(See Figure 33 Cooling room for mangoes).

Figure 33. Cooling room for mangoes.

Storage of mangoes

Pinhead-sized black spotting is not a defect but is a characteristic of some varieties (Haden).  Avoid mangoes that are wilted, have greyish discoloration of the skin or are pitting.  Some varieties will yield to gentle pressure when ripe.  Most varieties will turn yellow as they ripen, except for green varieties.  Red mangoes will not become redder after harvest.  Area around the stem should look plump and round when the mango is ripe.  Mangoes are susceptible to chilling injury. The handling and storage must be at 12.8°C and relative humidity of 85 to 90 percent. The typical shelf life is of 7 to 14 days.

Pre-treatments

Forced ripening

Fruit may require ripening at the packinghouse to satisfy importer requirements. Mangoes are triggered to ripen by Ethylene injected into the atmosphere around the fruit. Temperature then controls the rate of ripening. Conditions for controlled ripening are: ethylene (1 day) shot method with 200 ppm injected twice or by the trickle method with 10 ppm continuously at 18 to 22°C and 85 to 90 percent relative humidity.

Following the ethylene treatment, store the fruit at 18 to 22°C until it is ready for transport to the export dispatch port. Avoid temperatures higher than 25°C. At high temperatures, the flesh will soften but the skin colour will not change completely from green to yellow. Fruit rots are also severe at high temperatures. The temperature regime required to partly ripen the fruit depends on the time lag before transport.

In India, mangoes are picked quite green to avoid bird damage and the dealers layer them with rice straw in ventilated storage rooms over a period of one week. Quality is improved by controlled temperatures between 15° to 21°C. In ripening trials in Puerto Rico, 'Edward' mango was harvested while deep green, dipped in hot water at 51°C to control anthracnose, sorted as to size, then stored for 15 days at 21°C with relative humidity of 85 percent to 90 percent. Those picked when more than 3 in (7.5 cm) in diameter ripened satisfactorily and were of excellent quality. Ethylene treatment causes green mangoes to develop full colour in 7 to 10 days depending on the degree of maturity, whereas untreated fruits require 10 to 15 days. One of the advantages is that there can be fewer pickings and the fruit colour after treatment is more uniform. Ethylene treatment is a common practice in Israel for ripening fruits for the local market. Some growers in Florida depend on ethylene treatment. Generally, 24 hours of exposure is sufficient if the fruits are picked at the proper stage. It has been determined that mangoes have been picked prematurely if they require more than 48 hours of ethylene treatment and are not fit for market.

Recent experiments in Mexico with Manila mangoes were able to reduce in half the ripening time when mature green mangoes were treated with 500 to 750 ppm ethylene. The fruit ripened homogeneously and attained similar compositional parameters than control mangoes at their edible stage.

Some cultivars, especially 'Bangalora', 'Alphonso', and 'Neelum' in India, have much better keeping quality than others. In Bombay, 'Alphonso' has kept well for 4 weeks at 11.1°C 6 to 7 weeks at 7.2°C. Storage at lower temperatures is detrimental inasmuch as mangoes are very susceptible to chilling injury. Any temperature below 13°C is damaging to 'Kent'. In Florida, this is regarded as the optimum for 2 to 3 weeks storage. The best ripening temperatures are 21.1°C to 23.9 °C (Morton, 1987)

Controlled atmospheres treatment

According to Kader (2000), optimum controlled atmospheres (CA) of mangoes (Kader, 2000) consist of 3 to 5 percent O₂ and 5 to 8 percent CO₂. CA delays ripening and reduces respiration and ethylene production rates.  Post harvest life potential at 13 °C is 2 to 4 weeks in air and 3 to 6 weeks in CA, depending on cultivar and maturity stage. Exposure to CA below 2 percent O₂ and/or above 8 percent CO₂ may induce skin discoloration, greyish flesh colour, and off-flavour development. (Figure 34 AC chamber1 for mango and Figure 35 AC chamber 2 for mango)

Figure 34. AC chamber 1 for mango.

Figure 34. AC chamber 2 for mango.

Coating films

Wrapping fruits individually in heat-shrinkable plastic film has not retarded decay in storage. The only benefit has been 3 percent less weight loss. Coating with paraffin wax or fungicidal wax and storing at 20 to 32°C delays ripening 1 to 2 weeks and prevents shrivelling but interferes with full colour development. Recently a maltodextrin-based coating was able to retard manila mango ripening for three weeks at ambient temperature and exerted limited fly larvae and anthracnose control (Diaz-Sobac et al., 1997)

Irradiation

Gamma irradiation (30 Krad) causes ripening delay of 7 days in mangoes stored at room temperature. The irradiated fruits ripen normally and show no adverse effect on quality. Irradiation has not yet been approved for this purpose.

Refrigerated storage

Cooling

As soon as is practical after harvest, fruit is to be cooled to 13°C, in 85 to 90 per cent relative humidity. The fruit shall be maintained at this temperature for the period before shipping, including the time spent on the orchard; during transport export fruit should not be stored with other ripe or ripening mangoes.