9Peanut Oil
Harold E. Pattee
North Carolina State University
Raleigh, North Carolina
1. PEANUT ORIGIN AND HISTORY
In 1753, Linneaus described the domesticated peanut species as Arachis (derived
from the Greek ‘‘arachis,’’ meaning a weed) hypogaea (meaning a underground
chamber) or a weed with fruit produced below the soil. The domesticated peanut
(A. hypogaea) is believed to have originated in an area covered by southern Bolivia
and northern Argentina because of the primitive characteristics associated with the
germplasm from this region (1). Subspecies hypogaea var. hypogaea is the pre-
dominant peanut type found in this area, and Krapovickas (2) hypothesized that
the var. hypogaea may represent the most ancient cultivars because they have the
runner habit, branching patterns, similar to related Arachis species, and no floral
compound spikes.
Additional information now suggests that a second origination event in the area
north of Lima on the west coast of Peru could have been involved in the evolution
of A. hypogaea. Archeological excavations near Casma at Pampa de la Llamas-
Moxeke have recovered peanut shells at a level dated to be approximately
1500 B.C. (3–5), and gold carvings found in ancient tombs just to the north of Pampa
de las Llamas-Moxeke (6, 7) closely resemble the reticulation of the cultivated
types now grown in the Casma area.
Bailey’s Industrial Oil and Fat Products, Sixth Edition, Six Volume Set.Edited by Fereidoon Shahidi. Copyright # 2005 John Wiley & Sons, Inc.
431
As peanut is native to South America, the early Spanish and Portuguese
explorers found the Indians cultivating the peanut along with other food crops. It
was from the tropical and subtropical areas of this hemisphere that the peanut
was disseminated to Europe, to both the coasts of Africa, to Asia, and to the Pacific
Islands (8). The Incas of Peru, who achieved one of the world’s most highly devel-
oped agricultural civilizations, cultivated the peanut throughout the long coastal
regions of Peru. Garcilaso de la Vega describes the peanut as ‘‘another vegetable
which is raised under the ground, called by the Indians ynchic. It is very like mar-
row, and has the taste of almonds.’’ Of its food and medicinal uses: ‘‘If the ynchic is
eaten raw it caused headache, but when toasted it is wholesome, and very good with
treacle; and they make an excellent sweetmeat from it. They also obtain an oil from
the ynchic, which is good for many diseases’’ (8). Just when the peanut was first
purposefully introduced into Europe and into the colonial seaboard of the south-
eastern United States is not documented. However, from this introduction around
the world, the peanut has become a significant agricultural commodity and its oil
a primary ingredient in the culinary process in many countries.
2. GLOBAL
2.1. Peanut Production
The peanut is known by several names throughout the world, such as groundnut and
earth nut, because the seeds develop under the ground. Peanuts are produced on a
significant basis in more than 30 different countries throughout the world. The
worldwide production for 2002 was estimated to be in excess of 31 million metric
tons (MMT) (9). India, China, and the United States were the three largest produ-
cers of peanuts and accounted for over 70% of the world production in 2002. Peanut
production worldwide has undergone significant increases in the last 30 years
(Table 1). In 1972, the average production was 14.4 MMT, 1980 16.0 MMT,
1990 21.6 MMT, and 2000–2002 32.0 MMT. (9, 10). Some of the production
increase was a result of a 22% increase in the area harvested between 1972 and
2002. However, the major factor was the increase in yield from 0.93 MT/ha in
the 1970s to 1.4 MT/ha in 2001/2002. Among the three major producers, India
had a 42% increase in production between the 1970s and 1990s but decreased
16% between the 1990s and 2002. China increased production 179% between
the 1970s and 1990s and another 136% to 2002. The U.S. production increased
15% in the first 20 years and has remained near 1.9 MMT since the 1990s
(9, 10). Total area harvested and production levels in the next tier of eight countries
has averaged approximately 4.63 mha harvested and 4.46 MMT produced across
the 30 years. From the data given in Table 1, the high total area harvested for
this tier of eight countries was 5.38 mha in 1972 with a low of 3.93 mha in
1990. Highest production occurred in 2000 at 5.50 MMT and the lowest in 1990
at 3.46 MMT (Table 1). World exports of peanuts from the producing countries
have only increased 22%, from 1178 MMT in 1972 to 1518 MMT in 2002.
432 PEANUT OIL
TABLE 1. Major Countries and World Peanut Production and Utilization (mha or MMT) Across 30 Years.1
Area TotalDomestic Consumption
Total——————————————————————
Year Country Harvested Production Supply Exports Crushed Food Feed; Seed; Waste Total Distribution
1972 China 1878 2092 2092 42 1018 768 264 2050 2092
1972 India 6990 4092 4342 33 3511 532 266 4309 4342
1972 United States 601 1485 1663 236 386 768 78 1232 1663
1972 Argentina 370 440 457 2 331 46 21 398 457
1972 Brazil 506 590 590 78 401 59 52 512 590
1972 Burma 633 390 390 0 228 142 20 390 390
1972 Indonesia 407 483 483 29 91 340 23 454 483
1972 Nigeria 1220 772 797 284 383 100 30 513 797
1972 Senegal 1100 540 540 7 385 45 103 533 540
1972 Sudan 690 568 568 156 91 210 111 412 568
1972 Zaire 451 230 230 0 81 137 12 230 230
1972 World 18121 14421 16263 1178 8569 4873 1270 14712 16263
1980 China 2339 3600 3600 305 1667 1257 371 3295 3600
1980 India 6801 5005 5205 71 4059 325 650 5034 5205
1980 United States 566 1045 1512 228 202 663 232 1097 1512
1980 Argentina 197 243 282 74 147 12 11 170 282
1980 Brazil 235 310 312 37 196 37 42 275 312
1980 Burma 514 431 431 0 319 91 21 431 431
1980 Indonesia 508 791 806 2 47 682 75 804 806
1980 Nigeria 650 530 530 0 204 220 106 530 530
1980 Senegal 1064 521 521 3 258 101 159 518 521
1980 Sudan 894 707 707 133 377 151 46 574 707
1980 Zaire 480 320 320 0 107 185 28 320 320
1980 World 17508 16040 17805 1113 8507 5697 1989 16193 17805
TABLE 1 (Continued )
Area TotalDomestic Consumption
Total——————————————————————
Year Country Harvested Production Supply Exports Crushed Food Feed; Seed; Waste Total Distribution
1990 China 2907 6368 6369 448 3250 2209 462 5921 6369
1990 India 8309 7514 7514 45 5999 490 980 7469 7514
1990 United States 732 1634 1964 296 313 916 129 1358 1964
1990 Argentina 198 311 341 110 123 31 30 184 341
1990 Brazil 95 157 172 2 50 95 20 165 172
1990 Burma 554 472 472 10 320 96 46 462 472
1990 Indonesia 600 860 1011 0 45 850 93 988 1011
1990 Nigeria 500 250 260 0 80 100 60 240 260
1990 Senegal 914 703 758 4 480 146 93 719 758
1990 Sudan 540 325 325 20 145 135 25 305 325
1990 Zaire 530 380 380 0 129 229 22 380 380
1990 World 19089 21656 23498 1304 11705 7791 2157 21653 23498
2000 China 4856 14437 14437 450 6800 6047 1140 13987 14437
2000 India 8100 5700 5700 100 4300 500 800 5600 5700
2000 United States 541 1481 2138 239 248 988 166 1402 2138
2000 Argentina 251 395 409 177 142 21 19 182 409
2000 Brazil 102 196 216 3 60 125 18 203 216
2000 Burma 530 640 640 12 390 162 76 628 640
2000 Indonesia 650 1040 1178 0 64 1030 70 1164 1178
2000 Nigeria 1210 1470 1475 0 510 670 290 1470 1475
2000 Senegal 1030 1003 1028 9 420 395 149 964 1028
2000 Sudan 550 370 370 5 210 135 20 365 370
2000 Zaire 491 382 382 0 120 232 30 382 382
2000 World 22644 31120 33225 1387 14174 13886 3021 31081 33225
2002 China 5000 14500 14500 500 6950 5950 1100 14000 14500
2002 India 8100 6700 6700 105 5060 600 935 6595 6700
TABLE 1 (Continued )
2002 United States 551 1702 2395 293 292 1090 167 1549 2395
2002 Argentina 200 315 335 160 125 21 19 165 335
2002 Brazil 100 195 215 3 60 124 18 202 215
2002 Burma 530 640 640 12 390 162 76 628 640
2002 Indonesia 650 1000 1219 0 62 1075 68 1205 1219
2002 Nigeria 1230 1510 1515 0 528 685 297 1510 1515
2002 Senegal 750 500 523 5 160 252 85 497 523
2002 Sudan 550 370 370 4 211 135 20 366 370
2002 Zaire 500 390 390 0 132 233 25 390 390
2002 World 22507 31837 34155 1518 14901 13971 3056 31928 34155
1Data extracted from http://www.fas.usda.gov/psd/complete_files/OIL-2221000.csv
However, China alone has increased exports from 42 MMT to 500 MMT during this
same period (Table 1). This increase accounts for nearly one-third of the total world
peanut exports. On the other hand, the African continent countries of Nigeria, Sene-
gal, and Sudan have had a decrease in the exporting of peanuts from a combined
447 MMT in 1972 to 9 MMT in 2002.
2.2. Peanut Utilization
Peanuts are not a crop that can easily be carried over from one year to the next as
noted by a comparison of the production and total consumption values across years
(Table 1). Utilization of the peanut crop can be classified into the general areas of
crushed, food, feed, seed, and waste. In 1972, the primary utilization in 7 of the 11
listed countries was the crushing of peanuts for oil and utilization of the resultant
meal. The United States’ food utilization was more than twice that of the next coun-
try, Indonesia. In the United States, food utilization was nearly twice that of crush-
ing utilization. In 2002, the number of countries having food as the primary
utilization factor had increased to six and the United States and Indonesia were
almost equal in food utilization (Table 1).
2.2.1. Oil Hammons’ (8) review of the origin and early history of the peanut pro-
vides extensive insight into writings of the early Spanish and Portuguese explorers
and the usage of peanuts as an oil source for many purposes. Spanish recognition of
the usefulness of peanut oil is documented by the establishment of an oil mill at
the Mediterranean port of Valencia around 1800 (11). Most authorities credit the
Portuguese with introducing the peanut into African agriculture from Brazil.
West Africa was the primary source of peanut exportation in the nineteenth century.
Brooks (12) provides an overview of the development of the peanut industry in
Africa and peanut exportation from West Africa to other parts of the world. The
first export seems to have been from Gambia to Britain in 1834 involving 213 bas-
kets, but the next year export increased to 47 tons and by the 1840s involved thou-
sands of tons a year. Earliest exports to America were in 1835, and exports to
America dominated the Gambian market from 1837 to 1841. The exportation to
Britain was for crushing, and the dominant reason for American usage was the
pleasing flavor of the roasted peanut.
Development of the European peanut oil industry was stimulated by a worldwide
shortage of fats after the Napoleonic wars, an increase in population, a rise in the
standard of living, and a new working class. As in Britain, French soap and candle-
makers became increasingly dependent on foreign sources of oil supply in the
1830s. Learning of the British peanut imports, French industrialists undertook
experimentation of their own on peanut oil. Jaubert, a Goree trader who had sent
a sample of peanut oil to Marseille in 1833, is credited with initiating the industry
with a shipment of 722 kg of peanuts from West Africa to Marseilles in 1840, when
France reduced the tariff on peanuts (8, 12). Following that shipment, other traders
are reported in 1842 to have brought nearly a 1000 tons of peanuts to Marseilles.
436 PEANUT OIL
Peanut oil production continued to increase, in Europe, throughout the nineteenth
century. By 1899, 17 factories at Marseilles were crushing about 200,000 tons. An
equal volume was being processed in Britain and other European countries (13).
France continued to be a major peanut importer and oil producer, through the
mid-1970s with 331 MMT crushed in 1972. However, by 1980 and 2000, the
crushed level had dropped to 79 and 8 MMT, respectively (10).
Across the last 30 years, the amount of peanuts crushed for oil worldwide has
increased from 7957 to 14,901 MT. (Table 2). Increases in metric tons crushed in
China and India and the decreases in the South America countries of Argentina and
Brazil account for almost 100% of the changes. The oil produced is virtually all
used within the countries of production. It seems appropriate to note that within
Japan, the industrial use of peanut oil has increased from 4 to 14 MMT between
1990 and 2002. Exporting of peanut oil has decreased nearly 42% from 1972 to
2002. Of the 252 MMT of oil exported worldwide in 2002, four countries, Argen-
tina, Nigeria, Senegal, and Sudan, account for nearly 70%.
2.2.1.1. Oil Extraction Hydraulic pressing, expeller, and/or solvent extraction are
the three general methods for extracting oil from the seed. When hydraulic pressing
is used, it is followed by hot solvent extraction for nearly total recovery of the oil.
Expeller extraction relies on friction and pressure within the expeller, which causes
the meal to heat, thus facilitating the oil extraction process. This process removes
approximately 50% of the peanut oil. The remaining oil is extracted using hexane,
which is later removed through an evaporation–condensation system. Solvent
extraction involves petroleum hydrocarbons or other solvents. Solvent extraction
is accomplished in closed systems where oil is removed and solvent reclaimed
for reuse. The efficiency of extraction with hexane, 95% ethanol, or absolute etha-
nol on peanut grits has been reported (14). Extracted oil is refined by deacidification
with sodium hydroxide to neutralize the free-fatty acids, washing with water at
about 82�C to remove the sodium hydroxide, and then bleaching with bleaching
clay at about 100�C under reduced pressure. The refined oil is then deodorized
by heating under vacuum and blowing superheated steam through the oil. Deacidi-
fication and deodorization of peanut oil and other edible oils by dense carbon diox-
ide extraction has been investigated (15). The purpose of the refining process is to
remove nontriacylglycerol components, including free fatty acids, nonhydratable
phosphoacylglycerols, sterols, pigments, glucosides, waxes, hydrocarbons, and
other compounds that may be detrimental to the flavor or oxidative stability of
the refined oil (16).
2.2.1.2. Alternative Oil Extraction Techniques and Seed Treatment The com-
plete removal of organic solvents used for extracting seed oils is mandatory if
the oil is to be used for human consumption. Supercritical fluid extraction
has emerged as an attractive separation technique because it does not introduce
any residual organic chemicals. Supercritical CO2 is the most commonly used
supercritical fluid (17). CO2 is relatively low cost, nonflammable, nontoxic, and
GLOBAL 437
TABLE 2. Major Countries and World Peanut Oil Production and Utilization (MMT) Across 30 Years.1
Oil On TotalDomestic Consumption
Total———————————
Year Country Crushed Production Hand Imports Supply Food Total Exports Distribution
1972 China 1018 254 0 0 254 234 234 20 254
1972 India 3511 1060 0 0 1060 1060 1060 0 1060
1972 United States 386 122 15 0 137 72 72 48 137
1972 Argentina 331 78 2 0 80 0 0 80 80
1972 Brazil 401 112 0 0 112 68 68 44 112
1972 Burma 228 73 0 0 73 73 73 0 73
1972 Indonesia 91 29 0 0 29 29 29 0 29
1972 Nigeria 383 122 0 0 122 11 11 111 122
1972 Senegal 385 128 0 0 128 65 65 63 128
1972 Sudan 91 29 0 0 29 29 29 0 29
1972 Zaire 81 26 0 0 26 22 26 0 26
1972 World 7957 2371 17 401 2789 2325 2337 434 2789
1980 China 1667 417 0 0 417 368 368 49 417
1980 India 4059 1177 0 0 1177 1177 1177 0 1177
1980 United States 202 63 20 0 83 44 44 22 83
1980 Argentina 147 42 0 0 42 0 0 36 42
1980 Brazil 196 62 0 0 62 16 16 46 62
1980 Burma 319 102 0 0 102 102 102 0 102
1980 Indonesia 47 16 0 0 16 16 16 0 16
1980 Nigeria 204 65 0 4 69 69 69 0 69
1980 Senegal 258 83 0 0 83 63 63 20 83
1980 Sudan 377 121 0 0 121 105 105 16 121
1980 Zaire 107 34 0 0 34 33 34 0 34
1980 World 8085 2343 60 319 2722 2410 2411 268 2722
1990 China 3250 813 0 5 818 772 772 46 818
1990 India 5999 1740 0 0 1740 1736 1740 0 1740
1990 United States 313 97 10 5 112 90 90 11 112
1990 Argentina 123 40 0 0 40 5 5 35 40
1990 Brazil 50 14 8 15 37 15 15 18 37
1990 Burma 320 99 0 0 99 99 99 0 99
1990 Indonesia 45 14 5 0 19 13 13 0 19
1990 Nigeria 80 37 0 0 37 37 37 0 37
1990 Senegal 480 153 9 0 162 53 58 99 162
1990 Sudan 145 47 0 0 47 44 44 3 47
1990 Zaire 129 41 0 0 41 40 41 0 41
1990 World 11389 3242 54 302 3598 3274 3292 259 3598
2000 China 6800 2115 0 10 2125 2110 2110 15 2125
2000 India 4300 1245 0 0 1245 1235 1245 0 1245
2000 United States 248 81 14 36 131 111 111 6 131
2000 Argentina 142 42 0 0 42 1 1 41 42
2000 Brazil 60 16 2 0 18 17 17 1 18
2000 Burma 390 123 0 0 123 123 123 0 123
2000 Indonesia 64 20 0 0 20 20 20 0 20
2000 Nigeria 510 230 0 0 230 195 195 35 230
2000 Senegal 420 160 6 0 166 58 58 102 166
2000 Sudan 210 67 0 0 67 22 22 45 67
2000 Zaire 120 38 0 0 38 37 38 0 38
2000 World 14149 4301 32 258 4591 4239 4250 312 4591
2002 China 6950 2175 0 10 2185 2170 2170 15 2185
2002 India 5060 1465 0 0 1465 1451 1465 0 1465
2002 United States 292 93 14 20 127 111 111 5 127
2002 Argentina 125 39 0 0 39 1 1 38 39
2002 Brazil 60 16 0 0 16 15 15 1 16
2002 Burma 390 123 0 0 123 123 123 0 123
2002 Indonesia 62 19 0 0 19 19 19 0 19
TABLE 2 (Continued )
Oil On TotalDomestic Consumption
Total———————————
Year Country Crushed Production Hand Imports Supply Food Total Exports Distribution
2002 Nigeria 528 238 0 0 238 208 208 30 238
2002 Senegal 160 58 5 10 73 10 10 60 73
2002 Sudan 211 68 0 0 68 24 24 44 68
2002 Zaire 132 41 0 0 41 40 41 0 41
2002 World 14901 4513 30 219 4762 4476 4491 252 4762s
1Data extracted from http://www.fas.usda.gov/psd/complete_files/OIL-4234000.csv
easily removed from the oil product by depressurization. However, particle size
does have a significant effect on the extraction rate curves (18–20). CO2 is also
U.S. Food and Drug Administration approved and is generally regarded as a safe
compound.
Food-grade butane in a supercritical, low-pressure, liquefied gas extraction pro-
cedure has also been described for oil extraction from peanuts (21). The extraction
process consists of mixing the liquefied butane with the material to form a slurry.
The liquefied gas and oil are moved to a solvent recovery system where the oil is
removed from the butane. The oil is pumped from the solvent recovery system to a
holding tank, and the butane is then transformed into a gas in the solvent recovery
system and transported back to the butane storage tank for reuse.
Aqueous enzymatic oil extraction is another ecofriendly extraction procedure.
It is based on simultaneous isolation of oil and protein from oilseed by dispersing
finely ground seed in water and separating the dispersion by centrifugation into oil,
solid, and aqueous phases. The presence of certain enzymes during extraction
enhances oil recovery by breaking cell walls and oil bodies (22). For peanuts, a
multistep aqueous extraction process has been described with a recovery of
about 98% (23). More recently, the relatively new technique of enzyme-assisted
aqueous extraction has been applied to peanuts with a reported oil recovery of
86–92% (24).
Microwave treatment, because of its rapid heating of materials, is being explored
in a multitude of crops for enzyme inactivation (25–28), for extraction of natural
products (29), and oil and fat extraction from seeds and food products (30–32).
Microwave treatment of peanut seed prior to press extraction increased oil recovery
approximately 10% at an optimum treatment time of 30 seconds (30). However,
free fatty acid content initially increased with exposure time as well as peroxide
value (30). Research on use of microwave treatment in blanching of peanuts indi-
cated an influence on oil stability depending on treatment conditions (33).
2.2.1.3. Oil Extraction By-Product The byproduct of peanut oil production is
peanut meal, and depending on the methods used, the oil content remaining in
the meal range from about 7% to 1%. Human consumption of peanut meal is neg-
ligible except in India and Argentina (Table 3). The primary use of peanut meal is
animal feed. When peanut meal is used for human or animal consumption, careful
consideration should be given to the quality of the meal. Various oilseeds, edible nuts,
grains, and their derived products are subject to mycotoxin contamination (34),
and these mycotoxins may have a detrimental effect on both human and animal
health (35). Worldwide regulations for mycotoxins have been published (36).
Mycotoxins are generally associated with the protein fraction and are not found
in refined oil because of the processing procedures. Unrefined or lightly refined
oil may contain mycotoxins because of the fine residue particles contained therein.
Meal from edible-grade peanuts with low oil content may be processed into flour
for human consumption. When poor-quality grades are used, poor extraction effi-
ciencies or lack of hygienic conditions exist, and the residue should be used as a
fertilizer.
GLOBAL 441
TABLE 3. Major Countries and World Peanut Meal Production and Utilization (MMT) Across 30 Years.1
On TotalDomestic Consumption
Total————————————
Year Country Crushed Hand Production Imports Supply Exports Food Feed: Waste Total Distribution
1972 China 1018 0 407 0 407 0 0 366 407 407
1972 India 3511 0 1373 0 1373 869 0 504 504 1373
1972 United States 386 1 163 0 164 0 0 161 161 164
1972 Argentina 331 5 136 0 141 85 0 44 44 141
1972 Brazil 401 0 154 0 154 80 0 74 74 154
1972 Burma 228 0 88 0 88 0 0 88 88 88
1972 Indonesia 91 0 35 0 35 0 0 35 35 35
1972 Nigeria 383 6 147 0 153 137 0 16 16 153
1972 Senegal 385 0 148 0 148 135 0 13 13 148
1972 Sudan 91 20 35 0 55 50 0 5 5 55
1972 Zaire 81 0 31 0 31 0 0 31 31 31
1972 World 8098 33 3158 1030 4221 1431 13 2710 2774 4221
1980 China 1667 0 667 0 667 3 0 598 664 667
1980 India 4059 0 1705 0 1705 394 0 1311 1311 1705
1980 United States 202 4 85 0 89 0 0 85 85 89
1980 Argentina 147 7 57 0 64 42 0 8 8 64
1980 Brazil 196 0 72 0 72 46 0 26 26 72
1980 Burma 319 0 121 0 121 0 0 121 121 121
1980 Indonesia 47 0 18 0 18 0 0 18 18 18
1980 Nigeria 204 0 79 0 79 0 0 79 79 79
1980 Senegal 258 0 95 0 95 49 0 46 46 95
1980 Sudan 377 0 145 0 145 75 0 70 70 145
1980 Zaire 107 0 41 0 41 0 0 41 41 41
1980 World 7813 16 3181 488 3685 549 0 3050 3116 3685
1990 China 3250 0 1300 0 1300 160 0 1028 1140 1300
1990 India 5999 0 2520 0 2520 175 5 2340 2345 2520
1990 United States 313 6 136 0 142 35 0 103 103 142
1990 Argentina 123 0 48 0 48 38 3 7 10 48
1990 Brazil 50 0 20 0 20 3 0 17 17 20
1990 Burma 320 0 105 0 105 10 0 95 95 105
1990 France 0 0 0 253 253 3 0 250 250 253
1990 Indonesia 45 16 17 132 165 0 0 145 145 165
1990 Nigeria 80 0 28 0 28 0 0 28 28 28
1990 Senegal 480 34 183 0 217 166 0 22 22 217
1990 Sudan 145 0 56 0 56 52 0 4 4 56
1990 Zaire 129 0 50 0 50 0 0 50 50 50
1990 World 11350 61 4518 717 5296 626 8 4478 4610 5296
2000 China 6800 0 2660 0 2660 15 0 2645 2645 2660
2000 India 4300 0 1810 0 1810 20 10 1780 1790 1810
2000 United States 248 2 104 0 106 5 0 99 99 106
2000 Argentina 142 5 62 0 67 50 3 5 15 67
2000 Brazil 60 0 24 0 24 1 0 23 23 24
2000 Burma 390 0 123 0 123 10 0 113 113 123
2000 Indonesia 64 8 24 7 39 0 0 33 33 39
2000 Nigeria 510 0 163 0 163 0 0 163 163 163
2000 Senegal 420 3 190 0 193 144 0 44 44 193
2000 Sudan 210 0 81 0 81 76 0 5 5 81
2000 Zaire 120 0 46 0 46 0 0 46 46 46
2000 World 14139 22 5254 255 5531 274 35 5204 5239 5531
2002 China 6950 0 2719 0 2719 10 0 2709 2709 2719
2002 India 5060 0 2128 0 2128 50 10 2068 2078 2128
2002 United States 292 2 127 0 129 5 0 122 122 129
2002 Argentina 125 0 55 0 55 47 3 5 8 55
2002 Brazil 60 0 24 0 24 1 0 23 23 24
2002 Burma 390 0 123 0 123 10 0 113 113 123
TABLE 3 (Continued )
On TotalDomestic Consumption
Total————————————
Year Country Crushed Hand Production Imports Supply Exports Food Feed: Waste Total Distribution
2002 Indonesia 62 5 23 0 28 0 0 26 26 28
2002 Nigeria 528 0 169 0 169 0 0 169 169 169
2002 Senegal 160 5 68 0 73 63 0 10 10 73
2002 Sudan 211 0 81 0 81 75 0 6 6 81
2002 Zaire 132 0 51 0 51 0 0 51 51 51
2002 World 14901 17 5502 244 5763 222 37 5495 5532 5763
1Data extracted from http://www.fas.usda.gov/psd/complete_files/OIL-0813200.csv
3. ENVIRONMENTAL AND GENOTYPE EFFECTSON THE COMPOSITION PEANUTS
Major factors that influence the oil and other composition components of the peanut
include cultivar and maturity (37) as well as the environmental production condi-
tions of light, temperature, water stress, soil constituents, atmospheric constituents,
herbicides and insecticides, physical damage, and pest attack (38). In the four major
U.S. market-types (runner, virginia, valencia, and spanish), total oil content varies
from 44% to 56% (37, 39, 40). Information on the environmental and genotypic
effects on oil and fatty acid composition in peanuts is available (40, 41). The effects
of production environment on oil composition of varieties grown in Australia (42),
India (43, 44), and the United States (45–49) have been reported. In maturity stu-
dies, the total oil (as a percentage of dry weight) increased significantly and then
decreased slightly (50, 51). The most rapid changes in oil percentage occurred in
early maturity stages and corresponded to the time of very rapid increases in seed
dry weight (45, 51–54). As the peanut oil content increases across maturity, there is
a concurrent change in fatty acid composition (45). Mature seeds contain more stea-
ric and oleic acids and less arachidic, behenic, and lignoceric acids than immature
seeds. The oleic/linoleic (O/L) ratio also increases with maturity (41, 45). Develop-
ment of new high oleic acid peanut cultivars will be discussed in the next section.
Oil content and fatty acid composition have been studied in aboriginal varieties
of Arachis hypogaea subsp. hypogaea and subsp. fastigiata. These varieties are
important because they contain germplasm that can be used to increase the varia-
bility in the genetic base of the cultivated varieties (55, 56). The A. hypogaea subsp.
hypogaea var. hypogaea cultivars were higher in oleic acid concentration than the
A. hypogaea subsp. fastigiata var. fastigiata, var. aequatoriana, and var. peruviana
cultivars in sources from Peru (57) and Bolivia (58). Similar results were also
obtained from Mexican landrace lines of A. hypogaea subsp. hypogaea var. hirsuta
(59). In contrast, a survey of 16 wild species of Arachis found that the wild species
had higher levels of linoleic acid in comparison with the Arachis hypogaea geno-
types (60)
4. MODIFICATION OF OIL CHARACTERISTICS THROUGHBREEDING
Modification of fatty acid composition has been a particular goal of breeding pro-
grams because oil quality, fatty acid composition, and protein composition are
highly heritable traits. One of the keys to successful progress in a breeding program
is the availability of rapid, efficient screening systems. Some of the methods for
rapid screening are measurement of the iodine value (IV) by the oil’ refractive index
(61), estimation of the seed oil content by its specific gravity (62), and estimation of
seed fatty acid composition by use of a small tissue fraction and analysis through
direct transmethylation (63), which improves on the individual seed analysis meth-
od (64). Methods of peanut improvement through breeding programs have been
MODIFICATION OF OIL CHARACTERISTICS THROUGH BREEDING 445
discussed in detail (65–68). Most peanut genotypes have 36–67% oleic acid (O),
15–46% linoleic acid (L), and O/L ratios between 1.19 and 4.46 (69–72). While
surveying peanut genotypes for oil quality, it was found that two closely related
experimental lines had 80% oleic acid and 2% linoleic acid (O/L ¼ 40) with an
IV of 74 (71). This naturally occurring mutation may have resulted from a mutation
of aspartate at position 150 to asparagine in the cDNA that reduced oleoyl-PC desa-
turase activity (73). Initial oxidative stability studies were done comparing
extracted oil from the experimental high-oleic line with that of an isogenic sister
line with normal fatty acid composition (74). The results indicated that the high-
oleic peanut oil had a greater oxidative stability than the normal-oleic oil. These
experimental lines have been used in breeding programs to develop cultivars
with high O/L ratios (75–79). Cultivars having these high O/L ratios do not have
significant differences in oil content (80) nor do they have significant differences in
color, aroma, flavor, or texture (81, 82). It is characteristic of these high oleic acid
lines to have a linoleic acid content of 4% or less. High oleic roasted peanut seed
have a more stable roasted peanut attribute after 6 weeks storage at 22�C, and their
estimated shelf life is approximately two times longer than that of seed from a nor-
mal-oleic variety Florunner (83). Comparison of flavor stability in high-oleic and
normal oleic roasted peanut seed during storage at low relative humidity (84)
or �20�C (85) indicated that the high-oleic sources had better flavor quality and
stability. Use of high oleic oil in roasting of peanuts resulted in slight increases
in shelf life as measured by oxidative stability index (OSI) and peroxide value
(86). The OSI decreased over storage time, but the differential between high-oleic
and normal roasting oils was maintained throughout the storage period. The stabi-
lity of high-oleic peanut, sesame, and soybean blends in comparison with normal-
oleic peanut, sesame, and soybean blends has also been investigated (87), as has the
effect of the high-oleic trait on roasted peanut flavor heritability (79, 88).
5. OIL COLOR
Color is an important quality parameter of edible oil, both in the refining process
and in the marketplace. It is frequently monitored in the product line according to
some commercial standards to maintain a consistent quality. Each oil has its own
characteristic color primarily because of naturally occurring polyphenolic pig-
ments, gossypol, chlorophyll, and carotenoids (89). Therefore, oil color is often
specified according to both market and trade rules established by various associa-
tions. Peanut oil of the first grade for cooking should not exceed 2 Lovibond red
with fixed Lovibond yellow 20 according to Chinese national standard GB5525-
85, and for salad use, it should be no more than 1.5 Lovibond red with fixed Lovi-
bond yellow 15 (90). The Lovibond method, American Oil Chemists’ Society
(AOCS) Method Cc 13e-92 (91), is practiced primarily outside the United States
and Canada (90), and AOCS Method Cc 13e-45 or Wesson method is used through-
out the Americas (92). Introduction of automated colorimeters made possible the
replacement of the manually operated visual color instrument. An international
446 PEANUT OIL
collaborative study was conducted to establish a broad-scale correlation between an
automated colorimeter (Tintometer Model PFX 990 (The Tintometer Ltd)) and the
official visual colorimeter (Tinometer Model AF710) (93). The automated col-
orimeter was concluded to be an appropriate alternative. Recently, digital image
analysis has been proposed as an alternative method to the visual Lovibond method
(90). The light yellow color of peanut oil is caused by ß-carotene and lutein (94). As
peanuts mature, a distinct lightening of the oil color can be observed (95). This
lightening of oil color has been suggested as a method to assess maturity (96). How-
ever, because peanut oil color is affected by factors, such as water stress and rate
of curing in addition to maturity (97), this method was replaced by other maturity
evaluation methods (98, 99).
6. PEANUT OIL EVALUATION AND COMPOSITION
Crude peanut oil has a nutlike flavor, which is removed by refining (14). Flavor
quality ballots for oil quality have been described (100) and incorporate separate
ballots for grading and flavor intensity. The flavor quality ballot only describes
the flavor characteristics and does not include the suspected cause or process of
any off-odors (101). Lexicons of roasted peanut flavor terms are available, and
the origins of these flavor terms have been discussed (102). Although there is no
U.S. standard of identity per se, peanut oil must be suitable for human consumption
and conform to the identity characteristics defined by the Codex Alimentarius
Commission (103). The various chemical and physical characteristics for peanut
oil are given in Table 4.
Heat of fusion, or latent heat, is the quantity of heat required to change 1 g of
solid to a liquid with no temperature change. This latent heat increases with increas-
ing molecular weight. Heat of combustion is the amount of heat produced by com-
bustion of 1 kg of oil (104). The heat of combustion increases with the chain length
of the fatty acids for both monoacylglycerols and triacylglycerols (107).
The Hehner value expresses the percentage of water-insoluble fatty acids plus
unsaponifiable matter in an oil or fat (105). This method is of greatest value in test-
ing butterfat purify. Like most vegetable oils, peanut oil has a higher Hehner value
than butterfat (108). Lipids with soluble fatty acids will have lower Hehner values
than those with a greater proportion of high-molecular-weight fatty acids. The IV,
or Wijs iodine number, is the number of grams of iodine absorbed under standard
conditions by 100 g of fat. Peanut oil’s IV of 82–107 indicates it is more saturated
than corn, cottonseed, or linseed oil but is less saturated than coconut, palm, or
butter oil (37). Oil from the high oleic peanut varieties has an IV usually between
73 and 77 (41).
Peroxide value is the measure of reactive oxygen content of a fat in terms
of milliequivalents per 1000-g fat, following AOCS method Cd 8-53 or AOAC
Method 965.33 (109). Elevated peroxide values indicate that lipid oxidation has
taken place (110). Free fatty acids can serve as substrates for lipoxygenase and per-
oxidase (111), both of which are inactivated during heating (112). Once the cell
PEANUT OIL EVALUATION AND COMPOSITION 447
structure is disrupted, lipoxygenase reacts with linoleic, linolenic, or arachidonic
acid [either as the free acid, triacylglycerols, or methyl or ethyl esters (113)] to
form hydroperoxides. Hydroperoxides can undergo further decomposition to
form pentanal and hexanal, both of which are detectable by headspace analysis
(114). These oxidation products are correlated with reduced flavor scores (100)
and cardboard and painty defects (100). Although the peroxide value is used as
an indicator of oil oxidation, the Kreis test was found to be a better predictor of
oxidation than the peroxide value for peanut oil (115).
The Plenske value and Reichert–Meissel values are indicators of steam-volatile
water-soluble (butyric, caproic, and caprylic) or water-insoluble (capric and
lauric) fatty acids, respectively (37). These tests were designed for detecting
TABLE 4. Characteristics of Peanut Oil.
Characteristic Value Reference
Acetyl value 8.5–9.5 37
Acid value (maximum)
Refined 0.6 mg KOH/g oil 103
Cold Pressed 4 mg KOH/g oil 103
Calculated gums (phospatides x 32) 0.35% 104
Color (Lovibond, maximum) Yellow 16–25; 2.0 red 37
Color (visual) Light yellow 37
Flavor and odor
Refined Bland 14
Cold Pressed Shall be characteristic of the natural product 103
Free from foreign and rancid odor or taste
Heat of fusion (unhydrogenated) 21.7 cal/g 37
Heating value 40.4 mJ/kg 104
Hehner value 95–96 105
Insoluble Impurities (% maximum) 0.05 103
Iodine no. (Wijs) 86–107 103
Kinematic viscosity (21.1�C) 70.7cSt 104
Melting point 0–3�C 106
Melting point of the fatty acids 22–30�C 106
Moisture and volatiles 0.23% 106
Peroxide value (maximum)
Refined 10 meq peroxides O2/kg oil 103
Cold Pressed 15 meq peroxides O2/kg oil 103
Polenske value 0.5 37
Refractive index (nD40�C) 1.46–1.465 103
Reichert-Meisl value 0.5 37
Saponification number 187–196 103
Smoke point (minimum) ~226.4�C 14
Specific gravity (20�C) 0.912–0.920 103
Specific heat (Cp, liquid oil) 0.4914 þ 0.004 T (�C) 107
Surface tension 35.6 mN/m 104
Thiocyanogen value 0.5 37
Titer 26–32�C 37
Unsaponifiable lipids 0.40% 104
448 PEANUT OIL
low-molecular-weight fatty acids in oil and adulteration in butterfat (106). Butterfat
has a Reichert–Meissel value of 17–34.5 (110).
The thiocyanogen value (TV) is a measure of the amount of the reagent absorbed
by 1 g of fat. GLC methods have largely displaced this method for determining the
content of oleic, linoleic, and linolenic acids when IV’s are determined (116).
Methods for calculating fat composition using the IV and TV have been discussed
(110).
For soap making, the melting point of the fatty acids (titer value) is an important
parameter (117). The titer value for peanut oil is lower than that for cottonseed oil
(30–37�C), cocoa butter, and animal fats and oils (118) but is higher than that for
corn (14–20�C) and/or linseed oil (19–21�C) (37).
The unsaponifiable matter is largely sterols and methylsterols (119, 120).
Detailed compositional analysis of the unsaponifiable fraction will be discussed
under the sterol subheading.
Before the development of gas chromatography and high-pressure liquid chro-
matography, the presence of peanut oil (as an olive oil adulterant) could be detected
because peanut oil contains about 5% arachidic acid. Arachidic acid is insoluble in
cold alcohol unlike stearic and palmitic acids (110). Methods for the detection of
arachidic acid include the Bellier, Evers, Evers–Bellier, and Renard tests (110,
121). Arachidic acid is predominant in the lecithin and cephalic fractions of peanut
oil (122). Detection methods for toxic oils as an adulterant in edible oils such as
peanut oil have been reviewed (123, 124).
Advances in instrumentation have brought about proposals of new methods for
oil content and quality measurements. Near-infrared transmittance spectroscopy has
been used as a nondestructive method for the determination of oil content in pea-
nuts (125). Fourier-transform infrared methodology has been applied as a quality
control method in determining peanut oil in high fat products such as peanut butter
(126) and monitoring changes in peanut oil and other oils under oxidative condi-
tions (127). Although Fourier-transform–Raman spectroscopy has been applied to
the classification of fats and oils including peanut oil (128), differential scanning
calorimetry has been used to follow changes in the thermal characteristics of frying
oils such as peanut oil (129).
6.1. Fatty Acids
Peanut oil is composed of mixed acylglycerol of approximately 80% unsaturated
and 20% saturated fatty acids (37). In mature peanuts, the oil is 96% triacylglycerol
(130) with the main fatty acids being palmitic, oleic, and linoleic (40). Other fatty
acids found in peanut oil are arachidic, 11-eicosensoic, behemic, and lignoceric
acids. The long-chain fatty acids are usually found at about or slightly less than
2%. The percent of free fatty acids in peanut oil varies between 0.02% and 0.6%
(131). Lipase hydrolysis of triacylglycerols into free fatty acids and glycerol occurs
before germination (132) and during adverse storage (97). Consequently, high free
fatty acid values indicate poor handling, immaturity, mold growth, or other factors
that lead to triacylglycerol hydrolysis (133).
PEANUT OIL EVALUATION AND COMPOSITION 449
With maturation, the percentage of oleic acid increases while linoleic acid per-
centage decreases slightly (41, 45). Oxidative stability of peanut oil is highly cor-
related with the ratio of oleic acid to linoleic acid (134); thus, oil stability is
correlated with maturity. Cooler production climates lower the O/L ratio, resulting
in oil with a shorter shelf life. Other environmental conditions, such as drought
(135), and dry-land farming (45) will also lower the O/L ratio, and selecting soils
with a more basic pH and increasing iron while avoiding overfertilization will
increase the O/L ratio (136). Application of growth regulators has been shown to
reduce the O/L ratio (137, 138), decrease the eicosenoic acid content (137), and
increase oil yield (139). Herbicides have been shown to have a slight effect on
the oleic and linoleic acid content (137, 140). Fatty acid composition of peanut
oil can also be widely influenced by cultivar source (141, 142). Varietal variations
in fatty acid composition are summarized in Table 5 and by Young (143). It is
again important to indicate that in high oleic acid peanut cultivars, the general char-
acteristic is a linoleic acid content of 4% or less (41).
6.2. Triacylglycerol Structure
Interest in the triacylglycerol structure of peanut oil arose from observations that
peanut oil showed atherogenic effects in rabbits and other animals (144–147).
This atherogenicity has been attributed to the triacylglycerol structure of peanut
oil (148–150) because treatment of peanut oil with a base, to bring about randomi-
zation, reduced the atherogenicity to that of corn oil (151). However, the results of
the Kritchevsky studies (148, 149, 151) have been questioned (40) on the basis that
they did not include other vegetable oils for comparison and a lack of data for
appropriate statistical analysis. More recent studies (152–155) have shown that pea-
nut oil and peanut product-based diets produce a reduction in total and LDL cho-
lesterol.
Various studies have identified anywhere from 18 to 84 different triacylglycerol
species in peanut oil (149, 150, 156, 157). Although many different triacylglycerol
species have been identified, the data are conclusive concerning a nonrandom dis-
tribution of fatty acids in the sn-1, -2, -3 positions of the triacylglycerols. As the
TABLE 5. Reported Fatty Acid Composition Ranges of Peanut Oil.
Fatty Acid Percentage
Reference 102 135 141
Palmitic 8.0–14.0 7.4–12.5 5.3–10.4
Stearic 1.0–4.5 2.7–4.9 2.2–4.4
Oleic 35.0–69 41.3–67.4 52.8–82.2
Linoleic 12.0–43.0 13.9–35.4 2.9–27.1
Arachidic 1.0–2.0 1.2–1.9 1.1–1.8
Eicosenoic 0.7–1.7 0.7–1.4 0.7–2.4
Behenic 1.5–4.5 2.1–3.6 2.2–3.9
Lignoceric 0.5–2.5 0.9–1.7 1.0–1.9
450 PEANUT OIL
composition of the peanut oil changes, so does the spatial arrangement of the tri-
acylglycerols (158). The predominate triacylglycerol species are OOL, OOO, OLL,
POL, and POO (O ¼ oleic, L ¼ linoleic, P ¼ palmitic) (157). Oleic acid is present
in high concentration at all three positions, and linoleic acid is found primarily in
the sn-2 position. The shorter chain length saturated fatty acids, palmitic and stea-
ric, are mainly located in the sn-1 position and less in the sn-3 position. The longer
chain length saturated fatty acids, arachidic, behenic, and lignoceric, are located in
the sn-3 position. Eicosenoic acid is also frequently located in the sn-3 position
(156, 157, 159). Peanuts are grown under many different environmental conditions,
and such environmental differences can also influence the composition of the pea-
nut oil and the triacylglycerol species (160). Because peanut triacylglycerol struc-
ture and composition and total oil composition are affected by environmental
factors and diverse genetic background (158), their atherogenic potency (148)
and oxidative stability (74) may also be affected by these conditions.
6.3. Phospholipids
The phospholipid content of peanut oil can vary from 0.6% to 2% depending on the
maturity of the peanuts from which the oil is extracted (161). The major phospho-
lipids of peanut oil are phosphatidic acid (PA), phosphatidylcholine (PC), phospha-
tidylethanolamine (PE), phosphatidylglycerol (PG), and phosphatidylinositol (PI).
The composition of the phospholipid fraction is influenced by maturity and by
the postharvest stresses to which the peanuts are subjected (162). The concentra-
tions of PA, PE, PC, and PG were higher in immature seed, and PI was lower,
when compared with mature seed. The concentration of all phospholipids except
PG increased when peanuts were subjected to a curing temperature of 40�C.
When the peanuts were frozen before curing, a significant increase was observed
in PA and PG, whereas PC and PE decreased in comparison with the controls. Oxi-
dative stability of peanut oil has been postulated for some time to be caused by con-
stituents in addition to the linoleic acid content and tocopherol content (163). More
recently, it has been reported that phospholipids act in a synergistic manner with
tocopherols in lengthening the onset of the induction period of lipid oxidation
(164, 165). The degree of unsaturation of the acyl fatty acid chain has an added
effect on the length of the induction period (164). PE and PI appeared to be
more effective than PC in increasing oil stability (164). The usually high concen-
tration of PC in raw peanut oil contributes to the efficiency of the degumming pro-
cess during refining (166). A critical concentration of PC is needed to ensure that a
gum is formed for the removal of the phospholipids.
6.4. Tocopherols
Tocopherols are considered a moderate antioxidant in the peanut oil. The Codex
Alimentaris standard for tocopherols in peanut oil (103) indicates a range of
48–373 mg/kg for alpha-tocopherol, 0–140 mg/kg for beta-tocopherol, 88–389
mg/kg for gamma-tocopherol, and 0–22 mg/kg for delta-tocopherol. Total tocopherol
PEANUT OIL EVALUATION AND COMPOSITION 451
content ranges from 130 to 1300 mg/kg. Tocotrienols should not be detectable in
peanut oil. Tocopherol content in the oil can be affected by variety, production loca-
tion within the United States, maturity, and temperature of seed storage (37). Sto-
rage of peanut seed at 38�C vs. 22�C reduced alpha-tocopherol content by about
25%. A multiyear study on oil composition of peanuts exported from Argentina,
China, and the United States found tocopherol content to be the highest in the
U.S. source and lowest in the China source (167). Alpha- and gamma-tocopherols
were found to be the most abundant forms. Tocopherol form influences the antioxi-
dant capacity. Gamma- and delta-tocopherols were found to be significantly better
antioxidants than alpha-tocopherol, in that either of the first two would protect oil
approximately twice as long as a similar concentration of the latter (168). In unpro-
cessed expeller-pressed peanut oil, the tocopherol content did not affect antioxidant
activity when the oil was stored at 2% relative humidity (RH) vs. 91% RH (169).
Total tocopherol content in oil may be reduced during the degumming and the
bleaching processes by 20% and 60%, respectively (170). Peanut oil tocopherols
are also lost during frying when peanut oil is used as a cooking oil (171). Tocophe-
rols are also known as vitamin E; thus, peanut oil can serve as a good source for this
vitamin particularly when the oil is unrefined. The vitamins found in peanuts are
given in Table 6.
TABLE 6. Vitamin Content of Peanuts (Units per 100 g Dry
Weight) (37).
Constituent Units
Fat soluble
Vitamin A 26 I.U.
Carotene (provitamin A) Trace (<1 ug)
Vitamin D ND
Vitamin E 26.3 –59.4 mg/100-g oil
Alpha-tocopherol 11.9 –25.3 mg/100-g oil
Beta-tocopherol 10.4 –34.2 mg/100-g oil
Delta tocopherol 0.58 –2.50 mg/100-g oil
Vitamin K ND
Water soluble
B-Complex
Vitamin B1—Thiamine 0.99 mg
Vitamin B2—Riboflavin 0.14 mg
Vitamin B6—Pyridoxine 0.30 mg
Vitamin B12—Cyanocobalamin ND
Niacin—Nicotinic acid 12.8–16.7 mg
Choline 165–174 mg
Folic acid 0.28 mg
Inositol 180 mg
Biotin 0.034 mg
Pantothenic acid 2.715 mg
Vitamin C 5.8 mg
ND–Nondetectable.
452 PEANUT OIL
6.5. Sterols
Sterols are a minor constituent of peanut oil, varying from 0.09% to 0.3% (172).
Refining can remove nearly 61% of the sterol content. The Codex Alimentaris stan-
dards for desmethysterols in peanut oil (103) are given in Table 7. Detailed analyzes
of the unsaponifiable lipid fraction from peanut oil can be found in the literature.
Analysis of the unsaponifiable fraction of Nigerian peanut oil indicated the total
fraction to be about 0.4%, and when subdivided by TLC, the fractions were sterols
60%, hydrocarbons 27%, the remainder aliphatic alcohols, and other minor compo-
nents (119, 120). Beta-sitosterol comprised 64% and campesterol 15% of the sterol
fraction. The major triterpene alcohols included 24-methylenecycloartanol at 46%
and cycloartanol at 33%. A more recent report on the separation of the unsaponifi-
able components of Madagascar peanut oil (173) indicated that the sterol fraction
was composed of 72% beta-sitosterol and about 17% campesterol. The 4-alpha-
methylsterol fraction was primarily composed of citrostadienol (20%), obtusifoliol
(17%), gramstisterol (15%), and cycloeucalenol (14%). The triterpene alcohol frac-
tion was composed of 14-methyl-cycloeucalenol (42%), cycloartenol (22%),
cycloartanol (15%), and lupeol (10%). Use of peanut oil as frying oil also results
in the loss of phytosterols (174). The major sterol component, beta-sitosterol, has
recently been shown to inhibit cancer growth (175) and may offer protection from
colon, prostate, and breast cancer.
7. USES
Peanut oil is used mainly for edible purposes in the preparation of shortening, mar-
garines, and mayonnaise, as a cooking and frying oil and as a salad oil. As indicated
previously, the primary use of edible peanuts outside North America is the produc-
tion of peanut oil (Tables 1, 2), and the oil may be hydrogenated into vanaspati, an
Indian analogue to margarine (176). Because of the high smoke point (229.4�C),
TABLE 7. Codex Alimentarius Standard Levels
of Desmethylsterols in Peanut Oil (102).
Constituent % Total Sterols
Cholesterol ND–3.8
Brassicasterol ND–0.2
Campesterol 12.0–19.8
Stigmasterol 5.4–13.2
Beta-sitosterol 47.4–69.0
Delta-5-avenasterol 5.0–18.8
Delta-7-stigmastenol ND–5.1
Delta-7-avenasterol ND–5.5
Others ND–1.4
Total sterols (mg/kg) 900–2900
ND—Nondetectable, defined as � 0.05%.
USES 453
refined peanut oil is often used in deep-fat frying (14), but hydrolysis of acylglycer-
ols into free fatty acids during frying leads to a decrease in smoke point (107). For
both frying and as a salad oil, peanut oil is considered to be superior to soybean oil
and develops fewer flavor defects with long-term use (177). Peanut oil is considered
to be superior in the manufacture of pourable dressings because of its ability to hold
solids in suspension longer (178). However, because peanut oil solidifies at 0–3�C,
it does not meet the definition for salad oil, which must remain clear after 5.5 hours
of immersion in an ice bath at 0�C (179). A nonedible use of peanut oil as a diesel
fuel has been investigated (180–183), but it is more expensive than conventional
No. 2 diesel fuel and has the added drawbacks of lower heating value, greater sur-
face tension, greater viscosity, and greater density (104).
7.1. Peanut Oil as a Protectant
In developing countries, there is a need for economical and locally available mate-
rials that can be used as a protectant, particularly as a seed protectant. In Nigeria,
peanut oil is recommended for control of rice weevils (Sitophilus oryzae L.) (184)
and as a protectant of maize from damage by the maize weevil (Sitophilus zeamais
Motsch.) (185). Protection can last up to 180 days. Control of Sitophilus granaries
L. with peanut oil was effective for up to 90 days of storage for wheat (186). The
use of peanut oil for the control of Callosobruchus maculates (F) in cowpea grain
has been reported (187) and its mode of action investigated (188, 189). Applications
of the method have been reported from Gambia (190), Senegal (191), Nigeria, and
Colombia, South America (192). In India, peanut oil is used as a protectant against
Callosobruchus chinensis L. in chickpea (Cicer arietinum L.) (193). In Sahel, pea-
nut oil is used for protecting leguminous tree seeds against seed beetles (194). Other
protectant applications are its use as a protectant against infestations of Cryptolestes
pusillus and Rhyzopertha dominica in stored grains, such as maize and sorghum
(195). Application of peanut oil to apples as a postharvest treatment has been shown
to reduce superficial scald (196). Peanut oil has also been evaluated for control of
the parasitic tracheal mite [Acarapis woodi (Rennie)] in colonies of the honeybee
[Apis mellifera (L.)] (197).
8. DIETARY ASPECTS
Dietary aspects of high fat content products such as peanuts and peanut products
and of peanut oil are often in question. One point is the high atherogenic potential
of peanut oil, which has been attributed to its triacylglycerol structure (148–150),
because treatment of the oil with a base to bring about randomization reduced the
atherogenicity to that of corn oil (151). Another study has suggested that the lectin
in peanut oil may significantly contribute to its atherogenic properties (198). Con-
tinued human epidemiological studies have shown a 30–50% reduction in cardio-
vascular disease in individuals who ate nuts, including peanuts, four to five times a
week (199–201). Another human subjects study found that the use of high oleic
454 PEANUT OIL
acid peanuts as the fat source in a low-fat–high-monounsaturate diet produced sig-
nificant positive changes in blood lipids in postmenpausal women, including reduc-
tion of total cholesterol from 264 to 238 mg/dl (202). Additional evidence for the
benefits of a diet high in monounsaturated and polyunsaturated fats and low in satu-
rated fat on body function is found in a recent study in which the subjects consumed
one of five diets: a low-fat diet, one including olive oil, one including peanuts and
peanut butter, one including peanut oil, and a typical American diet. Results indi-
cated that the diet including peanuts and peanut butter, the one including peanut oil,
and the diet including olive oil (all low in saturated fat and cholesterol, and high in
monounsaturated fat) lowered total cholesterol and LDL cholesterol. Further, each
of these three diets lowered triacylglycerol levels, but they did not lower the
beneficial HDL cholesterol (203, 204). Peanut oil because of its beta-sitosterol
may inhibit cancer growth (175) and may offer protection from colon, prostate,
and breast cancer. Snacking on peanuts or peanut products has a satiety effect
that enables individuals to control hunger without leading to a weight gain (205).
9. ALLERGENICITY
The allergenicity of peanuts is well documented (206). Because peanuts are among
the most potent allergenic foods, based on the prevalence of peanut allergy and the
frequency of reported severe adverse reactions (207–209), peanut oil has been the
most thoroughly studied (210). It has been shown that the most peanut-allergic indi-
viduals can safely consume refined peanut oil, whereas unrefined oil can provoke
reactions in some of the same individuals. However, some other studies report cases
of allergic individuals reacting to peanut oil that presumably had been refined (211,
212). This has led to a debate about the safety of refined oils and specifically
whether to label each oil individually because of the potential risk of allergenicity.
It has been suggested that the discrepancy between these observations was caused
by processing differences (210). It was further suggested that there needs to be a
standardized and validated methodology for measuring the protein content and
immunoreactivity of the residual protein in the peanut oil. Such a standard metho-
dology can then be used to maintain process specifications. Thresholds of reactivity
to allergens also need to be established to assess fully the risk from very small
amounts. It has been questioned whether high oleic acid peanuts differ in their aller-
genic properties from normal peanuts. Investigation of this question concluded that
a high content of oleic fatty acid has no effect on peanut allergenicity (213).
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