EFFECTS OF CA ON STORAGE FIFE AND QUAFITY OF FRUITS

Table of Contents:

The tolerance of fresh fruits to low О and elevated CO concentrations vary greatly. The tolerance limits can be different at temperatures above or below the recommended for each commodity. Further, a particular commodity can tolerate higher levels of CO or lower levels of О for a short duration. But in general CA storage, supplemented with the optimum low temperature, is widely known to extend the storage-life and maintain the quality of many fruits either tropical or temperature in nature. Under properly maintained CA storage system, the storage life of fruits can be increased (on an average) by one and half to two times from that of its optimum cold storage and 3-4 times compared to ambient storage (Sudhakar Rao et al., 2011)

The main purpose of using CA technology is to extend the marketing period of the commodity during storage, transport, and distribution and to maintain quality and nutritive or market value of the product over that achievable by the use of temperature alone. Therefore, CA should be considered as a supplement to refrigeration for produce maintenance after harvest.

APPLES

CA storage of apples is predominantly used to prolong the storage life by reducing respiration, ethylene production and the associated biochemical and physiological changes. Several factors like cultivar, maturity, О and CO concentrations, length of storage, and timing of CA application influence the storability (Bekele et al., 2016). Apple fruits are susceptible to various flesh browning disorders caused by chilling injury, CO injury or senescence either singly or in combination. Development of flesh browning has become a serious limiting factor for the long term CA storage of “Empire” apple cultivar (Fawbush et al., 2008). Incidence of a flesh browning of “Empire” apples during CA storage at 2°C was increased by treatment of fruit with 1-methylcyclopropene (1-MCP) which is commercially used to maintain quality characteristics such as firmness and acidity (Watkins, 2008). Flesh browning incidence develops earlier in the stem-end than calyx-end region of the fruit. No evidence was detected for close involvement of phenolics and/or PPO and POX activity in the development of flesh browning disorders (Ma et al., 2015).

It has also been previously reported that CA can prolong the impact of 1- methylcyclopropene (1-MCP) on both physical and sensory responses of apple and these two technologies generally are most effective when used in combination (Bai et al., 2005; Rupersinghe et al., 2000; Watkins et al., 2000). However, “Honeycrisp” apples treated with 1-MCP (1 pLL'1) for 24 h at 8-10°C, held for 5 days at 10°C, and then stored at 3°C in CA (3.0 kPa 0+1.5 kPa CO) for 8 months exhibited internal CO injury (DeEll and Ehsani-Moghaddam, 2015). But, sensoiy evaluations revealed that fruit not treated with 1-MCP and stored in air were rated higher for oxidized red apple, earthy flavors while CA-stored apples with 1-MCP were rated the highest for fresh green apple flavor and acid taste.

Hot water dipping (HWD) treatment before longer-term storage, provides an effective control of fungal storage rots (Neofabraea spp, Gloeosporium

spp.) and is now widely used on commercial organic apple orchards in Germany (Neuwald and Kittemann, 2016). “Topaz” apples grown on organic orchards, subjected to HWD treatment for 2 min at 51°C and stored at 1°C in CA (1.0 kPa O, 2.5 kPa CO) for 6 months plus 7 days of shelf-life at 20°C, had less incidence of fungal rots without affecting the fruit quality.

12.2.1.1 D YNAM 1C CON TROL L ED A TMOSPHERE (DCA)

STORAGE

The concept of dynamic controlled atmosphere storage (DCA) involves the reduction of the oxygen concentration in the storage atmosphere close to the lowest level that can be tolerated by the fruit without inducing excessive anaerobic metabolism, which would affect fruit quality. Fruit respiration and thus quality loss during storage is assumed to be slowed down compared to normal ultra-low oxygen (ULO) storage. The safe establishment of very low oxygen levels is possible by monitoring the chlorophyll fluorescence or ethanol concentration on the fruit, or respiratory coefficient (Prange et al., 2011) during oxygen reduction and storage: if oxygen concentrations in storage rooms fall below the critical value, the monitoring will detect the physiological stress of the fruit immediately, allowing the storage room manager to increase the oxygen concentration to a safe level.

A novel type of dynamic controlled atmosphere storage (RQ-DCA) was developed to control О and CO partial pressures in storage containers for apple fruit automatically, based on measurements of the stored fruit respiratory quotient (Bessemans et al., 2016). The RQ-DCA system manages to control О and CO partial pressures in the storage container in an autonomous way. Superficial scald was found to be controlled almost completely in “Granny Smith” apples during storage with RQ-DCA and the effect remained visible during up to 14 days of shelf life.

Torres and Hernandez (2015) assessed superficial scald expression on fruit stored in DCA (for 5-7 months) and then maintained in cold storage for up to 90 days under regular atmosphere (0-1 °C, >90% RH) plus 14 days at 22°C. Commercial DCA did not provide optimum superficial scald control when transferred to air storage. The longer the storage in low temperature under regular atmosphere (RA) after DCA removal, the higher the superficial scald incidence on “Granny Smith” apples, once fruit is exposed to higher temperatures.

Prestorage hot-water treatment did not affect fruit quality and the incidence of physiological disorders of DCA stored apple. Fruit rot was affected by the cultivar, “Topaz” being the most susceptible cultivar and “Ariane” the most resistant to fruit rot. Organic fruit were susceptible to higher fruit rot during DCA-storage than integrated production fruit. Compared to ULO conditions, DCA did not reduce fruit rot (Gasser and Arx, 2015).

Thewes et al. (2017), evaluated the interaction between CA, DCA-CF, and DCA-RQ, with either immediate or delayed atmosphere establishment (30 days of delay) on the quality and volatile profile of “Fuji Suprema” apple after long-term storage. Fruit stored under DCA, regardless the method, had lower ethylene production and higher flesh firmness, both at immediate and delayed atmosphere establishment. DCA-RQ resulted in lower decay incidence when the atmosphere was established immediately. “Fuji Suprema” apple stored in DCA-RQ 2.0 had the highest total ester concentration and the highest volatile compounds that are characteristic to Fuji apples, such as ethyl 2-methyl butanoate, ethyl butanoate, and ethyl hexanoate whereas storage under DCA-CF resulted in the lowest production of volatile compounds.

For most commercial cultivars of apple the optimum CA and temperature reported were 2-3% О and 2-3% CO and 0-3°C (Table 12.1). However, the storage life varied from 4 to 9 months depending on the cultivar.

TABLE 12.1 Optimum Controlled Atmosphere Storage Conditions Standardized for Different Cultivars of Apples.

C'ultivars

Recommended CA

Pre-

storage

treatment

Storage

temperature

(°C)

Storage

life

(months)

References

О

(0/0)

CO(%)

Golden Delicious

2-3

3-5

0-3

6-8

Ryall and Pentzer (1982)

Jonathan

2-3

2-3

0-1

4-6

Ryall and Pentzer (1982)

Topaz

1.0

2.5

HWD for 2 min at 51°C

1

6

Neuwald and Kittemann (2016)

McIntosh

1.5-3

1-5

2—4

5-7

Meheriuk

(1993)

Golden Delicious

3.0

3.0

0

8.5

Truter et al. (1982)

Delicious

3.0

3.0

0

9

El-Shiekh et al. (2002)

Delicious

2.5

2.5

Smart

Fresh

0

8

DeEU et al. (2005)

TABLE 12.1 (Continued)

Cultivars

Recommended CA

Pre-

storage

treatment

Storage

temperature

(°C)

Storage

life

(months)

References

О

(0/0)

CO(%)

Gala

1.5

<0.5

0

9

Jobling et al. (1993)

Cortland

2.5

2.5

0

4-6

DeEll and Murr (2012)

Cortland

2.5

2.0

Smart

Fresh

2-3

6-8

DeEll and Murr (2012)

Cortland

1.5

1.5

0-3

6-7

DeEll and Murr (2012)

APRICOT

CA storage allows stone fruit industries to store fruits like apricot, peaches, and so on for up to 3 months. However, measurable reductions or increase of biochemical components have been noted after 10-15 weeks of storage even in CA. Apricot fruits and peaches can be kept for as long as six weeks by using the optimal CA conditions (10% О and 4% CO at 1°C, 90% RH) while maintaining an excellent quality (total solids, total sugar, total acidity and ascorbic acid) throughout their storage and shelf-life (Temocico et al., 2013)

AVOCADO

Avocado fruits could be stored for 9 weeks at 5°C under 3% О + 8% COwith reduced incidence of chilling injury and after CA storage the fruits ripened normally with typical peel color changes (Meir et al., 1993)

BANANA

The recommended optimum CA conditions varied widely for banana, with oxygen concentrations as low as 2% and CO as high as 10%. Reduced О appeared to be mainly responsible for delaying ripening (Ahmad and Thompson, 2006). Mature green Robusta banana could be kept in unripe condition for 56 days at 15°C and 75 days at 13°C when stored under CA composition of 5% О and 5% or 10% CO and the fruits ripened normally within a week when shifted to ambient conditions (Krishnamurthy et al., 2000 and Sudhakar Rao et al., 2005). CA conditions before the initiation of ripening were beneficial in delaying ripening of banana, with no detrimental effects on subsequent ripening or eating quality of the fruits when they were ripened in air (Williams et al., 2003). CA storage was also found useful in extending the storage life of banana even after they have begun to ripen. Bananas that had been initiated to ripen by exposure to exogenous ethylene then immediately stored in 1% О at 14°C remained firm and green for 28 days but ripened almost immediately when transferred to air at 21°C (Liu, 1976). Post-climacteric use of CA extended the marketable life of banana fruit by 2.3- 3.8-fold, depending on the combination of O/CO used. Overall, 4% О and 4-8% CO, was most effective in extending storage-life (Ahmad and Thompson, 2006) (Fig. 12.1).

Banana (cv. Robusta) fruits stored for 75 days at 13°C under CA conditions of 5% О + 5% CO(CA I) and 5% О +10% CO(CA II)

FIGURE 12.1 Banana (cv. Robusta) fruits stored for 75 days at 13°C under CA conditions of 5% О + 5% CO(CA I) and 5% О +10% CO(CA II).

12.2.5 BLUEBERRY

One of the major factors responsible for the short shelf life of blueberry fruit is the high weight loss that causes shriveling and loss of brightness. Storage trials conducted in early 80’s using CA have indicated that shelf-life extension can be achieved using combinations of elevated CO and reduced О during storage (Ceponis and Cappellini, 1985). 1-MCP (0.3 and 0.6 pi L'1) treatment of blueberries prior to storage in a CA (3 kPa O+ll kPa CO) at 0°C was useful only in controlling the weight loss during 60 days storage period (Chiabrando and Giacalone, 2011).

 
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