Recent Development in the Preharvest 1-MCP Application to Improve Postharvest Fruit Quality

*Nariane Q. Vilhena, Lourdes Cervera-Chiner, Ana Moreno and Alejandra Salvador*

#### **Abstract**

1-Methylcyclopropene (1-MCP), an ethylene action inhibitor, is routinely applied to fruit as a postharvest treatment prior to cold storage to extend fruit storability and posterior shelf life. Nevertheless, preharvest 1-MCP applied as a liquid spray to trees is a novel treatment for maintaining fruit quality throughout the postharvest in some crops and can be a very useful tool for improving handling operations in packing houses. This chapter aims to provide an overview of not only employing 1-MCP as a preharvest treatment in different crops, but also of its effect on the biochemical and physico-chemical parameters that influence fruit postharvest quality, storage capacity, and chilling injury development. It also intends to address the main factors related to the preharvest 1-MCP application effect, such as application time, optimum concentrations, and its combination with other preharvest treatments.

**Keywords:** 1-methylcyclopropene, Harvista, fruit storage, field treatment, ethylene

#### **1. Introduction**

Ethylene is the simplest natural plant ripening hormone that is involved in the regulation of many growth and development processes of horticultural crops. This hormone acts by linking itself to its action site in the cell to promote a succession of events, such as leaf abscission, fruit maturation, and the ripening process [1–3].

Fruits are generally divided into two categories: climacteric and non-climacteric [4]. It has been clearly established that all fruits produce minimal amounts of ethylene during their development. However, the ripening of climacteric fruit is characterized by an increased respiration rate and a burst of ethylene biosynthesis. Non-climacteric fruits have a different ripening pattern. They do not show a drastic change in respiration rate and the ethylene production remains at a very low level. Climacteric and non-climacteric fruits can be differentiated by not only their pattern of ethylene production during ripening but also by their response to exogenous ethylene.

The postharvest quality of horticultural crops is also influenced by ethylene, whose effect can be beneficial or detrimental depending on a number of factors like fruit type (climacteric or non-climacteric), ripening stage, and intended use [5].

The application of exogenous ethylene is often used to promote uniform ripening in climacteric fruits like bananas or apples [6, 7]. Ethylene is also applied on nonclimacteric fruits to bring about certain different effects, such as accelerating citrus fruits color change (degreening) [8]. However, ethylene can negatively influence the quality of both climacteric and non-climacteric fruits by inducing the development of physiological disorders or accelerating senescence processes, especially during storage and shelf life.

Therefore, many strategies have been studied to control ethylene production or its action during the postharvest life of fruits and vegetables. Of the available methods, 1-methylcyclopropene (1-MCP) is a competitive inhibitor of ethylene perception that prevents ethylene binding and the eliciting of subsequent signal transduction and translation. As a consequence, 1-MCP applied at very low concentrations (0.5–1.0 μL L−1) can delay ripening and senescence events of horticultural products that are mediated by ethylene [9–11].

Postharvest 1-MCP application has become a successful technology for controlling ripening and senescence processes to maintain fruit quality and to reduce different postharvest physiological disorders in many climacteric and non-climacteric horticultural products [9, 12]. 1-MCP is also used as an excellent tool to explore ethylene-mediated responses of plant systems, especially those involved in ripening and senescence processes.

It is known that 1-MCP lowers the highest peak value of respiration and ethylene production and delays their emergence during storage [1]. There are two known systems for regulating ethylene production in higher plants: system-1 and system-2. Auto-inhibitory system-1 functions during normal vegetative growth and is responsible for producing the basal ethylene levels detectable in all tissues in both climacteric and non-climacteric fruits. Autostimulatory system-2 is responsible for the upsurge of ethylene production that occurs during the ripening of climacteric fruits [13, 14]. The transition from system-1 to system-2 is believed to be an important step during fruit ripening [3]. For different fruits, such as apples, bananas, and tomatoes [13, 15, 16], there are reports that the expression of the genes responsible for the transition from system-1 to system-2 can be blocked by postharvest 1-MCP application.

To date, a large amount of information has been acquired about the effect of postharvest treatment with 1-MCP on many fruits and vegetables. Protocols have been developed to optimize the benefits of 1-MCP for different horticultural products because its effect depends on factors like concentration, exposure time, or application time after harvest.

Some commercial names of 1-MCP are EthylBloc®, SmartFresh®, SmartTabs®, and EthylBloc® Sachet, which contain different 1-MCP concentrations. When the product is mixed with water or buffer solution, 1-MCP gas is released to the chambers where it is applied. 1-MCP is used in combination with proper temperature and relative humidity management and can replace or be utilized in combination with controlled atmospheres.

Despite postharvest 1-MCP application being able to present lots of benefits in many fruits and vegetables, preharvest 1-MCP treatment emerges as a novel option, and one that has been tested in several crops with different effects, for example, reducing fruit drop, delaying color development and softening, ethylene production, ripening, maintaining fruit quality throughout the postharvest, and replacing the postharvest treatment in some crops [9, 17, 18].

Preharvest 1-MCP treatments can offer some advantages over conventional postharvest exposure. Besides, treatments allow a more flexible harvesting time to be *Recent Development in the Preharvest 1-MCP Application to Improve Postharvest Fruit Quality DOI: http://dx.doi.org/10.5772/intechopen.109724*

obtained for some apple cultivars and might be a good option because they respond poorly or inconsistently to 1-MCP gas exposure as a postharvest treatment [19, 20].

As the preharvest 1-MCP application is considerably limited, a sprayable formulation has been developed for its utilization that facilitates its field application and is marketed as Harvista® (AgroFresh Solutions Inc., Philadelphia, PA, USA). This product allows 1-MCP to be dissolved in water and applied as a fumigation product. Today, it is the only 1-MCP formulation available for preharvest use purposes.

In some cases like bananas, the preharvest 1-MCP treatment has been tested by submerging the stem of the bunch still attached to trees in 1-MCP aqueous solution [21]. In another study conducted with figs, preharvest treatment was applied through a plastic bag with gaseous 1-MCP [22]. Despite having positive effects, these application modes would be very limited for commercial use.

Relatively few reports exist about the preharvest 1-MCP treatment effect on fruits. Most studies have focused mainly on apples and pears, since Harvista® treatment is authorized for these fruits in some countries. However, the interest generated by this treatment has led to further studies being conducted in recent years to search for a possible benefit on other fruits [23]. This chapter reports a review of the main findings of the preharvest 1-MCP application on different fruits.

#### **2. Climacteric fruit**

Increased respiration in climacteric fruit is associated with autocatalytic ethylene production, which mediates fruit ripening processes [24]. As 1-MCP inhibits ethylene perception, its field application in climacteric fruits affects fruit ripening and senescence processes, mainly by delaying harvest time and prolonging postharvest fruit quality [9]. However, effects vary according to different aspects, such as fruit cultivar, application time, and concentration.

#### **2.1 Apple (***Malus domestica* **Borkh)**

1-MCP is commonly used as a postharvest treatment to prolong apple eating quality by maintaining fruit firmness, crispness, sweetness, acidity, and juiciness of cold-stored fruits. It is a proven effective treatment in many cultivars [25–27]. In recent years, and as a novel application method, numerous studies have been conducted on the effect of 1-MCP applied at preharvest on delaying maturation on trees and to maintain postharvest quality in different scenarios.

Most studies generally suggest that the preharvest 1-MCP treatment positively influences apple quality attributes. The differences observed in fruits response may vary among cultivars, mostly in relation to the ability of some cultivars to rapidly generate new ethylene receptors when fruits remain attached to trees [17, 28, 29].

Recent studies have demonstrated that preharvest 1-MCP can retard the activation of system-2 ethylene biosynthesis in apples [14]. The MdACS1 gene is necessary for system-2 activation during apple climacteric ripening. The molecular mechanisms that control the delay and suppression of the expression of MdACS1 and receptor genes after regular postharvest 1-MCP treatment are not well defined. However, the preharvest 1-MCP application is effective in suppressing its expression in the "Delicious" and "Golden Delicious" varieties, which results in the delayed activation of system-2 ethylene biosynthesis [1, 6, 14].

One effect of 1-MCP applied in the preharvest has been reported on fruit cuticular wax biosynthesis and regulation, composition, and structure for regulating ethylene biosynthesis and signaling [1]. The preharvest 1-MCP application at 150 g hm2 lowers the contents of alcohols, acids, and esters in apple cuticular wax by reducing fruit superficial scald and decay and by maintaining fruit cuticular wax functions, such as disease resistance and water retention, after 1 cold storage month.

The preharvest 1-MCP effect on carbohydrate metabolism in apples has also been studied at harvest and during cold storage. The authors observed that the treatment at 150 g AI ha−1 applied 7 days before harvest inhibited starch degradation, retarded soluble sugar increase, and reduced sucrose, glucose, and fructose in "Starkrimson" apples. This was related to the ethylene regulation of related gene expressions and enzyme activities during cold storage [30].

The combined application of pre- and postharvest 1-MCP treatments has also been evaluated in apples. In this case, Harvista® was applied 10 days before harvest at 60 mg L−1 and, 1 day after harvest, fruits were subjected to the Smartfresh® treatment at 1 μL L−1. This combination resulted in greater fruit firmness retention and longer ethylene suppression in "Golden Delicious" apples throughout cold storage [14]. The preharvest or postharvest 1-MCP treatment application led to different expression patterns of ethylene biosynthesis genes (MdACS3 and MdACS1) and receptor genes, which could result in differential effects by 1-MCP treatments.

A common preharvest treatment for apples is to apply ethephon to accelerate maturity to bring forward the harvest period and to improve color development [31, 32]. However, ethephon application leads to the activation of ethylene autocatalysis in fruit tissues, which is reflected as a drastically shortened harvest period and reduced storability. It can also lead to undesired fruit abscission before harvest and accelerated flesh firmness loss during the commercialization period [30, 33, 34]. Nevertheless in "Anna" apples treated with ethephon (50 ppm), preharvest 1-MCP treatment (1–2 mM) in the mature green stage reduced preharvest abscission and preserved fruit firmness. This treatment also mitigated the adverse influence of ethephon on flesh firmness loss during fruit cold storage at 1°C.

In order to delay fruit ripening and preharvest drop in apple, treatments with naphthaleneacetic acid (NAA), a synthetic auxin, and aminoethoxyvinylglycine (AVG), an inhibitor of ethylene biosynthesis, are applied in some production areas. Comparative studies have been conducted on the application of these treatments and the preharvest 1-MCP application [6]. In this way, sprayable 1-MCP at 396 mg L−1 applied 1 week before harvest to "Golden Delicious" apples had a stronger effect on delayed fruit drop than AVG or NAA [24]. Similarly with "Delicious" apples, the application of 1-MCP 15 or 7 days before harvest at a concentration of 160 or 320 mg L−1 delayed preharvest fruit drop more effectively than AVG or NAA used alone and had a similar effect compared to the fruit to which both AVG and NAA had been applied. In that study, the best results were obtained when 1-MCP was applied 15 days before harvest and the concentration did not affect its efficacy in reducing fruit drop [6].

Scolaro et al. [35] also compared preharvest treatments with 1-MCP or AGV on "Royal Gala" apples. They observed that the 1-MCP application had similar effects to the AVG treatment on delaying fruit ripening and also on decreasing ethylene production, starch degradation, loss of flesh firmness and acidity, epidermal yellowing, soluble solid accumulation, and red color development. The authors concluded that preharvest 1-MCP can be an alternative method to the commonly applied AVG for fruit maturation and harvest management purposes.

#### *Recent Development in the Preharvest 1-MCP Application to Improve Postharvest Fruit Quality DOI: http://dx.doi.org/10.5772/intechopen.109724*

With "Golden Delicious" and "Law Rome" apples, 1-MCP applied 7 days or 1 day before harvest at concentrations between 75 and 155 mg L−1 has also been reported as an effective emergency stop treatment, similarly to NAA, and without the potential loss of firmness caused by NAA [20].

Preharvest 1-MCP application, used as a treatment to reduce the incidence of different disorders during storage, has been reported for some apple cultivars [20, 27, 36, 37]. In "Honeycrisp" apples, preharvest 1-MCP sprays reduced the incidence of both soft scald, a skin disorder characterized by brown lesions, and soggy breakdown, a flesh disorder characterized by brown and soft internal tissue [36]. In "Law Rome" apples, preharvest 1-MCP application also lowered the superficial scald incidence during prolonged cold storage (up to 120 days) [20].

Stem-end flesh browning, another disorder that develops around the shoulders of apples, is frequently manifested in some cultivars during storage. In cv. Gala, postharvest 1-MCP treatment had no effect on this disorder, while the preharvest 1-MCP application significantly reduced it, but did not prevent its development [37].

In "Fuji" apples at harvest, watercore incidence and severity, besides starch pattern indices, were lower in the fruits that underwent the preharvest 1-MCP treatment [27]. This study also evaluated the combined application of preharvest and postharvest 1-MCP treatments on fruit quality and the incidence of disorders. The incidences of flesh greasiness and watercore diminished more when the combination of both treatments was applied than by either treatment alone. Besides, preharvest and postharvest 1-MCP applications contribute to maintain fruit quality attributes during cold storage and at 20°C. The effects of preharvest 1-MCP were more consistent when the interval between spraying and harvest was 10 days compared to its application at 4 days before harvest.

The traditional postharvest 1-MCP treatment has been reported to increase the risk of certain stress-related storage disorders in apples, such as CO2 injury, a physiological disorder that can be manifested externally and/or internally, and both injury type and susceptibility were strongly affected by apple cultivar and growing conditions [38]. A study carried out with the cv. McIntosh and cv. Empire revealed that 40 to 160 mg L−1 of preharvest 1-MCP applied 7 or 11 days before harvest also increased the development of external CO2 injury during storage in a controlled atmosphere.

#### **2.2 Pear (***Pyrus communis* **L.)**

Similarly to apples, in pears the effect of the sprayable preharvest 1-MCP application has been studied mainly on fruit drop, extension of the harvest window, quality maintenance during cold storage, and reduction of the incidence of different disorders [39–41].

Prevention of fruit drop with the preharvest 1-MCP application has been reported in "Santa Maria" pears, but the effect on fields was dose-dependent [40]. The most effective treatment was achieved at 150 and 200 g ha−1. In this cultivar, the ripening period could be prolonged up to 4 weeks.

A similar preharvest 1-MCP treatment effect on fruit drop has been reported for "Barlett" pears [42]. In this study, the 1-MCP application was as effective as NAA in reducing premature fruit drop. 1-MCP significantly delayed ripening immediately after harvest, but this effect diminished after storing fruit at −1°C for 3.5 months. No differences in pear fruit maturity were found between the highest (100 mg L−1) and the lowest (28 mg L−1) applied doses. The strongest 1-MCP effect occurred when fruits were harvested soon after treatment (7 days after application). The 1-MCP preharvest application also lowered internal browning incidence during storage.

A recent study performed with the "Bartlett" and "d 'Anjou" cultivars found that the preharvest 1-MCP treatment extended the harvest window by 3–4 days without reducing the storage potential or eating quality [41]. This treatment also lowered ethylene synthesis and respiration rates, maintained fruit firmness and green color during cold storage, and retarded melting texture development in both cultivars. 1-MCP also reduced the incidence of flesh disorders by alleviating membrane lipid peroxidation, maintaining antioxidant capacity, and enhancing superoxide dismutase, catalase, and ascorbate peroxidase activity in both cultivars.

When combining the effect of the pre- and postharvest 1-MCP treatments on "Barlett" pears, the applications of 160 μL L−1 of Harvista® and 0.15 μL L−1 of Smartfresh® were capable of extending the melting texture life of pears up to 5 months of cold storage [43]. When the effects of Harvista® and Smarfresh® were compared in relation to the fruit firmness maintenance during the cold storage of "Abate Feel" pears, a positive result of both treatments was obtained, but the postharvest application was more effective [44]. The Harvista® application time influenced its effect on fruit firmness, since applying Harvista® 7 days before the commercial harvest time was more effective in maintaining fruit firmness after harvest than when applied before.

In "Chuhwangbae" pears, the preharvest 1-MCP application had no effect on postharvest quality attributes during cold storage and shelf life because most fruit quality attributes and specific targeted metabolites were not affected by preharvest 1-MCP application, but by storage duration [19]. Nevertheless, the sprayable preharvest 1-MCP treatment enhanced the incidence of physiological disorders compared to that of the untreated fruits.

#### **2.3 Persimmon (***Diospyros kaki* **Thunb)**

The postharvest 1-MCP (Smartfresh®) application is routinely performed to allow persimmon cold storage, since it has been widely reported that it reduces flesh firmness loss as the main chilling injury symptom [45, 46]. Nevertheless, very little information is available on the preharvest 1-MCP application effect on persimmon.

In cv. Rojo Brillante, the preharvest 1-MCP application effect has been evaluated on maintaining flesh firmness in two different scenarios: 1) early in the season on the fruit treated with ethephon to advance maturity; and 2) at the end of the season on the fruit destined for cold storage, treated with gibberellic acid to delay fruit ripening [18]. The preharvest 1-MCP treatment (22 g L−1) delayed fruit firmness loss induced by ethephon, extending the harvest window, and proved to be the most effective treatment when 1-MCP was applied 1 day after ethephon treatment. The preharvest 1-MCP application also maintained fruit firmness during the marketing period and applying the postharvest 1-MCP treatment was not necessary. Nevertheless, the preand postharvest 1-MCP combination maintained greater flesh firmness during the commercialization period than the single postharvest application.

In the fruit treated with gibberellic acid at the end of the season, the 1-MCP application performed 3 days before harvest maintained fruit firmness during cold storage to the same extent as the traditional postharvest 1-MCP application [18]. Hence in this situation, replacing the postharvest 1-MCP application with preharvest treatment can be a very useful alternative.

A positive preharvest 1-MCP treatment effect has also been observed on "Fuyu" persimmon [47]. Spraying 150 mg L−1 of 1-MCP in the first commercial harvest week reduced not only premature flesh softening but also the occurrence of the translucent stain disorder at postharvest without altering fruit maturation on trees. Better results were found on fruit harvest 1 day after 1-MCP treatment, when similar efficacy of the pre- or postharvest application on both fruit firmness and the incidence of disorders was observed during storage.

## **2.4 Banana (***Musa spp.***)**

The main postharvest banana losses are due to a short postharvest life, which is the main problem in the banana industry. The postharvest 1-MCP application has been well studied in this fruit to delay the ripening process and maintain postharvest quality [21]. Numerous studies have reported that 1-MCP applied at the 5–500 nL L−1 and 0.1 μL L−1 concentrations delays fruit ripening and skin color change during the postharvest life [48–50].

The postharvest 1-MCP treatment regulates ethylene synthesis by inhibiting the genes that regulate the aminocyclopropane-1-carboxylic acid synthase (ACS) and aminocyclopropane carboxylate oxidase (ACO) enzymes [51, 52]. The inhibition of these enzymes results in reduced fruit softening, which extends green life. Moreover, 1-MCP enhances superoxide dismutase and catalase activities and inhibits peroxidase activity, playing an important role in growth and plant development and disease resistance [11, 53]. It is noteworthy that the postharvest 1-MCP treatment effect depends on different factors such as cultivar, maturity stage, previous ethylene exposures, crop conditions, and the part of the bunch [21].

Negative 1-MCP postharvest application effects have also been reported in bananas such as irregular peel coloration, reduced volatile compound production, and delayed sugar accumulation [21, 50]. 1-MCP treatment in bananas can increase the development of chilling-related disorders, which can be trigged by the inhibition of ethylene production [10, 54]. These negative effects limit its commercial application [11].

To date, very few studies on preharvest 1-MCP applications in bananas exist. Only Manigo et al. [55] has studied the effect of preharvest 1-MCP treatment with "Cavendish" on postharvest fruit quality to identify the best and most cost-efficient application method. Three preharvest 1-MCP application methods have been evaluated: Stalk End Immersion (SEI), where the edge of bunch stalks is immersed in an aqueous solution of 1-MCP; bunch spraying (BS); and the combination of both methods (SEI-BS). In all cases, the applied dose was 400 nL L−1. These treatments had a significant effect on delaying fruit ripening, retarding peel color change and fruit softening, and maintaining visual quality during storage. The fruit treated with 1-MCP by the SEI-BS method displayed lesser accumulated weight loss, and the degree of shriveling and the finger drop incidence were lower compared to the BS and SEI methods followed separately. The combined method is useful for prolonging the banana shelf life up to 19 days.
