Key Words: Temperature, Pretreatments, Anti nutrients, Nutrients,Peanut
Christopher J. Etti1 , Linus Ashiwel Adie2
Effects of Pretreatments and Drying Methods on Some Anti-nutrients and Proximate Composition of Peanut (Arachis Hypogaea)
Peanuts (Arachis hypogaea), which is also referred to as groundnuts in certain places of the world are edible leguminousseeds.IndiaandNigeriaarethesecondandthird principal producer of peanuts respectively in the whole world,withtotalproductioncapacityofapproximately6.857 million metric tons and 3.029 million metric tons respectivelyperyear[1]. Arachis hypogaea (A. hypogaea) is also regarded as pea from the family (fabaceae) of bean/legume.Eventhough A.hypogaea isaleguminouscrop; itiscommonlyconsideredasoilseedsbecauseofitsgreatoil content. A. hypogaea isarichsourceofoil,proteinandfibers [2].Asidetheproductionofoil, A. hypogaea canbeusedfor peanutbuttermanufacturing,productionofconfectioneries androastedpeanuts,manufacturingofSnackproducts,meat productformulationextendersandformakingofsoupsand desserts.Therearesomany A. hypogaea cultivarspresently. Some A. hypogaea varietiesarefavouredoverothersbecause their specific usages due to their differences in flavour, percentageoilcontent,variationintheirsizeandshape,and their ability to resist diseases infection. There are many differentcultivarswhichareusedinterchangeablyhowever, themostpopularcultivarsareSpanish,Runner,Virginiaand Valencia.
Most A. hypogaea soldaredoneintheirshellandaremostly oftheVirginiatypewithsomeValenciasbreedchosendueto theirlargeness insizeandthe eye catchingappearance of their shell. Spanish A. hypogaea are commonly used for productionofcandy,saltednuts,andbutter.SomeRunner varieties are also used to manufacture peanut butter [3]. The consumption of A. hypogaea globally are in various forms,principallyastraditionalcuisine.Theyareutilisedas the comprehensive source of dietary basis for people on tourstovariousareaslikeAntarctica,spaceandtrekking.It hasnotablybeenthesourceofeliminationofmalnutrition amongst the population in many African countries in the recentyears[4].Anti nutrientsaresubstancesfoundinmost foodsubstanceswhicharePoisonoustohumansorinsome wayslimitthenutrientavailabilitytothebody.Plantsevolve thesesubstancestoprotectthemselvesandtopreventthem frombeingeaten.However,ifthedietisnotvaried,someof thesetoxinsbuildupinthebodytoharmfullevels[5].Some vitamins in food may be destroyed by anti nutritional substances. Legume family is one of the most important families in plant kingdom, inwhich it is a cheap protein source for vegetarian diets [6]. The Presence of anti nutritionalfactors, such as flatulence factors, phytic acid and enzyme inhibitor limitthe useof leguminouscrops in food industry. There are diverse anti nutrients domiciled in various fragments of A. hypogaea, such as peanuthull, skin, seed, kernel, root and cotyledons[7]. The presence of lectins in A. hypogaea causes broad interference withabsorption of nutrients across intestinal wall. Lectins also known as hemagglutinin, is a plant agglutinin that exerts specific affinity for certainsugar molecules[8]. Ramakrishnaetal.[6]reported thepresence of trypsin inhibitors inhibiting the activities of protease, such as plasmin, chymotrypsin and trypsin. Pahnwar[9] revealed the presence of phytates, oxalates, tannins, aflatoxin, oligosaccharides and hydrogen cyanide in peanuts and their effects on health. Goitrogens is a naturally occurring compound that is present in groundnut thatsuppresses the function of thyroid gland [8]. It interferes the uptake of iodine, which in turn causes the enlargement of thyroid gland. The phenomenonisknownas“goitre”.Salunkhe[8]alsofound PeanutIingroundnuts. Peanut I is a peanut protein that acts asan allergic factor in inducingpeanut allergy in certain individuals. The other anti nutrients that are present ingroundnut include phenolic compounds, flatus agent, bitter flavour compoundsand phytate. Thisstudy investigates the presence of some anti nutritional factors
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Abstract In this study, the fresh peanuts were dehydratedby microwave hot air drying and conventional hot air oven drying methods. The samples were dried at three different temperatures: 50, 60, and 70oC, with and without the application of pretreatment by soaking in water and in brine. The effect of the pretreatment and drying processes were tested on some of the anti nutrients (oxalate and tannin), and proximate composition of the peanuts. The average value for oxalate and tannin were 24.58% and 5.27% respectively for the raw samples. Pretreatment and microwave drying was proven to have the highest effect on the anti nutrients by reducing the oxalate from 24.58% to 2.08% when pretreated in brine and dried at 70oC; and the tannin was also reduced from 5.27% to 3.33% when water soaked and microwave dried at 70oC. This shows that pretreatment by soaking in brine or water reduced the anti nutritional factor of peanut which in turn influenced the proximate compositions of the peanuts.
1,2Department of Agricultural and Food Engineering, Faculty of Engineering, University of Uyo, Uyo, Akwa Ibom State, Nigeria ***
1. INTRODUCTION
PermanganateTitration
2.2 Pretreatments
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2.3 Processing Techniques
The effects of pretreatment and processing techniques on the anti nutrients are presented in tables 1 and 2. The averagevalueforoxalatewas24.58%atroomtemperature (RT)(seetable1).Theresultsobtainedfromthisresearch showedasignificanteffectofthepretreatmentsontheanti nutrients. Soaking in water and in brine as pretreatment measures have reduced the percentage of oxalate from 24.58% to 4.83% when soaked with water and to 3.99% whensoakedwithbrine(seetable1),soakingisadomestic treatment that is often used by people to prepare complimentaryfoodsathome.PreviousstudiesbyMubarak [12] and Vijayakumari et al. [13] had shown that soaking pretreatmentandsignificantlyreducedphytate,trypsininhibitoractivity(TIA),tannincontents.Table2,alsoshowedtheeffectsofandprocessingtechniquesontheantinutrient
3. RESULTS AND DISCUSSIONS
likeoxalatesandtanninsin A. hypogaea andevaluatesthe effectsofprocessingtechniquesonthem.
Seedsofunshelledpeanutsweresoakedindistilledwater for1,2,and3hoursatapeanut:waterratioof1:10(w/v). Aftersoaking,thewaterwasdrainedoffandtheseedswere dried in the hot air oven. Also, raw seeds of unshelled peanutswerebrinesoakedfor1,2,and3hoursatpeanut: water ratio of 1:10 (w/v). After soaking, the water was drainedoffandtheseedsweredriedinahotairoven.500gof the pre soaked sample was separately subjected to the followingprocessingtechniques;microwavedryingandoven drying.
2.4 Anti nutrients Determination (a) Determination of Tannin
2.6 Statistical Analysis
2.5 Proximate analysis
Alltheexperimentsweremadeintriplicateandtheresults were expressed as mean ±SD (standard deviation). The differentbetweenmeansweredeterminedusingANOVAand Turkey’sHSDadhoctestinSPSS20.0
PreparationoftheStandardSolutionofIndigoCarmine Standard solution of Indigo carmine was prepared as follows:6gIndigocarmineisdissolvedin500mlofdistilled deionizedwater(dd)byheating,aftercooling50mlof95 97%isadded,thesolutionisdilutedto1Landthenfiltered. The blank tests by titration of a mixture of 25ml indigo carminesolutionand750mlddH2Oarecarriedout.
(b) Oven Roasting Seedswereoven roastedfor6minusingadomesticsize hotairoven.Afterthetreatment,theseedsweredriedand then,grindedwiththemotarandpestleintogranules,putin cruciblesandplacedinthedesiccatorsforfurtheranalysis.
Quantitative estimation of tannin was performed by titratingtheextractwithstandardpotassiumpermanganate solution following the method of AOAC [10] Briefly 5 ml aliquot of the extract was mixed with 12.5 ml of indigo carminesolutionand375mlofdistilledwater.Thismixture was titratedagainstKMnO4solution(“Y” mL).As titration preceded the blue colour of the indigo carmine passes throughmanyshadestoafinalyellowwithafaintpinktintat therim.Itwastakenastheend point.Theconcentrationof tanninwasestimatedusingthefollowingrelationship: 1mlofstandardKMnO4solution=0.595mlof0.1NOxalic acid1mlof0.1NOxalicacid=0.0042goftannin
The proximate compositions of the cocoyam sample, namely, moisture, ash crude lipid, protein content, crude fibre, and carbohydrate were determined according to the recommendedmethodsoftheAOAC[10].
2.1 Collection and Preparation of samples
(b) Oxalate Content Determination
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(a) Microwave Roasting Seedsweremicrowave roastedfor6minusingadomestic sizeMoulinexmicrowave(Geli1380,type665;Geligroup, Zhuhai City, China). After the treatment, the seeds were driedinahotairovenandthen,grindedwiththemotarand pestle into granules, put in crucibles and placed in the dessicatorsforfurtheranalysis.
2. MATERIALS AND METHODS
Shandongpeanuts whichare characterized by plump grain size, large size, with excellent taste and high nutritionsamplewascollectedfromalocalvendorinUyo, Akwa Ibom State. The sample was soaked, dried and subjectedtothetriplicatetreatment.
Oxalate content was determined by AOAC (2012) [11] method.Briefly,1gofthesamplewasweighedinto100mL conical flask. Then, 75 mL of 3mol/L were added and the solutionwascarefullystirredintermittentlywithamagnetic stirrerforabout1handthenfilteredusingWhatmanNo.1 filterpaper.Thesamplefiltrate(extract,25mL)wascollected andtitratedagainsthot(80 90°C)0.1N solutiontothepoint whenafaintpinkcolourappearedthatpersistedforatleast 30s. The concentration of oxalate in each sample was obtainedfromthecalculation: 1mL0.1permanganate=0.006303goxalate
Raw(R)
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TemperatureDrying(
Brine
Valueswithdifferentletterswithinthesamerowandcolumnshowsignificantdifferences(P<0.05). There was no significant effect of heat on tannin content whendriedat50and60oC,but,reducedto3.33%whenthe temperaturewasraisedto70oC,indicatingthatincreasein heat could cause a decrease in the anti nutrient when samplesareovendried.Whensampleswerewatersoaked and oven dried, the tannin content showed no significant effect;theaveragevalueofthetannincontentwaswithinthe rangeoftherawsample(Table2)duringovendrying.Even atbrinesoakingandovendriedat70degreesCelsius,there arenosignificantdifferenceswiththerawcontentoftannin and brine soaked and dried samples as presented in the Table2. There was no significant differences between the raw (untreated) sample and the microwave dried content of tanninevenasthedryingtemperaturesincreasedfromroom temperature to 70oC. Similarly, there was no observable significantdifferencesbetweentheraw(untreated)sample and the oven dried content of tannin at increasing drying temperatures, except at 70oC, where the tannin level significantlyreducedto3.42±0.29%(seetable2).Pretreated microwavedandovendriedsamplesshowednosignificant effectontanninaspresentedinthetable2,exceptforbrine soaked(BS)and microwaveddriedat70oC(3.50±1.09%). The least value of tannin for pretreated and dried sample was obtained at 70oC as 3.33% when water soaked and microwaveddriedat70oC.
Table 2: EffectsofovendryingandmicrowavedryingofPeanutinreducingTannin TemperatureDrying( 0C) Raw(R) Water(WS)Soaking Brine(BS)Soaking MD OD MD OD MD OD Room temp. ( RT) 527±139�� 527±139�� 392±024�� 392±014�� 375±043���� 375±043�� 50 441±038�� 508±038�� 375±025�� 541±029�� 425±043���� 466±014���� 60 417±101�� 506±038�� 342±080�� 491±014���� 383±038���� 458±014���� 70 375±025�� 342±029�� 333±014�� 450±075���� 350±109�� 441±014���� Valueswithdifferentletterswithinthesamerowandcolumnshowsignificantdifferences(P<0.05).
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tannin.Theaveragevaluefortanninwas5.27%atRT(see table2).Therewassignificanteffectofthepretreatmenton theanti nutrient.Tanninwasreducedfrom5.27%to3.92% during water soaking and to 3.75% during brine soaking. Therewerenosignificantdifferencesbetweenwatersoaking andbrinesoaking(seetable2). The oxalate content was also seen to significantly reduce whensampledryingtemperatureswasincreasedfromthe temperaturesof50to70oC,revealingtheeffectsofovenheat ontheanti nutrient.Whenthesamplewaswatersoakedand subjectedtothesameoventemperaturesof50to70oC,the oxalate content reduced to a minimal level of 2.10% at 70oCelsius.However,brinesoakedandovendriedvaluesof oxalatecontentshowedsignificanteffectcomparedwiththe rawsampleasthevaluereducedto2.73%.
The microwave drying showed a significant effect on the oxalate content of peanut, the oxalate content decreased withincreaseintemperaturetoaminimallevelof5.46%at 70oC.Pretreatedandmicrowaveddriedsamplesshoweda significanteffectontheoxalatecontentaspresentedinthe table1,exceptforbrinesoakedandmicrowaveddriedat50 and60oC.Theleastvalueofoxalatecontentforpretreated andmicrowavedriedsamplewasobtainedas2.08%at70oC.
Table 1: EffectsofovendryingandmicrowavedryingofPeanutinReducingOxalate 0C) Water(WS)Soaking (BS)Soaking temp. ( RT) 2458±126 2458±126 483±036 483±036�� 399±036�� 399±036�� 50 1051±073�� 735±036�� 189±036���� 399±036�� 399±036�� 273±073���� 60 861±036�� 420±036�� 336±073�� 357±036�� 378±189�� 273±036���� 70 546±036�� 420±036�� 294±036�� 210±073�� 208±093�� 252±063��
MD OD MD OD MD OD Room
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REFERENCES
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[3] Woodroof, “The composition and nutritive value of groundnut kernels” . In The groundnut crop, pp 173 213,1983
[1] USDA,“Nutritionfactsforpeanuts,alltypes,raw,USDA Nutrient Data” Conde Nast, USDA National Nutrient Database, version SR 21. 2014, Retrieved January 15, 2015.
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[2] Suchoszek Lukaniuk et al., “Health Benefit of Peanut (Arachis hypogeal L.) Seeds and Peanut Oil Consumption”. In book: Nut and Seeds in Health and DiseasePrevention,pp.873 880,2011
Effect
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Theresultsobtainedfromthisresearchshowedasignificant effect of the pretreatments on the anti nutritional factors. Soaking in water and in brine as pretreatment measures have reduced the percentage of oxalate from 24.58% to 4.83% when soaked with water and 3.99% when soaked withbrine.Also,theeffectsofpretreatmentandprocessing techniques on the anti nutritional factor tannin showed tanninreductionfrom5.27%to3.92%duringwatersoaking and 3.75% during brine soaking. The oxalate content significantlyreducewhensampledryingtemperatureswas increasedfrom50to70oC,revealingtheeffectsofovenheat ontheanti nutrient.Whenthesamplewaswatersoakedand subjectedtothesameoventemperaturesof50to70oC,the oxalate content reduced to a minimal level of 2.10% at 70oCelsius.Anti nutrientswasalsoseentoaffecttheamount ofnutrientavailableinfoodandhence,influencetheusage of such food raw material. Reducing the anti nutrients helpedtoimproveonthenutritionalcontentofthefood.
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�� 600C 181±002�� 197±003��
Table 2, also shows the effects of pretreatment and processing techniques on the anti nutrient tannin. The average value for tannin is 5.27 ±1.39 %. There were significant effects of pretreatments on the anti nutrient tannin.Tanninwasreducedto3.92±0.24%duringwater soaking and 3.75 ±0.43 % during brine soaking at room temperature.Therearenosignificantdifferencesbetween watersoakingandbrinesoaking. Theeffectofprocessing methodsandtemperatureontheproximateanalysisofoven driedpeanutispresentedinTables3ato3b.Table3ashows the proximate results for moisture contents, ash contents andfatcontentswhiletable3bshowstheproximateresults for fibre contents, protein contents and carbohydrate contents. -3a: of (OvenDrying) TemperaturesontheProximateAnalysisofPeanut 2296±061 192±003 3553±009 3006±033 3591±049 2218±007 1419±031 1893±068 C 261±003 195±004 179±002 3163±154 3056±025 3508±008 982±176 1139±030 2252±020 Valueswithdifferentletterswithinthesamecolumnshowsignificantdifferences(P<0.05). The average moisture content of raw peanut was 4.07%; water soaking and brine soaking influenced the moisture contentto5.24%and3.55%respectively.Theash,fat,fibre, protein and carbohydrate content of raw peanut were obtained as 2.61%, 48.45%, 2.71%, 36.77% and 9.45% respectively.Watersoakingshowedsignificantincreasein the ash content and decrease in the fat, fibre, protein and carbohydrate content. Brine soaking showed significant increaseintheproteincontentandcarbohydratecontentas presentedintables3aand3b. Theleastvaluesforprotein andfatwereobservedas29.90%and46.33%respectively whensampleswerewatersoakedandovendriedat50 Percentage raw Ash and Fat contents 3.13% and 51.76 % respectively were highest when oven dried at 70 . Oven drying had some significant effects on the proximate compositionofpeanut. 4. CONCLUSIONS
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TM MC (% wb) Ash (%) Fat (%) Raw WS OD BS OD Raw WS OD BS OD Raw WS OD BS OD RT 524±012�� 407±006�� 355±015�� 261±005�� 405±005�� 274±004�� 4845±039�� 4701±056�� 3555±049�� 500C 4.37±0.04�� 4.41±0.03�� 3.70±0.01�� 2.72±0.04�� 2.76±0.03�� 2.59±0.02�� 45.09±0.11�� 46.33±0.09�� 35.66±0.15�� 600C 371±001�� 428±004�� 366±006�� 258±003�� 258±002�� 271±002�� 3419±014�� 4692±008���� 3687±018�� 700C 104±004�� 410±006�� 364±002�� 313±008�� 396±004�� 249±002�� 5176±050�� 4804±007�� 3448±020�� Note:TM=Temperature,RT=roomtemp,WS OD=soakedinwaterandovendried,soakedinbrinesolutionandovendried Table 3b: EffectofTreatment(OvenDrying)atVariousTemperaturesontheProximateAnalysisofPeanut TM Fibre (%) Protein (%) Carbohydrate (%) Raw WS OD BS OD Raw WS OD BS OD Raw WS OD BS OD RT 271±037�� 196±004�� 191±002�� 3677±362�� 3391±122�� 3737±025�� 945±316�� 900±071�� 1737±025�� 500C 227±005�� 213±002�� 183±002�� 3169±081�� 2990±059�� 3326±073�� 1387±088�� 1447±062��
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[4] GuimonJ.andGuimon,“HowReady to UseTherapeutic FoodShapesaNew TechnologicalRegimetoTreat ChildMalnutrition” InTechnologyForecastSoc.Change, (7):1319 1327,2012 [5] Norman, N.P., Food Science. CBS Publishers and Distributors,780,1987 [6] Ramakrishna, Rama and Rao, “Antinutritional Factors duringGerminationinIndianBean(DolichoslabalbL.) Seeds” .InWorldJournalofDairyandFoodScience,1(1): 6 11 [7] Lindsey,D.L.,Turner,R.B.,Davis,D.D.,andBishops,R.D., “Isolation and Identification of 5,7dimethoxyisoflavone, An Inhibitor of Aspergilllus flavus from Peanuts” In Mycopathologia. 57, 38 40, 1975 [8] Salunkhe,“OilsandFats,EdibleAnalysis” InNewYork, VanNostrandReinhold.VXII.554p.1992 [9] Panhwar, F., “Anti nutritional factors in oil seeds as aflatoxin in groundnut”, 2005. Retrieved October 18, 2010,fromwww.ChemLin.com. [10] AOAC(AssociationofOfficialAnalyticalChemists) Official methods of analysis, association of analytical chemists.15thEdition,WashingtonD.C.USA,141 144, [11]2005AOAC (Association of Official and Analytical Chemists). Official Methods of Analysis. 19th Edition, Association of Official and Analytical Chemists, WashingtonD.C.876p,2012. [12] Mubarak, A.E., “Nutritional composition and antinutritionalfactorsofmungbeanseeds(Phaseolus aureus) as affected by some home traditional processes”.InFoodChemistry,89:489 495,2005 [13] Vijayakumari, K., Pugalenthi, M., and Vadivel, V., “Effectofsoakingandhydrothermalprocessingmethods on the levels of antinutrients and in vitro protein digestibility of Bauhinia purpurea L. seeds”. In Food Chemistry,103:968 975,2007