All stages of producing peanuts to trade this product 2
Table 3. Five major developing countries producing cake (Mt 000) and groundnut oil (Mt 000).
|China||1 585||1 646||1 592||1 750||1 740||1 644|
|India||1 859||2 123||1 725||1 675||1 050||1 175|
|China||2 078||2 158||2 087||2 293||2 281||2 154|
|India||2 216||2 511||2 065||2 110||1 286||1 449|
Source: FAOSTAT database 1990 to 1998.
Roasting groundnut with 1 to 4 percent salt is a very common practice throughout the world.It is utilized in various forms including roasted, boiled, raw, ground or paste. Out of the several million tonnes of groundnut produced in the world each year, hulls represent about 25 percent of the total mass produced and is utilized mainly in cattle and poultry feed. The haulms are important as livestock fodder, especially in dry season in the semi-arid tropics.nuts
Among prominent cultivated crops in the developing countries, groundnut is unique because the plant and its produce have a wide range of uses in the daily life of the people as well as in the various industries. The roots of the plant help to enrich the soil and the vines serve as excellent fodder for cattle. The nuts, in addition to being the most consequential source of edible oil, are useful in numerous other ways. When the cake is powdered and extracted in solvent, it yields defatted groundnut meal. Thus the crop has gained great popularity, based on its all-around usefulness and the financial returns it brings to the grower.
Slightly over half of the groundnut production is crushed into oil for human consumption or industrial uses. Protein meal, a by-product of crushing, is an ingredient in livestock feeds.
Groundnut is also consumed directly and is used in processed food and snacks.nuts
Approximately one-third of world production is used in the confectionery products. Utilization of oil, meal and confectionery groundnuts are all increasing concurrent with a gradual shift away from oil and meal into confectionery use. In many groundnut-producing countries, several products and by-products are processed and consumed locally as a few are exported too. Among the by-products traded in the international market are peanut butter and roasted groundnuts. Today, technologies exist for several value-added products from groundnut with very simple locally available materials. Their procdures are quite easy to follow. The groundnut-based products derived from these technologies may be consumed by the farming family or sold in the domestic market. These products may add value to groundnut and enable the farming family to earn additional income.
1.5.1 Export requirements
The quality attributes defined by the final end products made from groundnut vary among the developed and developing countries. Groundnut is mainly used for making peanut butter and consumed roasted or in confectioneries in developed countries. Meanwhile, in several developing countries it is mainly processed for its oil. Most developing countries have not given much attention to the quality. They are obliged to meet the quality parameters fixed by the importer countries for the international trade of groundnut kernels and cake. For example, the general guidelines for the quality of groundnut pods and kernels formulated by the Natural Resources Institute of the United Kingdom Ministry for Overseas Development are: pod colour and type, size, pod texture, cleanliness, freedom from damage and absence of blind nuts; for in-shells and, grading for size or count, shape, ease of blanching, skin colour and conditions; resistance to splitting, moisture content, cleanliness, oil content and flavour; for kernels.
Quality guidelines specify that the groundnut lots must be free from aflatoxin contamination. This is the most important consideration for export quality today. Aflatoxins are the toxic metabolites produced by some strains of fungi of the Aspergillus flavus group. Users may demand certain additional attributes, requirements and salient technical specifications. A large groundnut-processing factory makes its purchase based upon:
Size/grade: for medium runners graded between 83 mm and 71 mm slot screens a count size of 155 to 170 kernels 100 g-1.
Aflatoxin: Five parts per billion maximum, however; recently European Union has modified the aflatoxin B1 limit to 2-μg kg-1 for the consumption of groundnuts by human beings. Moisture: between 6 to 8 percent (determination by air oven drying of ground samples at 130°C for 2 h)
Oil quality: the acid value of cold pressed oil from kernels shall not exceed 1.5, while the peroxidase value shall normally be zero and shall not exceed 1.0 mille equivalents kg-1. Edibility: groundnut shall be free form pathogenic organism (e.g. Salmonella, Escherichia coli) and also free from insect infestation, live or dead and viable eggs.
There are certain other conditions regarding odour and flavour, splits, damaged kernels and unshelled groundnuts, foreign matter and discoloured/mouldy nuts.
1.5.2 Inspection and diversion of aflatoxin contaminated lots
To ensure that groundnut utilized for food or feed contain less than 20 ppb aflatoxin, various agencies in developing countries, for example IOPEA in India and the AGC in Africa, are regulating the export quality of groundnuts and groundnut products.
1.5.3 AGC agreement with the FAO
At the 18th Session of the FAO Intergovernmental Group on Oilseeds, Oil and Fats, 20 to 24 February 1984, in Rome, the AGC was part of the delegation, which discussed the proposed modifications to the EEC Directives regarding tolerance limits of undesirable substances (especially aflatoxin B1) in cattle feed. After detailed discussion, the group finally declared that “all legislative regulatory measures in this field should necessarily be based on data which can be verified through reliable means, in order to prevent any unjust harm to the concern parties and to the liberty of international standardization of norms so the Joint Committee FAO/OMS of the “Codex Alimentarius” could fix aflatoxin limits which are internationally recognized, uniform and reasonable. Considering the significance of the aflatoxins, several countries including the FAO (Codex Alimentarious Committee) have set the tolerance limits for groundnuts and its extractions. India and the United States of America have set 20 μg kg-1 of seed meant for human consumption as tolerance limit. As of the year 2000, European Union has formulated the following limits of aflatoxins for various categories of groundnuts (Table. 4).
Table 4. Tolerance limits for aflatoxins as set by European Union.
Tolerance limit (μg kg )
|B1||B1 + G1 + B2 + G2|
|Groundnut for direct consumption||2||4|
|Groundnut for further processing||5||10|
|Milk and milk products||0.05||–|
The key attributes for the export of groundnuts are piece count referring to the number of seeds per ounce, aflatoxins and physical properties such as brokens and admixtures. The seed size expressed as piece counts is crucial to determine commodity value. Until now, there have been no limits for the pesticide residues in the seed and cake. The increasing interest in healthy eating has initiated the concept of organic farming in developing countries. Groundnuts grown without synthetic pesticides and fertilizers would fetch a premium.
1.5.4 Aflatoxin limits fixed by importer countries
Many groundnut-importing countries have placed limits on the levels of aflatoxins permissible in groundnuts and groundnut products (Table 5). Countries depending on export of aflatoxin-susceptible commodities e.g. groundnuts are obliged to establish export limits that meet importers’ requirements. This leads to economic loss, if the requirements are unnecessarily strict. Where a local food is also an export item, exportation of the most wholesome food may lead to local consumption of more contaminated foods. In part, this augments the risk of toxic effects in the indigenous population.
Table 5. Maximum possible levels of aflatoxin in imported groundnut for human consumption and livestock and poultry feeds.
|Country||Aflatoxin type||Maximum permissible level (ng g-1), 1995|
|Sweden||B1, B2, G1, G2||5||10|
|UK||B1, B2, G1, G2||4||20|
|USA||B1, B2, G1, G2||20||20|
Source: Freeman et al. 1999, ICRISAT
nuts: Groundnut quality and consumers preference may be judged by the following parameters: Flavour: The flavour of the roasted groundnut plays important role in its acceptance by consumers and other users. Flavour also plays an important role in the acceptability of groundnut products such as peanut butter. Samples of several high yielding genotypes showed that their flavour quality needs improvements. A method of evaluating the cooking quality of groundnuts by boiling them in shell has been standardized at ICRISAT (ICRISAT, Report 1990). More than 300 compounds have been detected in roasted groundnut. Sugars in groundnut also play an important role as precursors in the production of the typical roasted groundnut flavour. Thus it is important to standardize the test used to evaluate the acceptability of roasted groundnut by conducting sensory evaluation and relating the findings to the presence or absence of various volatile compounds and the concentrations in which they are present. Studies indicate that hexanal concentration is one of the eight compounds that gives an objectionable flavour to groundnut and correlated with a professional flavour profile panellists’ evaluation. Characterization of flavour compound by gas chromatography would enable breeders to identify those cultivars that have a good flavour profile for further development (Ahmed and Young, 1982).
Texture: Crunchy and crisp are textural attributes that are important and desirable sensory qualities of groundnuts. Crisp food is one that is firm (stiff) and snaps easily when deformed emitting a crunchy/crackly sound. Based on consumer study, crispness has been reported to be the most versatile single texture parameter. A number of instruments have been developed for measuring mechanical properties of nuts, which can be related to texture of the kernels. Sensory quality: Mechanical force and work usually have strong inverse correlation with sensory crispness and crunchiness scores. Sensory evaluation of texture in foods belongs to the domain of psychology known as psychophysics. Psychophysics directly concerns the correlation of sensory experience with physical measures. Two measure classification of sensory tests are: i.) affective and ii.) analytical. Affective tests are used to evaluate preference and/or acceptance of products. This method; however, cannot provide a proportional relationship between sensory scores and physical measures. Analytical tests are used for quantification of sensory characteristics. Evaluating the textural quality of groundnuts, sensory panellist can either bite or chew those groundnut kernels. The physical property differences between row, blanched and oil roasted groundnuts was distinguished best by a compression test (Vivar and Brennan, 1980). When groundnuts are exposed to high relative humidity environment they absorb moisture and become soggy, the consumers do not prefer such products.
Colour: Colour of raw groundnut kernels is attributed to both the testa and the oil. Tannins and catechol-type compounds are responsible for imparting the colour to the testa. The colour of cotyledons is due primarily to the oil colour present in the cells of the cotyledons. The measure carotenoid pigments present in oil are β-carotene and lutein. Maximum concentration of these pigments occurs in the immature kernels i.e. 60 µg of β-carotene and 138 µg of lutein per litre of oil and diminishes as the groundnut advance to maturity. Consumer preference is light coloured groundnut oil. The characteristic colour of roasted groundnut is due primarily to the sugar-amino acid reactions with subsequent production of melanins. Caramelization of sugars may contribute to brown coloration of roasted groundnut. Consumers reject soft or mushy roasted groundnuts even though they exhibit attractive colour and good flavour (Hodge, 1953).
Indian groundnut is very popular in the international market for the table purpose, due to its characteristic natural flavour, nutty taste and crunchy texture and also has relatively longer shelf-life. Therefore, with the growing consumer taste the world over for organic food with natural flavour, Indian groundnut has better export opportunity. Consumption of groundnuts as nuts and in the manufacture of peanut butter is based on the use of roasted groundnut kernels. Roasting time has a significant influence on the strength of the odour and flavour. Raw and roasted groundnuts should be free of foreign material, unadulterated with toxic or noxious substances such as pesticides and microorganisms. The Food and Drug Administration (1969) issued guidelines for food manufacturers who produce wholesome food items including groundnuts and groundnut products. The “Official Methods of AOAC” gives methods (36.020 to 36.024) for the determination of adulterants in food.nuts
Groundnuts especially those produced in the developing countries have been used traditionally since the origin of humanity. It is rich in oil and protein and has a high-energy value. Developing countries account for nearly 95 percent of world production. Asia accounts for about 70 percent of this amount where the major producers India and China together represent over two-thirds of global output. Other important producers are Nigeria, Senegal, Sudan and Argentina. In most of the developing countries kernels are used for oil extraction, food and as an ingredient in confectionery products. Following extraction, the residual cake is processed largely for animal feed, but is also used for human consumption. The quality attributes that are important for end uses of groundnut vary among the developed and developing countries. Groundnuts are mainly processed for oil in several developing countries. Even though it is a good protein source, the cake obtained after oil extraction is not utilized to the best advantage. Production of aflatoxin due to the invasion of the fungus Aspergillus flavus to groundnut pod/kernel is a serious problem in the trade of groundnuts in the international market, which has seriously hampered the export business of the developing countries. Therefore, these countries can no longer rely on monoculture in order to support their growing economies.
Under current conditions, crop dependency has made producers vulnerable to losses because of the lower prices paid for the pods and kernels. It is, therefore, imperative for them to diversify their production and create added value through processing thereby reducing risks and opening new local and export markets. There is a necessity to investigate new opportunities for the use of groundnut as food and confectionery items. Most of the developing countries have poor drying and storage facilities. Under these conditions the seed loses its quality and viability in storage rapidly. The purpose of this publication is to discuss the importance of the post-production system in developing countries and to suggest suitable curing, drying, storage and processing technologies. Advised methods are especially meant for the smallholder farmers and the most diversified uses of groundnut in confectionery items.
The tools and equipment fabricated locally by farm families themselves or by rural artisans mainly perform post-harvest processing of groundnuts in the traditional manner. Commercial machinery is normally manufactured in urban factories or overseas. The introduction of commercial machinery signals a decline in demand for the products of rural artisans. This potentially diverts cashflow away from the rural economy. As well, it will probably increase the drain on the country’s scarce supply of foreign exchange for imported machines, spare parts and fuels. Please see Figure 2. In many cases, suitable machines could be made locally by the use of simple machines, tools and welding equipment.
Figure 2: Artisan fabricating a thresher in a local market.
Training of rural artisans, upgrading of technology in rural workshops, provision of credit plus other support services may encourage local manufacture of necessary machines. Small-scale farmers regard the groundnut as a very labour-intensive and high-risk crop. The high labour allocated for weeding, harvesting, drying, threshing and shelling makes the crop economically unattractive to the younger generation of farmers. Research is needed to provide the farmers with better implements. Farm operations comparable to digging or harvesting, curing, drying, shelling, grading and storage are must be suitably modified to reduce the quantitative and qualitative harvest and post-harvest losses.
The basic idea used to develop a crop management strategy is to provide an environment that allows maximum yield with reduced risk of losses, proper use of pesticides and other petrochemicals and minimal environmental contamination. In short, a successful plant health management strategy must include management of all the following:
- Physiological and environmental disorders,
- Pre-harvest and post-harvest insects,
- Viral diseases and foliar pathogens,
- Soil borne fungal pathogens, nematodes and mycotoxin producing fungi.
To be practicable at the farm level, plant health management strategies must be integrated as a package approach. Some guidelines for the cultivation of groundnut are mentioned below.
- Fields may be selected with suitable type of soil, as the groundnut grows best in deep, well-drained soils with a sandy or very loose surface layer. Most soil rubbed between the index finger and thumb should not ribbon out but should fall apart easily. An exception to this rule is Gujarat (India) where most groundnut is grown in heavy, black-calcareous soils. Therefore, farmers practice adding sand or gravel or moram into the furrows before sowing once in 3 to 4 years to make the soils friable.
- Groundnut crop rotation with other crops, such as sorghum, maize, cotton, pigeon pea and castor is beneficial in several ways: i.) more effective use of residual soil fertility; ii.) improved efficiency in controlling certain weeds; and iii.) reductions in soil borne disease and nematode problems.
- Conventional primary and secondary tillage operations may be performed to control diseases and weeds and to operate a seedbed for planting.
- Sowing may be performed with high-quality seed in well-prepared, moist seedbed. Groundnut seeds are generally planted at a depth of 4 to 5 cm. The spacing between row-to-row and plant-to-plant varies with the type of groundnut sown. After sowing in moist soil, water uptake is the first phase in returning the dry seed to active growth. For rapid emergence, soil temperature above 21°C is needed. The optimum temperature for the most rapid germination and seedling development is about 30°C.
- Temperature is a major environmental factor that determines the rate of crop development. Temperatures above 35°C inhibit the growth of groundnut.
- Moisture-deficit during vegetative phase is beneficial to increase water use efficiency. Because of the complex interactions between the soil and plant water status, the atmospheric conditions that influence both of these and the critical timings of water application need considerable research at various agro-ecological regions.
- Length of crop growing season required for the four different types of groundnut varies widely, but it takes Virginia and runner groundnut, in general, 1 to 6 weeks longer to mature than Valencia and Spanish groundnut.
Figure 3: Groundnut pod, inside shell and kernal colouration determines the right maturity stage. Dark tan colour inside the shell indicates maturity.
Groundnut pod development takes place in the soil making it difficult to correctly judge the maturity of the crop. Farmers are obliged to have considerable experience and great vigilance to carry out the harvesting operations efficiently without much loss of quality and yields. A proper time to commence the harvest is when a good number of pods are fully developed and are fairly intact. This condition is normally achieved when the vine begins to turn yellow and leaf shedding starts. The actual maturity of the pod is determined when they attain normal size with prominent veins, the inside of the shell turns dark and the kernels reach maximum growth accompanied by good colouration of the seed coat.
A fully mature pod can often be difficult to spilt open with the
pressure of the fingers. Meanwhile an immature pod can be split easily revealing the white inside surface of the pod which appears also to be spongy in texture. These criteria may help in assessing the correct stage of the harvest of groundnut crop. Harvesting at the proper time ensures that a high percentage of mature pods remain on the plants and the maximum number of pods has attained their greatest weight or physiological maturity (Figure 3).
Delay in maturation may also occur because of late-season drought stress. Long periods of rain immediately prior to harvest may result in both yield loss and deterioration of quality of groundnuts. Several methods have been described for determining the maturity of the groundnut crop i.e. shell-out maturity and hull-scrap maturity testing methods. The prevailing attitude among the groundnut production specialist is that the hull-scrap method is not accurate for Virginia and Spanish types groundnut and may predict a harvest time that is too early. Following are the tips of the shell-out maturity testing method:
- Select five to ten plants from representative areas of the field.
- Pick off all combine-harvestable pods i.e. soft; watery pods that shrivel in windrows should not be used.
- Break open each pod to examine internal hull and seed coat colour.
- Place pods with tan to black internal hull colour and pink to dark pink seed coat colour together as mature pods.
- Calculate the percentage of mature pods: percent mature pods =[number of mature pods/(number of mature pods + number of immature pods)] x 100.
- Mature pod percentage for approximate harvest time: runner, 70 to 80 percent; Virginia, 60 to 65 percent; Spanish, 75 to 80 percent.
- Other considerations:
- If leaf spot or other diseases are problem in the field, do not delay harvest.
- If there is a weather forecast that would delay the harvest, this must be taken into account.
- Harvest must be done when sufficient labour and adequate equipment are available.
- Failure of peg strength and well-filled pods with pink seed coat indicate maturity in large-seeded Virginia type. Signs of weakening peg strength indicate immediate need for harvest if excessive losses are to be avoided. Check groundnut crop closely as the average number of days to maturity approaches.
Seed-hull ratio and shelling percentage as indicator of groundnut maturity:
The seed-hull ratio as an index of groundnut maturity was first proposed by Pattee, et al. (1977) and is obtained by dividing the mass of the seed by the mass of hull (shell). The ratio may be determined on the basis of fresh as well as dry seed mass. Shelling percentage is the proportion of the mass of the seed in a given mass of seed in a given mass of pods. It is usually measured on the basis of dry mass. Shelling percentage is an important attribute in the evaluation of varieties and in trade transactions, which involve unshelled groundnut. Troeger, et al. (1976) were apparently the first to use the seedpod ratio as a maturity indicator for individual pods.
The mathematical relations of this method are given below:
Seed-pod ratio (SPR) = seed mass (S) / Pod mass (P)
= S/P-S x (P/P-S)-1
= seed-hull ratio (SHR)/ Pod-hull ratio PHR)(1)
PHR = P/P-S
= 1 + S/P-S
Substituting (2) in (1), we get
SPR = SHR/(1 + SHR)(3)
Multiplying both sides by 100, equation (3) can be restated as:
Shelling percentage =100 [seed-hull ratio/ (1 + seed-hull ratio)]
Hull-pod ratio (HPR) = 1-SPR(4)
SHR = S/P-S
= S/P x (P-S/P)-1
Substituting (4) in (5), we get
SHR = SPR/ (1-SPR)(6)
Multiplying and dividing the right hand side by 100, equation (6) can written as:
Seed-hull ratio = shelling percentage/(100-shelling percentage).
Table 6. Groundnut cultivars and elite germplasm being used in various developing countries for their useful traits.
|Name of cultivars|
|Characteristics and remarks|
|CG 7||ICRISAT||High yielding confectionery type, longer selflife|
|ICGV 86325||India||Released jointly by ICAR and ICRISAT for rainy season cultivation|
|BARD 92 [ICGS (E) 56]||Pakistan||High yielding released by the Pakistan Agriculture Research Council.|
|1.Stella (ICGV- SM 85|
048) 2. Veronica (ICGVSM 86715)
|Mauritius||High yielding released by Mauritius Sugar Industry Research Institute.|
|ICGV 91004||ICRISAT||Higher and balanced pod yields in relation to fodder yield across the locations.|
|ICGS 76, ICGS 44||ICRISAT||Drought tolerant and high yielding cultivars|
|Kadiri 3, J 11, TAG 24,||India||High yielding and usually taken as National checks.|
|ICG 7625 and 5856||ICRISAT||High oil content|
|ICG 5369 and 5856||ICRISAT||High O/L ratio|
|ICGV 87123||ICRISAT||High P/S ratio|
|ICGV 86552||ICRISAT||Resistant to insects and pests, bud necrosis disease, tolerant of end-season drought.|
|ICGV 86606||ICRISAT||Foliar disease resistant|
|ICGV 86398 and 86393||ICRISAT||Pest resistant|
|ICGV 87480||ICRISAT||High yielding and short-duration|
|ICGV 91278||ICRISAT||Resistant to seed infection by Aspergillus flavus|
|ICGV 87350||ICRISAT||Foliar disease resistant|
|ICGS (E) 56 (ICGV 86015)||ICRISAT||A short duration variety|
|NRCG 1800 (ICG 2530)||India||Resistance to ash-weevil and root knot nematode.|
|NRCG 8440 (ICG 3563)||India||Tolerant to iron-deficiency chlorosis|
|Name of cultivars|
|Characteristics and remarks|
|NRCG 664 (NCAc 17090)||Peru||High peg strength|
|NRCG 609 (ICG 3404)||Argentina||Salinity and drought tolerance|
|NRCG 2615 (ICG 1587)||India||Cold tolerance and resistance to Spodoptera litura|
|Chico (ICG 476)||–||Short-duration|
|TAG 24||India||High harvest index (HI)|
|ICG 86031||–||Higher water use efficiency (WUE)|
|TKG 19 A||India (BARC)||High shelling percentage (68 to 70%)|
|CSMG 84-1||India||High yielding and rust resistant Virginia runner|
|GG 20||India||High yielding semi-spreading variety|
|Luhia 15||China||High-yielding, small-seeded with O/L ratio|
|Birsa Bold 1||India||Promising new confectionery variety|
|BR 1||Brazil||High yielding cultivar seed yield 1.3 t ha-1.|
|NCAc 343||ICRISAT||Multiple insect pest resistance|
(P=polyunsaturated and s= saturated acids)
It is evident that shelling percentage could also be used as an index of maturity in addition to seed-hull ratio (Abdul and Ahmadi, 1994).
Promising cultivars: Some promising cultivars and elite groundnut germplasm being used in the developing countries were shown in Table 6.nuts