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Postharvest Biology and Technology 78 (2013) 48–54

Contents lists available at SciVerse ScienceDirect

Postharvest Biology and Technology

journa l h o me pa g e: www.elsev ier .com/ locate /postharvbio

ffects of repeated 1-methylcyclopropene (1-MCP) treatments on ripeningnd superficial scald of ‘Cortland’ and ‘Delicious’ apples

ingang Lua,b, Jacqueline F. Nocka, Yanping Maa,c, Xinghua Liub, Christopher B. Watkinsa,∗

Department of Horticulture, Cornell University, Ithaca, NY 14853, USACollege of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi 712100, ChinaCollege of Forestry, Northwest A&F University, Yangling, Shaanxi 712100, China

r t i c l e i n f o

rticle history:eceived 20 October 2012ccepted 15 December 2012

eywords:alus×domestica Borkh

thyleneirmnesstoragehysiological disorders

a b s t r a c t

Postharvest 1-MCP can maintain fruit quality and inhibit development of superficial scald, a physiolog-ical storage disorder found in apple fruit, but the extent of the inhibition can vary by cultivar. In thisstudy, we investigated whether multiple applications of 1-MCP, which are now permitted by a labelmodification of the commercial 1-MCP product, SmartFreshTM, might improve scald control. ‘Cortland’and ‘Delicious’ apples were untreated, treated on the day of harvest with the antioxidant inhibitor ofscald, diphenylamine (DPA), or with 1 �L L−1 1-MCP at different intervals after harvest. Treatment times(days) were 1, 4, 7, 1 + 4, 4 + 7, 1 + 4 + 7, 7 + 14, 7 + 28, 7 + 42, and 7 + 84. Internal ethylene concentrations(IECs), flesh firmness, and accumulations of �-farnesene and conjugated trienols (CTols) were measuredat harvest, at the time of treatment, and at intervals during air storage at 0.5 ◦C for up to 36 weeks. Scaldwas completely inhibited by DPA and all 1-MCP treatments in ‘Delicious’. However, effective control ofscald in ‘Cortland’ was obtained with 1-MCP treatments within the first 4 days of harvest, either alone orin combination. Scald control with delayed 1-MCP treatments resulted in poorer scald control that wascomparable to that obtained with DPA. IECs and �-farnesene accumulation were similar in untreated andDPA treated fruit, but inhibited by 1-MCP. However, differences among 1-MCP treatments became moreevident with increasing storage periods. Inhibition of IECs and �-farnesene accumulation was greaterin fruit treated on days 1, 4, 1 + 4, 4 + 7, 1 + 4 + 7, than on day 7 alone. A second application of 1-MCP on

day 14 to fruit treated on day 7 increased inhibition of IECs, �-farnesene and CTol accumulations, butincreasing delays before the second 1-MCP treatment resulted in progressively less inhibition of thesefactors. Similar effects of treatment on IECs, �-farnesene and CTol accumulations were found for bothcultivars, even though no scald was detected in treated ‘Delicious’ apples. The results indicate that initial1-MCP treatments should be applied to faster ripening cultivars such as ‘Cortland’ within a few days of harvest.

. Introduction

1-Methylcyclopropene (1-MCP), an inhibitor of ethylene per-eption, is registered as SmartFreshTM for commercial use on fruitnd vegetables. 1-MCP-based technology has had a major impactspecially on apple industries because of its influence on maintain-ng fruit firmness and other quality attributes during storage andhelf life (Watkins, 2006, 2008). Cultivar, harvest maturity and stor-ge treatments affect the response of apples to 1-MCP, probablyeflecting ethylene production by the fruit at the time of treat-

ent (Watkins, 2008; Watkins and Nock, 2012). Cultivars such as

Delicious’ and ‘Granny Smith’ maintain low ethylene productionnd high flesh firmness over extended storage periods after 1-MCP

∗ Corresponding author.E-mail address: cbw3@cornell.edu (C.B. Watkins).

925-5214/$ – see front matter © 2012 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.postharvbio.2012.12.007

© 2012 Elsevier B.V. All rights reserved.

treatment, whereas others such as ‘Cortland’ and ‘McIntosh’ tendto recover from 1-MCP induced inhibition of ripening during stor-age (Fan et al., 1999; Rupasinghe et al., 2000; Watkins et al., 2000;Zanella, 2003; Moran, 2006; Magazin et al., 2010).

In addition to its effects on fruit ripening, 1-MCP can inhibitthe development of the physiological storage disorder superficialscald (Fan et al., 1999; Rupasinghe et al., 2000; Watkins et al.,2000; Pechous et al., 2005), providing a possible replacement forthe antioxidant diphenylamine (DPA). A key process in the devel-opment of scald is thought to be the oxidation of �-farnesene toform toxic products that result in cell damage (Lurie and Watkins,2012). Inhibition of ethylene production by 1-MCP suppresses theproduction of �-farnesene, whereas DPA acts to prevent oxida-

tion of �-farnesene rather than its production (Arquiza et al., 2005;Isidoro and Almeida, 2006; Jung and Watkins, 2008; Moggia et al.,2010). However, the control of scald by 1-MCP can, like softening,be affected by cultivar (Fan et al., 1999; Rupasinghe et al., 2000;

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atkins et al., 2000), and factors such as exposure time to 1-MCPnd treatment temperature (DeEll et al., 2002). As is the case forPA, increasing time between harvest and treatment can result in

educed effectiveness of 1-MCP on scald control (Jung and Watkins,008; Amarante et al., 2010). Reduced control of scald develop-ent by 1-MCP in both apples and pears appears to be associatedith ethylene production in the fruit at the time of treatment and

renewed ability of the fruit to produce ethylene (Ekman et al.,004; Tsantili et al., 2007; Jung and Watkins, 2008).

Apple storages are typically filled over several days or moreepending on factors, such as storage room size, cooling capac-

ty and daily fruit harvest volumes. The suppliers of SmartFreshTM

rovide recommendations to most apple cultivars for maximumelays of 7 d between harvest and treatment (AgroFresh, 2012).owever, the effect of delays between harvest and applicationf 1-MCP is affected by cultivar, storage type and storage lengthWatkins and Nock, 2005). DeEll et al. (2008) reported that theffective time period to inhibit softening of ‘McIntosh’ apples cane as short as 3 d. Rapid treatment of fruit with 1-MCP after har-est can help maintain quality of fruit even when application ofontrolled atmosphere (CA) storage is delayed (Watkins and Nock,012).

The SmartFreshTM label has been modified in the United Statesnd some other countries to allow multiple 1-MCP treatments. Pre-ious studies examined the effects of multiple 1-MCP treatmentsn quality of apples and pears. Firmness of ‘Delicious’ apples wasaintained by multiple treatments at temperatures of 5 ◦C and

bove, but only small effects of treatment were detected at 0 ◦C,ecause of slower softening overall (Mir et al., 2001; Jayanty et al.,004). In ‘Cortland’ or ‘McIntosh’ apples, a second 1-MCP treatmentid-way (4.5 months) during storage did not affect quality of air

nd CA stored fruit (Delong et al., 2004). Pear fruit recovered morelowly from 1-MCP inhibition of softening if additional treatmentsere made before ripening had been initiated (Ekman et al., 2004).

hese studies were largely of academic interest until recently, buthe change in the SmartFreshTM label opens up commercial oppor-unities to apply 1-MCP while storage rooms are being loaded, oruring storage.

The objective of this study was to investigate the effects ofultiple 1-MCP treatments on ripening and scald development

n ‘Cortland’ and ‘Delicious’ apples during long-term cold storage.ur interest was two-fold: first, to investigate if multiple 1-MCP

reatments that might occur during storage room loading wouldmprove inhibition of ripening and scald, especially for a fast ripen-ng cultivar such as ‘Cortland’, and second, to investigate if repeated-MCP in storage during the time when IEC and �-farnesene con-entrations increase, would improve control of scald developmenturing storage.

. Materials and methods

.1. Plant material, treatment and sampling

‘Cortland’ and ‘Delicious’ apples [Malus×sylvestris (L.) Mill.ar. domestica (Borkh.) Mansf.] were harvested from commercialrchards in Western New York regions on 21 and 29 September,011, respectively. Fruit of each cultivar were sorted into 48 cratesf 100 fruit on the day of harvest and stored at 0.5 ◦C. Four replicaterates of fruit were untreated, or treated with 1 g L−1 DPA (Shieldrite 15%, Pace International, Seattle, WA) for 1 min. The remainingrates were treated with 1 �L L−1 1-MCP at the following treatment

imes (d): 1, 4, 7, 1 + 4, 4 + 7, 1 + 4 + 7, 7 + 14, 7 + 28, 7 + 42, and 7 + 84.-MCP treatments (SmartFreshTM tablets, 0.36% a.i., AgroFresh Inc.,pring House, PA) were applied for 24 h in a 4000 L plastic tent using

release and fan system supplied by the manufacturer.

Technology 78 (2013) 48–54 49

The fruit of both cultivars were stored in air at 0.5 ◦C for up to36 weeks from harvest. Ten fruit per replicate were sampled atharvest, and after removal from storage every six weeks for evalua-tion of internal ethylene concentration (IEC), firmness, soluble solidconcentration (SSC) and titratable acidity (TA) and peeled using ahand-held fruit peeler. Fruit replicates were sampled immediatelyafter removal from storage to minimize warming. The peels werefrozen immediately in liquid nitrogen and then stored at −80 ◦Cuntil used for analysis of �-farnesene and conjugated trienols(CTols). Scald incidence was assessed on 40–50 fruit per replicateafter 36 weeks of storage plus 7 d at 20 ◦C.

2.2. Internal ethylene concentration (IEC)

The IEC of each fruit was measured by gas chromatography ona 1-mL sample of internal gas withdrawn into a syringe through ahypodermic needle inserted into the core cavity (Watkins and Nock,2012). Ethylene was measured using a Hewlett-Packard 5890 seriesII gas chromatograph (Hewlett-Packard, Wilmington, DE) equippedwith a flame ionization detector and fitted with a stainless steelcolumn packed with 60/80 mesh alumina F-1 (2 m × 2 mm, i.d.).Analyses were run isothermally with an oven temperature of 160 ◦Cand injector and detector temperatures of 220 and 250 ◦C, respec-tively. The flow rates for nitrogen, hydrogen and compressed airwere 30, 30 and 230 mL min−1, respectively. Ethylene was quanti-fied by peak area, and an external standard of 10 �L L−1 was usedfor calibration.

2.3. Firmness, soluble solids and titratable acidity

Firmness was measured on opposite sides of each fruit withan EPT-1 pressure tester (Lake City Technical Products, Lake City,Canada) fitted with an 11.1 mm diam. probe. SSC was measured ona fresh juice sample using a digital refractometer (PR-100; AtagoCo. Ltd., Tokyo, Japan). TA was measured using an automatic titra-tor (Metter DL12, Hightstown, NJ). Wedges were cut from 10 applesamples and juiced. Aliquots of 10 mL were titrated to pH 8.1 with0.1 N NaOH and the results expressed as % malic acid.

2.4. Extraction and quantification of ˛-farnesene and CTols

Frozen peel samples were pulverized in liquid N2 and 1 g ofpowder transferred to 15 mL tubes containing 5 mL hexane. Thetubes were sealed and shaken continuously at 20 ◦C for 10 min.After centrifugation, 0.4 mL of the supernatant was filtered througha florisil column and diluted to 4 mL, and then used for estimationof �-farnesene at 232 nm with a Beckman diode array spectropho-tometer (Model DU 7400, Beckman Instruments, Columbia, MD).Appropriate dilutions of hexane extracts with florisil treatment(Huelin and Coggiola, 1968) were measured at 281 and 290 nmfor CTol concentrations. �-Farnesene and CTol concentrationswere calculated using molar extinction coefficients ε232nm = 27,740(Anet, 1969) for �-farnesene and ε281–290nm = 25,000 for CTols(Anet, 1972) and expressed as mmol kg−1 on a fresh weight basis.Although there is a tendency for spectrophotometric estimates of�-farnesene to be higher than HPLC estimates when concentra-tions are low (Whitaker et al., 2000), a comparison of selectedsamples using HPLC showed close similarities for estimates usingour method (Whitaker, pers. commum.).

2.5. Statistical analysis

A completely randomized experimental design was used withfour replications. Data were subjected to analysis of variance(ANOVA), with treatment and storage time as sources of varia-tion. Mean comparisons at P = 0.05 were performed using the least

50 X. Lu et al. / Postharvest Biology and

Table 1Fruit harvest indices, �-farnesene and conjugated trienols (CTols) concentrations(means ± standard error) for ‘Cortland’ and ‘Delicious’ apples at harvest.

‘Cortland’ ‘Delicious’

IEC (�L L−1) 0.090 ± 006 6.43 ± 1.32Firmness (N) 72.2 ± 0.7 75.9 ± 0.6SSC (%) 9.9 ± 0.2 10.3 ± 0.06TA (% malic acid) 0.36 ± 0.02 0.21 ± 0.005

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�-Farnesene (mmol kg−1) 0.08 ± 0.01 0.13 ± 0.02CTols (mmol kg−1) 0.02 ± 0.003 0.04 ± 0.006

ignificant difference (LSD) method. IEC and percentage storageisorder data were subjected to logarithm and arcsine transforma-ions, respectively, before analysis. Pearson correlations were usedo quantify the relationships between IEC, �-farnesene, CTols andcald incidence.

. Results

.1. Harvest quality

‘Cortland’ fruit had preclimacteric IECs at harvest (Table 1).Delicious’ fruit had higher IECs overall, but were variable; the per-entage of fruit with IECs greater than 1 �L L−1 in replicates (n=4)anged from 20 to 50%, respectively. �-Farnesene and CTol concen-rations were low in fruit at harvest (Table 1).

.2. IEC

For clarity of presentation, the results for IECs of the fruit haveeen separated into three groups for each cultivar; Untreatednd DPA (Fig. 1A and D), 1, 4, 1 + 4, 4 + 7, and 1 + 4 + 7d (Fig. 1Bnd E) and 7, 7 + 14, 7 + 28, 7 + 42 and 7 + 84 d (Fig. 1C and F).he IECs of untreated and DPA treated fruit were high with littleffect of treatment for either cultivar (Fig. 1A and D). Overall, theECs for untreated and DPA treated fruit were 75 and 74 �L L−1,espectively, for ‘Cortland’, and 37 and 38 �L L−1, respectively, forDelicious’.

All 1-MCP treatments resulted in lower IECs in both cultivarsFig. 1B, C, E, F), and were always lower than untreated and DPAreated fruit. Delaying 1-MCP treatment until days 4 and 7 resultedn progressively increasing IECs over storage compared with theay 1 treatment. Overall, the IECs in ‘Cortland’ apples when treatedith 1-MCP on days 1, 4 and 7 were 8, 10 and 33 �L L−1, respec-

ively, and for ‘Delicious’ were 3, 4 and 7 �L L−1, respectively.ultiple 1-MCP treatments over the first 7 d of storage, resulted in

imilar overall IECs of 8, 9 and 7 �L L−1 for 1 + 4 d, 4 + 7 d and 1 + 4 + 7 treatments, respectively, for ‘Cortland’. However, for ‘Delicious’,verall IECs were 2 �L L−1 for the 1 + 4 + 7 d, compared with 4 and

�L L−1 for 1 + 4 d, and 4 + 7 d, respectively.The effect of additional 1-MCP treatments during storage to the

d alone treatment was also investigated (Fig. 1C and F). Treatmentf fruit at 7 + 14 d resulted in lower IECs than day 7 alone for ‘Cort-and’ and ‘Delicious’, being 10 and 3 �L L−1, respectively. Increasingelays before the second 1-MCP treatment resulted in progressivelyigher IECs during storage for ‘Cortland’, but to a lesser extent for

Delicious’.

.3. ˛-Farnesene and CTols

�-Farnesene concentrations reached a maximum in untreatednd DPA treated fruit on weeks 12 and 18 in ‘Cortland’ and on

eeks 6 and 12 in ‘Delicious’ apples, thereafter declining over stor-

ge (Figs. 2A and 3A). Overall concentrations were slightly highern untreated ‘Cortland’ fruit (0.57 mmol kg−1) than in untreatedDelicious’ (0.53 mmol kg−1).

Technology 78 (2013) 48–54

Delaying 1-MCP treatment until days 4 and 7 resulted inprogressively increasing �-farnesene concentrations over storagecompared with the day 1 treatment in both ‘Cortland’ (Fig. 2B and C)and ‘Delicious’ (Fig. 3B and C). Overall, �-farnesene concentrationsin ‘Cortland’ apples when treated with 1-MCP on days 1, 4 and 7were 0.35, 0.42 and 0.56 mmol kg−1, respectively, and for ‘Delicious’were 0.36, 0.46 and 0.62 mmol kg−1, respectively.

A repeated 1-MCP treatment after 7 d of storage decreasedthe rate of �-farnesene accumulation compared with day 7 alonein both cultivars, except for the 7 + 84 d treatment in ‘Cort-land’ (Figs. 2C and 3C). The lowest �-farnesene concentrationsoccurred in the 7 + 14 d treatment. Progressively less inhibition of�-farnesene accumulation was detected with longer delays beforethe second treatment for ‘Cortland’.

Overall, CTol concentrations were 24% and 36% lower in DPAtreated fruit than in untreated fruit of ‘Cortland’ and ‘Delicious’,respectively (Figs. 2D and 3D). CTol concentrations increased dur-ing storage, and to a greater extent as treatment time was delayedfrom 1 to 7 d (Figs. 2E, F and 3E, F). There were few differencesbetween the multiple 1-MCP treatments on CTol concentrationswhen applied within the first 7 d. When 1-MCP was applied afterthe initial 7 day treatment, the lowest CTol concentrations occurredin the 7 + 14 d treatment. There was little difference in CTol accu-mulation among the 7 + 28 d, 7 + 42 d and 7 + 84 d treatments.

3.4. Firmness, SCC and TA

3.4.1. ‘Cortland’The flesh firmness of ‘Cortland’ apples decreased from week 18

to week 36 of storage (Table 2). Firmness of the untreated fruitwas lowest, and that of DPA treated fruit higher than untreated atboth storage removals. All 1-MCP treated fruit were firmer thanuntreated or DPA treated fruit.

Within each storage period, the most firm fruit were thosetreated with 1-MCP on days 1, 1 + 4, and 1 + 4 + 7. Delays in 1-MCPtreatment from 1 to 7 d resulted in progressively softer fruit. The4 + 7 d treatment was similar to 4 d alone. The firmness of fruittreated at day 7 and day 7 plus additional treatments on days 14,28, 42 and 84 was similar after 18 weeks of storage, but after 36weeks the double treated fruit were firmer than day 7 alone.

The SSC of the fruit was not affected by storage time, but itwas lowest in the untreated fruit (Table 2). However, SSC wasnot affected consistently by the 1-MCP treatments (Table 2). TheTA decreased during storage, but within each storage period TAswere higher in all 1-MCP treatments than in the untreated and DPAtreated fruit. Few consistent differences were detected within the1-MCP treatments.

3.4.2. ‘Delicious’The flesh firmness of ‘Delicious’ apples decreased from week 18

to week 36 of storage, with the exception of the 1 + 4 + 7 d treat-ment (Table 2). Fruit from all 1-MCP treatments were firmer thanuntreated and DPA treated fruit, but treatment effects were vari-able within each storage period. SSCs were not affected by storageperiod, and while significant treatment effects were detected, theywere also inconsistent. TAs in fruit from all 1-MCP treatments wereusually higher at 18 weeks, and always higher at 36 weeks, thanuntreated and the DPA treatment.

3.5. Superficial scald

For ‘Cortland’, the lowest scald incidence was found in fruit

treated with 1-MCP 1 d, 4 d, 1 + 4 d, and 1 + 4 + 7 d after harvest(Table 3). Treatment with 1-MCP at 4 + 7d and 7 + 14 d, resultedin slightly higher scald. Scald control was relatively poor in fruittreated with 1-MCP on day 7, and 7 d with second applications on

X. Lu et al. / Postharvest Biology and Technology 78 (2013) 48–54 51

Fig. 1. Log internal ethylene concentrations (IECs) in ‘Cortland’ (A–C) and ‘Delicious’ (D–F) apples untreated, treated with 1 g L−1 DPA at harvest or with 1 �L L−1 1-MCP ond wered reated

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ay(s) 1, 4, 1 + 4, 4 + 7, 1 + 4 + 7, 7, 7 + 14, 7 + 28, 7 + 42 and 7 + 84 after harvest. Fruitifferent scale for y axes for 1-MCP treatments compared with untreated and DPA t

8, 42 and 84 d, though better than with DPA. For ‘Delicious’, scaldas detected only in untreated apples (Table 3).

.6. Correlations

�-Farnesene concentrations were correlated with IECs in bothCortland’ (r = 0.820, P < 0.001) and ‘Delicious’ (r = 0.567, P < 0.001).he relationships between scald incidence after storage and CToloncentrations during storage was investigated for ‘Cortland’

ig. 2. �-Farnesene (A–C) and conjugated trienol (CTol) (D–F) concentrations in ‘Cortlanay(s) 1, 4, 1 + 4, 4 + 7, 1 + 4 + 7, 7, 7 + 14, 7 + 28, 7 + 42 and 7 + 84 after harvest. Fruit wereifferent scale for y axes for 1-MCP treatments compared with untreated and DPA treated

stored at 0.5 ◦C up to 36 weeks. Vertical bars represent LSD value at P = 0.05. Note fruit.

(Table 4). Overall, the correlations were highly significant, but ther value declined markedly at week 36. The 1-MCP treatments wereanalyzed separately; a low r value was found at week 6, but thesewere then relatively uniform over time.

4. Discussion

The effectiveness of either DPA or 1-MCP on inhibition of soft-ening, loss of TA, and scald development was much greater for

d’ apples untreated, treated with 1 g L−1 DPA at harvest or with 1 �L L−1 1-MCP on stored at 0.5 ◦C up to 36 weeks. Vertical bars represent LSD value at P = 0.05. Note

fruit.

52 X. Lu et al. / Postharvest Biology and Technology 78 (2013) 48–54

F elicioud wered reated

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ig. 3. �-Farnesene (A–C) and conjugated trienol (CTol) (D–F) concentrations in ‘Day(s) 1, 4, 1 + 4, 4 + 7, 1 + 4 + 7, 7, 7 + 14, 7 + 28, 7 + 42 and 7 + 84 after harvest. Fruitifferent scale for y axes for 1-MCP treatments compared with untreated and DPA t

Delicious’ than for ‘Cortland’ (Tables 2 and 3). A major effect ofultivar on the persistence of DPA and 1-MCP control of scald haseen well described, especially under the rigorous conditions of

ong term air storage (Piretti et al., 1994; Watkins et al., 1995; Fant al., 1999; Little and Holmes, 2000; Watkins et al., 2000; Jung andatkins, 2008). In the case of 1-MCP, the effectiveness of treatment

ppears to be related to whether or not inhibition of ethylene pro-uction is maintained during storage. Cultivars such as ‘Delicious’,

Granny Smith’ and ‘Law Rome’ show long term inhibition of ethyl-ne production, ripening and scald development (Fan et al., 1999;upasinghe et al., 2000; Watkins et al., 2000; Zanella, 2003; Tsantilit al., 2007; Magazin et al., 2010), while others such as ‘McIntosh’nd ‘Cortland’ show ‘escape’ from this inhibition (Fan et al., 1999;atkins et al., 2000; Watkins and Nock, 2005; Tsantili et al., 2007;

ung and Watkins, 2008).

The effect of delayed 1-MCP treatment was also influenced by

ultivar. Control of scald development on ‘Delicious’ was complete,ven if the first application was delayed 7 d after harvest, whereasontrol of scald in ‘Cortland’ was essentially lost with the same

able 2lesh firmness, soluble solids concentration (SSC) and titratable acidity (TA) of ‘Cortland’

reated with 1 g L−1 DPA diphenylamine (DPA) or with 1 �L L−1 1-MCP at various times (d

Treatment ‘Cortland’

Firmness (N) SSC (%) TA (% ma(d) 18 36 18 36 18

Untreated – 43.6 34.8 9.5 9.1 0.204

DPA 0 46.1 39.7 10.0 9.9 0.202

1-MCP 1 64.9 57.8 10.3 9.9 0.252

4 60.3 54.9 10.0 10.3 0.277

1 + 4 64.1 57.3 10.4 10.2 0.272

4 + 7 60.5 55.1 10.0 10.5 0.270

1 + 4 + 7 65.4 57.6 10.2 10.4 0.281

7 56.5 46.9 10.0 10.4 0.252

7 + 14 57.1 50.4 10.2 10.5 0.265

7 + 28 57.0 51.9 10.1 9.8 0.278

7 + 42 55.3 49.7 10.7 10.0 0.262

7 + 84 55.5 48.7 10.3 9.9 0.269

LSD0.05 2.4 0.5 0.0

s’ apples untreated, treated with 1 g L−1 DPA at harvest or with 1 �L L−1 1-MCP on stored at 0.5 ◦C up to 36 weeks. Vertical bars represent LSD value at P = 0.05. Note

fruit.

delay (Table 3). An additional treatment of 1-MCP to ‘Cortland’ onday 14 partly reduced scald incidence compared with 7 d alone.However, additional treatments to the day 7 treatment beyond 14d had no effect on scald control compared with day 7 alone. Fruitquality as assessed by firmness, was best in fruit treated with 1-MCP on days 1, 4, 1 + 4, 4 + 7 and 1 + 4 + 7 (Table 3). The effects of1-MCP on scald and firmness mostly corresponded, the exceptionsbeing days 7 + 14 and 7 + 28. In those cases, firmness was uniformlylower with both treatments whereas scald incidence was lowerwith the additional treatment on day 14 but not on day 28 (Table 3).For ‘Delicious, all 1-MCP treatments resulted in firmer fruit thanuntreated or DPA-treated fruit (Table 2).

The effects of 1-MCP on maintaining fruit quality and inhibitingscald development can be less persistent, depending on cultivar,fruit maturity and handling effects such as delays between harvest

and 1-MCP treatment (Watkins and Nock, 2005; Jung and Watkins,2008; Amarante et al., 2010). It is assumed that reduced effects aredue to the presence of ethylene that competes for existing bindingsites in the cell and the development of new ethylene receptors

and ‘Delicious’ apples after 18 and 36 weeks storage at 0.5 ◦C. Fruit were untreated,ays) after harvest.

‘Delicious’lic acid) Firmness (N) SSC (%) TA (% malic acid)

36 18 36 18 36 18 36

0.130 61.6 54.5 13.5 13.6 0.131 0.0770.156 61.1 51.2 14.4 14.2 0.121 0.0760.217 74.0 69.2 14.1 14.3 0.142 0.1020.218 73.5 66.5 14.2 13.7 0.136 0.0960.226 71.1 67.5 14.3 13.9 0.141 0.1010.236 74.5 69.6 15.0 14.9 0.156 0.1000.231 68.8 67.8 14.0 14.5 0.138 0.0940.201 72.9 66.8 14.8 14.8 0.147 0.0870.215 70.3 65.6 13.6 13.5 0.145 0.1040.237 69.5 66.7 14.8 15.2 0.143 0.0860.210 72.6 66.8 14.3 13.9 0.147 0.0980.191 71.9 66.5 14.3 14.4 0.145 0.095

16 2.6 0.4 0.011

X. Lu et al. / Postharvest Biology and

Table 3Scald incidence in ‘Cortland’ and ‘Delicious’ apples after 36 weeks storage at 0.5 ◦Cplus 7 days at 20 ◦C. Fruit were untreated, treated with 1 g L−1 DPA diphenylamine(DPA) or with 1 �L L−1 1-MCP at various times (days) after harvest. Transformeddata for ‘Cortland’ are presented for comparison of means by LSD at P = 0.05; back-transformed means are shown in parentheses.

Treatment (d) ‘Cortland’ ‘Delicious’

Untreated – 90 (100) 51DPA 0 42 (46) 01-MCP 1 0 (0) 0

4 4 (1) 07 34 (32) 01 + 4 6 (2) 04 + 7 14 (6) 01 + 4 + 7 2 (0.6) 07 + 14 17 (9) 07 + 28 36 (35) 07 + 42 37 (36) 07 + 84 38 (38) 0

LSD0.05 3.9 –

Table 4Pearson correlation coefficient for superficial scald incidence of ‘Cortland’ applesafter 36 weeks air storage plus 7 d at 20 ◦C and conjugated trienols (CTols) concen-trations at successive sampling times during storage. Separate analyses were carriedout for all data and for 1-MCP treatments alone. All relationships were significantat P < 0.001.

Sampling time (weeks) Correlation coefficient

All data 1-MCP treatments only

6 0.906 0.43012 0.845 0.73018 0.857 0.79824 0.848 0.800

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30 0.823 0.77836 0.641 0.700

Blankenship and Dole, 2003; Sisler and Serek, 2003; Zhang et al.,009, 2011). The ethylene data are broadly consistent with thisiew, the IECs of fruit treated with 1-MCP on day 7 with or withoutdditional treatments being higher by week 6 of storage (Fig. 1).nterestingly, even though IECs of ‘Delicious’ were lower than thosef ‘Cortland’ during storage, treatment effects could be detected.

Patterns for �-farnesene and CTols were affected in a similarashion (Figs. 2 and 3) to IEC (Fig. 1). While the large effect of 1-

CP on production of the substrate �-farnesene and its oxidationroducts, CTols, was obvious compared with untreated and DPA-reated fruit, the effects of 1-MCP were generally less so duringhe earlier part of storage. CTols concentrations are often corre-ated with scald incidence (Huelin and Coggiola, 1968; Anet, 1972;

atkins et al., 1995; Whitaker et al., 1997). In our experiment, theorrelations were initially poor for the 1-MCP treatments (Table 4).nexpectedly, the correlations were lower at the last sampling timef 36 weeks than for most earlier time points. CTol accumulationslso increased in 1-MCP treated ‘Delicious’ apples (Fig. 3), and in aashion consistent with the effects of 1-MCP on ethylene produc-ion. However, scald was not detected in any 1-MCP treated fruitTable 3). It is possible that scald was present or developing, butot detectable to the naked eye, or that the low CTol concentra-ions reflected low levels of free radical activity and/or oxidationroducts that were not damaging to the cell.

In conclusion, repeated 1-MCP treatments appear to have great-st impact on fruit quality and scald control of the faster ripeningultivar, ‘Cortland’, when applied within 4 days of harvest. Delayss short as 7 days compromised control of scald and maintenance

f quality, though a repeated application 14 days after harvest wasartially effective. Although CA storage, instead of air storage as

n this experiment, could increase the benefits obtained by laterpplications, the present results strongly support the value of rapid

Technology 78 (2013) 48–54 53

1-MCP application to faster ripening cultivars within a few days ofharvest. The revised label for SmartFreshTM that permits multipleapplications is most beneficial while the rooms are being loadedand during the early part of the storage period.

Acknowledgments

This research was partly supported by Federal Formula FundsNE1036, the New York Apple Research and Development Pro-gram, and AgroFresh, Inc. We thank Dr. Bruce Whitaker, USDA-ARS,Beltsville, for HPLC analyses of �-farnesene and CTols. Xingang Luand Yanping Ma thank the Chinese Scholarship Council for financialsupport.

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