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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
Tp10 : bo qun iu kin thng trong thi gian 10 ngy
Tp15 : bo qun iu kin thng trong thi gian 15 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
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