Grapefruit [German version]

Table of contents

General:
Product information
Packaging
Transport
  Container transport
  Cargo securing


Risk factors and loss prevention:
Temperature Odor
Humidity/Moisture Contamination
Ventilation Mechanical influences
Biotic activity Toxicity / Hazards to health
Gases Shrinkage/Shortage
Self-heating / Spontaneous combustion Insect infestation / Diseases




Product information

Product name

German Grapefruits, Pampelmusen
English Grapefruit
French Pamplemousse
Spanish Toronja
Scientific Citrus paradisi
CN/HS number * 0805 40 ff.


(* EU Combined Nomenclature/Harmonized System)



Product description

The grapefruit belongs to the rue family (Rutaceae) and comes originally from Central America.

It is not related botanically to the shaddock, which originates from Malaysia. However, the language of commerce does not distinguish between the shaddock, which is no longer cultivated commercially, and the grapefruit.

The name grapefruit finds its origin in the fact that the fruits grow close together like bunches of grapes.

The grapefruit is a large, yellow-peeled, round citrus fruit weighing approximately 250 - 700 g. Its pulp is very juicy and has a refreshing, aromatic taste. The bitter taste is caused by the glycoside naringin; the amount of this bitter substance present varies according to variety and place of origin. Grapefruit from the tropics generally have a sweeter, less sharp flavor than those from cooler regions of cultivation. The "Ruby" and "Ruby red" varieties, for example, are red-fleshed, seedless fruits with a reddish tinge to the peel in parts (russeting) and a milder, sweeter flavor than other varieties. In international trade, they are two of the most important varieties.

In addition to grapefruit, the group of citrus fruits, which are mainly cultivated in subtropical regions, also includes lemons, oranges, mandarins, limes and easypeelers.

Citrus fruits are berry fruit consisting of three layers:

the outer yellow/orange peel (exocarp, flavedo), the glands of which exude the essential oils, which produce the typical citrus odor
the whitish mesocarp (albedo)
the endocarp consisting of 8 - 10 segments filled with juice sacs (vesicles)


The degree of ripeness of citrus fruit is determined on the basis of three criteria:

by the ripeness index: this is determined by the Brix value, which is a measure of the sugar/acid ratio of the fruit. According to [7], citrus fruit with a Brix value of between 10 and 16 have good flavor.
by cutting at purchase: freshness is determined by cutting the fruit in half from the stem-end to the opposite end. If the fruit is withered at the stem-end, it must not be shipped.
by peel color: the color of the peel is not necessarily a reliable indicator of ripeness, but its surface gloss is.


Fungicides are diphenyl, orthophenylphenol (OPP) and thiabendazole (TBZ). Diphenyl can be recognized from its naphthalene-like odor. The fungicides primarily prevent blue and green molds, but they do impair flavor and indication of their use is mandatory.


Quality / Duration of storage

Experience has shown that it is the care taken with preparation of the fruit for shipping which very largely determines whether individual batches withstand the rigors of transport. Such preparation for shipping is carried out in packing houses. These include:

Post-ripening of green or unsatisfactorily colored fruit to achieve a salable peel color in ripening rooms.
Removal of dirt, sooty mold, spraying residues and scale insects in washers.
Coating with a layer of wax and treatment with preservatives and marking accordingly.
Grading of the fruits by size (gaging), color and other external features.
Counting, weighing and packing. Marking each package with details of number of fruit, quality class, variety and origin.
Storage until shipment in cold stores.


Photo, washing process

Figure 1


Waxing to prevent loss of aroma and weight is required because the washing process removes the natural wax layer. The film of wax sprayed onto the peel only partially seals the pores so that the fruits are still able to respire.

Various sources state maximum duration of storage as follows:

Origin Temperature Rel. humidity Max. duration of storage Source
not stated 5.5 - 10°C 85 - 90% 12 weeks [1]
not stated 8 - 15°C 85 - 90% 12 weeks [3]
not stated 10 - 14°C 85 - 90% 4 - 12 weeks [5]
California 14 - 16°C 85 - 90% 4 - 6 weeks [20]
California 14 - 16°C 85 - 90% 4 - 6 weeks [39]
Florida 10°C 85 - 90% 4 - 6 weeks [20]
Florida, Jan. - Sept. 10°C 85 - 90% 4 - 6 weeks [39]
Florida, Oct. - Dec. 15.5°C 85 - 90% 4 - 6 weeks [39]
Israel 6 - 9°C 85 - 90% 12 - 16 weeks [20]
South Africa 11°C 85 - 90% 3 - 4 weeks [39]


Where controlled atmosphere transport is used, transport and storage duration may be extended. The following parameters apply in such a case [16]:

Temperature Rel. humidity O2 CO2 Suitability for controlled atmosphere
14.4 - 15.6°C 85 - 90% 3 - 10% 5 - 10% Moderate



Intended use

Grapefruit are mainly eaten fresh as a very popular breakfast fruit, but they are also used in the production of juices, marmalades, salads etc..


Figures

(Click on the individual Figures to enlarge them.)

Photo, grapefruit

Figure 2
Photo, grapefruit

Figure 3
Photo, grapefruit

Figure 4



Countries of origin

This Table shows only a selection of the most important countries of origin and should not be thought of as exhaustive.

Europe Turkey, Spain, Italy, Cyprus
Africa South Africa, North Africa
Asia Israel, China
America Brazil, Argentina, USA, Mexico, Cuba
Australia Australia


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Packaging

Grapefruit are transported in crates (e.g. wire-bound boxes), fruit crates and cartons.

Photo, corrugated board carton

Figure 5



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Transport

Symbols

Symbol, general cargo

General cargo


Temperature-controlled



Means of transport

Ship, aircraft, truck, railroad

Photo, transport

Figure 6



Container transport

Refrigerated container with fresh air supply or controlled atmosphere.


Cargo handling

Because of its impact- and pressure-sensitivity, the fruit has to be handled with appropriate care.

The required refrigeration temperature must always be maintained, even during cargo handling.

In damp weather (rain, snow), the cargo must be protected from moisture, as there is otherwise a risk of premature spoilage.


Stowage factor

2.05 - 2.10 m3/t (corrugated board cartons) [1]
2.55 - 2.83 m3/t (boxes and cartons) [14]


The stowage factor depends very much on weight categories and the packaging units used.


Stowage space requirements

Cool, dry, good ventilation


Segregation

Fiber rope, thin fiber nets, wooden dunnage


Cargo securing

Because of its considerable impact- and pressure-sensitivity, packages of this cargo must be secured in such a way that they are prevented from damaging each other. Spaces between packages or pallets must be filled, to prevent slippage or tipping. By selecting the correct packaging size or cargo unit (area module or area module multiple), holds can be tightly loaded (without spaces).


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Risk factors and loss prevention

RF Temperature

Grapefruit require particular temperature, humidity/moisture and ventilation conditions (SC VII) (storage climate conditions).

A written cooling order must be obtained from the consignor before loading is begun. This order must always be complied with during the entire transport chain. The following Table merely constitutes an estimate of appropriate temperature ranges. Temperatures may deviate from these values, depending on the particular transport conditions.

Designation Temperature range Source
Travel temperature 5.5 - 10°C [1]
10 - 13°C [2]
8 - 15°C [3]
10 - 14°C [5]
Grapefruit from California 14 - 16°C [20]
Grapefruit from Florida 10°C [20]
Grapefruit from Israel 6 - 9°C [20]


Storage and transport temperatures differ considerably in their specific details according to variety and country of origin and are stated as different in the literature (see above). For this reason, it is imperative that the specific travel temperature be indicated in writing by the consignor.

The cargo and holds/containers should be precooled prior to loading.

Depending upon the species and variety, all citrus fruits are highly cold-sensitive. Grapefruit, lemons and limes are more susceptible to chilling damage than are oranges and mandarins, and late-ripening varieties are more temperature-sensitive than early varieties. While oranges can withstand temperatures of 5°C, more temperature-sensitive types should never be shipped below 10°C. Green citrus fruits require higher transport temperatures than do yellow; the higher is the acid content of the fruit, the greater is its cold-sensitivity.

Chilling damage is manifested in citrus fruits in particular by spots on the peel (brown dots on the peel), accompanied by a bitter taste and unpleasant odor, rot and cell wall collapse. The glossiness of the peel is lost and the albedo layer (inner layer of the peel), which is normally white, turns a dark color. When the fruit is divided up, the segments, which have a low juice content, break up and the whole fruit is glassy and soft. The severity of the chilling damage is determined not only by the extent to which the temperature has fallen beneath the limit, but also by the length of exposure to this temperature. In grapefruit there is a risk of chilling damage at temperatures below 6°C. Chilling damage does not generally occur in cold stores, but instead prior to cooling or after leaving the cold stores.

Excessively rapid warming of refrigerated fruit results in condensation and spoilage, and excessively high temperatures render the grapefruit highly impact-sensitive and susceptible to mold.

During loading, pulp temperature measurements must be performed continually. The pulp temperature must never be < 4°C or > 25 - 30°C as storage life and appearance are impaired outside this range. Fruits punctured for pulp temperature measurement must be discarded as they would rapidly spoil and infect the other fruit. The measurements must be recorded.


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RF Humidity/Moisture

Grapefruit require particular temperature, humidity/moisture and ventilation conditions (SC VII) (storage climate conditions).

Designation Humidity/water content Source
Relative humidity 85 - 90% [1]
85 - 90% [3]
85 - 90% [5]
85 - 90% [20]
Water content approx. 87% [1]
Maximum equilibrium moisture content 85% [1]


It is essential to protect grapefruit from moisture (seawater, rain, condensation, snow) as moisture in particular promotes green and blue mold and black rot.

In general, due to the high water content of grapefruit of approx. 87%, a relative humidity of 85 - 90% is required. Only lemons, oranges and mandarins with a dark green peel color are able to withstand a relative humidity of 82 - 85%.


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RF Ventilation

Grapefruit require particular temperature, humidity/moisture and ventilation conditions (SC VII) (storage climate conditions).

Recommended ventilation conditions:

According to [1]: circulating air, 60 - 80 circulations/hour with continuous supply of fresh air

According to [14]: circulating air, 40 - 60 circulations/hour with continuous supply of fresh air

The addition of fresh air is extremely important as citrus fruit can start to ferment within a few hours due to anaerobic respiration (resulting in total loss of the fruit). If ventilation is inadequate, storage damage may occur, taking the form of a bitter flavor and peel scab.


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RF Biotic activity

Grapefruit display 2nd order biotic activity.

They are living organs in which respiration processes predominate, because their supply of new nutrients has been cut off by separation from the parent plant.

Care of the cargo during the voyage must be aimed at controlling respiration processes (release of CO2, water vapor, ethylene and heat) in such a way that the cargo is at the desired stage of ripeness on reaching its destination. Inadequate ventilation may result in fermentation and rotting of the cargo as a result of increased CO2 levels and inadequate supply of atmospheric oxygen (see Ventilation).


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RF Gases

CO2 evolution at 10°C: 13 mg/kg*h
Upper limit of permissible CO2 content 0.1 vol.% [1]

0.3 vol.% [39]
Ethylene evolution  
Active behavior The rate of ethylene production is very low, being below 0.1 µl/kg*h [16].
Passive behavior Grapefruit are moderately sensitive to ethylene [16] and should thus not be stored with goods having an elevated ethylene production rate (allelopathy).


In fresh fruit, metabolic processes continue even after harvesting. The fruit absorbs oxygen (O2) and excretes varying amounts of carbon dioxide (CO2) and ethylene (C2H4) as well as aromatic compounds during the ripening process.

If ventilation has been inadequate (frost) or has failed owing to a defect, life-threatening CO2 concentrations or O2 shortages may arise. Therefore, before anybody enters the hold, it must be ventilated and a gas measurement carried out. The TLV for CO2 concentration is 0.49 vol.%.

Levels of respiratory gases which promote ripening, such as ethylene as well as carbon dioxide, should be kept as low as possible. If ventilation is inadequate, storage damage, such as a bitter flavor and peel scab, may occur. The supply of fresh air must thus be constant in order to dissipate these gases.


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RF Self-heating / Spontaneous combustion

No risk.


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RF Odor

Active behavior Grapefruit have a strong, pleasant odor, this being a typical citrus odor caused by the essential oils in the flavedo layer of the peel. For this reason, they constitute a highly odor-contaminating cargo and must thus not be stowed or stored together with fruit, vegetables and other odor-sensitive foodstuffs. Meat, butter, eggs, fats and cheese are particularly prone to absorbing the citrus odor. Cold stores must therefore be carefully deodorized before different goods are transported on the next voyage. Wooden dunnage tainted with the citrus odor must not be reused for odor-sensitive goods.
Passive behavior Grapefruit are highly odor-sensitive.



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RF Contamination

Active behavior Grapefruit do not cause contamination.
Passive behavior Grapefruit are sensitive to dust, dirt, fats and oils. The holds or containers must accordingly be clean and in a thoroughly hygienic condition before loading.



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RF Mechanical influences

Grapefruit are highly impact- and pressure-sensitive. Spoilage due to mold and rot occurs in particular when the peel of the fruit is injured. Injury to peel occurs in the event of careless harvesting and due to incorrect handling of packages. Such injury may also be a sign of excessively low temperatures or incorrect use of postharvest phytosanitary agents.

Attention must be paid to the level of filling of cartons in order to avoid damage: they should be filled no higher than the top as overfilling will inevitably result in pressure damage, and thus premature spoilage, when the cartons are stacked. Bruises become soft and the squashed peel looks like "goose-pimples". The aroma of the fruit is also lost and the flavor becomes bitter and unpleasant.

Photo, filling level

Figure 7



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RF Toxicity / Hazards to health

If ventilation has been inadequate (frost) or has failed owing to a defect, life-threatening CO2 concentrations or O2 shortages may arise. Therefore, before anybody enters the hold, it must be ventilated and a gas measurement carried out. The TLV for CO2 concentration is 0.49 vol.%.


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RF Shrinkage/Shortage

The normal weight loss due to a reduction in the moisture content of the product is 1 - 2% [1]. 

Losses of volume caused by breakage are less when the cargo is packaged in cartons than when it is packaged in boxes.


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RF Insect infestation / Diseases

Blue mold rot or storage rot is the most feared storage disease of citrus fruits and is caused by two species of mold: green mold (Penicillium digitatum), which is of an olive-green color, and blue mold (Penicillium italicum), which is of a blue-green color. The fungal spores mainly penetrate through small injuries and initially form white, circular spots of fungal growth, which are subsequently covered from the center outwards with a green or blue-green sporulating layer. The peel becomes spongy, the pulp soft - a typical instance of wet rot. Development is optimal at 20 - 27°C; growth still flourishes at 10°C and comes to a standstill only at 4°C. Blue mold is transferred from fruit to fruit by contact.

Seawater, rain and condensation water promote green and blue mold growth.

Drawing, blue mold

Figure 8


Black rot (beginning at flower end) and stem-end rot (beginning at stem-end) are forms of dry rot which may occur as early as during harvest. Moisture promotes blue mold rot and black rot.

The Mediterranean fruit fly (Ceratitis capitata), a quarantine pest, in particular attacks thin-peeled citrus varieties, especially oranges and mandarins. The 8 mm long maggots of this boring fly in particular attack ripening and ripe fruit, causing rotting. Complete destruction of affected fruit and the use of contact insecticides during the flight time are the most effective methods of control. Countries apply strict quarantine measures to prevent introduction of this pest. Import of affected fruit is prohibited. Since these pests have many different food sources (being polyphagous), they can find food throughout the year in the Mediterranean region; in January mandarins are attacked, from February to May early to late oranges, in the summer peaches, apricots and pomaceous fruit and, at the beginning of winter, back to mandarins. Externally visible signs of attack are sunken, soft, black puncture marks and, subsequently, brownish discoloration of the peel. Mites cause sucking injuries to the fruit.

The quarantine regulations of the country of destination must be complied with and a phytosanitary certificate may have to be enclosed with the shipping documents. Information may be obtained from the phytosanitary authorities of the countries concerned.


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