Barley
| Infobox on Barley | |
|---|---|
| Example of Barley |  |
| Facts | |
| Origin | This Table shows only a selection of the most important countries of origin and should not be thought of as exhaustive
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| Stowage factor (in m3/t) |
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| Angle of repose | Approx. 25° (average value) |
| Humidity / moisture |
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| Oil content | The oil content of barley is approx. 2%. |
| Ventilation | Recommended ventilation conditions: surface ventilation (see text). |
| Risk factors | An excessively high water content may result in self-heating due to increased respiratory activity. |
Barley
Contents
Description
Barley (Hordeum vulgare) is a type of cereal belonging to the grass family (Gramineae), the term "cereals" covering the grain fruits of cultivated grasses (spikes or ears in the case of wheat, rye, barley and corn; panicles in the case of oats and rice.
Barley is grown mainly in the summer, but also in the winter. Barley ears have awns some 15 cm in length growing from them.
The structure and chemical composition of the grain vary little between the different types of cereal. The cereal grain is a single-seeded indehiscent fruit, the husk of which is formed by the fusion of the fruit and seed walls. It consists of three components:
its cracked husk, which gives the grain a greatly increased surface area relative to its mass. This allows the cereal grain to enter into an active exchange of materials with its environment; the endosperm, which constitutes the main component of the grain and the embryo.
After harvesting, barley usually undergoes further post-ripening, which consists of the high molecular weight substances congregating further with water being expelled (syneresis). As the surface of the cereal then becomes damp because of the elevated water content, this is described as "sweating. In this state, the cereal is highly susceptible to mold and must not as yet be shipped. However, if the water content of the cereal is relatively low (approx. 13 - 14%), proper storage allows the sweat moisture to be absorbed by the air without the risk of mold growth. This sweating process proceeds for a period of approximately 1 - 2 months.
Prior to loading, checks should be carried out by an independent inspector and a certificate provided in relation to loading moisture content, the absence of odor and contamination and the absence of pests.
Excessively damp and incompletely ripened goods may be liable to self-heating, elevated respiratory activity, mold growth and fermentation during transport.
Barley which is "dry for shipment" may be kept for up to 12 months or longer provided that the appropriate temperature, humidity/moisture and ventilation conditions are complied with.
Applications
Winter barley is used primarily as an animal feedstuff while summer barley is mainly used to make malt (sprouted barley grains) for beer and coffee substitute and as a breadstuff.
Shipping/storage
Barley is mainly transported as bulk cargo and only sometimes in bags (seed).
Mainly in bulk containers, but also as bagged cargo (e.g. seed) in standard containers. Compliance with limits for the water content of the cargo and container floor must be ensured.
In damp weather (rain, snow), the cargo must be protected from moisture, since wetting and extremely high relative humidities may lead to mold growth, spoilage and self-heating due to increased respiratory activity.
Suction and blowing devices may cause not inconsiderable damage to the grains.
Grain size
Diameter 1 mm, length 8 mm
Stowage space requirements
Cool, dry, good ventilation.
In the case of maritime transport, the IMO (International Maritime Organization) "Code for Safe Carriage of Grain in Bulk" must be complied with.
When loading an ocean-going vessel with several types of cereal, heavy cereals (wheat, rye, barley, corn) must be stowed in the lower part of the hold and lighter cereals (oats, millet) in the upper part of the hold, for reasons of stability.
Risk factors
Temperature
Barley requires particular temperature, humidity/moisture and ventilation conditions (SC VII) (storage climate conditions).
Favorable travel temperature range: no lower limit - 20°C
Molds reach optimum activity at temperatures of between 20 and 30°C. In addition, at temperatures > 25°C, metabolic processes increase, leading to increased CO2 production and self-heating of the barley.
Humidity/Moisture
- Designation: Humidity/water content
- Relative humidity: 70%
- Water content: 11 - 14%
- Maximum equilibrium moisture content: 70%
Weight loss, germination, self-heating, mold growth and fermentation processes are closely associated with the moisture content and hygroscopicity of the cargo.
Problems of moisture may be prevented by suitable pre-drying of the barley. This is the easiest way of reducing the activity (respiration) of the grain and removing the nutrient medium for mold development and spoilage processes. The necessary level of dryness is approx. 11 - 14% water content, which is at equilibrium with relative humidity of up to 70% at 25°C. The mold growth threshold is reached at a water content of as little as 15% (75% relative humidity). In cold transport regions (North Atlantic in winter), a relative humidity of 70% would be at equilibrium and the barley would not sustain any damage even at that level. At 16 - 17% water content, the sorption isotherm climbs sharply, so meaning that equilibrium moisture contents of > 80% very rapidly produce an excessively damp atmosphere.
Individual clusters of damp product may cause considerable damage to the cargo. The barley in such clusters has a tendency to self-heating. Damp (sweating) barley then appears in the boundary layers, so allowing the process to develop further. Such clusters may form, for example, in too freshly harvested product (not yet post-ripened) or where damp goods have been loaded.
Prior to loading, the loading moisture content should be checked by an independent inspector and a certificate provided. These certificates should state not only that appropriate measures have been carried out but also how and with what they were carried out and with what level of success.
When cereals are shipped as bulk cargo, lumber used for the grain bulkheads must be air dry, i.e. the water content of the lumber must not be more than 15%. The water vapor released by the lumber may otherwise lead to heating of the cereals and to lump formation along the lumber walls. Spoiled cereals then stay stuck to the bulkheads.
Ventilation
Barley requires particular temperature, humidity/moisture and ventilation conditions.
Recommended ventilation conditions: surface ventilation.
Ventilation of cereals depends on water content: goods with a water content of < 13% and equilibrium moisture contents of < 70% do not need to be ventilated.
Up to a water content of 15%, surface ventilation is recommended, in order to dissipate CO2, heat and moisture. At the same time, care should be taken to ensure that the surfaces are not cooled too much, to avoid the formation of damp boundary layers beneath the cargo surface.
Barley releases water vapor constantly, which needs to be dissipated by ventilation. However, caution is advisable on voyages from hot to cold regions (e.g. Argentina to Europe):
Barley which is not dry for shipment has a particular tendency to self-heating and the flow of heat from the cargo counteracts external cooling, so resulting in the formation of steep temperature gradients in the superficial layers of the cargo. At the same time, water vapor flows from the inside of the cargo to the surface. In the case of simultaneous cooling of the surface by ventilation, the relative humidity increases in the superficial layers of the cargo. If dry fresh air is used for ventilation, a dry surface layer several centimeters thick is obtained, which creates the impression that the cargo is free of all defects. Beneath this is then a damp intermediate layer of lower grade cereal which is starting to decompose, being stuck together and swollen. Such damp intermediate layers are observed relatively frequently.
In order to avoid cargo damage caused by such moist intermediate layers, the fresh air supply must be restricted when there is an excessive temperature differential between the cargo and the external temperature.
Damage to only a proportion of a cargo of barley is as a rule indicative of the damaged proportion having been stored in a dead air zone, where it was inadequately ventilated.
Damage may also be caused by the ships' lying in the roads at the port of destination for an extended period at low external temperatures. The cargo within the stack is, however, still at a higher temperature, resulting in water vapor transport towards the colder parts of the cargo close to the ship's side, where moisture damage may then occur. Such damage is often associated with the fact that ventilation is stopped when the ship is lying in the roads. Ventilation is, however, essential until the cargo has been unloaded from the ship.
It is essential to be aware of the fact that it is impossible to ensure proper airing throughout a bulk cargo of cereals. Even when ventilation is carried out, the relative humidity of the immobile air between the individual cereal grains is determined by the product's water content. For this reason, as mentioned above, drying-out caused by ventilation is generally only superficial.
As a result, cereal loaded in an excessively moist state cannot be dried and protected from spoilage by a ship's ventilation installation.
Biotic activity
Barley displays 2nd order biotic activity.
It is a living organ in which respiration processes predominate, because its supply of new nutrients has been cut off by separation from the parent plant.
Gases
In barley, metabolic processes continue even after harvesting. The cereal grains absorb oxygen and excrete carbon dioxide (CO2).
This excretion of carbon dioxide is important from various standpoints:
If relatively large quantities of CO2 accumulate in the hold, the respiratory activity of the cereal will drop. In the case of cereal which is dry for shipment, hold or container air with an increased CO2 content does not have a negative impact on the quality of the cargo, indeed mold growth is inhibited.
However, if barley is shipped in closed holds/containers at relatively high water contents, the cereal must be expected to change over from aerobic to anaerobic respiration due to the build-up of CO2, which means, among other things, that lactic acid bacteria, which are able to tolerate an anaerobic environment, can also develop. Due to their toxicity, the resultant fermentation products CO2, lactic acid and alcohol have an impact on the grain germ, especially on seed cereal, which loses its ability to germinate if stored in an oxygen-depleted environment.
Respiration may cause life-threatening CO2 concentrations (TLV: 0.49 vol.%) or O2 shortages in the hold/container. Therefore, before anybody enters the hold, it must be ventilated and a gas measurement carried out.