Peanuts
| Infobox on Peanuts | |
|---|---|
| Example of Peanuts |  |
| 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) | Unshelled:
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| Angle of repose | - |
| Humidity / moisture |
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| Oil content | 20 - 60% |
| Ventilation | Recommended ventilation conditions: air exchange rate: at least 10 changes/hour (airing) |
| Risk factors | Self-heating / Spontaneous combustion. Fresh, green, wet, crushed peanuts with a high water content tend in particular towards rapid self-heating, may ignite. Reference is made to the relevant IMO publications of hazardous cargo. Peanuts are sensitive to unpleasant and/or pungent odors, contamination, mechanical influences and insect infestation (see text). |
Peanuts
Description
The peanut, or groundnut (Arachis hypogaea), is a species in the legume or "bean" family (Fabaceae). The peanut was probably first domesticated and cultivated in the valleys of Paraguay. It is an annual herbaceous plant growing 30 to 50 cm tall. The leaves are opposite, pinnate with four leaflets (two opposite pairs; no terminal leaflet), each leaflet 1 to 7 cm (⅜ to 2¾ in) long and 1 to 3 cm broad.
The flowers are a typical peaflower in shape, 2 to 4 cm across, yellow with reddish veining. Hypogaea means "under the earth"; after pollination, the flower stalk elongates causing it to bend until the ovary touches the ground. Continued stalk growth then pushes the ovary underground where the mature fruit develops into a legume pod, the peanut – a classical example of geocarpy. Pods are 3 to 7 cm long, containing 1 to 4 seeds.
Peanuts are known by many other local names such as earthnuts, ground nuts, goober peas, monkey nuts, pygmy nuts and pig nuts. Despite its name and appearance, the peanut is not a nut, but rather a legume.
Peanuts are particularly susceptible to contamination during growth and storage. Poor storage of peanuts can lead to an infection by the mold fungus Aspergillus flavus, releasing the toxic and highly carcinogenic substance aflatoxin. The aflatoxin-producing molds exist throughout the peanut growing areas and may produce aflatoxin in peanuts when conditions are favorable to fungal growth.
Harvesting occurs in two stages.[citation needed] In mechanized systems, a machine is used to cut off the main root of the peanut plant by cutting through the soil just below the level of the peanut pods. The machine lifts the "bush" from the ground and shakes it, then inverts the bush, leaving the plant upside down on the ground to keep the peanuts out of the soil. This allows the peanuts to dry slowly to a bit less than a third of their original moisture level over a period of three to four days. Traditionally, peanuts are pulled and inverted by hand.
After the peanuts have dried sufficiently, they are threshed, removing the peanut pods from the rest of the bush.
Thousands of peanut cultivars are grown, with four major cultivar groups being the most popular: Spanish, Runner, Virginia, and Valencia. Certain cultivar groups are preferred for particular uses because of differences in flavor, oil content, size, shape, and disease resistance. For many uses the different cultivars are interchangeable.
Most peanuts marketed in the shell are of the Virginia type, along with some Valencias selected for large size and the attractive appearance of the shell. Spanish peanuts are used mostly for peanut candy, salted nuts, and peanut butter. Most Runners are used to make peanut butter.
Peanuts have a thin, netted, wrinkly, fragile shell (pod) with 1 - 4 (generally 2) kernels, which are 1.5 - 2.5 cm in size. The shell fraction amounts to 25%. The peanut is native to South America and is cultivated in all tropical and sub-tropical regions of the world. It is also called groundnut or earthnut.
Peanuts are transported both shelled and unshelled. Peanut kernels are surrounded by a fine, brown seed coat, which contains antioxidants which protect the kernels against the penetration of atmospheric oxygen and thereby prevent them from becoming rancid (oxidative rancidity).
Applications
Peanuts have many uses. They can be eaten raw, used in recipes, made into solvents and oils, used in make-up, medicines, textile materials, peanut butter, as well as many other uses. Popular confections made from peanuts include salted peanuts, peanut butter (sandwiches, peanut candy bars, peanut butter cookies, and cups), peanut brittle, and shelled nuts (plain/roasted). Salted peanuts are usually roasted in oil and packed in retail-size plastic bags or hermetically sealed cans. Dry roasted salted peanuts are also marketed in significant quantities. Peanuts are often a major ingredient in mixed nuts because of their inexpensiveness compared to Brazil nuts, cashews, walnuts, and so on. Although peanut butter has been a tradition on camping trips and the like because of its high protein content and the fact that it resists spoiling for long periods of time, the primary use of peanut butter is in the home, but large quantities are also used in the commercial manufacture of sandwiches, candy, and bakery products. Boiled peanuts are a preparation of raw, unshelled green peanuts boiled in brine and often eaten as a snack. More recently, fried peanut recipes have emerged - allowing both shell and nut to be eaten. Peanuts are also used in a wide variety of other areas, such as cosmetics, nitroglycerin, plastics, dyes and paints.
As a legume with a high protein content (24 - 35%), the peanut is one of the world's most important staple foods after wheat. They are grown to be eaten fresh and for oil extraction (20 - 60% oil content). After soya oil, peanut oil occupies second place in world vegetable oil production.
Storage / transport
Peanuts are harvested and shipped all year round. The color and size of the peanuts vary depending on the country of origin, the color of the peanuts varying from light brown to red/reddish brown depending on the color of the soil; the lightest peanuts are the most desirable. It is very important to ascertain the year of harvest: it must be taken into consideration that the nuts may be mixed with nuts from the previous year's harvest. Fresh peanut kernels have a smooth, shiny appearance. Old peanuts are dull and wrinkly. Peanuts from the previous year's harvest have a tendency to insect infestation (beetles and moths) and rancidity. Thus, there is also an increased risk of aflatoxin production (see RF Toxicity/Hazards to health). HPS stands for Hand Picked Selected.
Peanuts may be stored for two weeks in summer and several months in winter.
These days, peanuts are mainly transported in containers. Conventional loading methods are now used only by China. Unshelled peanuts are predominantly packaged in polysacks in quantities of 25 - 30 kg (50 - 60 kg where shelled). Shelled peanuts for producing peanut oil, butter etc. are generally transported loose in bulk. Blanched peanut kernels are frequently packaged in 50 kg polysacks and unshelled nuts are also packaged in 10 kg cartons. Transport is also possible as bulk cargo in ventilated containers (coffee containers), if the water content of the goods is < 4.5% and the lower limits set for the water content of packaging and flooring and the oil content of the goods are complied with and if protection against solar radiation is ensured (-> self-heating).
In damp weather (rain, snow), the cargo must be protected from moisture, since it may lead to mold, spoilage and self-heating as a result of increased respiratory activity. No hooks should be used with bagged cargo, so as to prevent damage to the bags and loss of volume. In order to ensure safe transport, the bags must be stowed and secured in the means of transport in such a manner that they cannot slip or shift during transport. Attention must also be paid to stowage patterns which may be required as a result of special considerations, such as ventilation measures.
In the event of loading as general cargo, dunnage should be used to protect against damage:
- Floor dunnage: criss-cross dunnage and packing paper
- Side dunnage: lining with wooden dunnage and mats or jute coverings: protection from metal parts of the ship, since traces of metal promote cargo rancidity due to autoxidation.
- Top dunnage: important for voyages to cold regions (winter), since sweat may drip onto the cargo.
Temperature
Favorable travel temperature range: 5 - 25°C. At temperatures < 5°C, fresh cargo is subject to cold damage and spoilage. Temperatures > 30°C should not prevail for a long period, as such temperatures promote respiration of the cargo. Heated nuts become rancid and thus inedible. Low temperatures can only limit hydrolytic/enzymatic fat cleavage and cargo respiration. It is therefore of primary importance to ensure storage stability by compliance with water content limit values (see Risk factor Humidity/Moisture).
Humidity / Moisture
| Designation | Humidity/water content |
| Relative Humidity | 65% |
| Water content | 4.5 - 5.5% (unshelled) 4 - 10% (shelled) |
| Maximum equilibrium moisture content | 65% |
Cargo which has become moist exhibits increased hydrolytic/enzymatic fat cleavage, which leads to self-heating as a result of increased respiration. Peanuts are very sensitive to moisture of any kind (sea, rain, condensation water). Peanuts which have become too moist have a tendency to develop mold (Caution: formation of aflatoxin). With bagged loads, the dunnage or the container must be dry and the bags must not be stowed directly against metal parts to protect them from hold or container sweat.
The sorption isotherm for unshelled peanuts shows that they are strongly hygroscopic (hygroscopicity): even at relative humidity of 60%, the peanut water content reaches almost 10%. The curve rises steeply, for example a 12% water content is at equilibrium with a relative humidity of 75%. This means that the mold growth threshold is reached. The steep rise exhibited by the sorption isotherm may be explained by the porosity of the shells. The sorption isotherm for peanut kernels shows that, at a water content of 8%, the mold growth threshold is reached at an equilibrium moisture content of 75%.
Ventilation
Peanuts require particular temperature, humidity/moisture and ventilation conditions. Recommended ventilation conditions: air exchange rate: at least 10 changes/hour (airing). The heat arising through self-heating of the cargo must be dissipated as quickly as possible by ventilation, since hot spots spread very rapidly and may affect entire batches of cargo. If the cargo is loaded with a relatively high water content, heat dissipation must be assisted by suitable stowage measures and ventilation channels. Absolutely fresh, green peanuts are frequently the cause of cargo fires.
Before anybody enters the hold, it must be checked for an excessive CO2 content due to cargo respiration and, if necessary, ventilated.
Biotic activity
Peanuts 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 keeping decomposition processes at the lowest possible level, so as to keep within limits any losses in quality caused by the emission of CO2, heat and water vapor.
Gases
In peanuts (particularly fresh goods), metabolic processes continue even after harvesting. They absorb oxygen and excrete carbon dioxide (CO2). 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.%.
Risk factors
Self-heating / Spontaneous combustion
Fresh, green, wet, crushed peanuts with a high water content tend in particular towards rapid self-heating, may ignite. Fat decomposition in nuts leads to the risk of self-heating and, finally, to a cargo fire.
Fat decomposition may proceed as follows:
- By hydrolytic/enzymatic fat cleavage or
- By oxidative fat cleavage
Hydrolytic / enzymatic fat cleavage
If the critical water content of the peanuts is exceeded, this promotes hydrolytic/enzymatic fat cleavage. Fat-cleaving enzymes are activated by the elevated water content. The additional action of light and heat may accelerate this process. Free Fatty Acids sometimes have an unpleasant odor and taste. In the event of extended storage or improper cargo care, these cause the cargo to become rancid. The free fatty acids formed are consumed by respiration processes in the peanuts to form carbon dioxide and water, a process which is associated with considerable evolution of heat.
Self-heating of peanuts is an extremely vigorous process, as the consumption of fatty acids by respiration processes is associated with a considerably greater evolution of heat than is the case with the respiration equation for carbohydrates. Here too, as with cereals, the spoilage process proceeds in a type of chain reaction, because heat and water are formed by the fatty acids consumed by respiration, which in turn contribute to an intensification of the process. The self-heating of peanuts requires only a small seat of moisture, so that within just a few hours heating may occur at moist points for which weeks or months would be required in goods dry on shipment.
Fresh peanuts with a high water content tend in particular towards rapid self-heating and may ignite. Self-heating of peanuts leads not only to a reduction in the utility value of this product (rancid odor and taste) but also has a qualitative and quantitative effect on oil yield. The color and bleachability of the oils are also negatively affected. The oil obtained complicates refining of the crude oils in subsequent processing, because a higher free fatty acid content makes decolorization substantially more difficult.
Hydrolytic/enzymatic fat cleavage and respiration may be limited by low temperatures; however, this may only be affected to a limited degree during transport. It is therefore important to ensure storage stability by complying with the limit values for the water content of the goods.
Oxidative fat cleavage
Food components frequently react with atmospheric oxygen in spoilage reactions. Atmospheric oxygen may enter into an addition reaction with unsaturated fatty acids through the simultaneous assistance of light, heat and certain fat companion substances. Rancidity caused by oxidative fat cleavage is particularly noticeable in the case of shelled peanuts, because the shelling process results to a certain degree in exposure to atmospheric oxygen or to the steel parts of the ship or the container walls, if not carefully covered with mats. It is therefore absolutely essential to store peanuts in the dark and to protect them from oxygen and metal parts, since otherwise they become brown-colored and develop a rancid odor and taste.
Odor
Active behavior: Peanuts have a very slight, pleasant odor.
Passive behavior: Sensitive to unpleasant and/or pungent odors.
Contamination
Active behavior: As a result of the high oil content of the goods, dark fat spots may appear on the bags, which must therefore not come into contact with contamination-sensitive goods. Do not stow together with fibers/fibrous materials, since oil-impregnated fibers promote self-heating.
Passive behavior: Peanuts themselves are sensitive to dust, dirt and fats and oils. In the case of relatively large consignments, it is advisable to commission an independent surveyor to monitor stowage and inspect the holds with regard to cleanliness, absence of odor, sealing of hatches and ventilation equipment.
Mechanical influences
Peanuts are impact- and pressure-sensitive. If stack pressure is too high, the peanuts are crushed, thereby promoting self-heating. In addition, if the nuts are transported in jute bags, the oils accumulate in the fabric and accelerate the process.
Toxicity / Hazards to health
The molds Aspergillus flavus and Aspergillus parasiticus produce the toxin aflatoxin, which may be present in the cargo as a result of an attack by the above-mentioned mold types. In general, this is "country damage", i.e. the toxin is already present in the peanut at the time of harvesting. As a rule, aflatoxin is only found in individual nuts. If batches of peanuts intended as a human foodstuff are affected by this toxin, the product can no longer be approved for human consumption. Peanuts affected by aflatoxin cannot be distinguished with the naked eye from the other nuts in a batch. The toxin may be detected using UV light.
Shrinkage / Shortage
Volume may be lost as a result of tears in bags and theft. A weight loss of approximately 1 - 2% is deemed normal. Larger weight losses may arise in the event of water vapor emission by fresh, green or excessively wet goods. New crop unshelled peanuts may weigh 12% heavier, for example in April, than those warehoused in December. Valuable cargo, so at high risk of theft.
Insect infestation / Diseases
Insect infestation generally occurs during storage prior to loading and may cause considerable damage, in particular to kernels.
Insect infestation should therefore be looked for when a consignment is accepted, since peanuts are generally infested (grain moths, khapra beetles, flour beetles, mites, cockroaches, sawtoothed grain beetles, meal moths, dried fruit moths and rats and mice). Commission a loading inspector, have reserve samples taken and sealed. The quarantine regulations of the country of destination must be complied with and a phytosanitary certificate and fumigation certificate may have to be enclosed with the shipping documents. Information may be obtained from the phytosanitary authorities of the countries concerned.
Reference is made to the relevant IMO regulations on hazardous cargo ("Seed Cake").
Note: (Source including Transport Information Service of the GDV)