tims (< 1 min.). At lowr concntrations, mor contact tim is rquird to kill th pathogns.

6 Packinghous Nwslttr No Dcmbr, 2000 Amount of organic mattr in th watr (.g. fruit, lavs and soil): Organic mattr in th watr will inactivat hypochlorous acid and can quickly rduc th amount of availabl chlorin. Chlorin which combins with organic mattr is no longr activ against pathogns but may still b masurd by total chlorin tsting kits. Watr tmpratur: At highr tmpraturs, hypochlorous acid kills pathogns mor quickly but is also lost mor rapidly du to ractions with organic mattr. Typ and growth stag of th pathogns: Although grminating spors and myclium ar rlativly asy to kill, spors ar much mor rsistant to chlorin, and pathogns growing insid citrus tissu (insid wounds or as quiscnt infctions) ar shildd from th chlorin and not killd. Maintaining Adquat Chlorin Concntrations Chlorin must b continuously addd to th watr to rplac chlorin lost to ractions with organic mattr, chmicals, microorganisms, and th surfacs of citrus fruits. Thr ar svral ways to maintain adquat chlorin concntrations. Equipmnt is availabl to automatically masur fr chlorin concntrations and to add chlorin to th watr whn ndd. Morovr, crtain typs of systms also automatically maintain th propr ph rang. Automatd dispnsing of chlorin products rquirs frqunt masurmnt of th chlorin concntration to vrify propr opration. Managrs must b vigilant with systms dsignd to dispns chlorin at a uniform rat bcaus th chlorin dmand can chang abruptly du to factors such as th amount of sooty mold prsnt. Manual addition of chlorin products can b usd if th managr is dilignt in masuring and adjusting chlorin concntrations and ph. Sampls should b takn on an hourly basis. Chlorin Tst Kits Mak crtain th tst kit masurs fr chlorin (not total) and b familiar with th concntration limits of th kit. Swimming pool-typ kits usually masur in th rang of 1 to 5 ppm fr chlorin. Ths kits can provid accurat masurmnts if watr sampls ar dilutd to th rang of th kit bfor tsting. Distilld watr should b usd to dilut th sampl for accurat dtrmination of fr chlorin. Diluting th sampl with sulfur watr or watr containing organic mattr or othr chmicals will intrfr with accurat masurmnt of fr chlorin. Rcommndations 1. Maintain a minimum concntration of 75 parts pr million (ppm) of fr chlorin. 2. Maintain ph btwn 6.5 and Chck fr chlorin and ph lvls frquntly. Automatd systms to monitor and adjust fr chlorin and ph lvls may b ffctiv, but rquir rgular calibration and maintnanc. 4. Drain th tank at th nd of ach day and rfill with clan watr. 5. Us all chmicals according to thir labl instructions (.g. chlorin, muriatic acid, ly, tc.). 6. Us slf-claning scrns in dump tanks to rmov larg dbris. 7. Consult local rgulations for disposal of chlorinatd watr.

7 Packinghous Nwslttr No Dcmbr, 2000 Dsird ppm of Fr Chlorin MIXING CHLORINE SOLUTIONS Pints of 5.25% NaOCl solution pr 100 gal. of watr Pints of 12.75% NaOCl solution pr 100 gal. of watr Ouncs of 65% Ca(OCl) 2 pr 100 gal. of watr To prpar a spcific fr chlorin solution (ppm) using sodium hypochlorit (NaOCl), us th following formula. 1) Dtrmin amount of sodium hypochlorit (NaOCl) concntrat to b addd to th total volum of watr (units for NaOCl concntrat to add and total volum must b th sam): Volum of NaOCl to add = Dsird ppm of fr chlorin X total volum in tank (% NaOCl in concntrat) X 10,000 2) Add calculatd amount of NaOCl concntrat to tank and bring up to final volum with watr. Exampl To achiv a 150 ppm fr chlorin concntration in a 1,000 gallon dump tank using a 12.75% sodium hypochlorit solution. 1) NaOCl concntrat to add (gallons) = 150 ppm X 1,000 gallons = 1.18 gallons. (12.75 X 10,000) ppm 2) Add 1.18 gallons of 12.75% sodium hypochlorit to gallons of watr. Adjust ph to btwn 6.5 & 7.5.