eating quality ,All stages of producing peanuts to trade 7

eating quality 

All stages of producing peanuts to trade this product 7







Figure 23: Arachilipometer developed and designed and developed at NRCG.


Nutritive quality

Proteins: There is growing demand for protein throughout the developing world. Groundnuts are good sources of proteins and have high-energy value (average 564 calories/100 g seed), thus in the developing countries groundnut is very important crop to meet the demand of oil and protein in daily diet. Groundnut germplasm collection at ICRISAT demonstrated protein content ranges between 15 to 34 percent depending upon the cultivar, location and year. The genetic variability in the mechanism of protein synthesis during development of seed suggests that there is potential for the development of groundnut cultivars possessing nutritionally desirable proteins by manipulating protein synthesis.eating quality

The major proteins are arachin and conarachin. Groundnut proteins undergo changes due to heating or roasting of the seed

and removal of the oil from the seed by solvent extraction. On heating the antigenic structure of the major reserve protein α-arachin should remain intact in groundnuts and groundnut products, when heated during processing. Generally this reserve protein remains unchanged even heating for 1 hour at 145°C (Jambunathan, 1991).

Amino acids: The contents of amino acids in groundnut seed very according to type of groundnut, cultivar, location, year and length of maturation period of seed. With advancing the maturity of groundnut seed, amount of free amino acids decreases, while protein content increases. Arginine undergoes the greatest reduction in content upon maturation; thus it is proposed that argenine content could be used to determine the degree of maturity of groundnut seed and also suggested that free amino acids can be incorporated into protein at different rates. Thus high-protein cultivars contained higher amounts of free amino acids than the low protein cultivars, during seed maturation. This implies that certain polypeptides or proteins with a specific amino acid composition are selectively deposited in the maturing seed at different time intervals and at different rates among the various groundnut cultivars. Conarachin proteins that are high in essential amino acids were observed to be deposited during early stages of maturity while the arachin protein that are low in essential amino acids deposits during the later stages of maturation (Basha, et al., 1980).

According to FAO (1970), the limiting amino acids in groundnut  are lysine and methionine, but there are reports, which indicate that lysine, metheonine and threonine are equally limiting (Miller and Young, 1977). Tryptophan has also been included as a possible limiting amino acid in groundnut (Milner, 1962). Much published information is available on the amino acid composition of groundnut (FAO, 1970). The ranges reported for the amino acids, lycine, methionine and threonine as per cent of protein are 2.1 to 3.9, 0.35 to 1.0 and 2.3 to 2.7, respectively.

eating quality

Carbohydrates: In groundnut sucrose is the major sugar measuring from 2.86 to 6.35 percent among different cultivars, followed by stachyose and raffinose (Pattee, et al., 1974). Slight loss in sugar contents is found upon roasting and there is about 15 percent loss in sucrose and inositol and about 33 percent loss in glucose and fructose. Please see Table 16 and 17. Fructose and glucose occurs in small concentrations, but it was found that the sucrose undergoes hydrolysis to the two monosaccharides, fructose and glucose, which in turn reacts with some free amino acids to form the characteristic flavour of roasted groundnuts.


Table 16. Effect of roasting on sugar content (mg g-1 fat-free groundnut meal) of Spanish type groundnut.

SugarRaw Roasted 
Fructose and or/ Mannose2.71.6-

Source: Mason, et al., 1969


Minerals and vitamins: Groundnut contains much more potassium than sodium and is good source for calcium, potassium, phosphorous and magnesium. Three forms of vitamin B1 exist in groundnuts such as thiamine, thiamine-mono-phosphate and thiamine-pyrophosphate. Thiamine occurs in groundnut seed at a concentration of about 1mg/100g. Each ounce of groundnuts can meet the daily dietary requirement of several important vitamins and minerals. Groundnuts are rich source of agrinine (about 3.5 percent), which helps in wound healing and immunity. Vitamin E, selenium and zinc are regarded as antioxidants, which protect body tissues from free radicals. Incidentally, National Aeronautics and Space Administration (NASA) of the United States of America has selected groundnut as a possible food for the Advance Life Support system for extended space missions.


Table 17. Nutritional characteristics of groundnut kernel.

CharacteristicsContent 100-1 g  
RawRoastedDefatted flour
Calories (g)564.0582.0371.0
Proteins (g)
Fat (g)47.548.75.8
Carbohydrate (g)18.620.630.0
Calcium (mg)69.072.0127.0
Phosphorus (mg)401.0401.0800.0
Iron (mg)
Thiamine (B1) (mg)1.140.320.75
Riboflavin (B2) (mg)
Niacin (mg)

Source: Burn and Huffimann, 1975



Sensory quality

Sensory quality is the summation of all physical and chemical characteristics of edible seed or their products that influence human senses and result in acceptability judgements by the consumer. Several volatile components isolated from roasted groundnuts were described as contributors to “nutty” odour or a “nut-like”. Some of which are 2-crotolsctone, 3-methyl-2carotolactone, 5-hydroxy-4-nonenoic acid, pyrazines, 2-isopropyl-4, 5-dimethylthiazole and 2-propyl-4, 5 diethylthiazole, most of them have been characterized as having green nutty aroma (Ho, et al., 1982). Several flavour evaluation lies on the use of human subjects as the detectors of sensors of food-flavour. For roasted nuts, the Quality Committee of APREA (1971) has adopted the CLER flavour score method. Twenty roasted half-seed are tested individually and a score is assigned to each seed. The total of these scores will represent the treatment flavour score. It is suggested that standardized sensory methodology should be followed to evaluate the flavour of food products. Such methodologies are outlined in several publications (Rodriguez, 1976; Larmond, 1977).

eating quality

Studies in Japan showed a negative correlation exist between whole pod mass and eating quality. For the same level of yield varietal differences in eating quality exist, which enables the selection of a high-yielding variety with better eating quality. The correlation between sweetness and eating quality and seed hardness and eating quality increases as sweetness and seed hardness is augmented. On the other hand, eating quality is more closely correlated with sweetness. The correlation between external quality and eating quality was so low that good external quality as determined by pod and seed is not necessary associated with good eating quality. Based on the studies it was suggested that the sucrose content and hardness of the seed, which are most closely related to the eating quality, could be used as indicators for the evaluation of the eating quality in tests (Gocho, 1992).

Seed hardness decreased with the delay in harvesting time and selection for seed hardness should be determined 85 days after flowering. Sucrose content of seed decreases when the harvesting time was delayed. The eating quality also shows a similar trend. Therefore, sampling time for this character is very important. The sucrose content should be analyzed at the optimum sampling time of the lines, based on the harvesting time, namely 75 days after flowering for early-maturing varieties, 80 to 85 days for medium maturing varieties and 95 days in late-maturing varieties (Pattee and Young, 1982).

2.8.3 Oil processing

Food processing constitutes a major economic sector in developing countries, especially in urban areas where low-income families are not equipped to carry out the basic processing of agricultural and animal products. Food processing also allows the consumption of seasonal agricultural products over the whole year and therefore minimizes the important price fluctuations resulting from the periodic gluts and shortages of the fresh products. In addition, food processing could generate substantial foreign exchange. Thus extraction of oils from the kernel of groundnuts is a well-established industrial activity in a number of developing countries. Since the early 1950s, most groundnut-growing countries have favoured indigenous oil extraction in preference to the export of kernels. They have thus support the setting up of factories for this purpose, which, are large-scale plants situated in or near urban areas. Commercially oil is extracted from groundnut by three methods including hydraulic pressing, screw pressing and solvent extraction.

Power ghani mill

The ghani mill originated from India where these indigenous oil crushers have been improved over the time. The original animal-powered ghani consists of a wooden mortar and a pestle.

The mortar is fixed to the ground while the pestle attached to one or a pair of bullocks (or buffaloes or camel) is rotated in the mortar where the kernels are crushed by the generated fraction and pressure. The oil runs through a hole at the bottom of the mortar while the residue or cake is scooped out. Depending on the size of the mortar and the type of kernels, an animal-powered ghani can process 5 to 15 kg of kernels at a time. An improved version of the ghani has been developed in India, known as the Wardha Ghani (see Figure 24). It is larger as well as more efficient than the traditional ghani and can crush charges of kernels of up to 15 kg in approximately 1.5 hours or close to 100 kg per day. Two or three family members are required for the operation of the mill. It is essential that one of the workers should have the necessary qualifications for running, maintenance and repair of the ghani unit. An engine-powered ghani is now replacing, to a large extent, the bullock-powered ghani. In this type of ghani, either or both the mortars and pestles are made of cast-iron. Power ghanis are often work in pairs. The crushing capacity of a two-ghanis unit is approximately 500 kg to 600 kg of kernels per day.

Some of the technical advantages of the power ghanis, as compared to bullock-powered ghanis include a higher oil extraction rate per unit of raw materials representing an increase of approximately 1 to 2 percent of the extraction rate. There is a higher output per unit of time and less space is used than in the case of bullock-powered ghanis. The quality of the oil produced by the power ghanis is identical to that produced by the bullock-powered ghanis. Power ghanis are now increasingly replacing bullock-powered ghanis (ILO, 1990).

 Figure 24: Line diagram of Wardha Power Ghani.


Improved power ghanis have oil extraction efficiency, which fairly close to that of smallscale expellers and often constitute a viable alternative to the latter, especially in rural areas. While this has been the case in India and in a number of Asian countries, there is no guarantee that ghani mill meet the same approval in other developing countries. For example, the introduction of ghani in Tanzania has met with little success. It is therefore, important to analyze all the requirements for the successful adoption of ghani mills prior to investigating in such units. For example it is important to investigate whether qualified labour is available in ruler areas, whether the miller or local mechanics can carry out the maintenance of ghani without much difficulty and whether power ghanis may be manufactured locally or must be imported. A large number of designs of powered ghanis have been developed and marketed in India. The detailed information regarding the drawings and name and addresses of manufacturers may be obtained by writing to: Appropriate Technology Development Association, P.O. Box No. 311, Gandhi Bhawan, Mahatma Gandhi Road, Lucknow-226001, India.

Oil extraction by pressing

The unit is a double ghani-mill, powered off a single 3-hp motor. Each ghani takes a charge of about 35 kg, which is processed in approximately one hour by the rotary movement of the iron pestle in the bowl. Thus such a unit may process 560 kg of kernel per day. Separate engines may also power the two ghanis. In this case, 2-hp motors are needed. The pestle in power ghanis rotates at approximately 10 to 12 revolutions per minute as compared to 3 to 5 revolutions for bullock-powered ghanis.

Oil filtration: To remove small impurities, oil must be filtered using an ordinary cloth stretched over a frame onto a tank of sufficient capacity. The filtered oil should be left in the tank for a few hours in order to allow the settling down of any fine impurities. The oil than is transferred into tins or bottles with a funnel from a tap on the tank. The tap should be attached over the sediment layer. The cake can be removed from the ghani manually. It may need little or no further breaking-up. The broken up cake meal can be loaded into bags manually. In general, the cake may spoil rapidly after a few days, unless it is properly treated, packaged and stored.

Advantages and disadvantages of ghani crushing

When ghani crushing was widespread, fresh oil was in greater demand than it is today. Flavour, which was traditionally an important attribute of all oils, was best in oils produced from mild ghani crushing. Since vegetable oils are naturally sterile, problems of hygiene in ghani oil are unlikely. Ghani cake is also known to be exceptionally hard and dry and is not prone to mould infestation unless inadvertently wetted. However, the ghani has disadvantages, which are mainly economic in nature. Traditional ghanis have a maximum capacity of about 50 kg per day and modern powered units only about twice that much. As a result, running costs are disproportionately high. If animals are used, they need to be trained and they are expensive to feed. Artisan training is also essential. Ghani oilcake as pressed out of the unit after crushing is externally hard and is not accepted by the trader for further solvent extraction, as are expeller oilcake (Achaya, 1993).

eating quality

Baby expeller mills

The baby expeller mills as defined in the joint memorandum of International Labour Office (ILO) and the United Nations Industrial Development Organization in 1990 have 45 to 55 kg per hour capacity. Therefore, by working only a one-day shift, as is normal for small plants, the unit can process between 350 and 450 kg of raw material per day. In a few cases such units do work 2 or 3 shifts per day and may then process up to one tonne of raw materials. Before crushing the seed remedial drying may be carried out in the open air or under a covered shade in case of adverse weather conditions. A drying ground of approximately 20 m2 is sufficed. This mill may use a crusher of the swing beater type with a capacity of 100 kg of material per hour, a 2-hp power requirement and revolving at 1 400 rpm. The seeds can be heated in open pans over enclosed fireplace to ensure fuel economy. The raw materials may be mechanically stirred through, for example, a linkage to the expeller or crusher drive. The length of time required is about 20 to 30 minutes and temperature 60 to 90°C. Trial and error will show the best conditions in terms of oil yield and quality. Cooking or scorching of seed is needed for three reasons: to facilitate oil extraction, to lower or increase the moisture of seed and to reduce the wearer in the screw press. The best temperature and moisture content depends on the extraction system, however the temperatures attained during cooking should not exceed 120°C as otherwise the protein quality may be adversely affected. In general, the required cooking temperature is a function of the cooking time, the type of oil extraction technology, the moisture content of the row material and the type of seed. The cooking or scorching of seeds should be carried with care in order to avoid the deteriorating groundnut kernels. Overheating reduces the oil extraction rate and yields lower quality oil. Since small rural processors neither may nor afford scorching equipment with automatic control of temperature and moisture of the material, they should arrive at the right cooking conditions through learning and experience.

eating quality

Oil extraction by pressing: Pressing can be achieved a single, duo or duplex expeller. Their drive can be provided by either an electrical motor or via a pulley and v-belt from a separate diesel engine. Various specialist manufacturers, notable in Japan and in India, produce small capacity expellers. When using a single expeller, the decision on whether to pass the seed once or twice should be based on economic considerations. A second pressing raises the oil extraction rate and therefore, yields additional revenues, but also increases processing costs. Thus, a second pressing is justified only when the increase in revenues is at least equal to the increase in cost. In general, at relatively low extraction rate of small expellers, small rural mills in developing countries find it profitable to press the row materials twice, the first time at low pressures and therefore, high hourly output and the second time at higher pressure through an adjustment of the choke.

eating quality

The extraction of groundnut oil in small expellers is a highly skilled job as it is necessary to add groundnut shells to the kernels in order to prevent the forming of groundnut butter. The adding of shells is necessary because groundnut kernel unlike copra have little fibre. The need for skilled labour should therefore be taken into consideration while choosing among various types of expellers. Expellers require periodic maintenance and repairs, the principal wearing pieces being the liner bars, the worms and the distance pieces. The periodicity of maintenance and repairs is a function of the rate at which the abrasive action of the row materials and that of foreign matter i.e. sand, pieces of iron wear the above piece of the equipment. The abrasive action of foreign matter is particularly harmful and can considerably shorten the life of various parts of expellers.

Filtration: Alternatively and whenever it is economically feasible, the mill may use a small chamber filter press with 10 plates of 18 x 18 cm, with attached oil pump. The pump makes 170 rpm and has a power requirement of 0.5 hp. Such a press may process up to 50 litres per hour and should therefore be sufficient for the filtering of the daily out put of oil. Filtration takes place through paper and filtre cloth. The mill owner should have the necessary skills for the running of the equipment, as well as for maintaining and repairing the latter. The daily out put of oil is 156 kg and cakes 215 kg. Two or three family members should suffice for the running of the unit. The mill owner should have the necessary skill for the running of the equipment, as well as for maintaining and repairing (ILL, 1990).

 Solvent extraction plant

Even the most perfect expeller leaves at least 6 percent of the oil in the expeller cake. It is possible to recover these losses using a solvent extraction plant and can reduce the residual oil in cake to less than 1 percent. A major drawback of this process, especially in view of the bias of the memorandum towards small-scale production, is that it is by nature suited to largescale extraction. The range of production leaves employed in solvent extraction plants is between 50 to 200 tonnes per day. Other drawbacks include high investment costs, the need for highly skilled labour, low employment generation and danger of explosion if the plant is not kept in perfect conditions. While solvent extraction plant may not constitute a viable rural industry, a number of these plants may be profitably established for the processing of both oil seeds and the cake produced by small oil extraction units. This will however, require a good cake collection system and a sufficient supply of oil seeds in order to maintain the solvent extraction plant running at sufficiently high capacity utilization rate.

Oil in human consumption

Groundnut oil is used primarily as a cooking and salad oil. Small quantities of groundnut oil are used in the manufacture of shortening and margarine. Groundnut oil is excellent fat for pan-frying or deep fat frying. Pastries shortening, oleomargarine, mayonnaise, salad dressing and other food products can be easily made with this bland vegetable oil. For use in mayonnaise, it should retain its natural yellow colour, for oleomargarine, it should be colourless, for shortening and other plastic fats, for all purposes it should contain an antioxidant. Groundnut oil is also marketed as crude oil for soaps and detergents. It forms the base for many face creams, shaving creams, hair lotions and other cosmetics because it is believed to energize the skin. It is used extensively for massaging polio patients. It is also used as a carrier of adrenaline in the treatment of asthma and other ailments.

eating quality

Adequate amounts of dietary fats are essential for health. In addition to contribute to meet energy needs, intake of dietary fat must be sufficient to meet requirements for essential fatty acids and fat-soluble vitamins. The minimum intake consistent with health varies throughout a person’s life and among individuals. Adequate intake of dietary fat is particularly important prior to and during pregnancy and lactation. Increasing the viability and consumption of dietary fats is often a priority for overcoming the problems of protein-energy malnutrition. The role of dietary fats and oils in human consumption is one of the most important areas of concern and investigation in the field of nutritional science. The findings of investigations on this subject have wide-ranging implications for consumers, healthcare providers and nutrition educators as well as food producers, processors and distributors. New evidence concerning the benefits and risks associated with particular aspects of dietary fat is constantly emerging in both the scientific literature and the popular media. At the invitation of FAO and the World Health Organization (WHO), an international group of experts in nutrition, public health, food science and technology gathered in Rome in 1993 to consider the latest scientific evidence about dietary fats and oils. Following are the general conclusions and recommendations of the expert consultation on fats and oils in human nutrition (FAO, 1994).

  • For most adults, dietary fat should supply at least 15 percent of their energy.
  • Women of reproductive age should consume at least 20 percent of their energy from fat.
  • Concerted efforts should be made to ensure adequate consumption of dietary fat among populations where less than 15 percent of the dietary energy supply is from fat.

Excessive dietary fat intake has been linked to increased risk of obesity, coronary heart disease and certain type of cancer. The mechanisms by which these are linked are complex, varied and in many instances not clearly understood. Elevated levels of serum cholesterol and low-density lipoprotein (LDL) constitute major risk factors for atherosclerosis and coronary heart disease. The degree of risk for these and other factors may vary according to, inter alia, type and level of fatty acid intakes, percentage of energy from total fat, dietary cholesterol, lipoprotein levels, intakes of antioxidants and dietary fibre, activity levels and health status.

Low fat diets are often lower in cholesterol and higher in antioxidants and dietary fibre. Among adults, there are no nutritional advantages in consuming high fat diets once essential energy and nutrient needs are met.

Anti-nutritional and other factors in groundnut

Lusas (1979) has briefly reviewed various anti-nutritional factors present in groundnut. Trypsin inhibitor activity in groundnuts has been reported as one half to approximately one fifth of the activity found in soybeans. Trypsin inhibitor activity in groundnut is significantly enough to cause pancreatic hypertrophy in rats receiving 15 percent of protein intake from groundnuts. Lectins shown to possess a remarkable array of biological activities have been found in groundnuts. An interesting aspect of the lectins in groundnut is that, roasting of groundnut does not destroy the lectins. Oil seed proteins constitute the most highly allergenic food groups. Groundnuts also have been shown to be highly allergic and shown some hypersensitivity reactions in children. Groundnut oil has been attributed to contain potent anti-inflammatory compounds, however, Calloway, et al. (1971) observed that groundnuts are absolutely non-flatulent. Later on varietal differences were noticed for the differences exist in groundnut in their ability to cause flatulence. In this connection, the consumption of new raw groundnuts is not advisable; groundnuts always should be consumed fried, boiled or roasted. Plant breeding programmes should also focus on developing varieties of groundnut with minimal content of allergenic proteins and antinutritional factors.

Groundnut oil and atherosclerosis

The atherogenecity of groundnut oil is well established, as is the fact that the structure of the component triglycerides of groundnut influences its atherogenecity. It is also atherogenic in the rabbit and rhesus monkeys. This property is not related to the degree of unsaturation of its component fatty acids. Some studies suggest that the atherogenic potency may be due to the triglycerol structure of the groundnut oil. If the atherogenic property is indeed due to the triacylglycerol structure, there seems to exist some genetic potential among cultivars for development of non-atherogenic lines of groundnut.

2.8.4 Secondary products

eating quality

Boiled groundnuts

Newly harvested groundnut pods are boiled or steamed in East and Southeast Asia before they are eaten as a vegetable. On a commercial scale, the boiled pods are dried, packed in airtight plastic bags and sold. Sweet-tasting Valencia types with 3 to 4 seeded pods; tan-rose or tan coloured seeds with high protein and low oil content are the most preferred. Unshelled immature pods can also be boiled in medium brine and eaten fresh or alternately canned and frozen and marketed commercially. At ICRISAT groundnut germplasm was screened for the boiling type of groundnuts with three controls, JL 24, Gangapuri and TMV 3. Six germplasm accessions identified were comparable to JL 24 and Gangapuri for shelling percentage, 100seed mass, oil and protein content, O/L ratios and polyunsaturated/saturated acid ratios. Some lines significantly out yielded TMV 3, which has been released as Khon Kane 60-2 for boiling purpose in Thailand.

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