South Africn Avocdo Growers' Assocition Yerbook. 2003. 26:55-64 Semi-commercil evlution of SmrtFresh with South Africn export vocdos in sttic continers t the Westfli pckhouse during 2002 D Lemmer #, J Bezuidenhout*, S Sekhune*, P Rmokone*, L Letsolo*, T R Mlumne #, P Chibi #, Y Nxundu #, M Hobson + nd F J Kruger # # ARC-ITSC, Privte Bg X11208, Nelspruit 1200, South Afric + ARC-ITSC Merensky experimentl frm *Westfli Esttes, PO Box 14, Duiwelskloof 0835, South Afric E-mil: dnie@itsc.gric.z (or) frns@itsc.gric.z ABSTRACT During the 2000 nd 2001 sesons, intensive lbortory testing ws done with 1-methyl cyclopropene (1-MCP), n ethylene blocker on vocdo fruit. All the mjor South Africn cultivrs were tested nd spects such s storge potentil, respirtion rte nd fruit qulity upon ripening were covered. The results were extremely positive nd the mnufcturer (Rohm & Hs, USA) hs subsequently registered the product in South Afric. During 2002, tblet formultion of 1-MCP, SmrtFresh TM, ws tested under semi-commercil conditions on Fuerte nd Hss t the Westfli pckhouse in Tzneen. The product ws pplied in sttic reefer continer. SmrtFresh TM ws found to effectively inhibit the ripening process of Hss nd Fuerte under the semi-commercil conditions described bove. The inhibition of ripening ws more intense in Fuerte thn in Hss. Furthermore, the inhibition of ripening ws more intense in the smller count 18 fruit thn in the bigger count 10-12 fruit. The increse in storge life ws found to be comprble to tht ttined with control tmosphere storge (CA) when SmrtFresh TM ws pplied t the optimum dosge. The most pproprite pckhouse bsed dosge regime for ll sized fruit ws determined nd commercil ppliction commenced during 2003. INTRODUCTION In the pst the firmness of export vocdos ws mintined by reducing the storge temperture during trnsport. However, temperture control lone will not prevent ripening during 28 dy export period, especilly during the lte seson. Since 1996, controlled tmosphere (CA) becme vilble in South Afric s n dditionl tool to reduce ripening during storge. Due to the success of this method, virtully ll vocdos re currently exported under CA. This method certinly improved the chnces of lnding hrd fruit in Europe nd extended the hrvesting window. Cold storge nd CA both dely the ripening process by slowing down the metbolism of the fruit. During the 2000 2001 sesons, the ARC- ITSC hs been evluting the effectiveness of SmrtFresh TM, product contining n ethyl- Yerbook 03 55 Jrboek 03
ene inhibitor, 1-methyl cyclopropene (1-MCP), on vocdos (Lemmer et l., 2002). The trils were done in the lbortory using ll the mjor export cultivrs nd covered spects such s storge potentil, respirtion rte nd fruit qulity upon ripening. The min conclusions drwn from the initil lbortory bsed trils were: SmrtFresh TM slows down the ripening process of vocdo under export simultion conditions. The ripening retrding effect is more intense on slow metbolizing CV s such s Ryn compred to CV s with fster metbolism such s Hss. SmrtFresh TM cn be pplied over wide rnge of concentrtions nd dosge effect exists. SmrtFresh TM cn be pplied t the temperture the fruit re to be exported t. Storge potentil of SmrtFresh TM treted fruit is comprble to CA fruit. SmrtFresh TM suppresses respirtion rte to greter extent thn CA. SmrtFresh TM reduces grey pulp under lbortory conditions. The storge period is not to be over extended s this my increse the incidence of fungl pthology. Due to the extremely positive results, the mnufcturer (Rohm & Hs, USA) hs registered the product on vocdos in South Afric. During 2002, tblet formultion, SmrtFresh TM, ws tested under semi-commercil conditions on Fuerte nd Hss t the Westfli pckhouse in Tzneen. The product ws pplied under pckhouse conditions in sttic reefer continer. The reserch imed to determine suitble ppliction periods nd optimum dosge regimes for Fuerte nd Hss vocdo fruit. MATERIAL AND METHODS Fruit In the cse of Fuerte count 18 (211 235 g ) nd count 10 (366 450 g) fruit were used. In the cse of Hss count 18 nd count 12 (306 365 g) fruit were used. Freshly hrvested nd pcked export fruit were smpled for the trils. Tretments Tking the previous results into considertion, it ws decided to include two SmrtFresh TM concentrtions (300 ppb nd 500 ppb) nd to tret the fruit for 16 hours. On pckhouse mngement request, n 8 hour regime ws lso included in one of the trils. In ll cses, the SmrtFresh TM treted fruit were compred with untreted control fruit from the sme btch. Smrtfresh TM treted fruit were lso compred with CA stored fruit (CO 2 = 6% nd O 2 = 4%). A flow-through CA system (consisting of 100 L drum connected to gs regultors nd CA control bord) ws instlled in Westfli cold room for this purpose. Tretment ppliction nd storge Two 58m 3 reefer shipping continers were prked t Westfli pckhouse for the durtion of the 2002 seson. One continer ws ir-tightened nd used for treting the fruit while the second ws used for cool storge. A totl number of 11 continer lods were treted during the seson. Fuerte fruit were treted on 18 April, 25 April, 5 June, 23 July, 24 July, 31 July, 2 August. Hss fruit were treted on 5 June, 23 July, 24 July, 2 August, 26 August, 27 August, 28 August, 29 August nd 30 August. During the first two trils, export fruit smples (3 boxes per size) were plced in the center of 20 pllets. The rest of the pllets consisted of locl mrket fruit. The im of the experiment ws to estblish whether the 1-MCP gs diffused evenly through the continer from the point of relese t the door. After the ppliction period of 16 hours, the doors nd the vents were opened. The pllets were removed nd 10 of the pllets were replced with pllets contining control untreted smples. The pllets were plced in the sme order, from the con- Jrboek 03 56 Yerbook 03
denser side towrds the door of the continer. The fruit were stored inside the continer with the vents 15% open to simulte the export period to Europe. After 28 dys storge period t the SAAGA prescribed temperture regime, the fruit were ripened t 18 o C nd evluted. During the remining 9 trils, the tretment continer ws filled with bulk bins contining locl mrket fruit. Two sets of export fruit smples (three boxes of ech count) were plced ner the condenser nd door, on top of the bulk bins. After tretment, the smple fruit were removed from the pllets nd stored in the second empty continer. Evlution criteri Individul fruit were comprehensively evluted s they ripened. This ws done by the ppliction of moderte finger pressure to the fruit on dily bsis. Densimeter redings were lso tken upon evlution to ensure tht the fruit were cut within similr firmness rnges. Fruit ripening ws expressed s the men number of dys until the fruit ripened nd longitudinl ripening profile ws composed. The following criteri were included when evluting the fruit upon ripening: No. of dys to ripen Bruising Blck cold dmge Lenticel dmge Dusky browning Grey pulp Pulpspot Vsculr browning Anthrcnose Stem-end rot. The physiologicl nd pthologicl disorders were scored on scle of 1 3 where 1 depicted mild nd 3 severe disorder. RESULTS AND DISCUSSION Figure 1 is representtion of the effect tht SmrtFresh TM hs on the externl colour of Hss fruit. This photogrph ws tken upon Figure 1. SmrtFresh TM slows down the degreening of Hss fruit during cold storge. This photogrph ws tken directly fter storge, during one of the trils where logisticl problems cused the control fruit to ripen premturely. removl from 28 dy cold storge period in one of the experiments during which certin logisticl problems were encountered. The control fruit hs strted turning blck during storge, while the SmrtFresh TM treted fruit remined green. This visully exemplifies the ripening inhibition properties of SmrtFresh TM. Figure 2. Men number of dys required to ripen count 18 Fuerte fruit treted nd stored in different pllet positions within the continer. The fruit were treted on 25 April with 300 ppb SmrtFresh TM for 16 hours before being stored with untreted smples for 28 dys t 7 o C. Brs mrked with the sme symbol re not significntly different (Student t-test, P>0.05). Figure 2 demonstrtes the effect of pllet position within the continer during the ppliction nd storge period on the ripening of Fuerte count 18 fruit. Pllet position did not mke difference. This indictes tht Smrtfresh TM diffused effectively through the continer. Yerbook 03 57 Jrboek 03
Figure 3. Men number of dys tken to ripen counts 10 nd 18 Fuerte fruit t 18 o C. The fruit were treted on the listed dtes inside 58 m 3 refrigerted se freight continer with either 300 or 500 ppb SmrtFresh TM for 16 hours, before being stored with untreted smples for 28 dys t the indicted export tempertures used t the time. Brs mrked with the sme symbol re not significntly different. The sttistics pply seprtely for ech tretment dte nd fruit count (Student t-test, P>0.05). Figure 4. Men number of dys tken to ripen counts 12 nd 18 Hss fruit t 18 o C. The fruit were treted on the listed dtes inside 58 m 3 refrigerted se freight continer with either 300 or 500 ppb SmrtFresh TM for 16 hours, before being stored with untreted smples for 28 dys t the indicted export tempertures used t the time. Brs mrked with the sme symbol re not significntly different. The sttistics pply seprtely for ech tretment dte nd fruit count (Student t-test, P>0.05). The number of dys required to ripen Fuerte fruit during the vrious trils, is displyed in Figure 3. Tretment with SmrtFresh TM led to significnt increse in the verge number of dys to ripen, throughout the seson. This ws true for the count 18 nd count 10 fruit. However, the inhibition of ripening ws more pronounced in the smller count 18 fruit thn in the bigger count 10 fruit. When compring the 300 ppb nd 500 ppb tretments, it is cler tht the higher concentrtion of Smrtfresh TM more drsticlly inhibited ripening thn the lower concentrtion. Nevertheless, the effect ttined with the 300 ppb tretment ws still stisfctory. During the tretment crried out on 25 April, the pckhouse cpcity ws overloded. Due to insufficient storge spce, the tretment pllets were stored in side hlls of the loding zones, with no temperture control. Furthermore, only one forklift ws vilble which hd to be shred with the pckhouse nd oil-fctory. For this reson, the plletelised fruit stood outside in the sun for severl hours. Regrdless of these sub-optiml conditions, the 300 ppb tretment ws still ble to retin storge potentil. This is very promising observtion, indicting tht SmrtFresh TM will hve buffering effect ginst temperture relted hick-ups in the cold chin. The number of dys until ripe recorded for Hss fruit is shown in Figure 4. A trend similr to Fuerte ws observed. However, the Hss fruit, especilly the bigger count 12 fruit, rected less fvourbly thn Fuerte to the SmrtFresh TM tretment. This might be contributed to the higher metblic rte of Hss fruit. The gen- Jrboek 03 58 Yerbook 03
% Fruit with Grey pulp % Fruit with Grey pulp 50 40 30 20 10 0 50 40 30 20 10 0 X 5Jun b 23 Jul Dte of tretment Figure 5. Percentge counts 10 nd 18 Fuerte fruit with grey pulp s recorded when the fruit ripened. The fruit were treted on the listed dtes inside 58 m 3 refrigerted se freight continer with either 300 or 500 ppb SmrtFresh TM for 16 hours, before being stored with untreted smples for 28 dys t the SAAGA export tempertures used t the time. Brs mrked with the sme symbol re not significntly different. The sttistics pply seprtely for ech tretment dte nd fruit count (χ 2 -test, P<0.95). 100 80 60 40 20 0 100 80 60 40 20 0 Control 300ppb SmrtFresh TM 500ppb SmrtFresh TM 18 Apr 5Jun 25 Apr Control 300ppb SmrtFresh TM 500ppb SmrtFresh TM Figure 6. Percentge counts 12 nd 18 Hss fruit with grey pulp s recorded when the fruit ripened. The fruit were treted on the listed dtes inside 58 m 3 refrigerted se freight continer with either 300 or 500 ppb SmrtFresh TM for 16 hours, before being stored with untreted smples for 28 dys t the SAAGA export tempertures used t the time. Brs mrked with the sme symbol re not significntly different. The sttistics pply seprtely for ech tretment dte nd fruit count (χ 2 -test, P<0.95). 24 Jul 23 Jul 24 Jul 31 Jul Dte of tretment 2Aug 31 Jul 28 Aug b b 2Aug 30 Aug Fuerte: Count 18 Count 12 Hss: Count 18 Count 12 erl effect ws nonetheless cceptble nd, s will be shown lter, very similr to tht ttined with CA. The percentge Fuerte fruit with grey pulp is portryed in Figure 5. The untreted fruit showed n incresing prevlence s the seson progressed nd this trend strted erlier nd to greter extend in the bigger count 10 fruit. It is promising to note tht the Smrtfresh TM tretments led to significnt decrese in the grey pulp incidence of, especilly, the count 10 fruit. The reduction ws more prominent nd consistent in the higher dosge tretments (500 ppb) of 24 July nd 2 August. The incidence of grey pulp in Hss fruit is portryed in Figure 6. The prevlence of the disorder ws too low to drw ny conclusions. The incidence of nthrcnose in Fuerte is represented in Figure 7. As the seson progressed, the incidence of the infection incresed. It is therefore promising to note tht only one SmrtFresh TM tretment (count 10; treted on 31 July) showed significntly higher incidence of nthrcnose. We expected the lengthening of the storge period to cuse more nthrcnose infections. A similr trend ws noticed in Hss (Figure 8). Only one Smrt- Fresh TM tretment showed significnt increse in nthrcnose infection (count18; treted on 30 August). This tretment ws done t the higher dosge (500 ppb) nd the ripening period ws considerbly longer in this specific cse. The intensity of the infection ws lso influenced. With the control, ll 16% of infected fruit scored 1. With the SmrtFresh TM tretment, 16% of the fruit obtined rting of 1, while Yerbook 03 59 Jrboek 03
Figure 7. Percentge counts 10 nd 18 Fuerte fruit with nthrcnose, s recorded when the fruit ripened. The fruit were treted on the listed dtes inside 58 m 3 refrigerted se freight continer with either 300 or 500 ppb SmrtFresh TM for 16 hours, before being stored with untreted smples for 28 dys t the SAAGA export tempertures used t the time. Brs mrked with the sme symbol re not significntly different. The sttistics pply seprtely for ech tretment dte nd fruit count (χ 2 -test, P<0.95). Figure 8. Percentge counts 12 nd 18 Hss fruit with nthrcnose, s recorded when the fruit ripened. The fruit were treted on the listed dtes inside 58 m 3 refrigerted se freight continer with either 300 or 500 ppb SmrtFresh TM for 16 hours, before being stored with untreted smples for 28 dys t the SAAGA export tempertures used t the time. Brs mrked with the sme symbol re not significntly different. The sttistics pply seprtely for ech tretment dte nd fruit count (χ 2 -test, P<0.95). 7.4% scored 2 nd 3.7% scored 3. Cre must therefore be tken not to over extend the shelflife by using too high dosge. This ws lso noticed in the lbortory trils conducted during the previous 2 sesons (Lemmer et l., 2002). The percentge of Fuerte fruit with stem-end rot is displyed in Figure 9. The control fruit did not show significnt increse in infection towrds the end of the seson. However, the Smrtfresh TM tretments did. This increse ws erlier nd more prominent in the count 10 fruit nd ws gin cused by the lengthening of the storge period. With Hss, the erly seson Smrt- Fresh TM tretment conducted on 5 June, led to significnt increse in stem-end rot (Figure 10). In this regrd it must be mentioned tht it is common to find high incidence of stem-end rot infection t the beginning of the hrvest window, when the fruit re still reltively immture. This is excerbted by further lengthening of the storge period. However, the severity of the infection ws not influenced. The highest incidence of in stemend rot in Hss ws recorded during the lte seson (2 nd 30 August) in count 12 fruit. These tretments were both done t the higher 500 ppb regime nd t first glnce my be scribed to the lengthening of the storge period. However, these two trils lso showed the highest incidence of lenticel dmge (Figure 11) nd bruising (Figure 12). The pre-hrvest qulity of the fruit ws obviously poor. In Tble 1, SmrtFresh TM is compred with CA. Both methods inhibited ripening to similr degree in count 12 Hss fruit during both the erly (Tble 1) nd the lte (Tble 1b) seson. During the erly seson, no Jrboek 03 60 Yerbook 03
Figure 9. Percentge counts 10 nd 18 Fuerte fruit with stem-end rot, s recorded when the fruit ripened. The fruit were treted on the listed dtes inside 58 m 3 refrigerted se freight continer with either 300 or 500 ppb SmrtFresh TM for 16 hours, before being stored with untreted smples for 28 dys t the SAAGA export tempertures used t the time. Brs mrked with the sme symbol re not significntly different. The sttistics pply seprtely for ech tretment dte nd count fruit (χ 2 -test, P<0.95). Figure 10. Percentge counts 12 nd 18 Hss fruit with stem-end rot, s recorded when the fruit ripened. The fruit were treted on the listed dtes inside 58 m 3 refrigerted se freight continer with either 300 or 500 ppb SmrtFresh TM for 16 hours, before being stored with untreted smples for 28 dys t the SAAGA export tempertures used t the time. Brs mrked with the sme symbol re not significntly different. The sttistics pply seprtely for ech tretment dte nd count fruit (χ 2 -test, P<0.95). nthrcnose occurred in ny of the tretments. However, during the lte seson both Smrtfresh TM nd CA cused significnt increses in the incidence of nthrcnose infection. Both tretments lso cused n increse in the incidence of stem-endrot during the erly seson. Although the interprettion of the lte seson dt ws confounded by discrepncies between the cold room nd continer dt, similr trend seemed to exist. As mentioned repetedly, the observed increse in pthologicl disorders cn be contributed to the lengthening of the shelf-life period. This gives the infections more time to develop under fvourble conditions. In Figure 13, the 8 hour exposure period is compred to the 16 hour tretment period. Three Smrt- Fresh TM dosge regimes were used, nmely 300 ppb, 400 ppb nd 500 ppb. From the grph it is cler tht the 8 hour regime ws less effective thn the 16 hour regime. In cse of count 12 fruit, no significnt increse ws obtined t both the 300 ppb nd 400 ppb concentrtions when treted for 8 hours. Only the 500 ppb tretment gve significnt increse in shelf life when treted for 8 hours. In cse of the smller count 18 fruit, both the 400 ppb nd 500 ppb tretments were effective when pplied for 8 hours. The bove results infer tht different concentrtions of SmrtFfresh TM is required for smll nd lrge fruit, when treting the fruit for 8 hours. However, the reltively smll volumes of count 10 12 fruit pcked mkes this imprcticl. Furthermore, the incresed dosge needed for the 8 hour regime will hve unnecessry cost implictions. As the 300 ppb/16 hour ws effective for both cultivrs s well s for Yerbook 03 61 Jrboek 03
smll nd lrge counts, this is obviously the better recommendtion. Figure 11. The percentge counts 12 nd 18 Hss with lenticel dmge, s recorded upon removl from cold storge. The fruit were treted on the listed dtes inside 58 m 3 refrigerted se freight continer with either 300 or 500 ppb SmrtFresh TM for 16 hours, before being stored with untreted smples for 28 dys t the SAAGA export tempertures used t the time. Brs mrked with the sme symbol re not significntly different. The sttistics pply seprtely for ech tretment dte nd count fruit (χ 2 -test, P<0.95). Figure 12. Percentge bruised counts 10 nd 18 Hss fruit, s recorded when the fruit ripened. The fruit were treted on the listed dtes inside 58 m 3 refrigerted se freight continer with either 300 or 500 ppb SmrtFresh TM for 16 hours, before being stored with untreted smples for 28 dys t the SAAGA export tempertures used t the time. Brs mrked with the sme symbol re not significntly different. The sttistics pply seprtely for ech tretment dte nd count fruit (χ 2 -test, P<0.95). Ad Hoc lbortory trils conducted during 2002 In ddition to the semi-commercil trils described bove, two lbortory scled trils were conducted during 2002. The trils were conducted t Westfli Esttes using the equipment nd procedures described by Lemmer et l. (2002). A question often sked is: Will it be possible to tret vocdo fruit in cool truck while in trnsit to Cpe Town hrbour? This implictes longer exposure periods thn the bove 16 hour recommendtion. To nswer this question, the fruit were treted with 300 ppb for respectively 16, 24 or 36 hours. The results re shown in Tble 2. There ws no difference between the tretments in terms of the number of dys to ripen (Tble 2) or fruit qulity (dt not shown). This indictes tht the lengthened tretment period hd no negtive effect. The second experiment imed to determine wht effect dely between pcking nd treting hs on storge potentil of the fruit. To do this, Hss fruit were treted with 300 ppb SmrtFresh TM for 8 hours directly fter hrvest s well s fter 3 nd 7 dys. The results re shown in Tble 3. When pplied 3 dys fter hrvest, the SmrtFresh TM tretment ws s effective s when pplied directly fter hrvest. When pplied 7 dys fter hrvest, the tretment ws slightly less effective nd it led to incresed pthologicl disorders (dt not shown) which is undesirble. Jrboek 03 62 Yerbook 03
Figure 13. Men number of dys tken to ripen counts 12 nd 18 Hss fruit t 18 o C. The fruit were treted inside continer with either 300, 400 or 500 ppb SmrtFresh TM for 8 or 16 hours, before being stored with untreted smples for 28 dys t the recommended export temperture. Brs mrked with the sme symbol re not significntly different. The sttistics pply seprtely for ech tretment dte nd fruit count (Student t-test, P>0.05). SUMMARY AND RECOMMENDA- TIONS Prevention of soft lndings SmrtFresh TM effectively inhibited the ripening process of Hss nd Fuerte under bigger volume semicommercil conditions. The increse in storge life is comprble to CA when Smrtfresh TM is pplied t optimum dosge. The inhibition of ripening is more intense in Fuerte compred to Hss. The inhibition of ripening is more intense in the smller Count 18 fruit compred to bigger Count 10-12 fruit. Physiologicl disorders Smrtfresh TM reduced the incidence of grey pulp during certin trils. The reduction ws greter t the 500 ppb concentrtion thn t the 300 ppb concentrtion. Tble 1. Comprison of the effect of CA nd SmrtFresh TM on count 12 Hss fruit in terms of the number of dys to ripen nd the incidence of pthologicl disorders recorded during the erly () nd lte (b) seson. Yerbook 03 63 Jrboek 03
Tble 2. Number of dys to ripen count 18 Hss fruit treted with 300ppb SmrtFresh TM inside 100l plstic continer for 16, 24 or 36 hours, before being stored with untreted smples for 28 dys t the recommended export tempertures, inside the 58m 3 se freight continer. Vlues mrked with the sme symbol re not significntly different (Student t-test, P>0.05). The reduction ws most noticeble in bigger sized fruit, especilly t the end of the seson when the incidence of grey pulp ws t its highest. Pthologicl disorders In both Smrtfresh TM treted nd CA stored fruit the lengthening in dys to ripen does not influence nthrcnose infection incidence in the erly seson. During the lte seson, incresed nthrcnose infection incidence sometimes occurred in both Smrtfresh TM treted nd CA stored fruit. Lengthening of ripening period sometimes led to n increse incidence of stem-end rot in both CA nd Smrtfresh TM treted fruit. This ws more prominent t the end of the seson. The incresed incidence of pthologicl Tble 3. The effect tht posthrvest dely before the SmrtFresh TM ppliction hs on the number of dys to ripen Hss count 18 fruit. The fruit were treted inside with 300ppb SmrtFresh TM inside 100 l plstic continer for 16 hours, either directly fter hrvest or fter 3 or 7 dy dely, before being stored with untreted smples for 28 dys t the recommended export temperture, inside 58m 3 se freight continer. Vlues mrked with the sme symbol re not significntly different (Student t-test, P>0.05). disorders ssocited with the lengthened shelf life is excerbted by the pre-hrvest qulity of the fruit. Dosge nd tretment period At this stge, it is recommended tht pckhouses pply SmrtFresh TM to Fuerte nd Hss fruit t concentrtion of 300 ppb for period of 16 hours. The Smrtfresh TM is most effective when pplied within 3 dys fter hrvest. LITERATURE CITED LEMMER, D., KRUGER, F.J., MALUMANE, T.R. & NXUDU, Y. 2002. 1-Methyl cyclopropene: n lterntive for controlled tmosphere storge of South Africn export vocdos. Journl of the South Africn Avocdo Growers Assocition, 25: 28-39. Jrboek 03 64 Yerbook 03