VALUE CHAIN #

Onion

The edible onion belongs to the lily family (Liliaceae) and comes originally from Central Asia. The onion (bulb) is composed of a highly compressed basal plate, which gives rise to the roots, and the main shoot apex, around which the thickened onion scale leaves are arranged. These end in the onion neck, from which the above-ground shoot or peduncle emerges. The outermost scale leaves are dry and protect the onion from external influences.
The ripening process starts when the onion bulb proper forms. Bulb formation is determined by day length and varies with the variety of onion.

At postharvest, the onion undergoes a post-ripening process. This post-ripening does not consist merely of the purely physical process of drying of the onions but also of the attainment of a certain physiological stage known as sprout or growth dormancy. During this process, the roots, peduncle and outermost scale leaves dry; the latter change colour and lie tightly around the onion neck, providing protection against evaporation and attack from microorganisms. This process is further assisted by subsequent post-drying.

Quality / Duration of storage
When inspecting the cargo to be loaded, it is essential to pay attention to the following points:

• the onions must not be wet or covered with condensation; instead, they must be dry and parchment-like, which may be discerned from the “lovely rustling sound” the bag makes when lifted.
• the onions must be fully developed and well ripened, they should be round and not flat and must not be soft to the touch.
• the onion neck must be closed and not thick, which would be an indication of inadequate ripeness.
• no peduncle residues must be left on the onions: these must be twisted off, not cut off, as there is otherwise a risk of onion neck rot.
• the roots must be dry and free of soil, which contains rot pathogens.
• the onions should where possible not have sprouted or have done so only slightly, since sprouting is an indication of improper storage and the risk of rot.
• mechanically damaged, squashed onions must always be rejected, as they cause rapid spoilage due to more intense respiration. This effect is also caused by contamination with leaf residues.
• loose-skinned onions are fit for shipping provided that they are dry and not damaged.
• the onions must be sound and free from rodents.

Maximum storage duration is stated as three months.

Where controlled atmosphere transport is used, the transport and storage duration of onions may be extended.

Designation	Temperature	Rel. humidity	O2	CO2	Suitability for controlled atmosphere
Onions, dry	0.6 – 1.7°C	65 – 75%	1 – 2%	0%	good
Onions, green	0.6 – 1.7°C	95 – 100%	2 – 4%	10 – 20%	good

Intended use
Onions are mainly used for seasoning and in cooked dishes and salads. They are also processed to produce powdered onion, onion rings for frying and pickled pearl or cocktail onions.

 

Figures

Figure 1	Figure 2	Figure 3	Figure 4	Figure 5
Figure 6	Figure 7	Figure 8	Figure 9

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	Netherlands, Italy, Poland, Spain, France, Hungary, Turkey, Israel
Africa	Egypt, South Africa
Asia
America	USA, Chile, Argentina, Canada
Australia	Australia, New Zealand, Tasmania

 

 

Packaging
Onions are transported in wide-meshed jute fabric or plastic bags, crates, boxes, cartons, baskets or fruit crates. Small-meshed bags are unsuitable for transport due to their low permeability to air.

Transport

Symbols

General cargo

Temperature-controlled

Means of transport
Ship, aircraft, truck, railroad

Container transport
As chilled goods: refrigerated containers with fresh air supply or controlled atmosphere.
As general cargo: actively ventilated containers, open-sided containers, open-top containers, flat racks(for loading below deck)

Cargo handling
Since onions are highly sensitive to impact and pressure, they must be handled with appropriate care. Damage to onions, caused by setting them down roughly for example, results in greater respiration intensity and self-heating. The required refrigeration temperature must always be maintained, even during cargo handling.

In damp weather (rain, snow), the cargo must be protected from moisture, since this may lead to self-heating, sprouting, root growth and packaging decay.

Storage factor

• 40 m³/t (jute fabric bags, 25 kg)
• 14 – 2.50 m³/t (crates, 27 kg)
• 23 – 2.29 m³/t (cartons and fruit crates)
• 60 – 3.80 m³/t (bags)
• 37 – 3.40 m³/t (bags)

 

Stowage space requirements
Cool, dry, good ventilation, dark (due to risk of sprouting)
Segregation
Fiber rope, thin fiber nets, matting, jute coverings

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).

Risk factors and loss prevention
RF Temperature
Onions 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	2 – 4°C	[1]
	0 – 4°C	[4]
	0°C	[5]

Where journey times are relatively long or a relatively long storage life is desirable, onions must be transported under temperature-controlled conditions. The freezing point of onions lies between -1.59 and -1.90°C. They are able to withstand gentle freezing to -3°C, as they are able to resorb completely the cell water expelled by freezing when they thaw. However, they must not be moved when frozen (risk: rough seas), since this would cause bruises, which lead immediately to rotting. Freezing injury manifests itself in glassiness and watery, grayish tinged spots. The travel temperature should therefore not fall below 0°C.

If the temperature rises from 0°C to 20°C, a rapid increase in respiration intensity ensues. Temperatures of up to 30°C, are admissible in the short term, but from 40°C the onions undergo physiological changes which are known in practice as “scalding” (physiological heat injury) and the symptoms of which include rot, spoilage, sprouting and self-heating. The onions acquire a glassy appearance, become mushy and exude a foul odour.
In the event of an increase in temperature accompanied by an increase in respiration intensity, the essential oils evaporate to a certain degree (increase in odour intensity in the hold), so causing a reduction in the seasoning action of the onions. Since the vitamin content is also reduced, 30°C is considered the maximum admissible temperature.

If the surfaces of a cargo stack cool down too sharply, a wet, rapidly heating, rotting, sprouting boundary layer, which causes the packaging material to decay, may form as a result of a marked difference in temperature relative to the rising heat and water vapor released by the onions from below, leading to total loss of the cargo, while the 0.5 – 1 m thick surface layer appears intact.

RF Humidity/Moisture
Onions require particular temperature, humidity/moisture and ventilation conditions (SC VII) (storage climate conditions).

Designation	Humidity/water content	Source
Relative humidity	75 – 80% at -1 – +1°C	[1]
	70% at 8 – 10°C	[1]
	65% at 15°C	[1]
	65 – 70%	[5]
Water content	82 – 88%	[1]
Maximum equilibrium moisture content	65%	[1]

Onions require a lower, temperature-dependent equilibrium moisture content than other vegetable cargoes with a high water content.
Their particular relative humidity requirements stem from the protective function of the outermost scale leaves, which need to be kept dry. High relative humidity encourage rot, root growth, premature sprouting and self-heating. Since it is not always possible to comply with the values stated above when onions are loaded conventionally without a refrigeration installation, an attempt must be made to get as close as possible to these values using suitable ventilation measures. The temperature must also be lowered to the temperature prevailing at the port of discharge.
During the voyage, onions release large amounts of water vapour. Evaporation losses entail additional losses of essential oils, sugar and vitamins. If the scale leaves of the onions are dry and parchment-like, penetration of microorganisms is largely prevented. Moist scale leaves, on the other hand, lose their resistance and offer favourable living conditions to adherent microbes. The first consignments of onions from a new harvest are more susceptible to injury than warehoused goods due to their higher water content. They must be post-ripened or dried for at least 2 weeks prior to transport (sprout/growth dormancy).

If the holds are washed prior to transport, the tank top ceiling (if present) must be completely dry again before loading (max. water content 15%), as otherwise the cargo may spoil.

RF Ventilation
Onions require particular temperature, humidity/moisture and ventilation conditions (SC VII) (storage climate conditions).
Recommended ventilation conditions: 60 – 80 air circulations/hour with continuous supply of fresh air, the circulating fans being operated constantly at full power. If the onions are transported as standard general cargo rather than as chilled goods, 25 air circulations/h with constant supply of fresh air will suffice. The fresh air supply must be controlled in such a way that the CO₂ content of the circulating hold air does not exceed 0.5 vol.%.
If the onions are stacked too high and ventilation is inadequate, the undissipated intrinsic heat may cause heat injury. Where holds or containers are opened for ventilation purposes, care must be taken to ensure that the onions are protected from the light, to prevent any risk of sprouting.

RF Biotic activity
Onions 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 vapour, 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.
In addition, onions must be protected from light during the voyage, as there is otherwise an increased risk of sprouting.

RF Gases

CO2evolution	Respiration processes may lead to an increased CO2 concentration during storage, associated with a simultaneous O2 shortage. Onions are known to consume large amounts of oxygen, as a result of their high respiration intensity.
Upper limit of permissible CO2content	10 vol.%
Ethylene evolution
Active behavior	The rate of ethylene production is very low, being below 0.1 µl/kg*h [16].
Passive behavior	Dry onions exhibit low sensitivity to ethylene, while green onions are moderately sensitive to it (allelopathy). Onions should not as a rule be loaded together with apples or pears.

An increase in the CO₂ content of the hold air from 0.03 vol.% (i.e. the normal content in inhaled air) to 5 – 10% does not cause any injury to onions. 12 vol.% and above causes the onions to convert to anaerobic respiration, resulting in relatively rapid spoilage.

If ventilation has been inadequate (frost) or has failed owing to a defect, life-threatening CO₂concentrations or O₂ shortages may arise. Therefore, before anybody enters the hold, it must be ventilated and a gas measurement carried out.

RF Self-heating / Spontaneous combustion
Oil content: 0.0037 – 0.055% allyl sulphide (essential oil). The respiration process in onions may give rise to a tendency to self-heating and a high CO₂concentration and high O₂ consumption, resulting in “scalding” (see RF Temperature).

RF Odour

Active behavior	Onions have an unpleasant, pungent odor. An increase in odor levels indicates self-heating, which is associated with the loss of essential oils, sugar and vitamins.
Passive behavior	Onions are highly sensitive to odor-emitting goods and should not be stowed in a hold together with hides, furs, bones or other animal products.

RF Contamination

Active behaviour	Onions produce dust.
Passive behaviour	Onions are sensitive to dirt, fats and oils. They may turn brown, especially if the previous cargo was ammonia (NH3).

RF Mechanical influences
Since onions are highly sensitive to impact and pressure, they must be handled with appropriate care. Damage to onions, caused by setting them down roughly for example, results in greater respiration intensity and self-heating. No more than 12 bags should be stowed on top of one another, as too great a stack height leads to bruising, excessive heating and rot. 12 – 16 bags cause distortion and losses within usual limits, while more than 16 bags should not lie on top of one another. Onions intended for use as seed must not be stacked more than 8 bags high and lower stack heights (6 bags) would be even more favourable.

RF Toxicity / Hazards to health
If ventilation has been inadequate (frost) or has failed owing to a defect, life-threatening CO₂concentrations 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.%.

In marine transport, it is important to inform the crew of the hazardous nature of cargoes of onions. No access is permitted to the holds without breathing apparatus or until they have been ventilated for a long enough period for the normal composition of the air to be re-established and a gas measurement has been carried out using a gas detector.

The following accident provides a telling example of the hazardous nature of cargoes of onions due to CO₂ formation and of the ignorance of those involved:

When a ship containing 5000 bags of onions was to be unloaded, the first dock worker climbed down into the hatch and immediately collapsed unconscious. Exactly the same happened to the second dock worker, when he came to the aid of the first. The ship’s doctor and an officer then climbed into the hold and the ship’s doctor also collapsed unconscious. The officer was able with his last ounce of strength to carry the first unconscious man out. Another member of the crew climbed into the hold and also collapsed unconscious. Only then did someone put on a breathing apparatus, rescue the unconscious men and take them to a hospital, where two people were confirmed dead. An investigation gave as the cause of the accident an excessively high CO₂ concentration in the hold.

 

RF Shrinkage/Shortage
A loss of volume of up to 0.2% of the cargo caused by torn bags may be deemed normal. The risk of decay of the jute bags must be taken into consideration. The normal water content of jute bags is approx. 13.75%; if this is exceeded, they decay quickly and further losses are sustained. Weight loss may also occur due to water vapour release during the voyage.

RF Insect infestation / Diseases

Losses most frequently result from onion neck rot, the cause of which may be found in inadequate post-ripening or post-drying or excessive humidity or inadequate air supply during transport. Onion neck rot is a gray mold rot caused by the fungus Botrytis allii. The fungus enters the onion neck and attacks the fleshy scales. Brown, somewhat sunken spots on the outermost scale leaves, followed by sinking and softening of the head and neck parts are the typical signs of this disease. The flesh of the onion becomes glassy and a layer of gray spores spreads between the onion scales.

The application of thumb pressure to the onion neck allows timely detection of the sunken parts. The mold may still develop even at temperatures of around 0°C.
Bacterial soft rot is another dangerous disease of onions. 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. http://www.tisgdv.de/tis_e/ware/gemuese/zwiebeln/zwiebeln.htm#anfang

 

Cooling and Storage

In order to maintain high quality, bunched green onions should be pre-cooled to <4°C within 4 to 6 hours of harvest. Dry onion bulbs for long-term storage should be pre-cooled to 0°C immediately after drying. Rapid pre-cooling inhibits rooting and sprouting during storage.

Bunched green onions can be stored 3 to 4 weeks at 0°C with 95% to 98% RH. Storage-life decreases to 1 week if the temperature is 5°C, and rapid yellowing and decay of leaves occurs at higher temperatures. Pungent, dry onions can be stored for 6 to 8 months at 0°C with 65% to 75% RH. High RH induces root growth, while high temperature induces sprouting. A combination of high temperature and high RH increases rotting and decreases quality.

After harvest, onion bulbs enter a state of rest for a period of 4 to 6 weeks, depending on cultivar and weather conditions during growth. Maleic hydrazide, a sprouting inhibitor, is often used to prevent root growth and sprouting during long-term storage. It is applied 2 weeks before harvest, when bulbs are mature and 50% of tops are down.

Onions intended for storage should be dried well and cured in the field, under sheds, or in storage. After 2 weeks of field drying, onions can be transferred to storage rooms for final drying and curing. Drying is complete when the onion neck is tight, outer scales are dry and make a rustling noise when touched, and the skin colour is uniform. After drying and curing, the temperature should be lowered gradually to the normal seasonal temperature, or bulbs can be pre-cooled in cold storage at 0°C. In either case, condensation should be avoided as it encourages rot and changes the colour of the dry skin.

For cold storage, onions are usually packed in crates or containers. Air circulation must be sufficient to maintain a constant temperature and remove moisture from inside storage containers. Onions packed in sacks can only be stored for a limited period of time, since air movement through sacks is insufficient to maintain proper storage conditions. Mild and sweet onions can be stored for only 1 to 4 months, even in optimal cold storage. CA may extend the storage period. Onions tolerate storage at 30°C to 35°C for short periods before marketing or processing, but their quality and external colour is less attractive than cold-stored onions.

When stored below -1°C to -2°C, onions should be thawed at 5°C for 1 to 2 weeks before they are removed from storage. Rapid thawing damages onion bulbs. Storage at <-4°C may cause freezing injury, which is manifested by soft, water-soaked fleshy scales and rapid decay after transfer from cold storage to higher temperature, which results in microbial growth. http://www.cargohandbook.com/index.php/Onions

 

Specifications

Parameters	Value
Color	Light and dark red color
Size	30mm and 70mm
Packing	Packed in 5 Kg, 10 Kg, 20 kg, or 25 Kg mesh bag as per customer requirement

http://www.ssexporters.com/onion.html

 

Onion export

Click here https://www.exportersindia.com/indian-suppliers/onions.htm

How are onions stored?

Onions in the field, ready for storage. The processes required to store onions properly. Once they are stored, onions undergo the following processes:

• The drying process: The processes of raising or lowering their temperature
• Conservation or storage proper: These processes are controlled by the Multiserverfrom AgroVentsystems BV.

The onion drying process

The aims of the onion drying process are:

• To remove all of the surface water or moisture from the onion
• To dry three or four layers of the onion skin, therefore sealing the onion
• To dry the stem and therefore also seal this part of the onion (remember that once the stem is cut, it is left open and must be kept as dry as possible.)

 

Well dried onions.

It is best to dry onions at between 25 and 30° Celsius..

 

Multiserver

 

The Multiserver programme for drying onions will ensure that the turbines work the maximum number of hours to extract moisture from the onions as quickly as possible, whilst maintaining the temperature between 25 and 30°C, and the relative humidity between 60% and 65%. In doing so, the aim is not to dehydrate the insides of the bulbs, but rather the 3 or 4 outer layers which separate the bulb from the outside. This process is completely controlled by the Multiserver, which constantly searches for the mixture of air with the highest drying capacity, by managing the doors, turbines, heaters and condensers.

The processes of raising or lowering the temperature of the onions

• Any changes to the temperature of the onions must be gradual and controlled, for two reasons:
• To prevent the cells in the bulb from being destroyed.
• To ensure that the centre of the bulb is at the same temperature as the outer layers.

This is why the Multiserver has two special programmes to control the heating or cooling of the produce.
Onion storage specialists advise cooling or heating the onions by 2 degrees per day at the very most, and recommend only 0.5 degrees per day. Such a slow change in the temperature of the onions has important consequences when planning to move the onions from the storage facility.

Let’s assume that the onions are stored at 2° Celsius.

The destination of the onions is 25° with 85% relative humidity, making the dew point 22.3°. This means that the onions must be heated by at least 20.3°, to 22.3°. At the maximum allowed increase of 2° per day, this process will take at least 10 days. These days must be kept in mind when planning the onion delivery. Especially in hot and humid climates, if the onions are not heated above the dew point, many of them will rot in the humidity.

The onion storage process

• A well-dried onionhas:
  Crispy skin and a juicy middle.
• Before they can be stored, onions must tick the following boxes:
• The onion must be the right variety for storage.
• It must be harvested when it is completely physically ripe.
• The bulb must be firm and compact.
• The skin must be strong.
• The bulb must have a low water content.
• It must be grown to Good Agricultural Practices.
• It must not be fertilised with nitrogen during the last 6 weeks of its growth.
• It must be applied sufficient amounts of aglime.
• Onions can be stored at two ranges of temperatures.
• Between 0 and 4° Celsius
• Between 25 and 31° Celsius

Why these two ranges?

The onion, postharvest, is still alive. This means that it continues to respire. All plants give off water when they respire. The more they respire, the more water they lose, and losing water means losing weight, which is the last thing we want during the storage process.

Below is a graph indicating the relationship between the storage temperature and the intensity of the onion respiration, reflected in the weight (water) loss percentage over 5 months of storage.

 

Onion respiration with relation to storage temperature.
The intensity of onion respiration is reflected in the percentage of weight (water) loss over 5 months of storage, with relation to the storage temperature. There are two ranges in which the onion respires relatively little, and consequently loses less weight:

• Cold storage between 0 and 4° Celsius
• Heat storage between 25 and 31° Celsius

Danger range:

The temperature ranges between 20 and 25° Celsius is very dangerous for the onion. It is inside this range that bacteria and fungi, enemies of the onion, are most active. Below and above this range, they remain inactive.

The graph demonstrates that within the range from 0 to 4° Celsius, weight loss is considerably less than within the range from 25 to 31° Celsius. On top of this, between 0 and 4° Celsius, onions can be kept healthy and suitable for storage for up to 12 months. Between 25 and 31° Celsius, they can be kept healthy and suitable for storage for up to 8 or 9 months.

However, when deciding at which range of temperatures to store your onions, you must bear in mind the local climate during storage time.

Why is this?

1) Temperate climates.

In a climate where the temperature varies between -10° Celsius and 15° Celsius it is much cheaper to cool your storage facility to between 0 and 4° Celsius. Less energy is wasted on keeping it cool.

2) Hot or tropical climates.

In a climate where the temperature fluctuates around 30° Celsius it is much cheaper to heat your storage facility to 25 to 31° Celsius. Less energy is wasted on keeping it at the right temperature. Another consideration is storing onions between 25 and 31° Celsius in the tropics.

Condensation.

As soon as an onion at 2° Celsius is exposed to humid air at 30° Celsius, it becomes moist.

This is what happens if you store onions at between 0 and 4° Celsius in the tropics:

When removing the onions from storage, they must be heated up to the outside temperature. This requires great energy and a lot of time. Meanwhile, onions stored at 30° Celsius can be removed immediately without the risk of moisture.

In both cases:

Relative humidity must be constantly kept between 55% and 65%. The temperature must remain constant; temperature fluctuations must be avoided during storage.

Bulbs must be kept in darkness. Whenever a light is switched on inside the storage facility, the onions in the light (on top of a pile) will react as if they were in direct sunlight, and start to sprout.

Please note: The onion bulb will lose significant weight through respiration (the bulb is still alive) if it is stored between 5 and 25° Celsius. The range between 20 and 25° is particularly dangerous because bacteria and mould thrive at this temperature.

During storage proper, ventilation must be kept to a minimum, because the onions are already dry (dry means dry!) and we do not want them to lose more weight through respiration, no matter how little that may be at this temperature. The little ventilation required is to avoid an increase in CO2 levels, and to eliminate the heat which the onions generate as they continue to respire slowly. https://www.onions-potatoes.com/storage/onions.php

 

Onions Exports by Country

Chopped onions

Global sales from onions exports by country amounted to US$3.1 billion in 2016.
Overall, the value of onions exports were up by an average 20.8% for all exporting countries since 2012 when onions shipments were valued at $2.6 billion. Year over year, the value of global onions exports retreated by -3.1% from 2015 to 2016.
Among continents, Asian countries accounted for the highest dollar worth of exported onions during 2016 with shipments valued at $961.1 million or almost a third (30.9%) of the global total.
In second place were European Union exporters at 30.3% while 22.4% of worldwide onions shipments originated from North America. Smaller percentages came from Africa (8.4%), Latin America excluding Mexico (3.7%) and Oceania (mostly New Zealand and Australia) at 3.3%.
The 6-digit Harmonized Tariff System code is 070310 for onions and shallots. A shallot is a small bulb that resembles an onion. Shallots are used to make pickles or as an onion substitute.

Onions Exports by Country

According to global trading platform Alibaba, the following companies are examples of onions-trading exporters.

• Aalia Gmbh (Germany)
• Agricola Dece SL (Spain)
• BHK Krakow Joint Venture Sp ZOO (Poland)
• Camill Alimentos S/A (United States)
• JDGC (France)
• Jinxiang Luteng Trading Co, Ltd (China)
• Naqshbandi Enterprise (Pakistan)
• Silas Export (Netherlands)
• SMA Trading (Egypt)
• Sri Parvathi Exports (India)

http://www.worldstopexports.com/onions-exports-by-country/