( Tạp Chí KH)TP Hoa Học Và Hàm Lương Aa Trứng GàBai 17 Sua (693 - 697 Ban in)l

Tp ch Khoa hc v Pht trin 2010: Tp 8, s 4: 693 - 697 TRNG I HC NNG NGHIP H NI

THNH PHN HA HC, THNH PHN V HM LNG A XT AMIN CA LNG TRNG TRNG G

Chemical Composition and Amino Acid Content of Chicken Egg White

H Ngc Tr My*, Nguyn Anh Tun, Nguyn Xun Duy

Khoa Ch bin, Trng i hc Nha Trang, Tp. Nha Trang, Khnh Ha *a ch email tc gi lin h: duy.ntu.edu@gmail.com

TM TT Lng trng trng c gi tr dinh dng cao v c nhiu ng dng trong cng nghip thc phm.

Mc ch ca nghin cu ny l xc nh thnh phn ha hc ca lng trng trng g. Kt qu ch ra rng lng trng trng g cha hm m rt cao (88,10%), tro (0,34%), protein (9,78%) v gluxt (0,60%). Protein ca lng trng trng g thuc dng hon ho v cha y cc axt amin thit yu vi t l kh cao (43%). Kt qu nghin cu ny cung cp thm thng tin quan trng v gi tr dinh dng ca lng trng trng g, ng thi gp phn m rng lnh vc ng dng ca n.

T kha: Axt amin, lng trng trng, thnh phn ha hc, trng g.

SUMMARY Egg white has a high nutritional value and has serveral applications in food industry. The

objective of this research is to determine the chemical composition of chicken egg white (CEW). Results showed that CEW had high moisture content of 88.10%, ash of 0.34%, protein at 9.78%, and carbohydrate 0.60%. Protein from CEW was a perfect protein type due to the presence of fully essential amino acids of a very high ratio of 43%. The result provides important information on the nutritional value of chicken egg white as well as its many applications.

Key words: Amino acid, chemical compostiton, chicken egg, egg white.

1. T VN

Trong cc loi thc phm, trng l loi thc phm c gi tr dinh dng cao (ch sau sa ti) v c nhiu c tnh cng ngh qu gi (kh nng to ng, to nh, gi bt, to xp,). V vy, t lu trng m i din l bt lng trng trng tr thnh mt ph gia ph bin cho ngnh cng nghip thc phm (Trng Hng Linh v cs., 2006). Vi vai tr l mt ph gia thc phm, bt lng trng trng c ng dng nhiu trong cng nghip sn xut cc loi ko mm, bnh cao cp, trong cc sn phm hi sn (v d: cng

ngh surimi v sn phm gc surimi)... l nh kh nng lm ng t, to nh, chng kt tinh, tng kh nng kt dnh, tng n, n hi, (Mc Th H Thanh v cs., 2006). Siegel v cs. (1979) chng minh lng trng trng l mt cht lin kt tt i vi cc loi protein tht. Protein m ch yu l ovalbumin t lng trng trng c tnh cht to gel, to bt v kh nng to nh cng vi l cht lng dinh dng cao. Chnh v vy lng trng trng tr thnh mt thnh phn ph liu ph bin s dng trong cng nghip thc phm (Iesel Van der Plancken v cs., 2006).

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Thnh phn ha hc, thnh phn v hm lng a xt amin ca lng trng trng g

Nhu cu s dng bt lng trng trng trong cng nghip thc phm c xu hng tng. Ngnh nui gia cm cng ang trn pht trin mnh, to ra ngun cung cp trng nguyn liu lng trng trng di do. Hn th na, trong mt s lnh vc ch bin thc phm (sn xut bnh m nhn ht g, cng ngh lm bnh ga t), lng trng trng c xem nh l phn nguyn liu cn li. V vy, vic tn dng ngun nguyn liu ny sn xut ra sn phm c ch s gip gia tng gi tr cho nguyn liu trng ng thi gim nguy c thi b, gy nhim mi trng. Mc d lng trng trng g c nhiu tim nng ng dng trong cng nghip thc phm cng nh mt s lnh vc khc, nhng d liu v thnh phn ha hc ca lng trng trng g vn cn nhiu hn ch. Do vy, nghin cu ny c thc hin nhm xc nh thnh phn ha hc ca lng trng trng g. D liu v thnh phn ha hc ny s gip hiu r hn v gi tr dinh dng ca lng trng trng g cng nh m rng tim nng ng dng ca n.

2. VT LIU V PHNG PHP NGHIN CU

2.1. Chun b mu phn tch thnh phn ha hc v axt amin

Trng g s dng trong nghin cu ny l trng g nui cng nghip, c mua ti ch Vnh Hi (Tp. Nha Trang, tnh Khnh Ha) thng 3/2010 t ngun cung cp trng ca mt trang tri nui g. chun b mu cho phn tch thnh phn ha hc v axt amin, 20 trng g c chia lm hai nhm, mi nhm 10 trng. Mi trng c x l tch ring phn v, phn lng v lng trng. Sau , phn lng trng c thu gom li ring cho mi nhm v tin hnh ng nht mu trong 5 pht s dng my ng ha (Hemogenizer LK-21, Yamoto, Japan). Cc mu lng trng trng sau khi c ng nht th em i phn tch cc ch tiu ha hc v axt amin.

2.2. Xc nh thnh phn khi lng

Trng g c x l tch ring phn v, lng v lng trng. Sau , khi lng mi phn c xc nh ring, s dng cn phn tch (AY-210, Shimadzu, Japan) vi chnh xc 10-4g. Thnh phn khi lng ca mi phn c tnh ton nh l t l phn khi lng ca mi phn so vi trng lng ton b trng theo cng thc:

imTPKL 100M

= (%) (1)

Trong : TPKL: Thnh phn khi lng (%) mi: Khi lng thnh phn th i ca

trng M: Khi lng ton b ca trng

2.3. Xc nh thnh phn ha hc Hm lng m c xc nh theo

phng php ca AOAC 950.46 (1995), hm lng tro theo phng php ca AOAC 923.03 (1995). Hm lng protein c xc nh theo TCVN 4321-1(2007) s dng h thng ct NH3 bn t ng Kjeldhal (Vapodest 45, Gerharlt, Germany). Hm lng gluxit c xc nh theo phng php ca Dubois (1956) s dng my quang ph (Spectrophotometry DR 4000, Hatch, USA). hp thu quang hc o bc sng 485 nm.

2.4. Xc nh thnh phn axt amin Phn tch thnh phn axt amin c

thc hin ti Vin Cng ngh sinh hc v Mi trng, Trng i hc Nha Trang. Mu phn tch thnh phn axt amin c thy phn trong dung dch HCl 6N 110oC trong 22 gi. Cc axt amin c phn tch s dng sc k kh ghp ph GC/MS ca hng Agilent (model 6890A plus, USA), s dng ct ZB-AAA (10 m 0,25 mm, Phenomenex, USA). Chng trnh nhit ci t nh sau: 100oC gi trong 1 pht, sau tng ng nhit 15oC/pht n 260oC gi trong 1 pht. Kh mang c s dng l nit. Phn tch trn c thc hin trong ba ln lp li, kt qu bo co l gi tr trung bnh lch chun.

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H Ngc Tr My, Nguyn Anh Tun, Nguyn Xun Duy

2.5. X l s liu

S liu c x l bng phn mm thng k Statistica 9.0 (Stasoft, Tulsa, Ok, USA). Kt qu bo co l gi tr trung bnh lch chun.

3. KT QU NGHIN CU V THO LUN

3.1. Thnh phn khi lng

Thnh phn khi lng ca trng g (Bng 1) bao gm: lng trng chim t l cao nht, gn 2/3 (60,51%) khi lng ton b trng, tip theo l lng (27,75%) v cui cng l v chim 13,22%. Kt qu phn tch thnh phn khi lng ca trng g cng nm trong cc khong gii hn gi tr c cng b bi Roca v cs. (1984) khi nghin cu v cu trc v thnh phn ca 14 loi trng chim khc nhau theo loi. Trong , lng trng trng dao ng t 47,1 - 65,0%; lng t 21,1 - 38,6% v thnh phn v l 6,1 -15,3%.

3.2. Thnh phn ha hc

Bng 2 lit k thnh phn ha hc ca lng trng trng g. Lng trng trng c t l nc rt cao (88,10%), cc thnh phn cn li bao gm tro, protein v gluxit chim t ln lt l 0,34%; 9,78% v 0,60%. Hm lng nc kh cao l kt qu in hnh i vi lng trng trng ti. Kt qu nghin cu ny kh gn vi kt qu ca mt s tc gi cng b. Mc Th H Thanh v cs. (2006) khi nghin cu sy lng trng trng

iu cng cho bit hm lng m ca lng trng trng ti khong 87,6%. Theo c s d liu ca USDA (Release 22, 2009) cng b th hm lng m ca lng trng trng g ti l 87,6%. Hm lng nc cao ca lng trng trng l mt tr ngi ln cho cng ngh lm kh sn xut bt lng trng trng. Cng theo USDA, hm lng tro, protein v gluxt ca lng trng trng g ti ln lt l 0,63%; 10,9% v 0,73%. S khc nhau ca hm lng ba thnh phn ny c l l do s khc nhau v loi trng g cng nh ngun gc ca trng. Trong nghin cu ny, hm lng cht bo khng c xc nh v theo Ayadi v cs. (2008) th hm lng cht bo trong lng trng ti hay bt lng trng trng c pht hin di dng vt.

Mt iu cn quan tm i vi cc nh cng ngh cng nh cc nh sn xut bt lng trng trng l hm lng ng c trong nguyn liu lng trng trng. Mc d, hm lng gluxt chim t l thp (0,60%) nhng c th gy kh khn cho cng ngh sn xut bt lng trng trng. Theo c s d liu ca USDA (Release 22, 2009), lng trng trng ti c cha cc loi ng nh: sucrose, glucose, fructose, lactose, maltose v galactose. c bit l ng glucose chim gn 50% tng cc loi ng trn. S c mt ca ng kh cng vi cc axt amin c sn trong nguyn liu s to iu kin thun li cho cc phn ng sm mu (phn ng Maillard) xy ra. V vy, trong cng ngh sn xut bt lng trng trng cn loi b cc thnh phn ng kh trc khi thc hin cc cng on lm kh.

Bng 1. Thnh phn khi lng ca trng g (n = 25)

Thnh phn T l (%)

V 13,22 1,12

Lng 27,75 3,48

Lng trng 60,51 2,17

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Thnh phn ha hc, thnh phn v hm lng a xt amin ca lng trng trng g

Bng 2. Thnh phn ha hc ca lng trng trng g (n = 3)

Thnh phn Hm lng (%) Hm lng (g/100 g cht kh)

Nc 88,10 0,04 740,34 3,00

Tro 0,34 0,01 2,86 0,13

Protein 9,78 0,20 82,18 1,37

Gluxt 0,60 0,02 5,00 0,20

Bng 3. Thnh phn axt amin ca lng trng trng g (n = 3) so vi mt s kt qu khc Thnh phn (g/100 g khi lng ti)

Axt amin Kt qu phn tch USDA (Release 22, 2009)

Alanine (ALA) 0,54 0,04 0,70

Glycine (GLY) 0,31 0,01 0,41

Valine* (VAL) 0,62 0,01 0,81

Leucine* (LEU) 0,80 0,03 1,02

Isoleucine* (ILE) 0,51 0,01 0,66

Threonine* (THR) 0,42 0,01 0,45

Serine (SER) 0,66 0,04 0,80

Proline (PRO) 0,33 0,01 0,44

Asparagine (ASP) 0,96 0,01 1,22

Methionine Sulfoxide* (MET) 0,36 0,01 0,40

Cysteine (CYS) 0,25 0,01 0,29

Glutamine (GLU) 1,08 0,05 1,55

Phenylalanine* (PHE) 0,50 0,02 0,69

Lysine* (LYS) 0,60 0,01 0,81

Histidine* (HIS) 0,18 0,01 0,29

Tyrosin (TYR) 0,37 0,02 0,46

Arginine (ARG) 0,59 0,02 0,65

Tryptophan - 0,13

TAA (total amino acid) 9,02 0,05 11,75

TEAA (total essential amino acid) 3,91 0,05 5,12

TNEAA (total unessential amino acid) 5,11 0,00 6,64

TEAA/TAA 0,43 0,00 0,44

TNEAA/TAA 0,57 0,00 0,57

(*): axt amin thit yu; TAA: tng axt amin; TEAA: tng axt amin thit yu; TNEAA: tng axt anmin khng thit yu; USDA: B Nng nghip Hoa K.

3.3. Thnh phn axt amin

Thnh phn axt amin ca lng trng trng (Bng 3) bao gm: 3 axt amin chim s lng nhiu nht ln lt l glutamine (1,08 g/100 g), asparagine (0,96 g/100 g) v leucine (0,80 g/100 g)

Lng trng trng cha y 8 axt amin thit yu (VAL, LEU, ILE, THR, MET, PHE, LYS, HIS) vi tng hm lng l 9,02 g/100 g khi lng t, chim 43% tng axt amin c nhn din. y l mt t l cao hn nhiu so vi khuyn co ca FAO/WHO (1973) i vi ngun protein hon ho (36%).

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H Ngc Tr My, Nguyn Anh Tun, Nguyn Xun Duy

iu ny cho thy, protein trong lng trng trng thuc loi protein hon ho. Kt qu ny cho thy, lng trng trng l mt ngun cung cp protein tt cho nhu cu dinh dng ca con ngi.

So snh kt qu ca nghin cu ny vi kt qu cng b bi USDA (Release 22, 2009) cho thy, c mt s khc nhau v hm lng cc axt amin trong lng trng trng ti. Nhn chung, hm lng cc axt amin c xc nh trong mu nghin cu ny thp hn kt qu cng b ca USDA. S khc nhau ny c th l do s khc nhau v chng loi cng nh ngun gc xut x ca trng c s dng trong nghin cu. Tuy nhin, gia cc kt qu ny c mt s im tng ng nh d liu ca USDA (Release 22, 2009) cho thy 3 axt amin chim hm lng nhiu nht cng l glutamine, asparagine v leucine. Tuy hm lng cc axt amin l khc nhau gia hai kt qu nghin cu, nhng t l TEAA/TAA l kh ging nhau mc 43% (nghin cu ny) v 44% theo USDA (Release 22, 2009).

4. KT LUN Hm lng m, tro, protein v gluxt

trong lng trng trng g 9,78%, 0,34% v 0,60%. Protein trong lng trng trng g cha y cc axt amin thit yu vi hm lng cao (43%). Kt qu nghin cu ny s to tin cho nhng nghin cu su hn v lng trng trng g.

Li cm n

Nghin cu ny c h tr mt phn ti chnh t D n Surimi (Pht trin sn phm gi tr gia tng t c nc ngt).

TI LIU THAM KHO

FAO/WHO, WHO Tech. Rep. Ser. No. 522, 118 (1973).

Helrich K, editor 1990. Official Methods of Analysis of the Association of Official

Analytical Chemists. 5th ed. Arlington, Va.: AOAC Inc.

Iesel Van der Plancken, Anm Van Loey, and Mare E. Hendrickx (2006). Effect of heat-treatment on the physico-chemical properties of egg white proteins: A kinetic study. Journal of Food Engineering 75, pp. 316-326.

M. Dubois, K.A. Gilles, J.K. Hamilton, P.A. Rebers, and F. Smith (1956). Colorimetric method for determination of sugars and related substances. Anal. Chem. 28:350 -356.

Mc Th H Thanh, Nguyn Ngc Dng, Trng Hng Linh v L Th Lin Thanh (2006). Nghin cu sy lng trng trng iu bng bc x hng ngoi. Tp ch Nng nghip v Pht trin nng thn, k 2, trang 38-39.

M.A. Ayadi, M. Khemakhem, H. Belgith, and H. Attia (2008). Effect of Moderate Spray Drying Conditions on Functionality of Dried Egg White and Whole Egg. Journal of Food Science, Vol., 73 (6): E 281-286.

P. Roca, F. Sasinz, M. Gonzlez, and M. Alemany (1984). Structure and Composition of the eggs from several avian species. Comp. Biochem. Physiol., Vol. 77A (2), pp. 307 - 310.

D. G. Siegel, K. E, Church, and G. R.Schmidt (1979). Gel structure of non-meat proteins

as related to their ability to bind meat pieces. Journal of Food Science, 44, pp. 1276-1284.

Trng Hng Linh, Mc Th H Thanh, L Th Lin Thanh v Nguyn Ngc Dng (2006). Phn lp vi khun sinh tng hp enzim lipotitic v xc nh hot lc enzim lipotitic trong lng trng trng ti v bt trng. Tp ch Nng nghip v Pht trin nng thn, k 2, trang 69 - 71.

USDA National Nutrient Database for Standard Reference, Release 22 (2009), http://www.nal.usda.gov/fnic/foodcomp/cgi-bin/list_nut_edit.pl. Cited 4/5/2010.

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