2.3 Packinghouse operations

Inspection

After harvesting the fruit should be given a quick rinse with a hose to remove any dust or accidental sap on the skin (this prolongs the life of dips by reducing the source of contamination). As stated earlier, the fruit should be de-sapped.

In a sophisticated Florida operation, harvested fruits are put into tubs of water on trucks in order to wash off the sap that exudes from the stem end. At the packinghouse, the fruits are transferred from the tubs to bins, graded and sized and packed in cartons ("lugs") of 8 to 20 each depending on size. The cartons are made mechanically at the packinghouse and hold 6.35 kg (14 lbs) of fruit. The filled cartons are stacked on pallets and using forklifts placed into refrigerated trucks with temperature set at no less than 12.8°C for transport to distribution centres (Morton, 1987).

Anthracnose and stem end rot (Botryodiplodia theobromae) are the most important post harvest rots found in mangoes. Both develop in ripening fruit, so are not noticed in the grading and packing process. The fruit can be dipped as a precaution against rot. There are two methods for anthracnose, stem and rot control:

a. Hot benomyl dip controls anthracnose and partially controls stem end rot. Fruit should be stored for 12 to 16 hours before dipping to prevent scalding. Rain within 36 hours of harvest increases the risk of scalding. Do not dip fruit treated with oil at de-sapping. Hot benomyl dips should be applied before dimethoate. The fruit is totally submerged for 5 minutes in hot water (52°C) to which 100 g/100l of benomyl 50 percent (Benlate®) has been added. The temperature must be carefully maintained; too high a temperature will damage fruit and too cool will reduce effectiveness. The dip must be constantly agitated to prevent the fungicide settling to the bottom. The dip should be replaced every 3 days or sooner with a fresh batch, if heavy contamination occurs from sap and dirt.

b. Unheated prochloraz can be used as a non-recirculating spray. This is not effective against stem end rot and at present is not approved as a dip. Solution concentration should be 250 ppm. This can be achieved by using 55 ml of Sportak® (45 percent prochloraz) per 100 l of water. Prochloraz is compatible with fenthion and should be mixed with it and applied as a low volume non-recirculating spray. See appropriate fruit fly treatment for application method (Poffley et al., 1988).

Washing

Washing the fruits immediately after harvest is essential, as the sap, which leaks from the stem bums the skin of the fruit making black lesions, which lead to rotting.

Grading

Inspect fruit on a grading table with good lighting. Developing a reputation for quality demands that fruit exported is always of a high standard. Do not pack fruit that is wind-marked, sunburnt, damaged by insects, sap-burnt or mechanically damaged Resist the temptation to put one or two borderline fruit in a tray; importers will use blemished fruit as a reason to reduce the price of the consignment. The simple rule is to send no marked, misshapen or damaged fruit. The fruit are re-checked to ensure quality specifications have been met before being separated into groups for packing by count. Grading should be carried out as soon as possible after harvest and fruit left under ambient conditions to continue ripening or placed at 10° to 12°C for cooling and storage. On arrival in the packing facility, fruit should be washed in water to remove latex and debris and then treated in a 0.05 percent Thiabendazole solution for anthracnose control. Washing, treatment and grading can be carried out using mechanized or manual systems, depending on the volumes of fruits. Grading in each cartoon is required in terms of size, sex (shape) and stage of ripeness. Female and hermaphrodite fruit cannot be mixed in the same carton; all fruits must be of a similar size in each carton resulting in a range of counts and separations must be made for the degree of ripeness. Carton net weight is dependent on the importer, ranging from 3.5 to 5 kg (8 to 11 lbs) and must not be overfilled during packing (DA, 1999).

Fruit should be graded in each carton according to variety, size by weight or diameter (giving a range of "counts" for each shipment) and maturity (firm, green full-mature and half-mature fruit will ripen at different rates and should not be packed in the same carton). Minimum weight and size specifications for the required market should be followed (Tropical seeds, 2001).

Hydrothermic process (rural installations and certification of automatic systems)

EMEX, (Mexican Packers of mangoes for export) has been pursuing the incorporation of better technologies to achieve highest quality in their mangoes for exports. To achieve this improvement EMEX is working on the following projects:

-Project of an Automated System for Hydrothermic Treatment Certification.
-Development of a Quality Assurance Program for Fresh Mexican Mangoes together with particular and educational government institutions.
-Market Studies of Mexican mangoes in the United States.

Hot-Water Immersion

Hot-water immersion consists of submerging the fruit in a hot-water bath at a specific temperature for a specified time, based on the weight of the commodity being treated and the pests that may be present (APHIS, 1993). For perishable food commodities, the mandated probity 9 level of fly control can be achieved by heating the core of the fruit to 43 to 46.7°C with exposure times varying from 35 to 90 minutes. Variations are noted for different commodities, pest species and life stages of insect pests. Hot water is an effective heat transfer medium and, when properly circulated through the load of fruit, quickly establishes a uniform temperature profile (Couey, 1989). Hot-water immersion also has the additional benefit of controlling post harvest microbial diseases such as anthracnose and stem end rot (Couey 1989, McGuire, 1991). Hot-water immersion is currently used to successfully treat mangoes infested with the Mediterranean fruit fly and several different Anastrepha species of fruit fly before importation into the United States from Mexico, the Caribbean and Central and South America (APHIS 1993). Research performed by ARS on mangoes, which are relatively resistant to heat damage, led to approval by USDA-APHIS of hot-water immersion quarantine treatments for mangoes infested with immature fruit flies (Sharp and Picho-Martinez, 1990).

A hot-water immersion system, can be easily assembled; and may be durable, mobile and inexpensive (Sharp, 1989). A hot water immersion is inherently more efficient than vapour heat as a heat transfer medium. (See Figure 29. Hot water immersion)

Figure 29. Hot water immersion.

Hot water immersion is the only approved quarantine treatment for mangoes. More than 75 commercial hot water treatment facilities operate in Mexico, Haiti, Puerto Rico, South America and Florida. The cost for each facility averages about $200,000. Additional facilities are planned or being constructed. APHIS/PPQ (Animal and Plant Health Inspection Service Plant Protection and Quarantine) must certify each facility and ensure that inspectors are on site.

Thermal disinfestation treatments (USDA -APHIS, 2001)
Mango (Kent, Keitt, Tommy, Haden and Ataulfo varieties) from Mexico

Pest: Anastrepha ludens (Mexican fruit fly), Anastrepha obliqua (West Indian fruit fly) and Anastrepha serpentina (black fruit fly)
Treatment consists of 103°C administered in one single-stage high temperature forced air application. Size of fruit will range from standard sizes 8 to 14.
Weight of fruit must not exceed 1½ pounds (700 g).
The steps must occur in the following order:

1. Probe at least three of the largest mangoes at the seed's surface. Insert probes into the thickest portion of the fruit's pulp.
2. Record temperatures at least once every two minutes until the Treatment is concluded.
3. Introduce air heated to 122°F (50°C) in the chamber.
4. Conclude the Treatment once the temperature at the seed's surface (based on the coolest part of the fruit) reaches 118°F (48°C).

IMPORTANT: Treatment time will vary depending on the size of the fruit and the number of boxes treated.

* Such as `Frances,' `Carrot,' `Zill,' `Ataulfo,' `Carabao,' and `Irwin.' ** Such as `Tommy Atkins,' `Kent,' `Hayden,' and `Keitt.'

* Such as `Frances,' `Carrot,' `Zill,' `Ataulfo,' `Carabao,' and `Irwin.' ** Such as `Tommy Atkins,' `Kent,' `Hayden,' and `Keitt.'

* Such as `Frances,' `Carrot,' `Zill,' `Ataulfo,' `Carabao,' and `Irwin.' ** Such as `Tommy Atkins,' `Kent,' `Hayden,' and `Keitt.'

Alternatively, vapour heat and forced hot air treatment systems are less damaging to commodities and more versatile than other treatment systems. Though these treatment systems cause less damage to produce, they are more expensive.

For Mango, Anthracnose caused by the mould Colletotrichium gloesporoides is a main disease causing decay and commercial devaluation of harvested mangoes. Liu (1984) suggested that pathogenic fungi diseases such as anthracnose on mango fruit are latent and a main cause of serious decay. Huang and Yang (1988) demonstrated that a 53°C hot treatment in combination with fungicide could reduce the decay. Mango fruit can be stored at ambient temperatures up to 15 days and at low temperature for about 30 days.

Jiang (1995) demonstrated that the activation of latent pathogenic fungi in mango was related to the development of fruit ripening and chitinase and ß-1, 3-glucanase increased gradually during fruit ripening and pathogenesis. Ji et al. (1994) also made some studies on storage of mango at low temperature and its chilling injury.

Experiments in Florida have demonstrated that 'Irwin', 'Tommy Atkins' and 'Kent' mangoes, held for 3 weeks at a storage temperature of 13°C, 98 percent to 100 percent relative humidity and atmospheric pressure of 76 or 152 mm Hg, ripened thereafter with less decay at 21°C under normal atmospheric pressure, as compared with fruits stored at the same temperature with normal atmospheric pressure, stored at 152mm Hg took 3 to 5 days longer to ripen than those stored at 76mm Hg. Decay rates were 20 percent for 'Tommy Atkins' and 40 percent for 'Irwin' varieties. Spoilage from anthracnose has been reduced by immersion for 15 minutes in water at 51.7°C or for 5 minutes at 55.6°C. Dipping in 500 ppm maleic hydrazide for 1 minute and storing at 32°C also retards decay but not loss of moisture. In South Africa, mangoes are submerged immediately after picking in a suspension of benomyl for 5 minutes at 55° C to control soft brown rot.

In Australia, mature-green 'Kensington Pride' mangoes have been dipped in a 4 percent solution of calcium chloride under reduced pressure (250 mm Hg) and then stored in containers at 25° C in ethylene-free atmosphere. Ripening was retarded by a week; that is, the treated fruits ripened in 20 to 22 days whereas controls ripened in 12 to 14 days. Eating quality was equal except that the calcium-treated fruits had slightly higher ascorbic acid content.

High Temperature Forced Air

Recirculated air that has been heated and humidified can be forced over fruit surfaces to raise the temperature to a level that is lethal to target pest species. Heated air treatments of 40 to 50 °C (usually at four incrementally increased temperatures) for less than eight hours are becoming more common for fruit fly control in tropical commodities (UNEP, 1994). Condensation on fruit surfaces or in the treatment chamber is prevented by keeping the dew-point temperature 2 to 3°C below the dry-bulb temperature throughout the duration of the test. This precise control of temperature and relative humidity is advantageous because it prevents condensation inside the treatment area and on the fruit surface, thus preventing fruit desiccation and scalding (Gaffney and Armstrong, 1990; Sharp et al., 1991). USDA-APHIS has approved forced air treatments for mango (APHIS, 1993). Fruit flies of concern are Mexican fruit fly, West Indian fruit fly and black fruit fly in mango from Mexico (APHIS, 1993).

Packing and packaging materials

Packaging practices (See Figure 30 Packing practices of Tommy Mango)

Experts on Manila variety advise picking of mango at the ripe stage at 120 to 130 days after flower induction. If done at 110 days, mangoes do not develop enough sweetness and shrink as they turn yellow when ripening. Trimming and placing mango's stem-end downward and in-between wooden slots can also prevent damage by latex or the milky liquid. This accelerates latex flow, which may be completed in 30 minutes. Detergents, the researchers said, are good washing agents to prevent latex stain and burns. But hot water treatment along with detergent is more effective against latex damage. In the packinghouse, less strict sorting system can also spell confusion. Extra care is necessary to separate export-grade (160 g and above) from local market-bound mango (DOST, 2001).

Figure 30. Packing practices of Tommy Mango.

Figure 31. Carton packages for Tommy mangoes.

Palletization (See Figure 32. Tommy mango palletization).

Figure 32. Tommy mango palletization.

Containers

Refrigerated containers operate with the refrigerated air supplied across the t-section floor, circulating around the container and returning to the system via the top of the cargo. The "temperature set point" is the temperature entered into the controller or microprocessor, of a temperature controlled container. This determines the air temperatures supplied to the container.

However good the container and however well cooled, packed and stowed the cargo, there is of necessity a temperature gradient within the container, which is dependent on outside conditions. Such gradients are known and understood by container operators and the reason for temperature variations include: effects of ambient temperature, container thermal properties, air circulation rate, air flow patterns, refrigeration control system and loading temperatures.

Integral containers in chilled mode control the air temperatures via the supply air probe. Modern integral units are fitted with dehumidifiers and in-built data-loggers measuring temperatures, relative humidity and events. Digital displays allow visual monitoring of temperatures. The software installed in these integrals also prevents fans from blowing warm, moist air into the container until the refrigeration system has restarted and the evaporator coil has cooled. This helps maintain the integrity of the temperature chain. Air must circulate around the cargo to absorb the small amount of heat that enters the container through the insulated walls, ceiling and floor. It is imperative that cargo is not loaded above the load limit line on the walls, to ensure air circulation occurs. Air must be allowed to flow between the door and the rear cargo stow, which must not extend beyond the end of the t-section floor.

Space (chimneys) must not be left between pallets or cartons, ensuring air does not short circuit back to the refrigeration unit. Gaps must be plugged with dunnage material to ensure that the maximum volume of air flows around the door area. Shippers of very small cartons sometimes cover the floor of the container with a form of hardboard that is covered with pinholes.

Cargo stability is important and shippers must ensure the cargo is well braced before closing the container's doors. Care must be taken when opening containers in case cargo has been displaced, thus creating a safety hazard. Each country has its own maximum load weight regulations, as do the containers; we can advise shippers of the relevant requirements. Shippers must ensure they take full advantage of the available cube space in a container, re-designing the packaging may improve the utilization of available volume and thus reduced transport costs.

Container Preparation

The procedure involves a physical and technical inspection of each unit to make sure the unit performs as required. Cleaning of the container involves removal of any solid matter, using hot water, detergent wash and steam as required. The container needs to be dry before being moved to the stuffing point. Shippers must inspect and accept that each container has been supplied clean and free from odour (P&O Nedlloyd, 2001).

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