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Managing ‘Bartlett’ pear fruit ripening with 1-methylcyclopropene reapplication during cold storage
Postharvest Biology and Technology 113 (2016) 125–130
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Postharvest Biology and Technology journal homepage: www.elsevier.com/locate/postharvbio
Managing ‘Bartlett’ pear fruit ripening with 1-methylcyclopropene reapplication during cold storage Luiz C. Argentaa , James P. Mattheisb,* , Xuetong Fanc, Cassandro V.T. Amaranted a
EPAGRI, Estação Experimental, 89500-000 Caçador, SC, Brazil USDA, ARS Tree Fruit Research Laboratory, 1104 N. Western Avenue, Wenatchee, WA 98801, USA USDA, ARS ERRC, 600 E. Mermaid Lane, Wyndmoor, PA 19038, USA d UDESC, Centro de Ciências Agroveterinárias, Avenida Luiz de Camões, 2090, CEP 88520-000 Lages, SC, Brazil b c
A R T I C L E I N F O
A B S T R A C T
Article history: Received 7 October 2015 Received in revised form 19 November 2015 Accepted 21 November 2015 Available online 7 December 2015
Repeated low-dose 1-MCP-applications were evaluated during cold storage of ‘Bartlett’ pear fruit to overcome long-term ripening inhibition of a high dose 1-MCP treatment at harvest. Fruit were exposed to 1-MCP at 0, 0.42, 4.2 or 42 mmol m 3 at harvest in year one, and to 0, 0.42 or 42 mmol m 3 in year two, and then stored in air at 0.5 C. In year two, fruit exposed to 1-MCP at 0.42 mmol m 3 at harvest were retreated during cold storage once (after 38 days) or twice (after 38 and 68 days), when ethylene production in samples removed from cold storage exceeded 0.014 hmol kg 1 s 1 within 7 days at 20 C. 1MCP was re-applied once at 0.42 or 4.2 mmol m 3 or twice at 0.42 or 4.2 then 42 mmol m 3. In year one, fruit treatment at harvest with 4.2 or 42 mmol m 3 1-MCP provided similar ripening delay during 120 days in storage followed by 7 days at 20 C, while fruit treated with 0.42 mmol m 3 1-MCP was not different from the control. In year two, fruit treated at harvest with 0.42 mmol m 3 1-MCP and retreated with 0.42 mmol m 3 (when ethylene production was already high) did not delay subsequent fruit ripening. Fruit treated at harvest with 42 mmol m 3 1-MCP or with 0.42 mmol m 3 at harvest and then +4.2 + 42, had similar peel yellow color, TA and SSC, but higher firmness after 180 days storage, compared to control fruit after 60 days storage. After 180 days storage, the severity of superficial scald, senescent scald and core browning on fruit treated only at harvest with 42 mmol m 3 were lower than on control fruit and similar to on fruit treated with 0.42 mmol m 3 at harvest and then retreated with +4.2 + 42. Therefore, a low dose application of 1-MCP at harvest followed by reapplication with higher doses based on fruit ethylene production capacity after removal from cold storage can extend ‘Bartlett’ pear storage life while allowing ripening to occur after mid-term storage. The efficiency of this procedure will depend on timing and 1-MCP reapplication concentration. Published by Elsevier B.V.
Keywords: Pyrus communis L. Ethylene inhibition Quality Firmness Physiological disorders
1. Introduction The marketing season of European pears can be scheduled and expanded by promoting (Villalobos-Acuña and Mitcham, 2008) or inhibiting (Ekman et al., 2004) ethylene production and action. Postharvest treatment of European pears with 1-MCP inhibits fruit ethylene production and respiration, delays ripening, and reduces the development of physiological disorders and decay after harvest (Baritelle et al., 2001; Argenta et al., 2003; Kubo et al., 2003; Hiwasa et al., 2003; Calvo and Sozzi, 2004, 2009; Calvo, 2004; Ekman et al., 2004; Trinchero et al., 2004; Mwaniki et al., 2005; Spotts et al., 2007; Villalobos-Acuña et al., 2011a). Although
* Corresponding author. E-mail address: [email protected] (J.P. Mattheis). http://dx.doi.org/10.1016/j.postharvbio.2015.11.009 0925-5214/ Published by Elsevier B.V.
postharvest application of 1-MCP provides potential benefits to improve storability, ripening capacity of 1-MCP-treated pears can be unpredictable after storage (Mattheis et al., 2000; Mitcham et al., 2001; Bai et al., 2006). European pear fruit ripening including softening is necessary to attain ideal sensory attributes and fruit characteristics for market acceptance (Kappel et al., 1995). The time period required for 1-MCP-treated pear fruit to resume the ripening process (starting with ethylene production) after 1-MCP treatment depends on the cultivar (Bai and Chen, 2005; Eccher Zerbini et al., 2005; Bai et al., 2006), 1-MCP concentration applied (Argenta et al., 2003; Ekman et al., 2004; Rizzolo et al., 2005; Calvo and Sozzi, 2004, 2009), timing of 1-MCP treatment (Calvo, 2003; Trinchero et al., 2004; Villalobos-Acuña and Mitcham, 2008; DeEll and Ehsani-Moghaddam, 2011), maturity stage of the fruit at the time of treatment, season (Calvo, 2003, 2004; Calvo and Sozzi, 2004; Bai and Chen, 2005; Moya-León et al., 2006; Villalobos-
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Acuña et al., 2011a), ethylene concentration and temperature during 1-MCP treatment (Villalobos-Acuña et al., 2011b), and storage temperature and gas composition after 1-MCP treatment (Rizzolo et al., 2005; Bai et al., 2006; Villalobos-Acuña et al., 2011b). Pears treated with 1-MCP have failed to recover their ability to ripen properly (Chen and Spotts, 2005; Chiriboga et al., 2013), even after treatment with ethylene (Argenta et al., 2003). 1-MCP treatment, at harvest, at low concentrations (4.2–21 mmol m 3) allows ripening of ‘Bartlett’ pear fruit within a reasonable period after removal from storage (Calvo, 2003; Ekman et al., 2004; Bai et al., 2006; Villalobos-Acuña et al., 2011a). However, such low concentrations may lose their effectiveness within a shorter period than anticipated depending on the many factors described previously. To overcome this difficulty, pears could be treated with a low concentration of 1-MCP at harvest and 1-MCP applications could be repeated when 1-MCP effects begin to dissipate if longer storage periods are necessary (Mattheis et al., 2000; Mitcham et al., 2001; Ekman et al., 2004). Considering the multiple factors influencing efficacy of 1-MCP inhibition of ‘Bartett’ pear ripening and the requirement for fruit ethylene production and action to promote ripening, the relationship between recovery of ethylene production capacity following 1-MCP treatment and reestablishment of ripening inhibition by 1MCP was evaluated. In this study, the effects of 1-MCP dose and repetitive treatments of 1-MCP at low and high doses after various periods of cold storage were evaluated as a means to extend storage life while maintaining the capacity for ‘Bartlett’ fruit to ripen after short- or long-term storage. 2. Material and methods ‘Bartlett’ pears were harvested from a commercial orchard in Wenatchee, WA, USA in two consecutive years. Fruit was placed into a cold storage room held at 0.5 C then, after 24 h, were exposed to 1-MCP gas at 0 (control), 0.42, 4.2 or 42 mmol m 3 in year one, and at 0 (control), 0.42 or 42 mmol m 3 in year two. After 1-MCP treatment, fruit were stored in air at 0.5 C. In year two, fruit were removed periodically from cold storage and ethylene production and respiration rates monitored during 7 days at 20 C. Sub-samples of fruit treated at harvest with 0.42 mmol m 3 1-MCP were retreated with either 0.42, 4.2 or 42 mmol m 3 1-MCP when ethylene production exceeded 0.014 hmol kg 1 s 1 within 7 days at 20 C. Using this protocol, 1-MCP was reapplied once at 38 days or twice at 38 and 68 days cold storage as follows: (I) 0.42 mmol m 3 at harvest + 0.42 mmol m 3 at 38 days; (II) 0.42 mmol m 3 at harvest + 4.2 mmol m 3 at 38 days; (III) 0.42 mmol m 3 at harvest + 0.42 mmol m 3 at 38 days + 42 mmol m 3 at 68 days; (IV) 0.42 mmol m 3 at harvest + 4.2 mmol m 3 at 38 days + 42 mmol m 3 at 68 days. Fruit at 0.5 C were exposed to 1-MCP for 24 h in a 250 L steel container with a steel lid sealed by a water moat. 1-MCP was generated at 20 C from EthylBloc1 powder and buffer solution (BioTechnology for Horticulture Inc., Burr Ridge, IL) in a sealed 5.1 L glass bottle and then pumped from the mixing bottle into the steel container for 15 min in a closed loop. Headspace concentration of 1-MCP in the treatment chamber was analyzed using a HP 5880 gas chromatograph (Hewlett Packard, Palo Alto, CA) using 1-butene (Scott, Plumsteadville, PA) as an external standard. The GC column was a CP Porabond Q, 0.32 mm i.d. 10 m length (Varian, Lake Forest, CA). He carrier gas linear velocity was 40 cm s 1, H2 and air flows were 0.42 and 5 mL s 1, respectively. The injector and detector temperatures were 60 and 150 C, respectively. The analysis was conducted with an oven temperature program with an initial temperature of 50 C increasing to 150 C at 0.42 C s 1.
Fruit maturity and quality were individually evaluated at harvest and after 60, 120 or 180 days storage plus 1 and 7 days at 20 C. Flesh firmness was measured on two pared surfaces per fruit using a penetrometer with an 8 mm tip (Lake City Technical, Kelowna, BC, Canada). TA was determined by titrating 10 mL of juice with 0.1 M KOH to pH 8.2 using an autotitrator (Radiometer, Copenhagen, Denmark). Soluble solids content (SSC) in juice sample was measure using an Atago N1 refractometer (Atago, Tokyo). Starch score was determined visually using a 1–6 scale (1 = full, 6 = no starch) after staining an equatorial section of each pear with a 5 mg L 1 I-KI solution. Color on a disorder free area of peel was recorded as CIE L*a*b* with a chromameter (Model CR200, Minolta, Japan) using CIE illuminant C and an 8-mm measuring aperture. Hue was calculated from a* and b* (Hunter and Harold, 1987). Superficial scald was visually assessed using a scale from 1 to 7 with consideration of both severity and areas of surface affected: 1, no scald; 2, light scald, <33% of the surface area affected; 3, light scald, 33–66% of surface affected; 4; light scald, >66% of surface affected; 5, dark scald, <33% of the surface area affected; 6, dark scald, 33–66% of surface affected; 7, dark scald, >66% of surface affected. Incidence of senescent scald, core browning and decay were rated as absent (1) or present (2). Superficial and senescent scald were differentiated based on symptom appearance (Pierson et al., 1971). Rates of ethylene production and respiration were assessed in four replicates of five pears per treatment, enclosed in 20 L plexiglass chambers, maintained at 20 C and supplied with compressed, ethylene-free air at 100 mL min 1. Gas samples of 0.5 mL were collected from effluent air of each chamber for CO2 and ethylene analysis. The concentration of CO2 was determined by a gas chromatograph (HP5890; Hewlett-Packard, Palo Alto, CA) equipped with a methanizer (John T. Booker, Austin, TX), flame ionization detector and a 0.6 m stainless steel column (2 mm i.d.) packed with 80–100 mesh Porapak Q (Supelco, Bellefonte, PA). Oven, detector, methanizer and injection temperatures were 50, 200, 290 and 150 C, respectively. Gas flows for N2, H2 and air were 1.2, 0.5 and 5 mL s 1, respectively. Analyses of ethylene concentration in gas sample was determined by a gas chromatograph (HP 5880A; Hewlett-Packard) equipped with a flame ionization detector and a 0.3 m glass column (3.2 mm i.d.) packed with 80– 100 mesh Porapak Q (Supelco, Bellefonte, PA). Oven, injector and detector temperatures were 60, 60 and 150 C, respectively. N2, H2 and air flows were 0.5, 0.5 and 5 mL s 1, respectively. There were 40 single fruit replications per treatment for quality assessments. Data were subjected to analysis of variance using SAS (SAS Institute, Cary, NC). Treatment mean separations were determined by Fischer’s least significance (a = 0.05). 3. Results 3.1. Year one At harvest, ‘Bartlett’ pears had flesh firmness 86.5 6.9N (SDV), starch index 1.1 0.1, soluble solids 11.0 0.5% and peel Hue 115 0.9. Increased ethylene production, fruit softening, yellowing (decreased Hue) and loss of acidity exhibited by control fruit were delayed by 1-MCP treatment at 4.2 or 42 mmol m 3 but not at 0.42 mmol m 3 (Fig. 1). Maximum ethylene production was similar regardless of treatment. Effects of 4.2 and 42 mmol m 3 1-MCP treatments on ethylene production, firmness, titratable acidity and Hue were similar through 60 days storage plus 7 days at 20 C. However, fruit treated with 42 mmol m 3 had lower ethylene production and higher firmness and titratable acidity after 120 days plus 7 days at 20 C compared with fruit treated with
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Fig. 1. Ethylene production and quality of ‘Bartlett’ pear fruit at harvest and following cold storage plus 7 days at 20 C. Fruit were treated at harvest with 0.42, 4.2 or 42 mmol m 3 1-MCP. Controls and fruit treated with 0.42 or 4.2 mmol m 3 1MCP severely affected by senescent scald and/or decay were not analyzed after 180 days storage. Inside vertical bars or numbers indicates LSD0.05 for each days of storage. Data from year one.
4.2 mmol m 3. A high incidence of disorders for controls and fruit treated with 0.42 or 4.2 mmol m 3 prevented assessment after 180 days. The impact of 1-MCP on development of physiological disorders was also dependent on treatment concentration and storage duration (Table 1). Superficial scald was detected only after 180 days in storage, while senescent scald was visible on fruit assessed after 120 and 180 days. 1-MCP applied at 42 mmol m 3 prevented the development of superficial scald and senescent scald through 180 days in storage but 0.42 mmol m 3 had no effect on disorder development. 1-MCP applied at 4.2 mmol m 3 prevented the development of superficial and senescent scald after 120 days storage, but it reduced only slightly the development of superficial scald and senescent scald after 180 days storage. Development of severe senescent scald prevented assessment of superficial scald after 7 days at 20 C. Fruit treated with 1-MCP at 4.2 or 42 mmol m 3 were less affected by decay after 180 days storage compared with controls or fruit treated with 0.42 mmol m 3 1-MCP. Core browning was not detected on any fruit during year one. 3.2. Year two At harvest, ‘Bartlett’ pears had flesh firmness of 111.4 8.4 N (SDV), starch index of 1.4 0.6, 10.5 0.9% SSC and 116 0.9 Hue.
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Production of CO2 and ethylene by control fruit increased during 7 days at 20 C after harvest and following 15–120 days of cold storage (Fig. 2). The increase in CO2 and ethylene production by control fruit held at 20 C right after harvest was less than that of fruit chilled for 15 days or more. All 1-MCP treatment concentrations delayed the increase in ethylene production and respiration rate relative to controls. However, the duration of the 1-MCP effect was greatest for the highest treatment concentration (42 mmol m 3). Fruit treated with 0.42 or 42 mmol m 3 1-MCP at harvest had rates of ethylene and CO2 evolution following 120 or 180 days, respectively, similar to those of controls following 60 days. High incidence of physiological disorders in controls and fruit treated only at harvest with 0.42 mmol m 3 1-MCP or retreated once with 0.42 mmol m 3 after 38 days in storage prevented determination of respiration, ethylene production and fruit quality after 180 days cold storage (Table 2) . Respiration and ethylene production rates by fruit treated with 0.42 mmol m 3 1-MCP at harvest were additionally reduced by 1MCP retreatments during storage depending on 1-MCP reapplication doses and how many times 1-MCP was reapplied. Fruit retreated once with 0.42 mmol m 3 after 38 days in storage had CO2 and ethylene production, after 120 days storage, similar to that of fruit treated only at harvest with 0.42 mmol m 3. However, fruit retreated with 4.2 mmol m 3 after 38 days and 42 mmol m 3 after 68 days in storage had lower respiration and ethylene production, after 120 days storage, compared with fruit treated only at harvest with 0.42 mmol m 3 and similar respiration and ethylene production, after 120 and 180 days storage, to fruit treated only at harvest with 42 mmol m 3 1-MCP. Fruit retreated once with 4.2 mmol m 3 1-MCP after 38 days in storage had similar respiration but lower ethylene production after 60 and 120 days storage compared with fruit treated only at harvest with 0.42 mmol m 3. After the reapplication on day 68 with 42 mmol m 3, ethylene production was higher after 120 and 180 days for fruit retreated on day 38 with 0.42 mmol m 3 compared with 4.2 mmol m 3. Control fruit softened, yellowed (decreased Hue) and lost TA during the first 60 days in storage plus 7 days at 20 C (Fig. 3). Fruit treated with 1-MCP were significantly firmer, greener (higher hue value), and had higher TA compared with control fruit after 60 days. Only exposure to the highest 1-MCP concentration (42 mmol m 3) at harvest resulted in firmer and greener fruit after 120 days of cold storage plus 7 days ripening compared with controls and fruit exposed at harvest to 0.42 mmol m 3. The response to 0.42 mmol m 3 1-MCP applied at harvest was similar to that of fruit retreated once with 0.42 mmol m 3 after 38 days in storage. In contrast, the period over which ripening was slowed in fruit treated at harvest with 0.42 mmol m 3 1-MCP was extended by retreatment at 4.2 and 42 mmol m 3. Fruit retreated with 3 4.2 mmol m 1-MCP after 38 days and 42 mmol m 3 after 68 days in storage had higher firmness, TA and peel hue, and developed less core browning, after 120 days storage, than fruit treated only at
Table 1 Physiological disorders and decay of ‘Bartlett’ pear after 120 and 180 days of cold storage. Fruit were treated at harvest with 1-MCP at 0 (control), 0.42, 4.2 or 42 mmol m Data from year one. Dose of 1-MCP (mmol m 3) 0 (control) 0.42 4.2 42 LSD0.05 a b
Superficial scald (1–7)a
Senescent scald (1–2)b
Decay (1–2)b
120 days
180 days
120 days
180 days
120 days
180 days
1.0 1.0 1.0 1.0 –
6.7 6.2 4.0 1.0 1.1
1.8 1.6 1.0 1.0 0.35
2.0 1.9 1.6 1.0 0.1
1.0 1.0 1.0 1.0 0
1.6 1.6 1.0 1.2 0.3
Superficial scald was visually assessed after 1 day at 20 C using a scale from 1 (no scald) to 7 (dark scald and >60% of the fruit surface affected). Senescent scald and decay were visually assessed after 7 days at 20 C as clear (1) or affected (2).
3
.
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Fig. 2. Ethylene production and respiration rates of ‘Bartlett’ pear fruit during 7 days ripening at 20 C following 0–180 days cold storage. Fruit were treated at harvest (h) with 1-MCP at 0 (control), 0.42 or 42 mmol m 3, or treated at harvest with 0.42 mmol m 3 1-MCP and then retreated once with 0.42 or 4.2 mmol m 3 1-MCP after 38 days in storage (1-MCP 0.42(h) + 0.42(38d) and 1-MCP 0.42(h) + 4.2(38d)) or twice with 0.42 or 4.2 and 42 mmol m 3 1-MCP, after 38 and 68 days in storage, respectively (1-MCP 0.42(h) + 0.42(38d) + 42(68d) and 1-MCP 0.42(h) +4.2(38d) + 42(68d)). Controls and fruit treated with 0.42(h) or 0.42(h) + 0.42(38d) mmol m 3 1-MCP severely affected by senescent scald were not analyzed after 180 days storage plus 7 days at 20 C. Inside numbers indicate LSD0.05 for significant treatment days interaction. Data from year two.
harvest with 0.42 mmol m 3. After 180 days storage, fruit retreated with 4.2 mmol m 3 1-MCP after 38 days and 42 mmol m 3 after 68 days in storage had similar firmness, TA, peel hue, and severity of superficial scald, senescent scald and core browning to fruit treated only at harvest with 42 mmol m 3. The retreatment with 0.42 and 42 mmol m 3, after 38 and 68 days in storage, respectively, also improved retention of fruit quality in comparison to 0.42 mmol m 3 applied only at harvest. However, these retreatments were less effective for firmness retention and prevention of physiological disorders after 180 days storage compared with retreatment with 4.2 and 42 mmol m 3 applied at 38 and 68 days, respectively. After 60 days, fruit retreated once with 4.2 mmol m 3 1-MCP after 38 days in storage had similar TA but higher firmness and hue than fruit treated only at harvest with 0.42 mmol m 3 1-MCP. However, after 120 days, fruit retreated once with 4.2 mmol m 3 1MCP had firmness, TA peel hue and severity of physiological disorders similar to those of fruit treated only at harvest with 0.42 mmol m 3 1-MCP, but higher firmness and TA and less physiological disorders than control fruit. Fruit treated at harvest with 42 mmol m 3 1-MCP and fruit retreated twice with 1-MCP (0.42 mmol m 3 at harvest + 4.2 mmol
m 3 after 38 days + 42 mmol m 3 after 68 days in storage) had, after 180 days storage, peel yellow color, TA and SSC similar to, but firmness higher than control fruit stored 60 days. However, controls were not affected by physiological disorders after 60 days storage while few symptoms of physiological disorders were detected, after 180 days of storage, on fruit treated at harvest with 42 mmol m 3 1-MCP and/or retreated twice with 1-MCP. Physiological disorders were not detected after 7 days ripening, following 60 days of storage on fruit of any treatment, in both years. 4. Discussion Results herein confirm 1-MCP delays ‘Bartlett’ pear ripening making its use a potentially effective method to extend the marketing season while reducing fruit deterioration. However, the delayed ripening and prevention of physiological disorders and decay following 1-MCP application can be associated with unpredictable ripening after removal from storage (Argenta et al., 2003; Chen and Spotts, 2005; Bai et al., 2006; Chiriboga et al., 2013). The effects of 1-MCP are not readily reversed by exposing 1-MCP treated fruit to ethylene (Argenta et al., 2003;
Table 2 Physiological disorders of ‘Bartlett’ pear after 120 and 180 days of cold storage. Fruit were treated at harvest (h) with 1-MCP at 0 (control), 0.42 or 42 mmol m 3, or treated at harvest with 1-MCP at 0.42 mmol m 3 and then retreated once with 1-MCP at 4.2 mmol m 3 after 38 days in storage (1-MCP 0.42(h) + 4.2(38d)) or twice with 1-MCP, at 4.2 and 42 mmol m 3 after 38 and 68 days in storage, respectively (1-MCP 0.42(h) + 4.2(38d) + 42(68d)). Data from year two. Treatment (mmol m 3) Control 1-MCP 0.42(h) 1-MCP 42(h) 1-MCP 0.42(h) + 4.2(38d) 1-MCP 0.42(h) + 4.2(38d) + 42(68d) LSD0.05 a b
Superficial scald (1–7)a
Senescent scald (1–2)b
Core browning (1–2)b
180 days
120 days
180 days
120 days
180 days
6.6 6.1 1.0 3.0 1.5 0.96
1.2 1.1 1.0 1.0 1.0 0.21
2.0 1.9 1.1 1.6 1.0 0.19
1.6 1.4 1.0 1.2 1.0 0.23
2.0 2.0 1.3 1.9 1.3 0.26
Superficial scald was visually assessed after 1 day at 20 C using a scale from 1 (no scald) to 7 (dark scald and >60% of the fruit surface affected). Senescent scald and decay were visually assessed after 7 days at 20 C as clear (1) or affected (2).
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42h 0.42h +4.238d +4268d 0.42h +0.4238d +4268d 0.42h +4.238d h 38d 0.42 +0.42 h 0.42 Control
110
80
Hue
Firmness (N)
100
60
100
40 90
20
11 0.3
SSC (%)
TA (%)
0.4
10
0
60
120
180 0
60
120
180
Days in storage Fig. 3. Firmness, titratable acidity (TA), peel color (hue value) and soluble solids content (SSC) of ‘Bartlett’ pear fruit at harvest and following cold storage plus 7 days at 20 C. Fruit were treated at harvest (h) with 1-MCP at 0 (control), 0.42 or 42 mmol m 3, or treated at harvest with 0.42 mmol m 3 1-MCP and then retreated once with 0.42 or 4.2 mmol m 3 1-MCP, after 38 days in storage (1-MCP 0.42(h) + 0.42(38d) and 1-MCP 0.42(h) + 4.2(38d)) or twice with 0.42 or 4.2 and 42 mmol m 3 1-MCP, after 38 and 68 days in storage, respectively (1-MCP 0.42(h) + 0.42(38d) + 42(68d) and 1-MCP 0.42(h) + 4.2(38d) + 42(68d)). Controls and fruit treated with 0.42(h) or 0.42(h) + 0.42(38d) mmol m 3 1-MCP severely affected by senescent scald were not analyzed after 180 days storage plus 7 days at 20 C. Inside vertical bars indicates LSD0.05 for each days of storage. Data from year two.
Trinchero et al., 2004) and ‘Bartlett’ pear fruit must ripen to a yellow color and soft and juicy texture to have market acceptance (Kappel et al., 1995). Therefore, an effective protocol that assures 1MCP treated pear fruit will ripen after transport and marketing is a commercial necessity. Identification of 1-MCP concentrations for each pear cultivar and storage period has been one means to avoid excessive 1-MCP inhibition of fruit ripening. The winter pear cultivar ‘d’Anjou’ is very sensitive to 1-MCP and requires lower 1-MCP concentrations to extend the storage potential compared with ‘Bartlett’ (Bai et al., 2006). Concentrations of 4.2–12.6 mmol m 3 for short-term (60– 90 days) and 16.8–25.2 mmol m 3 for long-term storage (90– 140 days) allow Bartlett pear fruit to ripen within a reasonable time after removal from storage (Calvo, 2003; Ekman et al., 2004). However, interactive effects of 1-MCP concentration, fruit maturity at harvest and storage period alter fruit response to 1-MCP (Calvo, 2003). In the present study, ripening of fruit with firmness of 111 N and 86.5 N at harvest in two years was and was not, respectively, delayed by treatment with 0.42 mmol m 3 1-MCP at harvest. Lateharvest ‘Williams’ pears require higher 1-MCP concentrations to maintain fruit firmness, acidity and green color than early-harvest fruit (Calvo, 2003). The long-term ripening inhibition of ‘Bartlett’ pears by 1-MCP can be modulated by delaying 1-MCP treatment after harvest (DeEll and Ehsani-Moghaddam, 2011) and temperature management both prior to 1-MCP treatment (Wang and Sugar, 2015) and after storage (Bai et al., 2006). Multiple applications of 1-MCP at low concentrations have been suggested as a mean to extend effects of 1-MCP for long periods while keeping the ability of fruit
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to ripening after short periods of storage (Mattheis et al., 2000; Mitcham et al., 2001). In this study, Bartlett pear fruit treated at harvest with a low 1-MCP concentration (0.42 mmol m 3) and then retreated twice with 4.2 and 42 mmol m 3 after 38 and 68 days of cold storage, respectively, had quality similar to that of fruit treated at harvest with 1-MCP at high concentration (42 mmol m 3), after 120 and 180 days in storage. The single 1-MCP reapplication after 38 days storage, when fruit attained ability to produce ethylene at 0.018 hmol kg 1 s 1 (within 7 days at 20 C), was more effective at concentration of 4.2 than at 0.42 mmol m 3, to delay ripening and prevent disorders after 120 and 180 days storage. Similarly, the second reapplication with 42 mmol m 3, after 68 days of storage, was less effective on fruit that had attained ability to produce 0.2 hmol kg 1 s 1 of ethylene than on fruit that had attained ability to produce 0.05 hmol kg 1 s 1 (within 7 days at 20 C). The reduction of 42 mmol m 3 1-MCP reapplication efficacy as fruit ethylene production increased is consistent with Ekman et al. (2004). Retreatment of ‘Conference’ and ‘Abbé Fétel’ pear fruit with low concentrations of 1-MCP (1.05 and 2.1 mmol m 3) after every 60 days of cold storage had little additional effect to 1-MCP applied at harvest (Eccher Zerbini et al., 2005; Rizzolo et al., 2005). Efficacy of 1-MCP retreatment therefore appears to depend in part on the state of fruit ripening capacity as assessed by monitoring of fruit ethylene production. The rate of fruit ripening during storage is affected by 1-MCP concentration applied at harvest and by fruit maturity at harvest as well as by other factors such as season and production region. It has been hypothesized that the conformation of the ethylene receptor is altered by the binding of agonists (ethylene) or antagonists (1-MCP) with agonist binding promoting ethylene responses following its dissociation from receptors while antagonist remains bound preventing ethylene action (Sisler and Serek 1997; Sisler, 2006). Similarly, Binder and Bleecker (2003) proposed that 1-MCP suppresses the ethylene response pathway by locking permanently the receptor in an active (inhibiting) confirmation. The long period of ripening inhibition of pear fruit from a single 24 h exposure to 42 mmol m 3 1-MCP and subsequent fruit insensitivity to exogenous ethylene (Argenta et al., 2003; Trinchero et al., 2004) support strong, perhaps irreversible, interaction between 1-MCP and ethylene receptors in European pear fruit. Transitory ripening inhibition following 1-MCP application at low (0.42 mmol m 3) concentration has been suggested to result from regeneration of ethylene receptors (Sisler and Serek, 1997; Pirrung et al., 2008; Sisler, 2006). Degradation of ethylene receptors is also a mechanism governing ethylene biosynthesis and perception (McClellan and Chang, 2008). Ethylene receptor gene expression patterns characterized during ripening after 1-MCP treatment indicate differential duration of 1-MCP effects in apple and peach fruit are related to differences in ratio, expression patterns and/or turnover of ethylene receptors (Dal Cin et al., 2006). Expression of ethylene receptor genes in apple fruit are induced at the transcriptional level during maturation and ripening and delayed by 1-MCP treatment although with different patterns depending on receptor homologs and fruit cultivar (Wiersma et al., 2007; Tatsuki et al., 2009; Varanasi et al., 2013; Yang et al., 2013). Increased expression of ethylene receptor transcripts during cold storage and/or ripening has also been demonstrated for pear fruit (El-Sharkawy et al., 2003; Chiriboga et al., 2013) with 1-MCP treatment causing delay, suppression, or stimulation of specific ethylene receptor genes in ‘Conference’ pears (Chiriboga et al., 2013). While the regulation of ethylene-sensitivity in 1-MCP treated pears appears complex, the identification of bio-markers related to resumption of ripening by 1-MCP treated fruit may enable more efficient postharvest management of 1-MCP treated pear fruit.
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5. Conclusions Postharvest treatment with 1-MCP delayed ‘Bartlett’ pear fruit ripening following cold storage with the duration of 1-MCPinduced responses dependent on 1-MCP concentration. Reapplication of 1-MCP can extend storage life of ‘Bartlett’ fruit while allowing proper ripening to occur at regular interval during cold storage. The efficiency of reapplication is dependent in part on fruit ethylene production capacity and 1-MCP reapplication concentration. A physiological indicator, in this case fruit ethylene production after removal from storage, rather than a predetermined schedule, may increase the efficacy of 1-MCP retreatment protocols. Acknowledgements The authors thank David Buchanan and Janie Countryman for excellent technical assistance. Partial funding for this work was received from the Northwest Pear Committee. References Argenta, L.C., Fan, X.T., Mattheis, J.P., 2003. Influence of 1-methylcyclopropene on ripening, storage life, and volatile production by ‘d’Anjou’ cv. pear fruit. J. Agric. Food Chem. 51, 3858–3864. Bai, J., Chen, P.M., 2005. Extending shelf-life of partially ripened ‘d’Anjou’ pears by 1MCP treatment. Acta Hortic. 671, 325–331. Bai, J., Mattheis, J.P., Reed, N., 2006. Re-initiating softening ability of 1methylcyclopropene-treated ‘Bartlett’ and ‘d’Anjou’ pears after regular air or controlled atmosphere storage. J. Hortic. Sci. Biotechnol. 81 (6), 959–964. Baritelle, A., Hyde, G.M., Fellman, J.K., Varith, J., 2001. Using 1-MCP to inhibit the influence of ripening on impact properties of pear and apple tissue. Postharvest Biol. Technol. 23, 153–160. Binder, B.M., Bleecker, A.B., 2003. A model for ethylene receptor function and 1methylcyclopropene action. Acta Hortic. 628, 177–187. Calvo, G., 2003. Effect of 1-methylcyclopropene (1-MCP) on pear maturity and quality. Acta Hortic. 628, 203–211. Calvo, G., 2004. Efecto del 1-metilciclopropeno (1-MCP) en peras cv. Williams cosechadas en dos estados de madurez. Rev. Invest. Agropecu. 33, 3–26. Calvo, G., Sozzi, G.O., 2004. Improvement of postharvest storage quality of ‘Red Clapp’s’ pears by treatment with 1-methylcyclopropene at low temperature. J. Hortic. Sci. Biotechnol. 79, 930–934. Calvo, G., Sozzi, G.O., 2009. Effectiveness of 1-MCP treatments on ‘Bartlett’ pears as influenced by the cooling method and the bin material. Postharvest Biol. Technol. 51, 49–55. Chen, P.M., Spotts, R.A., 2005. Changes in ripening behaviors of 1-MCP-treated ‘d’Anjou’ pears after storage. Int. J. Fruit Sci. 5 (3), 3–18. Chiriboga, M.A., Saladié, M., Bordonaba, J.G., Recasens, I., Garcia-Mas, J., Larrigaudiere, C., 2013. Effect of cold storage and 1-MCP treatment on ethylene perception, signaling and synthesis: Influence on the development of the evergreen behaviour in ‘Conference’ pears. Postharvest Biol. Technol. 86, 212–220. Dal Cin, V., Rizzini, F.M., Botton, A., Tonutti, P., 2006. The ethylene biosynthetic and signal transduction pathways are differently affected by 1-MCP in apple and peach fruit. Postharvest Biol. Technol. 42, 125–133. DeEll, J.R., Ehsani-Moghaddam, B., 2011. Timing of postharvest 1-methylcyclopropene treatment affects Bartlett pear quality after storage. Can. J. Plant Sci. 91, 853–858. Eccher Zerbini, P., Cambiaghi, P., Grassi, P., Grassi, M., Rizzolo, A., 2005. The effect of 1-MCP on the quality of ‘Conference’ and ‘Abbé Fétel’ pears. Acta Hortic. 671, 397–403. Ekman, J.H., Clayton, M., Biasi, W.V., Mitcham, E.J., 2004. Interaction between 1-MCP concentration, treatment interval and storage time for ‘Bartlett’ pears. Postharvest Biol. Technol. 31, 127–136. El-Sharkawy, I., Jones, B., Li, Z.G., Lelievre, J.M., Pech, J.C., Latche, A., 2003. Isolation and characterization of four ethylene perception elements and their expression
during ripening in pears (Pyrus communis L.) with/without cold requirement. J. Exp. Bot. 54, 1615–1625. Hunter, R.S., Harold, R.W., 1987. The Measurement of Appearance, second ed. Wiley & Sons, pp. 411. Hiwasa, K., Kinugasa, Y., Amano, S., Hashimoto, A., Nakano, R., Inaba, A., Kubo, Y., 2003. Ethylene is required for both the initiation and progression of softening in pear (Pyrus communis L.) fruit. J. Exp. Bot. 54 (383), 771–779. Kappel, F., Fisher-Fleming, R., Hogue, E.J., 1995. Ideal pear sensory attributes and fruit characteristics. HortScience 30, 988–993. Kubo, Y., Hiwasa, K., Omondi Owino, W., Nakano, R., Inaba, A., 2003. Influence of time and concentration of 1-MCP application on the shelf life of pear ‘La France’ fruit. HortScience 38 (7), 1414–1416. Mattheis, J., Fan, X., Argenta, L., 2000. Responses of apple and pear fruit to 1methylcyclopropene. Proceedings of the 20th Annual Washington Tree Fruit Postharvest Conference . http://postharvest.tfrec.wsu.edu/pages/PC2000DD. McClellan, C.A., Chang, C., 2008. The role of protein turnover in ethylene biosynthesis and response. Plant Sci. 175, 24–31. Mitcham, E.J., Mattheis, J., Bower Biasi, B., Clayton, M., 2001. Responses of European pears to 1-MCP. Perish. Handl. Q. 108, 16–19. Moya-León, M.A., Vergara, M., Bravo, C., Montes, M.H., Moggia, C., 2006. 1-MCP treatment preserves aroma quality of ‘Packham’s Triumph’ pears during long-term storage. Postharvest Biol. Technol. 42, 185–197. Mwaniki, M.W., Mathooko, F.M., Matsuzaki, M., Hiwasa, K., Tateishi, A., Ushijima, K., Nakano, R., Inaba, A., Kubo, Y., 2005. Expression characteristics of seven members of the b-galactosidase gene family in ‘La France’ pear (Pyrus communis L.) fruit during growth and their regulation by 1-methylcyclopropane during postharvest ripening. Postharvest Biol. Technol. 36, 253–263. Pierson, C.F., Ceponis, M.J., McColloch, L.P., 1971. Market diseases of apples, pears, and quinces. Agriculture Handbook No. 376. USDA, ARS. http://postharvest. tfrec.wsu.edu/market/Home. Pirrung, M.C., Bleecker, A.B., Inoue, Y., Rodriguez, F.I., Sugawara, N., Wada, T., Zou, Y., Binder, B.M., 2008. Ethylene receptor antagonists: strained alkenes are necessary but not sufficient. Chem. Biol. 15, 313–321. Rizzolo, A., Cambiagni, P., Grassi, M., Zerbini, P.E., 2005. Influence of 1methylcyclopropene and storage atmosphere on changes in volatile compounds and fruit quality of Conference pears. J. Agric. Food Chem. 53 (25), 1781–1789. Sisler, E.C., 2006. The discovery and development of compounds counteracting ethylene at the receptor level. Biotechnol. Adv. 24, 357–367. Sisler, E.C., Serek, M., 1997. Inhibitors of ethylene responses in plants at the receptor level: recent developments. Physiol. Plant. 100, 577–582. Spotts, R.A., Sholberg, P.L., Randall, P., Serdani, M., Chen, P.M., 2007. Effects of 1-MCP and hexanal on decay of d’Anjou pear fruit in long-term cold storage. Postharvest Biol. Technol. 44, 101–106. Tatsuki, M., Hayama, H., Nakamura, Y., 2009. Apple ethylene receptor protein concentrations are affected by ethylene, and differ in cultivars that have different storage life. Planta 230, 407–417. Trinchero, G.D., Sozzi, G.O., Covatta, F., Fraschina, A.A., 2004. Inhibition of ethylene action by 1-methylcyclopropene extends postharvest life of ‘Bartlett’ pears. Postharvest Biol. Technol. 32, 193–204. Varanasi, V., Shin, S., Johnson, F., Mattheis, J.P., Zhu, Y., 2013. Differential suppression of ethylene biosynthesis and receptor genes in ‘Golden Delicious’ apple by preharvest and postharvest 1-MCP treatments. Plant Growth Regul. 32, 585–595. Villalobos-Acuña, M., Mitcham, E.J., 2008. Ripening of European pears: the chilling dilemma. Postharvest Biol. Technol. 49, 187–200. Villalobos-Acuña, M., Biasi, W.V., Flores, S., Jiang, C.-Z., Reid, M.S., Willits, N.H., Mitcham, E.J., 2011a. Effect of maturity and cold storage on ethylene biosynthesis and ripening in ‘Bartlett’ pears treated after harvest with 1-MCP. Postharvest Biol. Technol. 59, 1–9. Villalobos-Acuña, M., Biasi, W.V., Mitcham, E.J., Holcroft, D., 2011b. Fruit temperature and ethylene modulate 1-MCP response in ‘Bartlett’ pears. Postharvest Biol. Technol. 60, 17–23. Wang, Y., Sugar, D., 2015. 1-MCP efficacy in extending storage life of ‘Bartlett’ pears is affected by harvest maturity, production elevation, and holding temperature during treatment delay. Postharvest Biol. Technol. 103, 1–8. Wiersma, P.A., Zhang, H., Lu, C., Quail, A., Toivonen, P.M.A., 2007. Survey of the expression of genes for ethylene synthesis and perception during maturation and ripening of ‘Sunrise’ and ‘Golden Delicious’ apple fruit. Postharvest Biol. Technol. 44, 204–211. Yang, X.T., Song, J., Campbell-Palmer, L., Fillmore, S., Zhang, Z., 2013. Effect of ethylene and 1-MCP on expression of genes involved in ethylene biosynthesis and perception during ripening of apple fruit. Postharvest Biol. Technol. 78, 55–66.
Contents lists available at ScienceDirect
Postharvest Biology and Technology journal homepage: www.elsevier.com/locate/postharvbio
Managing ‘Bartlett’ pear fruit ripening with 1-methylcyclopropene reapplication during cold storage Luiz C. Argentaa , James P. Mattheisb,* , Xuetong Fanc, Cassandro V.T. Amaranted a
EPAGRI, Estação Experimental, 89500-000 Caçador, SC, Brazil USDA, ARS Tree Fruit Research Laboratory, 1104 N. Western Avenue, Wenatchee, WA 98801, USA USDA, ARS ERRC, 600 E. Mermaid Lane, Wyndmoor, PA 19038, USA d UDESC, Centro de Ciências Agroveterinárias, Avenida Luiz de Camões, 2090, CEP 88520-000 Lages, SC, Brazil b c
A R T I C L E I N F O
A B S T R A C T
Article history: Received 7 October 2015 Received in revised form 19 November 2015 Accepted 21 November 2015 Available online 7 December 2015
Repeated low-dose 1-MCP-applications were evaluated during cold storage of ‘Bartlett’ pear fruit to overcome long-term ripening inhibition of a high dose 1-MCP treatment at harvest. Fruit were exposed to 1-MCP at 0, 0.42, 4.2 or 42 mmol m 3 at harvest in year one, and to 0, 0.42 or 42 mmol m 3 in year two, and then stored in air at 0.5 C. In year two, fruit exposed to 1-MCP at 0.42 mmol m 3 at harvest were retreated during cold storage once (after 38 days) or twice (after 38 and 68 days), when ethylene production in samples removed from cold storage exceeded 0.014 hmol kg 1 s 1 within 7 days at 20 C. 1MCP was re-applied once at 0.42 or 4.2 mmol m 3 or twice at 0.42 or 4.2 then 42 mmol m 3. In year one, fruit treatment at harvest with 4.2 or 42 mmol m 3 1-MCP provided similar ripening delay during 120 days in storage followed by 7 days at 20 C, while fruit treated with 0.42 mmol m 3 1-MCP was not different from the control. In year two, fruit treated at harvest with 0.42 mmol m 3 1-MCP and retreated with 0.42 mmol m 3 (when ethylene production was already high) did not delay subsequent fruit ripening. Fruit treated at harvest with 42 mmol m 3 1-MCP or with 0.42 mmol m 3 at harvest and then +4.2 + 42, had similar peel yellow color, TA and SSC, but higher firmness after 180 days storage, compared to control fruit after 60 days storage. After 180 days storage, the severity of superficial scald, senescent scald and core browning on fruit treated only at harvest with 42 mmol m 3 were lower than on control fruit and similar to on fruit treated with 0.42 mmol m 3 at harvest and then retreated with +4.2 + 42. Therefore, a low dose application of 1-MCP at harvest followed by reapplication with higher doses based on fruit ethylene production capacity after removal from cold storage can extend ‘Bartlett’ pear storage life while allowing ripening to occur after mid-term storage. The efficiency of this procedure will depend on timing and 1-MCP reapplication concentration. Published by Elsevier B.V.
Keywords: Pyrus communis L. Ethylene inhibition Quality Firmness Physiological disorders
1. Introduction The marketing season of European pears can be scheduled and expanded by promoting (Villalobos-Acuña and Mitcham, 2008) or inhibiting (Ekman et al., 2004) ethylene production and action. Postharvest treatment of European pears with 1-MCP inhibits fruit ethylene production and respiration, delays ripening, and reduces the development of physiological disorders and decay after harvest (Baritelle et al., 2001; Argenta et al., 2003; Kubo et al., 2003; Hiwasa et al., 2003; Calvo and Sozzi, 2004, 2009; Calvo, 2004; Ekman et al., 2004; Trinchero et al., 2004; Mwaniki et al., 2005; Spotts et al., 2007; Villalobos-Acuña et al., 2011a). Although
* Corresponding author. E-mail address: [email protected] (J.P. Mattheis). http://dx.doi.org/10.1016/j.postharvbio.2015.11.009 0925-5214/ Published by Elsevier B.V.
postharvest application of 1-MCP provides potential benefits to improve storability, ripening capacity of 1-MCP-treated pears can be unpredictable after storage (Mattheis et al., 2000; Mitcham et al., 2001; Bai et al., 2006). European pear fruit ripening including softening is necessary to attain ideal sensory attributes and fruit characteristics for market acceptance (Kappel et al., 1995). The time period required for 1-MCP-treated pear fruit to resume the ripening process (starting with ethylene production) after 1-MCP treatment depends on the cultivar (Bai and Chen, 2005; Eccher Zerbini et al., 2005; Bai et al., 2006), 1-MCP concentration applied (Argenta et al., 2003; Ekman et al., 2004; Rizzolo et al., 2005; Calvo and Sozzi, 2004, 2009), timing of 1-MCP treatment (Calvo, 2003; Trinchero et al., 2004; Villalobos-Acuña and Mitcham, 2008; DeEll and Ehsani-Moghaddam, 2011), maturity stage of the fruit at the time of treatment, season (Calvo, 2003, 2004; Calvo and Sozzi, 2004; Bai and Chen, 2005; Moya-León et al., 2006; Villalobos-
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Acuña et al., 2011a), ethylene concentration and temperature during 1-MCP treatment (Villalobos-Acuña et al., 2011b), and storage temperature and gas composition after 1-MCP treatment (Rizzolo et al., 2005; Bai et al., 2006; Villalobos-Acuña et al., 2011b). Pears treated with 1-MCP have failed to recover their ability to ripen properly (Chen and Spotts, 2005; Chiriboga et al., 2013), even after treatment with ethylene (Argenta et al., 2003). 1-MCP treatment, at harvest, at low concentrations (4.2–21 mmol m 3) allows ripening of ‘Bartlett’ pear fruit within a reasonable period after removal from storage (Calvo, 2003; Ekman et al., 2004; Bai et al., 2006; Villalobos-Acuña et al., 2011a). However, such low concentrations may lose their effectiveness within a shorter period than anticipated depending on the many factors described previously. To overcome this difficulty, pears could be treated with a low concentration of 1-MCP at harvest and 1-MCP applications could be repeated when 1-MCP effects begin to dissipate if longer storage periods are necessary (Mattheis et al., 2000; Mitcham et al., 2001; Ekman et al., 2004). Considering the multiple factors influencing efficacy of 1-MCP inhibition of ‘Bartett’ pear ripening and the requirement for fruit ethylene production and action to promote ripening, the relationship between recovery of ethylene production capacity following 1-MCP treatment and reestablishment of ripening inhibition by 1MCP was evaluated. In this study, the effects of 1-MCP dose and repetitive treatments of 1-MCP at low and high doses after various periods of cold storage were evaluated as a means to extend storage life while maintaining the capacity for ‘Bartlett’ fruit to ripen after short- or long-term storage. 2. Material and methods ‘Bartlett’ pears were harvested from a commercial orchard in Wenatchee, WA, USA in two consecutive years. Fruit was placed into a cold storage room held at 0.5 C then, after 24 h, were exposed to 1-MCP gas at 0 (control), 0.42, 4.2 or 42 mmol m 3 in year one, and at 0 (control), 0.42 or 42 mmol m 3 in year two. After 1-MCP treatment, fruit were stored in air at 0.5 C. In year two, fruit were removed periodically from cold storage and ethylene production and respiration rates monitored during 7 days at 20 C. Sub-samples of fruit treated at harvest with 0.42 mmol m 3 1-MCP were retreated with either 0.42, 4.2 or 42 mmol m 3 1-MCP when ethylene production exceeded 0.014 hmol kg 1 s 1 within 7 days at 20 C. Using this protocol, 1-MCP was reapplied once at 38 days or twice at 38 and 68 days cold storage as follows: (I) 0.42 mmol m 3 at harvest + 0.42 mmol m 3 at 38 days; (II) 0.42 mmol m 3 at harvest + 4.2 mmol m 3 at 38 days; (III) 0.42 mmol m 3 at harvest + 0.42 mmol m 3 at 38 days + 42 mmol m 3 at 68 days; (IV) 0.42 mmol m 3 at harvest + 4.2 mmol m 3 at 38 days + 42 mmol m 3 at 68 days. Fruit at 0.5 C were exposed to 1-MCP for 24 h in a 250 L steel container with a steel lid sealed by a water moat. 1-MCP was generated at 20 C from EthylBloc1 powder and buffer solution (BioTechnology for Horticulture Inc., Burr Ridge, IL) in a sealed 5.1 L glass bottle and then pumped from the mixing bottle into the steel container for 15 min in a closed loop. Headspace concentration of 1-MCP in the treatment chamber was analyzed using a HP 5880 gas chromatograph (Hewlett Packard, Palo Alto, CA) using 1-butene (Scott, Plumsteadville, PA) as an external standard. The GC column was a CP Porabond Q, 0.32 mm i.d. 10 m length (Varian, Lake Forest, CA). He carrier gas linear velocity was 40 cm s 1, H2 and air flows were 0.42 and 5 mL s 1, respectively. The injector and detector temperatures were 60 and 150 C, respectively. The analysis was conducted with an oven temperature program with an initial temperature of 50 C increasing to 150 C at 0.42 C s 1.
Fruit maturity and quality were individually evaluated at harvest and after 60, 120 or 180 days storage plus 1 and 7 days at 20 C. Flesh firmness was measured on two pared surfaces per fruit using a penetrometer with an 8 mm tip (Lake City Technical, Kelowna, BC, Canada). TA was determined by titrating 10 mL of juice with 0.1 M KOH to pH 8.2 using an autotitrator (Radiometer, Copenhagen, Denmark). Soluble solids content (SSC) in juice sample was measure using an Atago N1 refractometer (Atago, Tokyo). Starch score was determined visually using a 1–6 scale (1 = full, 6 = no starch) after staining an equatorial section of each pear with a 5 mg L 1 I-KI solution. Color on a disorder free area of peel was recorded as CIE L*a*b* with a chromameter (Model CR200, Minolta, Japan) using CIE illuminant C and an 8-mm measuring aperture. Hue was calculated from a* and b* (Hunter and Harold, 1987). Superficial scald was visually assessed using a scale from 1 to 7 with consideration of both severity and areas of surface affected: 1, no scald; 2, light scald, <33% of the surface area affected; 3, light scald, 33–66% of surface affected; 4; light scald, >66% of surface affected; 5, dark scald, <33% of the surface area affected; 6, dark scald, 33–66% of surface affected; 7, dark scald, >66% of surface affected. Incidence of senescent scald, core browning and decay were rated as absent (1) or present (2). Superficial and senescent scald were differentiated based on symptom appearance (Pierson et al., 1971). Rates of ethylene production and respiration were assessed in four replicates of five pears per treatment, enclosed in 20 L plexiglass chambers, maintained at 20 C and supplied with compressed, ethylene-free air at 100 mL min 1. Gas samples of 0.5 mL were collected from effluent air of each chamber for CO2 and ethylene analysis. The concentration of CO2 was determined by a gas chromatograph (HP5890; Hewlett-Packard, Palo Alto, CA) equipped with a methanizer (John T. Booker, Austin, TX), flame ionization detector and a 0.6 m stainless steel column (2 mm i.d.) packed with 80–100 mesh Porapak Q (Supelco, Bellefonte, PA). Oven, detector, methanizer and injection temperatures were 50, 200, 290 and 150 C, respectively. Gas flows for N2, H2 and air were 1.2, 0.5 and 5 mL s 1, respectively. Analyses of ethylene concentration in gas sample was determined by a gas chromatograph (HP 5880A; Hewlett-Packard) equipped with a flame ionization detector and a 0.3 m glass column (3.2 mm i.d.) packed with 80– 100 mesh Porapak Q (Supelco, Bellefonte, PA). Oven, injector and detector temperatures were 60, 60 and 150 C, respectively. N2, H2 and air flows were 0.5, 0.5 and 5 mL s 1, respectively. There were 40 single fruit replications per treatment for quality assessments. Data were subjected to analysis of variance using SAS (SAS Institute, Cary, NC). Treatment mean separations were determined by Fischer’s least significance (a = 0.05). 3. Results 3.1. Year one At harvest, ‘Bartlett’ pears had flesh firmness 86.5 6.9N (SDV), starch index 1.1 0.1, soluble solids 11.0 0.5% and peel Hue 115 0.9. Increased ethylene production, fruit softening, yellowing (decreased Hue) and loss of acidity exhibited by control fruit were delayed by 1-MCP treatment at 4.2 or 42 mmol m 3 but not at 0.42 mmol m 3 (Fig. 1). Maximum ethylene production was similar regardless of treatment. Effects of 4.2 and 42 mmol m 3 1-MCP treatments on ethylene production, firmness, titratable acidity and Hue were similar through 60 days storage plus 7 days at 20 C. However, fruit treated with 42 mmol m 3 had lower ethylene production and higher firmness and titratable acidity after 120 days plus 7 days at 20 C compared with fruit treated with
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Fig. 1. Ethylene production and quality of ‘Bartlett’ pear fruit at harvest and following cold storage plus 7 days at 20 C. Fruit were treated at harvest with 0.42, 4.2 or 42 mmol m 3 1-MCP. Controls and fruit treated with 0.42 or 4.2 mmol m 3 1MCP severely affected by senescent scald and/or decay were not analyzed after 180 days storage. Inside vertical bars or numbers indicates LSD0.05 for each days of storage. Data from year one.
4.2 mmol m 3. A high incidence of disorders for controls and fruit treated with 0.42 or 4.2 mmol m 3 prevented assessment after 180 days. The impact of 1-MCP on development of physiological disorders was also dependent on treatment concentration and storage duration (Table 1). Superficial scald was detected only after 180 days in storage, while senescent scald was visible on fruit assessed after 120 and 180 days. 1-MCP applied at 42 mmol m 3 prevented the development of superficial scald and senescent scald through 180 days in storage but 0.42 mmol m 3 had no effect on disorder development. 1-MCP applied at 4.2 mmol m 3 prevented the development of superficial and senescent scald after 120 days storage, but it reduced only slightly the development of superficial scald and senescent scald after 180 days storage. Development of severe senescent scald prevented assessment of superficial scald after 7 days at 20 C. Fruit treated with 1-MCP at 4.2 or 42 mmol m 3 were less affected by decay after 180 days storage compared with controls or fruit treated with 0.42 mmol m 3 1-MCP. Core browning was not detected on any fruit during year one. 3.2. Year two At harvest, ‘Bartlett’ pears had flesh firmness of 111.4 8.4 N (SDV), starch index of 1.4 0.6, 10.5 0.9% SSC and 116 0.9 Hue.
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Production of CO2 and ethylene by control fruit increased during 7 days at 20 C after harvest and following 15–120 days of cold storage (Fig. 2). The increase in CO2 and ethylene production by control fruit held at 20 C right after harvest was less than that of fruit chilled for 15 days or more. All 1-MCP treatment concentrations delayed the increase in ethylene production and respiration rate relative to controls. However, the duration of the 1-MCP effect was greatest for the highest treatment concentration (42 mmol m 3). Fruit treated with 0.42 or 42 mmol m 3 1-MCP at harvest had rates of ethylene and CO2 evolution following 120 or 180 days, respectively, similar to those of controls following 60 days. High incidence of physiological disorders in controls and fruit treated only at harvest with 0.42 mmol m 3 1-MCP or retreated once with 0.42 mmol m 3 after 38 days in storage prevented determination of respiration, ethylene production and fruit quality after 180 days cold storage (Table 2) . Respiration and ethylene production rates by fruit treated with 0.42 mmol m 3 1-MCP at harvest were additionally reduced by 1MCP retreatments during storage depending on 1-MCP reapplication doses and how many times 1-MCP was reapplied. Fruit retreated once with 0.42 mmol m 3 after 38 days in storage had CO2 and ethylene production, after 120 days storage, similar to that of fruit treated only at harvest with 0.42 mmol m 3. However, fruit retreated with 4.2 mmol m 3 after 38 days and 42 mmol m 3 after 68 days in storage had lower respiration and ethylene production, after 120 days storage, compared with fruit treated only at harvest with 0.42 mmol m 3 and similar respiration and ethylene production, after 120 and 180 days storage, to fruit treated only at harvest with 42 mmol m 3 1-MCP. Fruit retreated once with 4.2 mmol m 3 1-MCP after 38 days in storage had similar respiration but lower ethylene production after 60 and 120 days storage compared with fruit treated only at harvest with 0.42 mmol m 3. After the reapplication on day 68 with 42 mmol m 3, ethylene production was higher after 120 and 180 days for fruit retreated on day 38 with 0.42 mmol m 3 compared with 4.2 mmol m 3. Control fruit softened, yellowed (decreased Hue) and lost TA during the first 60 days in storage plus 7 days at 20 C (Fig. 3). Fruit treated with 1-MCP were significantly firmer, greener (higher hue value), and had higher TA compared with control fruit after 60 days. Only exposure to the highest 1-MCP concentration (42 mmol m 3) at harvest resulted in firmer and greener fruit after 120 days of cold storage plus 7 days ripening compared with controls and fruit exposed at harvest to 0.42 mmol m 3. The response to 0.42 mmol m 3 1-MCP applied at harvest was similar to that of fruit retreated once with 0.42 mmol m 3 after 38 days in storage. In contrast, the period over which ripening was slowed in fruit treated at harvest with 0.42 mmol m 3 1-MCP was extended by retreatment at 4.2 and 42 mmol m 3. Fruit retreated with 3 4.2 mmol m 1-MCP after 38 days and 42 mmol m 3 after 68 days in storage had higher firmness, TA and peel hue, and developed less core browning, after 120 days storage, than fruit treated only at
Table 1 Physiological disorders and decay of ‘Bartlett’ pear after 120 and 180 days of cold storage. Fruit were treated at harvest with 1-MCP at 0 (control), 0.42, 4.2 or 42 mmol m Data from year one. Dose of 1-MCP (mmol m 3) 0 (control) 0.42 4.2 42 LSD0.05 a b
Superficial scald (1–7)a
Senescent scald (1–2)b
Decay (1–2)b
120 days
180 days
120 days
180 days
120 days
180 days
1.0 1.0 1.0 1.0 –
6.7 6.2 4.0 1.0 1.1
1.8 1.6 1.0 1.0 0.35
2.0 1.9 1.6 1.0 0.1
1.0 1.0 1.0 1.0 0
1.6 1.6 1.0 1.2 0.3
Superficial scald was visually assessed after 1 day at 20 C using a scale from 1 (no scald) to 7 (dark scald and >60% of the fruit surface affected). Senescent scald and decay were visually assessed after 7 days at 20 C as clear (1) or affected (2).
3
.
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Fig. 2. Ethylene production and respiration rates of ‘Bartlett’ pear fruit during 7 days ripening at 20 C following 0–180 days cold storage. Fruit were treated at harvest (h) with 1-MCP at 0 (control), 0.42 or 42 mmol m 3, or treated at harvest with 0.42 mmol m 3 1-MCP and then retreated once with 0.42 or 4.2 mmol m 3 1-MCP after 38 days in storage (1-MCP 0.42(h) + 0.42(38d) and 1-MCP 0.42(h) + 4.2(38d)) or twice with 0.42 or 4.2 and 42 mmol m 3 1-MCP, after 38 and 68 days in storage, respectively (1-MCP 0.42(h) + 0.42(38d) + 42(68d) and 1-MCP 0.42(h) +4.2(38d) + 42(68d)). Controls and fruit treated with 0.42(h) or 0.42(h) + 0.42(38d) mmol m 3 1-MCP severely affected by senescent scald were not analyzed after 180 days storage plus 7 days at 20 C. Inside numbers indicate LSD0.05 for significant treatment days interaction. Data from year two.
harvest with 0.42 mmol m 3. After 180 days storage, fruit retreated with 4.2 mmol m 3 1-MCP after 38 days and 42 mmol m 3 after 68 days in storage had similar firmness, TA, peel hue, and severity of superficial scald, senescent scald and core browning to fruit treated only at harvest with 42 mmol m 3. The retreatment with 0.42 and 42 mmol m 3, after 38 and 68 days in storage, respectively, also improved retention of fruit quality in comparison to 0.42 mmol m 3 applied only at harvest. However, these retreatments were less effective for firmness retention and prevention of physiological disorders after 180 days storage compared with retreatment with 4.2 and 42 mmol m 3 applied at 38 and 68 days, respectively. After 60 days, fruit retreated once with 4.2 mmol m 3 1-MCP after 38 days in storage had similar TA but higher firmness and hue than fruit treated only at harvest with 0.42 mmol m 3 1-MCP. However, after 120 days, fruit retreated once with 4.2 mmol m 3 1MCP had firmness, TA peel hue and severity of physiological disorders similar to those of fruit treated only at harvest with 0.42 mmol m 3 1-MCP, but higher firmness and TA and less physiological disorders than control fruit. Fruit treated at harvest with 42 mmol m 3 1-MCP and fruit retreated twice with 1-MCP (0.42 mmol m 3 at harvest + 4.2 mmol
m 3 after 38 days + 42 mmol m 3 after 68 days in storage) had, after 180 days storage, peel yellow color, TA and SSC similar to, but firmness higher than control fruit stored 60 days. However, controls were not affected by physiological disorders after 60 days storage while few symptoms of physiological disorders were detected, after 180 days of storage, on fruit treated at harvest with 42 mmol m 3 1-MCP and/or retreated twice with 1-MCP. Physiological disorders were not detected after 7 days ripening, following 60 days of storage on fruit of any treatment, in both years. 4. Discussion Results herein confirm 1-MCP delays ‘Bartlett’ pear ripening making its use a potentially effective method to extend the marketing season while reducing fruit deterioration. However, the delayed ripening and prevention of physiological disorders and decay following 1-MCP application can be associated with unpredictable ripening after removal from storage (Argenta et al., 2003; Chen and Spotts, 2005; Bai et al., 2006; Chiriboga et al., 2013). The effects of 1-MCP are not readily reversed by exposing 1-MCP treated fruit to ethylene (Argenta et al., 2003;
Table 2 Physiological disorders of ‘Bartlett’ pear after 120 and 180 days of cold storage. Fruit were treated at harvest (h) with 1-MCP at 0 (control), 0.42 or 42 mmol m 3, or treated at harvest with 1-MCP at 0.42 mmol m 3 and then retreated once with 1-MCP at 4.2 mmol m 3 after 38 days in storage (1-MCP 0.42(h) + 4.2(38d)) or twice with 1-MCP, at 4.2 and 42 mmol m 3 after 38 and 68 days in storage, respectively (1-MCP 0.42(h) + 4.2(38d) + 42(68d)). Data from year two. Treatment (mmol m 3) Control 1-MCP 0.42(h) 1-MCP 42(h) 1-MCP 0.42(h) + 4.2(38d) 1-MCP 0.42(h) + 4.2(38d) + 42(68d) LSD0.05 a b
Superficial scald (1–7)a
Senescent scald (1–2)b
Core browning (1–2)b
180 days
120 days
180 days
120 days
180 days
6.6 6.1 1.0 3.0 1.5 0.96
1.2 1.1 1.0 1.0 1.0 0.21
2.0 1.9 1.1 1.6 1.0 0.19
1.6 1.4 1.0 1.2 1.0 0.23
2.0 2.0 1.3 1.9 1.3 0.26
Superficial scald was visually assessed after 1 day at 20 C using a scale from 1 (no scald) to 7 (dark scald and >60% of the fruit surface affected). Senescent scald and decay were visually assessed after 7 days at 20 C as clear (1) or affected (2).
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42h 0.42h +4.238d +4268d 0.42h +0.4238d +4268d 0.42h +4.238d h 38d 0.42 +0.42 h 0.42 Control
110
80
Hue
Firmness (N)
100
60
100
40 90
20
11 0.3
SSC (%)
TA (%)
0.4
10
0
60
120
180 0
60
120
180
Days in storage Fig. 3. Firmness, titratable acidity (TA), peel color (hue value) and soluble solids content (SSC) of ‘Bartlett’ pear fruit at harvest and following cold storage plus 7 days at 20 C. Fruit were treated at harvest (h) with 1-MCP at 0 (control), 0.42 or 42 mmol m 3, or treated at harvest with 0.42 mmol m 3 1-MCP and then retreated once with 0.42 or 4.2 mmol m 3 1-MCP, after 38 days in storage (1-MCP 0.42(h) + 0.42(38d) and 1-MCP 0.42(h) + 4.2(38d)) or twice with 0.42 or 4.2 and 42 mmol m 3 1-MCP, after 38 and 68 days in storage, respectively (1-MCP 0.42(h) + 0.42(38d) + 42(68d) and 1-MCP 0.42(h) + 4.2(38d) + 42(68d)). Controls and fruit treated with 0.42(h) or 0.42(h) + 0.42(38d) mmol m 3 1-MCP severely affected by senescent scald were not analyzed after 180 days storage plus 7 days at 20 C. Inside vertical bars indicates LSD0.05 for each days of storage. Data from year two.
Trinchero et al., 2004) and ‘Bartlett’ pear fruit must ripen to a yellow color and soft and juicy texture to have market acceptance (Kappel et al., 1995). Therefore, an effective protocol that assures 1MCP treated pear fruit will ripen after transport and marketing is a commercial necessity. Identification of 1-MCP concentrations for each pear cultivar and storage period has been one means to avoid excessive 1-MCP inhibition of fruit ripening. The winter pear cultivar ‘d’Anjou’ is very sensitive to 1-MCP and requires lower 1-MCP concentrations to extend the storage potential compared with ‘Bartlett’ (Bai et al., 2006). Concentrations of 4.2–12.6 mmol m 3 for short-term (60– 90 days) and 16.8–25.2 mmol m 3 for long-term storage (90– 140 days) allow Bartlett pear fruit to ripen within a reasonable time after removal from storage (Calvo, 2003; Ekman et al., 2004). However, interactive effects of 1-MCP concentration, fruit maturity at harvest and storage period alter fruit response to 1-MCP (Calvo, 2003). In the present study, ripening of fruit with firmness of 111 N and 86.5 N at harvest in two years was and was not, respectively, delayed by treatment with 0.42 mmol m 3 1-MCP at harvest. Lateharvest ‘Williams’ pears require higher 1-MCP concentrations to maintain fruit firmness, acidity and green color than early-harvest fruit (Calvo, 2003). The long-term ripening inhibition of ‘Bartlett’ pears by 1-MCP can be modulated by delaying 1-MCP treatment after harvest (DeEll and Ehsani-Moghaddam, 2011) and temperature management both prior to 1-MCP treatment (Wang and Sugar, 2015) and after storage (Bai et al., 2006). Multiple applications of 1-MCP at low concentrations have been suggested as a mean to extend effects of 1-MCP for long periods while keeping the ability of fruit
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to ripening after short periods of storage (Mattheis et al., 2000; Mitcham et al., 2001). In this study, Bartlett pear fruit treated at harvest with a low 1-MCP concentration (0.42 mmol m 3) and then retreated twice with 4.2 and 42 mmol m 3 after 38 and 68 days of cold storage, respectively, had quality similar to that of fruit treated at harvest with 1-MCP at high concentration (42 mmol m 3), after 120 and 180 days in storage. The single 1-MCP reapplication after 38 days storage, when fruit attained ability to produce ethylene at 0.018 hmol kg 1 s 1 (within 7 days at 20 C), was more effective at concentration of 4.2 than at 0.42 mmol m 3, to delay ripening and prevent disorders after 120 and 180 days storage. Similarly, the second reapplication with 42 mmol m 3, after 68 days of storage, was less effective on fruit that had attained ability to produce 0.2 hmol kg 1 s 1 of ethylene than on fruit that had attained ability to produce 0.05 hmol kg 1 s 1 (within 7 days at 20 C). The reduction of 42 mmol m 3 1-MCP reapplication efficacy as fruit ethylene production increased is consistent with Ekman et al. (2004). Retreatment of ‘Conference’ and ‘Abbé Fétel’ pear fruit with low concentrations of 1-MCP (1.05 and 2.1 mmol m 3) after every 60 days of cold storage had little additional effect to 1-MCP applied at harvest (Eccher Zerbini et al., 2005; Rizzolo et al., 2005). Efficacy of 1-MCP retreatment therefore appears to depend in part on the state of fruit ripening capacity as assessed by monitoring of fruit ethylene production. The rate of fruit ripening during storage is affected by 1-MCP concentration applied at harvest and by fruit maturity at harvest as well as by other factors such as season and production region. It has been hypothesized that the conformation of the ethylene receptor is altered by the binding of agonists (ethylene) or antagonists (1-MCP) with agonist binding promoting ethylene responses following its dissociation from receptors while antagonist remains bound preventing ethylene action (Sisler and Serek 1997; Sisler, 2006). Similarly, Binder and Bleecker (2003) proposed that 1-MCP suppresses the ethylene response pathway by locking permanently the receptor in an active (inhibiting) confirmation. The long period of ripening inhibition of pear fruit from a single 24 h exposure to 42 mmol m 3 1-MCP and subsequent fruit insensitivity to exogenous ethylene (Argenta et al., 2003; Trinchero et al., 2004) support strong, perhaps irreversible, interaction between 1-MCP and ethylene receptors in European pear fruit. Transitory ripening inhibition following 1-MCP application at low (0.42 mmol m 3) concentration has been suggested to result from regeneration of ethylene receptors (Sisler and Serek, 1997; Pirrung et al., 2008; Sisler, 2006). Degradation of ethylene receptors is also a mechanism governing ethylene biosynthesis and perception (McClellan and Chang, 2008). Ethylene receptor gene expression patterns characterized during ripening after 1-MCP treatment indicate differential duration of 1-MCP effects in apple and peach fruit are related to differences in ratio, expression patterns and/or turnover of ethylene receptors (Dal Cin et al., 2006). Expression of ethylene receptor genes in apple fruit are induced at the transcriptional level during maturation and ripening and delayed by 1-MCP treatment although with different patterns depending on receptor homologs and fruit cultivar (Wiersma et al., 2007; Tatsuki et al., 2009; Varanasi et al., 2013; Yang et al., 2013). Increased expression of ethylene receptor transcripts during cold storage and/or ripening has also been demonstrated for pear fruit (El-Sharkawy et al., 2003; Chiriboga et al., 2013) with 1-MCP treatment causing delay, suppression, or stimulation of specific ethylene receptor genes in ‘Conference’ pears (Chiriboga et al., 2013). While the regulation of ethylene-sensitivity in 1-MCP treated pears appears complex, the identification of bio-markers related to resumption of ripening by 1-MCP treated fruit may enable more efficient postharvest management of 1-MCP treated pear fruit.
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