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Postharvest Biology and Technology 59 (2011) 10–15

Contents lists available at ScienceDirect

Postharvest Biology and Technology

journa l homepage: www.e lsev ier .com/ locate /postharvbio

-Methylcyclopropene (1-MCP) delays senescence, maintains quality andeduces browning of non-climacteric eggplant (Solanum melongena L.) fruit

uan F. Massoloa, Analía Concellóna,b, Alicia R. Chavesa, Ariel R. Vicentea,c,∗

Centro de Investigación y Desarrollo en Criotecnología de Alimentos (CCT La Plata, CONICET – Facultad de Ciencias Exactas-UNLP), Calle 47 Esq. 116, La Plata,uenos Aires, CP 1900, ArgentinaComisión de Investigaciones Científicas Pcia, de Buenos Aires CIC-PBA, ArgentinaFacultad de Ciencias Agrarias y Forestales, UNLP, Calle 60 y 119, La Plata, Buenos Aires, CP 1900, Argentina

r t i c l e i n f o

rticle history:eceived 4 February 2010ccepted 4 August 2010

eywords:thylenetorageefrigerationolyphenol oxidase

a b s t r a c t

Ethylene action can be counteracted by 1-methylcyclopropene (1-MCP), which has been used duringpostharvest storage to maintain quality. In this work, we evaluated the effect of 1-MCP treatments oneggplant quality and phenolic metabolism during refrigerated storage. Eggplants (cv. Lucía) were har-vested at commercial maturity, treated with 1-MCP (1 �L/L, 12 h at 20 ◦C), stored at 10 ◦C for 21 d andsubsequently held at 20 ◦C for 2 d. Corresponding controls were stored at 10 ◦C and then transferred to20 ◦C for 2 d. During storage calyx color, damage and chlorophyll content, fruit weight loss and firmness,pulp sugar content, acidity, browning and total phenolics were measured. In addition, polyphenol oxidase(PPO), pyrogallol peroxidase (POD), and phenylalanine ammonia-lyase (PAL) activities were evaluated.

henylalanine ammonia-lyasehenolics

Fruit calyxes showed reduced damage and remained greener in 1-MCP treated than in control fruit. 1-MCP treated eggplants showed lower weight loss. Pulp browning was clearly prevented as a consequenceof 1-MCP exposure, and this was associated with delayed senescence, lower accumulation of total phe-nolics and reduced activity of PAL. The activity of the enzymes PPO and POD involved in the oxidationof phenolics compounds was also decreased in 1-MCP treated fruit. Results suggest that 1-MCP treat-ments delay senescence, prevent browning and are beneficial to complement low temperature storage

on-cl

and maintain quality of n

. Introduction

Eggplant (Solanum melongena L.) is an important non-limacteric fruit, with a worldwide production of around 32 milliononnes (FAOSTAT, 2009). Quality attributes include: white, green,iolet or variegated bright surface without defects, dark green calyxnd absence of seed or pulp browning (Cantwell and Suslow, 2009).ruit deterioration during long term storage is associated withalyx discoloration and pulp browning caused by the oxidation ofhenolic compounds. The level of phenolics has been shown toorrelate with browning in different eggplant varieties (Prohenst al., 2007). In addition, loss of cellular compartmentalization has

een shown to accelerate browning by increasing peroxide levelsnd oxygen partial pressure within the tissues, and by releasinghenolics stored in the vacuoles which can then be readily avail-ble for oxidation by polyphenol oxidases (PPOs) and peroxidases

∗ Corresponding author at: Centro de Investigación y Desarrollo en Criotecnologíae Alimentos (CONICET-UNLP), Calle 47 Esq. 116, La Plata, Buenos Aires, CP 1900,rgentina. Tel.: +54 221 4249287; fax: +54 221 4254853.

E-mail address: arielvicente@quimica.unlp.edu.ar (A.R. Vicente).

925-5214/$ – see front matter © 2010 Elsevier B.V. All rights reserved.oi:10.1016/j.postharvbio.2010.08.007

imacteric eggplant fruit.© 2010 Elsevier B.V. All rights reserved.

(PODs) (Beaulieu et al., 1999; Concellón et al., 2004). Low temper-ature storage is effective for reducing browning reactions and fordelaying eggplant fruit deterioration. However, refrigeration can-not be fully exploited because eggplants are chilling sensitive andshould not be stored for long periods below 7–10 ◦C (Concellón etal., 2007). Controlled or modified atmospheres do not show greatbenefits in eggplant. Reducing oxygen to 3–5% could delay dete-rioration just for a few days (Cantwell and Suslow, 2009). Thecontrol of ethylene production and action is an important com-ponent in postharvest management. The strategies used to protectfruits and vegetables from the negative outcomes of ethylene arebased on avoidance, removal or inhibition of its biosynthesis and/oraction. 1-Methylcyclopropene (1-MCP) is a cyclic alkene able toblock ethylene action (Sisler and Serek, 1999, 2003; Sisler, 2006).Ethylene production in eggplant is moderate and the compoundis not considered crucial for ripening control. However, severalchanges related to fruit deterioration such as calyx senescence

and pulp browning have been linked with the action of the hor-mone in various commodities (Watkins, 2006). 1-MCP treatmentshave been useful to protect fruits and vegetables from exogenousand self-produced ethylene, increasing their postharvest life andproviding more flexibility during storage, distribution and retail

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Blankenship and Dole, 2003; Watkins, 2006). Several works havehown the usefulness of 1-MCP in maintaining quality and delayingipening of climacteric fruits (Vilas-Boas and Kader, 2006, 2007),ut the number of studies evaluating the effects of 1-MCP in non-limacteric commodities is more limited and document diverseesults depending on the product. In whole strawberries 1-MCPreatments maintained fruit firmness and colour (Jiang et al., 2001)ut in another study Bower et al. (2003) concluded that treatmentith 1-MCP is unlikely to be cost-effective. The use of 1-MCP in min-

mally processed strawberries before and/or after cutting did notave a significant effect on fruit appearance or firmness (Aguayot al., 2006). Nilsson (2005) reported little benefit from fumigationith 1-MCP in cucumbers unless exogenous ethylene is present.

n other cases, positive results have been observed. In pineapple,-MCP treatments reduced internal browning and ascorbic acidecline (Selvarajah et al., 2001) and in loquat 1-MCP was effectiveor preventing deterioration (Cai et al., 2006). No works have beenublished that analyze the influence of reducing ethylene action onggplant quality and postharvest life. In this work we evaluated theffect of 1-MCP treatments on eggplant fruit quality and phenolicetabolism during refrigerated storage.

. Materials and methods

.1. Chemicals

Glucose, phenol, polyvinylpolypyrrolidone (PVPP), phenylethyl sulfonyl fluoride (PMSF). 2-Mercaptoethanol, l-

henylalanine, H2O2, pyrogallol, pyrocatechol were purchasedrom Sigma–Aldrich Chemical Co. (St. Louis, MO, USA). Acetone andthanol, were purchased from Mallinckrodt Baker Inc. (Phillips-urg, NJ, USA). Folin-Ciocalteu reagent and, EDTA were purchasedrom Anedra Bs. As., Argentina. All other chemicals and solventsere of the highest commercial grade and used without furtherurification.

.2. Plant material, treatments and storage

One hundred and twenty purple American eggplant fruit (S.elongena L.) cv. Lucía, weighing 170–190 g each, were harvested,

ransported to the laboratory and divided into two groups (a) con-rol and (b) 1-methylcyclopropene-treated (1-MCP). To performhe 1-MCP treatments the fruit were held in a plastic chamber. The

ass of 1-MCP commercial formulation necessary to reach a con-entration of 1 �L/L of 1-MCP was weighed in a beaker and putithin the chamber. The chamber was then hermetically closed

nd water was added with a syringe through a septum locatedn the chamber lid in order to release the 1-MCP. After 12 h at0 ◦C the fruit were taken out, packed in groups of two in plasticPET) trays and covered with perforated PVC (50 �m thick). Cor-esponding controls were placed in a plastic chamber which wasermetically closed without the presence of 1-MCP and held for2 h at 20 ◦C. After that time, fruit were removed, packed in plasticPET) trays, and covered with perforated PVC (50 �m thick). Con-rol and treated fruit were stored at 10 ◦C for 21 d (RH 85–90%) andhen held at 20 ◦C for 2 d (21 + 2 d). Twenty fruit for each treatmentnd storage time were taken for sampling. Calyx and pulp samplesere taken and immediately analyzed or otherwise frozen in liq-id N2 and stored at −80 ◦C until use. The experiment was repeatedhree times (three independent harvests).

.3. Calyx damage, color and chlorophyll

Calyx damage was evaluated by determining the percentagef area showing discoloration. Twenty fruit were evaluated forach treatment and storage time. For chlorophyll measurements,

nd Technology 59 (2011) 10–15 11

0.4 g of calyx tissue was frozen in liquid nitrogen, ground ina mill, and added to 10 mL of acetone:water (80:20). Sampleswere stirred in the dark for 10 min and the suspension was cen-trifuged at 17,000 × g for 10 min at 4 ◦C. The supernatant was usedto measure chlorophylls according to Lichtenthaler (1987). Fourindependent extracts were done for each treatment and storagetime. Calyx and pulp color were evaluated with a colorimeter(Minolta, Model CR-400, Osaka, Japan) by measuring the param-eters L*, a* and b*. The hue angle was calculated for calyx tissueas: hue = 180 + arc tan b*/a*. Twenty fruits were evaluated for eachtreatment and storage time and two measurements were done oneach fruit on opposite sides of the calyx (n = 40).

2.4. Weight loss

Weight loss was determined for 20 fruit from each treatment,storage time, and harvest. Fruit were weighed individually beforepacking and during storage. Results were expressed as percentageof weight loss (WL) as described below:

WL (%) = 100 × IW − FWIW

,

with IW, initial fruit weight (before storage) and FW, final fruitweight (after storage).

2.5. Firmness

Firmness was measured using a texture analyzer (TA.XT2, Sta-ble Micro Systems Texture Technologies, Scarsdale, NY, USA) fittedwith a 3 mm flat probe. Each fruit was compressed 6 mm at theequatorial zone at a rate of 0.5 mm/s, and the maximum force devel-oped during the test was recorded. Three measurements were doneper fruit, and 20 independent control or treated fruit were analyzedfor each storage time. Results were expressed in Newtons.

2.6. Pulp browning, total sugars and acidity

A Minolta Colorimeter, model CR-400, was used to determinethe lightness of pulp tissue by measuring the parameter L* (0 = blackand 100 = white). Discs of approximately 0.5 cm cross-section wereexcised from the central zone of the fruit and pulp color was imme-diately measured. Twenty fruit were evaluated for each treatmentand storage time and two discs were evaluated per fruit (n = 40).For sugar determinations, frozen tissue was processed in a mill and1 g of the resulting powder was extracted with 5 mL of ethanol.The mixture was vortexed, centrifuged at 17,000 × g for 10 minat 4 ◦C, and the supernatant was brought to 100 mL with water.Total sugars were measured with the anthrone reagent (Yemmand Willis, 1954). Briefly, aliquots (50 �L) of the ethanolic extractswere taken and brought to 500 �L with water. One milliliter of 2 g/Lanthrone, prepared in 98% (w/w) H2SO4, was added slowly to thetest tubes in a water-ice bath. Then, samples were held at 100 ◦C for10 min, cooled in water, and the absorbance at 620 nm was mea-sured in a spectrophotometer (Beckman Model UV Mini-1240, CA,USA). Glucose was used as a standard and results were expressedas grams of glucose per kilogram of fresh weight. Four measure-ments were done for each treatment and storage time analyzed.For acidity and pH measurements approximately 50 g of fruit pulpwere frozen in liquid nitrogen, ground in a mill and 15 g of theresulting powder were added to 100 mL of water. The pH was mea-

sured with a pH-meter (Oakton Model 510, IL USA), and acidity wasdetermined titrimetically with 0.1 mol/L NaOH until pH 8.2 (AOAC,1980). Four samples were evaluated for each treatment and stor-age time. Results were expressed as [H+] mol L−1, on a fresh weightbasis.

12 J.F. Massolo et al. / Postharvest Biology and Technology 59 (2011) 10–15

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ig. 1. (A) Calyx appearance and (B) whole fruit appearance in control and 1-MCP trd (21 + 2 d).

.7. Total phenolics

Frozen pulp tissue was ground in a mill and approximately 2 gere added to 6 mL ethanol. The suspension was vortexed and cen-

rifuged at 17,000 × g for 10 min at 4 ◦C. The supernatant was savednd brought to 100 mL with water. Two hundred microliters of 1:1olin-Ciocalteu reagent were pipetted into test tubes containing00 �L of ethanolic extracts and 800 �L of water. Samples wereortexed and, after 3 min at 20 ◦C, 400 �L of 20% (w/v) Na2CO3n 0.1 mol/L NaOH was added. Then, each test tube was broughto 3 mL with water, vortexed and incubated at 20 ◦C for 1 h. Thebsorbance at 760 nm was measured and phenolic compounds con-ent was calculated by using phenol as a standard. Three extractsere prepared for each treatment and storage time analyzed and

ach one was measured in duplicate. Results were expressed asilligrams of phenol per kilogram of fresh fruit.

.8. Enzyme activities

For phenylalanine ammonia-lyase (PAL) approximately 20 gf frozen tissue were ground in a mill and 3 g of the resultingowder were homogenized in 10 mL of Na2B4O7·10H2O buffer0.1 mol/L, pH 8.8), 2-mercaptoethanol 0.05 mol/L, EDTA 2 mmol/L,0 g/L polyvinylpolypyrrolidone, 1 mmol/L phenyl methyl sulfonyluoride. The suspension was centrifuged at 19,000 × g for 10 mint 2 ◦C and the supernatant was dialyzed against Na2B4O7·10H2Ouffer (0.1 mol/L; pH 8.8) by using a dialysis membrane with aut off of 6–8 kDa (Spectrapor®, Spectrum Labs Inc. CA, USA). Theeaction mixture contained 2.2 mL of Na2B4O7·10H2O (30 mmol/L,

H 8.8), 500 �L of 0.01 mol/L l-phenylalanine and 300 �L of enzy-atic extract. Samples were incubated at 35 ◦C and the activity was

etermined spectrophotometrically at 290 nm through an increasen absorbance caused by the accumulation of trans-cinnamic acidZucker, 1965). Results were expressed as change in optical density

eggplants during storage at 10 ◦C for 21 d and after subsequent transfer to 20 ◦C for

(�OD) in a second per kilogram of fruit under the assay condi-tions. For pyrogalol peroxidase (POD) approximately 50 g of frozenpulp tissue were ground and 5 g of the resulting powder wereadded to 20 mL of phosphate buffer (0.05 mol/L, pH 6.5; 10 g/LPVPP, 1 mmol/L PMSF and 1 mol/L NaCl). The suspension was cen-trifuged at 19,000 × g for 10 min at 2 ◦C and the supernatant wasused to assay pyrogallol peroxidase activity. The reaction mixturecontained 300 �L of phosphate buffer (50 mmol/L, pH 6.5); 300 �Lof 8 mmol/L H2O2; 200 �L of 45 mmol/L pyrogallol and 50 �L ofenzymatic extract. The reaction mixture was incubated at 25 ◦C andthe enzymatic activity was determined spectrophotometrically at430 nm (Converso and Fernandez, 1995). Results were expressedas change in optical density (�OD) in a second per kilogram offruit under the assay conditions. Finally, for polyphenol oxidase(PPO), approximately 50 g of frozen pulp tissue were ground ina mill and 5 g of the resulting powder were homogenized with20 mL of phosphate buffer (50 mmol/L, pH 6.5; 10 g/L PVPP and 0.1%,v/v Tritón-X100). The suspension was centrifuged at 19,000 × g for15 min at 2 ◦C, and the supernatant was used to assay PPO activity.The reaction mixture contained phosphate buffer (0.1 mmol/L, pH6.5); 1 mL of 20 mmol/L pyrocatechol and 50 �L of extract in a totalvolume of 3 mL. The reaction mixture was incubated at 25 ◦C andthe enzymatic activity was determined spectrophotometrically at410 nm (Serradell et al., 2000). Results were expressed as changein optical density (�OD) in a second per kilogram of fruit underthe assay conditions. Three extracts were prepared for each treat-ment and storage time analyzed, and each one was measured intriplicate.

2.9. Statistical analysis

Experiments were performed in a factorial design. Data wereanalyzed by ANOVA and means were compared by a Fisher test ata significance level of 0.05.

J.F. Massolo et al. / Postharvest Biology and Technology 59 (2011) 10–15 13

Table 1Weight loss (n = 20), firmness (n = 60), acidity (n = 4) and sugars (n = 4) in control and 1-MCP treated eggplants after storage at 10 ◦C for 21 d (21) and subsequent transfer to20 ◦C for 2 d (21 + 2). Values with different letters are significantly different at P < 0.05.

Storage

0 21 21 + 2

Weight loss (%) Control 0 7.6a 8.6a1-MCP 0 5.2b 6.2b

Firmness (N) Control 19.6a 13.2c 10.2d1-MCP 20.1a 15.8b 16.2b

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Acidity ([H ] mol L ) Control1-MCP

Sugars (g kg−1) Control1-MCP

. Results and discussion

.1. Calyx deterioration

Calyx senescence was one of the first symptoms of quality reduc-ion observed during eggplant storage at 10 ◦C (Fig. 1A). It startedt the sepal tips after 1 week and was manifested as wilting andiscoloration. Later, the affected area increased and by the endf the storage period fungal development was observed. Calyxesemained greener and fresher in 1-MCP treated fruit (Fig. 1A).lthough at the end of storage some senescence symptoms werelso observed in 1-MCP treated fruit, the percentage of damagedrea per fruit was significantly lower than in control fruit (Fig. 2A).clear reduction in both calyx lightness and hue angle was found

n control fruit at the end of the storage period, indicating a changerom bright green to yellow-brownish color (Fig. 2B and C). In con-rast, the reduction of lightness and hue angle in 1-MCP treatedruit was significantly lower. Finally, chlorophyll content decreased

ig. 2. (A) Damage (n = 20) (B) lightness (L*, n = 40), (C) color (hue, n = 40) and (D)hlorophyll content (n = 4) in the calyx of control and 1-MCP treated eggplants dur-ng storage at 10 ◦C for 21 d and after subsequent transfer to 20 ◦C for 2 d (21 + 2 d).ifferent letters indicate significant differences at P < 0.05.

0.010c 0.014b 0.018a0.010c 0.015b 0.018a21b 22b 30ab22b 23b 28a

during storage in both control and 1-MCP treated fruit (Fig. 2D).Although the reduction was slightly lower in the latter group, thedifferences were not significant. Results suggest that 1-MCP treat-ment was clearly effective in delaying eggplant calyx deteriorationand that the main differences between control and 1-MCP treatedfruit were associated with reduced browning.

3.2. Dehydration, firmness, sugars and acidity

1-MCP treated eggplants maintained higher gloss than controlfruit (Fig. 1B). Jha et al. (2002) found a negative linear correlationbetween eggplant fruit dehydration and surface gloss. Dehydrationsymptoms were clearly visible in control fruit after 21 d at 10 ◦C and2 d at 20 ◦C (21 + 2 d) (Fig. 1B). These results agree with weight lossdata, which were higher in the controls than in 1-MCP treated fruit(Table 1). In addition, treated eggplants maintained firmness betterthan control fruit (Table 1). Previous studies have shown that waterexchange in eggplant occurs mostly through the calyx (Díaz Pérez,1998). It is possible to associate the decrease in softening, weightloss and dehydration with the maintenance of calyx integrity in 1-MCP treated fruit, which might then result in higher resistance towater vapor flux. Finally, titratable acidity increased during stor-age but no differences were observed between control and treatedfruit (Table 1). This is coincident with results described by otherauthors (Concellón et al., 2007; Esteban et al., 1989). Sugar con-tent did not show variations during storage at 10 ◦C but when thefruit was transferred to 20 ◦C a significant, but slight increase wasobserved in both control and 1-MCP treated eggplants (Table 1).

3.3. Seed and pulp browning

Browning is an important problem during storage of fresh fruitsand vegetables (López-Gálvez et al., 1996). In eggplant it is usu-ally associated with long term storage or chilling injury and greatlyreduces fruit quality (Concellón et al., 2007; Cantwell and Suslow,2009; Molinar et al., 1996). Browning is the result of reactionsbetween phenolic compounds and oxidative enzymes due to cel-lular disruption. Browning symptoms started initially in the seeds,but after transfer to 20 ◦C it also was observed in the pulp. After21 d, control eggplants showed higher seed browning than 1-MCP treated fruit (Fig. 3A). No differences were observed in pulpcolor initially or after 21 d between control and 1-MCP treatedfruit, but upon transfer to 20 ◦C (21 + 2 d) pulp browning increasedmarkedly in non-treated eggplants (Fig. 3B). In contrast, pulp light-ness remained unchanged in 1-MCP treated fruit.

3.4. Biosynthesis of phenolic compounds

The level of phenolic compounds has been associated with egg-plant browning susceptibility. In fact, in a collection of eggplanthybrids and varieties a positive correlation between total pheno-lics and browning was found (Prohens et al., 2007). The content

14 J.F. Massolo et al. / Postharvest Biology and Technology 59 (2011) 10–15

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ig. 3. (A) Seed browning and (B) pulp lightness (L*, n = 40) in control and 1-MCP t21 + 2 d). Different letters indicate significant differences at P < 0.05.

f phenolics at harvest was around 800 mg/kg (Fig. 4A). Chloro-enic acid (3-caffeoyl quinic acid) represented more than 90% ofhe ethanol soluble phenolic compounds (data not shown). Dur-ng 21 d of storage at 10 ◦C phenolics increased in control fruit,

hile no changes were detected in 1-MCP treated fruit. One of theegulatory steps in the biosynthesis of phenolics is catalyzed byhenylalanine ammonia-lyase (PAL). At harvest, no difference inAL activity was found between control and treated fruit, but after1 d of low temperature storage higher PAL activity was detected

n the control (Fig. 4B). It has been demonstrated in several systemshat PAL is induced by low temperature stress (Hyodo et al., 1991;

anchez-Ballesta et al., 2000; Lafuente et al., 2001). Particularly inggplant, an increase of PAL during refrigeration has been reportedKozukue et al., 1979). Results suggest that the induction of PAL

ight be, in part, an ethylene dependent response. This has been

ig. 4. (A) Phenolic compounds (n = 3) and (B) phenylalanine ammonia-lyase (PAL,= 3) in control and 1-MCP treated eggplants during storage at 10 ◦C for 21 d and

ubsequent transfer to 20 ◦C for 2 d (21 + 2 d). Different letters indicate significantifferences at P < 0.05.

eggplants during storage at 10 ◦C for 21 d and subsequent transfer to 20 ◦C for 2 d

suggested also by the increase of PAL at low temperatures associ-ated with bleeding development in plums (Manganaris et al., 2007,2008).

After transfer to 20 ◦C the content of phenolic compoundsincreased in 1-MCP treated fruit, reaching values similar to the con-trol, which showed no variations when held at 20 ◦C. Interestingly,after 21 + 2 d, no correlation was detected between PAL activityand the accumulation of phenolic compounds since lower enzymeactivity and rapid accumulation of phenolics were detected in 1-MCP treated eggplants. One possibility to explain the observationthat higher PAL activity did not result in a build up of phenolics inthe control might be that the higher PAL activity occurred togetherwith rapid browning (consuming the compounds) (Fig. 3B). Thehigher rate of browning in control fruit upon transfer to 20 ◦Cmight be due to higher tissue disruption associated with senes-cence and/or due to the induction of phenolics degrading enzymessuch as polyphenol oxidases (PPOs) and peroxidases (PODs).

3.5. Activity of enzymes involved in the oxidation of phenoliccompounds

The function of PPOs and PODs has been associated withdefenses against pathogens and insects, but from the perspective offruits and vegetables as foods, they are recognized as serious prob-lems (Haard et al., 1974; Concellón et al., 2004). PPOs catalyze theoxidation of phenolics to quinones using oxygen as a final electronacceptor, while for peroxidases the final electron acceptor is hydro-gen peroxide. After quinone formation, secondary non-enzymaticreactions result in the accumulation of melanin-like pigments, giv-ing a brown undesirable appearance to the tissues. Both PPOs andPODs have been shown to be induced by biotic and abiotic stres-sors. In this work, PPO activity increased in control eggplants at 21 dof storage at 10 ◦C (Fig. 5A) as has been reported by Concellón et

al. (2004) working with another eggplant variety. Induction of PPOtranscripts has been also observed in pineapple stored at low tem-peratures (Stewart et al., 2001). In the present work after transferto 20 ◦C (21 + 2 d), control fruit still maintained higher PPO activitythan 1-MCP treated fruit. Finally, POD showed higher activity than

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ig. 5. (A) Polyphenol oxidase (PPO, n = 3) and (B) pyrogallol peroxidase (POD, n = 3)n control and 1-MCP treated eggplants during storage at 10 ◦C for 21 d and afterubsequent transfer to 20 ◦C for 2 d (21 + 2 d). Different letters indicate significantifferences at P < 0.05.

-MCP treated fruit after by 21 and 21 + 2 d of storage (Fig. 5B).he difference was still observed after transfer at 20 ◦C (21 + 2 d).esults suggest that ethylene is involved in the increase of therowning-related enzymes PPO and POD during eggplant storage.

Different approaches have been taken to control enzymaticrowning. In some cases, it has been prevented by using antiox-

dants such as ascorbic acid, chelating agents such as EDTA, anditric acid, which can reduce the pH and limit the activity of PPOsnd PODs (Altunkaya and Gökmen, 2008). These strategies are valu-ble in commodities showing browning in external tissues and inrocessed products, but their usefulness is reduced in commodi-ies in which the manifestation of the disorder occurs internally.ow O2 atmospheres have been effective in some products, whileefrigerated storage is highly recommended if the commoditiesre not chilling sensitive. Herein, results showed that eggplant (cv.ucía) browning can be prevented by 1-MCP treatments. This mightave been due to reduced loss of cellular compartmentalizationo that substrates for browning were not available for oxidationeactions. In fact, data on calyx damage, weight loss, firmness andehydration suggest that 1-MCP delayed eggplant senescence. 1-CP treatments also decreased PAL activity and the accumulation

f phenolic compounds. In addition, treated fruit show lower PPOnd POD activity after long term storage. Overall, results suggesthat 1-MCP treatments might then be suitable to maintain qual-ty and extend the postharvest life of refrigerated non-climactericggplant (cv. Lucía) fruit.

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