nhung van de moi chtosan

8/2/2019 Nhung Van de Moi Chtosan

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TI:TM HIU V MNG BAO

CHITOSAN TRONG BO QUN

RAU QU

GVHD : ThS. Dng Vn Trng

Lp : HTP6ALT

Nhm SV : Hong Trung Ngha 10325441

Lm Th Y Lnh 10330771

L c Minh 10312451

Nguyn Hong Ln 10366921

TP.HCM, ngy 22 thng 1 nm 2012


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Li m u

Hinnay bn cnh vic thu hoch cc loi rau qu vn chng ta cn quan tm hn ht

l lm sao bo qun chng, gi hon ton cht lng bn trong

Trong vic bo qun cc loi rau qu ti rt kh khn, cng vi xu hng hin nay l

con ngi hng n s dng cc sn phm, ch phm t nhin, thn thin vi mi

trng, an ton cho ngi s dng.

y l iu m c rt nhiu nghin cu cng nh ng dng vo thc t, chng ta tm

ra mt phng php khc thay th cho cch bo qun hin nay, gim vic con ngi

tip xc s dng cc ha cht, v ph hp vi xu hng tiu dng an ton thc phm

trn th gii.

Trong nhng nm gn y cc c quan nghin cu Khoa hc Nng nghip nc ta lin

tc cho ra i nhiu ch phm c tc dng bo qun rau ti a li hiu qu s dng

v kinh t cao: Gim c t l h hao, tng thi gian bo qun nhm ko di thi gian

thu hoch v tiu th. Hu ht cc ch phm ny u c ngun gc sinh hc, n gin,

d s dng, sn phm c bo qun bng cc ch phm ny hon ton khng c hi,

an ton cho ngi sn xut ln ngi s dng. Rau qu ni chung l mt loi sn phm

thc phm c tnh thi v. chnh v th p ng cho lu thng, tng tr v s dngth vn quan trng nht chnh l ko di thi gian s dng ca chng.

Yu cu c bn trong bo qun l gi c trng thi t nhin mt cch tt nht, tnh

cht ca rau qu khng b bin i trong thi gian bo qun.

Rau qu l mt mi trng sng m lun sy ra rt nhiu bin i c l, ha hc ,

sinh hc. v ang tn ti nhiu bin php bo qun rau qu: bin php ha hc,

sinh hc, vt l. V cho ti nay th vic s dng nhit thp bo qun vn t ra

chin u th.

Chitossan l mt hp cht sinh hc c tnh u vit rt ph hp cho vic bo qun rau

qu, ngoi kh nng khng vi sinh vt, chitossan cn c kh nng hn ch qu trnh h

hp hiu kh t nhin ca rau qu v th tri cy s c bo qun lu hn v trng thi

t nhin bin i t hn- iu ny c nhiu ti chng minh bng thc nghim.

Vic kt hp bo qun lnh cng vi s dng chitossan bo qun tri cy s mang li

hiu qu cao hn thi gian bo qun di hn, c tnh t nhin bin i t hn.


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MC LC

3.2.thc nghim cho bo qun: .................................................................................31


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Mng Bao Chitosan Trong Bo Qun Rau Qu GVHD:Th.s Dng Vn Trng

CHNG I:TNG QUAN V CHITOSAN:

1.1.Lch s pht hin Chitosan:

Chitin c Bracannot pht hin ln u tin vo nm 1811 trong cn dch chit ca

mt loi nm v t tn l fungine ghi nh ngun gc tm ra n. Nm 1823 Odier

phn lp c mt cht t b cnh cng v ng gi l chitin hay chitine c ngha l

lp v. Nhng khng pht hin s c mt ca Nit. Cui cng c Bracannot v Odier

u cho rng cu trc ca chitin ging cu trc ca xenluloza

Nm 1929 Karrer un si chitin 24h trong dung dch KOH 5% v un tip 50 pht

160C vi kim bo ha ng thu c sn phm c phn ng mu c trng vi thuc

th, cht chnh l Chitosan [1].

Vic nghin cu v dng tn ti, cu trc, tnh cht l ho ng dng ca chitosan

c cng b t nhng nm 30 ca th k XX. Nhng nc thnh cng trong lnh

vc nghin cu sn xut chitosan l: Nht, M, Trung Quc, n , Php. Nht Bn

l nc u tin trn th gii nm 1973 sn xut 20 tn/nm. V n nay ln ti 700

tn/nm, M sn xut trn 300 tn/nm. Theo Know nm 1991 th th trng c nhiu

trin vng ca chitin, chitosan l Nht Bn, M, Anh, c. Nht c coi l nc dn

u v cng ngh sn xut v bun bn chitin, chitosan. Ngi ta c tnh sn lngchitosan s t ti 118000 tn/nm; trong Nht, M l nc sn xut chnh [2].

Vit Nam, vic nghin cu v sn xut chitin, chitosan v ng dng ca chng trong

sn xut phc v i sng l mt vn tng i mi m nc ta. Vo nhng nm

1978-1980, trng i hc Thy sn Nha Trang cng b qui trnh sn xut chitosan

ca tc gi Minh Phng m u bc ngot quan trng trong vic nghin cu,

tuy nhin cha c ng dng no thc t trong sn xut [3]

1.2. Ngun gc:

Chitin c xem l polymer t nhin quan trng th hai ca th gii, c nhiu th haith gii (ch sau xenlulo). L mt polymer ng vt c tch chit v bin tnh t vcc loi gip xc (tm, cua, hn, trai, s, mai mc, a bin), mng t bo nm hZygemycetes, cc sinh khi nm mc, mt s loi to Chitin c mt trong v cc loi gip xc, mng t bo nm thuc h Zygemycetes ctrong sinh khi nm mc, v mt vi loi to . Cn chitosan chnh l sn phm bin tnhca chitin .Chitosan c trong v tm. nc ta, sn phm tm ng lnh chim sn lng ln nht

trong cc sn phm ng lnh. Chnh v vy, v tm ph liu l ngun nguyn liu tnhin rt di do, r tin, c sn quanh nm, nn rt thun tin cho vic cung cp chitin hit


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Cc cng trnh nghin cu ca nhiu nh khoa hc trn th gii chng minh, trong vtm c cha 27% cht Chitin, t cht Chitin ny, h c th chit tch thnh chtChitosan ng dng cho nhiu ngnh kinh t: ho dc, m phm v c bit trongngnh dc phm, cht Chitosan h tr c lc trong vic bo ch ra rt nhiu sn

phm thuc cha c nhiu loi bnh khc nhau.[4]1.3 Cng thc cu to:

1.3.1. Cu trc ha hc ca chitin

Chitosan cu to bi cc n v glucosamine. Chitin c mt rt ph bin ng vt bcthp, c bit c nhiu gip xc, to. Thnh phn ny thng c nhiu trong bt tm,lm nh hng n tiu ha thc n, c bit l tiu ha protein ca ng vt thysinh.Chitin l polisaccarit mch thng, c th xem nh l dn xut ca xenluloz, trong

nhm (-OH) nguyn t C(2) c thay th bng nhm axetyl amino (-NHCOCH3)

(cu trc I). Nh vy chitin l poli (N-axetyl-2-amino-2-deoxi--D-glucopyranoz) lin

kt vi nhau bi cc lin kt b-(C-1-4) glicozit. Trong cc mt xch ca chitin cng

c nh s nh ca glucoz:

Hnh 1: Cu trc ho hc ca chitin

Ph thuc vo ngun gc c im tng vng, chitin xut hin vi hai loi cu trc c

trng, gi l dng v dng . S khc nhau gia hai dng ny c nhn bit bng cc

phng php ph nghim nh ph hng ngoi, ph NMR chp trng thi rn kt hp

vi XRD. Mt dng th ba km ph bin hn l -chitin, nhng xut pht t cc s liu

phn tch, ngi ta vn cho rng dng th ba ch l mt loi khc trong cu trc ca -

chitin.

-chitin ph bin nht trong t nhin, n c mt trong v tm, trong cc loi nhuyn th

thc n ca c voi, trong dy chng (tendon) v v ca tm hm v cua cng nh trong

biu b ca cc loi cn trng Him hn l dng -chitin, c tm ra trong protein


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ca mc ng [5]

Hnh 2: Sp xp cc mch trong phn t chitin

1.3.2. Cu trc ho hc ca chitosan v mt vi dn xut:

Chitosan l dn xut axetyl ho ca chitin, trong nhm (NH2) thay th nhm (-

COCH3) v tr C(2). Chitosan c cu to t cc mt xch D-glucozamin lin kt vi

nhau bi cc lin kt b-(1-4)-glicozit, do vy chitosan c th gi l poly -(1-4)-2-

amino-2-deoxi-D-glucoz hoc l poly -(1-4)-D- glucozamin (cu trc III).

Hnh 3: Cu trc chitosan (poly b-(1-4)-D- glucozamin)

Cng thc phn t: (C6H11O4N)n

Phn t lng: Mchitosan =(161,07)n

Tuy nhin trn thc t thng c mt xch chitin an xen trong mch cao phn tchitosan (khong 10%). V vy cng thc chnh xc ca chitosan c th hin nh sau:

m

O

OH

H NHCOCH3

H

H

O

HH

CH2OH

O

OH

H NH2

H

H

O

HH

CH2OH

nHnh 4: cng thc cu to ca chitosan

chitin chitin chitin


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Trong t l m/n ph thuc vo mc deacetyl ha

ch phm ny cn c tn l PDP: Poly- - (1 4) D- glucosamin

Hay cn gi l Poly- - (1- 4) 2 amino 2- desoxy D- glucosa

Di y l cng thc cu to ca cc dn xut:

Dn xut N,O- Cacboxymetylchitin:

Hnh 5: Dn xut

N,O-

Cacboxymetylchitin

Dn xut N,O-cacbonxymetylchitosan:

Hnh 6: Dn xut N,O-cacbonxymetylchitosan

Dn xut: N,O-axylchitosan:


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Hnh 7: Dn xut: N,O-axylchitosan

Dn xut N-metylchitosan:

Hnh 8: Dn xut N-metylchitosan

So snh cu trc chitin, chitosan, xenluloza:

Hnh 9: Cu trc 1:Chitin , 2: Chitosan , 3: Xenluloza.

1.3.3. deaxetyl ha- DD (Degree of deaxetylation):

L t l thay th nhm (-NHCOCH3) bng nhm (-NH2) trong phn t Chitin


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Hnh 10: Qu trnh deaxetyl ho

Nu:

DD < 50%_ chitinDD 50%_ chitosan

Cc phng php xc nh:

Da vo ph cnh hng t ht nhn proton (H-NMR)

Ph hng ngoi IR

Chng ct chitin,chitosan vi axit photphoric

Phn ng to mu vi ninhidrin

Xc nh theo Nit

1.4.Tnh cht vt l ca chitosan:

-L mt cht rn, xp, nh, hnh vy, c th xay nh theo cc kch c khc nhau.

-Chitosan c tnh kim nh. C mu trng hay vng nht, khng mi v, khng tan trong

nc, dung dch kim v axt m c nhng tan trong axt long (Ph=6), to dung dch

keo trong, c kh nng to mng tt.


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Khi ho tan trong dung dch acid acetic long s to thnh dung dch keo dng, nh

m keo chitosan khng b kt ta khi c mt ca mt s ion kim loi nng nh: Pb 3+,

Hg+,

- Nhit nng chy 309- 311oC.

- Trng lng phn t trung bnh: 10.000- 500.000 Dalton (Li, 1997- Onsoyen v

Skaugrud, 1990) ty loi. Loi PDP c trng lng phn t trung bnh (M) t 200.000

n 400.000 hay c dng nhiu nht trong y t v thc phm. [4]

- Chitosan l mt polymer mang in tch dng nn c xem l mt polycationic

(pH


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-Dn xut O-axyl cu chitin/chitosan.

-Dn xut Otosyl ho chitin/chitosan.

1.5.2. Phn ng v tr N:

-Phn ng N-axetyl ho chitosan.

-Dn xut N-sunfat chitosan.

-Dn xut N-glycochitosan (N-hidrroxy-etylchitosan)

-Dn xut acroleylen chitossan.

-Dn xut acroleylchitosa

1.5.3. Phn ng xy ra ti v tr O, N:

- Dn xut O,Ncacboxymetylchitosan.

- Dn xut N,O-cacboxychitosan.

- Phn ng ct t lin kt -(1-4) glicozit

- Chitosan phn ng vi acid m c to mui kh tan.

- Chitosan tc dng vi It trong mi trng H2SO4 cho phn ng ln mu

tm. y l phn ng dng trong phn tch nh tnh chitosan

1.5.4.Kh nng hp ph to phc vi cc ion kim loi chuyn tip ca chitosan:

- Trong phn t chitin/chitosan v mt s dn xut ca chitin c cha cc nhm chcm trong cc nguyn t Oxi v Nit ca nhm chc cn cp electron cha s dng,

do chng c kh nng to phc, phi tr vi hu ht cc kim loi nng v cc kim

loi chuyn tip nh: Hg2+, Cd2+, Zn2+, Cu2+,Ni2+,Co2+.... Tu nhm chc trn mch

polime m thnh phn v cu trc ca phc khc nhau.

- V d: vi phc Ni(II) vi chitin c cu trc bt din vi s phi tr bng 6, cn phc

Ni(II) vi chitosan c cu trc t din vi s phi tr bng 4.


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trong l mng polime

Hnh 12: Phc ca chitosan vi kim loi

1.5.5.Phn ng c trng khc ca chitosan:

Phn ng Van-Wisselingh: chitosan tc dng vi Lugol to dung dch mu nu trong

mi trng axit sunfuric c mu tmPhn ng Alternative: tc dng vi axit sunfuric to tinh th hnh cu chitosan sunfat

lm mt mu dung dch fucsin 1%

Kh amin nh: Ba(BrO)2, AgNO3, N2O2.

Ct mch bi axit, enzim, bc x

Chitosan phn ng vi acid m c to mui kh tan.

Chitosan tc dng vi It trong mi trng H2SO4 cho phn ng ln mu tm. y l

phn ng dng trong phn tch nh tnh chitosan

1.6.Tnh cht sinh hc ca chitosan:

- Vt liu Chitosan c ngun gc t nhin, khng c, dng an ton cho ngi.

- Chng c tnh ha hp sinh hc cao vi c th, c kh nng t phn hu sinh hc.

- Chitosan c nhiu tc dng sinh hc a dng nh: c kh nng ht nc, gi m, tnh

khng nm, tnh khng khun vi nhiu chng loi khc nhau, kch thch s pht trin

tng sinh ca t bo, c kh nng nui dng t bo trong iu kin ngho dinh dng,

tc dng cm mu, chng sng u.

Ngoi ra cn c tc dng lm gim cholesterol v lipid mu, lm to vi ng mch v hhuyt p , iu tr thn mn tnh , chng ri lon ni tit .- Vi kh nng thc y hot ng ca cc peptide- insulin, kch thch vic tit rainsulin tuyn tu nn dng iu tr bnh tiu ng .- Nhiu cng trnh cng b kh nng khng t bin , kch thch lm tng cng hthng min dch c th, khi phc bch cu, hn ch s pht trin cc t bo u, ung th,HIV/ AIDS .- Chng tia t ngoi, chng nga .-Chitosan khng nhng c ch cc vi khun gram dng, gram m m c nm men v

nm mc Kh nng khng khun ca chitosan ph thuc mt vi yu t nh loi


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chitosan s dng ( deacetyl, khi lng phn t), pH mi trng, nhit , s c mt

ca mt s thnh phn thc phm. Kh nng khng khun ca chitosan v dn xut ca

n c nghin cu bi mt s tc gi, trong c ch khng khun cng c

gii thch trong mt s trng hp. Mc d cha c mt gii thch y cho kh nng

khng khun i vi tt c cc i tng vi sinh vt, nhng hu ht u cho rng kh

nng khng khun lin quan n mc hp ph chitosan ln b mt t bo. Trong ,

chitosan hp ph ln b mt vi khun gram m tt hn vi khun gram dng. Mt s c

ch c gii thch nh sau:

+Nh tc dng ca nhng nhm NH3+ trong chitosan ln cc v tr mang in m

trn mng t bo vi sinh vt, dn ti s thay i tnh thm ca mng t bo.Qu trnh

trao i cht qua mng t bo b nh hng. Lc ny, vi sinh vt khng th nhn cc

cht dinh dng c bn cho s pht trin bnh thng nh glucose dn n mt cn

bng gia bn trong v bn ngoi mng t bo. Cui cng dn n s cht ca t bo.

+Chitosan c th ngn cn s pht trin ca vi khun do c kh nng ly i cc ion

kim loi quan trng nh Cu2+, Co2+, Cd+ ca t bo vi khun nh hot ng ca cc

nhm amino trong chitosan c th tc dng vi cc nhm anion ca b mt thnh t bo.

Nh vy vi sinh vt s b c ch pht trin do s mt cn bng lin quan n cc ionquan trng [6].

+ in tch dng ca nhng nhm NH3+ ca glucosamine monomer pH< 6.3

tc ng ln cc in tch m thnh t bo ca vi khun, dn n s r r cc phn t

bn trong mng t bo. ng thi gy ra s tng tc gia sn phm ca qu trnh thu

phn c kh nng khuch tn bn trong t bo vi sinh vt vi AND dn n s c ch

mARN v s tng hp protein t bo.

+ Chitosan c kh nng ph hu mng t bo thng qua tng tc ca nhng nhm

NH3+ vi nhng nhm phosphoryl ca thnh phn phospholipid ca mng t bo vi

khun.

- C tc dng lm gim ng k s lng vi sinh vt tng s trn b mt thc phm.

Vi hm lng 1,5% gim s lng vi sinh vt trn b mt cam l 93%, trn b mt

qut l 96%, trn b mt c chua l 98% v.v.

- Ngoi ra, Chitosan cn c tc dng lm gim cholesterol v lipid mu, lm to vi ng

mch v h huyt p, iu tr thn mn tnh, chng ri lon ni tit.


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- Chitosan l cht thn m c kh nng hp thu du m rt cao c th hp thu n gp 6-

8 ln trng lng ca n. Chitosan nh phn t c in tch dng nn c kh nng gn

kt vi in tch m ca lipid v acid mt to thnh nhng cht c phn t ln khng b

tc dng bi cc men tiu ha v do khng b hp thu vo c th m c thi ra

ngoi theo phn qua lm gim mc cholesterol nht l LDL-cholesterol, acid uric

trong mu nn c th gip ta trnh cc nguy c bnh tim mch, bnh gt, kim sot

c tng huyt p v gim cn.

- Vi kh nng thc y hot ng ca cc peptide- insulin, kch thch vic tit ra

insulin tuyn tu nn Chitosan dng iu tr bnh tiu ng. Nhiu cng trnh

cng b kh nng khng t bin, kch thch lm tng cng h thng min dch c

th, khi phc bch cu, hn ch s pht trin cc t bo u, ung th, HIV/ AIDS.

- Chng tia t ngoi, chng nga.

1.7..c tnh ca chitasan:

dng trong y t v thc phm, c nhiu cng trnh nghin cu v c tnh ca

Chitosan v a ra cc kt lun sau:

- Chitosan hu nh khng c, khng gy c trn xc vt thc nghim v ngi, khng

gy c tnh trng din [3].- Chitosan l vt liu ho hp sinh hc cao, n l cht mang l tng trong h thng vn

ti thuc, khng nhng s dng cho ng ung, tim tnh mch, tim bp, tim di

da, m cn ng dng an ton trong ghp m.

- Dng Chitosan vi trng lng phn t thp tim tnh mch, khng thy c tch ly

gan. Loi Chitosan c DD =50 %, c kh nng phn hu sinh hc cao, sau khi tim

vo bng chut, n c thi tr d dng, nhanh chng qua thn v nc tiu,

Chitosan khng phn b ti gan v l lch .

- Nhng li im ca Chitosan: tnh cht c hc tt, khng c, d to mng, c th t

phn hy sinh hc, ho hp sinh hc khng nhng i vi ng vt m cn i vi cc

m thc vt, l vt liu y sinh tt lm mau lin vt thng.

- Chitosan khng c hoc c tnh rt thp trn xc vt thc nghim v n c th c

s dng an ton trn c th ngi

dng trong y t v thc phm, c nhiu cng trnh nghin cu v c tnh caChitosan- Ngay t nm 1968, K.Arai v cng s xc nh Chitosan hu nh khng c


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(almost non- toxic ), ch s LD 50 =16g / kg cn nng c th , khng gy c trn xcvt thc nghim v ngi, khng gy c tnh1.8.Tc dng sinh hc a dng :+ Tnh khng nm .

+ Tnh khng khun vi nhiu chng loi khc nhau .+ Kch thch s pht trin tng sinh ca t bo .+ C kh nng nui dng t bo trong iu kin ngho dinh dng .+ Tc dng cm mu+ Chng sng u1.9.Sn xut chitosan:1.9.1.Nguyn liu:

Ngun nguyn liu phong ph nht sn xut chitosan l t ph liu ca ngnh thy

sn: t v cc loi gip xc (tm, cua, hn, trai, s, mai mc, a bin ,....)

Chitosan c trong v tm. nc ta c b bin di, lng thy sn ln, c tnh hng

nm Vit Nam c khong 30.000 tn v tm ph thi t cc nh my tm ng lnh, ch

ring tnh Bc Liu mi ngy thi ra 35 tn u v v tm (theo Nguyn Ngc

T-Bo co ti hi ngh bng ton quc ln th 3).

Tr lng chitin trong thin nhin c tnh 100 t tn/ nm nhng lng tiu th ch c

1100-1300 tn/nm. iu ny chng t nguyn liu khai thc l rt di do [19]. Sn

phm tm ng lnh chim sn lng ln nht trong cc sn phm ng lnh. Chnh v

vy, v tm ph liu l ngun nguyn liu t nhin rt di do, r tin, c sn quanh

nm, nn rt thun tin cho vic cung cp chitin v chitosan. Cc cng trnh nghin cu

ca nhiu nh khoa hc trn th gii chng minh, trong v tm c cha 27% cht

Chitin, t cht Chitin ny, h c th chit tch thnh cht Chitosan

Sn lng nh bt cc loi gip xc trn th gii l: 6 triu tn/nm to ra ngun ph

liu n nh l nguyn liu cho sn xut chitosan

Trong nm 2007, sn lng thy sn c nc c t 3,9 triu tn trong khai thc t1,95 triu tn, nui trng 1,95 triu tn. D kin, nm 2008, tng sn lng thy sn s

t 4,1 triu tn, trong nui trng l 2,15 triu tn, khai thc 1,95 triu tn Ngy nay,

ngh nui tm v ch bin ng lnh nhiu nc trn th gii ang pht trin v nht

l Vit Nam. Song song vi n, mi nm li c hng triu tn v tm b vt b, nhng

bn trong n li cha c mt kho tng qu bu cht Chitosan- hu dng cho nhiu

ngnh kinh t.


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Bng 1: Hm lng chitin trong v mt s ng vt gip xc

(Theo: Chitosan-Its productinal and potential Zakaria M.B)

1.9.2.Quy trnh sn xut Chitasan:

Nguyn tc chung ca vic sn xut Chitosan:

Cng ngh sn xut Chitosan da trn nguyn tc loi b mui calcium, protein v cc

tp cht khc c trong v tm, cua

Chitosan l cht rn, xp, nh, c th xay nh khch thc khc nhau.C mu trng hay

vng nht.khng mi v, khng tan trong nc, dung dch kim v acid m c.Nhngtan trong acid long (PH= 6-6.5) to dung dch keo trong, c kh nng to mng tt,

nhit nng chy 3090C 3110C.Trng lng phn t trung bnh 10.000-500.000

dalton ty loi

Chitosan l mt polyamine n c xem nh l mt polymer cationic c kh nng cho

cc kim loi bm vo cc b mt in tch m v to ra phc cht vi kim loi kt ta ,

noh72 vo nhng bin i ca nhm OH qua phn t copolymer v kh nng to nhm

NH2

Trn mi mc xch ca phn t chitosan c 3 nhm chc, cc nhm chc ny c kh

nng kt hp vi cht khc to ra cc dn xut c li khc nhau ca chitosan (O-

caylchitosan, N-acetylchitosan, N-phatylchitosan)

Trong ph thi thy sn (v tm, u tm, mai mc,v cua) c cha ch yu l:

protein, chitin v cht khong trong chitin chim khong 14-35%. Nh vy mun thu

c chitin ta cn loi b protein v khong cht sau deaxetyl ha chitin thu cchitosan. [4]

STT Phn loi Hm lng chitin theo trng lng (%)1 u tm 112 V tm 27

3 V tm ph thi hn hp 12-18

4 V tm hm 37

5 Cng cua tuyt 246 Chn cua tuyt 32

7 Mai mc ng 30-35

8 a bin 34-49


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Hnh13 : S sn xut chitosan

Nguyn liu:

V tm, cua, mc..t cc nh my ng lnh c thu gom v s l s b bng cch r

sch, sy kh v nghin nh.

Loi b protein:

Protein c loi b bng nhiu bin php khc nhau, c th loi b bng phng php

sinh hc (dng enzim), hoc bng phng php ha hc (dng kim hoc axit),c hc.

+ Dng phng php sinh hc:

Trong phng php ny ngi ta c th dng cc ch phm enzim proteaza hoc hin

nay ngi ta ang nghin cu s dng cc chng vi vt phn hy protein.

u im ca phng php sinh hc l sch, gim chi ph, to nhng cht thi hu c dphn hy nhng lng protein tch ra khng trit

X l

Nguynliu

Loi khong

Tch protein

Chitin

Deacetyl ha

Chitosan


19/39


+ Phng php ha hc:

Protein thng c loi b bng axit HCl long hay s dng dung dch kin NaOH,

KOH 5%

Phng php ny c u in hn v tch c trit protein song li to ra nhiu cht

thi kh x l, tn nng lng, khng n nh v lm thay i khi lng phn t chitin

do mch b ct ngu nhin dn n thay i nht. Trong cng nghip hin nay

phng php ha hc vn c s dng rng ri v ph bin hn c

+ Phng php c hc:

Nguyn liu c sy kh v nghin sau khi tch tp cht, sau dng qut gi

phn loi, phn protein nng hn c tch ra khi hn hp

u im ca phng php ny l c th thu c lng protein ti s dng vo vic

khc nhng nhc im chnh l tch khng chit nn chitin thu c c tinh

khit khng cao

Loi mui v c v tp cht:

Mui v c (ch yu l CaCO3) thng c loi ra bng vic s dng axit HCl long

c kt hp un si 120C trong khong 1-2 gi .

Deaxetyl ha:Sau khi tch tp cht, cht v c, protein ta thu c chitin

S dng dung dch NaOH c deaxetyl ha chitin thu c chitosan, ty thuc vo

mc deaxetyl m ta thu c cc ch phm chitosan c DD khc nhau, qu trnh

ny c khng ch bng nng NaOH (15M), nhit (150C) v thi gian 1-1,5

gi [8]

1.9.3.Mt s c s ang nghin cu v sn xut chitin-chitosan Vit Nam:

- Trung tm ch bin trng i hc thy sn Nha Trang: sn xut chitin cht lng cao.

- Vin khoa hc Vit Nam kt hp vi x nghip hy sn H Ni: sn xut chitin ng

dng trong nng nghip.

- Trung tm cng ngh sinh hc v sinh hc thy sn phi hp vi i hc y dc thnh

ph H Ch Minh, phn vin khoa hc Vit Nam, vin khoa hc nng nghip Vit Nam.

1.10. ng dng ca chitosan:

Chitosan c ng dng nhiu trong cc lnh vc:

- Trong y t: nguyn liu thuc cha bnh, t dc, vt liu y sinhT h k d d k h ti t i UV


20/39


- Trong thc phm: bo qun rau qu, tri cy, ph gia thc phm- Trong cng nghip: x l nc thi, nc sinh hot- Trong nng nghip: lm phn bn cho rau sch1.10.1. Cc ng dng ca Chitosan trong cng ngh thc phm:

Trong cng ngh thc phm, vt liu Chitosan c dng bo qun ng gi thc n,

bo qun hoa qu ti v n to mng sinh hc khng c. Ngi ta to mng

Chitosan trn qu ti bo qun qu o, qu l, qu kiwi, da chut, t chung, du

ty, c chua, qu vi, xoi, nho,...

L mt polyme dng an ton cho ngi, li c hot tnh sinh hc a dng, Chitosan

c a vo thnh phn trong thc n: sa chua, bnh ko, nc ngt, ...

Nht bn c nhng sn phm n king c cha Chitosan lm gim cholesterol v

lipid mu, gim cn nng, chng bo ph, dng trnh nguy c mc bnh tim mch,

tiu ng (bnh m, khoai ty chin, dm, nc chm...) c bn rng ri trn th

trng .

C quan bo v mi trng ca M (USEPA) cho php Chitosan khng nhng c

dng lm thnh phn thc n, m cn dng c trong vic tinh ch nc ung. Nm

1983, B thuc v thc phm M (USFDA) chp nhn Chitosan c dng lm cht

ph gia trong thc phm v dc phm.[2]Chitosan chnh thc c T chc y t th gii (WHO) cho php dng trong y hc

v thc phm [9]

N-cacboxymetyl chitosan cn c dng nh antioxidant bo qun thc phm do

chng c kh nng kt hp vi kim loi (Fe) l nhng cht xc tc ca qu trnh i ha

du m, ngn cho cc sn phm cha du m khi b i ha.

Cc ng dng ca Chitosan trong cng ngh thc phm

- L sn phm thay th hn the. Chitosan l cht ph gia bo qun tt cho gi v bnhcun nhit phng v bo qun tt n 26 ngy T= 8 oCTrong ch bin bo qun gi th lng Chitosan c dng tt nht l 2,5g/kg tht vc a vo giai on xay nhuyn cng vi mui v gia v trc khi cho nc mmca quy trnh sn xut gi truyn thng.Trong ch bin bo qun bnh cun th lng Chitosan c dng tt nht l 24g dungdch 3,5% cho 1kg bt nc v c a vo giai on trc khi trng bnhSn phm gi v bnh cun c ph gia Chitosan gi thnh ph hp vi an ton sckho.- Vt liu Chitosan c dng :

+ Bo qun ng gi thc n ,+ bo qun hoa qu ti v n to mng sinh hc khng c . Ngi ta to mngPDP t t i b l ki i d h t t h d t


21/39


c chua, qu vi, Xoi, nho ...V bc thc phm bng mng Chitosan c php s dng Canada v M t lu .- L mt polyme dng an ton cho ngi, li c hot tnh sinh hc a dng, Chitosan c a vo thnh phn trong thc n : sa chua, bnh ko, nc ngt, ...

- Sn phm n king c cha Chitosan lm :+ Gim cholesterol v lipid mu.+ Gim cn nng.+ Chng bo ph.+ Dng trnh nguy c mc bnh tim mch, tiu ng ( bnh m, khoai ty chin,dm, nc chm...) c bn rng ri trn th trng .- Liu php y hc iu tr bnh bo ph c xut l ch n king vi ccthc n c Chitosan v axit ascorbic ( vitamin C) cho kt qu gim cn tt .- ng dng quan trng trong gi xc xch v... thy snT trc n nay, vic bo qun cc loi thc phm ti sng giu m, d h hng

nh tht, c... trong iu kin kh hu nng m ca nc ta l mt trong nhng vn v ang c cc nh sn xut, ch bin v cc nh khoa hc quan tm, nn sau khi vbc chitosan t v tm c hon thnh, cc nh nghin cu ngh ngay n vicdng mng bc chitosan t v tm ny lm v bc xc xch.+ Cc v bc ny khi cho hn hp nguyn liu xc xch vo th dng my nhi quay tay.Khi nhi hn hp nguyn liu vo v bc xong th buc li hai u. Do trong thnh

phn c nhng cht ph gia nn lp chitosan ny kt dnh cc mao mch ca v tmli vi nhau, vi p lc ca my nhi tay, v bc khng b nt, m tip tc bm st vonguyn liu bn trong to thnh nhng hnh xc xch xinh xn. Ngoi vic gip cho sn

phm xc xch c hnh dng p, lp v mng chitosan ny cn c tc dng c bit l

khng lm mt mu v mi c trng ca hn hp nguyn liu xc xch.+ S dng v bc chitosan bo qun thy sn ti v kh. i vi c ti cc tc gi tin hnh x l ly rut, mang ( nguyn con hoc fil...) ri ra. Sau , nhng c x l vo dung dch chitosan c pha sn cc nng 0,5%, 1%, 15%, 2%, 2,5%ty theo ln ca tng loi c. Sau c ro trong t mt khong 10 pht gipmng chitosan c nh hnh ri cho vo t cp ng... Sau 18 ting ng h c thtin hnh r ng. C l nguyn liu c c lng lo, nhiu nc. Trong qu trnh cpng chm (nhit -25oC) s xy ra hin tng mt nc, lm cho trng lng ca cgim. Mt khc, do mi trng trong t cp ng l khng kh lnh v kh nn nckhuch tn t c tht c ra b mt ca c v t b mt ca c ra mi trng bn ngoi rt

ln. Tuy nhin khi s dng mng bao chitosan t v tm th khc phc c hin tngny, chng t vic s dng mng bao chitosan bao ph b mt ca c l rt hiu qu.c bit khi cho c vo nc v nu chn, dung dch chitosan khng lm thay i mi vca sn phm. Cn i vi thy sn kh nh c kh v c mc... th tin hnh pha dungdch chitosan 2% trong dung dch axit acetic 1,5%. Sau nhng c v mc vo dungdch c pha, lm kh bng cch sy nhit 30oC c qut gi. Sn phm thu cc th bo qun tt nhit bnh thng... Ty theo m ca c v mc m sn

phm c thi gian bo qun khc nhau, m cng thp thi gian bo qun cng di.Vi m 26-30%, c kh bo qun c 83 ngy, mc kh gi c 85 ngy cn m 41 - 45% th c kh gi c 17 ngy, mc kh c 19 ngy [10]

Tm li, ch phm Chitosan c dng trong thc phmDng bo qun thc phm, hoa qu, rau ti...


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Lc trong cc loi nc qu p, bia, ru vang, nc gii kht...

L thnh phn b dng a vo thc phm, thc n, bnh ko, nc gii kht.

Dng lm thuc b dng c th (functional food, functional drug) gim cholesterol

mu, lipid mu, h huyt p, gim cn nng, chng bo ph, tng cng min dch c

th, iu tr bnh tiu ng, phng chng u v ung th.

L ph gia khng c bo qun thc phm khi thiu thi.

Hnh 14. Hnh so snh gia vic khng dng (tri) v dng (phi) mng bao chitosan

trong bo qun du ty [11]

1.10.2 ng dng trong y hc:

Chitosan cn c kh nng chng vim cp trn m lnh. Bng cu thng kiu mi, kthut cao, c thnh phn cu to bi cht Chitosan. So vi cc loi bng thng, tc cm mu, tnh st khun v thi gian lnh m khi s dng loi bng ny c hiu qu hngp nhiu ln.- V t lu, mt s chuyn gia Trung tm Huyt hc thuc Vin Hn lm Y hc Ngacng pht hin, Chitosan c th ngn chn s pht trin ca chng nhi mu c timv bnh t qu.- Nh vo tnh u vit ca Chitosan, cng vi c tnh khng c, hp vi c th, t

tiu hu c, nn Chitosan c ng dng rng ri v c hiu qu trong k nghbo ch dc phm+ Lm thuc cha bng.+ Gim au.+ Thuc h cholesterol.+ Thuc cha bnh d dy.+ Chng ng t mu.+ Tng sc khng.+ Cha xng khp.- C tc dng h tr iu tr bnh ung th.

- Thuc kem Pokysan c tc dng khng khun, khng nm, c bit l chng nmCandila albicans, khng gy d ng v tc dng ph, c kh nng cm mu, chng xng


23/39


chng ln da non v gim bt au n cho ngi bnh. ng dng vt liuchitin/chitosan t d phm ca ngnh ch bin thy, hi sn (v tm, cua, mai mc) catp th cn b khoa hc n Phng Plyme dc phm (Vin Ha hc-Vin Khoa hc vCng ngh Vit Nam). Thuc c th nghim lm sng trn 500 bnh nhn bng

nng v bng su ti Vin bng Quc gia v cc bnh vin khc Vit Nam vi hiuqu tt ngang thuc bng nhp ngoi ca M v n nhng gi r hn nhiu. Cngtrnh ny c nhn Huy chng vng ti Hi ch quc t hng cng nghip Vit

Nam nm 2001, c cp bng c quyn gii php hu ch nm 2003, Huy chngng ti Hi ch sng to quc t Seoul 12/2004, gii thng FAWICH ti nng sngto n v Bng danh d ca Tng Lin on Lao ng Vit Nam. Cng ngh sn xutthuc ny cng c cho bn ch cng ngh TECHMARK Vit Nam nm 2003. PhGio s, Tin s Nguyn Th Ngc TT Chitosan, ngi ta bo ch ra nhiu loi thuc iu tr cc bnh nh: nhim x,cha bng, gim au, thuc h cholesterol, cha bnh d dy, ng t mu v cha

c c bnh ung th. c bit ti Vit Nam, Vin Vacxin Nha Trang thu gom hngngn tn v tm c thi ra t cc nh my ch bin ng lnh ti a phng nghin cu v sn xut ra 2 sn phm Chitosan cha bo ph v Glusivac iu tr thoiho khp. Hai loi thuc ny c B Y t cp php lu hnh ton quc vo uthng 6/2005.1.10.3.ng dng trong cc lnh vc khc:

Chitin/chitosan v cc dn xut ca chng c nhiu c tnh qu bu nh: c hot tnh

khng nm, khng khun, c kh nng t phn hu sinh hc cao, khng gy d ng,

khng gy c hi cho ngi v gia sc, c kh nng to phc vi mt s kim loi

chuyn tip nh: Cu(II), Ni(II), Co... Do vy chitin v mt s dn xut ca chng c

ng dng rng ri trong nhiu lnh vc: Trong lnh vc x l nc thi v bo v mi

trng, dc hc v y hc, nng nghip, cng nghip, cng ngh sinh hc, m phm,

cng ngh giy,dt

1.10.3.1. X l nc:T trc ti nay , nc ta cht keo t c s dng lng trong nc sinh hot lnhm sunfat (thng gi l phn n) hoc nhm kali, nhm amon sunfat (thng gi

chung l phn kp) hoc dung dch phn nc (thng thng l dung dch (phn nhmst). Nhm phng chng mt s bnh tt, bnh dch ngi ta cn s dng mt s hacht khc nh clo (clo lng, nc javen, bt ty) c tc dng dit khun; vi hiuchnh pH; natri silicofluorua chng bnh su rng; polyacrylat hon thin qutrnh lng trong nc...ng dng nhng tin b k thut vo sn xut cc ha cht c hiu qu x l nc tthn cc loi phn n, phn kp truyn thng s dng hng trm nm nay.-Vt liu hp ph sinh hc mi v kh nng x l kim loi t nc thi

Nc thi ca hot ng khai thc m, m kim loi, nh my in, ch to thit b inv c bit l hot ng ca cc t hp nhin liu ht nhn, cc c s quc phng, v.v...

c cha cc kim loi c c tnh cao nh crm, caimi, ch, thy ngn, niken, ng cnc x l trc khi thi. Kt ta ha hc, oxy ha - kh, lc c hc, trao i ion, tch

h h t t li th l h h h d i t h


24/39


cc kim loi nng khi dng thi.Hp ph sinh hc l phng php s dng cc vt liu sinh hc tch kim loi hay cchp cht v cc ht khi dung dch. Trong nhng nm gn y, phng php ny cnh gi l mt trong nhng phng php hiu qu v c kinh t v k thut loi b

cc kim loi gy nhim bn ngun nc mt v nhiu loi nc thi cng nghip. Olinv Bailey a ra 12 loi cht hp ph c kh nng tch kim loi khi cc dng thivi chi ph thp. Trong s 12 loi ny, chitosan c dung lng hp ph cao nht i vikim loi.Chitosan c kh nng hp ph tt cc kim loi nng. Do c tnh ca nhm amino t dotrong cu trc chitosan c to thnh khi deacetyl ha chitin, cc phc chelat ca nlm cho kh nng hp ph kim loi tng gp 5 n 6 ln so vi chitin. Khi ghp mt snhm chc vo khung cu trc ca chitosan s lm tng kh nng hp ph kim loi cachitosan ln nhiu ln. to iu kin tt cho qu trnh chuyn khi, ng thi tngdung lng hp ph kim loi ca chitosan,bin tnh chitosan hp ph kim loi nng trn

mng li lin kt mch thng v cho nhau. Kt qu l to ra c nhiu loichitosan bin tnh c dung lng hp ph kim loi cao.- Volesky, Holan, Wase v Foster cng nghin cu mt s cht hp ph sinh hc vkh nng gi cc nguyn t phng x nh urani, thori. H nhn thy kh nng ngdng rng ln ca cc loi cht hp ph sinh hc trn c s chitosan bin tnh v vychng c tp trung nghin cu, pht trin v thng mi ha . Cc cht hp phsinh hc dng t nhin thng mm, trong dung dch nc c xu hng kt t hocto gel. Hn na, dng t nhin mng li ca chng thc t khng c kh nng hp

ph. S di chuyn ca kim loi nhim bn vo mng li giam gi ng vai tr rt quantrng trong qu trnh ch to vt liu hp ph sinh hc. Cn thit phi cung cp s h tr

vt l v tng cng s thm nhp ca mng giam gi kim loi ca cht hp ph sinhhc trn cc loi gi th khi chun b vt liu hp ph sinh hc. Nhiu vt liu hp phsinh hc vi cc loi mng chitosan bin tnh trn cc gi th khc nhau c nghincu cho mc ch ny.Mt nhm tc gi thuc Phng nghin cu k thut cng trnh ca qun i M kt hpcng Trung tm nghin cu & Qun l cht thi ca y ban Qun l Ti nguyn Thinnhin v Trng i hc Tng hp Illinois kt hp nghin cu mt loi vt liu hp

ph sinh hc vi mng chitosan trn nhm oxit.- Vt liu mng chitosan bin tnh trn gi th composit s - nhm oxit t 153,8 mgCr6+/g (vi nng ban u ca Cr6+ u 1000mg/l). nh hng ca cu trc l,

phn b kch thc l xp v gi tr pH ti dung lng hp ph rt r rt. Ni chung,vt liu c b mt ring 80 - 105 m2/g vi kch thc ht 100 - 150 micron l thch hp. gi tr pH thp, dung lng hp ph tng. S c mt nng cao ca ion sunfat vclorua s lm gim kh nng hp ph kim loi.CHNG II:NG DNG MNG BAO CHITOSAN TRONG BO QUN RAU

QU

2.1. Thc trng trong vic bo qun rau qu hin nay:

Hin nay, nc ta ch c mt s doanh nghip ln v cc siu th c phng thc tn

tr tri cy nhit lnh. Cn li, a s cc va thu mua tri cy cng nh nng dnu thu hoch v bn tri cy theo tp qun, khng c qui trnh bo qun sau thu hoch.


25/39


iu ny gy nh hng khng nh n cht lng sn phm v hiu qu kinh t. Thi

gian gn y vn ny c cc nh vn rt quan tm v c bit cc cng trnh

nghin cu bo qun tri cy sau thu hoch cng ang cho nhng kt qu kh quan

Vn bo qun tri cy xut khu:

Sn phm tri cy ca nc ta, c bit tri cy ca cc tnh ng Bng Sng Cu Long

c nhiu li th v chng loi, sn lng v cht lng ca tri cy min nhit i

nhng vic bo qun xut khu vo cc th trng ln nh Nht, M, EU cha

ngang tm vi sn lng thu hoch hng nm.

C nhiu nguyn nhn trong vn ny, trong vic bo qun cha c u t v

cng ngh v h thng thit b bo qun mt cch tng xng vi doanh nghip c

thng hiu tri cy xut khu.

Ti th trng trong nc t nhiu nm nay gi bn tri cy vo thi im thu hoch r

thng bp bnh, do sn phm cng chng loi nhiu vo thi im thu hoch, bnh

qun khong 2 thng/v, lm cho vic iu tit tiu th sn phm gp nhiu kh khn,

sn phm tri cy c tiu th dng ti l ch yu ti a phng v trong nc,

nn thng gy ng, sn phm thng b h hng. Trong thc t sn phm tri cy

thng c thu hoch thm ch khi cha n thi im thu hoch, a s tri cythng khng qua khu kim tra cht lng v v sinh an ton thc phmTrong

ch mt s lng tri ti tiu chun phm cp c phn loi bo qu kho lnh c

nhit v m thch hp cho tng loi tri. ng ch , hin do nc ta c rt t cc

kho bo qun nn ch ph bo qun trong cc khu thu hi, bao gi v vn chuyn lnh

xut khu rt cao. y cng l nguyn nhn hn ch vic ng dng cc tin b k

thut v bo qun sn phm cc trung tm pht trin cy n qu trong c nc.

2.2.C s khoa hc ng dng chitosan trong bo qun tri cy, rau qu:

2.2.1..Cc qu trnh xy ra khi bo qun rau qu ti:

Qu trnh bin i vt l:

S bay hi nc:

Trong rau qu th phn chim nhiu nht l nc t 65-95% ty thuc vo tng loi

qu. Sau khi thu hi rau qu b mt hm lng nc trong sut qu trnh bo qun do

tham gia vo qu trnh h hp hoc bay hi vo mi trng. y l nguyn nhn chnh


26/39


lm cho rau qu b hao ht khi lng so vi ban u. S mt nc cn lm tng kh

nng nhy cm vi s bin i nhit v kt qu l lm tng cng h hp ca qu.

Khi rau qu mt i 5-10% khi lng chng s b ho v h hng nhanh chng. Do s

chnh lch m gia qu v mi trng. Tc bay hi ph thuc vo:

Cu to v hnh thi ca m che ch: nu phn v cu to bi t bo cng, chc,nguyn

vn s lm gim tc mt nc

iu kin mi trng: nhit cng cao, m khng kh cng thp th tc bay hi

nc cng nhanh

Tc chuyn ng ca khng kh: cng cao th nc bay hi cng nhiu

S gim khi lng t nhin:

Nguyn nhn l trong qu trnh bo qun qu b mt nc v mt cht kh do h hp.

Qu trnh ha hc:

ng: B gim ng k do h hp, tuy nhin nhng loi qu m khi thu hi hm

lng ng cha cao th trong thi gian bo qun dng c th tng ln do tinh bt

chuyn ha thnh.

Tinh bt: C th tng hoc gi ty thuc vo tng loi rau qu. Nu tinh bt t ti

hn th trong qu trnh bo qun hm lng tinh bt s gim (v d: chui xanh) cn nuchua cao th trong bo qun li tng do tinh bt c tng hp (v d: u non)

Protopectin: C th b phn gii thnh pectin ha tan lm yu cc lin kt v qu b mm

ra.

Cc axit hu c: Hm lng axit hu c gim dn lm chua ca rau qu gim

Cc vitamin: Gim i rt nhanh do tc ng ca emzim ni bo v s oxi ha

Cc cht mu: (clorofil, carotenoit,flavonoit) di tc dng ca oxi khng kh s b

chuyn ha lm bin i mu sc t nhin ca qu, mt s cht mu mi c tng

hp. Lng chlorophill b mt i thay vo l s tng ln ca cc cu t mang mu

khc nh carotenoid (to cho qu c mu vng, da cam v mu ). Cc qu trnh ny

u c s tham gia ca enzim.

Cc hp cht phenon: polyphenon b oxi ha bi men PPO to thnh flobafin c mu

nu lm mt mu sc ti ca qu khi bo qun.

Qu trnh h hp


27/39


Trong qu trnh sinh trng v pht trin ca qu lun lun xy ra cc qu trnh ng

ha v d ha: khi qu bt u pht trin v cn ang trn cy th ch yu xy ra qu

trnh ng ha l ch yu, l qu trnh tng hp cc cht hu c cho qu nh tinh bt,

ng, cht khong.qu ngy cng pht trin y cho ti khi chn: kch thc qu

tng ln, mu sc qu thay i r rng

Khi qu c thu hi vn xy ra qu trnh sng ca rau qu nhng lc ny trong rau qu

ch yu xy ra qu trnh d ha: l qu trnh s dng cc cht hu c c sn

duy tr s sng ca qu. Trong rt nhiu nhng bin i xy ra sau khi thu hi rau qu

th h hp l ch yu.

H hp s dng tinh bt hoc ng v cc hp cht khc. Di tc dng ca oxi khng

kh, cc mch hidrocacbon b b gy v sn phm thu c l CO 2 v nc. Phn ng

ny ta ra nng lng di dng nhit.

Khi lng oxi trong khng kh c cung cp y th qu trnh trn xy ra rt mnh

m v bin thin theo tng thi k bo qun. V kt qu ca cc qu trnh ny l rau qu

ngy cng b bin i su sc cho ti khi hng hn. Cng trong qu trnh ny c nhng

phn ng lm tng cht lng ca rau qu nh s chuyn thnh ng ca tinh bt

Qu trnh ny l h hp hiu kh: c s tham gia ca oxi khng kh, sn phm ca qutrnh l CO2, H2O v nhit. Tiu biu l phn ng:

C6H12O6 + 6O2 = 6CO2 + 6H2O + 673 KCal

Khi oxi trong mi trng gim xung khon thp hn 2 % th qu trnh ln men s thay

th cho qu trnh h hp hiu kh. Qu trnh h hp ym kh ny to ra mt lng ln

cc cht trung gian trong ng k nht l qu trnh bin i ng thnh ru v kh

cacbonic. Chnh nhng sn phm trung gian ny lm qu trnh h hng ca qu xy

ra nhanh hn bng vic lm bin i mu sc, mi v v trng thi qu mt cc su

sc.Tiu biu l phn ng:

C6H12O6 2C2H5OH +2CO2 +28 Kcal

Nh vy khi s thng kh trong khi bo qun km s lm tng nng kh CO 2 , nhit

xung quanh qu v to mi trng thun li cho h hp ym kh v cc vi sinh vt

pht trin, kt qu l qu s b h hong nhanh chng. V vy vic m bo s thng kh

mt cc thch hp trnh h hp ym kh v m bo h hp hiu kh xy ra thch hp l

rt quan trng v c ngha quyt nh n cht lng ca qu trnh bo qun.


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Nhng loi qu c qu trnh h hp tng ln rt nhanh chng v sau li gim xung

gi l h hp t bin (Climacteric), v d nh c chua v xoi. Cn nhng loi qu m

trong sut qu trnh bo qun s h hp lun gim th cng h hp khng c im

t bin (non-climacteric) nh to, nho Kh etylen to ra trong sut qu trnh h hp

l nguyn nhn quan trng thc y qu trnh chn ca qu. Etylen l mt hormone thc

vt t nhin lin quan n qu trnh sinh trng, pht trin, chn v s lo ha ca thc

vt. Ngi ta cho rng phytohormone ny thc y qu trnh chn ca rt nhiu loi qu

nh: chui, da, c chua, xoi, da hu v u . N c to ra nhiu nng khc

nhau ph thuc vo nhiu loi qu. Nhng khi nng ethylene t t 0,1 n 1,0 ppm

(phn triu) th bt u xy ra qu trnh chn ca qu vng nhit i. Sn phm ethylene

trong qu l tn hiu cho hot ng ca nhiu loi enzyme khc nhau dn n nhng

thay i sinh l nh: qu c s thay i mu sc t xanh sang , trng thi qu chuyn

sang mm v c mi v khc nhau.

Nh vy trong qu trng bo qun qu cn phi hn ch h hp trnh tn tht cht

kh ng thi phi tuyt i trnh h hp ym kh. y l mt bi ton ti u quan

trng quyt nh ln ti cht lng bo qun

2.2.2.S h hng trong qu trnh bo qun:- Do vi sinh vt:Vi sinh vt thm nhp t mi trng

- Do h hp

- Do s bay hi nc

- Do hoy ng ca enzym

- Do s t bin i cc cht

- Do tc ng c hc

- Do tc ng ca nhng ha cht bo v thc vt.

2.3.Yu cu ca mt bao b sinh hc:

Bao b sinh hc l sn phm t nguyn liu t nhin.Bao b t vt liu sinh hc phi p

ng c cc tiu chun nh:

- Tnh chng thm

- c quang sinh hc

- Tnh co gin

- C th ng du v in n d dng


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- Khng nhit v ha cht

- n nh, thn thin vi mi trng c gi thnh cnhn tranh

hn na bao b phi ph hp vi quy nh v bao b thc phm, tng tc gia bao b v

thc phm, m bo an ton v sinh cht lng v an ton thc phm

2.4.u im ca mng chitosan:

D phn hu sinh hc

V tm ph liu l ngun nguyn liu t nhin rt di do, r tin, c sn quanh nm,

nn rt thun tin cho vic cung cp chitin v chitosan

Tn dng ph thi trong ch bin thy sn bo qun thc phm nc ta. Thnh

cng ny cn gp phn rt ln trong vic gii quyt tnh trng nhim mi trng do

cc cht thi t v tm gy ra.

2.4.1.u in ca chitosan trong bo qun tri cy:

- C kh nng to mng do, dai: nng thch hp chitosan c kh nng to mng kh

dai, kh x rch, c bn tng ng vi mt s cht do vn dng lm bao gi.

- C kh nng khng nm, khng khun cao

- Trnh mt m ca qu khi bo qun lnh

- Hn ch oxi cung cp, gim h hp hiu kh v trnh ym kh

- Lm chm li qu trnh b thm ca rau qu: Rau qu sau khi thu hoch s dn dn b

thm, lm gim cht lng v gi tr. Rau qu b thm l do qu trnh oxi ho to ra cc

sn phm polyme ha ca orthoquinon. Nh bao gi bng mng chitosan m c ch

c hot tnh oxy ha ca cc polyphenol, lm thnh phn ca anthocyamin, flavonoid

v s tng lng cc hp cht phenol t bin i, gi cho rau qu ti lu hn.

- C kh nng kt hp vi cc cht bo qun khc (axit benzoic)

- D phn hy sinh hc v thn thin vi mi trng

- C kh nng hp ph mu m khng hp ph mi, hp ph mt s kim loi nng

-Chitosan c kh nng to mng, gi m, khng khun, khng nm, trnh ym kh, gim

s h hp v h hng t nhin ca qu

-C kh nng kt hp vi cc ha cht bo qun khc.


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- C th s dng chitosan vi nng 1,5-2% bo qun gi ti mt s loi qu, tuy

nhin cn nghin cu kt hp vi cc ph gia v iu kin bao gi d hiu qu bo qun

c cao hn.

-Kt hp vi bo qun lnh tng thi gian bo qun v gi c tnh cht ca qu

-Chitosan c kh nng lm tng thi gian bo qun m khng nh hng nhiu ti cht

lng sn phm.

Phn hu sinh hc d hn chitin.

Chitosan v cc dn xut ca chng u c tnh khng khun, nh c ch hot ng ca

mt s loi vi khun nh E.Coli, dit c mt s loi nm hi du ty, c rt, u v c

tc dng tt trong bo qun cc loi rau qu c v cng bn ngoi

Khi dng mng chitosan, d dng iu chnh m, thong khng kh cho thc

phm (Nu dng bao gi bng PE th mc cung cp oxy b hn ch, nc s b ngng

ng to mi trng cho nm mc pht trin)

Mng chitosan cng kh dai, kh x rch, c bn tng ng vi mt s cht do

vn c dng lm bao gi.

Mng chitosan lm chm li qu trnh b thm ca rau qu. Rau qu sau khi thu hoch

s dn dn b thm, lm gim cht lng v gi tr. Rau qu b thm l do qu trnh lnmen to ra cc sn phm polyme ha ca oquinon. Nh bao gi bng mng chitosan m

c ch c hot tnh oxy ha ca cc polyphenol, lm thnh phn ca anthocyamin,

flavonoid v tng lng cc hp cht phenol t bin i, gi cho rau qu ti lu hn.


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Hnh15.Hnh Chui mau b mc khi bo qun bng cch thng thng (tri)

Chui ti lu nh s dng ch phm sinh hc chitosan bo qun(phi)

2.5.Cch to mng bc chitosan:Chitosan c nghin nh bng my gia tng b mt tip xc.Pha dung dch chitosan 3% trong dung dch axit axetic 1,5%.Sau b sung cht ph gia PEG - EG 10% (t l 1:1) vo v trn u, yn mt lc

loi bt kh.Sau em hn hp thu c qut u ln mt ng inox c nung nng nhit 64-65oC (ng inox c nng nhit bng hi nc). kh mng trong vng 35 pht ri tch mng.Lc ny ngi ta thu c mt v bng c mu vng ng, khng mi v, l lp mng

chitosan c nhng tnh nng mi u vit


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Mng Bao Chitosan Trong Bo Qun Rau Qu GVHD:Th.s Dng VnTrng

CHNG III: MT S NGHIN CU THC NGHIM KHC V

MNG BAO CHITOSAN TRONG VIC BO QUN.

3.1.Cc nghin cu t c: c rt nhiu nghin cu v vic ng dng chitosan bo qun tri cy, mt s

nghin cu thu c nhng thnh cng nht nh

Sau y l mt s nghin cu tiu biu:

3.1.1.Cc nghin cu trong nc:

Qui trnh nghin cu bo qun xoi c S Khoa hc v Cng ngh TP Cn Th

nghim thu u nm 2007. Nng trng Sng Hu ni nghin cu hin c

150.000 cy xoi ct Ha Lc, trung bnh, mi h c 80-100 cy. Vi sn lng

hng nm ln n c hng nghn tn xoi sn phm. Xoi Ct Ha Lc c v mng

nn kh bo qun lu v vn chuyn xa, gy kh khn cho vic xut khu. Tin s

Ton cng cc cng s nghin cu khc phc hn ch trn bng cch x l chn

nc nng ngn bnh thn th v rui c tri. Bin php ny gip m bo sn

phm t cht lng theo yu cu kim dch thc vt cho cy n tri. Sau , tri

c nhng vo dung dch Chitosan, to nn mt lp mng bao ph mng c tc

dng chng mt m, gim hao ht trng lng v ko di thi gian tn tr. Qua cc

th nghim, xoi c tn tr tt nht l nhit lnh t 10-12 0C. Kt lun: Qua

qu trnh x l v tn tr, tri xoi c bo qun tt nht trong 4 tun, thm ch c

kh nng ko di 6 tun, c th vn chuyn v phn phi i xa.

Qua nhiu nghin cu cc nh khoa hc a ra qui trnh bo qun tri qut

ng vi thi gian tn tr n 8 tun. l bo qun tri bng cch bao mng

Chitosan nng 0,25% kt hp vi bao Polyethylene (PE) c 5 l vi ng

knh mi l 1 mm v ghp m li bng my p. Sau , bo qun nhit 12 C.

Vi phng php ny, phm cht bn trong tri nh: hm lng ng, hm lng

vitamin C... lun n nh, t l hao ht trng lng thp, mu sc v tri ng u

v p.

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ti: Nghin cu s dng cc hot cht sinh hc bin thay th cc cht c

hi trong bo qun nng thy sn sau thu hoch v ch bin thc phm ca PGS.

TS Trn th Luyn Khoa Ch Bin, Trng i Hc Nha Trang a ra mt s

kt lun sau:Ln du tin cc dn liu khoa hc c a ra trn c s nghin cu mt cch chi

tit y v kh nng bo qun nng thy sn ca chitosan, COS

(chitosanolygosacharide) trn cc i tng c , cam, qut, c chua, hnh

tm v da qu, tht heo, tht b, c ngn, v xc xch

Qua nghin cu ca Chu Vn Minh v cng s thuc Vin Ho hc cc hp cht

t nhin, Trung tm Khoa hc T nhin v Cng ngh Quc gia iu ch c

ch phm BQ-1 vi nguyn liu chnh l chitosan c tc dng bo qun qu ti (c

chua, nho vi, chui,) rt tt. Ch phm ny c tc dng chng mc, chng s

ph hu ca mt s nm men, vi sinh vt gram m trn cc loi hoa qu.

Mi y nht, ti i hc Thy sn Nha Trang, cc kt qu nghin cu ca cc nh

khoa hc Trn Th Luyn, Nguyn Trng Bch cho thy chitosan c th kt hp vi

cc ph liu tinh bt h ha, sorbitol v PVA (polyvinyl acetate) to mng bao

c c tnh c l kh tt (mm do v bn t cao) c kh nng p ng yu cu

bao gi thc phm. ng thi khi s dng mng bao chitosan to thnh bao gi

tht b ti, kt qu cng cho thy mng bao chitosan lm gim ng k nng

vi sinh vt tng s trn b mt tht b khi bo qun nhit 0-5C [3].

Ti trng ai hoc Cng Nghip Thnh Ph H Ch Minh cng c th nghim v

bo qun trng g bng Chitosan.bng cch kho st mu sc ca qu trng sau thi

gian bo qun v s hao ht trng lng

V kt lun nh sau:trong 5 ngy u bo qun hao ht khi lng trng c

to mng (nng chitosan 1%; 1,5% v 2%) khng c s khc bit ln vi trng

khng to mng chitosan. Nng chitosan to mng cng khng nh hng ln

n hao ht khi lng trng trong khong thi gian ny. iu ny c th c

gii thch: do trong thi gian u, khi mng bao t nhin ca v trng cha b phn

hy nn cn kh nng khng vi sinh vt, hn ch s trao i kh v nc vi mi

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trng bo qun. Tuy nhin, khi thi gian bo qun cng di th nh hng ca

mng bao n hao ht khi lng trng cng r nt hn. Sau 30 ngy, trng c

bo qun bng mng chitosan nng 1,5% ch hao ht 5,312%, trong khi mu

i chng ln ti 10,911%.Qua qu trnh kho st vi cc nng chitosan 1%; 1,5% v 2% chitosan th nhm

ch ra c nng 1,5% chitosan l ti u nht bo qun cho cht lng qu

trng tt nht.[12]

3.1.2.Cc nghin cu nc ngoi:

Nhm nghin cu B. Ratanachinakorn, W. KumsiriBuchsapawanich, J. Singto

xy dng ch bo qun tri cy bng chitosan, theo nghin cu nng chitosan

ph hp l 1-2%

- Nhm tc gi: Nurrachman, Purwoko, B. S., Susanto, S., Sutrisno thuc

Department of Agronomy, Bogor Agricultural University, Darmaga, Bogor 16680,

Indonesia nghin cu ng dng chitosan trong bo qun to v a ra kt lun:

s dng chitosan vi nng 0.5, 1.0 v 1.5% v bo qun nhit phng

lm gim 1,5% s hao ht khi lng so vi mu khng dng chitosan

- Nhm nghin cu: Yoshii Fumiko, Kume Tamikazu, Nht Bn nghin cu bo

qun xoi bng chitosan v ch ra rng: sau 15 ngy bo qun nhit thng

xoi vn gi c mu sc t nhin, ti v mt i 10% khi lng

- Cc tc gi S. Bautista-Baos. M. Hernndez-Lpez, E. Bosquez-Molina C. L.

Wilson t Mexico nghin cu tc dng khng nm ca chitosan: nng

1.5%-3% chitosan c kh nng khng nm C. gloeosporioides c trn to m khng

nh hng ti nng cht rn tng s v s hao ht khi lng qu trong sut qu

trnh bo qun

- Svetlana Zivanovic, John R. Mount, Frances A. Draughon, Carl E. Sams n t

khoa cng ngh thc phm trng i hc Tennessee nghin cu ng dng chitosan

v chitosan c b xung tinh du lm mng bao bo qun du ty v nho: cc tc gi

dng chitosan 1% ,chitosan 1% kt hp vi 4% tinh du lm mng bao qu v

bo qun nhit 4C, nh gi s pht trin ca nm mc bng phng php

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nui cy trn canh tng thch Rose Bengal agar trong 3 ngy. Nghin cu a

ra mt s kt lun sau: sau 9 ngy bo qun s t bo nm mc m c ln lt

l: 4.40, 2.90,v 0 cfu/mL ng vi cc mu khng dng chitosan, c dng chitosan

v chitosan kt hp vi tinh du. s pht trin ca nm mc trn du ty sau 18ngy bo qun l 3.87 cfu/mL gim i nhiu so vi 4,33 cfu/mL khi khng dng

chitosan.

Khi phn tch hm lng kh etylen thot ra trong qu trnh bo qun thu c cc

kt qu sau: Lng kh ethylen gim t 0.187 L/kg.h xung 0.028 and 0.012

L/kg.h khi bo qun bng chitosan v chitosan c kt hp tinh du.

Nh vy chitosan c kh nng lm gim v c ch s pht trin ca nm mc, ngoi

ra cc qu trnh sinh l ca qu cng gim xung lm qu bo qun c lu hn,

chitosan c kh nng dng kt hp vi cc ha cht bo qun khc tng hiu qu

bo qun

- Nm 1996 cc tc gi Lee SH, No HK, Jeong YH cng b kt qu bc u

nghin cu s dng dung dch chitosan trong bo qun trng..

Ngoi ra cn c rt nhiu nghin cu khc thc hin trn cc loi hoa qu khc

nhau, i chng cc nhit khc nhau u a ra nhng iu kin bo qun

ti u khi s dng chitosan.

3.2.thc nghim cho bo qun:

- vi qu bi, khi dng mng bao chitosan th qu bi c th bo qun trong 3

thng, v khng c thay i nhiu nh hng n cht lng bi.Thc nghim ny

c mt nhm sinh vin ca trng i Hc Nng Lm nghin cu v chng

minh [12]

- Vi xoi, cc tc gi khuyn co nn x l tri sau khi ra sch qua nc nng

48-500C trong 5-10 pht ngn nga bnh thn th v rui c tri, sau nhng

vo dung dch Chitosan v bo qun nhit lnh 10-120C th s lu gi c

qu trong 4 tun, thm ch ti 6 tun c th vn chuyn i xa an ton.

HTP06ALT

th 3.1:Biu din s hao ht khi lng trng theo thig

GVHD ThS Nguyn Th T

Nhm SVTHTrn Thanh

Phm Vn QV Trng T

31


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- Vi cam qut, c bit l tri qut ng Lai Vung ( ng Thp) cc tc gi

khuyn co quy trnh bo qun tri bng cch bao mng Chitosan nng 0,25%

kt hp vi bao Polyethylene (PE) c c 5 l vi ng knh 1 mm c ghp m

bng my p v bo qun nhit lnh 120C c th bo qun c ti 8 tun.3.3.Cc kt lun c th:

* Vi nng chitosan hp l t 1,5 2 % khng nh hng n cht lng cm

qun ca qu sau thu hoch, ng thi li c tc dng lm cho trng lng ca qu

t b hao ht. T cho thy, c th s dng chitosan hoc chitosan kt hp thm

ph liu bo qun gi tui cc loi qu cho hiu qu kh r rng

* Cam ti t chn k thut em nhng trong dung dch chitosan 1,5 %, hong

kh v bo qun c 25 ngy nhit thng, 36 ngy nhit lnh 8-10 0C,

vn t c ti theo tiu chun nguyn liu ch bin.

* Qut ti em nhng trong dung dch chitosan 1,5 %, hong kh v bo qun oc

15 ngy nhit thng, 32 ngy nhit lnh 8-10 0C, vn t c ti

theo tiu chun nguyn liu ch bin.

* Hnh tm c nhng trong dung dch chitosan 1,5 %, hong kh v bo qun

c 56 ngy nhit thng, vn t c tiu chun nguyn liu ch bin.

* Chitosan c tc dng lm gim ng k s lng vi sinh vt tng s trn b mt

thc phm. Vi hm lng 1,5 % gim s lng vi sinh vt trn b mt cam l

93 %, trn b mt qut l 96 %, v.v.

* Da qu chn k thut em nhng trong dung dch chitosan 1,5 % c ph liu

benzoat natri 0,1 %, hong kh v bo qun c 15 ngy nhit thng v 35

ngy nhit lnh 8-10 0C, vn t c ti theo tiu chun nguyn liu ch

bin. Trng hp x l bng olygoglucosamin 1% vi ph liu benzoat natri 0,1 %

th gi ti c 12 nhit thng v 40 ngy nhit 8-10 0C .

Ti liu tham kho

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[1] http://www.chitosan.com.cn/chitosan/news

[2]Production of chitosan oligosaccharide. (Sn xut chitosan oligosaccharide vng dng ca n trong thc phm, dc phm, m phm).

[3] PGS-TS Trn Th Luyn; GVC Minh Phng; TS Nguyn Anh Tun. Sn

xut cc ch phm k thut v y dc t ph liu thy sn, NXB Nng Nghip

[4] Lu Vn Chnh. Tng hp v nghin cu hot tnh sinh hc ca mt s dn

xut t chitin. Lun n tin s

[5]ng Vn Luyn, ng Mai Hng. Phng php sn xut chitosan, 1992. (

cp cng ngh sn xut biopolyme, c th l cp n phng php thu nhn

chitin t v tm ri chuyn ha tip thnh chitosan).

[6]Alvarez, Review: Active food packating. Food Sci. Tech Page 97-108

[7]Chu Vn Minh: s dng chitosan lm cht bo qun qu ti Tp ch khoa

hc, trang 34, s 4-1996

[8] http://edu.go.vn/e-tap-chi/tin/9/90/6446/chitosan-tong-quan,-nghien-cuu,-ung-

dung.html

[9]Joint FAO/WHO Food standards Progaramme Codex Alimentarius Commission

(1994)

[10]http://olympiavn.org/forum/index.php?topic=2589.0

[11]http://www.youtube.com/watch?v=Ia4gwKYAdh4

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http://www.chitosan.com.cn/chitosan/newshttp://edu.go.vn/e-tap-chi/tin/9/90/6446/chitosan-tong-quan,-nghien-cuu,-ung-dung.htmlhttp://edu.go.vn/e-tap-chi/tin/9/90/6446/chitosan-tong-quan,-nghien-cuu,-ung-dung.htmlhttp://olympiavn.org/forum/index.php?topic=2589.0http://www.youtube.com/watch?v=Ia4gwKYAdh4http://www.chitosan.com.cn/chitosan/newshttp://edu.go.vn/e-tap-chi/tin/9/90/6446/chitosan-tong-quan,-nghien-cuu,-ung-dung.htmlhttp://edu.go.vn/e-tap-chi/tin/9/90/6446/chitosan-tong-quan,-nghien-cuu,-ung-dung.htmlhttp://olympiavn.org/forum/index.php?topic=2589.0http://www.youtube.com/watch?v=Ia4gwKYAdh4


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[12]http://www.cyberchemvn.com/cyberchemvn/index.php?

option=com_content&view=article&id=107:chitosan-tng-quan-nghien-cu-ng-

dng&catid=36:cong-nghe-va-ung-dung&Itemid=37

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http://www.cyberchemvn.com/cyberchemvn/index.php?option=com_content&view=article&id=107:chitosan-tng-quan-nghien-cu-ng-dng&catid=36:cong-nghe-va-ung-dung&Itemid=37http://www.cyberchemvn.com/cyberchemvn/index.php?option=com_content&view=article&id=107:chitosan-tng-quan-nghien-cu-ng-dng&catid=36:cong-nghe-va-ung-dung&Itemid=37http://www.cyberchemvn.com/cyberchemvn/index.php?option=com_content&view=article&id=107:chitosan-tng-quan-nghien-cu-ng-dng&catid=36:cong-nghe-va-ung-dung&Itemid=37http://www.cyberchemvn.com/cyberchemvn/index.php?option=com_content&view=article&id=107:chitosan-tng-quan-nghien-cu-ng-dng&catid=36:cong-nghe-va-ung-dung&Itemid=37http://www.cyberchemvn.com/cyberchemvn/index.php?option=com_content&view=article&id=107:chitosan-tng-quan-nghien-cu-ng-dng&catid=36:cong-nghe-va-ung-dung&Itemid=37http://www.cyberchemvn.com/cyberchemvn/index.php?option=com_content&view=article&id=107:chitosan-tng-quan-nghien-cu-ng-dng&catid=36:cong-nghe-va-ung-dung&Itemid=37


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nhung van de moi chtosan

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