chemical composition and protein quality mucuna pruriens

8/12/2019 Chemical Composition and Protein Quality Mucuna Pruriens

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Chemical Composition and Protein Quality of the Little-KnownLegume, Velvet Bean (M u c u n a p r u r i en s (L.) DC.)

Pe r u m a l Sid d h u r a ju , K a r u p p a n a n V ija y a k u m a r i , a n d K a r n a m J a n a r d h a n a n *

B iochemis t ry L a b ora t ory, Dep a rt ment of B ot a ny, B ha ra t hia r U nivers it y,Coimbat ore 641 046, Tam il Na du, I ndia

The chemical composit ion an d nutri t ional chara cterist ics of seeds of M u cu n a p r u r i en s wereinvest iga ted. The ma tu re seeds cont a ined 314.4 g/kg crud e protein , 51.6 g/kg cru de fiber, 67.3 g/kgcrude fat , 41.1 g/kg ash, and 525.6 g/kg carbohydra tes. P ota ssium, phosphorus, a nd calciumregister ed higher concentra tions compa red wit h th e most commonly consumed pulses. The globulinsa nd a lbumins t ogether constit uted the m a jor st orage proteins (22.7 g/100 g of seed flour). Theessentia l am ino acids profile of tota l seed proteins compared fa vora bly wit h th e FAO/WHO referen cepat tern except for deficiency of sulfo a mino acids. When compar ed with g lobulins, albumins a ppea redto be a r ich source of valine a nd tr yptophan . However, cystine, methionine, a nd leucine were deficientin both the protein fractions. B oth oleic an d l inoleic acids consti tuted t he predominant fat ty acids(65. 5%) a l o n g w i t h a s u bs t a n t i a l q u a n t i t y of p a l m it i c a ci d (20. 16%). D ry h e a t i n g a s w e l l a saut oclaving significan tly reduced t he a ntinutri t ional fa ctors. Pr otein effeciency ra t io, true proteindigestibi li ty, biological value, net protein uti l izat ion, a nd uti l izable protein were significan tlyi m prov ed b y a u t ocl a v i n g a s com p a re d w i t h dry h e a t i n g . H o w e ve r, t h e v a l u es of t ru e p rot e indigestibi l i ty and net protein uti l izat ion of dry-heated samples were significantly higher than the

raw samples.

Keywords: M u cu n a p r u r i en s; ch emi ca l comp o si t i on ; a m i n o a ci d s; fa tty a ci d s; a n tr i n u tr i t i o n a l factors; h eat tr eatm ents; bi ological evalu ati on

INTRODUCTION

The ma tur e seeds, seeds from unr ipe pods, and seedsfrom young pods of M u cu n a p r u r i en s(L.) DC. a re soakedand boiled/roasted an d eaten as such (or) mixed withs a l t b y t h e N ort h e a s t I n di a n t r i b a l s ect s K h a s i , Na g a ,K u k i, J a i n t i a , C h a k m a , a n d M i zo (Arora , 1981) a n dother poor vi l lagers. The tribals G ar os of Meghalayaar e consuming the seeds for increasing potency, and t hehairs of the seed coat are used as vermifuge (Vasudevaand Shanpru, 1981).

However, the a cceptability a nd ut ilization of legumesa s food ha s been limited due to the presence of relat ivelyhigh concentrat ions of certain antinutri t ional factorssuch as lectins, protease inhibitors, R-amy lase inhibitor,allergens, polyphenols, a nd phytic a cid (Liener, 1994).To overcome the aforesaid adverse factors, the variousprocessing methods must be considered. A perusal ofthe l i terat ure reveals t ha t only l imited informa tion onchemical composition of the above sa id legume is a vail-able (Prakash and Misra, 1987; Laurena et al . , 1991;Mar y J osephine and J ana rdha na n, 1992; Vijaya kuma riet a l . , 1995). However, no at tempts seem to ha ve been

made to decipher the fatty acid profiles of the lipids, tos t u dy t h e e ff ect s of v a ri ou s p roce s si n g m e t h ods t oremove the ant inutrients, a nd to evalua te the biologicalvalue of seed proteins of this little-known legume.

MATERIALS AND METHODS

Samples. About 5 kg of ma ture a nd dry seeds of M u cu n a p r u r i e n s (L.) DC. were collected from five plants grown in thesame ecosystem of the deciduous forests of Yercaud Hills,S al e m Di st r i ct , Tam i l Na d u, I nd i a . Fur t he r m or e , t he se e dsaft er collection w ere dried in the open sunlight for 2 da ys. Thedried seeds were cleaned thoroughly, and a ny foreign ma tter,broken seeds, and imma ture seeds were removed. The seedsw e r e st or ed i n a plast i c c ont a i ner at r oom t e m pe r at ur e (25 C ).

Proximate Composition. Seed moisture wa s determinedby following t he method of Rajara m a nd J ana rdha na n (1990).The seeds were powdered separately in a Willey Mill to 60mesh size. The fine seed powder so obta ined wa s stored inscrew-cap bottles at room temperature and used for furtheran alysis. Nitrogen content w as determined according to theKjeldahl method (Humphries, 1956), and the percentage ofcr ud e pr ot ei n w a s c al cul at e d usi ng t he fac t or 6 .2 5. Thecontents of crude l ipid, crude fiber, and ash were determined

in accordan ce wit h th e sta nda rd meth ods of the AOAC (1970).Ca rbohydrates w as obta ined by difference. The energy valueof the seeds was estimated (in kJ ) by multiplying the percent-ag e of c r ud e pr ot e i n, c r ud e fat , and c ar b ohy d r at e s b y t hefactors 16.7, 37.7, a nd 16.7, respectively.

Fiber Analysis. The method of Goering and Van Soest(1970) wa s used to determine neutra l detergent fiber (NDF)as w ell a s acid detergent fiber (ADF). Insoluble hemicellulosewas calculated as the loss in the weight of ADF residue aftertreat ment with sulfuric acid. The loss in weight of the aboveresidue upon ashing w as used to calculate t he l ignin content.

Analysisof Mineral Elements. Determination of Ca, Mg,Fe, Cu, Zn, and Mn was carried out by using a Perkin Elmerat omic absorption spectrophotometer (Model 5000, P erkinElmer), w hile a flame photometer (Elico, India) wa s used forthe determina tion of potassium and sodium. Ph osphorus wascolorimetrically analyzed (APHA, 1980) at 630 nm using aspectrophotometer (Model Spectronic 20D, Milton R oy).

Lipid Extraction. S eed flour (2 g)w a s extracted overnightb y shaki ng w i t h 3 0 m L of a m e t hanol-ethyl ether mixture(1+1) at room temperatur e (25 C). The mixture wa s centri-fuged at 10000g for 30 min at room tempera tur e (25 C). Thee xt r a c t ion w a s r ep ea t e d t w i ce i n t h e s a m e m a n n e r. Th eextracted flour was air-dried and used for the extraction oftotal proteins and protein fractionations.

Extraction and Estimation of Total Seed Proteins andSeed Protein Fractionation. The tota l (true) proteins wereextracted by the method of Rajaram an d J ana rdha na n (1990).The extracted proteins were precipitated by adding cold TCAto a fina l concentra tion of 20%. The precipitat e wa s separa tedby centrifugation at 20000g for 30 min at 4 C and estimated

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by the meth od of Lowry et a l. (1951). The rema ining proteinwas lyophilized.

Albumins and Globulins.After lipid extraction from theseed flour residue, the albumin and globulin fractions of seedproteins were extra cted and separ at ed according to the methodof Murray (1979).

Prolamins. The se e d f l our r e sid ue a f t e r a l bum i n a ndglobulin extra ction w as extracted with 30 mL of 80%etha nolovernight a t 25 C. The suspension wa s centr ifuged at 20000gfor 30 min, a nd the supernata nt containing prolamins wa s a ir-dried and dissolved in 0.1 N NaOH.

Glutelins. The seed flour residue a fter prolamin extr action

wa s extracted with 30 mL of 0.04 M NaOH overnight at 25 Cand centrifuged at 20000g for 30 min at room temperature.

Protein Content. All four protein fractions (albumins,globulins, prolamins, and glutelins) so obtained were precipi-ta ted a nd w ash ed with cold 10%TCA. The precipita tes wereseparated by centrifugation at 20000g f or 1 h a t 4 C a n dr e di ssol ved i n 0 . 1 M Na O H , a nd t he pr ot e in c ont e nt w a sdetermined according t o the method of Lowry et a l. (1951) withl ipid -e xt r ac t e d b ovi ne se rum a l bum i n as t he st a nd ar d . Aportion of precipitated protein was centrifuged and freeze-driedprior to amino acid analysis.

Amino Acid Analysis. K now n am ount s of pr ec ipit at e dt ot a l s ee d p r ot e in s a n d p r ot e in f r a ct i on s (a l b um in s a n dglobulins) were a cid hy drolyzed with 6 N HC l for 24 h at 110C in sealed ampules under vacuum. The amino acid analysiswa s performed using an aut omated precolumn derivatiza tion

w i t h O-phthaldialdehyde (OPA) using reverse-phase HPLC(Model 23250). The cystine content of protein sam ples wa sobtained separately by the method of Liddle and Saville (1959).For t he d e t er m i nat i on of t r y pt ophan c ont e nt of pr ot ei ns,aliquots containing known amounts of proteins were dispersedinto glass a mpules together with 0.75 mL of 5 M NaOH. Theampules were flame sealed and incubat ed at 110 C for 18 h.The t r y pt ophan c ont e nt s of t he al kal i ne hy d r oly sat e s w e r ed e t er m i ned c ol or i m et r i cal l y b y t he m e t hod of S pi es andC ham b e r s (19 49 ). The c ont e nt s of d i f fer e nt am i no ac i dsr e cove r ed w e r e pr ese nt ed as g /1 00 g of pr ot ei ns and ar ecompa red w ith th e FAO/WHO (1990) reference pat tern. Theessentia l a mino acid (EAA) score wa s ca lculated as follows:

Fatty Acid Composition. The total lipids were extractedfrom the seeds according to the method of Folch et al. (1957)using a chloroform and methanol mixture in the ratio of 2:1(v/v). Methyl esters w ere prepared from the total l ipids bythe method of Metcalfe et a l . (1966). The fat ty acid methylesters were analyzed by gas chromatography (Shimadzu GC-R 1A, J apan) usi ng a n i nst r um ent e q uippe d w i t h a f l am eionization detector (FID) and a glass column (2 m 3 m m )packed with 1%diethylene glycol succinate on chromosorb W(silanized 80/100 mesh). The carrier gas wa s n itrogen at aflow ra te of 32 mL/min. The column tempera tur e grad ient of4 C /m i n r ang e d fr om 1 90 t o 2 40 C . A st and ar d fat t y ac i dm e t hy l e st er m i xt ur e (S ig m a C he m ic al C o. ) w a s r un t o use

retention times in identifying sample peaks. Fa tty acid levelswere estimated on the basis of peak areas of known concentra-t i ons of t he st a nd ar d s.

Heat Treatments. About 1.5 kg of seeds was roasted at120 C for 30 min, a l lowed t o cool, a nd t hen powdered to 60mesh size. A sample of 1.5 kg of seeds wa s a utoclaved a t 15l b pr essur e for 3 0 m in i n w at e r using a 1 0: 1 w at e r t o se edr at i o. The aut ocl avi ng li q uid w a s se par a t e d , and t he a ut o-claved seeds were dehydrated with a hot air oven at 50 C toa constant weight an d powdered for a nalysis of antinutri t ionalcomponents an d feeding tests.

Determination of Total Free Phenolics, Tannins, Hy-drogen Cyanide, and P hytic Acid. The antinutri t ionalcomponents, t otal free phenolics (Sada sivam a nd Ma nickam,1992), tannins (Burns, 1971), and hydrogen cyanide (HCN)(J ackson, 1967) were qua ntified in ra w a s well as in moist a nd

dry hea t-trea ted seeds. The colorimetric procedure of Wheeleran d F errel (1971) wa s followed t o estimat e phytic a cid.

Determination of L-DOPA. L-DOP A [3-(3,4-dihy droxy -phenyl)-L-ala nine] content wa s determined by extracting w ith0.1 N H Cl a nd etha nol (Br ain, 1976).

Trypsin I nhibitor Analysis. Trypsin inhibitor activitywa s determined by the enzymic assa y of Ka kade et a l . (1974).One trypsin un it is expressed a s a n increase of 0.01 absorban ceunit per 10 mL of reaction mixture at 410 nm. Trypsin in-hibitor activity is defined in terms of trypsin units inhibitedper milligram of protein.r-Amylase Assay. R-Am y l ase ac t i vit y w a s d e t er m i ned

a ccording to th e procedure outlined by Moneam (1990). Oneunit of enzyme activity was defined as that which l iberates 1mol of reducing gr oups (calculat ed a s ma ltose)/min a t 27 Can d pH 7.0 under t he specified conditions (Deshpande et a l . ,1982) from s oluble sta rch.r-Amylase Inhibitor Analysis. R-Amylase inhibitor ac-

tivity wa s evaluat ed according to the method of Deshpande eta l. (1982). A 1-g sa mple wa s extra cted with 10 mL of distilledw a t e r for 1 2 h at 4 C and c ent r i fuge d at 5 000g for 20 min,and t he supe r nat ant s w e r e t e st e d for R-am ylase inhibitoryactivity. Extr act-conta ining inhibitor (0.25 mL) wa s incubatedwit h 0.25 mL of enzyme solution for 15 min a t 37 C. To thismixture after preincubation was added 0.5 mL of 1%starchsolution. At t he end of 30 min, the reaction wa s stopped bythe a ddition of 2 mL of dinitrosalicylic acid reagent a nd hea tedin a boiling wa ter bat h for 10 min. The test tubes were then

cool ed u n d er r u n n in g c ol d t a p w a t e r a n d m a d e t o a f in a lvol um e of 1 3 m L w i t h d i st i ll ed w at e r . The a b sor b anc e w asrecorded at 540 nm in a Spectronic 20 D spectrophotometer.The libera ted reducing suga rs w ere expressed as m a ltose. Oneu n it of R-a m y l a s e a c t iv it y i n hi bi t ed w a s d ef in ed a s on eR-amy lase inhibitory unit .

Phytohemagglutinating Activity.The tota l crude lectinswere extra cted by t he method of Almeida et a l . (1991). Theprotein content of the extra ct wa s estimat ed by the method ofLowry et a l . (1951). The phytohemagglutinat ing activity ofraw and treated seed samples was determined by the methodof Tan et al . (1983) and expressed as hemagglutinating unit(HU) per milligram of protein.

Rat Bioassay. The diet consisted of test material contrib-uting 10%protein in t he diet, 4%mineral mixtur e, 1%vita minmixture, 10% oil , 5% cellulose, an d corn sta rch to make up

t he r e m ai ning d i et . A c ont r ol d i e t c ont a i ning 1 0% c asei nprotein wa s also prepared. For the determination of proteinefficiency ra tio, groups of five Wista r stra in male ra ts (Pa steurResearch Inst itute, Coonnoor, The Nilgiris district, India ) aged21-23 days, ea ch weighing about 40 g, were used. Wat er andfood w e r e g i ven ad l ib i t um . We ig he d d i et w a s g i ve n, andunconsum e d d i e t w a s c ol le ct e d , d r i e d, and w e i ghe d . Theexperiment was conducted for 28 days (Pellett and Young,1980). The rat s were weighed twice a week. Food and proteini nt ake s d ur i ng t he pe r i od of s t ud y w e r e c al c ul at e d on d r yma tt er basis. P rotein efficiency ra tio (P ER) and food efficiencyrat io (FER) w ere determined a s follows:

B i ol og i c al e val uat i on of pr ot e i n q ual i t y of r aw and he at -treat ed seed sa mples w as conducted according to th e methodof Eggum (1973). G roups of five Wista r stra in male ra ts, eachweighing about 60 g, were used. Ea ch rat w as da ily fed a 10-gdiet (dry w eight basis) conta ining 150 mg of nitrogen. Theexperiments consisted of a 4-day preliminary period a nd a5-day bala nce period. During t he bala nce period, urine andfeces were separately collected each day from each rat andpooled separa tely for 5 days . At t he end of 5 day s, unconsumedd ie t w e ig h t w a s r eco rd ed , a n d t o t a l n i t r og en i n t a k e w a scalculated. Another group of rats of the same weight and a gewere fed a nitrogen-free diet to calculat e the endogenous and

EAA score )

g of EAA in 100 g of test protein

g of E AA in 100 g of FAO/WHO ref pa tt ern 100

P E R )gain in body weight (g)

proein int ake (g)

F E R )gain in body weight

food in ta ke (g)

Velvet Bean Protein Composition and Quality J. Agric. Food Chem.,Vol. 44, No. 9, 1996 2637


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metabolic nitrogen losses. The concentra tion of nitrogen inurine and feces was estima ted by the Kjeldhal method. Trueprotein digestibility (TD), biological value (BV), net proteinutilization (NP U), and ut ilizable protein (UP ) were determinedfor al l sa mples.

Statistical Analysis. The dat a w ere sta tistically ana lyzedusing D uncans Multiple Range Test (DMRT) by t he meth odof Alder and Roessler (1977), and the significant differencesobtained are discussed in the text.

R E S UL T S AND DI S C US S I O N

The mean value of the proximate and fiber composi-tion for M u c u n a p r u r i e n s seeds a re shown in Table 1.

The seeds of M . p r u r i en s contain an average of 314.4 gcrude protein kg-1 D M , w h i ch s ee ms t o b e h i g h ercompared to an earl ier report (Laurena et al . , 1991),suggesting tha t i t is a better source of protein. Due tothe presence of relat ively high levels of crude fat andprotein, the seeds a ppear t o be a rich source of energy.Fiber helps to maintain the heal th of the gastrointes-

t i n a l t ra ct . N eu t ra l de t erg en t f ib er ( ND F ) a n d a ci ddetergent fiber (ADF ) values a re found t o be 213.0 and96.0 g kg-1 DM, respectively. Hemicellulose content ,ob t a i n ed a s t h e di f f ere n ce b e t w e en N D F a n d AD F ,registers a value of 117.0 g kg-1 DM. The presence ofa n a de q u a t e l e v e l o f de t e rg e n t f i b e r i n M . p r u r i en s reveals that the seeds can be utilized as a better sourceof fiber a mong the tribal people. The dat a on minera lcomposit ion (Table 1) indicat e tha t the seeds of th isl i t t le-known legume a re found to be a rich source ofpotassium, calcium, and phosphorus.

As in other pulses, the seeds of M . p r u r i en s exhibitglobulins (16.7 g/100 g ) a nd a lbumin s (6.0 g/100 g) a sthe ma jor seed protein fractions. The dat a on a minoa cid composition an d essentia l am ino acid score of totalseed proteins, a lbumins, a nd globulins of M . p r u r i en s a re given in Ta ble 2. The consumption of this legumecan fulfill the essential amino acid requirement pattern(FAO/WHO 1990) among the people except for S-conta ining amino a cids. Furth ermore, the lysine con-t e n t o f t h e t o t a l p ro t e i n s o f t h i s s a m p l e s e e m s t o b ehigher when compared with an earl ier report from ourlaboratory (Mary J osephine a nd J an ar dhan an , 1992).The amino acid profiles of protein fractions, albumins,and globulins of M . p r u r i en s reveal that cyst ine, me-

thionine, and leucine, a lone in a lbumins an d beside thea foresa id am ino acid tryptophan (a lso in globulins), ar efound t o be the l imiting a mino acids.

The fatty acid composition of the total seed lipids isgiven in Ta ble 3. It revea ls tha t th e seed lipids are richin unsa tur a ted fa tt y a cids such as oleic acid (37.14%)a nd lin oleic a cid (28.71%). The mono- a nd polyun sa tu -ra ted fat t y acids together account for 70.85%, whichseems to be a significa nt find ing. The presence of highlevels of the unsa tura ted fat ty a cids is desirable for th econsuming tribals because i t is a significan t feat ure inhuma n food. Although, the legume seeds conta in highlevels of protein, their digestibi l i ty and uti l izat ion isp oor du e t o t h e p res en ce of ce rt a i n a n t i n u t r i t i on a l

compounds (Liener, 1994).The high content of total free phenolics (Table 4) is

undesirable for human consumption because they in-terfere with the digestion and absorption of protein.However, a significant reduction in the content of totalfree phenolics has been observed under both a utoclaving(61%) and dry hea t t rea tm ent (48%) condit ions only in

Table 1. Chemical, Fiber, and Mineral Composition ofM u c u n a p r u r i en s Seedsa

com pon en t g kg-1 D M

chemical compositionmoisture (g kg-1 F W) 71.0crude protein (N 6.25) 314.4cr ude fiber 51.6cr ude fa t 67.3a sh 41.1ca rboh ydr at es (by differ en ce) 525.6energy content (kJ kg-1 D M) 16565.2

fiberAD F 96.0ND F 213.0h em icellulose 117.0cellulose 82.0lign in 11.2

mineral compositionsodium 174.2pot a ssium 13304.3ca lcium 2857.1m a gnesium 851.2ph osph or us 4065.2m a n ga n ese 5.6ir on 65.4copper 23.0zin c 20.4

a Avera ge values of three determina tions ( standard error. DM,

d r y m a t t e r b a s i s .

Table 2. Amino Acid Composition, Essential Amino Acid Score, and Limiting Amino Acids of Total Seed Protein andProtein Fractions (Albumins and Globulins) of M u c u n a p r u r i e n s (g/100 g of Protein)

amino acidtotal (true)

seed proteinessential amino

a cid scor e a lbu min sessential amino

a ci d s cor e g lob ul in sessential amino

acid scoreF AO/WHO

(1990) valu es

a spa r t ic a cid 8.16 10.41 14.18glut a m ic a cid 17.23 12.20 20.35a la n in e 2.81 3.61 4.05

va lin e 5.57 159.1 5.80 165.7 5.12 146.3 3.50gly cin e 5.12 5.75 4.83a r gin in e 7.16 6.87 5.71ser in e 4.10 4.91 6.05cyst ine

} 0.84

84.8 1.47

58.8 0.71

62.8 2.50m et h ion in e 1.28 t r a ce 0.86t h r eon ine 3.64 107.1 3.85 113.2 4.01 117.9 3.40phenylalanine

} 3.85

136.7 4.20

123.5 5.11

142.9 6.30t y r osin e 4.76 3.58 3.89isoleucin e 4.12 147.1 5.16 184.3 5.57 198.9 2.80leucin e 7.85 118.9 5.08 77.0 4.80 72.7 6.60h ist idin e 3.14 2.76 3.80lysin e 6.60 113.8 5.72 98.6 6.03 104.0 5.80t r y pt oph a n 1.35 122.7 1.25 113.6 0.81 73.6 1.10pr olin e ND a ND ND

a ND, not determined.

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the present st udy. When the seeds of M . p r u r i e n s a reproperly cooked/roa st ed before consu mption, t ota l freephenolics get reduced ma rkedly. This ena bles improve-m e n t i n p ro t e i n di g e s t i o n a n d u t i l i z a t i o n a m o n g t h etribals.

Hydrogen cyanide (HCN) is known to cause a cute orchronic cyanide t oxicity. Although th e level of HCN ishigher in raw seeds, i t is significantly reduced duringdry h eat tr eat ment (67%) a nd a utoclavin g (68%). Hence,HCN-related ill effects can be nullified during consump-

tion of cooked seeds.Phytic acid has the antinutri t ional properties due toi ts abi l i ty to lower the bioavai labi l i ty of minerals andform a complex with proteins and inhibits the enzymaticdigestion of ingested protein (Nolan an d Duffin, 1987).Significant reduction in t he content of phytic acid hasbeen noticed in M . p r u r i e n s subjected to both dry heattr ea tm ent (36%) an d a ut ocla ving (47%) in th e presentstudy.

Consumption of improperly boiled seeds by th e triba lsect Ka nikkars in Kerala Sta te, India, is known to ca useill effects like and increase in body temperature and skineruptions. Sha nkara nar aya n (1978) has a t tributed theaforesa id ill effects to th e presence of L-DOPA, which isp h a rm a c o l o g i c a l l y a c t i v e , a n d i s a l s o k n o w n t o c u re

P ar kinsons disea se. Subsequently, by repeated boilingand decan ting of the seeds for seven t imes with wa ter,a substantial reduction in the quanti ty of L-DOP A hasb ee n s h o w n . C on s u m pt i on of s u ch s ee ds h a s b ee nshown to be safe to the consuming tribals (J ana rdha nan ,1982). In t he present study, L-DOP A content (7.7 gkg-1) seems to be higher a s compar ed to ear lier report s(Daxenbichler, 1972; Mary J osephine and J anardhanan,1992; Vijay akuma ri , 1994). Dry heat treat ment ha s

been shown t o be more effective in reducing th eL -DOPAcontent in th e present report. The possible reductionof L -DOP A content ma y be a ttr ibuted to its ra cemizationunder roasting. Studies of Haya se et al . (1975) havere v e a l e d t h a t a m i n o a c i d re s i du e s i n p ro t e i n s a n d i nsynthetic peptides can ra cemize under r oasting condi-tions.

The an tinutri t ional properties of var ious proteaseinhibitors, R-amylase inhibitors, and lectins have beenwell documented (Liener, 1994). In t he present stud y,

a significant reduction of TI a ctivity ha s been achievedby dry hea t trea tment (93%) an d a utoclaving (96%).S i n ce t ry p s in i n h ib it o rs a re k n o w n t o b e h e a t l a b i le ,t h e i r s t ru c t u ra l di s i n t e g ra t i o n u n de r h e a t t re a t m e n tmay explain the destructive effect on diminished trypsininhibitor act ivi ty.

The seeds of M . p r u r i en s a r e k n ow n t o con t a i nrelat ively high levels of R-amyla se inhibi tor act ivi ty(Table 4) as compared to different varieties of chickpea(Muliman i et a l., 1994). Complete eliminat ion ofR-amy-lase inhibi tor act ivi ty has been observed under auto-claving (Table 4). In genera l, a significant reduction ofh e ma g g l u t i n a t i n g a c t i vi t y (l ect i n ) h a s b ee n n ot i ce da mong a ll the blood groups (A, B , an d O) when th e seedsw e re s u b j e c t e d t o b o t h dry h e a t t re a t m e n t a n d a u t o -

claving (Table 4). The presence of similar residualactivi ty has a lso been reported aft er heat t reatment inPhaseolus vulgaris (Almeida et al., 1991).

In a ddit ion to chemical a nalysis, ra t feeding tr ials ofprotein provide useful information with regard to i tsoveral l qual i ty. The PER a nd FER of ra w, dry-heated,and autoclaved seed samples of M . p r u r i en s along withcasein (control) a re given in Table 5. The food a s w ellas protein inta ke of ra ts fed heat -treat ed seed diets a refound to be higher as compared to raw seed diet , andt h u s t h e ra t s re g i s t e r a s u b s t a n t i a l i n c re a s e i n b o dyweight . However, autoclaved seed sa mples exhibi t arelat ively high level of P ER over ra w seeds.

The biological eva luat ion of raw a nd processed seeds

of M . p r u r i en s along wit h casein a re presented in Ta ble6. The raw seeds of M . p r u r i en s exhibit low levels ofBU , TD, an d NPU . When compar ed with casein, bothdry-heated and autoclaved seeds of M . pr u r i en s exhibitl ow l ev el s of TD a n d N P U . I t m a y b e d ue t o t h epresence of relat ively high levels of polyphenols andfiber since the majority of these compounds are concen-t ra t e d i n t h e s e ed coa t . H o w ev er, a u t ocl a v ed s ee dssignifican tly improve the protein q uality (B V, TD, NP U,

Table 3. Fatty Acid Composition of M u c u n a p r u r i e n s Seed Lipids (%of Total Fatty Acid)

f a t t y a c id

pa lm it ic a cid (C 16:0) 20.16pa lm it oleic a cid (C 16:1) 1.72st ea r ic a cid (C 18:0) 3.84oleic a cid (C 18:1) 28.71lin oleic a cid (C 18:2) 37.14lin olen ic a cid (C 18:3) 3.28a r a ch idic a cid (C 20:0) 1.80beh en ic a cid (C 22:0) 0.73un iden t ified 2.62sa t ur a t ed fa t t y a cids 26.53un sa t ur a t ed fa t t y a cids 70.85essen t ia l fa t t y a cids 40.40

Table 4. Levels of Some Antinutritional F actors Present in R aw and Processed Seeds ofM u c u n a p r u r i en s a

a n t in ut r ien t r a w seeds dr y -h ea t ed a ut ocla ved

tota l free phenolics (g kg-1 D M) 62.3a 32.4b (48) 24.3b (61)ta nnins (g kg-1 D M) 2.5a 1.8 a,b (28) 0.7b (72)

hydrogen cyanide (mg kg-1

D M) 37.5a

12.4b

(67) 8.3b

(78)phytic acid (g kg-1 D M) 7.7a 4.9 b (36) 4.1b (47)L-DOP A (g kg-1 D M) 78.1a 43.0b (45) 58.6c (25)trypsin inhibitor activity (TIU mg-1 pr ot ein ) 78.7a 5.3 b (93) 2.9b (96)R-amy lase inhibitor act ivity (units g-1 sa m ple) 86.4a 18.2b (79) n ilc(100)

hemagglutinat ing act ivity(HU mg-1 protein)

ph yt oh em a gglut in a t in g a ct ivit y r a w seeds dr y -hea t ed a ut ocla ved

erythrocytes from huma n blood groupA 164a 16b (90) 8b (95)B 82a 8b (90) 4b (95)O 14a ni lb (100) n ilb (100)

a Mean of triplicate determina tions expressed on dry w eight basis . TI U, tr ypsin inhibitor unit ; HU , hemagglutinat ing unit . V alueswith the sa me superscript in each r ow do not differ s ignificantly from ea ch other (P< 0.05). V alues in the parentheses indicate the percent loss from ra w seeds.



5/6

a n d U P ) of M . p r u r i en s a s c o m p a re d t o ra w a n d dry -heated seeds. The heat tr eatment a pplied to legumefoods improves their texture, palatability, and nutritivevalue by destroying or inactivating heat-labi le toxiccompounds and other enzyme inhibi tors (Khan et al . ,1979). The low level of B V in the dr y-hea ted sa mplemight be due to heat treat ment w hich causes consider-a b l e n u t r i t i on a l da m a g e t o m e t h ion i n e, t h e m o s t i m -p or t a n t a m i n o a c id i n g r a i n l eg u me s ( S he me r a n dP erkins, 1975). A compar a tive study of dry hea t tr eat -m en t a n d a u t ocl a v in g on t h e p r ot e in q u a l it y of M .p r u r i e n s indicat es tha t aut oclaving is more beneficial .

An overall report on the nut ritional va lue of the seedsof M . p r u r i en s suggests that consumption of properlycooked (autoclaved) seeds of this legume may be useda s a f ood s ou rce f or con s u m in g t r i ba l s . B e s i des t h eprotein isolates of this l i t t le-known pulse might beexploi ted industr ial ly as a source of food formulat iona n d u s ed a s a ce rea l s u pp le m en t . Th e i n t o xi ca t i o nassociated with the overeat ing of velvet beans is prob-ably related to their L-DOPA content ra ther tha n t o anyother antinutritional factor (Duke, 1981; Afolabi et al . ,1985). Cult ivar di fferences ar e known to exist in theL-DOP A content of mucuna beans (J a ya weera , 1981),an d t hese differences sh ould be exploited t o select lowL-D O P A l i n es f or h u m a n n u t ri t i on . F u rt h e r de t a i l e dresear ch on th e ant inutri t iona l substance in this l i t t le-known pulse might also be frui t ful .

ACKNOWLEDGMENT

Th a n k s a re du e t o D r. P . R a k k iy a p p a n , S e n i or S c i-entist , Sugarcane Breeding Insti tute, Coimbatore, forhis help in the analyses of minerals and fat ty acids.

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Table 5. PE R and FE R of Raw and Processed SeedSamples ofM u c u n a p r u r i en s a

r a wseeds

dry-heated

auto-claved

casein(control)

food in t a ke (g) 145.6 180.2 192.4 368.1pr ot ein in diet (%) 10.8 11.2 10.3 10.5ga in in body w eigh t (g) 10.3 22.4 27.6 92.6P E R 0.66b 1.12bc 1.41c 2.43a

F E R 0.07b 0.13c 0.15d 0.25a

a B a s ed o n f i v e d e t er m i n a t i o n s f or e a c h t r e a t m e n t . Av e r a g ei n i t ia l w e ig h t : 4 0 g. Va l u e s w i t h t h e s a m e s u p er s cr i pt i n e a c h

row do not differ s ignificantly from each other (P< 0.05).

Table 6. Biological Evaluation of R aw and ProcessedSeeds ofM u c u n a p r u r i en s a

r a wseeds

dry-heated

a u t o -claved

casein(control)

b iolog ica l v a lu e (%) 58.7b 62.6b 74.5c 83.2a c

t r ue d ig es t ib il it y (%) 48. 5b 68.5c 81.6d 92.5a

net protein ut ilizat ion (%) 28.5b 42.9c 60.8d 77.0a

u t il iz a bl e p rot ei n (%) 9. 0b 13.2b 18.1c 66.5a

pr ot ein (%) 31.4 30.8 29.7 86.3

a Ba sed on f ive determinations for each treat ment . Net proteinutilizat ion ) ( true protein digest ibility biologica l va lue)/100.Ut ilizable protein ) (protein net protein utiliza tion)/100.Protein ) N 6. 25 (d r y w e ig h t b a s i s). Va l u e s w i t h t h e s a m e

superscript in each row do not differ significantly from each other(P< 0.05).

2640 J. Agric. Food Chem.,Vol. 44, No. 9, 1996 Siddhuraju et al.


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Received for review November 27, 1995. Revised ma nuscriptreceived Ma y 30, 1996. Accepted J une 4, 1996.X K.J . tha nkst he M i ni st r y of E nvi r onm e nt a nd For est s , Ne w De lhi , forG ra nt 14/52/89-MAB/RE dt 26.3.1992, an d P .S. a nd K.V. a regrateful to the Council of Scientific and Industrial Research(CSIR), New Delhi, for the award of Research Associateships.

J F 950776X

X Abstract published in Advance ACS Abstracts, Au -gust 1, 1996.


chemical composition and protein quality mucuna pruriens

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