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CHNG 1:

TNG QUAN V VN NGHIN CU

1. TNG QUAN V NGUYN LIU DA1.1. Tnh hnh pht trin cy Da trn th gii v trong nc

Da c ngun gc t Ty n, trung M hin c trng cc nc c

kh hu nhit i nh : Philippin, o Sumatra, Hawai, Srilanca, Nam M, chu

Phi sn lng Da ca th gii nm 1992 l 10 triu tn, ng th ba sau chui

v xoi. Trong Thi Lan chim 1/5 sn lng Da trn th gii v l nc sn

xut Da nhiu nht. Vit Nam Da l qu ch lc trong ch bin hp xut

khu, tuy nhin sn lng cn rt t so vi cc nc trong vng, Da c trng

ch yu ng bng Sng Hng v ng bng Sng Cu Long.

C nhiu ging Da , c phn thnh ba nhm chnh:

- Nhm Queen (nhm Hong Hu): Da thuc nhm ny c khi lng v

ln trung bnh, mt qu li, chu vn chuyn, tht qu vng m, mi thm c

trng, v ngt. y l nhm Da c phm cht cao nht ang c trng ph bin

nc ta v c gi l Da hoa hay Da khm.

- Nhm Caien (Cayene). Loi ny c khi lng ln qu to c khi n 3 kg.

tht qu mu vng ng, nhiu nc, t thm v t ngt hn Da hoa. Ging ny

c trng nhiu cc nc vng Thi Bnh Dng. Loi ny tuy cht lng

khng cao lm nhng c trng nhiu ch bin do qu to d cgii ho, cho

hiu qu kinh t cao. Hin nay Vit Nam ang c ch trng pht trin ging Da

ny.

- Nhm Spanish (Ty Ban Nha). Da ny c kch thc qu ln hn Da

hoa, nhng nh hn Da Caien. Tht qu vng nht n trng, t thm, chua, nhiu

nc hn Da hoa. Da mt, Da ta trng Vit Nam thuc nhm ny.Ngoi ba nhm Da chnh trn cn c nhm Xan Migel tht qu mu vng

thm ngon

Thi v thu hoch Da thng t thng 3 n thng 8. Da tri v thu

hoch vo khong thng 11 n thng 1, thng hai nm sau .

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Da tri v l kt qu ca vic x l cy Da bng ho cht (Acetylen) kch

thch sinh trng. Khi ngn Da c t 10 l trln ngi ta cho Acetylen dng bt

hoc dung dch vo nn Da . Sau 6 thng chng s ra hoa. Bng cch ny c th

ri v Da c th thu hoch quanh nm. Tuy nhin cht lng ca Da tri v

ca Vit Nam hin cn km so vi Da chnh v.

1.2. Cc bnh thng gp Da .

1.2.1 Bnh thi en: Bnh do loi nm Cerastomella paradoxa. Loi bnh

ny c th gp c trn chui, trn cy ma. Bnh c th bt u t ngoi rung,

pht trin mnh trong qu trnh vn chuyn, c th dn ti mt mt 25%. iu kin

bnh pht trin tt nht l nhit 21-320C v m cao. C th ngn nga

bnh bng cch phun ln qu mi hi dung dch acid Benzoic trong cn, sau em

i bo qun lnh.

1.2.2. Bnh ng nc: Loi nm gy ra bnh ny l Thieliaviopsis

paradoxa. Bnh xut pht t khi vn chuyn. Ch b bnh c mu en xm, ng

nc. phng bnh c th st trng dng c, bao b, kho bo qun bng dung dch

2% n 5% formalin.

1.2.3. Bnh nm xm: Do nm Penicillium fusarium pht trin. Giai on

u tin ca bnh rt kh pht hin. Thot u di lp v Da xut hin nhng

vt bm c mu xm nht n sm. Bnh lan dn ra c qu1.2.4. Bnh thm li: Bnh xut hin ch yu l do ri lon sinh l sinh ho

khi bo qun iu kin khng thch hp, nht l nhit qu lnh (di 9-100C

i vi Da xanh v 4-60C i vi Da chn). Da hng nhanh khi thnh phn kh

quyn ni bo qun thiu oxy qu trnh h hp hiu khi tin trin bnh thng

dn ti h hp ym kh.

1.3. Cc phng php bo qun rau qu ti.

1.3.1. Nguyn l bo qun nguyn liu v sn phm thc phm.

Khi lu tr rau qu ti sau thu hi trong iu kin mi trng 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 ti khi rau qu b h hng di hay ngn ph thuc

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


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mi trng Nguyn nhn trc tip cbn dn ti s h hng thi ra rau qu

l hin tng chn v hin tng nhim bnh .

Chn l mt trong nhng giai on pht trin sinh l bnh thng trong chu

k sinh hc ca mt c th sng. l sinh ra-ln ln-gi-cht. Rau qu ti sau

khi thu hi vn tip tc qu trnh sng nh cn trn cy m, tc l vn tip tc

bin i theo xu hng tt yu ca chu k sinh hc ni trn. Qu trnh chn ca rau

qu ph thuc vo cng h hp, qu trnh h hp ca rau qu sau khi thu hi

xy ra vi cng cng cao th hin tng chn cng nhanh chng xy ra. iu

ng ngha vi thi hn bo qun ca rau qu cng b rt ngn. Thc t cho thy

qu cng chn bao nhiu th cng trnn mm, sc chu ng tc ng chc cng

km l do trong qu trnh chn enzyme protopecitinaza hot ng mnh, phn hu

protopectin (l cht gn cc t bo vi nhau) thnh pectin ho tan, lm yu dn mi

lin kt gia cc t bo thm ch lm cho cc t bo tch hn khi nhau dn n

hin tng chy thnh dch lng. V vy sc khng bnh l ca qu chn km

hn nhiu so vi qu cha chn, l chi tt cho cc loi vi sinh vt pht trin

gy thi ra h hng nhanh chng. Nh vy ko di thi hn bo qun nguyn

liu rau qu trc ht cn thc theo nguyn tc l km hm hot ng sng tc l c

ch cng h hp, t km hm tc chn v ny mm.

S h hng, thi ra ca rau qu sau khi thu hi xy ra ch l do nguynnhn nhim bnh. Trong nhiu trng hp cho dng nguyn liu c hn ch qu

trnh chn n mc tt nht, nhng khi vi sinh vt nht l nm mc c iu kin

hot ng tt th chng s gy bnh dn n thi ra, h hng ng k. Nh vy

nguyn tc th hai, ko di thi hn bo qun rau qu l c ch s hot ng,

sinh trng v pht trin ca vi sinh vt .

Nh vy thc cht ca cc phng php bo qun l siu chnh cc qu

trnh sinh hc xy ra trong rau qu ti cng nh trong vi sinh vt. Khi thay i

iu kin mi trng s tc ng n cc yu t vt l, ho hc dn ti tiu dit hay

c ch, hoc bo ton qu trnh sng ca rau qu.

1.3.2.Cc phng php bo qun rau qu .

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

bo qun thnh ba nhm :


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

sng Bioza (Biosis). Thi gian bo qun rau qu bng phng php ny ph thuc

vo kh nng t khng bnh l v bn ca tng loi qu khi qu trnh sng

ca chng c duy tr bnh thng. Vi phng php bo qun theo nguyn l

ny, rau quc 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 hu thnh phn dinh dng do h hp v gim tn hao khi lng t

nhin do bay hi nc.

- Nhm th hai gm cc phng php da trn nguyn l tm sinh-

Anabioza tc l lm chm, c ch hot ng sng ca nguyn liu v vi sinh

vt. Nh, lm chm thi gian h hng thi ra ca rau qu. Trong thc t,

c ch hot ng sng ca nguyn liu cng nh ca vi sinh vt, cn c s can

thip ca mt s yu t vt l v ho hc. l cc bin php bo qun nhit

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

gim dm, vv c im chung ca cc phng php nay l to ra mi trng

khng thun li cho hot ng ca nguyn liu v vi sinh vt, nhvy km hm

c cng ca cc qu trnh xy ra trong nguyn liu cng nh trong vi sinh

vt.

- Nhm th ba l nhm cac phng php da trn nguyn l phi tim sinh-Abioza. l phng php loi b s sng trong nguyn liu cng nh trong vi

sinh vt. nh ch s sng trong nguyn liu tc l ngn chn mi tc ng dn n

phn gii thnh cc thnh phn ho hc do cc hot ng ca qu trnh sinh hc xy

ra trong t bo sng. Khi khng cn hot ng ( ch bin thnh sn phm),

nguyn liu mt hon ton tnh khang khun v trthnh mi trng pht trin tt

cho vi sinh vt. Trong trng hp ny, mun gi sn phm khi h hng th phi

tiu dit hon ton hoc c ch ti a hot ng sng ca vi sinh vt c trong sn

phm. Nhng phng php bo qun thuc nhm ny l gm: thanh trng nhit,

thanh trng bng dng in cao tn, cc phng php bo qun bng ho cht hoc

bng khng sinh, dng tia phng xa, tia cc tm, v.v

1. Bo qun nhit thng


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iu kin thng c hiu l iu kin nhit v m bnh thng

ca t nhin. Nhit v m t nhin hon ton ph thuc vo s bin ng kh

hu v thi tit.

Nhn chung nhit v m Vit Nam l rt cao (min Bc nhit

trung bnh 23,30C, m trung bnh la 83,5%; min Trung nhit trung bnh l

25,10C, m trung bnh 88,5%; min Nam nhit trung bnh 270C, m

trung bnh l 82%) thch hp cho s pht trin ca a s loi vi sinh vt, nht l nm

mc. Hn na iu kin nhit v m cng rt thun li cho qu trnh h hp

ca rau qu. Ni cch khc th kh hu Vit Nam hon ton bt li cho vic lu gi

rau qu sau khi thu hi. Vi iu kin ny rau qu s chng chn v chng hng.

Tuy nhin trong thc t khi cn thit chng ta vn phi gi nguyn liu rau qu

iu kin bnh thng khng thun li nh vy. l khi cn tp trung rau qu

trc lc phn phi hoc trc khi ch bin cng nghip.

Bo qun iu kin bnh thng hon ton da vo nguyn l bo tn s

sng (Bioza). Thi hn bo qun ph thuc vo c tnh sinh hc ca tng loi rau

qu. Rau qun c k ng tnh cng di v bn cng cao th thi hn bo qun

cng lu. Phn ln cc loi rau qu ch bo qun c iu kin thng trong

khong vi ngy.

Mt trong nhng yu t quan trng gi cht lng ca rau qu khi bo qunnhit thng l thng gi. Thng gi nhm to ra mi trng kh quyn xung

quanh nguyn liu cng thong nh khng gian t do, tc l c nhit , m,

thnh phn kh quyn trong khi nguyn liu khng khc vi t nhin. Ngoi ra rau

qu cng c che chn khi tc ng trc tip ca nh sng hn ch nguyn

nhn lm tng cng h hp.

m bo ch thng gi t nhin cng nh cng bc, khi nguyn liu

cn c xp sao cho c nhng k h khng kh c th lun qua. Rau quc

ng trong st tha xp trn sn thnh l c chiu cao 4-5m. sn kho cn k cao to

rnh ht gi c chiu rng khong 2cm.

2. Bo qun lnh


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Thc phm ni chung, rau qu ni ring c bo qun mi trng c

nhit t 20-240C (gii hn nng lnh) n nhit gn im ng bng ca dch

bo trong nguyn liu gi l bo qun lnh.

Nhit mi trng bo qun cng thp th cng c tc dng c ch cng

ca cc qu trnh sinh l sinh ha xy ra trong rau qu cng nh trong vi sinh vt.

iu m bo ko di thi han bo qun rau qu ti. Nh vy bo qun lnh l

da vo nguyn l tim sinh. Phng php bo qun lnh c dng ph bin trn

th gii hin nay, v y l phng php chc chn nht, t nh hng n cht lng

sn phm nht v c th kt hp vi cc phng php bo qun khc.

Tuy nhin phng php ny c nhc im l hao tn nng lng, tn chi

ph ban u xy kho.

3. Bo qun trong mi trng thay i thnh phn kh quyn

a. Bo qun CA (Controled Atmosphere)

l phng php bo qun rau qu ti trong mi trng kh quyn m

thnh phn khng kh nh O2, CO2c iu chnh (hay c kim sot) khc vi

kh quyn bnh thng. T c gi l phng php bo qun trong kh quyn

c kim sot Controled Atmosphere(CA).

Nh bit, kh O2 v CO2 c tc dng trc tip ln qu trnh sinh l, sinh

ha ca rau qu v t nh hng n thi hn bo qun ca chng. Mt khc tacng bit rng trong kh quyn bnh thng c cha 21% O2, 0.03% CO2, cn li

gn 79% N2 v cc kh khc.

Khi bo qun iu kin thng vi hm lng O2 v CO2 nh trn th chc

chn cng hiu kh s rt cao, n mc rau qu s chn ch vi ngy sau thu hi.

Ngi ta th bo qun rau qu ti trong iu kin h thp nng O2

xung di 21% v tng hm lng CO2. kt qu cho thy thi hn bo qun tng.

l s kt hp hai loi kh trn cng vi iu kin nhit .

Anh hng ca O2 v CO2 ln cc qu trnh sinh l ca rau qu .

Anh hng ca O2: Kh O2 tc dng ha hc vi cc thnh phn c trong

nguyn liu v ng vai tr quan trng nht i vi qu trnh h hp. Anh hng

ca nng O2n thi hn bo qun l rt r rt. Kt qu nghin cu cho thy khi

bo qun to ging Wiliam nhit 00C trong mi trng kh quyn bnh thng


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th thi hn bo qun t 170 ngy, trong khi vi iu kin nhit nh vy,

nhng trong kh cha 3% O2, 0% CO2 thi hn bo qun t 240 ngy.

Khi gim nng O2 xung di 21% cng h hp cng gim dn,

nhng khi gim n mc no s xy ra qu trnh h hp ym kh. i vi

phn ln cc loi rau qu khi nng O2 gim di 2-3% th h hp ym kh bt

u xy ra.

Hm lng O2 gim qu mc cng c th lm cho hm lng Vitamin gim.

Cc loi nm bnh pht trin chm khi gim hm lng O2n 3% v khng c

CO2.

- Anh hng ca CO2: nhiu tc gi nghin cu nh hng ca CO2n

cng h hp ni ring, thi hn bo qun rau qu ti ni chung. Nghin cu

trn to ging Kok Orange Reneta bo qun trong mi trng kh quyn cha 3% O2

v t 0-5% CO2 cho thy cng h hp hu nh khng i. Nhng nu nng

CO2 l 7%, nhit bo qun l 12oC th cng h hp bc chng k. C tc

gi cn cho thy rng, nu nng CO2 qu cao th cng h hp chng nhng

khng gim m cn c th tng. C hin tng l do khi nng CO2 cao chua

ca rau qu tng v CO2 c th cnh bn trong t bo rau qu to thnh axit hu

cv lm ri lon trong mt s phn ng trao i cht.

Phng php iu chnh nng O2 v CO2 trong mi trng bo qun: to nng O2 v CO2 thch hp c th thc hin theo hai phng php t nhin v

nhn to.

- Phng php t nhin da vo qu trnh h hp tiu th O2 v nh ra CO-

2. phng php ny c thc hin khi phng n iu chnh m tng nng O2

v CO2 vn m bo nhiu kin thng. Nng O2 s gim dn v CO2 tng

dn. Phng php ny n gin r tin, dng dng nhng qu trnh iu chnh

ko di.

- iu chnh kh quyn bng phng php nhn to tc l dng kh nitcho

vo phng hoc cho khng kh c rt bt kh O2n nng cho php bng

cch cho tip xc vi Mtan hoc Propan. Phng php ny cho php a nhanh

nng d O2n mc mong mun.


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Ni chung phng php bo qun trong mi trng c kim sot thnh phn

kh quyn cho hiu qu tt, thi hn bo qun di (t 6-9 thng vi to). Trong thi

gian bo qun, cht lng rau qu hu nh khng i. Nhng nht im ln l

phc tp, i hi s ch c bit trong u t xy dng cng nh trong vn hnh

kho bo qun. Tnh n nh ca ch bo qun khng cao, ph thuc khng

nhng vo ging m cn vo thi v, iu kin v a bn pht trin ca nguyn

liu rau qu.

b. Bo qun rau qu ti trong mi trng kh quyn ci bin MAP

(Modified Atmosphere Packaging)

y l phng php bo qun m rau quc ng trong ti mng mng

Polyetylen c tnh thm thu chn lc, mi ti nng t 1-3kg hoc ng trong st

25-35kg c lt mng Polyetylen. Thm ch rau qu cn ng trong container sc

cha 300-1000 kg, c lt bng vt liu tng hp c tnh thm thu chn lc i

vi cc loi kh.

Mc thm thu ca cc loi mng rt khc nhau ph thuc vo loi,

dy ca vt liu l mng. Nu thm thu ca mng cao th rau qu co xu hng

h hp mnh dn n mau chn, mau h hng cn nu mng c d thm km th O2

kh i vo v CO2 kh i ra dn n nng O2 gim, nng CO2 tng lm cho

rau qu h hp ym kh, rau qu mau h hng.Trong qu trnh bo qun do qu trnh h hp hm lng O2 gim, CO2 tng,

hi nc tng v do chch lch hm lng cc cht ny vi mi trng bn ngoi

nn CO2 v hi nc di chuyn ra cn O2 di chuyn vo. Khi t cn bng nng

O2i vo bng nng O2 cn cho qu trnh h hp, nng CO2i ra bng nng

CO2 thi ra do qu trnh h hp.

Cc dng MAP:

- MAP thng : cho rau qu vo ti cht do sau hn kn li. Ti cht

do s hn ch s xm nhp ca O2 t bn ngoi vo v CO2 t bn trong ra. Sau

mt thi gian th hn hp khng kh bn trong t im cn bng.

- MAP chng: Ht khng kh bn trong ti hoc mng cht do ra sau

bm vo hn hp kh c nng CO2 v O2 thch hp .


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- Ht chn khng: ht 1 phn lng khng kh bn trong sau mt thi gian

khng kh bn trong st n im cn bng.

Phng php MAP ngoi bo qun rau qu cn bo qun tht, c, phomt.

Do cc thc phm ny khng c qu trnh h hp nn khng cn O2, hn ch Oxy

ha cc cht dinh dng .

Mt s phng php x l: thi hn bo qun di hn, trc khi bo

qun rau qu c thc x l bng nhit, bng dung dch CaCl2 hoc to mng

sp.

- X l nhit: dng nc nng, dng hi nc nng hoc dng hi nng.

Phng php dng hi nc nng hoc hi nng: x l nhit khng cao nhng

thi gian x l di v d: nhit l 43oC, thi gian gi l 8 gi. Phng php dng

nc nng : x l nhit cao (500C) v thi gian x l l 15 n 30 pht

u im : c ch vi sinh vt, loi b bt mt s loi cn trng, su hoc di,

hn ch Enzyme oxy ha nh Polyphenoloxydaza, hn ch qu thrnh trao i cht

ca rau qu, qu trnh sinh l, sinh ha bn trong rau qu, hn ch s sinh Etylen.

Phng php ny p dng i vi nhn, vi, bng ci xanh.

- X l bng dung dch CaCl2: Nhng rau qu vo dung dch CaCl2 c nng

t 2 -8%. Dung dch ny c tc dng hn ch qu trnh phn hy Clorofil, c ch

c vi sinh vt, c ch qu trnh trao i cht bn trong rau qu, hn ch s mmca rau qu.

- To mng sp: to lp mng sp bao xung quanh rau qu bng mt s loi

ch phm nh Waxol, CMC, Protexan. Tc dng ca lp mng sp l hn ch s

mt nc, to ra mc thm kh CO2 v O2 ph hp v trn mt s cht khng vi

sinh vt sau khi to mng c tc dng c ch vi sinh vt.

Cch dng: Ha ch phm cht to mng vo nc ri nhng rau qu vo

dung dch, em kh ri bo qun.

4. Bo qun bng ha cht.

Hin nay trong thc t bo qun v ch bin thc phm ni chung, bo qun

rau qu ti ni ring ngi ta vn thng xuyn s dng mt s loi ha cht

nhng liu lng khc nhau nhm ko di thi gian bo qun thc phm. i vi

rau qu ti, mt s loi ha cht c kh nng c ch sinh trng, tc l lm chm


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qu trnh pht trin sinh l, c th l qu trnh ny mm ca rau qu. Loi ha cht

khc li c kh nng thm thu su vo mng t bo ca vi sinh vt, tc dng vi

protein ca cht nguyn sinh, lm t lit hot ng sng ca t bo, v do vi sinh

vt ngng hot ng. ko di thi hn bo qun rau qu ti ch yu l kh

nng tiu dit cc loi vi sinh vt ca cc loi ha cht.

Thc t cho thy, khi s dng ha cht ph hp, rau qu c th bo qun

c di ngy ngay cnhit bnh thng. Tuy nhin nu kt hp x l ha

cht vi bo qun lnh th hiu tng ln nhiu.

Nhc im ca vic s dng ha cht nh l cht bo qun l ch c th

lm bin i phn no cht lng ca rau qu, to mi v khng tt. Quan trng

hn, c th gy hi cho sc khe con ngi . Tc hi ca ha cht i vi sc khe

c th xy ra tc khc hoc lu di. Tc l c th gy ngc ngay sau khi cth

nhn mt lng ha cht vt qu mc chu ng ca con ngi. Tc hi lu di l

khi c th tch ly dn dn mt cht no c kh nng trthnh nhn t sinh ra

mt s bnh nguy him. Nh vy chng ta cn thn trng khi quyt nh dng ha

cht x l bo qun rau qu ti.

Ha cht c s dng bo qun thc phm ni chung, rau qu ti ni

ring cn phi p ng nhng yu cu sau: dit c vi sinh vt liu lng thp

di mc nguy him cho con ngi; khng tc dng vi cc thnh phn trong thc

phm dn ti bin i mu sc, mi v lm gim cht lng sn phm . Khng

tc dng vi vt liu lm bao b hoc dng c thit b cng ngh; d tch khi sn

phm khi cn s dng.

Tuy nhin t khi c loi ha cht no li c th tha mn tt c nhng yu

cu trn, cho nn khi s dng cn tm hiu dy tnh cht ha hc, l hc, mc

c hi, tc dng ca tng loi ha cht la chn cho tng i tng c th,

nhm m bo ng thi cht lng bo qun v an ton thc phm.

Ha cht dng bo qun rau qu gm hai nhm:+ Nhm th nht gm cc loi ha cht co kh nng chng ny mm hoc

tit mm. i din ca nhm ny l M-1, MH4O, ru nonilic, v.v

M-1 thc cht l este ca axit -Naptylaxetic v ru metylic. N tn ti

dng tinh khit khng tan trong nc, tan trong este, benzen, ru v mt s dung

mi hu ckhc. Trong thc t M-1 c th dng dng bt mn 3,5% trong bt t


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st. Hn hp bt M-1 thng dc rc ln khoai ty ngn chn ny mm. Dng

M-1 dng bt co u im so vi dng ha tan l trnh c nh hng xu ca

dung mi n b mt ca rau qu ti. Mt khc dung mi t hn nhiu ln so vi

bt t st.

Kh nng khng nm, khng khun ca M-1 yu, khng c kh nng ditmm.

MH4O l hydrazit ca axit malic. Loi thuc ny c tc dng hn ch sinh

trng ca cc loi rau qu nh khoai ty, c rt, hnh v mt s rau qu khc.

Thng dng dng dung dch mui natri 0,25%. Ngi ta phun dung dch MH4O

ln cy ngoi ng trc khi thu hi 3 n 4 tun vi liu lng 1000 lt cho mt

hecta.

Ru Nonilic (Nonanol) c dng dit mm khoai ty. Khi khoai ty

ny mm cn dng loi ha cht ny phun vo l mm ho. Nonanol tn ti dng

hi nn rt chng bay hi. V th, c hiu qu cn phun thuc nhiu ln.

+ Nhm th hai gm cc loi ha cht c kh nng dit vi sinh vt.

Cc loi vi sinh vt gy bnh c th b tiu dit bi cc ha cht sau:

- Pentaclonitrobenzen (KP2) c phun ln bp ci trc khi bo qun dit

nm. Loi ny c tnh c cao nn cn cn thn khi thao tc cng nh khi s dng

sn phm. an ton, trc khi s dng phi bc lp v ngoi trnh ngc.

- Topxin M (Tiophanatmetyl-C12H24N4O4S2) l loi ch phm c dng btmu t st, kh tan trong nc, tan trong cc dung mi hu c nh: Axeton,

Clorofooc, Metanol, Topxin M dc sn xut Nht nhng nay c s dng

rng ri khp ton th gii. Cht ny c tc dng dit nm mnh ngay cnng

thp; thi gian tc dng nhanh, ko di; c th dit c nhiu loi nm; khng c

hi.

Cch dng: ha dung dch 0,1% sau em nhng cam hay chui vo to

mt lp bn ngoi ri ly ra.

Ngoi cc loi ha cht nu, gn y trn th trng th gii con xut hin

nhiu ch phm mi c tc dng chng nm nh: Mertect 90, Benlat, NF44,

MAO7, v.v Mi cht c tc dng ring tng loi qu.

5. Bo qun rau qu bng mng Chitosan (C6H13NO5)


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Chitosan c cu trc t nhin ca v tm, mai cua , chitin- sau khi sau khi

tch chit c deacetyl ha vi kim c s cho chitosan. Chitosan l mt polyme

sinh hc c hot tnh cao, a dng d ha hp vi c th sinh hc, c tnh khng

nm v kh nng t phn hy; khi to mng mng c tinh bn thm, chng nm

nn c ng dng trong nhiu lnh vc kinh t, k thut khc nhau nh: y hc

(dng cha bng, chm sc vt thng, cha bnh bo ph) cng nghip dt,

giy, m phm, bo v mi trng, v.v. trong k ngh bo qun rau qu ti,

nhiu tc gi thnh cng trong vic s dng Chitosan bo qun da chut, du

ty, h tiu, c chua

Cch s dng Chitosan bo qun mt s loi qu ti: Trc tin ngi

ta to ra dung dch Chitosan bng cch ha tan chitosan nguyn liu trong mi

trng acit acetic long. C th b sung mt s cht ph gia tng tnh khng nm

hoc tng cng tnh to mng ca dung dch Chitosan.

Qu ti sau khi thu hi c phn loi, lm sch ri nhng vo dung dch

Chitosan chun b sn trong thi gian thch hp, sau c vt ra lm kh

to mng Chitosan. Mng mng Chitosan to thnh trn b mt qu c tc dng

c ch h hp, gi li kh cacbonic, gim thiu lng ethylen (vn c tc dng kch

thch qu trnh chn trong qu) v km hm qu trnh bin mu ca qu trong khi

bo qun, vn chuyn i tiu th, gi cho ch tiu cm quan ca qu chn c boqun tt hn.

6. Bo qun bng phng php chiu x.

Nguyn l ca phng php bo qun bng chiu x l: khi chiu bc x vo

sn phm th mt mt vi sinh vt s b tiu dit, mt khc i vi rau qu ti

qu trnh sinh l, sinh ha c th bc ch lm chm qu trnh chn ca rau qu v

hn ch hin tng ny mm. Ngoi ra n cn tiu dit cn trng hay ng vt gy

hi c rau qu ti, nhvy ko di thi hn bo qun .

Cc loi tia bc xc s dng trong bo qun thc phm gm:

- Tia m cc v tia . y l dng in t c tc ln, gn bng tc nh

sng. Cc loi tia ny c xuyn thu km hn tia v tia X, nhng thi gian tiu

dit vi sinh vt th ngn hn (ch cn vi giy n vi chc giy trong khi cc tia

khc cn n vi chc pht)


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- Tia Rngen (X) v tia . Hai tia ny thc cht l sng in t ngn thu

c khi bn ph in t. Tia X c xuyn thu cao d s dng nhng h s c

ch thp t 0,1 n 10%, thi gian dit vi sinh vt di t 10 n 30 pht.

Tia Rngen (X) v tia khc nhau ch: Tia X thu c bng phng php

nhn to khi cho in t bn ph vo mt vt i m cc. Cn tia thu c do s

phn giai cc cht ng v phng x.

Trong bo qun thc phm thng dng tia v n c cc u im: c

thc phm hay rau qu hp th mt cch d dng; c mc xuyn thu cao; c

tnh n nh v r tin.

Trn thc t tia c sinh ra t ngun Co60 v Cs137. khi dng tia th n

c tnh an ton v nu mun sinh ra phng x cm ng th nng lng phng x phi

ln hn 5MeV trong khi nng lng phng x ln nht ca tia thu c t

Co60

1,3 MeV.

Liu lng chiu x: l nng lng phng xc hp thu bi mt kilogam

vt cht .

Liu lng phng xc o bng Rad hay Gy (Grey), 1Rad=10-2Gy. Thc

t liu lng chiu xmc n v l Mrad hay KGy.

+ Anh hng ca chiu xn vi sinh vt:

Kh nng tiu dit vi sinh vt ca tia bc x ph thuc vo cc yu t sau:S lng vi sinh vt ban u. S lng vi sinh vt cng nhiu th liu lng

chiu x phi cng cao.

Loi vi sinh vt: Mi loi vi sinh vt c kh nng chu tc ng ca tia bc

xn mt liu lng gii hn no . Vt qu gii hn ny chng s b tiu dit.

Loi bn chiu x nht l vi trng Koc v nha bo ca cc chng Bacillus,

Clostridium, Cl. Botulinum ch b tiu dit liu lng chiu x 5Mrad khi s

lng ca chng l 1012 t bo /cm2.

Cu to ca vi sinh vt: Loi vi sinh vt c cu to cng n gin sc chu

tc ng ca tia bc x cng cao, v ngc li cu to t bo t bo cng phc tp

th vi sinh vt cng nhy cm vi tia bc x.

Dng tn ti ca vi sinh vt. Cng loi vi sinh vt nhng vi sinh vt dng nha

bo chu c liu lng chiu x ln gp 2-3 ln so vi dng mm.


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Ngoi nhng yu t nu trn, yu t nhit , hm lng O2, thnh phn ha

hc ca sn phm, cng nh hng ng kn tnh bn chiu x ca vi sinh vt.

Nhiu nghin cu cho thy s cht ca vi sinh vt v liu lng chiu x c

mi tng quan logarit

c biu th bng biu thc.

R=D10log (N0/Nn)

Trong :

R l liu lng chiu xo bng Kgy

N0, Nn l s lng vi sinh vt trc v sau khi chiu x,

D10 l bn chiu xc c trng bng liu lng chiu x cn

thit lm gim s lng vi sinh vt xung 10 ln, 1 chu k logarit.

+Anh hng i vi thnh phn ha hc ca rau qu.

Gluxit

Cc cht gluxit ni chung kh bn chiu x

Nu liu lng chiu x cao th c s hnh thnh nhm COOH, bin

glucoza t trng thi ng sang trng thi axit.

liu lng 10MRad, xenluloza b bin i, protopectin thy phn thnh

pectin ha tan, tinh bt chuyn thnh dextrin v mantoza, Ni tm li khi chiu

x vi liu lng cao cc cht thuc nhm gluxit c xu hng phn gii t dngphc tp sang dng n gin hn, thm ch c th xy ra cc phn ng melanoidin,

polyme ha, Nhng liu lng thng s dng cho sn phm thc phm t

1Mrad n 8MRad th nhng bin i trn khng nhiu so vi gia nhit.

Cc Vitamin

Cc loi Vitamin l i tng kh nhy cm vi tia bc x. Mc ph hy

Vitamin do chiu x tng t nh trng hp ta dng nhit hay x l nhit.

Vitamin C c th b phn hy ti 50%. Trong dung dch nc Vitamin C b

oxy ha thnh dng dehydroascorbic acid, v do d phc hi tr li trng thi

acid ascorbic.


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Vitamin A khng b phn hy liu lng 0,85MRad, cn liu lng

11,25MRad s mt khong 50%.

Vitamin E b phn hy n 60% liu lng bc x 3 MRad. Nu mi

trng khng c O2 th ni hu nh khng b phn hy do vy ngi ta cho rau qu

vo bao gi ht chn khng ri mi chiu x.

Vitamin K c th khng b phn hy liu lng bc xn 5 MRad.

Cc loi vitamin trong cng mt hn hp c th l cht bo v ca nhau. V

d khi chiu x hn hp vitamin C, v vitamin PP, vitamin C b phn hy thn

vitamin PP trong khi nu tn ti ring l th Vitamin C b phn hy nhiu hn. iu

ny chng t vitamin PP trthnh cht bo v vitamin C

Cc thnh phn lipit v protit

Tc dng ca chiu x ln lipit v protit c th lm thay i r rt mi, v ca

sn phm. Nguyn nhn chnh l do lipit b oxy ha, protein b phn gii to thnh

cc hp cht c mi v kh chu. Tuy nhin s bin i lipit v protit khi chiu x

khng ln hn khi gia nhit.

Enzyme

Cc emzyme tng i bn vi s chiu x. Emzyme peroxydase catalase

khng b mt hot tnh ngay c khi liu lng bc xn 8 MRad. Ni cch khc l

thnh phn rt bn chiu x khng th dng tia bc x v hot chng trong snphm thc phm.

Do nh hng ca tia bc xn hu ht cc thnh phn ha hc nn dn ti

s bin i chung v trng thi ca sn phm. Rau qu c th b mm do chiu x,

liu lng cng cao th mm cng tng, mu sc ca sn phm c th khng gi

c trng thi t nhin thm ch cn b mt mu. Mi v ca mt s loi rau qu

nh mng ty trnn chua, kh chu.

Liu lng chiu x cho cc loi rau qu

Nhiu nghin cu s dng chiu x ko di thi hn bo qun cho rau qu

ti. S bin i cht lng v thi hn bo qun ph thuc vo liu lng phng

x. Cng trn mt loi qu nhng liu lng x l thp c th chng nhng khng

ko di c thi hn bo qun, khng ngn chn c bnh m cn bin i xu

hn so vi mu khng x l. Ngc li nu liu lng qu cao c th ngn c vi


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sinh vt gy bnh nhng li nh hng n cht lng cm quan ca sn phm: qu

c th b mm, b mt mu, v vy phi tm ra mt liu lng chiu x thch hp

sao cho va ko di c thi hn bo qun va gic cht lng sn phm.

Liu lng chiu x dng cho mi loi rau qu mt khc, ph thuc vo c tnh

ca loi . Khng phi tt c cc loi rau quu c th bo qun c bng chiu

x. Thng thng vi loi rau qu c pH > 4,5 th phi chiu x vi liu lng

khong 45 MRad, cn loi co pH < 4,5 th dng liu lng thp hn 13 MRad

u im ca phng php chiu x l: n gin, nhanh chng v thun tin;

khng li d lng nu dng liu lng hp l; qu trnh chiu x c th d dng

iu khin theo mun v gi thnh thp.

7. Bo qun rau qu bng Ozon

c to thnh khi c s phng in, l hp cht khng bn d b phn hy

thnh O2 va [O] nguyn t. Mc tiu dit vi sinh vt ca Ozon mnh gp 1,5 ln

so vn Clorine c bit Ozon c tc dng rt mnh i vi vi khun Ecoli.

Ozon c th khi nhng mi hi khng mong mun v tnh oxy ha kh

ca n. Ozon cn c tc dng loi b Etylen.

C2H4 + 2O3 = 2CO2 + 2H2

1.3.3. Phng php bo qu Da ang c p dng

Sau khi thu hi Da c la chn theo chn, kch thc. Loi b nhngqu bm dp, sy st. Da bo qun c hoa, cung di khong 2cm.

Kho bo qun cn c sat trng bng formalin cha 36% formaldehyd vi

liu lng 0,25 lit/m2 sn. Nhit lc phun l 16-180C, m 95% n 97%. Phun

xong ng kn kho trong 24 gi. C th xng kho bng lu hunh vi liu lng

10g/m3. Khi xng cng ng kn phng trong 24 gi.

Trc khi bo qun, Da c thc xng bng Metilbrom vi liu lng

50 n 80g/m3 kho trong 30 pht, sau xp vo bao b v cho vo kho bo qun.

Da xanh c bo qun trong phng lnh nhit 10-110C, m 85-90%.

Khng bo qun Da xanh nhit thp hn 70C v li Da d b thm v mt

kh nng chn.

Da xanh c x l bng ha cht 2,4DT nng 0,05% v bc sp hoc

nhng Topxin M 0,2% c th bo qun nhit 20-250C c hai tun.


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Ngoi vic x l Da bng ha cht, ngi ta con dng mng PE chuyn

dng bc Da ri bo qun. Bng cch ny c th ko di thi gian bo qun ln

gp i.

Da chn bo qun 4,5-70C, m 85-90%. Khng bo qun di 40C.

2.TNG QUAN V CHITOSAN

2.1. Ngun gc ca chitosan

Chitin phn b v tn ti kh phong ph trong t nhin, chng c cng

vt v thc vt. Song trong ng vt thy sn c bit l trong lp v ca cc ng

vt gip xc nh tm, cua, ghe th hm lng chitin chim kh cao so vi trng

lng kh.

Chitin l mt polysaccaride c m khng c hi, c khi lng phn t

ln. Cu trc Chitin l mt tp hp cc phn t lin kt vi nhau bi cc cu nihydrogen v hnh thnh mt mng cc si t nhiu c t chc.

Chitosan l mt dn xut ca Chitin, n l mt polymer hu cph bin

trong t nhin sau cellulose v chng c to ra trung bnh 20g trong 1nm/m2 b

mt tri t.

2.2. Cu trc phn tca Chitosan

Chitosan l mt polymer hu cc cu trc tuyn tnh t cc n v D-

Glucosamin lin kt vi nhau bng lin kt 1,4 Glucozit.

Cng thc cu to ca Chitosan:

Cng thc phn t: (C6H11O4N)n

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

2.3. Tnh cht ca Chitosan

* Tnh cht sinh hc

HH

H

HH

H

HH

H

HH

H

HH

H

OHOH OH

NH2NH2NH2

CH2OH CH2OH CH2OH

n


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- Chitosan c ngun gc t nhin, khng c, an ton cho ngi khi s dng

lm thc phm, dc phm, c tnh ha hp sinh hc cao i vi s th, c kh

nng t phn hy sinh hc.

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

m, khng nm, khng khun vi nhiu chng loi khc nhau, kch thch tng sinh

t bo ngi v ng vt, c kh nng nui dng t bo trong iu kin ngho

dinh dng.

* Tnh cht ha hc

- Chitosan l cht rn, xp, nh, dng bt c mu trng ng, dng vy c

mu trng trong hay hi vng, khng mi v.

- Chitosan c tnh kim nh, khng ha tan trong nc, tan trong mi trng

acid long (pH=6,6) to dung dch keo dng, nh m keo Chitosan khng b kt

ta khi c mt ca mt ion kim loi nng nh Pb3+, Hg2+.

- Chitosan kt hp vi aldehyt trong iu kin thch hp hnh thnh gel,

y l cs by t bo, enzyme.

- Chitosan phn ng vi acid c to mui kh tan, cho phn ng mu tm

khi tc dng vi iod v acid sunfuric, do c th dng phn ng ny nh tinh

Chitosan.2.4. ng dng ca Chitin-Chitosan

Chitin khng c cng dng g ng k khi nguyn dng v tnh tan km,

tuy nhin khi chuyn sang cc dn xut nh: glucosamin, chitosan, th n li

c ng dng rng ri trong nhiu lnh vc khc nhau nh:

Trong nng nghip

Chitosan c dng nh mt thnh phn chnh trong thuc phng tr nng

bnh (o n, kh vn,), dng lm thuc kch thch sinh trng cy trng nh:

la, cy cng nghip, cy n qu, cy cnh, Chitosan khng c hi, gi tc dng

lu trn l, cy, lm tng ny mm cu ht, tng vic to dp lc trn l, tng kh

nng m r, thc y qu trnh ra hoa kt qu v lm tng nng sut thu hoc ca

cy trng


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C th ch to mng chitosan dng trong thc phm nh sau: Ha tan

chitosan trong acid acetic 1,5% to thnh dung dch chitosan 6%, nh o u, lc

dung dch b cn v cht khng tan. Ly dung dch va lc pha vi hai phn

Glycerine v hai phn dung dch acetat km 20% to thnh dung dch long, do.

em hn hp va trn un cch thy 40-500C, thi gian 20-30 pht khi no thy

dung dch trong sut l c. Dng hn hp trn trng thnh nhng mng mng

Chitosan. Mng mong Chitosan ny c th thay th polyetylen bao bc thc

phm cao cp.

* Trong cng nghip dt:

Nhvo tnh khng tan trong nc ca Chitosan lm cho n c kh nng

h ln vi lm vi chng m, ngoi tnh khng thm nc vi si sau khi x l cn

c kh nng chng bn la, cch nhit, chu nng tt, chng mc.

Chitosan c th dng sn xut bao b chng m, dng c bo h lao ng

trong sn xut cng nh trong nghin cu.

Chitosan c dng h, cnh hnh in hoa, u im l n c th thay i

c h tinh bt lm cho vi hoa, t, sbn hn, chu c s c xt, b mt

bng p, chu c acid v kim nh.

* Trong cng nghip giy:

Chitosan lm tng bn cho giy, ch cn thm trng lng bng 1%trng lng ca giy s lm sc do dai ca giy, gim thi gian cn thit rt

nc ra khi bt, lm gia tng s lng cht si trong giy. Theo c tnh ca

nh sn xut giy c th tit kim c 90% nng lng tiu th v by gih

khng cn nh bt rt nc ra na. Loi giy c ch to bng Chitin d in

hn loi giy binh thng v kh rch hn khi bt. Vi c tnh ny Chitin c

thc dng trong vic ch to t lt cho tr em, khn giy v bao giy gi hng.

* Trong m phm:

Dng chitosan nh mt cht ph gia lm kem thoa mt, lm thuc lm

mm da, lm tng kh nng ha hp sinh hc gia da v kem thuc, ch to ra kem

lt da mt v bn cht Chitosan l cnh d dng trn biu b da bi nhng nm

NH4+

tha, c cc nh ha hc gn vi nhng tia cc tm hay nhng cht gi

nc. Chitosan trthnh cu ni gia hot cht ca kem v da.


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Trong y hc

Chitosan c ng dng nhiu trong lnh vc y t nh: dng cha bng,

chm sc vt thng, dng lm ch khu, lm da nhn to.

Chitosan c nghin cu trong lnh vc y hc Vit Nam lm thuc

polysan 2% cha bng v vt thng mau lnh, khng li so, khng c tc

dng ph, khng gy dng, c b y t dit v cp giy php lu hnh trong ton

quc.

T chitosan sn xut glucosamincos kh nng thc tin thuc khng sinh t

v c th dng lm nguyn liu nui vi trng v ch thuc.

Trong k ngh v bo ch dc phm, chitosan c th lm cht ph gia nh

lm t n, t dc dnh, cht to mng vin nang mm v cng v cht mang sinh

hc dn thuc

Theo nghin cu dng Chitosan lm t dc dnh trong mt s cng thc

vin c dc cht d b tc ng bi cc ion kim loi nng ca Nguyn Th Ngc

T, Nguyn Phc Khu v Nguyn Th Thanh Hi cho kt qu chitosan lm t dc

nh trn Vitamin C tt ngang PVP (dung dch cn polyvinyl pirovidin) v l tc

nhn kha ion kim loi nng tng t EDTA_Na2 (Etylen Diamin Tetra

Natriacetat). Chitosan c kh nng dng thay th hn hp PVP, EDTA_Na2 trong t

bo thuc vin v c kh nng to mng phim trn vin, thch hp bao cc vinc thnh phn trung tnh hoc acid nh.

Khoa Dc trng i Hc Y Dc Thnh Ph H Ch Minh nghin cu

thuc cha vim lot d dy t trng t ch phm ca Chitosan nh: Gel Chiosan,

Gel Chitin, Gel Chitosan v Al(OH)3.

Chitosan v dn xut ca n dng lm thuc cha bnh nh: thuc h

cholesterol trong mu, thuc chng bo ph vi hm lng chitosan 2%, cha cc

vt thng. Ngoi ra ngi ta con sn xut c ch khu t nhin bng chitin.

Mt cng ty M dng Chitosan to vt dng ht nc v ch khu t

tiu. Cc bc sM khm ph rng c th gip mu ng nhanh hn v ch

to ra thu knh tip xc khng c tnh th lc t Chitosan gip qu trnh lin so

ca th gic.

ng dng trong cng ngh sinh hc


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* Dng chitosan trong cnh t bo

Chitin-Chitosan l mt cht mang ph hp cho s cnh enzyme t bo.

Enzyme cnh t bo l mt cht xc tc sinh hc hot ng trong mt khng

gian linh hot. Enzyme cnh cho php m ra vic s dng rng ri enzyme

trong cng nghip, trong y hc, khoa hc phn tch Enzyme cnh c s

dng lu di, khng cn thay i cht xc tc, nht l trong cng ngh lm sch

nc, lm trong nc qu, s dng enzyme cnh rt thun li v t hiu qu

cao.

c im quan trng ca cc nguyn liu c s dng lm cht mang

enzyme l din tch b mt trn mt n v th tch hay trng lng phi rng,

khng b phn gii, khng tan, bn vng vi cc yu t ha hc, gi r, d kim.

Trong cc loi polymer th chitin v chitosan tha mn yu cu trn.

Phng php cnh enzyme bao gm: Enzyme c dnh trn cht mang

bng lin kt hp ph hay lin kt tnh in (lin kt ion), hoc lin kt vi trong

li gel, lin kt ngang (GrossDingking). Enzyme c c nh trong Chitosan

bng lin kt hp ph hay lin kt ngang qua cu ni cht trung gian nh:

Glutaraldehyt hoc c khi enzyme b vi trong li gel to thnh lin kt ngang

gia Chitosan v Glutaraldehyt.

Qua nhiu nghin cu cho thy Chitosan c cc c im sau:- Chitosan l mt nguyn liu do, linh hot, n c th cnh enzyme bng

cc hp phn gin, bng hp ph dng li gel hay bng lin kt ion qua nhn t

chc nng trung gian hoc dng th vi.

- S lin kt ion NH4+

ca chitosan vi cc ion m t do khc trn enzyme,

l nhn t hnh thnh lin kt hp ph hay ion.

- Hiu sut cnh theo phng php hp ph c khuynh hng cao hn

theo lin kt ion, cho php thc hin trong iu kin nh nhng.

- Khi so snh vi cc cht mang khc th Chitosan c kh nng chc ng

lng protein 10-30mg/gram Chitosan.

* Cc ng dng khc ca Chitosan


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mt nc v tn tht cht dinh dng ca c khi cp ng v sau khi r ng. c

bit, khi nu c c bo qun bng Chitosan th thy Chitosan khng lm thay

i mi v ca sn phm. i vi thy sn kh nh: c kh, c mc, th tin hnh

pha dung dch chitosan 2% trong dung dch acid acetic 1,5% sau nhng c kh

v mc kh vo dung dch c pha, lm kh bng cch sy nhit 300C c

qut gi. Sn phm thu c c th bo qun tt nhit bnh thng. Ty theo

m ca c v mc kh m sn phm c thi gian bo qun khc nhau, m

cng thp th thi gian bo qun cng di. Vi m 26 - 30%, c kh bo qun

c 83 ngy, mc kh 85 ngy; cn m 41- 45% th c kh gic 17 ngy,

mc kh gic 19 ngy.

-Nguyn Trng Bch (i Hc Thy Sn) nghin cu mng bao gi thc

phm t dung dch Chitosan nng 3,5% phi trn ph liu l dung dch h tinh

bt nng 3% vi t l phi trn Chitosan/ tinh bt l 70/30. ng dng mng ny

bo qun tht b v c thu nhit 0 - 50C th thy mng ny c kh nng khng

khun tt v c kh nng gi nc ca thc phm trong, qu trnh bo qun lnh th

thy kt qu l tht vn gic mu sc trong sut ba ngy bo qun.

- Tc gi Nguyn Ngc T v cc cng s nghin cu dng mng

chitosan bo qun hoa qu ti th thy thi gian bo qun rau qu ko di hn

so vi hoa qu chc bo qun lnh. Kim tra s lng vi sinh vt th thy hoaqu bo qun bng mng chitosan c kh nng khng khun tt.

Ngoi nhng nghin cu trn, nhiu tc gi cng khc cng c nhng nghin

cu dng mng chitosan bo qun tri cy nh: s dng Chitosan trong bo qun

cam Vit Nam ca nhm tc gi L Don Din v cc cng s v vi ti ny

h c th bo qun cam ln n 42 ngy m trng thi ca cam vn t mc thng

phm; hay ti ca sinh vin Phm Hng Ngc Thy bo qun xoi sau thu hoch

bng Chitosan v ph gia c nh gi cao.

3.2. Nghin cu ngoi nc

Mt s nh khoa hc ngi Nga nh Krasavtsev, Maslova, Degtyareva,

Bycoda, Noudga nghin cu ng dng mng Chitosan lm bao gi bo qun

c v cc sn phm t c. Ngi ta dng Chitosan c chit rt t cc ngun ph

liu thy sn khc nhau nh tm, cua, gh ln lt lm mng mng bao gi c th


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thy mng Chitosan chit rt t v tm c dy, bn ko, n hi cao nht.

Mng chitosan gip cho sn phm gi nc rt tt v gic cc c tnh t nhin

ca sn phm.

Attaya Kungsuwan, Bodin Ittipong v Suwalee Chandrkrachang nghin

cu s dng dung dch Chitosan (ha tan 5g chitosan trong 500ml acid acetic 1%)

lm mng bao gi bo qun c th thy thi gian bo qun ko di ti 2 thng trong

khi c khng c bo qun bng Chitosan th thi gian bo qun ch ko di ti a

l 1 thng trong cng mt iu kin bo qun.

Mt nhm cc nh khoa hc trc thuc mt s trng i hc Canada nh

Blaise Ouattara, Ronal E. Simard, Gabriel Piette, Andre Begin, Richard A. Holley

nghin cu dng mng Chitosan bao gi tht th c thc chc s pht trin

ca cc vi sinh vt gy thi ra nhm ko di thi gian bo qun tht v cc sn

phm t tht.

Ngoi ra c mt s tc gi nghin cu dng mng Chitosan bo qun

tri cy nh: Yueming Jiang, Jianrong Li, Weibo Jiang ca trng i hc Zhejiang

Gongshang Trung Quc dng mng chitosan bo qun vi; hay ti nghin

cu dng mng chitosan bo qun xoi ca nhm tc gi P.C. Srinivasa, Revathy

Baskaran, M.N. Tharanathan ca phng ha sinh v dinh dng ca trung tm

nghin cu cng ngh thc phm An .4. GII THIU V MNG CHITOSAN

Mng mng chitosan c vai tr ht sc quan trng, n c dng bo

qun thc phm s hn ch kh nng mt nc cng nh kh nng chng li s pht

trin ca vi sinh vt trong qu trnh bo qun.

Chitosan c tc dng lm bt ng cc t bo vi trng ng vt hoc thc vt

hay cc enzyme. l tnh khng khun, khng nm (chitosan b sung vo thc n

gia sc s kch thch s pht trin ca vi khun Bifidobacterium trong rut, vi khun

ny to ra enzyme lactase cho s tiu ha v cn trs sinh trng ca cc vi sinh

vt khc). Cch khng khun ca Chitosan vn cha chc chn, tuy nhin mt vi

suy on tin cy xut kin cho rng:

- Chitosan s ly i t cc vi sinh vt ny cc ion quan trng nh Cu2+. Nh

vy vi sinh vt s cht do mt cn bng cc ion quan trng.


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- Ngn chn ph hoi chc nng ca mng t bo.

- Gy ra s tng hp ca polyelectrolyte vi polyme mang tnh cht acid trn

b mt t bo vi khun.

Nh vy vic dng mng Chitosan bao bc quanh thc phm c th ko di

thi gian bo qun, gim s thi hng nhkh nng khng khun, khng nm ca

n.

Mng mng chitosan c thng dng rng ri trong ngnh cng nghip bao

gi, bao b thc phm. V n c th thay th polyetylen sn xut giy bng kn

bao bc thc phm cao cp. c bit mng mng chitosan cn c kh nng lm cht

bo qun thc phm v thc phm ti sng. Ngoi ra ngi ta s dng Chitosan

lm mng mng ph ln tri cy tng thi gian bo qun.

Mt khc, hin nay nhim mi trng l vn bc xc ang c quan

tm, mt trong nhng ngun cht thi l bao b lm t PE, PVC,.m hng

ngy chng ta thi ra mi trng. Loi cht thi ny thi gian phn hu rt lu

ng thi x l n cng ht sc phc to. Chnh v vy vic nghin cu v ng

dng mng chitosan dng trong cng nghip bao gi l ht sc cn thit v c

ngha v cng to ln.


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CHNG 2: I TNG V PHNG PHP NGHIN CU

1. I TNG NGHIN CU

Da l mt loi qu nhit i c tn khoa hc l Ananas comusus, y l

loi quc s dng nhiu n ti v ch bin. Bo qun Da phc v cho ni

tiu v xut khu hin nay ang l vn bc xc nc ta.

Vic p dng cc phng php bo qun hin i rt t tin cha th tin

hnh trong iu kin hin nay ca nc ta. Phng php dng ho cht bo qun

Da tuy c th p dng c nhng d lng ca ho cht c th gy c hi i

vi ngi tiu dng.

Chnh v vy vic tin hnh nghin cu s dng chitosan- mt nguyn liu

tch chit t v tm, mai cua vn khng c hi vi ngi v khng gy nhim

mi trng- lm mng bao bo qun Da ti trong iu kin Vit Nam. Vic

s dng chitosan bo qun tri cy s ko di thi gian bo qun v gim gi thnh

vn chuyn em li hiu qu kinh t cao hn.

Da nghin cu trong ti l loi Da Queen (khm) c trng huyn

Bnh Chnh Thnh Ph H Ch Minh, vn chuyn n ni tiu th bng xe ti trong

thi gian t 2 n 3 ngy ; cn Chitosan c sn xut ti Trung Tm Ch Bin Ca

Trng i Hc Thu Sn gm hai loi: Chitosan deacetyl cao HDD (95%) vChitosan deacetyl thp LDD (75%).

2. NI DUNG NGHIN CU

- Tm hiu v tnh cht ca chitosan

- Xc nh loi v nng chitosan bo qun da

- Xc nh iu kin bo qun (nhit , m,)

- xut quy trnh cng ngh bo qun Da sau thu hoch


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3. PHNG PHP NGHIN CU

3.1. S b tr th nghim

Nguyn liu da

kim tra X l tp cht

dung dich Chitosan

0% 0.5% 1% 1.5% 2%

Bo qun

Nhit phng nhit lnh (ngn di t lnh)

Kim tra cht lng DaNguyn liu

Da c thu hi khi cc mt Da mht hoc c t 1 n 3 hng

mt ng mu vng. Sau khi thu hi Da c chn la theo chn kch thc.

Loi b nhng qu bm dp sy st. Da bo qun c hoa, cung di khong

2cm sau c x l to mng chitosan.

Xl

Ra Da bng nc sch nhm loi b bi bn tp cht v mt phn vi sinh

vt trn b mt. Sau kh t nhin.

Kim tra

Xc nh mu sc, trng thi ban u ca Da . Xc nh trng lng ban u ca qu.

Xc nh cc thnh phn ha hc c trong nguyn liu ban u:

- Xc nh hm lng ng tng s

- Xc nh hm lng axit ton phn

Dung dch Chitosan


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Chun b dung dch chitosan

Dng Chitosan kh ha tan trong dung dch acid axetic 1% ln lt thu

c cc dung dch Chitosan c nng 0.5%, 1%, 1.5%, 2%

Nhng Da vo trong dung dch Chitosan chun b to lp mng

mng trn b mt ri kh t nhin trong khng kh.

Bo qun

Da sau khi to mng trong dung dch chitosan sau cho vo ti PE c c

l (mi ti 6 l) ri chia thnh hai phn:

Phn th nht bo qun iu kin nhit phng.

Phn th hai bo qun nhit lnh (ngn di t lnh).

Cng vic kim tra phn tch mu c thc hin 10 ngy mt ln. Khi mu

bt u h hng th kt thc qu trnh bo qun

3.2. Cc phng php phn tch

3.2.1. Xc nh ch tiu cm quan (mu sc, trng thi) ca Da theo

phng php cho im cm quan

Tin hnh xy dng bng im chun cm quan theo phng php cho im.

phng php cho im ny s dng h 10 im xy dng trn mt thang thng

nht c 6 bc t 0 n 5. Su bc nh gi tng ng vi ni dung m t bng sau:

Ch tiu cm quanim cha c

trng lng Mu sc Trng thi

5 V Da cn xanh hay c 1 n 3 mt

ng vng

Da cn ti, cng khng

c bm dp xy st

4 V Da cn xanh 1 s mt ng vng Da cn cng, t ti

3 V Da c mu xanh - vng Da hi b mm km ti

2 V Da vng gn nh hon ton, n

hon ton

Da mm, kh cung Da

ho

1 V Da vng sm bt u h hng Da mm, v ho, bt u


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xut hin mc xanh

0 V chuyn sang sm Da mm, b ng mt phn

Hai ch tiu mu sc v trng thi c mc quan trng ngang nhau nn hs quan trng ca ch tiu mu sc bng h s quan trng ca ch tiu trng thi v

bng 1.

3.2.2 Xc nh trng lng qu bng cn ng h ( sai lch 510g)

Da sau khi thu hoch dc la chn theo kch thc, mu sc, loi b cc

qu bi hng, nhim mc, bm dp, sau ra sch, kh t nhin. Tip tin

hnh nhng Da vo cc dung dch chitosan, ri kh t nhin. Dng cn xc

nh trng lng ca qu. Tip tc tin hnh theo di s thay i trng lng qu

trong qu trnh bo qun theo cng thc:

3.2.3. Xc nh hm lng acid tng stheo phng php chun bng

NaOH tiu chun vi ch th l phenolphtalein- nh ngha: acid ton phn bao gm tt c cc loi acid c trong thc

phm, ch yu l nhng acid hu c(acid citric, acid acetic, acid malic,) m cc

acid ny c thnh lng bng dung dch kim tiu chun.

- Nguyn l: Dng dung dch kim tiu chun trung ho ht cc acid c

trong mu vi ch th l phenolphtalein.

- Tin hnh xc nh :

+ Chun b mu:Cn P(g) mu them nghin nh, dng nc ct trung tnh chit ht acid

c trong mu th.

+ Chun :

Ly vo cc thu tinh V1 ml dung dch th v cho vi git ch th

phenolphtalein 1%.

: l t l hao ht trng lng qu.: l trng lng qu ban u.: l trng lng qu sau thi gian bo qun.

g

G1

G2

%1001

21

G

GGg

=

Trong


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em cc i chun bng NaOH 0,1N n khi dung dch chuyn sang mu

hng bn th dng. c th tch NaOH 0,1N tiu tn, gi s l V2 ml.

+ Tnh kt qu

Hm lng acid c trong quc tnh theo cnh thc:

Trong :

V2 : l s ml NaOH 0,1 N dng chun

K : biu th s gam acid tng ng vi 1 ml NaOH 0,1 N. i vi tri cy th

quy trnh v acid citric K= 0,0064 hoc acid malic K= 0,00667

F : h s pha long mu tng cng

P : khi lng mu th.

X l s liu bng chng trnh Microsoft Excel.CHNG 3 KT QU NGHIN CU V THO LUN

1. KT QUNGHIN CU SDNG CC LOI CHITOSANBO QUN

1.1. Loi Chitosan Deacetyl cao (HDD).

1.1.1 Anh hng ca cc nng Chitosan n ch tiu cm quan ca

Da trong qu trnh bo qun nhit thng v nhit lnh (6 80

C)Bng 1: Anh hng ca cc nng chitosan n ch tiu cm quan ca Da

trong qu trnh bo qun nhit thngim c trng lng

Nng chitosan, %Thi gian boqun (ngy)

Hi ngcm quan 0 (/c) 0,5 1 1,5 2

1 10 10 10 10 10

2 10 10 10 10 10

3 10 10 10 10 10

4 10 10 10 10 10

Tp 1

5 10 10 10 10 10

TB 10 10 10 10 10

1 7 7 8 8 8

2 6 7 7 7 8

Tp 10

3 6 6 7 8 8

PFVKX

100... 2=

(%)


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4 6 7 7 8 8

5 6 7 7 7 8

TB 6,2 6,8 7,2 7,6 8

1 5 6 7 7 7

2 5 5 6 6 8

3 4 5 6 7 7

4 4 6 6 7 7

Tp15

5 5 6 6 6 7

TB 4,6 5,6 6,2 6,6 7,2


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Bng 2 : Anh hng ca cc nng chitosan n ch tiu cm quan ca Datrong qu trnh bo qun nhit lnh 6-8 oC

im c trng lng

Nng chitosan, %

Thi gian

bo qun

(ngy)

Hi ng

cm quan 0 (/c) 0,5 1 1,5 2

1 10 10 10 10 10

2 10 10 10 10 10

3 10 10 10 10 10

4 10 10 10 10 10

Tl 1

5 10 10 10 10 10

TB 10 10 10 10 10

1 9 8 9 10 10

2 8 9 9 9 10

3 8 9 9 9 9

4 8 8 9 9 9

Tl 10

5 8 8 8 9 9

TB 8,2 8,4 8,8 9,2 9,4

1 8 7 8 9 9

2 8 8 9 9 9

3 7 8 8 8 8

4 7 8 8 8 9

Tl 20

5 7 7 8 8 9

TB 7,4 7,6 8,2 8,4 8,8

1 7 6 7 8 8

2 7 7 8 8 8

3 6 6 8 7 8

4 6 7 7 8 8

Tl 30

5 6 6 7 8 8TB 6,4 6,4 7,4 7,8 8


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Hnh 1 : o th bieu dien s anh hng cua cac nong o chitosan en ch tieucam quan cua Da nhiet o phong va nhiet o lanh trong qua trnh bao quan

0

24

6810

12

0 (/c) 0,5 1 1,5 2

Nong o chitosan, %

iemcamquantrungbnh

Tp 1Tp 10Tp15Tl 1Tl 10Tl 20Tl 30

Trong :

Tp1 : bo qun iu kin thng trong thi gian 1 ngy



Tl 1 : bo qun iu kin lnh trong thi gian 1 ngy

Tl 10 : bo qun iu kin lnh trong thi gian 10 ngyTl 20 : bo qun iu kin lnh trong thi gian 20 ngy

Tl 30 : bo qun iu kin lnh trong thi gian 30 ngy

Nhn xt v tho lun:

T hnh 1 cho thy: Mu i chng theo thi gian bo qun nhit phng

mu sc, trng thi, mi v ca qu gim r rt. Thi gian u s bit i t nhng

sang ngy th 7 tri th s bin i v mu sc, trng thi, mi v cng nhanh v

n ngy th 15 th mu i chng bt u h. Trong khi cc mu c x l

chitosan th mu sc, trng thi, mi v c gim nhng t hn so vi mu i chng

v tc cng chm hn. iu ny c th gii thch khi to mng bao, chitosan s

hn ch qu trnh chn ca qu cng nh hn chc s bay hi nc, do trng

thi ca qu vn cn cng, ti. Mng bao chitosan cng dy th hiu qu hn ch

qu trnh chn v bay hi nc cng tng. iu ny c chng tmu chitosan


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nng 0,5% so vi mu i chng khng c s khc bit ln, cn mu x l nng

2% th do mng to dy hn ch s trong i cht gia qu v mi trng nn

sau khong 15 ngy qu con cng, ti. Tuy nhin nu ko di thi gian th mu

2% s b ng nc, ci Da s ben v s qu din ra ln man ym kh. Kt qu

cui cng l qu s b h nhanh hn so Da c x l nng 1% v 1,5%.

Nu ta kt hp bo qun Da nhit lnh (6 100C) th ch tiu cm

quan ca Da cng tt ng thi thi gian bo qun cng c ko di. C th khi

bo qun Da nhit phng th sau 15 ngy qui chng bt u h, trong khi

bo qun nhit lnh th sau 30 ngy qu vn cha h, sau ta ra ngoi

4 ngy nhit thng th qu mi c du hiu h hng.

1.1.2. Anh hng ca cc nng Chitosan n t lhao ht trong lng

ca Da trong qu trnh bo qun nhit phng v nhit lnh (6 80C)

Bng 3: nh hng ca cc nng Chitosan n t l hao ht trong lng ca Da

trong qu trnh bo qun nhit phng v nhit lnh (6 80C)

T l hao ht trng lng, %

Nng chitosan, %

Thi gian

bo qun

(ngy) Nhit 0 (/c) 0,5 1 1,5 2

10 15,38 13,53 11,47 8,4 7,25

15

Nhit

phng 23,77 21,3 17,21 16,03 12,32

10 5,17 4,12 3,28 3,06 1,9

20 11,21 7,21 7,37 6,12 4,76

30

Nhit

lnh

(6-8oC) 15,52 11,34 10,65 9,18 6,67

o th bieu dien s anh hng cua cac nong o chitosan en ty le haotrong lng cua Da nhiet o phong va nhiet o lanh trong qua trnh bao quan

05

10

15

20

25

0,5 1 1,5 2Nong o Chitosan (%)

Tylehaohuttronglng%

Tp 10Tp 15Tl 10Tl 20Tl 30

Hnh 2 :

0(C)


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Nhn xt v tho lun:

Trong qu trnh bo qun, Da vn c s hao ht khi lng v trong qu

Da xy ra qu trnh h hp, trao i cht, cc thnh phn nh glucid, acid,

glucozit s tham gia qu trnh h hp v sinh nng lng lm tn hao khi lng

ca qu. ng thi qu trnh bay hi nc ca Da cng lm cho qu hao ht trng

lng.

T hnh 2 ta thy: Sau thi gian bo qun mu i chng c s hao ht trng

lng v tc ln hn so vi cc mu c x l bng chitosan. Khi bo qun

nhit thng th sau 10 ngy t l hao ht trng lng ca mu i chng l

15,38%, trong khi cc mu c x l bng chitosan th s hao ht trng lng

ca qu gim c th cc nng 0,5%; 1%; 1,5%; 2% c t l hao ht trng

lng ln lt l 13,53%; 11,47%; 8,4%; 7,25%. Sau 15 ngy th t l hao ht trng

lng tip tc tng nhng tc c xu hng gim dn

Tuy nhin khi kt hp vi bo qun nhit thp (6 100C) th t l v tc

hao ht trng lng ca Da xy ra t hn so vi khi bo qun nhit

thng v nhit thp cc qu trnh trao i cht, bay hi nc ca qu b hn

ch. Sau 10 ngy mu i chng c t l hao ht trng lng l 5,17%; trong khi

cc mu bo qun bng chitosan cc nng 0,5%; 1%; 1,5%; 2% t l hao ht

trng lng ln lt l 4,12%; 3,28%; 3,06%; 1,9%. Sau khi bo qun 30 ngy tht l hao ht trng lng mu i chng l 15,52%, cn cc mu c mng bao

chitosan ln lt l 11,34%; 10,65%; 9,18%; 6,67%. Nh vy vi cc mu x l

chitosan nng cng cao th mng bao cng dy v t l hao ht trng lng cng

gim bi v mng bao cng dy th n s hn ch qu trnh bay hi nc cng nh

qu trnh h hp ca qu

1.1.3. nh hng ca cc nng Chitosan n hm lng acid tng ca

Da trong qu trnh bo qun nhit phng v nhit lnh (6 80C).

Bng 4 : nh hng ca cc nng Chitosan n hm lng acid tng ca Da

trong qu trnh bo qun nhit phng v nhit lnh (6 80C).

Hm lng axit tng s, %

Nng chitosan, %

Thi gian

bo qun

(ngy) Nhit 0 (/c) 0,5 1 1,5 2


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Tp 1 0,7500 0,7500 0,7500 0,7500 0,7500

Tp 10 0,5184 0,5376 0,6144 0,6336 0,6720

Tp 15

Nhit

phng 0,5280 0,4608 0,5568 0,5760 0,5952

Tl 1 0,7500 0,7500 0,7500 0,7500 0,7500

Tl 10 0,6144 0,6528 0,6912 0,7104 0,7296

Tl 20 0,4704 0,5088 0,5184 0,5376 0,6240

Tl 30

Nhit

lnh

(6-8 oC) 0,5568 0,4864 0,4992 0,5184 0,5856

Hnh 3 : Anh hng cua cac nong o Chitosan en ham lng Acid tong so cuatrong qua trnh bao quan nhiet o phong va nhiet o lanh (6-8)

0,000

0,200

0,400

0,600

0,800

0 0,5 1 1,5 2

Nong o Chitosan, %

Haml

ngAcidtongso,%

TpTp

Tp

Tl

Tl

Tl

Tl

Nhn xt v tho lun:

Da sau khi t chn thu hoch th trong qu trnh bo qun Da tip tc

xy ra mt s bin i v sinh l, sinh ho lm mu sc, mi v ca Da tt hn gi

l qu trnh chn tip ca qu, cng chnh v th m hm lng acid trong qu gim

dn theo thi gian bo qun. Tuy nhin khi qu bt u h th hm lng acid trong

qu bt u tng li, l do l trong quang xy ra qu trnh ln men lactic nn

trong qu hm lung acid tng ln

Theo hnh 3, ta thy mu i chng so vi nhng mu c x l bng

chitosan th gim hm lng acid din ra nhanh hn ngha l qu trnh chn tip


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ca Da din ra nhanh hn. C th sau 10 ngy bo qun nhit thng, t hm

lng acid ban u l 0,75%, mu i chng gim xung cn 0,5184%, trong khi

cc mu c x l chitosan nng 0,5%; 1%; 1,5%; 2% th hm lng acid gim

ln lt l 0,5376%; 0,6144%; 0,6336%; 0,6720%. Nhng ngy bo qun tip theo

hm lng acid cc mu bo qun bng chitosan tip tc gim, nhng mu i

chng li tng iu ny chng t qui chng ang b h hng. Nh vy mng

bao chitosan khng nhng lm chm qu trnh chn ca qu m n cn c tc dng

hn ch hot ng ca cc loi nm mc, nm men.

T hnh 3 cng cho ta thy rng: khi kt hp bo qun Da nhit lnh

(6- 100C) th hm lng acid gim t hn ng thi thi gian bo qun cng c

ko di v chnh yu t nhit cng l tc nhn hn ch qu trnh chn ca qu v

hn ch hot ng ca vi sinh vt. C th nu sau 10 ngy bo qun nhit

phng vi mu i chng hm lng gim xung cn 0,5184% th nhit lnh

hm lng acid chn 0,6144%; v mu i chng nhit thng ch 15 ngy

th qu bt u h, nhng khi bo qun nhit lnh th thi gian bo qun ko

di n 30 ngy nhit thp v 4 tip theo ngy nhit thng.


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1.1.4 Anh hng ca cc nng Chitosan n hm lng ng tng s

ca Da trong qu trnh bo qun nhit thng v nhit lnh (6 80C).

Bng 5: nh hng ca cc nng Chitosan n hm lng ng tng s ca Da

trong qu trnh bo qun nhit thng v nhit lnh (6 80C).

Hm lng ng tng s, %

Nng chitosan, %

Thi gian

bo qun

(ngy) Nhit 0 (/c) 0,5 1 1,5 2

Tp 1 8,0 8,0 8,0 8,0 8,0

Tp 10 14,5 13,2 13,0 12,0 11,3

Tp 15

Nhit

phng 13,6 12,9 12,5 11,7 10,4

Tl 1 8,0 8,0 8,0 8,0 8,0

Tl 10 12,3 11,7 10,8 10,7 10,2

Tl 20 13,2 13,7 12,2 12,5 11,8

Tl 30

Nhit

lnh

(6-8oC) 12,0 12,5 13,0 13,2 12,5

Hnh 4 : Anh hng cua cac nong o Chitosan en ham lng ng tong so

Da trong qua trnh bao quan nhiet o phong va nhiet o lanh (6-8)

0,02,04,06,08,0

10,012,014,0

16,0

0 (/c) 0,5 1 1,5 2Nong o Chitosan %

Hamlngng

Tp 1Tp 10Tp 15Tl 1Tl 10Tl 20Tl 30

Nhn xt v tho lun:


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Theo thi gian bo qun, hm lng ng tng s trong Da tip tc tng

l do:

Tinh bt thu phn Glucose + Maltose + Dextrin + Fructose

Hemixenlulosethu phn

Xenlulose + Pentosan

Pentosan chuyn thnh Pentose m bn cht ca Pentose l ng.

Theo hnh trn ta thy hm lng ng trong Da tng theo thi gian bo

qun. mu i chng ta thy hm lng ng tng nhanh hn cc mu c x l

bng chitosan. C th khi bo qun nhit thng th sau 10 ngy mu i

chng hm lng ng t 8% tng ln 14,5%, trong khi cc mu x l to mng

bao chitosan nng 0,5%; 1%; 1,5%; 2% ln lt l 13,2%; 13%; 12%; 11,3% .

Nhng sau 15 ngy hm lng ng trong mu i chng v cc mu c nng

0,5%; 1%; 1,5% gim, tuy nhin tc gim khng ging nhau mu x l nng

chitosan thp gim nhanh hn mu x l nng cao. Cn mu x l nng

chitosan 2% th hm lng ng tip tc gim n 12,5%. S gim hm lng

ng ca cc mu trong thi gian cui qu trnh bo qun l do ng tham gia

vo mt s qu trnh phn ng ln men, phn ng sinh ho to ra cc sn phm

trung gian.

Khi kt hp bo qun qunhit thp th hm lng ng tng ln

chm hn so vi khi bo qun nhit thng. V d nh sau 10 ngy bo qun nhit thng hm lng ng t 8% tng ln 14,5% ; cn nhit thp n

ch tng ln 12,3%. Nh vy yu t nhit thp cng lm gim cc qu trnh thu

phn tinh bt, hemixenlulose, pentosan thnh ng nn hm lng ng tng t

hn so vi khi bo qun nhit thng.


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1.2. Loi Chitosan Deacetyl thp (LDD)

1.2.1 nh hng ca cc nng Chitosan n ch tiu cm quan ca

Da trong qu trnh bo qun nhit thng v nhit lnh (6 - 80C)

Bng 6,7 :nh hng ca cc nng Chitosan n ch tiu cm quan ca Da

trong qu trnh bo qun nhit thng v nhit lnh (6 - 80C)

im c trng lng

Nng chitosan, %

Thi gian

bo qun

(ngy)

Hi ng

cm quan

0 (/c) 0,5 1 1,5 2

1 10 10 10 10 10

2 10 10 10 10 10

3 10 10 10 10 10

4 10 10 10 10 10

Tp 1 5 10 10 10 10 10

TB 10 10 10 10 10

1 5 6 7 7 8

2 6 6 7 7 8

3 5 5 6 7 7

4 5 6 6 7 7

Tp 10 5 6 6 7 6 7

TB 5,4 5,8 6,6 6,8 7,4

1 4 5 5 6 6

2 5 5 6 6 6

3 4 5 6 6 6

4 4 5 6 6 6

Tp15 5 5 6 6 5 6

TB 4,4 5,2 5,8 5,8 6


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Hnh 5: nh hng ca cc nng chitosan n ch tiu cm quan ca Da trong

qu trnh bo qun iu kin thng v iu kin lnh (6 80C)

Nhn xt v tho lun

T hnh v cho ta thy theo thi gian bo qun mu sc, trng thi ca qu

gim dn v cng ging nh bo qun bng chitosan HDD mu i chng c mu

sc trng thi gim nhanh hn so vi cc mu c x l bng chitosan. C thnhit

phng sau 10 ngy im cm quan ca mu i chng t 10 gim xung cn 5,4

trong khi im cm quan ca cc mu c x l bng chitosan cc nng 0,5%;

1%; 1,5%; 2% ln lt l 5,8; 6,6; 6,8; 7,4. n ngy th 15 th mu i chng

h nhiu im cm quan l 4,4 trong khi cc mu c x l chitosan c im cm

quan ln lt l 5,2; 5,8; 5,8; 5,8; 6

Cn khi kt hp vi bo qun lnh th mu sc v trng thi ca qu tt hn

v thi gian bo qun cng di hn. C th l sau 10 ngy bo qun nhit

thng th im cm quan ca mu i chng l 5,4 v Da ch bo qun dc

trong 15 ngy; trong khi nu bo qun nhit thp (6-80C) th im cm quan

ca mu i chng l 8,2 v bo qun ko di 30 ngy nhit 6 80C sau

mang ra ngoi nhit thng 3 ngy th Da mi c du hiu h hng.


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1.1.2. nh hng ca cc nng Chitosan n t lhao ht trong lng

ca Da trong qu trnh bo qun nhit phng v nhit lnh (6 80C)

T l hao ht trng lng, %

Nng chitosan, %

Thi gian

bo qun(ngy)

Nhit 0 (/c) 0,5 1 1,5 2

Tp 10

Tp 15

Nhit

phng

19,39

27,76

16,67

25,40

15,04

22,12

14,52

21,16

9,65

15,54

Tl 10

Tl 20

Tl 30

Nhit

lnh

(6-8oC)

6,08

13,04

17,33

4,96

10,64

14,89

3,76

8,27

12,78

2,96

8,14

12,59

2,14

5,00

8,57

Nhn xt v tho lun

Trong qu trnh bo qun trng lng ca Da cng b gim iu ny cng

c gii thch l do qu trnh bay hi nc, qu trnh h hp nn mt s cht trong

qu b gim dn n trng lng ca qu cng gim. T th ta thy mu i

chng c hao ht trng lng ln v tc nhanh hn so vi cc mu bo qun

bng chitosan c th nh s liu bng trn.

Hnh 6 : o th bieu dien s anh hng cua cac nong o chitosan en ty lehao hut trong lng cua Da trong qua trnh bao quan Nhiet o phongva nhiet o lanh (6-8)

0

510

15

20

25

30

0 (/c) 0,5 1 1,5 2Nong o chitosan, %

Tyleh

aohuttrong

l

ng,%

Tp 10

Tp 15Tl 10

Tl 20Tl 30


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Khi kt hp bo qun nhit thp th t l hao ht trng lng ca qu

gim r rt, v d nh khi bo qun nhit thng sau 10 ngy t l hao ht

trng lng mu i chng l 19,39% cn mu bo qun nhit lnh (6 80C)

th t l hao ht l 6,08%. Nhng mu c x l bng chitosan th t l gim v

gim ph thuc vo mng bao chitosan dy hay mng c th nh mt s t l

hao ht trng lng nh bng trn, mng bao cng dy th t l hao ht cng gim

iu ny c gii thch phn bo qun Da bng chitosam HDD

1.2.3 nh hng ca cc nng Chitosan n hm lng acid ca Da

trong qu trnh bo qun nhit thng v nhit lnh (6 - 80C)

Bng 8 : nh hng ca cc nng Chitosan n hm lng acid ca Da trong

qu trnh bo qun nhit thng v nhit lnh (6 - 80C)

Hm lng acid tng s, %

Nng chitosan, %

Thi gian

bo qun

(ngy)

Nhit

0 (/c) 0,5 1 1,5 2

Tp 1 Nhit 0,7500 0,7500 0,7500 0,7500 0,7500

Tp 10 phng 0,4800 0,4992 0,5184 0,5856 0,6240

Tp 15 0,5287 0,5284 0,5088 0,5280 0,5299

Tl 1 0,7500 0,7500 0,7500 0,7500 0,7500

Tl 10 0,5568 0,6048 0,6240 0,6336 0,6816

Tl 20 0,4512 0,4992 0,5280 0,5664 0,6432

Tl 30

Nhit

lnh

(6-8oC)

0,5280 0,5088 0,4992 0,5184 0,5664


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Hnh 7 : Anh hng cua cac nong o Chitosan en ham lng acid tong cuaDa trong qua trnh bao quan nhiet o phong va nhiet o lanh ( 6 8C).

0,0000

0,2000

0,4000

0,6000

0,8000

0 (/c) 0,5 1 1,5 2

Nong o chitosan, %

Haml

ngacidtongso%

Tp 1Tp 10Tp 15

Tl 1Tl 10Tl 20

Tl 30

Nhn xt v tho lun

Trong qu trnh bo qun, hm lng acid ca Da gim dn nhng n thi

gian cui qu trnh bo qun th hm lng acid trong qu bt u tng ln v khi

qu c du hiu h hng mt s phn ng ln men bt u din ra lm cho hm

lng acid tng s trong qu tng ln. mu i chng hm lng acid tng sgim nhanh hn so vi cc mu c x l bng chitosan v ch sau khong hn 20

ngy th hm lng acid mu i chng bt u tng li v ta cng thy rng mu

x l chitosan nng cng cao th hm lng gim cng t; cn khi bo qun

nhit thp (6 80C) th hm lng acid gim chm hn so vi bo qun nhit

thng c th s liu nh bng 8.


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1.2.4 nh hng ca cc nng Chitosan n hm lng ng tng s

ca Da trong qu trnh bo qun nhit thng v nhit lnh (6 80C).

Bng 9 : nh hng ca cc nng Chitosan n hm lng ng tng s ca

Da trong qu trnh bo qun nhit thng v nhit lnh (6 80C).

Hm lng ng tng s, %

Nng chitosan, %

Thi gian

bo qun

(ngy)

Nhit

0 (/c) 0,5 1 1,5 2

Tp 1 8,0 8,0 8,0 8,0 8,0

Tp 10 13,7 13,3 12,8 12,5 11,7

Tp 15

Nhit

phng 12,0 12,6 13,5 13,3 13,2

Tl 1 8,0 8,0 8,0 8,0 8,0Tl 10 12,8 11,9 10,6 10,3 9,6

Tl 20 13,6 12,7 11,5 11,4 10,8

Tl 30

Nhit lnh

(6-8oC)

12,5 13,5 12,8 12,7 11,8

Nhn xt v tho lun

Theo s cho ta thy, thi gian u qu trnh bo qun hm lng ng

tng s trong Da tip tc tng nhng cui qu trnh bo qun th hm lng

ng trong qu li gim. iu ny chng t trong quang din ra cc phn ng

sinh l sinh ho, quang chn dn sau n giai on phn gii v cui cng qu

Hnh 8 : Anh hng cua cac nong o Chitosan en ham lng ng tong so

cua Da trong qua trnh bao quan nhiet o thng va nhiet o lanh ( 6 80

0,0

5,0

10,0

15,0

0 (/c) 0,5 1 1,5 2Nong o chitosan

Hamlngng

Tp 1Tp 10

Tp 15Tl 1Tl 10

Tl 20Tl 30


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s b hng. Vi mu i chng th hm lng ng tng nhanh hn cc mu bo

qun bng chitosan nhng thi gian din ra s phn gii ng cng nhanh hn.

Trong khi tc tng hm lng ng cc mu c x l bng chitosan chm

v thi gian din ra giai on phn gii ng cng di hn. Do thi gian bo

qun cng c ko diKhi ta kt hp vi bo qun lnh th thy hm lng ng trong qu tng

chm hn so vi bo qun nhit thng. C c iu ny l do yu t nhit

thp n nh hng ng kn cc qu trnh sinh l sinh ho din ra trong qu

khi bo qun, ng thi yu t nhit thp cng vi chitosan c ch hot ng ca

vi sinh vt nhvy m thi gian bo qun Da c ko di hn

** Nhn xt chung

Qua kt qu nghin cu s dng hai loi chitosan bo qun Da cho ta

thy:

- Vi loi chitosan deacetyl cao (HDD) cho kt qu tt hn so vi loi

chitosan deacetyl thp (LDD). C th nh khi s dng chitosan HDD bo qun

th t l hao ht trng lng, hm lng acid tng s gim, hm lng ng tng

s v thi gian bo qun di hn so vi chitosan LDD. iu ny chng t Chitosan

deacetyl cao th khi to mng s kn hn so vi chitosan deacetyl thp do n s

hn ch qu trnh chn ca qu tt hn so vi chitosan deacetyl thp

- T cc thng s nghin cu trn cho thy rng nng dung dch chitosan

0,5% c hiu lc bo qun km. Da chn nhanh, t l hao ht trng lng cao hn

so vi cc nng khc, ng thi cc thnh phn ho hc nh hm lng ng,

hm lng acid cng gim nhanh, thi gian bo qun ngn. Cc nng chitosan

1%; 1,5% c hiu qu tng ng nhau v c th dng bo qu Da . Cn

chitosan nng 2% c tc dng bo qun r rt, tuy nhin nng ny kh pha v

do to mng dy nn thi gian bo qun khng c di v mng dy qu thiu oxy

nn d ln ln men ym kh dn n qu nhanh h hng v mu sc ca qu sau khi

bo qun cng khng c pI.4. Quy trnh cng ngh sdng chitosan bo qun Da sau thu hoch

Da nguyn

La chn , ra loi b qu khng t


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Lm kh t nhin

To mng chitosan (nhng)

Lm kh t nhin

Bao gi

Bo qun lnh(6 80C)

Thuyt minh quy trnh:

- Nguyn liu: sau khi thu hoch nguyn liu c la chn, theo mu sc

trng thi, loi b nhng qu hng, nhim mc, bm dp. Sau ra Da bngnc sch mc ch l loi b bi bn v mt phn vi sinh vt bm trn Da , ri

kh t nhin ti nhit phng hoc c th dng qut mau kh

- To mng chitosan: Nhng Da vo dung dch chitosan pha sn vi cc

nng khc nhau. Thi gian nhng mi qu l 1,5 2 pht.

- Sau khi nhng xong, Da kh nhit phng

- Bao gi: cho mi qu Da vo mt ti PE c c 6 l thng kh sau

a vo bo qun lnh (6 80C)

KT LUN V KIN NGH1. KT LUN

T cc kt qu trn c thi n kt lun sau:

C th s dng dung dch chitosan HDD nng 1% x l to mng bao

bo qun Da sau khi thu hoch. Mng bao chitosan c tc dng lm chm qu

trnh chn ca qu, ngn chn s mt nc v c kh nng khng khun.

Thi gian bo qun Da bng chitosan HDD nng 1% theo nhit

nh sau:

- nhit thng l 15 ngy (t l h hng 15%)

- nhit lnh (6 80C) l 30 ngy v 4 ngy nhit thng(t l h

hng 20%)

Trong khi nu khng dng mng bao chitosan th :

- nhit thng Da bo qun c 15 ngy nhng t l h hng l 60%


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- nhit lnh (6 - 80C) bo qun c 30 ngy t l h hng 35%

Hiu qu kinh t:

Gi ca 1kg Da hin nay mua ti vn trung bnh l 500 ng.

Chi ph bo qun i vi mu 20 qu (trng lng 1,2kg/qu)

- Khi lng Da : 24kg (12000 ng)

- Chi ph chitosan: 10000 ng

- Chi ph acid acetic: 400 ng

- Chi ph cho bao b: 1000 ng

- Chi phin bo qun lnh 15000 ng

- Tng chi ph : 38400 ng

Vy chi ph bo qun khng dng chitosan cho mt kg da l 1125 ng/kg

Nu dng chitosan bo qun l:1600 ng/kg

- T l thi hng ca Da khng bo qun chitosan nhit lnh l 35%

(l 100kg cn li 65kg)

- T l thi hng ca Da bo qun chitosan HDD 1% nhit lnh l 5%

(l 100kg cn li 95kg)

Nh vy trong mt l c 100kg Da nu bo qun bng dung dch chitosan

s hiu qu hn khi khng dng dung dch bo qun l 30kg. v nu xt tnh hiu

qu kinh t ta c th tnh nh sau:

Gi chnh lch gia bo qun chitosan v khng bo qun chitosn l 475 ng

Nu khng bo qun bng chitosan th t l hao ht c th ln 35% (35kg

trong l 100kg) tc l ta mt ht 39375 ng.

Nu bo qun bng chitosan th c th tit kim c 30% (30 kg), nhng

ch cn tng thm mt khong chi ph l 16625 ng, v cht lng v cm quan

cng nhng v gi tr dinh dng cng tt hn, ta c th bn gi cao hn.

Nh vy bo qun bng chitosan s mang li hiu qu kinh t hn.

2. XUT KIN:- Trong Da hm lng Vitamin C khong 40mg%, nhng do kinh ph cn

gp nhiu kh khn cng nh thi gian c hn nn trong qu trnh thc hin ti

em cha kim tra bin i hm lng vitamin trong Da sut qu trnh bo

qun. Do vy nhng cn nghin cu su hn v s bin i hm lng Vitamin C

trong Da khi bo qun


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- Cn nghin cu nhiu hn nhng ng dng ca chitosan trong cc lnh vc

khc nh : trong y hc, trong cng ngh sinh hc, trong cng ngh thc phm, x l

nc thi, .

- Nhin cu dng chitosan to ra mt loi bao b mi c kh nng t phn

hu nhm hn ch nhim mi trng.

- Cn nghin cu cng ngh sn xut chitosan c deacetyl cao c th

xut khu ra th trng nc ngoi, nng cao hiu qu kinh t trong sn xut chitin

chitosan.


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TI LIU THAM KHO

TI LIU TING VIT

1. H Vn Thuyt, Trn Quang Bnh. Bo qun rau qu ti v bn chphm ti

bn ln thnht, NXB Nng Nghip H Ni 2002.

2. Minh Phng, ng Vn Hp. Gio trnh phn tch kim nghim thc phm

thu sn, Trng i Hc Thu Sn Nha Trang, 1997.

3. PGS Trn Minh Tm, Bo qun v chbin nng sn sau thu hoch, NXB Nng

Nghip, H Ni 2000.

4. GS. TS. L Don Din v cc cng s, Nghin cu Sdng chitosan trong bo

qun cam Vit Nam. NXB Nng Nghip H Ni 2002.

5. Phm Hng Ngc Thu. n tt nghip Nghin cu bo qun Xoi sau thu

hoch bng chitosan v ph gia, nm 2004.

TI LIU TING ANH

1. Fereidoon Shahidi, Janak Kamil Vidana Arachchi and You Jin Jeon. Food

application of chitin and Chitiosans. Trends in food science anh technology 10

(1999).

2. Yueming Jiany, Jianrong Li Weibojiang. Effects af chitosan coating on shelf

life of cold stored litchi fruit at ambient temperature. (School of food science

China Agricultural University 14/2004.

3. P.C. Srini Vasa, Revathy Baskaran, M.N. Ramesh, K.V. Harish Prashanth, R.N.

Tharanatham. Storage Studies of mango Packed using biodegradable Chitosan film.

Eur Food Res Technol(2002) Published online : 22/10/2002.

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