Đề tài sản xuất chitin-chitosan từ vỏ tôm và Ứng dụng chitosan làm màng bao...

SVTH: BI THANH TRUNG

TRANG 1

CHNG I: M U

1.1. t vn :

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.

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 dn u thu hoch v bn tri cy theo tp qun, khng c qui trnh bo

qun sau thu hoch. iu ny gy nh hng khng nh n cht lng sn phm

v hiu qu kinh t. 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. Thi gian gn y vn ny

c cc nh vn rt quan tm v cc cng trnh nghin cu bo qun tri cy sau

thu hoch cng ang cho nhng kt qu kh quan.

Rau qu chng ta c sn lng rt cao nhng v mt cht lng th rt km

nh thng c thu hoch khi cha n thi im thu hoch, a s tri cy thng

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.

S h hng trong qu trnh bo qun rau qu do cc nguyn nhn sau y: do

hin tng chn sinh l t nhin v hin tng nhim bnh. ng thi cc yu t

nh vi sinh vt thm nhp t mi trng bn ngoi v cng h hp ca qu nu

h hp cng mnh m th qu trnh chn cng chng xy ra v thi hn bo qu cng

b rt ngn. Rau qu trong qu trnh bo qun b mt nc v b tn thng c hc.

Bnh cng gy tn thng to iu kin cho nhim vi sinh vt th cp cng gy h


TRANG 2

hng nhanh chng hn. Thuc bo v thc vt s dng ba bi dn n gim gi tr

cm quan v khng an ton.

V vy tm c phng php bo qun rau qu sau thu hoch n gin v

tit kim l nhim v trc mt quan trng y mnh xut khu rau qu.

C chua l loi rau mu c trng v s dng kh ph bin nc ta.

Chng c tui th ngn do cu trc nhiu nc v khng c v cng bo v. Thi

v thu hi c chua ko di t thng 11 n thng 2 nm sau. Trong thi gian ny do

thu hoch cng lc nn gi c chua rt thp (c thi im ch 500 VND mt

kilogam), i khi ngi nng dn khng mun thu hi v gi bn khng b cng

sc. Nhng khi tri v gi c chua li kh cao, cc nh my khng c c chua

sn sut. T trc ti nay bin php bo qun c chua ch yu l sn xut bn sn

phm (nuc p, bt, c chua c c) d cng ngh c nhiu ci tin song cc

tnh cht qu ca c chua trong cc sn phm ny u b mt i, c bit l mi v

v vitamin.

Trong nhng hng nghin cu cng ngh bo qun sau thu hoch tri cy,

rau qu ni chung v c chua ni ring th vic ko di c thi gian bo qun v

quan trng nht l gi c trng thi, tnh cht nh ca rau qu ti c quan

tm hn c.

Chitosan l mt polyme c sn xut t u tm, v tm, mai mc l

nhng ph ph phm ca ngnh ch bin thy sn. Chitosan th hin nhiu c tnh

ng ch nh c kh nng to mng thm kh, kh nng dit khun cao v khng

hi cho ngi tiu dng khi s dng gi rau qu ti, khi s dng c bit ph hp

cho bo qun rau qu ti. Do ngi ta nghin cu s dng chitosan lm mng

bao trong bo qun rau qu v n va thn thin vi mi trng va an ton thc

phm.

1.2. Mc ch kha lun:

Tm hiu phng php bo qun c chua bng mng bao chitosan.

1.3. Mc tiu:


TRANG 3

Quy trnh sn xut chitin chitosan t v tm. Trong qa trnh thy phn

v tm c thc hin bng enzyme protease.

Tng quan v ng dng ca chitosan trong bo qun c chua.

Xy dng quy trnh bo qun c chua bng chitosan n gin v tit kim.


TRANG 4

CHNG II: TNG QUAN

2.1 TNG QUAN V CHITOSAN

2.1.1 Lch s pht hin

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[21].

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[21].

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 lng chitosan s t ti 118000 tn/nm: trong

Nht, M l nc sn xut chnh[14].

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 quy

trnh sn xut chitosan ca tc gi Minh Phng m u bc ngoc quan

trng trong vic nghin cu, tuy nhin cha c ng dng no thc t trong sn

xut[7].


TRANG 5

2.1.2. Ngun chitosan

Chitosan l sn phm t v tm cua, mai mc ph ph phm ch bin thy

sn trc kia n l cht thi rn gy nhim mi trng. Pht hin t ph ph phm

ny c th sn xut chitin v chitosan l nhng polysaccharide t nhin c nhiu

c tnh qu gm khng khun, to mng bao bo qun tri cy rau quT cc

cng trnh nghin cu ca nhiu nh khoa hc trn ton th gii chng minh

trong v tm c cha 27% cht chitin, t chitin ny h c th chit tch thnh cht

chitosan.

Nc ta c b bin di sn lng khai thc thy sn l 2.45 triu tn, sn

lng nui trng thy hi sn l 2.57 triu tn c tnh hng nm Vit Nam. Tm

l mt hng ch bin ch lc ca nghnh thy sn Vit Nam ch yu l tm ng

lnh. Theo bo co ca b thy sn d bo sn lng tm nm 2011 l 403600 tn

ty thuc vo sn phm ch bin v sn phm cui cng, ph liu tm c th ln ti

40 70% khi lng nguyn liu. Tng ng vi sn lng hng nm s c khi

lng ph liu khng l gm u v v tm c to ra.Vit Nam lng ph thi v

tm t cc nh my tm ng lnh khong 30.000 tn (theo Nguyn Ngc T-Bo

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

Ngy nay, ngh nui tm v ch bin tm 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.

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

lnh. Chnh v vy, v tm 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[3].


TRANG 6

Chitin c xem l polymer t nhin quan trng th hai ca th gii, c

nhiu th hai th gii (ch sau xenlulo). L mt polymer ng vt c tch chit v

bin tnh t v cc loi gip xc (tm, cua, hn, trai, s, mai mc, a bin), mng

t bo nm h Zygemycetes, cc sinh khi nm mc, mt s loi to

Chitosan thng mi c ngun gc t v tm v ng vt gip xc bin khc.

Chitosan c sn xut bng kh acetyl (deacetylation) ca chitin, l yu t c

cu trong cc b xng ngoi ca ca ng vt gip xc (cua, tm, mai mc) v

thnh t bo ca nm. Mc deacetylation (%DD) c th c xc nh bng ph

NMR, v DD% trong chitosan thng mi l khong 6- 10%.

2.1.3. Cng thc cu to

2.1.3.1. Cu trc ha hc ca chitin

Chitin l polysaccarit 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 poly (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 2.1: 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.


TRANG 7

-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 ca mc ng[5].

Hnh 2.2: Sp xp cc mch trong phn t chitin

2.1.3.2. 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 2.3: 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

t chitosan (khong 10%). V vy cng thc chnh xc ca chitosan c th hin

nh sau:

chitin chitin chitin


TRANG 8

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 2.4: Dn xut N,O- Cacboxymetylchitin

Dn xut N,O-cacbonxymetylchitosan:

Hnh 2.5: Dn xut N, O-cacbonxymetylchitosan

Dn xut: N,O-axylchitosan:


TRANG 9

Hnh 2.6: Dn xut: N, O-axylchitosan

Dn xut N-metylchitosan:

Hnh 2.7: Dn xut N-metylchitosan

So snh cu trc chitin, chitosan, xenluloza:

Hnh 2.8: Cu trc chitin, chitosan, xenluloza

1: Chitin, 2: Chitosan, 3: Xenluloza.

2.1.4. deaxetyl ha- DD (Degree of deaxetylation)

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


TRANG 10

Hnh 2.9: Qu trnh deaxetyl ho

Nu:

DD < 50%_ chitin

DD 50%_ chitosan

Cc phng php xc nh:

Da vo ph cng 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

2.1.5. Tnh cht chung.

- 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: Pb3+, Hg+

- Nhit nng chy 309- 311oC.


TRANG 11

- 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 [3].

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

(pH< 6.5), c kh nng bm dnh trn b mt c in tch m nh protein,

aminopolysaccharide (alginate), acid bo v phospholipid nh s c mt ca nhm

amino (NH2)

- Chitosan thng mi t nht phi c mc DD (degree of deacetylation) hn 70%

- Chitosan c tnh cht c hc tt, khng c, d to mng, c th t phn hu sinh

hc, c tnh ho hp sinh hc cao vi c th.

2.1.6. 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 acid m c nhng tan trong acid long

(pH6), to dung dch keo trong, c kh nng to mng tt.

Chitosan c mu trng hay vng nht, khng mi v. Khng tan trong nc,

dung dch kim v axit m c nhng tan trong acid long (pH6), to dung dch

keo trong, c kh nng to mng tt, nhit nng chy 309 311 0C.

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.


TRANG 12

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 ln men 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.

2.1.7. Tnh cht ho hc ca chitin/chitosan

Trong phn t chitin/chitosan c cha cc nhm chc -OH, -NHCOCH3

trong cc mt xch N-axetyl-D-glucozamin v nhm OH, nhm -NH2 trong cc

mt xch D-glucozamin c ngha chng va l ancol va l amin, va l amit. Phn

ng ho hc c th xy ra v tr nhm chc to ra dn xut th O-, dn xut th N-,

hoc dn xut th O-, N.

Mt khc chitin/chitosan l nhng polime m cc monome c ni vi nhau

bi cc lin kt -(1-4)-glicozit; cc lin kt ny rt d b ct t bi cc cht ho

hc nh: acid, baz, tc nhn oxy-ha v cc enzyme thu phn.

2.1.7.1. Cc phn ng ca nhm OH

- Dn xut sunfat.

- Dn xut O-axyl cu chitin/chitosan.

- Dn xut Otosyl ho chitin/chitosan.

2.1.7.2. 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

2.1.7.3. Phn ng xy ra ti v tr O, N

- Dn xut O, Ncacboxymetylchitosan.


TRANG 13

- 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.

2.1.7.4. Kh nng hp ph to phc vi cc ion kim loi chuyn tip ca chitin/

chitosan

- Trong phn t chitin/chitosan v mt s dn xut ca chitin c cha cc nhm

chc m 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 polyme 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.

trong l mng polime

Hnh 2.10: Phc ca chitosan vi kim loi

2.1.7.5 Phn ng c trng khc ca chitosan


TRANG 14

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

nu trong mi trng axit sunfuric c mu tm.

Phn ng Alternative: tc dng vi acid 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 acid, enzyme, 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.

2.1.8. 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.

- 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 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


TRANG 15

lm cho 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 v 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 ion quan trng [16].

+ 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%

- 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.

- Chitosan l cht thn m c kh nng hp th 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 th 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.


TRANG 16

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

insulin tuyn ty 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.

- Chitosan chng tia t ngoi, chng nga.

2.1.9.c tnh

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 [7].

- 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.

- 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.

2.1.10. Sn xut chitosan

2.1.10.1 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....)

[1]


TRANG 17

Bng 2.1: Hm lng chitin trong v mt s ng vt gip xc

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

2.1.10.2. Quy trnh cng ngh sn xut chitosan bng phng php ha hc

STT Phn loi Hm lng chitin theo trng lng (%)

1 u tm 11

2 V tm 27

3 V tm ph thi hn hp 12-18

4 V tm hm 37

5 Cng cua tuyt 24

6 Chn cua tuyt 32

7 Mai mc ng 30-35

8 a bin 34-49


TRANG 18

Quy trnh cng ngh sn xut chitosan bng phng php ha hc

Ra v sy

Nghin v lc

Loi Protein Dung dch NaOH 3%,

nhit 90-95 0C trong

3-4h

Ra

Kh khong HCL 1N trong 30 pht

nhit phng

Ra xong ri kh

mu

Ra v sy

Deacetyl ha NaOH 50% trong

4 gi, 110-1200C

Ra sy

Nguyn liu

Chitin

Chitosan


TRANG 19

Hin nay sn xut chitin chitosan ch yu bng phng php ha hc

bao gm cc qu trnh chnh sau:

Qa trnh loi protein

Ta tin hnh loi b hon ton protein bng dung dch NaOH 3%, protein b

kim thy phn thnh cc amin t do tan v c loi ra theo quy trnh ra tri.

Lng NaOH 3% cho vo n khi ngp ton b v tm v kim tra pH = 11 12 l

c m bo vic loi b protein c hon ton. un nhit 90 - 950C

trong 3.5 4h (trong qu trnh nung lu vn tro dung mi do to bt nhiu v

mi bay ra kh chu ) sn phm sau khi nung c ra sch bng nc thng hoc

nc ct n Ph = 7.

Tip chng ti tin hnh ra trung tnh, nhm mc ch ra tri ht cc ,

mui natri, cc amin t do v NaOH d. Sy kh 600C thu c chitin th.

Qa trnh kh khong

Trong v tm thnh phn ch yu l mui CaCO3, MgCO3 v rt t

Ca3(PO4)2, nn ngi ta thng dng cc loi acid nh HCL, H2SO4... kh

khong. Khi kh khong, nu dng H2SO4 s to mui kh tan nn t s dng, ngi

ta dng HCL kh khong theo cc ph ng sau:

MgCO3 + 2HCl = MgCl2 + CO2 + H2O.

CaCO3 + 2HCl = CaCl2 + CO2 + H2O

Ca3(PO4)2 + 6HCl = 3CaCl2 + 2H3PO4

Trong qu trnh ra th mui Cl- to thnh c ra tri, nng acid HCL

c nh hng ln n cht lng ca chitosan thnh phm, ng thi c nh hng

ln n thi gian v hiu qu kh khong. Nu nng HCL cao s rt ngn c

thi gian kh khong nhng s lm ct mch do c hin tng thy phn cc lin

kt - (1-4) glucozit to thnh to ra cc polymer c trng lng phn t trung

bnh thp, c khi thy phn trit n glucosamin. Ngc li nu nng HCL


TRANG 20

qu thp th qu trnh kh khong s khng trit v thi gian x l ko di nh

hng n cht lng sn phm.

Sau khi kh khong tin hnh ra trung tnh, cng on ny c tc dng ra

tri ht cc mui, acid d tan trong nc. Qa trnh ra kt thc khi dch ra cho

PH = 7.

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 trit nn chitin thu c c

tinh khit khng cao.

Qa trnh ty mu ( loi b astaxanthin )

Chitin th c mu hng nht do c sc t astaxanthin. Do chitin n nh vi

cc cht oxy ha nh thuc tm (KMnO4) oxy gi (H2O2) nc javen (NaOCl +

NaCl), Na2S2O3, CH3COCH3li dng tnh cht ny ta s dng kh mu chitin.

iu ch chitosan

Qa trnh iu ch chitin thnh chitosan thc cht l qu trnh deaety ha

chitin, chuyn ha nhm NHCOCH3 thnh nhm NH2 v loi b nhm CH3CO,

chuyn ha thnh mui natri CH3COONa. thc hin c qu trnh deacetyl ha

hon ton, ngi ta s dng NaOH m c 50% thi gian 4h nhit 110 120

0C.

dy da vo tnh cht chitosan tan c trong dung dch acid long to

thnh dung dch keo trong sut, trong khi chitin khng tan do ta c th s b

kim tra mc chuyn ha chitin thnh chitosan bng cch ly mt t sn phm

cho vo CH3COOH 1%. Nu sn phm tan to thnh dung dch keo trong sut l

c. Sau ra trung tnh v sy kh, chitosan thu c c mu trng sng. Qa

trnh iu ch chitosan t chitin cho hiu sut tng i cao ( 60 75%).

2.1.10.3. Quy trnh cng ngh sn xut chitosan s dng enzyme prtease


TRANG 21

Quy trnh cng ngh sn xut chitosan s dng enzyme protease

Ra v sy

Nghin v lc

Ra

Kh khong HCL 1N trong 30 pht

nhit phng

Ra xong ri kh

mu

Ra v sy

Deacetyl ha NaOH 50% trong

4 gi, 110-1200C

Ra sy

Nguyn liu

Chitin

Thy phn protein (dng enzyme protease 13% t l w/v = 1/5, pH =5- 5.5 nhit 70 -800C trong thi gian 4 gi

Chitosan


TRANG 22

Gii thch quy trnh

Vic sn xut chitosan theo phng php sinh hc kt hp ha hc cng thc

hin theo cc bc: kh protein, kh khong v deacetyl. Chng ta thy cng on

kh khong hiu qu nht v duy nht ch thc hin bng phng php ha hc.

Cng on kh Protein y chng ta dng phng php sinh hc, l

kh protein bng enzyme protease vi nng 13% t l w/v = 1/5 vi nng pH

thch hp t 5- 5.5 nhit 70 -800C trong thi gian 4 gi. Trong phng php

ny ngi ta c th dng cc ch phm enzyme protease 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 d phn hy

nhng lng protein tch ra khng trit .

Qa trnh kh khong c thc hin tng t nh quy trnh cng ngh sn

xut chitosan bng phng php ha hc.

Phng php c hc c thc hin tng t nh quy trnh cng ngh sn

xut chitosan bng phng php ha hc.

Qa trnh ty mu c thc hin tng t nh quy trnh cng ngh sn xut

chitosan bng phng php ha hc.

Qa trnh deacetyl ha c thc hin tng t nh quy trnh cng ngh sn

xut chitosan bng phng php ha hc. Ngoi ra qu trnh deacetyl bng enzyme

deacetylase nhng hiu qu khng bng phng php ha hc.

Quy trnh phn tch nguyn liu :

Xc nh m ca v tm kh chi tit theo mc A trong ph lc.

Xc nh hm lng tro trong v tm kh tuyt i chi tit theo mc B trong

ph lc.

Xc nh hm lng Ca v P trong mu tm kh tuyt i chi tit theo mc

C trong ph lc.


TRANG 23

Xc nh hm lng Nito tng s bng phng php Kjeldahl chi tit theo

mc E trong ph lc.

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 thy 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.

2.1.11. ng dng ca chitosan

2.1.11.1. 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 [14].


TRANG 24

Chitosan chnh thc c T chc y t th gii (WHO) cho php dng

trong y hc v thc phm [15].

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.

Tm li, ch phm Chitosan c dng trong thc phm

Dng bo qun thc phm, hoa qu, rau ti...

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.

2.1.11.2 ng dng trong y hc

- Chitosan c ng dng trong iu tr bng.

- Khng ch s gia tng ca t bo ung th.

- Chng vim cp trn m lnh.

- Ngn chn s pht trin ca chng nhi mu c tim v bnh t qu

- H cholesterol, thuc cha bnh d dy, chng ng t mu, tng sc khng,

cha xng khp, h tr cha bnh tiu ng

- Dc phm.

2.1.11.3.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(II)... Do vy chitin v mt s dn


TRANG 25

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

2.2. NG DNG CHITOSAN BO QUN RAU QU

2.2.1. Thc trng vn bo qun tri cy Vit Nam

Vn trong nc:

Nc ta hin nay 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 dn u thu hoch v bn tri cy theo tp qun, khng c qui trnh bo

qun sau thu hoch. 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 dn n 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 cy thng khng qua khu kim tra cht lng


TRANG 26

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.

2.2.2. C s khoa hc ng dng chitosan trong bo qun tri cy

2.2.2.1.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 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 mc 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:


TRANG 27

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 ng c th tng ln do

tinh bt chuyn ha thnh.

Tinh bt: C th tng hoc gim 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 nu cha 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 acid hu c: Hm lng acid hu c gim dn lm chua ca rau qu

gim.

Cc vitamin: Gim i rt nhanh do tc ng ca enzyme 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 enzyme.

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

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.


TRANG 28

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 CO2 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 qu trnh l CO2, H2O v nhit. Tiu biu l phn ng:

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

Khi oxi trong mi trng gim xung khong 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

CO2, 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 cch 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.

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, nhoKh etylen to ra

trong sut qu trnh h hp l nguyn nhn quan trng thc y qu trnh chn ca


TRANG 29

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 trnh 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.

2.2.2.2 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 hot ng ca enzyme

Do s t bin i cc cht

Do tc ng c hc

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

2.2.2.3. Bo qun rau qu

Nguyn l bo qun rau qu:

Khi lu tr rau qu ti sau khi thu hi trong iu kin kh quyn bnh

thng, cht lng ca chng s gim dn v tin ti h hng hon ton do thi ra.

thi gian t khi thu hi cho ti khi rau qu hng hon ton di hay ngn ph thuc

vo nhiu yu t khc nhau nh: ging, loi rau qu, thi gian thu hi, chn v

iu kin mi trng bo qun Nguyn nhn trc tip v c bn dn ti rau qu

b h hng l do hin tng chn v hin tng nhim bnh.


TRANG 30

Qu trnh chn ca rau qu ph thuc vo cng h hp, h hp cng

mnh m th qu trnh chn cng nhanh chng xy ra v thi hn bo qun ca rau

qu cng b rt ngn.

Qu cng chn th cng tr nn mm v gim kh nng chu tc ng c hc.

Qu trnh tin ti giai on chn ca rau qu l qu trnh phn hy cc cht dinh

dng trong c c cc cht c kh nng c ch vi sinh vt nh cc acid,

phitonxit.to iu kin tt cho vi sinh vt pht trin mnh gy thi ra v h hng

nhanh chng.

Nh vy, ko di thi hn bo qun ca rau qu trc ht l km hm hot

ng sng, tc l c ch cng h hp, t km hm tc chn ca qu.

Nhng ch c km hm ch khng c nh ch nu khng s dn ti h hng

nhanh chng hn do h hp ym kh.

Trong trng hp h hp c hn ch ti mc thp nht nhng khi vi sinh

vt nht l nm mc c iu kn pht trin mnh th rau qu cng s b h hng

nhanh chng. V vy nguyn tc tip theo l ngn nga, loi b hot ng ca vi

sinh vt [8].

Da trn nhng nguyn l sinh hc, gio s Nikitin chia cc phng php

bo qun thnh 3 nhm:

Nhm th nht bao gm cc phng php da trn nguyn l bo ton s

sng- Bioza: rau qu c gi nguyn trng thi sng bnh thng khng cn tc

ng bt c gii php x l no ngoi mt vi tc ng hn ch cng sng

nhm gim mc phn hy thnh phn dinh dng do h hp v gim tn hao khi

lng t nhin do bay hi.

Nhm th hai: gm cc phng php da trn nguyn l tim sinh-Anabioza.

Lm chm, c ch hot ng sng ca qu v ca vi sinh vt nn lm chm thi

gian h hng v thi ra ca rau qu. Trong nhm ny gm cc phng php: bo

qun lnh, lnh ng, c c, sy iu chnh thnh phn kh quyn, mui chua, dm

gim.c im chung ca cc phng php ny l to ra mi trng khng thun

li cho hot ng sng ca qu v ca vi sinh vt.


TRANG 31

Nhm th ba l nhm da trn nguyn l phi tim sinh-Abioza. l cc

phng php loi b s sng ca qu cng nh ca vi sinh vt. Khi khng cn hot

ng sng th qu cng mt tnh khng bnh t nhin chnh v th chng tr thnh

mi trng thun li cho s pht trin ca vi sinh vt, mun gi sn phm khi h

hng th phi tiu dit hay c ch hon ton vi sinh vt c trong sn phm. Cc

phng php thuc nhm ny c: thanh trng, tit trng, cc phng php bo qun

bng ha cht hay bng khng sinh, phng php lc vi sinh, chiu x

Nhng yu t nh hng ti thi hn bo qun rau- qu:

Thi gian bo qun rau qu ti ph thc vo rt nhiu yu t khc nhau trong

ng k nht l nhit , m v thnh phn kh quyn.

- Nhit l yu t rt quan trng c yu t quyt nh ti thi hn bo qun ca

rau qu, s thay i nhit trc ht nh hng ti cng h hp. Nhit

cng cao tc phn ng sinh ha xy ra trong rau qu cng nhanh, tuy nhin s

ph thuc t l thun ch n gii hn nht nh, c th khi tng nhit t 25 oC

tr ln th cng h hp li gim. Chng ta mun c ch hot ng sng ca rau

qu th bo qun nhit cng thp cng tt, tuy nhin nhit qu thp khng

hn ko di c thi gian bo qun ca rau qu v t bo thc vt b ph hy do

dch bo b ng bng mt khc nhit thp lm ri lon mt s qu trnh sinh l,

sinh ha ca qu, v d nh chui xanh bo qun di 12oC chui s khng chn,

chui chn di 11oC th s b thm.

Nh vy, mi loi rau qu thch hp vi mt nhit nht nh no v nhit

bo qun ti u.

- m tng i ca khng kh quyt nh ti tc bay hi nc ca rau qu.

m cng thp th cng h hp v tc bay hi nc cng cao lm gim

khi lng v lm qu b ho. Nhng m thp lm gim kh nng hot ng ca

vi sinh vt nn hn ch bnh cho qu. Ngc li nu m cao lm gim qu trnh

bay hi nc v h hp, tuy nhin nu m qu cao s to iu kin thun li cho

vi sinh vt pht trin ngoi ra cn lm ngng t nc trn b mt rau qu dn n


TRANG 32

ri lon h hp. V th cn chn m thch hp cho tng loi qu khi bo qun -

m ti u.

-Thnh phn kh quyn l thnh phn kh O2 v CO2. Hai thnh phn ny phi

thch hp vi tng loi qu gim ti a h hp hiu kh nhng phi trnh iu

kin xy ra h hp ym kh, t hn ch ti a qu trnh sng cng nh khng

sinh ra nhng cht c hi sinh ra do h hp ym kh u c qu.

Cc phng php bo qun rau qu [8]:

Bo qun iu kin thng.

Bo qun lnh v lnh ng.

Bo qun trong mi trng thay i thnh phn kh quyn v mt s phng

php x l.

Bo qun CA (Controled Atmosphere) thay i thnh phn khng kh.

Bo qun trong mi trng kh quyn ci bin (MA_ Modified atmosphere)

qu c ng trong ti hay to mng bao polyme.

Bo qun bng ha cht.

Bo qun bng tia bc x.

2.2.2.4. 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


TRANG 33

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.

2.2.3. 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:

2.2.3.1. 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 12C.


TRANG 34

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.

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 [5].


TRANG 35

CHNG III: TNG QUAN CHITOSAN TRONG BO QUN C CHUA.

3.1. La chn ging c chua cho bo qun

Qua kho st v cc ging c chua hin nay c trn th trng cc tnh pha

Bc Vit Nam, tc gi la chn ging c chua hng i Loan P375 do X

Nghip Rau Qu - Vin Nng Nghip Cng Ngh Cao cung cp v ging ny c

nhng c im sau:

ang c trng v s dng ph bin nht trn th trng.

Cho cht lng qu tt v n nh.

Qu u rt thch hp cho bo qun cng nh cho qu trnh c gii, t ng ha

nu bo qun quy m ln.

Kch thc qu ph hp cho vic to mng bao chitosan. Mi qu c ng

knh t 4-5cm.

B mt qu nhn bng v u p rt thch hp cho vic n ti.

Qu chn u.

3.2. Xc nh chn thch hp cho bo qun

Tu c trng ging v iu kin thi tit, qu c chua chn tui 30-35

ngy. Trong qu trnh chn c chua phi qua cc thi k sau y:

- Thi k qu xanh: Qu v ht pht trin cha hon chnh. Mu qu xanh hon ton.

Nu thu hi qu thi k ny v thng qua cc phng php thc chn th qu chn

khng bnh thng, qu khng c hng v, khng c mu sc c trng ca ging

nn khng thch hp cho vic thu hi v bo qun.

- Thi k chn xanh (Green): Cht keo bao quanh ht c hnh thnh. Qu pht

trin y v kch thc, qu cha c mu hng hoc mu vng. Nu em thc

chn th qu s th hin mu sc ca ging. Do trong giai on ny khi tri qua qu

trnh chn qu s chu c nhit lnh khc nhau nn khng thch hp cho bo

qun.

- Thi k chn vng (Breaker): nh qu xut hin mu vng hoc mu hng vi

din tch b mt chim khong 10%.


TRANG 36

- Thi k chuyn mu (Turning): Din tch b mt t 10-30% c mu vng hoc .

- Thi k chn hng (Pink): 30-60% din tch b mt qu c mu hng nht hoc

mu vng. Qu t chn cao nn tri qua cc giai on sinh l quan trng nn

rt kh nh gi hiu qu ca bo qun thng qua cc ch tiu c lin quan ti cc

qu trnh sinh l nh h hp, bin i mu scV vy dng chn ny bo

qun trong th nghim l khng thch hp.

- Thi k qu hng hoc (Light Red): 60-90% din tch b mt qu c mu vng

hoc . Qu chn qu nn khng th phn tch c hiu qu bo qun.

- Thi k qu chn (Red): Trn 90% din tch b mt c mu . Trong thi k

ny cng khng th phn tch c hiu qu bo qun.

Qua nh gi cho thy thch hp nht cho qu trnh thu hi bo qun l khi

qu t chn vng (Breaker) v thi k chuyn mu (Turning). chn ra mt

chn thch hp nht cho bo qun bng chitosan, ti tin hnh lm th nghim

kho st s b: thu hi hai chn d kin v tin hnh nhng vo dung dch

chitosan chun b bo qun. Bo qun cng mt iu kin trong phng th

nghim. Sau 14 ngy trn c s nh gi mu sc, trng thi s b rt ra c mt

s kt lun sau:

Hai chn kho st u c mu bin i ng u.

Qu chn vng c cng cao hn.

Nh vy c hai chn u thch hp cho vic nh gi hiu qu bo qun,

song chn vng (Breaker) cho thi gian bo qun lu hn do qu cn xanh hn

thi k chuyn mu (Turning).

V vy chn thch hp cho vic bo qun cng nh nh gi hiu qu bo

qun bng chitosan l thi k chn vng (Breaker). Tuy nhin y mi ch l nhng

kho st s b do thi gian nghin cu cha p ng c, v vy mt kin ngh

cho vic kho st chnh xc chn ca c chua ph hp nht cho vic bo qun

bng chitosan l cn thit.


TRANG 37

3.3. Chitosan v cc nng to mng bao

Chitosan phc v th nghim c cung cp t trng i Hc Thy Sn Nha

Trang- (Nguyn nh Chiu, Nha Trang, Khnh ha, Vit Nam) c nhng c tnh

sau

Bng 3.1: c tnh ca chitosan

c tnh Gi tr

m 10%

Hm lng ion Ca2+ 0.01%

nht 265cps

Hm lng cht khng tan 0.18%

Hm lng Nit tng s 8,42%

Deacetyl 87.8%

tan (trong dung dch CH3COOH 1%) 99,82%

Phn ng Biure m tnh

Hm lng chitosan 89,82%

Qua cc ti liu nghin cu ch ra rng chitosan tan tt trong dung dch axit

axetic 1%.

Th nghim tin hnh pha chitosan trong dung dch axit axetic 1% thu

c dung dch chitosan: 0.5%, 1.0%, 1.5%, 2.0%, 2.5% cc nng ny

chitosan u tan ht sau 24h cho dung dch trong c mu vng ng nht, dung dch

khng c vn c hay vn cc. nht tng ln theo nng ca chitosan. Ring

dung dch chitosan nng 3.0% chitosan khng tan ht v c vn cc. Nn

nng 3.0% chitosan khng tan ht trong dung dch axit axetic 1%.

xc nh chitosan thch hp lm mng bao theo th nghim c cung cp

t trng i Hc Thy Sn Nha Trang- (Nguyn nh Chiu, Nha Trang, Khnh

Ha, Vit Nam) tin hnh th nghim theo s sau :


TRANG 38

Hnh 3.1: S b tr tin hnh th nghim

Qua s b tr th nghim trn cc tc gi kt lun rng nng chitosan

1.5% v 2% th cho kt qu tt nht vi t l hao ht thp, mu sc sn phm p,

thi gian bo qun c ko di .

3.4. Kho st s b s ln nhng chitosan ph hp cho bo qun

Dung dch chitosan c nht nn c kh nng bm dnh trn b mt qu c

chua v to mng khi kh. Tuy nhin do b mt qu nhn nn kh to iu kin

tt cho vic to mt lp mng u trn b mt qu, v th s nh hng khng nh

ti hiu qu cng nh s nh gi kh nng ng dng chitosan trong bo qun c

chua.

Nhit lnh 12-13

oC

Nhit thng

Xc nh cc ch tiu: Hao ht khi lng, ng kh, axit, vi sinh vt

tng s, cht kh ho tan, mu sc, cng, cng h hp, cm quan.

Nhn xt-Kt lun

La chn-Ra sch

kh

0.5% 1.0% 1.5% 2.0% 2.5%

Bo qun

Nhng vo dung dch chitosan

0%


TRANG 39

Do thi gian cn hn ch nn vic nh gi s ln nhng ch da trn s quan

st lp mng to c trn b mt qu sau khi nhng vo chitosan v kh.

Qua kho st nhn thy rng: vi ch 1 ln nhng th tt c cc nng mng

chitosan to c u khng u (soi nghing trn nh sng thy nhng vt loang

khng bao ph ton b b mt qu). Cc nng 0.5%; 1.0% do nht ca cc

dung dch ny thp nn phi nhng n ln th 3 th mng chitosan mi bao ph ht

ton b b mt qu, sau mi ln nhng kh trong 15 pht. Cc nng 1.5%;

2.0%; th nhng 2 ln, ring nng 2.5% do nht kh cao nn ch cn nhng

mt ln l mng chitosan bao ph ton b b mt qu.

3.5. iu kin bo qun

3.5.1. Bo qun nhit thng

Qu c bo qun v theo di mi trng phng th nghim vi nhit

bin i trong khong t 22-28 0C m nm trong khong 80-85% (iu kin kh

hu bin i t thng 2 ti thng 5).

3.5.2. Bo qun nhit lnh

Theo di nh hng ca chitosan kt hp vi bo qun lnh bng cch bo

qun trong ngn di t lnh vi nhit trong khong 12-130C l khong nhit

ti u bo qun c chua. Trong iu kin t lnh khng ch nhit ny cn

hn ch vic m t thng xuyn v lun duy tr m 90%.

3.6. Bin i cng ca qu trong qu trnh bo qun

Trong qu trnh bo qun trong qu protopectin b thy phn thnh pectin ha

tan lm cho qu mm dn. Th nghim c thc hin vi cc nng chitosan nhu

bn di v ch dng mt ln nhng.

3.6.1 Bin i cng trong mu bo qun thng

Kt qu o cng mu bo qun thng c biu din thng qua biu sau:

Bng 3.2: Bin i cng (mu bo qun thng- kg/cm2)


TRANG 40

Nhn xt:

Vi mu i chng (0%) cng gim rt nhanh sau 15 ngy u tin bo

qun (t 5.5-1.2 kg/cm2). Do trong giai on ny qu chn rt nhanh nn lng

protopectin c trong qu xanh b bin i rt nhiu. Din bin ny cng trng vi

thi k qu h hp mnh nht (trnh by trong phn bin i cng h hp) nn

cc hp cht b bin i nhanh chng. Sau 20 n 25 ngy bo qun qu trnh gim

cng din ra chm dn do lng protopectin c sn trong qu xanh ban u

khng cn nhiu v giai on ny h hp ca qu cng gim dn, qu bt u b

bin phn hy su sc v h hng.

Cc mu 0.5%; 1.0% cng bin i tng t mu i chng nhng cng

ca qu cng thi im lun cao hn. Chng t khi bo qun bng chitosan qu

c cng hn khi khng dng.

Vi mu 1.5% v 2.0% th ban u sau 15 ngy bo qun th cng ca

mu 2.0% gim nhanh hn mu 1.5% nhng sau th mu 2.0% gim t hn nhiu

so vi mu 1.5% iu ny c th c gii thch do cng h hp ban u ca

mu 2% din ra mnh hn mu 1.5% nhng sau qu trnh ny b hn ch dn ti

cng ca qu t bin i hn.

Ring mu 2.5% th ban u cng bin i t nht nhng sau 25 ngy bo

qun th cng gim thp hn mu 2.0%

Kt lun:

Nng

Ngy

0% 0.50% 1.00% 1.50% 2.00% 2.50%

0 5.5 5.5 5.5 5.5 5.5 5.5

6 3.13 2.86 3 3.8 3.5 4

15 1.166 2.25 2.25 2.733 2.433 3.6

25 0.5 1.9 1.875 1.833 2.5 2.366


TRANG 41

Nhn vo biu ta c th nhn thy cng mt thi im th bin thay

i cng ca mu c dng chitosan so vi mu i chng l rt r rt. iu ny

chng t chitosan c th lm gim s bin i cng ca qu.

Hiu qu lm gim s bin i cng qu c chua khi bo qun bng mng

chitosan c nng 2% v 2.5% l tt nht.

3.6.2 Bin i cng mu bo qun lnh

cng ca mu bo qun lnh cng c o bng my o cng thi

im ban u, sau 6 ngy, 15 ngy, 30 ngy bo qun.

Khi bo qun c chua bng chitosan kt hp vi bo qun nhit lnh th

cng ca qu bin i t hn so vi bo qun nhit thng.

So snh vi s bin i cng ca mu bo qun thng ta thy mu bo

qun lnh bin i t hn cng thi im vi tt c cc nng . iu ny l do

tc dng hn ch h hp v bin i cht trong mi trng bo qun lnh, nhit

lnh tt c cc qu trnh sng ca qu din ra chm hn nhit cao v vn

ny c rt nhiu nghin cu chng minh.

3.7. Qa trnh bin i mu sc qu

Khi chn c chua chuyn dn t mu xanh sang mu vng ri mu . iu ny

l do clorophil chuyn thnh carotinto nn mu sc ca qu chn.

Tc bin i cc thnh phn ha hc trong c bin i v mu sc t l

thun vi cng h hp.

Mu sc ca qu c kho st thng qua s sai khc v mu (E) trc v sau

thi gian bo qun, c xc nh bng my o mu. nh gi ti thi im ban

u v sau 6 ngy, 15 ngy, 25 ngy bo qun.

Thi gian bo qun cng lu th mu sc bin i cng nhiu do qu cng chn.

Do qu trnh chn t l thun vi cng h hp nn mu sc qu bin i

iu ny c c l do cng h hp khi bo qun bng chitosan c hn ch

hn.


TRANG 42

Nhng y ch yu l h hp ym kh do mng chitosan qu dy hn

ch ti a lng kh oxi trao i vi qu v ti ngng lm qu trnh h hp ym

kh xy ra mnh m kt hp vi lng nhit sinh ra khng ta ra ngoi mt cch

hiu qu nn qu bin i nhiu hn cc mu khc.

so snh nh hng ca mng chitosan trong bo qun thng kt hp vi

bo qun lnh ti cng mu ca c chua chng ti tin hnh o s bin thin

cng mu ti cng mt thi im (15 ngy sau bo qun) c hai ch bo

qun lnh v bo qun thng v kt qu thu c nh sau:

Qa trnh bo qun c chua bng chitosan nhit thng v nhit lnh

th kh nng lm gim s bin i mu sc khi kt hp vi bo qun lnh l rt r

rt. Ta thy s bin i mu ca mu bo qun lnh u thp hn mu bo qun

thng. Nh vy nhit thp cng h hp gim hn lm mu sc qu

bin i t hn, iu ny mt ln na minh chng cho s ph thuc ca s bin i

mu sc vo cng h hp.

Nh vy kh nng lm gim cng h hp ca mng chitosan c

chng minh mt phn thng qua mu sc qu khi bo qun.

Kt lun:

Mng chitosan c kh nng lm gim s bin i mu qu mt cch r rt.

S kt hp mng chitosan vi bo qun lnh lm gim s bin i mu sc

tt c cc nng .

nng 2.0% mng chitosan cho hiu qu lm gim kh nng bin i

mu tt nht ca qu c chua c 2 ch bo qun lnh v bo qun

thng.

3.8.nh hng ca mng chitosan ti cng h hp ca c chua

Khi bo qun mi rau qu khc cng nh c chua lun c cc hot ng

sng, trao i cht. Trong in hnh nht l qu trnh h hp c bn l qu

trnh s dng cc hp cht c tng hp khi qu cn trn cy duy tr s

sng ca qu.


TRANG 43

C chua khi bo qun ph thuc vo thnh phn khng kh bn ngoi m s

h hp c th l hiu kh hoc ym kh. C hai qu trnh ny u lm bin i cc

cht trong qu, nhng hn ch ti a h hp ym kh v gi h hp hiu kh mc

ti thiu chnh l bi ton ti u ca phng php bo qun ny.

Chitosan l cht c kh nng to mng, ty theo nng m kh nng thm

kh (O2) ca chng khc nhau, v khi lm mng bao th kh nng iu chnh h hp

ca chng theo cng khc nhau.

nh gi kh nng iu chnh h hp ca mng chitosan, thng qua cc

kt qu nghin cu v cng, bin i mu v hao ht khi lng chng ti nhn

thy nng chitosan cho kt qu tt l 1,5% v 2,0%, kt hp vi iu kin thit

b khng cho php. V vy trong phn nghin cu xc nh cng h hp ca

qu ch xc nh ti ba mu: mu i chng, mu 1.5 % v mu 2.0 % vi cng thi

gian v iu kin bo qun (nhit thng).

Kt qu thu c nh sau:

Cng h hp

0

10

20

30

40

50

60

0 2 4 6 8 10 12 14 16

ngy

mg

CO

2 /k

g.h

Mu DC

Mu 1,5%

Mu 2%

Hnh 3.2: nh hng ca mng chitosan ti cng h hp

Nhn xt:

Nhn vo biu ta thy c chua l loi qu c h hp t bin (Climacteric).

Cng h hp bin i ln xung theo thi gian bo qun.


TRANG 44

Tt c cc nng biu u ging nhau, chng t din bin h hp ca

chng l nh nhau nhng ch khc nhau v cng . Ban u do qu cn ng nn

cng h hp gim dn trong 4 ngy u bo qun giai on ny l thi k ng

tnh ca qu, qu kt thc giai on tch ly dinh dng nh khi cn trn cy m v

chun b qu trnh chn nn cc phn ng tng hp din ra chm hn v lng CO2

thot ra gim i.

Sau thi gian ng tnh h hp bt u tng ln v qu bt u chn. Lc ny

hng lot cc phn ng m ch yu l cc phn ng phn hy (ch yu l phn hy

ng) v bin i cht ny thnh cht khc (tinh bt bin thnh ng) xy ra

mnh m v lng CO2 thot ra nhiu. Cng h hp t cc i (im

climacteric cc i) sau 8 ngy bo qun lc ny qu chn hon ton.

Tri cy sau khi chn hon ton th bt u giai on phn hy v cht. Giai

on ny ch yu l cc phn ng t phn khng khng sinh ra nhiu CO2. Cng

h hp gim dn sau 9 ngy bo qun.

Da vo biu ta thy mu 2.0 % c cng h hp thp nht, giai on

h hp cc i mu 1.5 % c cng h hp mnh hn mu i chng nhng

giai on sau th thp hn. iu ny c th gii thch nh sau: Mng chitosan 1.5%

c kh nng tch lu kh ethylen sinh ra do qu trnh h hp nhiu hn mu 2% nn

kh nng kch thch ca kh ny ti cc h enzyme h hp, c bit l amylaza lm

chuyn ho tinh bt thnh ng, lng ng tng ln lm cho h hp v qu trnh

chn tng ln.

mu 2% kh ethylen cng c tch lu song do mng chitosan dy hn

nn lng O2 cung cp cho h hp t hn nn h hp vn thp hn. Do mng

chitosan c kh nng thm kh nn lng khng kh trao i gia mi trng v qu

b thay i dn ti cng h hp thay i. Cng h hp cng thp qu cng

chn chm hn. Mu 2.0 % c kh nng lm gim cng h hp tt nht, qu

trnh thm kh O2 v thot CO2 trnh ym kh din ra rt c li cho bo qun.

Thi k h hp cc i ca mu i chng din ra lu hn hai mu cn li l

do nhu cu O2 lun c p ng t mi trng, trong khi do c kh nng thm


TRANG 45

kh t t nn lng ny cung cp cho qu mu 1.5 % v mu 2.0 % b hn ch

hn.

Cng h hp ca mu 2.0 % thp nht chng t lng O2 vn duy tr

h hp hiu kh v khng xy ra h hp ym kh.

Kt lun:

Mng chitosan c kh nng lm bin i thnh phn khng kh cung cp cho

qu trnh h hp ca qu.

Mng chitosan nng 2.0 % c kh nng hn ch h hp mc thp nht.

Qu chn chm nht.

Mng chitosan 2.0 % khng lm qu b h hp ym kh mnh m.

3.9. Bin i hm lng acid chung trong qu trnh bo qun

Acid cng tham gia mt phn rt nh vo qu trnh h hp, nhng ch yu l

qu trnh tng hp nn acid l hp cht trung gian ca cc qu trnh. Cc giai on

pht trin khc nhau cho hm lng acid bin i khc nhau. nh gi s nh

hng ca mng bao chitosan ti hm lng acid chung khi bo qun c chua tc

gi tin hnh o tt c cc nng sau mi 5 ngy bo qun i vi mu bo

qun thng.

Nhn xt:

Tt c cc mu u c s bin thin hm lng acid chung ging nhau v ch

khc nhau v cng .

Nhng ngy u ca qu trnh bo qun hm lng acid tng ln nhanh chng,

sau 5 ngy bo qun hm lng acid t cc i. Do ban u khi qu cn xanh v

bt u chuyn sang giai on chn, cc hot ng ha sinh xy ra mnh m, cng

h hp cha cao nn lng acid c tng hp khng b mt i. Chnh v vy

cng vi qu trnh chn ca qu th hm lng acid tng ln.

Sau khi t cc i th hm lng acid bt u gim xung (sau 5 ngy bo

qun) do lc ny cng h hp bt u tng mnh m, cc cht hu c d tr

tham gia nhiu vo qu trnh h hp. Sau giai on ny lng acid li tng ln rt


TRANG 46

nhanh cho n cui giai on bo qun. Do trong qu trnh h hp mt s acid l

cc hp cht hu c trung gian c hnh thnh lm chua ca qu tng ln v

qu cng chn th chua cng tng. iu ny cng mt phn l do hm lng

ng kh c s dng phn ln cho h hp. V mt s qu trnh phn hy khi

qu h hng cng sinh ra acid (Protein t phn hy cng to ra acid, s thy phn

ng, cht bo c nhiu trong ht c chua thnh nhng mnh 2 cacbon trong chu

trnh Kreb cng to ra nhng hp cht trung gian l cc acid hu c) .

Nh vy qu chn cng nhanh th lng acid cng tng, cho ti khi qu b h

hng.

Ta thy nng chitosan trong mu bo qun c chua cng cao th cng

bin i acid chung ln nht iu ny cho ta thy do mng chitosan qu c nn s

khuch tn kh oxi t mi trng vo b hn ch lm qu h hp ym kh, thc cht

l cc qu trnh phn hy khng c mt ca oxi, kt qu ca qu trnh ny to ra

nhiu cht trung gian, trong phi k n l cc nhm ru v acid hu c.

Ban u th acid tt c cc mu cn li u tng vi t l khc nhau khng

nhiu. y vn l thi k tch ly ca qu xanh nn mng chitosan khng nh

hng nhiu ti kt qu .

3.10. Bin i hm lng ng kh trong qu trnh bo qun

Trong qu trnh h hp c hiu kh v ym kh c cht c s dng ch yu

l cc ng kh (ch yu l Glucoza), nhng cng vi qu trnh ny l s bin i

cc polysacaride khc m quan trng nht l tinh bt chuyn ha thnh ng nh

cc enzyme thy phn.

Kt qu bin i hm lng ng kh c m t thng qua biu sau:


TRANG 47

0

1

2

3

4

5

6

0 5 10 15 20 25 30

Ngy bo qun

%

ng

kh

0%

0.50%

1%

1.50%

2.00%

2.50%

Hnh 3.3: Bin i ng kh theo thi gian bo qun (mu bo qun thng)

Nhn xt:

Hm lng ng kh bin thin rt nhiu theo thi gian bo qun.

Sau 6 ngy u bo qun lng ng kh gim xung thp nht l do trong

giai on qu cn xanh lng ng kh trong qu khng nhiu, cc enzyme thy

phn vn cn nm dng lin kt nn tinh bt cha b chuyn ha thnh ng,

mt khc trong giai on ny h hp bt u tng ln, qu khng cn giai on

ng tnh nn lng ng gim i nhanh chng.

Hm lng ng kh bt u tng ln khi h hp gim i v ti 14 ngy th

t cc i, iu ny trng khp vi thi im h hp gim mnh. Mt khc trong

giai on ny cc enzyme b hot ha v qu trnh chuyn ha tinh bt thnh

ng din ra mnh m. Sau khi t cc i hm lng ng kh gim xung

tt c cc mu tng ng vi thi k phn hy ca qu. Lc ny qu trnh phn hy

ng din ra chim u th hn hn qu trnh tng hp. Qu bt u i vo giai

on h hng.

Ta thy mu bo qun c chua bng chitosan vi nng 2.0 % sau thi gian

bo qun c hm lng ng kh vn cao, iu ny c c l do h hp ca mu

ny b hn ch hn so vi cc mu khc, h hp hiu kh khng xy ra v nu xy ra


TRANG 48

th lng ng s dng cho h hp tng ln lm cho tng lng ng kh gim

i.

mu i chng sau thi gian bo qun hm lng ng kh gim i

nhanh chng do sau qu trnh h hp qu chuyn sang giai on phn hu (qu

chn). iu ny mt ln na chng t tc dng ca mng bao chitosan ti qu trnh

bo qun.

Sau 8 ngy bo qun khi h hp ca mu 2.0 % t cc i th lng ng

kh gim, nhn vo biu ta thy mu i chng lng ng kh gim nhiu

nht, mu 2.0 % li c xu hng tng l do h hp b hn ch hn.

Kt lun:

Sau thi gian bo qun hm lng ng kh mu 2.0 % l nhiu nht.

Cng ti im Climacteric lng ng kh ca mu i chng thp nht

chng t h hp mnh nht. Nh vy tc dng ca mng chitosan ti cng

h hp li mt ln na c khng nh.

3.11. Hao ht khi lng trong qu trnh bo qun

Trong qu trnh bo qun c nhng bin i v phn ng xy ra ht sc phc

tp, nhng bin i sinh ha ny khng nhng lm thay i v cht m cn dn ti

bin i nhiu v lng.

C chua l mt loi qu c cha nhiu nc (84%-88%) nn lun xy ra hin

tng bay hi nc ra mi trng bn ngoi, bn cnh c qu trnh h hp ca

qu lm gim hm lng cht kh. C hai yu t ny u lm hao ht khi lng

ca qu trong sut qu trnh bo qun, trong 75-85% s gim khi lng l do

bay hi nc cn li l do h hp lm tiu hao hm lng cht kh.

3.11.1 Hao ht khi lng mu bo qun lnh

kho st s hao ht khi lng khi bo qun, ti dng phng php cn

khi lng qu trc v sau mi thi gian bo qun, s hao ht c nh gi theo

phn trm khi lng.

Nhn xt:


TRANG 49

Thi gian bo qun cng lu th khi lng hao ht cng nhiu, iu ny xy

ra tt c cc mu.

Nng chitosan trong mng bao cng ln th khi lng hao ht cng t, do

mng bao cng dy v kn nn s bay hi nc ra ngoi mi trng b hn ch.

Ngoi ra cn k ti cng h hp b hn ch mt phn nn khi lng qu cng

t mt i.

bt k thi im bo qun no mu 2.0 % v mu 2.5 % cng c hao ht t

nht, chng t mng bao kn v hn ch tt s bay hi nc ca qu.

Sau 21 ngy bo qun th mu 2.0 % v mu 2.5 % ch mt i 3.34%. iu

ny ni ln tnh hiu qu ca mng chitosan ti vic ngn chn kh nng bay hi

nc ca qu ra ngoi mi trng.

Kt lun:

Mng chitosan c kh nng lm gim ng k s hao ht khi lng qu khi bo

qun.

Nng chitosan cng cao th kh nng hn ch hao ht khi lng cng nhiu.

Mu 2.0 % v mu 2.5 % t hao ht khi lng nht.

3.11.2. Hao ht khi lng mu bo qun thng

Nhn xt:

Thi gian bo qun cng di th khi lng mt i cng nhiu.

cng mt thi im mu bo qun thng mt nhiu khi lng hn mu bo

qun lnh tt c cc nng . iu ny chng t hiu qu ca bo qun lnh ti

hao ht khi lng. Do trong iu kin bo qun lnh ca th nghim c m

khng kh lnh ln hn nn chnh lch m gia qu v mi trng ngoi t i v

ng lc bay hi nc gim i.

Ti cng mt thi im bo qun khi lng b mt i t l nghch vi nng

chitosan l do mng chitosan ngn cn s bay hi v hn ch mt phn h hp.

Kt lun:

Mng chitosan c kh nng hn ch s bay hi nc ca qu.


TRANG 50

Nng chitosan cng cao hao ht khi lng cng t.

C chua c bo qun lnh hao ht t hn bo qun iu kin thng.

Mng chitosan c nng thch hp khong 1.5%; 2.0 % v 2.5% c kh nng

lm gim s mt khi lng t nht.

3.12. Bin i cht kh ha tan theo thi gian bo qun

Trong qu trnh bo qun cht kh ha tan ca qu bin i do hai qu trnh

ngc nhau xy ra ng thi: qu trnh h hp v cc phn ng sinh ha khc lm

gim cht kh ho tan cng vi n l qu trnh bin i nhng cht khng tan thnh

cht tan.

3.12.1. Bin i cht kh ha tan mu bo qun thng

Cht kh ha tan bin i theo thi gian bo qun.

C chua sau 30 ngy bo qun th cht kh ha tan chung gim i. Do ti

thi im ny qu h hng nhiu nn cc cht ha tan b phn hy nhiu.

Vi nng chitosan 2.0 % s bin i cht kh ha tan theo thi gian bo

qun l t nht. Sau 15 ngy cht tan gn nh khng thay i l do h hp ca mu

ny b hn ch hn cc mu khc nn cht tan gim i t hn cc mu khc.

3.12.2. Bin i cht kh ha tan mu bo qun lnh

Nhn xt:

Sau thi gian bo qun lng cht kh tan gim do lc no qu b h

hng nn cc cht tan b phn hy nhiu, cc mu cn li cht tan u tng.

iu ny c th c c l do h hp b hn ch nn qu trnh chuyn ha

cc cht lm tng cht kh ha tan chim u th hn.

Kt lun:

Sau thi gian bo qun mu 1.5 % v mu 2.0 % cht kh ha tan tng nhiu

nht, qu ang giai on chn y , trong khi mu i chng chuyn sang

giai on h hng, phn hy.


TRANG 51

3.13. Xc nh vi sinh vt tng s

Vi sinh vt tng s l tng tt c cc vi sinh vt sng trn mi trng dinh

dng chung khi nui cy trong thi gian 48h. nh gi kh nng khng khun

ca mng chitosan chng ti tin hnh xc nh vi sinh vt tng s trn b mt qu

c chua mu i chng v mu c bo qun bng chitosan 2% c iu kin bo

qun thng v bo qun lnh.

0

50000

100000

150000

200000

250000

300000

350000

400000

450000

500000cfu/g

Ban u Sau 14 ngy

ngy bo qun

i chng

Chitosan 2%

Hnh 3.4: Lng vi sinh vt tng s (mu bo qun thng)

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000cfu/g

Ban u Sau 14 ngyngy bo qun

i chng

Chitosan 2%

Hnh 3.5: Lng vi sinh vt tng s (mu bo qun lnh)


52

Nhn xt:

Thi gian bo qun cng lu th lng vi sinh vt tng s cng nhiu do vi sinh

vt pht trin v sinh si, ngoi ra cn c mt lng ln thm nhp t mi trng bo

qun. C chua khi cn xanh c kh nng khng mnh hn khi qu chn.

Sau 14 ngy bo qun lng vi sinh vt tng ln rt nhiu c mu i chng

v mu c bo qun bng chitosan. Tuy nhin mu bo qun bng mng chitosan t l

tng ny t hn rt nhiu so vi mu khng bo qun bng chitosan. iu ny chng t

kh nng khng khun rt tt ca mng chitosan.

Cc khun lc quan st c hu ht l cc nm mc, chng t chitosan c kh

nng c ch s pht trin ca nm mc kh mnh.

mu bo qun lnh lng vi sinh vt tng s pht trin t hn hn mu i

chng iu ny c c l do nhit lnh c tc dng hn ch s pht trin ca vi

sinh vt trn b mt qu. Vi sinh vt ch yu trn b mt l loi a m v km chu

lnh nn nhit thp chng b c ch nn hot ng sng v sinh sn km hn

nhiu so vi iu kin thng.

Kt lun:

Mng chitosan c kh nng khng khun cao. C th dit c 96% vi sinh vt

trn b mt qu.

Nhit thp c kh nng c ch vi sinh vt pht trin trn b mt c chua.

Vi sinh vt trn b mt c chua ch yu l nm mc.

3.14. Kt lun chung

Qua cc ch s phn tch trn ta nhn thy:

Tc dng bo qun ca mng chitosan rt r rt.

Mu bo qun bng mng chitosan 2% cho cht lng tt nht c ch bo qun

lnh v bo qun thng.

Chitosan kt hp vi bo qun lnh cho hiu qu cao hn bo qun thng tt c

cc ch tiu

3.15. nh gi cm quan mu

3.15.1 nh gi cm quan mu bo qun iu kin thng


53

Bng 3.3: kt qu mu bo qun thng 0% chitosan sau 20 ngy bo qun

Bng 3.4: Kt qu mu bo qun thng 2.0% chitosan sau 20 ngy bo qun

Ch

tiu

im tng thnh vin

TNG

Trung

bnh cha

c trng

lng

H s

trng

lng

Trung

bnh c

trng

lng

T1 T2 T3 T4 T5

Mu

sc 2 1 0 0 1 4 0.8 2 1.6

Trng

thi 0 1 0 0 0 1 0.2 2

0.4

im cht

lng: 2.0

Ch tiu

im tng thnh vin

TNG

Trung

bnh cha

c trng

lng

H s

trng

lng

Trung

bnh c

trng

lng

T1 T2 T3 T4 T5

Mu sc 5 5 4 5 4 23 4.6 2 9.2

Trng

thi 5 4 4 5 4 22 4.4 2

8.8

im cht

lng:

18.00


54

3.15.2 nh gi cm quan mu bo qun iu kin lnh

Bng 3.5: Kt qu mu bo qun lnh 2.0% chitosan sau 30 ngy bo qun

Bng 3.6: Kt qu mu bo qun lnh 0% chitosan sau 30 ngy bo qun

Kt lun:

Sau 30 ngy bo qun kt qu cm quan ch ra rng: nng chitosan 2%

cho cht lng cm quan tt nht c 2 ch bo lnh v bo qun thng

3.16. Chi ph nguyn liu cho bo qun

S liu thc t khi tin hnh lm th nghim thu c nh sau:

Trng lng trung bnh ca qu:83,33g

Ch tiu

im tng thnh vin

TNG

Trung

bnh cha

c trng

lng

H s

trng

lng

Trung bnh

c trng

lng T1 T2 T3 T4 T5

Mu

sc 5 5 5 5 5 25 5 2 10

Trng

thi 4 4 5 4 4 21 4.4 2

8.4

im cht

lng: 18.4

Ch tiu

im tng thnh vin

TNG

Trung

bnh cha

c trng

lng

H s

trng

lng

Trung

bnh c

trng

lng

T1 T2 T3 T4 T5

Mu sc 1 2 0 1 2 6 1.2 2 2.4

Trng

thi 0 1 0 0 3 4 0.8 2

1.6

im cht

lng: 4.0


55

Lng dung dch chitosan 2.0 % tiu tn cho 2kg qu l: 20ml

500ml dung dch c th bo qun c 50kg c chua.

Bng 3.7: Tnh gi thnh ph thuc vo chi ph nguyn liu chnh:

S lng n gi Gi thnh

C chua 50kg 3.000/kg 150.000

Chitosan 0.01kg 500.000 /kg 5.000

Axit axetic 0.005l 100.000 /l 500

- Tng gi thnh chi ph nguyn liu cho bo qun 50kg c chua l: 155.500 .

- Chi ph nguyn liu bo qun 1kg c chua l: 110 VND.

- Hao ht khi lng sau thi gian bo qun bng chitosan l 7%. Tng ng vi c

1kg c chua bo qun bng chitosan s mt i 210 VND.

- Tng chi ph cng hao ht khi lng khi bo qun bng chitosan l: 320 VND.

Trong khi :

- hao ht khi lng qu khi bo qun nu khng dng chitosan l 11.72%.

- Vy c 1kg c chua khng c bo qun bng chitosan s mt i 0.1172 kg tng

ng vi 351.6 VND.

Tm li

- Nu dng chitosan bo qun mt 320VND, trong khi nu khng dng

chitosan s mt 351.6 VND cho mi kg c chua.

- Mt khc dng chitosan cn ko di c thi gian bo qun nn gi tr gia

tng thu c rt ln t sn phm tri v.


56

3.17. Xy dng quy trnh bo qun c chua bng chitosan

3.17.1. S quy trnh bo qun

Thi gian t 1- 2 pht

Hnh 3.6: S quy trnh cng ngh bo qun c chua bng chitosan

3.17.2. Thuyt minh quy trnh bo qun

Nguyn liu:

- C chua c la chn theo ging c trng v cung cp n nh ti vng nguyn

liu.

Bo qun 12- 13 oC

Dch chitosan hi lu

Pha dch chitosan

2%

Chitosa

n

Dung dch axit axetic

1%

Nguyn liu

La chn-Phn loi

Ra sch

kh

Nhng chitosan ln 1

kh trong 15 pht

Nhng chitosan ln 2

kh

Xp vo khay bo qun


57

- Chn chn thu hi bo qun khi qu chn vng (Breaker) - qu bt u xut

hin mu vng hoc hng vi din tch chim 10% b mt.

La chn v phn loi:

C chua c la chn bng my da vo kch thc ca qu vi mc ch to s

ng u hiu qu bo qun cao hn v d c gii ha.

Ra sch: c chua c ra sch bng my, c th kt hp gia qu trnh ra v

phn loi qu. Sau khi ra sch qu c kh mng chitosan bm tt trn b mt.

Chun b dch chitosan 2%: dung dch chitosan 2% c pha trong axit axetic

1% cho ti khi khng cn vn cc v khng c vn c. Sau khi pha dung dch c

lc qua vi lc nhm loi b nhng cn bn.

Nhng qu vo dung dch chitosan: qu sau khi kh c nhng vo dung

dch chitosan t 1- 2 pht c nhng theo hai ln, gia mi ln c se b mt trong

15 pht (trnh lm kh hon ton b mt khi s to hai lp mng dy). Dung dch

chitosan tha chy t qu ra c thu hi, lc cn bn v dng li cho ln nhng tip

theo.

Xp khay: sau khi mng chitosan to c trn b mt qu kh ht th tin hnh

xp qu vo khay. Mi khay c th xp 3-4 lp qu, khng xp qu cht qu trnh

trao i kh din ra d dng. S dng khay c l lm bng tre hoc nha do. Cc khay

c th c xp trng ln nhau trn cc gi sai cho qu khay di khng b ln

khay trn. Mi gi ti a nn l 5 khay qu trnh ta nhit din ra tt v trnh h

hp ym kh.

Bo qun:

Cc gi c xp vo kho bo qun vi khong cch hp l m bo iu

kin cho qu hot ng sng bnh thng, trnh tng nhit cc b v CO2 thot ra d

dng. C th bo qun trong kho c thng kh cng bc hoc kho lnh th thi gian

bo qun lu hn nhng tn km hn.

C chua c th bo qun c 24-26 ngy nhit thng v 35-38 ngy

nhit lnh 12- 13 oC ty theo iu kin bo qun, m vn cho cht lng tt c th

dng cho n ti hoc ch bin.


58

CHNG IV: KT LUN V KIN NGH

4.1. Kt lun

Chitosan l mt polysaccharide c sn xut t ph ph phm thy sn c

nhiu tnh cht vt l, ha hc v sinh hc ng qu nh kh nng khng khun, kh

nng to mng bao c thong kh

Quy trnh sn xut chitosan n gin gm cc quy trnh chnh nh thy phn

protein, kh khong v deacetyl ha trong mt s quy trnh sn xut chitosan bng

phng php ha hc ang c nghin cu thay th bng quy trnh sinh hc hay s

dng enzyme thn thin vi mi trng.

Nhng nghin cu nhm s dng chitosan lm mng bo qun tri cy, rau qu

ni chung v c chua ni ring cho thy ch cn nhng tri cy, rau qu trong dung

dch chitosan vi nng 2% th c chua c th bo qun c 28 ngy nhit

thng v 35 ngy iu kin lnh nhit khong 12 13 oC.

4.2. Kin ngh

Hon thin nghin cu s dng chitosan trong bo qun c chua nh:

o Xc nh cc cht dinh dng khc trc v sau khi bo qun.

o Kho st ging c chua bo qun cho hiu qu cao hn trong tng

lnh vc sn xut v xut khu.

o Nghin cu kt hp cc ha cht bo qun khc vi chitosan nng cao

hiu qu bo qun rau qu.

o Nghin cu cc quy trnh p dng cng ngh sinh hc vo sn xut

chitosan t ph ph phm ca ngnh thy sn nh u tm, mai gh

Xy dng m hnh, la chn thit b, nh gi hiu qu kinh t a phng

php bo qun c chua bng chitosan vo thc t.

Kho st tnh cht v la chn chitosan ph hp nht cho bo qun rau qu.

ng dng chitosan bo qun loi qu khc.


59

TI LIU THAM KHO

Ti liu ting Vit:

1. Chu Vn Minh: s dng chitosan lm cht bo qun qu ti Tp ch khoa hc,

trang 34, s 4-1996

2. Lu Vn Chnh. Tng hp v nghin cu hot tnh sinh hc ca mt s dn xut t

chitin. Lun n tin s

3. Nguyn Th ng. Tch chitin t ph thi thy sn bng phng php ln men axit

lactic. Lun n tin s

4. 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).

5. Nguyn Hong H, Hong L Sn. Quy trnh sn xut chitosan t v tm,

1993. ( cp n lnh vc cng ngh sn xut biopolyme, c th l cp n

quy trnh sn xut chitosan t v tm).

6. 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

7. H Vn Thuyt, Trn Quang Bnh. Bo qun rau qu ti v bn ch phm-NXB

Nng nghip, H Ni.

8. Quch nh, Nguyn Vn Tip, Nguyn Vn Thoa. Cng ngh sau thu hoch v

ch bin rau qu-NXB Khoa Hc K Thut H Ni.

9. Phan Hiu Hin. Phng php b tr th nghim v x l s liu-NXB Nng

Nghip Tp HCM

10. H Duyn T. K thut phn tch cm quan thc phm. _NXB KH&KT

11. Nguyn Xun Phng. K thut lnh thc phm, NXB Khoa hc v k thut, H

Ni.

12. H Duyn T. Qun l cht lng trong cng nghip thc phm- NXB Khoa hc

v k thut.

13. Phm Th nh Hng. 2003. K thut sinh ha. Nh xut bn i Hc Quc Gia

Tp.HCM.


60

14. Phm L Dng, Trnh Bnh, Li Thu Hin v cc cng s. 1997. Vt liu sinh hc

t chitin. Vin Ha Hc Vin Cng Ngh Sinh Hc, Trung tm khoa hc v

Cng ngh quc gia H Ni.


61

Ti liu ting Anh:

15. Production of chitosan oligosaccharide. (Sn xut chitosan oligosaccharide

v ng dng ca n trong thc phm, dc phm, m phm).

16. Joint FAO/WHO Food standards Progaramme Codex Alimentarius

Commission (1994)

17. Alvarez, Review: Active food packating. Food Sci. Tech Page 97-108.

18. Argaiz A 2004 Mechanical, physical and barrier of edible chitosan film,

Food Packating: Role of film, edible coating.

19. Caner, C. Vergano, PJ. And wiles. 1998 Chitosan film mechanical and

permeatin propertes as affected by axid.

Cc website:

20. http://members.tripod.com/~Dalwoo/structure.html

21. http://aceis.agr.ca/icar/docs/96000269.html

22. http://www.chitosan.com.cn/chitosan/news

23. www.compchem.hcmuns.edu.vn

24. www.fistenet.gov.vn

25. http://www.faostat.fao.org

v mt s website khc


62

PH LC

A.Xc nh m ca v tm kh

A.1. Thit b

Cn phn tch c chnh xc 10-4

Cc s, Bnh ht m

T sy bng in, c kh nng kim tra nhit 105 0C

A.2.Nguyn tc

Cn mu th chnh xc n 0.001g, cho vo bnh (m1)

Cc c sy kh v cn o trc (m0)

cc c cha mu th vo t sy nhit 105 0C thi gian 3 gi. Sau

lm ngui trong bnh ht m n nhit phng, em cn chnh xc n

0.001g (m2). Lp li thao tc trn nhng mi ln ch khong 30 pht trong

t sy cho n khi lng mt i ca hai ln cn lien tip khng chnh lch

nhau qu 2mg hoc 4mg ty theo khi lng ca phn mu th

A.3.Tnh ton

m tnh bng % khi lng c tnh theo cng thc sau:

[(m1 m2) * 100]/ (m1 mo)

Trong :

mo : khi lng cc khng (g)

m1 : khi lng cc v mu trc khi sy

m2 : khi lng cc v mu sau khi sy (g)

B. Xc nh hm lng tro trong v tm kh tuyt i

B.1.Dng c

Cn phn tch c chnh xc 10-4

Chn nung bng s chiu nhit hoc bch kim c dung tch t 30 50 ml

Bp in

Bnh ht m

L nung iu chnh nhit


63

L sy iu chnh nhit 105 0C

B.2. Nguyn tc

Chn cho vo l nung trong 3 gi nhit 500550 0C. Sau khi ly chn

ra lm ngui trong bnh ht m v em cn xc nh khi lng vi chnh

xc 0.001g.

Dn u mu trn y chn v t cn thn trn bp in cho n khi mu

bc ht khi, sau t chn mu vo l nung nhit 500 550 0C trong

khong t 1 2 gi. Sau ly ra ngoi lm ngui trong bnh ht m, em mu i

cn ta c khi lng m1, lm li qu trnh nung mu cho n khi khi lng khng

i.

B.3.Tnh ton

Hm lng tro th ca mu ( X ) c tnh bng % theo cng thc :

X = [(m1 m2) *100]/m

Trong :

X: hm lng tro th ca mu (%)

m1: khi lng chn v mu sau khi nung (g)

m2: khi lng chn (g)

m: khi lng mu th trc khi nung (g)

C. Xc nh hm lng Ca v P trong mu tm kh tuyt i

C.1.Xc nh hm lng calcium

C.1.1.Nguyn tc

Dng trilon B xc nh calcium trong dung dich mu vi ch th murexid

(C8H5O6N5) trong mi trng c pH = 12. K hiu cht ch th murexid l H3I-

Trong mi trng c pH = 12, H3I-

C mu tm v khi kt hp vi calcium to thnh phc cht c mu hng:

H3I- + Ca

2+ CaH3I

+

Tm hng

Cht phc hp ca Ca vi muruxid khng bn bng cht phc hp bi Ca

v trilon B y ch th murexid ra khi cht phc hp bi dng t do c mu tm:


64

CaH3I+ + H2Y

2- CaY

2- + H3I

- + 2H

+

Hng tm

C.1.2.Dng c v ha cht

Dng c :

Bnh tam gic 100 ml

ng chun 25 ml

ng ht 2, 5, 10 ml

Ha cht

Dung dch NaOH 10%

Dung dch KCN 3 %

Ch th murexid: cn 0.1g murexid + 50g tinh khit. Nghin nhuyn bng

ci, cho vo chai thy tinh c y nt kn.

Dung dch trilon B 0.02 N

C.1.3.Cch tin hnh

Ty theo hm lng Ca c trong mu,cn chnh xc 2 5g mu, nung

thnh tro trng, ha vi 5ml HCL tinh khit, un cch thy ti kh trn ni cch

thy si thc hin tng t them mt ln na. Tip cho thm 5ml HCL 20%

ha tan, lc trn giy lc khng tro. Ra chn nung nhiu ln bng nc ct nng.

Dch lc v nc ra cho c vo bnh nh mc, cui cng cho thm nc ct

100ml, ta c c dch th.

Ht 20ml dung dch th cho vo bnh tam gic 100ml thm 2ml dung dch

NaOH 10%, 5 git KCN 3% v khong na ht go ch th murexid. Chn bng

dung dch Trilon B 0.02 N cho n khi mu hng ca dung dch chuyn sang mu

tm, cn thc hin song song mt s th khng (i chng)

C.1.4.Tnh ton:

V1 = (v1*100)/a (ml/100g mu kh)

Lng calcium (tnh bng mg) trong 100g mu th l:

m1 = (v1*C*20.04*100)/a


65

Trong :

V1: th tch Trilon B cn chun khi xc nh lng calcium

trong dung dch mu tng ng vi 100g mu kh.

v1: th tch Trilon B 0.02 N dng chun .

a: trng lng mu kh tng ng vi th tch dung dch mu ly

chun .

20.04 : ng lng ca calcium

C : nguyn chun ca dung dch Trilon B

C.2.nh lng phosphor

C.2.1.Nguyn tc

Phng php da vo kh nng ca ion Orthophosphate phn ng vi

amomonium Molybdate to thnh Phosphormolybdate, phc cht c mu xanh l

2(MoO24MoO3) + H3PO4 (MoO24MoO3).2H3PO4.4H20

Hm lng phosphor ph thuc vo cng mu ca mu, o bc

sng hp th cc i 650ml vi cuvet c chiu dy 10mm, dung dch i chng l

dung dch khng.

C.2.2.Dung dch v ha cht

Dng c

Thi gian chun b l mt gi, nhy ca phng php cao do cc

dng c thy tinh i hi phi tht sch.

My quang ph c bc sng 650nm v cuvet bng 10mm.

Bnh nh mc 50,100 ml.

ng nghim.

Ha cht :

Tt c cc ha cht s dng trong tiu chun ny phi c tinh khit phn tch

Nc s dng phi l nc ct hay c tinh sch tng ng

HCL m c

HNO3 m c


66

Amobi Molybdate

Hydriquinone [ C6H4(OH)2] pha khi s dng

Kali Dihydrophotphat (KH2PO4)

Sodium sulfite (KH2PO4)

C.2.3.Cch tin hnh

Ly mu th v chun b mu theo TCVN 4325 86

Nu mu kh khng kh, x l s b v bo qun lnh

Nu mu ti, x l s b c cn, sy 60 0C, sy 105 0C nghin ly mu

trung bnh.

Chun b dch thuc th

Dung dch (1) = dung dch chun gc (c cha 100g phosphor/ ml). Ha

tan 0.394g KH2PO4 trong bnh nh mc 1000ml bng nc ct v nh mc ng

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