Reserch Journl of Chemicl Sciences ISSN 2231-606X Physicochemicl Properties nd Ftty cid composition of Diknut (Irvingi Gbonensis) seed oil Abstrct Etong D.I. 1, Mustph A.O. 1 nd Tlet A.A. 2 1 Science Lbortory nd Technology Deprtment, Federl Polytechnic, P.M.B 420, Off, Kwr Stte, NIGERIA 2 Science Lbortory And Technology Deprtment, Federl Polytechnic, Ede, Osun Stte, NIGERIA Avilble online t: www.isc.in, www.isc.me Received 20 th November 2014, revised 12 nd December 2014, ccepted 17 th Decmeber 2014 Nigeri is one of the countries of the world with vriety of oil seeds, therefore the potentil of Nigeri leding Afric, nd the world t lrge, in the re of seeds oil production ws exmined by evluting the ft content, physicochemicl qulities, nd ftty cid content of oil extrcted from diknut (Irvingi gbonensis) seed, bought from Owode mrket in Off locl Government re of Kwr Stte, Nigerin. The ft content of Irvingi gbonensis ws 22.50 + 0.2 %. The chemicl qulities iodine, peroxide, sponifiction, nd cid vlues, free ftty cid, nd unsponifible mtter were nlyzed using stndrd methods, nd the vlues, were found to be 4.50+0.1gI 2 /100g, 1.80+0.1 meq/kg, 187.90+0.3 mgkoh/g oil, 9.40+0.2 mgkoh/g oil, 4.70+0.2% FFA s oleic cid nd 1.50+0.5% respectively. The physicl properties were solid t room temperture, grey yellow in colour, melting point (13+1 o C) nd specific grvity 0.88+0.2kg/dm 3. The oil contined six mjor ftty cid in the following other luric > myristic > steric > plmitic > oleic > linolenic cid. The result revels tht the oil extrcted cn be useful both domesticlly nd industrilly. Keywords: Physicochemicl, extrction, Irvingi gbonensis, oil, ftty cid. Introduction Trees nd shrubs with medicinl nd nutritionl potentils bound in Nigeri. Severl of these plnts hve fruit which hve been identified to be nutritionlly importnt 1. In recent times, the desire to conserve resources spent on importtion of oil for domestic nd industril use gve renewed impetus in the serch for novel sources to complement the trditionl ones. Attention hs therefore been focused on under-utilized locl seeds for possible development nd use. There re severl of these underexploited plnt seeds in Nigerin 2. Diknut (Irvingi gbonensis) belongs to the simrubcee fmily nd is commonly known s Africn mngo. The fruit is yellow when ripe nd the pulp is edible but hs turpentine flvor. The seed rnks s n oil seed nd is used s populr soup thickener in Nigerin 3. The Irvingicee Kernels re prt of the non-timber forest products whose economics nd food importnce pper undenible, but despite their importnce the Irvingicee do not benefit from good vloriztion nd exploittion on lrge scle 4. There re six species of Irvingi in the Congo Bsin, nmely: Irvingi gbonensis, Irvingi grndifoli, Irvingi smithii, Irvingi wombulu, Irvingi excels nd Irvingi robur 5, where only Irvingi gbonensis nd Irvingi wombulu species pper to be well known, nd re the subject of severl trnsction nd some physiochemicl studies 6,7. Mny studies undertken on the nutritionl nd medicinl vlue of Irvingi gbonensis hve been reported 8-10 etc., work on other species include Irvingi smithii 4, Irvingi wombulu 11. Methnolic extrct of Irvingi gbonensis re used in the tretment of bcteril nd fungl infections 12. Seeds oils hve extensive demnds both for humn consumption nd for industril pplictions 13 nd lso hve been rted s the second most vluble commodity in the world trde tody 14. Numerous reserchers 10,13,15-19, mong others hve crried out lot of nlyticl works on seeds primrily becuse of extensive nd incresing demnds for both humn consumption nd numerous industril pplictions. Consequently, there is n incresing need to perpetully serch for oils from non-conventionl sources to ugment the vilble ones nd lso to meet specific pplictions. Attention hs not been focused on under-utilized griculturl foods nd industril products. This study therefore, is designed to serch for oil from non-conventionl sources becuse of the incresing needs for oils both for humn consumption nd industril pplictions. The physicochemicl properties nd ftty cid content of oil extrcted from Irvingi gbonensis ws studied to certin its suitbility for both domestic nd industril pplictions. Mteril nd Methods Sources nd preprtion of smple: The smple diknut (Irvingi gbonensis) seed ws bought from Owode mrket in Off Locl government re of Kwr Stte, Nigeri. The seed ws screened to remove the bd ones nd stones. They were dried to constnt weight in n oven t 60-65 o C for 24hours to Interntionl Science Congress Assocition 70
reduce moisture content nd then grounded using mechnicl grinder, put in n ir tight continer nd stored in desictor for further nlysis. Oil extrction nd nlysis: The seed oil ws extrcted using the continuous soxhlet extrction technique with petroleum ether (40-60 o C) for 5hrs. After removing solvent, using Rotvpor pprtus, the seed oil obtined ws drined under strem of nitrogen nd stored in freezer (-30 o C) for subsequent chemicl nlysis. Stndrd methods were used in ll the nlysis sponifiction vlue 20, unsponifible mtters, nd percentge free ftty cid s oleic cid, nd cid vlued, peroxide vlue, iodine vlue, ft content 21. Specific grvity ws determined using hydrometer 22. Refrctive index ws determined using refrctometer nd colour, colorimeter, smoke point, melting nd setting points 21. Ftty cid composition ws determined s their methyl esters prepred by boron-trifluoride methnol complex method 21 Results nd Discussion The studied chemicl properties of diknut (Irvingi gbonensis) seed oil re shown in tble-1. The ft content ws 22.50+0.2%, lower thn tht reported for cstor seeds (57.33+1.63), coconut seeds (42.00+2.21), diknut (62.80+2.4), groundnut seeds (40.80+0.50), melon seeds, (53.04+1.62), oil bens seeds (52.07+1.45) nd plm kernel seeds (54.18+1.88) 10, different vrieties of tobcco seeds cultivted in Bngldesh rnge 42.29+0.60-45.72+1.20 18, seed kernel of Irvingi smithii of Congo Bsin (54.52+2.61) 4, Cnrium schwenfurthii fruits (36.10%), Blnites egyptic lmonds (48.30%) 23, Dcryodes edulis pulp (29-67.50%) 24, nd Irvingi gbonensis seed kernels from two Congo Brzzville loclities, sibiti (3.69 o S; 13.35 o E) IGS-(34.55-73.82%), nd Ouesso (1.61 o N, 16.05 o E) IGO-(34.28-62.27%) 9. Tble-1 Chemicl properties of oil extrcted from Afric wild mngo (Irvingi gbonensis) seed Chemicl prmeter Composition Iodine vlue (IV) (g1 2 /100g) 4.50+0.1 Peroxide vlue (PV) (meq/kg) 1.80+0.1 Sponifiction vlue (SV) (mgkoh/g.oil) 187.90+0.3 Acid vlue (AV) (mgkoh/g oil) 9.40+0.2 % free ftty cid (FFA) s oleic cid 4.70+0.2 Unsponifible mtter (%) 1.50+0.5 Ft content (%) 22.50+0.2 vlue re mens + stndrd devition of triplicte determintions The sponifiction vlue ws 187.90+0.30 mgkoh/g oil which ws below the rnge reported for Irvingi gbonensis from two loclities in Congo Brzzville (IGO) 189.92+4.6-237.69+72mgKOH/g oil, nd (IGS) 196.32+6.2-277.69+2.5 mgkoh g oil 9. The vlue ws lso lower thn tht reported for Dcryodes edulis pulp oil (201) 25, those of oil extrcted from conventionl oil seeds s soy (189-195), groundnut (187-196) nd cotton (189-198) 26, it ws lso higher thn tht reported for Chrysophyllum lbidum (126.30+3.50), Lndolphi owriensis (42.40+3.00) nd Npolen imperilis (77.06+4.0) but lower thn Dcryodes edulis (191.10+3.80)nd Eleis guineensis (246.60+4.2) 2. However, sponifiction vlue is used to check dultertion 2. The reltives high vlue recorded for this smple is n indiction tht it hve potentil for industril used 16,25. Tble-2 Physicl properties of oil extrcted from Africn wild Mngo (Irvingi gbonensis) seed (Mens, n = 3) Properties Vlue Stte t room temperture (27 + 1 o C) Solid Colour Grey yellow Smoke point ( o C) 78+2 o C Melting point ( o C) 13 + 1 Specific grvity Kg/dm 3 0.88 + 0.2 Setting point ( o C) 25.30 + 1.20 vlues re mens + stndrd devition of triplicte determintion Tble-3 Ftty cid composition of diknut (Irvingi gbonensis) seed(men n=3) Ftty cid % composition Oleic 6.90 + 0.2 Myristic 20.50 + 0.2 Steric 11.40 + 0.1 Linolenic 6.40 + 0.2 Plmitic 10.30 + 0.2 Luric 39.40 + 0.5 vlue re mens + stndrd devition of triplicte determintion Iodine vlue ws 4.50+0.1 gi 2 /100g, confirming the vlues 4.3+0.10-4.80+0.69 for IGO vr nd 4.10+0.01-4.90+0.05 for IGS vr reported for Irvingi gbonensis from two loclities in Congo Brzzville 9. This vlue ws lower compred to tht reported for Cocos nucifer rnge (9.93-10.99) 15,27, Colocynthis citrullus rnge (110.93-111.46) 27. It ws higher thn 2.65-3.45 reported for Colocynthis citrullus, Cucumeropsis edulis nd Prumus mygdlus 28,but lower thn those reported for most non-conventionl plnt seeds in Nigeri nd Congo Brzzville 13,15,29,30, Solnum nigrum L (102.8-103.25), nd Amrnthus hybridus vr. 1 nd 2 (109-112.92) from Congo Brzzvelle 29,30 nd Telferi occidentlis (114.0) nd Citrullus vulgris (114.50) from Abeokut 19. A good drying oil should hve iodine vlue of 180 nd bove 26. Thus, the vlue obtined for these seed (Irvingi gbonensis) clssify it s non-drying oil, s such the seed oil will not be suitble s lky resins for point formultions or used s vrnishes, it my however found use in conjunction with mino resins s finishes for certin pplinces nd in this cse, the oil cn ct s plsticizers. The Interntionl Science Congress Assocition 71
reltive low iodine number of the seed oil my be n indictive of the presence of few unsturted bonds nd low susceptibility to oxidtive rncidity. Peroxide vlue ws 1.80+0.1 meq/kg comprble to C. lbidum (1.8+0.28), N. Imperilis (1.55+0.35) but lower thn E.guinensis (2.12+0.41), L. owriensis (2.80+0.50) nd D. edulis (21.23+1.50) 2. The vlue ws higher thn for Cocos nucifer (0.21) but within the rnge for Colocynthis citrullus (1.53-2.72) 27. The vlue compres fvourbly with the rnge (0.39-7.40) reported for non-conventionl seed oils in Nigerin nd Congo Brzzville 15,19,28,29,30 nd the rnge (0.23-1.80) obtined for the studied conventionl oils in the Nigerin mrkets 27. However, it ws lower thn B. prii (97.50), L. lnceolt (95.0), S. seteger (35.0), D. Microcrpum (150.0), B. Spid (135.0) nd S.birre (25.0) 13. Peroxide vlues re used s indictor for deteriortion of oils. Fresh oils hve peroxide vlues less thn 10 meq O 2 kg -l, 26,while vlues bove 20 indictes rncid tste nd disgreeble odour. The low peroxide vlue of this seed oil indictes low level of oxidtive rncidity of the oil nd lso suggests the presence for high level of ntioxidnt. Acid vlue is used s n indictor for edibility of oil nd suitbility for use in the pint industry. The vlue for these study ws 9.40+0.2 mgkoh/g oil, little bove the rnge 1.20-8.4, mg NOH g -1 reported for Telferi occidentlis, Citrullus vulgris, Colocythis citrullus, (from Akure nd Kno), Pentclethr mcrophyll, Treculi fricn nd Cocos nucifer 15,19,27,28, but compred fvorbly with the rnge (3.74+0.23-25.62+0.29) for most conventionl oils (Rpe seed, soy ben, Wngs, Kings, Turkey, Film, Gino nd Controller oils) sold in Nigerin mrkets 27. The cid vlue of the smple studied, fell within the llowble limits for edible oils 26, therefore the oil is edible. The free ftty vlue ws 4.70+0.2% (s oleic cid) ws higher thn C. lbidum (1.76+0.10), D. edulis (2.78+0.02), N. impreilis (2.60+0.07) but lower thn E. guinesis (7.06+0.01) nd L. owriensis (7.70+0.11) 2, lso higher thn tht reported for three vrieties of tobcco seed oil (1.51-2.30) 18. The oil hs low cid vlue nd corresponding low level of free ftty cid, which suggests low level of hydrolytic nd lipolytic ctivities in the oil, thus the seed oil studied could be good source of rw mterils for industries. The unsponifible mtter ws 1.50+0.50%, which ws comprble to tht reported for three tobcco vrieties 1.39-1.45% 18, but lower thn tht obtined for Psophocrpus tetrgonolobus (1.63%) nd orchid fruits Myristic (1.79%) oil seeds 31. Unsponifible mtter includes hydrocrbons, higher lcohols nd sterols (e.g. Cholesterol, phytosterol) 18. Most oils nd fts of norml purity contin less thn 2% of unsponifible mtter. Tble II showed the physicl properties of oil extrcted from diknut (Irvingi gbonensis) seeds. The oil ws solid t room temperture (27+1 o C) nd grey yellow in colour. The specific grvity ws 0.88+0.2, comprble to the rnge 0.88-0.93 for Cocos nucifer seeds but little below the rnge for Cocoynthis citrullus (0.90-0.92) 27. The specific grvity vlue 0.88+0.2, rnked fvorbly with the rnge of specific grvities 0.81-0.928 reported for other oils, fts nd wxes from common plnt seeds in Nigerin 2, 15, 19. However, the vlue ws low compred to those reported for seeds from Akure, Colocynthis citrullus (1.51), Cucumeropsis, edulis (1.67) nd Prunus mygdlus (1.71) 28. The smoke point ws (78.0+0.2 o C), lower thn tht reported for three vrieties of tobcco seeds oil (214+1.41-230+0.81) 18, soyben oil (250.00+5.77 o C), Blighi spid (220+2.88 o C) 32. Smoke point of ftty mteril is mesure of its therml stbility when heted in contct with the ir. Ftty cids re much less stble thn glycerides, hence the smoke points of ordinry oils depend principlly upon their content of free ftty cids. The melting point ws 13+1.0 o C, significntly lower thn rnge reported for selected Nigerin oil seed (34.0+3.5-72.0+2.6 o C) 10. Since melting point decrese with increse in the degree of unsturtion 10, the lower melting point oils my be useful in the mnufcture of soft nd esy-to- digest mrgrine nd hve be shown to be vluble in the mnufcture of oil crems. The setting point ws 25.30+1.20 o C which ws within the rnge reported for some selected Nigerin oil seeds (4.67+0.30-26.30+1.50) o C 10. Tble-3, presents the ftty cid composition of diknut (Irvingi gbonensis). The following ftty cids were found in the following percentge luric cid (39.40+0.5), myristic cid (20.50+0.3), steric cid (11.40+0.1), plmitic cid (10.30+0.2), oleic cid (6.90+0.2) nd linolenic cid (6.40+0.2). The smple ws richer thn Citrullus lntus seed-linolenic cid (5.29), steric cid (8.33), but comprble in plmitic cid (10.57), nd lower in terms oleic cid (13.65) 17. Severl uthors reported tht Irvingi gbonensis seed kernels oil my be regrded s myristic-luric oil becuse myristic cid ws most bundnt, followed by luric cid 7, but in this study the reverse ws the cse luric ws the most bundnt followed myristic, thus, it my be regrded s luric- myristic oil. Conclusion Tken s whole, in this study, the physicochemicl chrcteristics cn be helpful to identify the qulity of oil nd oil products for possible industril or commercil uses. The oil extrcted, is sturted, source of luric nd myristic cid, which is the chrcteristics of vegetble oils. From the qulity point of view, Irvingi gbonensis seed oil clssified s luricmyristic oils, is comprble to other oils nd cn be utilized for both industril nd domestic purpose. The oil hs considerble high qulity nd good shelf life. Reference 1. Ihekoronye A.I. nd Ngoddy P.O., Integrted Food Science nd Technology for the tropics, Mcmilln Publishers, 82-93 (1985) Interntionl Science Congress Assocition 72
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