Cnsx Tra Den

7/31/2019 Cnsx Tra Den

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BCNG THNG

TRNG I HC CNG NGHIP THC PHM TP.HCM

KHOA CNG NGH THC PHM

B Mn: CNG NGH CH BIN TR, C PH, CA CAO

GVHD: Th.S NGUYN TH CC

TP.HCM 9/2011


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Mn: CNCB tr, c ph GVHD: Nguyn Th Cc

Tiu lun: Thnh phn ha hc ca tr v k thut ch bin 2

DANH SCH NHM 01

H v Tn MSSV Lp

L Th Hu 3005090211 09CDTP1

Nguyn Th Dim My 3005090325 09CDTP2

Nguyn Th Kim L 3005090302 09CDTP3


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MU

Txa n nay, ch mt loi thc ung quen thuc i vi mi ngi, c bit l

i vi ngi ng. Ch c s dng trn ton th gii, v c xem l mt loi thc

ung mang tnh ton cu. Cng vi s pht trin khoa hc k thut, nhiu cng trnh

nghin cu chng minh li ch ca ch. Bn cnh chc nng gii kht, ch c tc dng

sinh l rt r rt i vi sc khe con ngi. Thnh phn caffein v mt s alkaloid khc

trong ch c tc dng kch thch h thn kinh trung ng, vi no lm cho tinh thn

minh mn, gim mt nhc sau khi lao ng. Ch cn c tc dng phng v trc nhiu

loi bnh khc nhau, c bit l cc bnh v tim mch, ung th.

Hn hp tanin c trong ch c khnng gii kht v cha nhiu loi bnh nh t, l,

thng hn, si thnNgoi ra trong ch cn cha rt nhiu cc loi vitamin nhm A, Bc bit l vitamin C c nhiu trong l ch ti, l ngun dinh dng qu bu i vi con

ngi.

Bn cnh , ch cn l nt truyn thng ca nhiu dn tc, n mang mt gi tr v

cng thing ling, cao qu trong i sng tinh thn ca con ngi.

L mt trong nhng qu hng ca cy ch vi nhng vng ch ni ting nh Thi

Nguyn, Vnh Phc, Ph Th, Ty Nguyn, Lm ng, cy ch c mt v tr c bit

trong ngnh kinh tv trong i sng ca ngi dn Vit Nam t lu, ch Vit Namc xut khu n nhiu ni trn th gii, em li lng ngoi tng kcho t nc.

Vit Nam, ch l mt trong nm mt hng xut khu ch cht ca nn nng nghip.

Hng nm, kim ngch xut khu ch ln n hng trm triu la M.

Trong cc sn phm ca ch nh ch xanh, ch en, ch vng, ch , ch

trngth trong , ch en l loi ch chim 80-90% tng sn lng trn th gii. V

ch bin ch en, chng ta mi ch trng n vn khi lng, cha ch n cht

lng nn sn phm ch en ca Vit Nam c gi tr thp hn so vi mt snc xut

khu ch en khc.

Vy trong ch c nhng thnh phn no? K thut sn xut ch en nh th no?

Ch en khc ch xanh im no?...th bi tiu lun ny s gip chng ta hiu r v

nhng vn .


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MC LC

Mu

I/ TNH HNH SN XUT V TIU TH CH TRN TH GII V VIT NAM .... 61.1/ Tnh hnh sn xut v tiu th ch trn th gii ........................................................ 6

1.1.1/ Tnh hnh sn xut .............................................................................................. 6

1.1.2/ Tnh hnh tiu th................................................................................................ 7

1.2/ Tnh hnh sn xut v tiu th ch ti Vit Nam....................................................... 9

1.2.1/ Tnh hnh sn xut .............................................................................................. 9

1.2.2/ Tnh hnh tiu th.............................................................................................. 10

II/ THNH PHN HA HC CA CH ....................................................................... 152.1/ Nc ........................................................................................................................ 16

2.2/ Tanin ....................................................................................................................... 17

2.3/ Gluxit....................................................................................................................... 18

2.4/ Pectin ....................................................................................................................... 18

2.5/ Cc vitamin v khong cht trong ch .................................................................... 19

2.6/ Du thm................................................................................................................. 19

2.7/ Protein v cc aminoacid trong l ch .................................................................... 202.8/ Cc hp cht alcoloit ............................................................................................... 21

2.9/ Cc loi enzyme trong ch ...................................................................................... 21

2.10/ Cht tro trong ch .................................................................................................. 22

2.11/ Cc acid hu c..................................................................................................... 23

2.12/ Cht bo v sc t ................................................................................................. 23

III. K THUT CH BIN CH EN THEO PHNG PHP C IN ................. 24

3.1/ Quy trnh ch bin ch ............................................................................................ 253.2/ Thuyt minh quy trnh cng ngh ch bin ch en ............................................... 25

3.2.1/ Nguyn liu ....................................................................................................... 25

3.2.2/ Lm ho l ch .................................................................................................. 27

3.2.3/ V ch v sng ch v ...................................................................................... 32


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3.2.4/ Qu trnh ln men ch en ................................................................................ 36

3.2.5/ Sy ch .............................................................................................................. 39

3.2.6/ u trn ch ..................................................................................................... 44

3.2.7/ Phn loi ch bn thnh phm .......................................................................... 44

3.2.8/ ng thng v bo qun ................................................................................... 45


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I/ TNH HNH SN XUT V TIU TH CH TRN TH GII V VIT

NAM

1.1/ Tnh hnh sn xut v tiu th ch trn th gii

1.1.1/ Tnh hnh sn xut

Ch c sn xut gn 40 nc trn th gii vi din tch 2.25 triu ha, tp trung

mt snc ch yu nh: Trung Quc 1.1 triu ha, n 486 nghn ha, Srilanca 190

nghn ha, ThNh K 80 nghn ha, Kenia 120 nghn ha. Sn lng ch ca cc quc gia

ny cng chim khong 70% tng sn lng ch th gii. Xu th hin nay ca cc nc

trng ch ch yu l ch nhiu n vic tng sn lng v tng nng sut lao ng.

Vic m rng din tch trng ch nhiu nc khng cn l ch tiu chnh. Trong 20

nm gn y (1980 2000) din tch ch t 2.34 triu ha tng ln 2.55 triu ha (tng6.8%), trong khi sn lng tng t 1.85 triu tn ln n trn 2.98 triu tn (tng 61%).

Nng sut bnh qun trn 1 tn/ha cao nht l Papua New Gin t gn 3 tn ch kh/ha,

tip theo l Kenya 2.2 tn/ha. Vit Nam t khong 0.9 tn/ha vn thp hn nng sut

bnh qun ca th gii.

Nm 2000, sn lng ch th gii t 2.95 triu tn. n l nc c sn lng

ch cao nht, hng nm t 850 870 ngn tn; tip n l Trung Quc 680 ngn tn;

Srilanca, Kenya trn 300 ngn tn; Indonesia, ThNh K, Nht Bn trn 100 ngn tn.Vit Nam khong 80 ngn tn, xp th 8 trong tng scc nc c sn lng ch trn th

gii.

V cng ngh ch bin, hin nay cc nc ch yu l sn xut ch en (chim 75%

tng sn lng). Phng php sn xut ch en ph bin l Orthodox v phng php

CTC. Trong sn xut bng phng php CTC ang c s dng ph bin. Cc nc

Kenya Malavi, Banglades 100% ch c sn xut theo cng ngh CTC, n 84.8%,

Indonesia 10% l ch CTC. Trung Quc, Achentina v cc nc Lin X c 100% ch

en sn xut theo phng php Orthodox, Srinlanca ch Orthodox chim 97% tng sn

lng ch en.


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1.1.2/ Tnh hnh tiu th

C mt snc, ch l mt hng xut khu thun ty, trong khi mt snc khc

phn ln sn lng ch li c tiu thtrong nc. Hu nh ton b sn lng ch

Argentina, Kenya, Srilanca c xut khu, trong khi phn ln sn lng ch ca n

v Trung Quc li c tiu th trong nc. Do dn stng nhanh, trong tng lai 2

nc n v Banglades c thl cc nc nhp khu ch. Mc d nhu cu v ch

Trung Quc d kin s tng nhng do chnh sch dn s cng rn v nng sut tng

mnh trong nhng nm gn y dn n vic ngy cng nhiu ch Trung Quc c

xut khu ra thtrng th gii.

S pht trin kinh t ti nhiu nc tiu th ch ln cng nh hng n th hiu v

khu v ca ngi tiu dng. Ch gi cao, c lng gi trtng ln, ang dn thay th cho

ch ri gi thp, cht lng km. Nhu cu ch ti, ch ha tan, ch ung lin ngy cng

gia tng c bit l cc nc cng nghip pht trin. Cc hng sn xut nc ngt c

gas ln ang thm nhp vo thtrng ch nc ng lon (hp Ice tea). Loi ch ny ph

bin M, Nht, Ty u, v bt u c gii trcc nc Chu quan tm. c bit

ti M, nhu cu tiu th ch dc tho ph bin nht, l ch bc h, cam tho, l

hivi nhu cu gia tng v slng cng nh cht lng ca ch th vn v sinh an

ton thc phm c ngi tiu dng cng nh cc nc nhp khu ch ln rt quan tmv ch trng.

nm c tnh hnh sn xut ch ca cc nc v kinh nghim sn xut ca nc

, trong phn ny s gii thiu s lc tnh hnh mt snc nh sau:

Trung QucTrung Quc l mt nc trng ch v ch bin ch sm nht th gii, l qu hng

ca ch. Trung Quc sn xut ra hng chc loi ch v c kinh nghim sn xut phong

ph. Trc y Trung Quc ng hng u v sn lng ch trn th gii v chim ti90% sn lng ch xut khu trn thtrng quc t. Nm 1936, tng din tch trng ch

ca Trung Quc l 364 nghn hecta, ch bin c 309 nghn tn ch. Nhng tri qua

nhiu nm chin tranh v di chnh quyn Tng Gii Thch, ngnh sn xut ch ca

Trung Quc b sa st nghim trng. Sau ngy gii phng, ngnh sn xut ch ca Trung


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Quc dn dn c hi phc: nm 1952 c 244 nghn hecta (khng k 40 nghn hecta

i Loan), nm 1950 ch sn xut c 60 nghn tn ch, n nm 1955 ln ti 104.5

nghn tn v ti nm 1956 din tch trng ch ln ti 300 nghn hecta, sn xut c

120.4 nghn tn. Vo nhng nm 1964 1965 sn xut c 200 nghn tn, ng th

3 trn th gii v sn lng ch, sau n v Srilanca.

n n l nc c lch s pht trin ch cha lu, nhng nhhc tp kinh nghim

ca Trung Quc v cc nc, do iu kin kh hu th nhng thch hp vi s sinh

trng ca cy ch nn ngnh sn xut ch ca n pht trin kh nhanh. Hin nay,

n ng hng u th gii v sn lng ch sn xut hng nm. Nm 1955, tng din

tch trng ch ca n l 320 nghn hecta, sn xut 300.4 nghn tn ch.

Nhng iu ng ch l gn y cng nghip sn xut ch en ca n c nhiu

thay i v k thut sn xut ch yu l p dng cc bin php mi sn xut ra cc loi

ch en ph hp vi yu cu ca thtrng quc t. Ch en sn xut bng phng php

CTC (sn phm ch yu l loi ch mnh) tng ln vi t lcao, cn ch en sn xut

bng phng php truyn thng (sn phm gm hai loi ch cnh v ch mnh) gim

xung r rt. ng thi, ch en lm bng phng php khng lm ho cng tng ln v

t nm 1960 p dng phng php v lin tc. Nguyn nhn ch yu ca phngphp ny l ch, khng nhng dng phng php ny lm cho qu trnh ln men ch

c tin hnh u n v su sc, m cn nng cao c mu sc ca nc ch. Nh

mi ngi u bit, ch en c s dng ph bin cc nc Chu u, nht l Anh

v Lin X c, ch en thng c pha thm ng hoc sa ung. Cch pha ch

en cng khc cch pha ch xanh, ch pha mt ln ri bi, nhng yu cu trong mt ln

pha phi rt chit c gn nh ton b cc cht c trong ch, nc ch phi m c

v c nng cao. t c yu cu ch c loi ch mnh (nhng khng phi lch vn), phng php CTC p ng c yu cu ny v nguyn liu ca n l cc loi

ch mnh (FBOP, BOP, BP). Trong mt snh my ch en ca Trung Quc (nh

Nh my ch en Thiu Hng) cng s dng my ct CTC vo sn xut v ang c

nghin cu vo p dng rng ri.


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SrilancaSrilanca l nc sn xut ra cc loi ch en ni ting. V sn lng, hin nay

Srilanca ng hng th hai trn th gii. Nm 1955, Srilanca c 229 nghn hecta ch, sn

xut 173 nghn tn. Nm 1962, sn xut 210150 nghn tn v ti nm 1963 sn xut

217025 nghn tn ch. Srilanca hng nm xut khu khong 90% lng ch trong nc

sn xut ra.

Nht BnNht Bn ch yu sn xut ch xanh, ch en ch chim 13% tng sn lng ch

hng nm. Nm 1961, Nht Bn sn xut khong 72 nghn tn ch, tng ln khng nhiu

lm so vi nm 1955 (39 nghn hecta, 70 nghn tn ch).

Lin X cVng ch ch yu ca Lin X c l Gruzia, min Kratnoda thuc Nga v

Adecbaidan.Nm 1955, din tch trng ch Lin X l 74.5 nghn hecta, ch bin c

36.5 nghn tn ch. Ring vng ch ca Gruzia Lin X, nm 1955 c 63.1 nghn hecta,

ch bin c 33.7 nghn tn ch, trong c 28.7 nghn tn ch ri, cn li l ch bnh.

IndonexiaVng ch ch yu ca Indonexia l o Giava, ch yu sn xut ch en, ng hng

thba trong cc nc t bn v sn xut ch. Nm 1951, c 138.5 nghn hecta. Nm1955 ch cn 64 nghn hecta (bng 46.2% so vi trc chin tranh) v sn xut c 43.5

nghn tn ch.

Ngoi ra trn th gii cng c nhiu nc trng v sn xut ch, v dPakistan cng

l mt vng ch ln. Cc nc Uganda, Tanganica, Congo hng nm cng sn xut c

khong t3.7 n 4.8 nghn tn ch.

1.2/ Tnh hnh sn xut v tiu th ch ti Vit Nam

1.2.1/ Tnh hnh sn xut

Him c ni no trn th gii li c u i nh Vit Nam, hu nh c th trng

ch khp ni. V phn a l 32/61 tnh thnh trong cnc c th trng ch, t trung

dumin ni pha Bc, ng bng Bc B, Bc Trung B, n Duyn Hi Min Trung, 5


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tnh Ty Nguyn Nhng vng c din tch trng ch ln nh trung du min ni pha

Bc v cao nguyn Lm ng thng tp trung lin i, lin khonh.

Din tch trng ch nc ta t 10500 ha (1995) tng ln 70000ha (1998), sn

lng ch kh t 5200 tn (1995) tng ln 49580 tn (1998).Nm 2005 l nm thng

li ln ca ch Vit Nam, sn xut v xut khu t mc k lc. Do thng thong th

trng v cc chnh sch pht trin cy ch cc a phng, nm 2006 cnc trng

thm khong 92000ha, a tng din tch ch ln gn 100000ha, trong din tch ch

kinh doanh khong 80000ha. D kin nm 2010, din tch trng ch ln gn 110000ha.

Sn lng ch cnc t 80000 tn, tng 15% so vi nm 2000. n nay Vit Nam

ng th 8 tng tng s 34 quc gia sn xut ch trn th gii sau n , Trung Quc,

Srilanca, Kenya, Indonesia, ThNh K v Nht Bn.

1.2.2/ Tnh hnh tiu th

Thtrng ni tiuLoi ch tiu th ch yu trong nc l ch xanh nh ch H Giang, ch Thi

Nguyn, ch Tuyn Quang, ch Lm ng Do nhu cu th hiu ca ngi tiu dng

ngy cng cao, n nay cc loi ch c p hoa ti cng c tiu th mnh: ch hoa

nhi, ch hoa sen, ch hoa si, Ch en dng ti cng c ngi tiu dng a

chung. Nm 1996, tng lng ch ni tiu l 20000 tn, bnh qun 0.274kgch/ngi/nm. Nm 2000, tng lng ch ni tiu tng gp i so vi nm 1996.

Theo E TradeNewsTrong 2 thng u nm 2007, tnh hnh xut khu ch ca

Vit Nam tng i kh quan vi lng ch xut khu c t 14 nghn tn, kim ngch

t 16 triu USD, tng 27% vlng v 45% v gi tr so vi cng knm 2006. D bo

trong nm 2007, vi squan tm ng mc ca nh nc v nhng n lc u t ca cc

n v sn xut, ngnh ch Vit Nam st mc tng trng cao nh nm va qua.

Theo s liu thng k ca Tng cc Hi quan, tnh ring thng 1/2007, cnc xut khu c 8.4 nghn tn ch cc loi vi kim ngch t trn 8 triu USD, gim

21.6% vlng v 24% v gi tr so vi thng 12/2006, tng 62,3% vlng v 51% v

tr gi so vi cng knm 2006.


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Trong thi gian ny, gi ch xut khu ca Vit Nam tip tc c xu hng gim, ch

ng mc 954 USD/tn, gim 29USD/tn so vi thng 12/2006. Tuy nhin trong thi

gian ti, d bo gi ch stng do sn lng ch th gii hin ang gim mnh trong khi

nhu cu tiu th li tng, nht l ti cc quc gia Hi gio.

Thng k ca B Nng nghipPht trin nng thn (NNPTNT) cho thy, ti 20

tnh vng ch tp trung ca cnc c 240 c sch bin cng nghip, tng cng sut

trn 3100 tn bp ti/ngy (600000 tn bp ti/nm), mi p ng c 88% nhu cu

nguyn liu ch bp ca cc c sch bin cng nghip.

Theo b NN PTNT, ti cc tnh vng ch min ni pha Bc, s pht trin qu

nhiu c sch bin khng cn i vi nguyn liu nn tnh trng tranh chp nguyn liu

kh gay gt trong nhiu nm qua, c bit Ph Th, Thi Nguyn, Tuyn Quang

Ring Ph Thc 75 c sch bin. Song, ch tnh nhu cu nguyn liu ti ch ca cc

cng ty ch Ph Bn, Ph a v ca t nhn ln ti 175000 tn ch bp ti/nm.

Trong khi , sn lng ch bp nm 2005 mi t 63700 tn, chp ng c 36%

nhu cu nguyn liu ca cc c sch bin trn a bn.

B NNPTNT cho bit, min ni pha Bc l vng ch pht trin sm nht, c din

tch ln nht nc. Ti y, c nhng loi ch ni ting trong nc v trn th gii nh

Tn Cng (Thi Nguyn), Thanh Ba (Ph Th), Mc Chu (Sn La), Shan tuyt SuiGing (Yn Bi), Tng din tch ch ton vng nm 2005 xp x 90800ha, chim

80,7% din tch ch ton quc. Trong , Thi Nguyn l a phng c din tch ch ln

nht vng vi 16400ha (18.1%). Mc d tc tng din tch ch cao n chng mt

trong vng 10 nm qua (1996 2005), ln ti gn 15%, nhng sn lng ch vn thiu

ht do khng chy theo ni slng nh my, c sch bin v do nng sut ch khng

cao. Trn 70% din tch ch hin s dng cc ging ch cht lng trung bnh. Hu ht

din tch ch phn tn ca cc hdn cn lm t bng th cng. Din tch ch c tinc ch chim khong 2%.

Theo Hip hi ch Vit Nam, d thng hiu ch Vit Nam c ng k ti 77

quc gia v vng lnh thnhng nng cao v th ca ch Vit Nam trn thng trng

quc ti hi cc nh sn xut ch trong nc phi tip tc ch trng nng cao cht


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lng ch v ngy cng i vo tiu chun ha. Vit Nam hin ang ng th 9 v sn

lng, chim 4% sn lng ch trn ton th gii v xp th 7 v xut khu (nm 2004).

Tuy nhin sn phm ch ch bin ti Vit Nam th n iu cha phong ph v chng

loi, mu m, t li n tng i vi ngi tiu dng trong nc v quc t. Theo ng

o Vn Khng, Gim c D n Pht trin ch v cy n qu, gp phn nng cao

cht lng ch, ngnh ch cng a ra nhiu gii php nh mcc lp o to nng

cao k thut chm sc ch; tng cng nng lc nghin cu to ra cc ging ch c

nng sut, cht lng cao, ph hp vi iu kin sinh thi ca mi vng min trong nc;

cung cp vn tn dng u t trng mi, thm canh, ch bin theo hng cht lng cao.

Thtrng xut khu:ng u danh sch nhp khu ch Vit Nam l Irag, Pakistan, i Loan, Nga, n

, Ba Lan, M vi 90.86% khi lng v 89.9% tr gi. Tuy nhin, th phn ch ca

Vit Nam cc nc ny vn cn nhv ang b cnh tranh gay gt. Irag l thtrng c

ngha c bit quan trng do gi xut khu cao hn cc nc v lng xut khu ln

(14.3 nghn tn nm 2002), nhng do nh hng ca chin tranh, xut khu ch cng gp

kh khn.

Ti Chu , Vit Nam c 2 khch hng ln l Nht Bn v i Loan. Ch Vit Nam

ch chim 6.5% t trng v gi thnh ch bng 35% so vi gi nhp khu tcc nckhc. Vi EU, ch Vit Nam ch chim 1- 1.5% tng kim ngch. Gi ch Vit Nam ti

y ch bng 40% so vi mt bng gi nhp khu tcc nc khc nhau. Mt khc, trong

15 nc thnh vin EU ch c Hy Lp v Luxembour l khch hng thng xuyn, 13

nc cn li c nhp ch ca Vit Nam nhng khng n nh. u nm 2003, ch Vit

Nam mt th trng Italia, Bo Nha v Phn Lan. Ro cn ln nht ca Vit

Nam khi vo cc nc ny l vn kim dch.

Vi thtrng Mnm 2002, ch Vit Nam xut khu sang M 2200 tn (chim 3%thtrng ch ti M) trong ch en chim khong 80% tng gi tr xut khu vo th

trng ny.

Th trng Pakistan: nm 2002 Vit Nam xut khu 12400 tn vo th trng ny

nhng ch yu l ch xanh.


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Cc loi ch xut khu ch yu ca Vit Nam l ch en chim 6070%, ch xanh

25 - 30% v cc loi khc 510%.

Xt v mt cht lng v uy tn trn thtrng th gii th ch Vit Nam vn l loi

khng c tn tui v thng xp sau ch Indonesia. Ch ca ta thng c u trn vi

ct ca cc loi ch khc hoc chit xut. y cng l l do ch cao cp ca ta bn rt

kh. Do vy nu gi ch ca th gii gim th ch Vit Nam gim nhanh hn v nu gi

ch tng trli th gi ch ca ta cng tng chm hn.

Tuy nhin, theo Hip hi ch Vit Nam cho bit, hin nay cng c nhiu thng

hiu ch ca cc doanh nghip trong nc c ngi tiu dng a chung, l: long

Thun ca Cng ty TNHH Tra C ph Tm Chu, Lm ng; Tri m tr ca Cng ty

TNHH Hong Bnh, Thi Nguyn; Ch Long t qu ca X nghip ch bin hng xut

khu Cu Tre,

Theo s liu thng k, trong 2 thng u nm 2007, lng ch xut khu ca Vit

Nam t 14 nghn tn, kim ngch t 16 triu USD, tng 27% vlng v tng ti 45%

v tr gi so vi cng k nm 2006. Trong , phn ln l ch en vi sn lng chim

khong 75%.

Gi xut khu ch en trung bnh trong thng 2/2007 mc 816 USD/tn, gim 11

USD/tn so vi thng trc. Xut sang th trng Phn Lan t mc gi cao nht vi1590 USD/tn (FOB), tng 60 USD/tn so vi thng trc.

Cc thtrng xut khu ch en nhiu nht trong thi gian ny l Nga, Pakistan,

M, Anh, i Loan v UAE. Trong , Nga l thtrng tiu thch en nhiu nht vi

sn lng c t 1088 tn, tr gi 1830 USD (FOB), tng 11% vlng v 86% v tr

gi so vi thng 12007.

Thng 3 2007, kim ngch xut khu ch vo Pakistan t 600 nghn USD, gim

48% so vi thng 2/07 v gim 57% so vi cng knm trc. C cu thtrng xutkhu ch ca Vit Nam trong thng 3 thay i, xut khu ch vo Pakistan gim mnh v

i Loan vn ln l thtrng xut khu ch ln nht ca Vit Nam. Trong thng ny,

Pakistan ch l th trng xut khu ch ln th4, ng sau i Loan, Nga v Trung


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Quc. Tuy nhin, tnh cqu I nm 2007, xut khu ch vo thtrng ny vn t cao

nht vi kim ngch t 2.9 triu la M.

Tnh chung, trong qu I nm 2007 ca cnc vn tng i kh quan vi kim

ngch xut khu t gn 19 triu USD, sn lng t xp x 20 nghn tn, tng 2% v tr

gi v 4% v sn lng so vi nm 2006.

Xut khu ch vo Nga v Trung Quc tng cao trli sau khi st gim vo thng 2

2007 v tng mnh so vi cng knm trc. c bit l xut khu vo Srilanka, trong

thng 3 2007 kim ngch xut khu ch vo th trng ny t 305 nghn USD, tng

241% so vi thng trc v tng gp 16 ln so vi cng knm trc.

Trong thng 1 2007, lng ch xut khu ca Vit Nam sang hu ht cc th

trng ln u gim so vi Ml tng. C th, lng ch xut khu sang cc thtrng

truyn thng nh Pakistan, i Loan, Nga, Trung Quc v n gim ln lt 24%;

24.3% so vi thng 12/2006. Trong khi , lng ch xut khu sang Indonexia v M

tng 44.7% v 31.4%.

Mc d xut khu ch sang Pakistan gim mnh c vlng v trgi, nhng y

vn l thtrng xut khu ch ln nht ca Vit Nam. Trong thng u nm 2007, kim

ngch xut khu ch ca Vit Nam sang thtrng ny t xp x 1.8 triu USD vi sn

lng t 1.6 nghn tn, gim 30% v tr gi v 24% vlng so vi thng 12 2006.Trong , ch en l chng loi c xut khu ch yu sang th trng ny vi sn

lng t trn 1000 tn, tr gi 1.1 triu USD, gi xut khu ch en trung bnh mc

1078 USD/tn (FOB), gim 42 USD/tn so vi thng 12/2006.

Cng vi Pakistan, lng ch xut sang i Loan v Nga hai thtrng xut khu

ch ln th 2 v th 3 ca Vit Nam trong thng 1/2007 cng c mc gim ng k.

Lng ch xut sang i Loan t 1.3 nghn tn tr gi 1.2 triu USD, gim 24.3% v

lng nhng li tng 8.1% v tr gi so vi thng 12/2006, lng ch xanh tng 108% vlng v 80% v tr gi so vi cng knm 2006. Lng ch en xut sang i Loan

trong thi gian ny t 800 tn, tr gi 390 nghn USD, gim 31% vlng v 32% v

gi tr so vi thng 12/2006.


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Lng ch xut khu sang Nga trong thng 1/2007 t xp x 1100 tn, tr gi trn 1

triu USD, gim 24.2% v lng v 22% v tr gi so vi thng 12/2006, tng 73% v

lng v 63% v tr gi so vi cng knm 2006.

Ch xanh l chng loi xut khu duy nht sang thtrng ny.

Vn gi: Trong thng 1/2007, gi trung bnh xut khu ch en ca Vit Nam

mc 1287USD/tn (FOB), n nh so vi thng 12/2006. Thtrng xut khu ch en

t mc cao nht l c vi 1420 USD/tn (FOB), thp nht l i Loan vi 309

USD/tn (FOB). Gi xut khu ch xanh mc 1406 USD/tn (CFR), trong , xut

sang thtrng Philippin t mc gi cao nht vi 2980 USD/tn.

II/ THNH PHN HA HC CA CH

Bng: Thnh phn ha hc ca l ch ti

Thnh phn Hm lng (%)

Nc 7580

Flavanol:

(-) Epigallocatechin gallate (EGCG) 812

(-) Epicatechin gallate (ECG) 36

(-) Epigallo catechin (EGC) 36

(-) Epicatechin (EC) 13(+) Catechin (C) 12

(+) Gallocatechin (GC) 34

Cafein 34

Acid hu c (Citric, Malic, Oxalic) 0.50.6

ng ( Glucose, Fructose, Saccarose, Rafinose,

Starchiose)

45

X (Xenlullose, hemixenlullose. Lignin) 47

Protein v acid amin 1417

Lipid 35

Khong 56

Cht mu 0.50.6


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Enzyme

2.1/ Nc

Trong l ch nc tn ti hai dng: nc tdo v nc lin kt.

Nc l thnh phn ch yu trong bp ch.

Nc c quan hn qu trnh bin i sinh ha

trong bp ch v n s hot ng ca cc men,

l cht quan trng khng th thiu c duy tr

s sng ca cy. Hm lng nc trong bp ch

thay i ty theo ging, tui cy, t ai, k thut

canh tc, thi gian hi v tiu chun hi Trong

bp ch (tm + 3 l) hm lng nc thng c

t 7582%. trnh khi s hao ht nhng vt

cht trong bp ch qua qu trnh bo qun v vn chuyn, phi c gng trnh s gim bt

nc trong bp ch sau khi hi.

Nc trong nguyn liu ch l mi trng xy ra tng tc gia cc cht c trong

nguyn liu ch khi em ch bin. Nc tham gia trc tip vo nhiu phn ng thy

phn, oxi ha kh. Hm lng nc c quan h mt thit i vi qu trnh ch bin ch.Nu nguyn liu ch b mt nc qu nhanh th bin i sinh ha din ra nhanh v

khng trit , i khi enzyme bc ch nu hm lng nc qu thp ( bp > l 1 > l 2> l 3.

Ph thuc vo lin v: Hm lng nc trong l ch vo ma xun >vo mah >vo ma thu. Ch hi vo u v v gia v c hm lng nc ln hn

ch hi vo cui v.


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Ph thuc vo cht kch thch sinh trng: Khi cy ch c bn nhiu phnm th hm lng nc tng ln do cht lng ch thp cn khi cy ch

c bn nhiu phn ln v phn kali th hm lng nc gim do vy m cht

lng ch cao.

2.2/ Tanin

Tanin l hp cht quan trng trong l ch, n c

tnh cht quyt nh n mu sc nc pha, hng

thm v v cht ca nc ch. c bit l ch en.

Tanin c c tnh d b oxi ha di tc dng ca

enzym v c cung cp oxi y . V vy, ch

nguyn liu cha cng nhiu tanin, c bit l tanin

ha tan th sn phm ch en c cht lng cng cao.

Flavanoids l thnh phn quan trng ca Tanin, trong

Catechin v Flavanoids chim t l ln.

Tanin thng c hai loi:

Tanin ngng t: tc dng vi FeCl3cho mu xanh en. Tanin thu phn: tc dng vi FeCl3 cho mu xanh da tri.

V hu ht tanin trong ch l tanin ngng t, cht tiu biu cho tanin ngng t lcatechine bao gm catechinen v gallo-catechinen.

Trong sn xut ch en, Catechin c v tr quan trng trong vic to mu sc, mi, v

cho ch thnh phm. Catechin l hp cht khng mu, tan trong nc, c vng, cht.

Hp cht polyphenol thng chim khong 27-34% cht kh trong ch. Theo kt

qu nghin cu cc ging ch, thnh phn t hp ca tanin ch trong nguyn liu ch ti

gm c:

Nhm cht catechin (tin cht ca tanin) n phn t (thuc nhm chtpolyhydroxylphenol - monomer) chim khong trn 80% tng lng tanin ch,

c v cht- ng mnh hn so vi tanin c bit.

Nhm tanin c bit: Chnh l polyphenol a phn t, chng to mu v v chtdu cho ch.


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Nhm cht phi tanin: Nhm ny gm 7 catechin khc nhau l Epicatechin(EC), Epigalocatechin (EGC), Galocatechin (GC), Epicatechingalat (ECG),

Epigalocatechingalat (EGCG), Galocatechingalat (GCG) v Catechin.

2.3/ Gluxit

Trong t ch ti c cha hu ht cc loi gluxit khc nhau nhng cn ch 2

im sau:

Tng lng gluxit khng cao, n chim khong 20% cht kh trong ch non. Cha rt t cc gluxit ha tan, trong ng monoza (nh glucoza, fructoza)

chim khong 1-2% cht kh v saccaroza chim khong 0,5-2,5% cht kh.

Nu thy tng lng gluxit cao c ngha l phn gluxit khng tan (nh

xenlluloza, licnhin, hemixenlluloza) tng ln lm cht lng ca ch gimxung. Thc t, nhm cht ny c quy lut bin i hm lng ngc vi quy

lut bin i hm lng cc cht c li cho cht lng ch nh protein, tanin.

Trong l ch hm lng gluxit khng nhiu v thay i theo gi non ca l.

Tng lng ng trong l ch thng l 1.63-4.33% so vi lng cht kh

trong ch. Trong hm lng ng kh l 0.99-1.91%. Lng ng trong

l ch non c t v l ch cng gi cng c nhiu.

2.4/ PectinHm lng pectin trong l ch kh cao t 11-17% so vi lng cht kh trong l

ch v ch cng gi hm lng pectin cng cao.

Trong ch, cc hp cht pectin tn ti cc trng thi l ho tan trong nc, ho tan

trong axit oxalic v ho tan trong amon-oxalat. Pectin tham gia vo vic to thnh hng

v ch, lm cho ch c mi to chn trong qu trnh lm ho. Hm lng pectin trong ch

chim khong 2% cht kh v lun thay i ph thuc vo nhiu yu t nh trng

thnh ca l ch, l cng non th hm lng pectin ho tan trong nc cng tng nhng

lng pectin ho tan trong hai dung mi cn li gm. Ngoi ra trong cng ch cng rt

giu cht pectin.

Pectin c tnh keo, khi b hydrat ho th tnh keo tng ln. Do , tnh dnh ca l

ch tng ln, nh l ch cun chc li giai on v hay giai on to hnh cnh ch


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v s lm cho c khi ch bn thnh phm bm cht vo nhau, di tc dng ca lc p

khi sn xut ch bnh m sn phm s theo hnh dng ca khun p. Do c tnh keo nn

pectin cn c tc dng lm tng nht ca nc ch v lm cho cc nc ch snh, hp

dn, ng thi pectin cng lm cho v ch d chu hn. Pectin cng c tnh ht m mnh,

v vy n nh hng xu trong qu trnhbo qun ch.

2.5/ Cc vitamin v khong cht trong ch

Cc loi vitamin c trong ch rt nhiu. Trong bp ch cha hu ht cc loi vitamin

nh vitamin A, B1, B2, PP, c bit vitamin C c rt nhiu trong ch. Chnh v vy gi tr

dc liu cng nh gi trdinh dng ca ch rt cao. Theo cc ti liu ca Trung Quc,

hm lng mt s vitamin trong ch tnh theo mg/1000g cht kh nh sau: Vitamin A:

54.6; B1: 0.70; B2: 12.20; PP: 47.0; C: 27.0 v.v

ng ch nht l hm lng vitamin C trong ch, nhiu hn trong cam chanh t

3 n 4 ln. Qu trnh ch bin ch en lm cho vitamin C gim i nhiu v n b oxy

ha, cn trong ch xanh th n gim i khng ng k.

Trong ch thnh phn khong chim t 47%, ch yu l K, chim gn 50 % tng

lng khong.

Trong l ch gi, l ch xu th thnh phn cht khong thng cao hn l ch non

v trong cc loi ch c cht lng cao.2.6/ Du thm

Hm lng tinh du thm trong ch, theo ti

liu nghin cu ca Nht Bn, hm lng du

thm trong l ch ti khong 0.02%. S tch lu

cc cht thm ph thuc vo ging ch, iu kin

kh hu v t ai.

Trong thnh phn ca du thm hm lngru 6 cacbon chim 60%, cc loi ru ny

trong l ch ti c mi hng v nhit si l 157-158 0C. Trong qu trnh sn xut, ch

thnh phm c qua nhiu qu trnh gia cng nhit nn cc cu t du thm c nhit

si nhhn 2000C d b mt i.


20/47



Ngoi cc cu t tinh du hng thm ca ch cn lin quan n cc cht c tnh

hp ph v gi hng trong thnh phn ca ch lm cho sn phm bn hn. Nh vy,

hng thm ca ch c hnh thnh t cc ngun sau:

Lng tinh du c sn trong nguyn liu. Lng cc cu t thm mi c to thnh trong qu trnh ch bin. Nhng cht c tnh hp ph v gi hng. nh hng ca nhit cao khi dng nc si pha ch n cc cht khng to

mi nhit thng.

Hng thm ca ch en thnh phm c to thnh ch yu do s oxy ho hoc

kh cc cht thm sn c to nn, bao gm cc cht ch yu l: n-butylandehit, izo-

butylandehit, izo-valerandehit, benzandehit, linaleol...v cc este ca chng. i vi cthcon ngi du thm c tc dng kch thch thn kinh v nng cao hiu sut lm vic

cc c nng ca c th.

2.7/ Protein v cc aminoacid trong l ch

Thnh phn cc hp cht protein trong

ch rt cao, khong 25-30% so vi lng cht

kh. L ch cng non hm lng cht kh

cng cao. Trong ch protein ni chung hotan trong nc, n t nh hng ln n cht

lng ch, tuy nhin, phn no cng lin

quan n cht lng ch v hm lng tanin

trong ch thp khi b tc dng vi protein to

thnh cc hp cht khng tan. Protein c th

kt hp trc tip vi Tanin, polyphenol, to ra nhng hp cht khng tan lm c nc

ch en.

Ngi ta tm thy 17 acid amin c trong ch. Trong 10 acid amin c bn l:

Theanine, phenylalanine, leucine, isoleucine, valine, Tyrosine, glutamine, serine,

glutamic, aspartic. Cc acid amin ny c th kt hp vi ng, tanin to ra cc hp cht

aldehyde, alcol c mi thm cho ch en. Cc aminoaxit trong ch khng nhiu, thng


21/47



khong 0.2-0.3% cht kh, n c tc dng tt i vi cht lng ch en. Cc aminoaxit

tc dng vi tanin trong qu trnh ch bin to thnh cc andehit thm.

Cng nh cc thnh phn ho hc khc, hm lng cc cht cha nit cng nh

protein trong l ch lun lun thay i v ph thuc vo nhiu yu t nhng u tun

theo quy lut l l cng non th hm lng ca chng cng cao, ch u v c cha nhiu

protein hn ch cui v. Ch chm sc bn nhiu phn m th hm lng protein

cng cao.

2.8/ Cc hp cht alcoloit

Cc hp cht alcoloit trong ch phn ln khng tan trong nc v tan nhiu trong

dung mi hu c, trong cc hp cht alcoloit quan trng nht l cafein, sau l

teobromin v teofelin, xantin, adenin, cholin, tetrametyluric...

Cafein trong ch chim 3-5% tng lng cht kh, ch cng non hm lng cafein

cng cao. Cafein l cht kch thch thn kinh, gy nghin, c kh nng tn ti kh lu

trong mu, cafein b thng hoa nhit 1800C nn t b tn tht nhiu khi sy.

Trong qu trnh ch bin cafein t bthay i, nhng i vi sn xut ch en n tc

dng vi tanin to thnh tanat cafein c mi thm v v d chu.

Khi pha nc, hp cht tanat caffein b kt ta khi nc ch ngui to thnh vng

ch.2.9/ Cc loi enzyme trong ch

L nhn t quan trng trong qu trnh sinh trng v ch bin ch, c bit trong

ch bin ch en. Enzyme c vai tr quyt nh chiu hng bin i cc phn ng sinh

ha trong giai on lm ho, v, ln men. Trong bp ch c 2 loi enzyme ch yu l:

Nhm enzyme thy phn: amilase, protease, glucosidase Cc men ny u gi vaitr quan trng trong s phn gii cc hp cht phc tp, a phn t, khng ho tan

thnh cc cht c phn t thp, ho tan. Do , gp phn lm tng cht ho tan trongch. Hn na, cc cht ny cn l tin cht ht sc cn thit cho s to thnh cc

cht mi, to hng v c trng cho ch sn phm sau ny, c th nh sau:

Pectinaza thu phn protopectin thnh pectin ho tan.


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Amilaza thu phn tinh bt khng tan thnh ng, cc ng kh ny va cvai tr to v, va tham gia vo cc phn ng to cht thm, cht mu cho ch.

Proteaza phn gii protein thnh cc axit amin, cc axit amin ny trc tiptham gia vo to v cho ch v c bit l chng tham gia vo cc phn ng to

hng thm nh to cc aldehyt thm mi hoa qu lm tng mi hp dn ca

ch.

Nhm enzyme oxi ha kh: peroxidase, polyphenoloxidase Trong , mencatalaza tn ti c hai trng thi l t do v lin kt, n xc tc cho phn ng phn

gii cc hydroperoxyt to ra cc nguyn txi (O) gp phn y mnh tc dng

ca men peroxydaza v polyphenolxydaza.

Enzyme peroxidase, polyphenoloxidase ng vai tr quan trng nht v c tc dng

khc nhau trong qu trnh ln men ch en. Cc enzyme ny u hot ng mnh 45C,

n 70C th hot ng yu hn i v nhit cao hn s b v hot hon ton.

V trong sn xut ch quan trng nht l nhm enzyme oxy ho -kh. Enzyme

peroxidaza xc tc cho qu trnh oxy ho tanin to thnh sn phm mu sa v hng

v ca ch en.

2.10/ Cht tro trong ch

Cc nguyn t tro gi vai tr quan trng trong hot ng ca c th sng, chng lnhng nhn t ca sthay i trng thi cc cht keo v nh hng trc tip n s trao

i cht ca t bo.

Hm lng cht tro trong ch khng nhiu, trong ch ti khong 4-5% v trong

ch thnh phm l 5-6%. Hm lng cht tro trong ch lun thay i v ph thuc vo

nhiu yu t trong ph thuc rt ln vo non gi ca t ch ti, thi k sinh

trng ca cy ch. Do , da vo hm lng cht tro cng c th nh gi s b c

cht lng ca nguyn liu v sn phm.Cht tro chia lm hai nhm: nhm ho tan v nhm khng ho tan.

Ch loi tt cht tro ni chung t hn ch loi sng, cht tro ho tan trong ch loi

tt li nhiu hn.


23/47



2.11/ Cc acid hu c

Trong thnh phn ha hc ca ch c cha cc axt hu c nh a.malic (c trong

qu to), a.limonic (c trong qu chanh), a.xucxinic v a.fumaric.

Trong giai on v ch en, hm lng cc axt malic v xucxinic tng ln r rt,

cn a.oxalic ch tm thy dng mui canxi-oxalat. Cc acid ny bin i trong cc qu

trnh ch bin.

2.12/ Cht bo v sc t

Trong l ch, cht bo chim khong 5-6% cht kh v cc cht mu ha tan trong

cht bo nh clorofin (c mu xanh), caroten (c mu vng), xantofin (c mu da cam),

antoxianidin (c mu hng) chim khong 0,3% cht kh. Hm lng cht bo trong

ch cng lun thay i v ph thuc vo nhiu yu t nh ging ch, thi v thu hi, vtr ca l trn cy. Vo u v, hm lng cht bo cao nht sau gim dn vo gia v

v n cui v li tng ln nhng khng bng gi tr ban u.

Cht bo c nh hng n cht lng ch, n tham gia vo s hnh thnh hng

thm do trong thnh phn cht bo cng c mt s cu t c mi thm hoc di tc

dng ca nhit s chuyn thnh cht thm. Cht bo c tnh hp ph mi v gi mi,

tnh cht ny ca cht bo gip cho qu trnh p hng b sung cho ch bng hng

liu hoc hoa ti c thun li, gip trnh tn tht v mt mi ch khi bo qun nhngcng c hi khi v ch tip xc vi vt c mi l s lm cho ch b nhim mi l

v rt kh kh b mi l ny.

Clorofin v cc cht mu km theo ho tan trong cht bo ca ch l nhng cht c

vai tr khc nhau i vi cy ch v ch bin cc loi ch. Trong cy ch, clorofin gi vai

tr quan trng trong qu trnh quang hp. Trong ch bin ch xanh, caroten v xantofin

to mu xanhti hoc xanh vng t nhin cho nc ch nhng trong ch bin ch en,

clorofin nh hng khng tt n mu nc v b ch thng c mu xm. Trong cngngh ch bin ch xanh th clorofin b mt nhiu nht giai on hp v sy, cn caroten

v xantofinbin i khng ng k. Trong mi trng kim, clorofin tn ti tt v cho

mu xanh, cn trong mi trng axt th cho mu vng do nhn Mg ca clorofin b mt i

v bin thnh feofitin c mu xm tro.


24/47



III/K THUT CH BINCH EN THEO PHNG PHP C IN

Trong qui trnh sn xut ch en, ngi ta tn dng trit enzym c trong nguyn

liu. Nc ch pha c mu nu, v m, cnh ch c mu en t nhin. Ch en c

nhiu nc trn th gii a chung.

Ty theo cht lng ch en m ngi ta chia sn phm ch en thnh cc cp loi

khc nhau. Theo TCVN, ch en c phn thnh cc cp loi nh OP, BOP, FBOP, PS,

P, BPS, F v DUST. C yu cu k thut c th cho tng loi.

Hin nay, c hai phng php sn xut ch en:

iu chnh qu trnh sinh ha nh tc dng ca enzymc sn trong nguyn liu. Phng php ny c nhc im l thi gian ch

bin di v cht lng sn phm khng cao. phng php ny vn cha c nhiu ni p dng. C s

ca phng php ny l vic iu chnh qu trnh sinh ha khng ch nh

enzym c trong nguyn liu m cn c qu trnh nhit luyn nn s dng trit

hot tnh ca enzym.


25/47



3.1/ Quy trnh ch bin chtheo phng php c in

3.2/ Thuyt minh quy trnh cng ngh ch bin ch entheo phng php c

in

3.2.1/ Nguyn liu

Nguyn liu dng trong sn xut ch l nhng bp ch 1 tm (bp ch) 2 hoc 3 l

non. Nguyn liu ch tt hay xu nh hng rt ln n qu trnh ch bin v cht lng

ch thnh phm.


26/47



Qua nghin cu ngi ta thy mt s tnh cht ca l ch c lin quan ti cht lng

ch nh sau:

to nh v nng nh ca nguyn liu ch: Nguyn liu ch nu c hi trncng mt cy th bp ch cng nh v bp ch cng tt, bp cng to cht lng

cng xu v nhng bp ch cng to trng thnh v dn c xu hng chuyn

thnh bp ch gi, thnh phn ho hc ca n km hn bp ch non.

Xt v nng nh: Trong cng mt bp ch tm nhhn l v l th nht nhhn l th 2...Nn nu cng mt ging ch, bp cng nh cht lng ch cng tt

v t l hng tt cng cao.

Mu sc ca l ch ti: mu sc ca l ch ti ph thuc vo ging ch, nitrng v iu kin chm bn. Nhn chung mu sc ca l ch c lin quan n

cht lng ch thnh phm. L ch c mu xanh thm th hm lng tanin khng

cao, hm lng clorofin v protein tng i cao. L ch c mu xanh hoc

vng nht mng th hm lng clorofin thp, hm lng tanin cao.

Ngoi ra, di ca bp, dy mng ca l cng lin quan n cht lng cach. Bp ch cng di, l ch cng mng th cht lng cng tt v khi ch bin

cht lng ch thnh phm cng cao.

Thu hi vn chuyn v bo qun ch: Thu hi, vn chuyn

Ch nguyn liu c thu hi

dng 1 tm, hai hoc ba l.

iu kin thu hi cng nh hng

n cht lng ch thnh phm. Cht

lng ch tt nht l c thu hi vo

bui sng nhng hi qu sm sng

nhiu cng nh hng xu n qu trnh

vn chuyn v bo qun l ch.

Khi vn chuyn, ch c ng

vo cc st, khi lng khng ln hnThit b phn loi ch


27/47



15 kg/st. Xe cng nng chkhong 1 tn/xe, phi lm gin trn xe v c mi che

ma nng. Trnh cht ng, ln p, lm dp nt, bc nng nguyn liu. Khi vn

xng phi nhanh chng gii phng ch ra khi phng tin vn chuyn v dng c

cha ng. Sau cn nhn v tin hnh phn tch cht lng, nguyn liu c

chuyn dn sang khu lm ho.

Bo qu b t

Bo qun bng phng php thong gi tch cc: Ch ti c ri thnh lp trn

sn li vi b dy 20 cm. Khng kh trc khi thi vo lp ch c lm m n m

tng i W = 92 n 95% bng cch phun m b sung.

Nhit ca khng kh gim i khong 1 n 2oC do c tip xc trc vi dng

nc phun, c qut ly tm thi theo hng tdi ln vi lu lng 6 m3 cho 1 kg ch

ti/gi. Thi gian bo qun 24 gi.

Bo qun theo phng php ny, s bin i xy ra rt chm, m ca l ch, hm

lng cht tan, hm lng tanin, hot tnh ca men PPO gn nh khng thay i. Trong

sut 18 gibo qun, nc ch vn xanh cha chuyn sang mu vng, chng t trong l

ch hu nh cha xy ra s chuyn ha ha hc. S tn tht cht kh ch tn tht 0,9%

(sau 24h bo qun cn 99,1% so vi ban u) v 0,3% (sau 24h bo qun cn 99,7% so

vi ban u).3.2.2/ Lm ho l ch

3.2.2.1/ Mc ch ca qu trnh lm ho

Lm gim bt nc trong nguyn liu, l ch mt i lc trng, to ra tnh n hi,bp ch trnn mm, do, dai hn to iu kin tt cho qu trnh v ch.

Qu trnh ho cn l qu trnh sinh ho, lm bin i su sc thnh phn ho hc cabp ch, phn gii cc cht c phn t ln thnh cc cht c phn t nh, c li cho

cht lng ch en. Trong qu trnh ho cc cu thng thm c tng c v slng v cht lng.

Qu trnh ho cn lm tng hot ng ca cc enzyme oxy ho c bit l

Polyphenol oxydase, c tc dng tt cho qu trnh ln men tip.


28/47



3.2.2.2/ Yu cu ca qu trnh lm ho

Ch phi c lm ho ng u, v c lm ho ng mc. Nu lm ho qu ccqu trnh bin i sinh ho b ngng li, l ch b kh v vn cn vng mi hng

ban u.

Cc thng s k thut ch yu ca qu trnh lm ho : Nhit v m ca khngkh: trnh ngng tnc trn b mt l v hi nc c thot ra d dng, yu

cu nu lm ho t nhin khng kh c nhit 380C v m 60-70%. Nu lm

ho nhn to, khng kh c nhit 46-490C v m 28-30%. Trong qu trnh lm

ho cn m bo lu thng khng kh lm gim m xung quanh l ch v

cung cp oxy cho qu trnh h hp.Vn tc lu thng khng kh thng l 100-

150m/pht.

Cht lng l ch khi lm ho cn ph thuc vo ng u ca l ch v nongi khc nhau th khnng bay hi nc khc nhau, l ch cng nonbay hi nc

cng mnh.

Tiu chun nh gi mc lm ho l ch nh sau: T ll ch c lm ho ng mc > 80% l ch ho loi tt . T ll ch c lm ho ng mc 70-80% l ch ho loi trung bnh. T ll ch c lm ho ng mc 70% l ch ho loi xu.

3.2.2.3/Nhng bin i ca nguyn liu ch hi c lm ho

Bc hi nc: khi lm ho, nc s bc hi v n s i qua cc mao qun di lch ra ngoi lm cho l ch mm v do dai hn. Khi lng v th tch nguyn liu

ch gim. Qu trnh ny chia lm ba giai on:

Bc hi nc t do: tc bc hi nhanh, chim 15 20 % tng lng ncc trong nguyn liu.

Tc bc hi chm v nc cc dch bo b cn tr bi cc dch keo ctrong l ch.

T bo mt kh nng hot ng bnh thng, lng nc bay hi tip tc gim.Qua ba giai on ny ta thy khng th lm ho nguyn liu ch giai on cui

vi tc ln v nh vy s lm chy nguyn liu do tc bay hi trn mt


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nguyn liu ch khng ph hp vi tc dch chuyn ca nc trong h thng ng

mao qun trong mi phn ca cc m l.

Cng ko di thi gian lm ho, cht lng ch thnh phm s gim do hm lngtanin c trong nguyn liu ch gim.

Trong qu trnh lm ho, hm lng clorofin trong nguyn liu ch gim, iu nyrt c li trong sn xut ch en v mu xanh ca clorofin s lm cho mu sc ca

nc pha ch en khng p.

Trong qu trnh lm ho, hm lng vitamin C gim (cht chng oxy ha), do lm tng qu trnh oxy ha sc t antoxianidin to ra nhng sn phm tan c

trong nc lm cho mu sc ca nc pha ch en tr nn p.

Qu trnh lm ho lm tng kh nng hot ng ca cc enzyme, c th: Theo ti liu ca A.Cursanp,trong thi gian lm ho hot tnh ca enzyme

glucozidaza tng t 100-200%, hot tnh ca enzyme invertaza tng 50-70%.

Theo ti liu ca Vivrxvi v R-Vrnxvai hot tnh ca enzymeperoxidaza thay i trong khi lm ho l ch nh sau: l th 1 v tm tng

12%, l th 2 tng ln 55,5%, l th 3 tng 144,2%.

Qu trnh lm ho ch yu l qu trnh vt l, nhng bin i sinh ha xy ra trong

qu trnh ny cng c nhng khng nhiu lm.

3.2.2.4/iu in thut

Nhit v m tng i ca khng kh (kk): hai yu t ny nh hng ln ntc lm ho. Nu lmho chm th cht kh tn hao t 4 5 %.

Nu kkthp th tc lm ho nhanh, nhng nu thp qu th vic lm ho skhng u. Thc t nu lm ho t nhin th kk< 60 %. Nu lm ho nhn to

th kkt28 30 % l tt. Nu nhit cao, tc lm ho s nhanh, nhng nu nhit qu cao s nh

hng n hot tnh ca cc enzym c trong nguyn liu v nhit cao, cc

cht hng to thnh s khng tch ly c, cc cht bay hi c mi thm b


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tn tht lm gim cht lng ch thnh phm. Do , nhit lm ho thng

l 40 450 C.

iu kin lu thng khng kh: lu thng khng kh nhm mc ch gim m cami trng lm ho. Trong qu trnh lm ho, m trong nguyn liu ch thot ra lm

mi trng lm ho nhanh chng bo ha nc. V th cn phi lu thng khng

kh ca mi trng lm ho tng tc lm ho ng thi cp cho nguyn liu

ch mt lng oxy cn thit cho qu trnh sinh ha (du t) xy ra trong qu trnh

ny. Ngi ta khng ch tc lu chuyn khng kh khong 2m/s.

ng nht ca nguyn liu: tc thot hi nc nhng phn non, gi canguyn liu ch c khc nhau, do trc khi lm ho cn phi phn loi v nguyn

liu non thng ho trc.3.2.2.5/ Cc phng php lm ho

Ch c lm ho theo hai phng php ch yu:

Lm ho t nhin. Lm ho nhn to.

Lm ho tnhinHo trong nh hoc trong bng rm: Yu cu din tch nh xng phi rng, v

thi gian ho iu kin ny phiko di t 17- 24 gi mi c

mt m.

Ch c ri mng vi lng

ch t 2- 2,5 kg ch ti/m2, trn

nn nh sch, thong kh hoc trn

cc gin tre na, li kim loi, sau

2-3 gi phi o r mt ln, cho

ti khi mc ho t yu cu th

a i v. Ho ch bng cch ny

th ch ho u nhng thi gian

ko di, tn nhn cng, tn din tch, Dy chuyn ho ch


31/47



nn ch s dng kt hp khi c iu kin.

Lm ho nhn toHo bng my

Tni thu nhn, bo qun, ch ti c chuyn vo bng ti np ca my ho,

chiu dy lp ch trn bng ti ph thuc vo tc ca my, thng dy t 18- 22 cm.

Dung lng tc thi trn 5 bng chuyn t 1500- 2250 kg ch bp ti.

My c c kh ho kiu bung kn, c 5 tng bng ti li chun lm vic mt

mt trn. Ch c lm ho theo nguyn tc dng song song (cng chiu) gia khng kh

nng v ch. Lu lng gi nng thi vo my t 55000- 60000 m3/gi.

Gi nng c trn vi khng kh lnh bung ho kh v c qut y vo

bung my ho tng trn cng v thot ra tng cui. My c 4 tc vn hnh, tng

ng thi gian ho t 2- 3- 4- 6 gi, cng sut t 13- 15 tn ch bp ti/ngy (500- 800

kg/gi)

Ho hcTni thu nhn ch c ri ln mng lm ho, dy lp ch ri t 25- 30 cm.

Cn m bo ch c ri u, ti xp, phkn li, ch t ri mng hn, phi r ti,

trnh dnh bt vo nhau. Khi ri xong, khng nn cp nhit ngay m phi bt qut lm

mt nguyn liu trong vng 10- 20 pht. Nhit khng kh nng a vo hc ho t 35-380C, m khng kh khong 40- 50%.

Khi lm ho, nh k sau 1- 2 gio ch 1 ln (dng tay o), ln u lt p, ln

sau o tung, m bo ti xp, tng mc ho u cho ch.

Ch : Thao tc khi ri v o r cn trnh lm dp nt ch ti. Mi mng ch u

c biu k theo di thi gian bt u ho, tnh trng ch ti quyt nh thi im kt

thc ch ho nhm m bo cht lng v th tthu ch a sang v.

Khi kt thc ho ch, phi qut mt cho ch ho trong thi gian 30 pht, sau mivn chuyn ch ho sang v. Ht m ho phi v sinh dn ht ch ho ca mc, trnh

ln sang m sau.


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3.2.2.6/Kim tra qu trnh lm ho vic kim tra qu trnh lm ho c thc hin

bng cch ly mu i din ca nguyn liu ch em lm ho ri tin hnh xc nh

m cn li ca nguyn liu ch sau khi lm ho.

3.2.3/ V ch v sng ch v

3.2.3.1/ Mc ch

V ch lm dp cc t chc t bo cc m lm cc thnh phn trong l ch thotra b mt ca l ch sau khi sy cc dch bo s bm ln b mt l lm cho cnh

ch ng nh hn v d dng ha tan vo nc pha to ra hng v c bit ca ch

en. Hn na, do dch bo thot ra ngoi nn tanin v cc hp cht hu c khc c

iu kin tip xc vi oxy khng kh xy ra qu trnh oxy ha to ra mi v, hng

v mu sc ca sn phm. V lm cho l ch b cun li, to ra nhng bp ch xon nn hnh dng p, gim

th tch, d dng cho vn chuyn v bo qun.

Trong khi v, do ma st gia cc l ch vi nhau hoc gia ch vi v my s lmpht sinh ra nhit, v th vic sng ch v nhm mc ch lm ngui khi ch sau

khi v.

Sng ch v cn nhm mc ch phn loi to iu kin thun li cho nhng lnv tip theo v cho qu trnh ln men sau ny.

3.2.3.2/u cu

Sau ba ln v, t l l ch b dp phi t 72 85 %. ln v cui cng, lng tanin trong l ch khng c gim qu 25 30 % (+/_ 5

%) so vi lng tanin c trong nguyn liu ch.

T l ch vn thp, cnh ch xon cht nhng phi thng v nh.3.2.3.2/Nhng bin i y ra hi v chTrong khi v, cc thnh phn trong ch ho u c nhng bin i ng k:

Khi t bo l ch b v dp th lng oxy thm nhp vo nguyn liu ch tng gpba ln so vi khi cha v. iu ny c th nhn thy qua s oxy ha mnh tanin

trong nguyn liu ch di xc tc ca cc men oxy ha to nn cc sn phm


33/47



mu. Sau ln v I, mu l ch ho t xanh vng chuyn sang mu hung hung v

sau ln v th II, III chuyn sang mu ng .

Trong qu trnh v do lc ma st v nhit sinh ra ca phn ng oxy ho, nhit khi ch tng ln 4-50C. Stng nhit khng u lm cho qu trnh oxy ha xy

mnh v cc b, nh hng xu n phm cht ch. lm gim nhit khi l v

iu chnh qu trnh oxy ho xy ra u n ng mc, ngi ta khng v ch lin

tc qu lu m v ch nhiu ln. Sau mi ln u c sng phn loi v lm ngui

Trong qu trnh v, lng tanin gim lin tc, nu trong ch ho hm lng tanin l23,6 % th sau ln v I s cn 23,3 %, sau ln v II cn 19,8 % v sau ln v III cn

17,5 %.

Trong qu trnh v, hm lng clorofin gim r rt, nu xem hm lng clorofintrong ch ho l 100 % th sau khi v ba ln, hm lng clorofin ch cn 30 %. iu

ny rt thun li cho sn xut ch en.

Trong qu trnh v, hm lng cc cht bay hi to hng thm tng ln r rt.Trong qu trnh ny c s tch ly cc sn phm d bay hi nh: benzaldehyt,

benzylphenol, hexanol...

Hm lng pectin gim trong khi v ch. Trong ch ho, hm lng pectin khong3,4 %, sau khi v cn 2,2 %. Nguyn nhn l do c s ln men xy ra trong khi v

ch, mt phn hydrat pectin bin thnh axit pectin lm cho hm lng pectin gim.

Hm lng vitamin C cng gim rt nhiu sau khi v ch. Ngoi ra, trong khi v ch ho c nhng bin i vt l quan trng, nhng phin l

ch xon cht, thng v nh, nh bng to nn ngoi hnh p cho sn phm.

3.2.3.3/ K thut v ch: C hai phng php v ch

V ch th cng: Cho ch ho vo trong cc ti vi tha ri dng tay v, phngphp ny t c dng trong sn xut ch en.

V ch c gii: Phng php ny cho cht lng sn phm cao, nng sut ln. Qutrnh v c thc hin trong nhng my v, my v ch gm mt thng hnh tr

cha ch lm ho, bn v t y thng c b tr ca tho ch v, trn bn

v c nhiu thanh g to nn nhng lc xon cun khi ch khi v. Nh c h


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thng g m thng v c th chuyn ng trn, lui ti trn mt phng ca y

thng v, bn v ng yn hoc cng chuyn ng trn, lui ti trn mt phng song

song vi mt phng ca y thng v nhng theo hng ngc li.

Hin nay, ngi ta thng s dng cc loi my v sau: My v ch m: My ch khng c b phn

bn p ln khi ch ho trong thng v.

My v ch kn: c b phn bn p ln khich ho trong thng v.

My v ch tc dng kp: My v ch mthng v v bn v u chuyn ng nhng

ngc chiu nhau. My v ch tc dng n: l my v ch ch

c thng v chuyn ng.

3.2.3.4/ Sng ch v

Trong qu trnh v, nhit trong khi ch v tng ln do cc lc ma st gia ch

v thit b v, do cc phn ng sinh ho khi ln men c to nhit. Mt khc ch cn b

vn cc do tc dng kt dnh ca dch ch, nha ch lm cho ch kh b v dp v km

xon. Do vy, phn loi ch v nhm mc ch:

Lm gim nhit khi ch v. Tng cng b mt tip xc khng kh, nhm cung cp oxy qu trnh oxy ho

ca enzyme pht trin ng u.

Phn loi khi ch v theo non, gi v kch thc to, nh thnh 3 phn: Phn I + II (phn lt sng nh v non), phn III (phn trn sng to, gi) x l

v li, ln men v sy ring.

Lm ti khi ch v b vn cc trong khi v.My sng phn loi phi c lm sch thng xuyn, khng cho l ch, nha

ch bm dnh vo li sng lm cho ch nhim mi chua, thiu.


35/47



3.2.3.5/u cu thut

Lng ch ho a vo my v: Ty thuc vo th tch ca thng v, trong thc t,lng ch ho a vo thng v chim 75 85 % th tch ca thng v. Nu lng

ch ho a vo my v qu nhiu th vic v ch s khng u v tn nhit s

khng tt, gy nh hng n cht lng sn phm. Nu lng ch ho a vo

my v qu t th nng sut my v s gim v p lc v c to ra do trng lng

bn thn khi ch s gim nn kh lm cnh ch xon kt p.

Tc quay ca mm v: tc quay ca mm v c nh hng n cht lngthnh phm. Ty theo cht lng ch ho em v v iu kin ca phng v m

khng ch tc quay ca mm v cho thch hp. Nu tc quay ca mm v qu

ln th cnh ch d gy vn nhng c u im l rt ngn c thi gian v v chtlng ca sn phm tt hn. Ngc li, nu tc quay ca mm v nh th c u

im l cc l ch khng b t on nhng thi gian v s ko di, nng sut v

ch thp, ch v trong my d pht nhit gy nh hng n cht lng sn phm.

Do , nu my v v phng v c h thng thng gi tt, c th dng tc v

nh, ngc li, phi tin hnh v nhanh.

Thi gian v: nu tc v ln th thi gian v gim. Tuy nhin cn phi lm thno qu trnh v ch t c nhng yu cu ra v dp t bo, t l vnnt...L ch gi th cn thi gian v ln hn l ch non. nc ta thng dng ch

v nh sau:

Ln v I II III

Tc (v/pht) 50 55 60

Thi gian (pht) (40 45 pht cho mi ln v)

p lc v: nu p lc v qu ln th l ch d b tn thng, ch vn nhiu, ngcli nu p lc v qu nh th qu trnh v s khng trit , mu nc pha ch en

thnh phm s nht, b ch c nhng m xanh. Do , trong thc t, ln v I,

ngi ta v m (khng c p lc) v trong ln v II, III th v kn (c p lc) xen k

vi v m nhit sinh ra trong qu trnh v d dng tn i.


36/47



3.2.3.6/Kim tra cng on v ch v yu cu thut ca phng v ch

Nhit ca phng v ch c nh hng rt ln n cht lng ca sn phm ch

en, do , cn phi khng ch nhit ca phng v ch vo khong 20 240 C. Ngoi

ra, tc dng ca men oxydaza trong nguyn liu ch ph thuc rt nhiu vo s c mt

ca oxy trong phng v, do cn phi lu thng khng kh trong phng v; ng thi

thun li cho qu trnh bin i ha hc ca ch v, cn khng ch m trong phng

v khong 95 98 % bng cch phun m.

Cht lng ch v c kim tra bng ch tiu dp ca t bo, sao cho ln v

cui dp t bo phi t t 75 85 % tr ln. Ngoi cch kim tra cm quan ( xon

cht v mc dch chy ra mt ch v) ngi ta cn kim tra bng phng php ha

hc. Phng php ny da trn nguyn tc l cho l chv vo dung dch kalibicromat

10 % trong thi gian 5 pht. Dung dch ny s lm xm nhng ni no l ch b dp (do

tc dng vi tanin), t ta c th xc nh c t l dp ca t bo trong qu trnh v.

3.2.4/ Qu trnh ln men ch en

3.2.4.1/ Mc ch ca qu trnh ln men

Ln men l giai on quan trng nht trong qu trnh ch bin ch en, y l qu

trnh oxy ho su sc mt s thnh phn ca ch v nhxc tc ca nhm enzyme oxy

ho kh v c s tham gia ca oxy khng kh. Trong giai on ny phi to c cciu kin nhit , m v oxy khng kh thch hp nht cho enzyme oxy ho hot

ng xc tin cc bin i ho hc cn thit v quyt nh nn cht lng, hng v

c bit ca ch en thnh phm.

Ton bqu trnh ln men c chia lm 2 giai on chnh :

Giai on 1: K tkhi v n khi v xong. Trong thi gian ny di tc dngca enzyme oxy ho catechine ca tanin ch oxy ho chuyn thnh

orthoquynone, l cht c hot tnh mnh c th oxy ho cc cht hoc ngngt vi nhau to thnh cc sn phm c mu.V vy khi v, l ch mu xanh

chuyn sang mu hung hung (nu nht ).

Giai on 2: k tkhi v n trc khi sy vi thi gian khong 2-3h. Nguynliu ch phng ln men lun c phun hi m v iu chnh nhit nht


37/47



nh thch hp cho qu trnh ln men. Trong thi gian ny ch chuyn t mu

hung hung sang mu ng v tohng thm d chu, v ch khng cht gt

m mt du .

3.2.4.2/u cu thut Ch sau khi ln men phi t nhng yu cu sau:

L ch mt i mu xanh, c mu Mi hng xanh mt i, c mi thm du Khng cn v cht, c v m du Hm lng tanin gim 50 % so vi lng tanin c trong nguyn liu ch. lc ny c

th kt thc qu trnh ln men.

3.2.4.3/ Nhng bin i xy ra trong qu trnh ln men

Cc cht ho tan: Trong qu trnh ln men cc cht ho tan bthay i rt ln do schuyn ho cc cht ho tan thnh khng ho tan v do tc dng vi protein. Nhn

chung hm lng cht tan gim t 42.9% sau khi lm ho xung cn 31.3% sau khi

ln men .

S bin i ca tanin: Hm lng tanin trong l ch gim dn trong qu trnh lnmen. S gim hm lng tanin l do qu trnh oxy ho di s xc tc ca enzyme

polyphenoloxydaza hnh thnh cc cht mi c v cht du v to nn cht mu.

S tch luhm lng Teaflavin c xu hng lin tc gim dn mt cch u n,

iu chng t c s chuyn ho mnh m bin Teaflavin l cht c mu vng

sng thnh Tearubigin.

Trong thi gian ln men hm lng tanin gim 50% so vi ban u. Hm lng catanin dng poliphenol catechine c vng gim t8.91% khi v n cn 2.77% sau

khi ln men. Cn tanin ring c v nht nh th gim i ng k t 9.06% khi v

xung 5.96% sau khi ln men .

Bin i ca du thm v s to thnh hng thm ca ch en thnh phm: Trongcc qu trnh ln men hm lng du thm thay i rt ln v t c cc i sau

3-4h ln men, t lm thay i cht lng v hng thm ca ch thnh phm.

Sthay i ca protein v cc cht khc trong khi ln men: Trong qu trnh ln menprotein phc tp khng tan bthay i thnh protein ho tan v cc aminoacid. Cc


38/47



aminoacid tham gia to thnh cc andehit thm ca ch. Mt khc, trong qu trnh

ln men cc monosaccarit tng ln cn saccaroz gim xung gp phn vo to

hng thm ca ch khi sy.

S thay i ca pectin trong khi ln men: Hm lng pectin ho tan gim xungcn pectin khng tan tng ln.

3.2.4.4/ Cc yu tnh hng n qu trnh ln men

Qu trnh ln men ch en chu tc dng rt ln ca nhit , m, v thnh phn

khng kh xung quanh.

Nhit : Nhit c nh hng rt ln n xc tc ca enzyme v tc ca ccphn ng ho hc. i vi sn xut ch en, nhit thch hp cho qu trnh ln

men l 20-300C. Nu nhit cao qu sc ch s xc tc ca enzyme, ngc li

nhit thp qu th lm chm qu trnh xc tc.

m: L ch sau khi v em ln men yu cu phi c m thch hp l 60-62%v m khng kh trong phng ln men phi cao 95-98% trnh lm l ch b

ho v lm cc phn ng ho hc b chm li.

Khng kh : Qu trnh ln men cn c cung cp mt lng ln khng kh sch,nu thiu khng kh ch d b hi. Trong khng kh nu thnh phn CO2 nhiu cng

gy nh hng xu ti qu trnh ln men. c bit kh H2S ch cn mt lng nhcng c th lm cho qu

trnh ln men bnh ch.

3.2.4.5/ K thut ln men

Ch sau khi c v chia

lm 3 loi c ri ring vo

khay g v t vo phng ln

men. dy ca tng phn chc quy nh nh sau: Phn

ch loi I dy 4cm , phn ch

loi II dy 6cm , phn ch loi

III dy 8cm .D chu n ln men ch


39/47



Khi xp vo cc khay cn ch xp xen km bo thong kh trong thi gian

ln men. Nhit v m khng kh trong phng ln men l t0 = 22-24oC v m 95-

98%.

Trong thi gian ln men, c 6-8 pht yu cu thng gi phng 1 ln. Tng thi gian

ln men l 4-5h k t khi bt u v v 2-3h k tkhi a ch vo ln men .

kt thc qu trnh ln men ngi ta da vo nguyn tc sau:

Khi ch ln men c mu ng , c hng thm v mi v d chu th c tha

ch vo sy .

Trong thi gian ln men, nhit ca khi ch tng dn v sau khi t cc ith bt u gim xung. Giai on ln men c kt thc khi nhit bt u

gim.

Trong qu trnh ln men hm lng tanin trong ch gim dn, tu theo tng loich m ngi ta cn phi gi hm lng tanin cn li sau qu trnh ln men

trong mt gii hn nht nh.

3.2.4.6/Kim tra giai on ln men

C hai cch kim tra: kim tra bng phng php cm quan v bng phng php

ha hc. y ch gii thiu mt vi phng php n gin nh sau:

Theo di nhit ln men: khi nhit khi ch t cao nht bt u gim xungth ch c ln men y v c th kt thc qu trnh ln men.

Theo di mu sc ch ln men: nu ch c mu ng th ln men y , munu th ln men qu mc v mu lm m xanh chng t ln men cha y ,

trng hp ny cn tm r nguyn nhn khc phc, c th do nhng cng

an trc nh lm ho, v.

Theo di mi v ch sau ln men: nu mi thm du l ln men ng mc, nu cmi chua l ln men qu mc, cn nu vn c mi hng xanh th ln men cha t.

3.2.5/ Sy ch

3.2.5.1/ Mc ch v ngha

nh ch cc qu trnh hot ng ln men. Lm gim m lm kh ch.


40/47



To iu kin cho qu trnh vn chuyn v bo qun ch c d dng. ng thi sy cn cnh nhng cht to thnh do qu trnh ln men v gi cht

tan trn b mt l ch.

Di tc dng ca nhit sy, cc hng thm ca ch c pht huy v mt scht thm mi c to thnh.

3.2.5.2/ Yu cu

Ch phi c sy u, kh v khng c mi kht, m cn li t 3 5 %

3.2.5.3/ Nhng bin i xy ra khi sy kh

Trong qu trnh sy ch, di tc dng ca nhit v s oxy ho m mu ng

ca ch ln men chuyn sang mu xm, sau mu en bng, mt s cht thm c

mi to chn c to ra giai on ln men b mt i, thay vo l hng thm cbit ca ch en. Trong qu trnh sy, si ch kh v xon li, v trong khi sy cng xy

ra bin i ho hc m ch yu l qu trnh oxy ho v caramen ho.

Ngoi ra cng vi lng m thot ra, lng du thm trong ch cng b tn tht,

ch yu l cc hp cht thm dbay hi v cc este ca du thm.

Ngoi du thm ra, cc hp cht nit trong c cafein cng gim i tung i r.

Trong thi gian sy, hydropectin gim i khong 1.59% trong khi protopectin

gim i 0.77%, c bit ru metylic c trong ch ln men th sau khi sy hu nh khngcn na.

Cc vitamin ca ch, c bit l vitamin C b ph hu kh nhiu trong qu trnh sy.

Hm lng vitamin C b gim rt ln trong qu trnh sy. Nu khi ln men l 81.4mg%

th sau khi sy ch cn 18.6mg%.

Trong qu trnh sy, di tc dng ca nhit, tuy hm lng ca glucoza, saccaroza

v tinh bt gim i khng nhiu lm nhng nhng bin i ca chng c ngha quan

trng i vi cht lng ca ch, bi v do kt qu ca s caramen ho m mt phn

gluxit b ho tan trong qu trnh pha, to nn nhng mi thm c o ca ch kh.


41/47



3.2.5.4/ Cch tin hnh sy

Cu to

1: L t

2: ng khi

3: Calorifer

4: Qut

5: Bung sy

6: Bng ti sy

7: Bng ti cp liu

8: Ca tho ch

Nguyn tc lm vic Thit b sy ch

Qut thi khng kh nng t calorife vo bung sy tdi ln, bung sy l mt

hp kim loi c 4 bng chuyn. Nguyn liu nhbng ti cp liu 7 vo bng chuyn trn

cng ri ln lt i xung pha di. Sau khi qua khibng chuyn di cng th ch ra

khi my sy theo ca 8. Nng sut ca my thng l 120 kg ch/gi, vn tc khng kh

nng 0,5 m/s. Tc bng chuyn 1 tng 47% v bng chuyn 2 tng 20% so vi bng

chuyn 3, tc bng chuyn 4 gim 20 % so vi bng chuyn 3. V th, dy ca ch

ri trn bng chuyn stng tbng chuyn 1 n bng chuyn 4, ph hp vi thc t lch s kh dn t trn xung di.

Khi sy ch, ch phn III c a vo sy trc, ch phn I, II sy sau. Tuiu

kin nguyn liu, nhit sy m iu chnh dy lp ch v tc sy cho ph hp.

Thng thng ch non v ch t ri dy hn ch gi.

Cn phi iu chnh cc thng s ca qu trnh sy cho hp l :

Nhit v thi gian sy: Nhit sy cn cao dit enzyme v lm kh chnhng cng trnh nhit qu cao gy mi ch chy. Thng thng ngi ta sy2 ln vi nhit nh sau :

Sy ln 1: Nhit 90-950C vi thi gian sy l 12-15 pht, m sau khisy l 18-20%.


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Sy ln 2: nhit 80-850C vi thi gian sy l 12-15 pht, m saukhi sy ln 2 l 3-5%.

Gia 2 ln sy ch c ri mng, lm ngui v ch phn phi li m cho

ng u, trnh hin tng kh cc bv trong t ngoi th kh. Ngoi nhit sy trn

ngi ta cn p dng sy nhit 1280C, phng php ny sy nhanh, nng sut cao

nhng kh khng ch cc ch tiu k thut.

Tc khng kh sy: m bo thi gian sy v nng sut ca my sy,lng khng kh vo thit b thch hp l 16000m3/hv m bo tc chuyn

ng ca khng kh qua lp ch l 0.5m/s. Nu lng khng kh sy t th tn tht

hng thm t nhng lng nc bay hi chm v nh hng xu ti cht lng

ch thnh phm.

Ch : Tt c cc loi ch sau khi sy kh phi ngui mi c ng vo bao,cn bo qun sau t nht 1 ngy mi c tin hnh phn loi trnh gy vn do ch

kh rn sau sy.

3.2.5.5/ Cc yu tnh hng n qu trnh sy

Nhit sy

Nu tng nhit sy ch khong 140oC th slm tng vn tc sy, ng thi lm

gim thi gian sy 40-50%, nh vy, s gim c kch thc thit b, gim c githnh sn xut thit b, mang li hiu qu kinh t v s dng nhin liu, nng lng...do

gim c gi thnh sn xut. Tuy nhin ng vquan im cht lng sn phm th

phi kn tnh cht v cht lng ca ch, ngha l phi chn nhit sy thch hp cho

tng giai on sy v cho tng loi sn phm. Nhit thch hp ca sy ch en nm

trong khong 80-85oC. nhit sy nhhn 80oC c th do nhng qu trnh sinh ho

c li cho cht lng ca ch xy ra cha hon ton, cn nhit sy ln hn 85oC m

cht lng ch b gim l do s tn tht (thng hoa) mnh m cc tinh du c trong chnguyn liu hoc sinh ra trong qu trnh ln men.

Trong thc t sn xut, tutheo iu kin c ththng ngi ta cn c vo mc

ln men quy nh nhit sy thch hp. Nu ch ln men ng mc th phi

dng nhit cao sy nhanh, ngn nga s ln men qu mc, lm cho v ca ch nht


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i. Nu mc ln men cha nhng do iu kin sn xut yu cu phi sy th nhit

sy phi thp. i vi ch en, ngi ta thng dngphng php sy hai ln.

nh hng ca khng kh (tc nhn sy)

Nu vn tc ca khng kh sy tng slm tng cng bc m, gim c thi

gian sy. Nhng nu vn tc sy tng qu mc s lm cho qu trnh kh qu nhanh, gy

nh hng n hnh dng v cht lng ca ch, ng thi cn gy tn tht vhng

thm ca ch v mc no gy tn tht nhit do khng kh mang ra ngoi.

Nu nhit sy khng i ( to=80oC), mt ca ch trn bng chuyn sy c

nh (1.5 kg/m2) th cng bc m ca lp ch sy ph thuc vo vn tc chuyn ng

ca khng kh sy.

Trong sn xut m bo cht lng ch, thi gian sy v nng sut ca thit b,

cng nh tn tht nhit khng cn thit, thng ngi ta chn vn tc chuyn ng ca

khng kh sy trong thit b sy cng nh xuyn qua lp ch


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- Kim tra cm quan bng cch dng ngn tay nghin ch sy thnh bt vn m khng

thy dnh tay l sy ng mc.

3.2.6/ Phn loi ch bn thnh phm

Ch sau khi sy c a qua sng phn trn v sn bng phn loi ra cc loi

ch c kch thc khc nhau. i vi cc loi ch to ngi ta cho qua dao ct ri li a

ln sng phn loi tip. Sau khi phn loi thnh nhiu ckhc nhau, ta ch nh s v

xp thnh tng chng ring. T cc cch trn ngi ta em pha trn v c cc loi

ch khc nhau:

Ch cnh hay ch si gm c: OP, P, PS. Ch mnh hay ch gy c: BOP, PB, BPS.

Ch vn gm: F, D (dust).Nhng ch khi phn loi ch:

Sng ch phi thng tho, nhn bit c v ly mt hng theo yu cu, ngchng loi.

Khi sng ch cng gn c nhiu ch cnh cng tt. Mun vy khi ch vomy sng phi t t, m bo dng ch xung my sng u, lin tc (trnh

qu nhiu hoc qu t) ch khng b ln loi.

Thng xuyn kim tra cc sch nh cli sng a vo my cho phhp.

Khi mun tng ng u v sng gn i vi 1 mt hng ch no th lpsong song hai sli ging nhau lin k.

Nhng phn ch ln nhiu tp cht, phi nht v tch tp cht trc khi emct - cn. Nhng phn ch ln nhiu ru x, phi cho tch ru x qua my bng

ht tnh in hoc sng tay.

Cc my sng sch u phi c lp bnam chm tch tp cht st.3.2.7/ u trn ch

Ch sau khi sy c ng trong cc bao vi hoc bao PE, cn b KCS ly mu

tng bao ch b vo ca khay g theo tng stng ng sau tin hnh nht, chn

trn khay g tng mt hng ch theo tiu chun v cho ra thc n phi trn ch.


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Cn c theo n u trn v shng dn ca KCS, tin hnh vic u trn ch.

Ch trn nhng bao ch cng tn, c hnh dng gn ging nhau, hoc nhng loi ch

c quy nh u trn vi nhau cho ra mt mt hng ch c ngoi hnh v cht lng

ng nht, t tiu chun theo yu cu.

Vic u trn c tin hnh th cng hoc trn trong my trn thng quay, tc

quay ca thng t 4-5 vng/pht.

3.2.8/ ng thng v bo qun

3.2.8.1/ ng thng

Sau khi trn ch xong ,ch c em ng thng v bo qun.Thng lm bng g

dn c lt giy thic, giy chng m v lp giy bn trng mn l lp tip xc vi ch.

Nhn hiu dn vo thng ch phi ghi r: Ni sn xut , ni nhn hng, khi lng

ch trong thng v ngy ng thng.

V trong qu trnh bo qun trc khi ng thng, ch ht m trli, v vy yu cu

ch khi ng thng phi c m l W


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Cc bao ch trong kho c xp nm, cch nn kho 10-20 cm, cch tng 50 cm v

gia cc l c li i li kim tra v vn chuyn d dng.

Kho bo qun ch phi kh ro, sch s, khng c cng cc vt t hng ho

khc trnh ch nhim mi l, phi thong kh, nhit khng kh khng c qu cao,

khng nh nng mt tri chiu trc tip vo ch bo qun, m khng kh khng

di 60%, nu c i kin th nn dng nu c i kin th nn dng iu ho khng

kh trong kho.Kho bo qun ch phi c trang by cc thit b v iu kin phng

chng chy n, phng chng s xm nhp ca cc vi sinh vt lm mt v sinh an ton

thc phm.


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TI LIU THAM KHO1/ TS. Trnh Xun Ng, Cy ch & kthut chbin ch, NXB Khoa Hc K Thut v

Cng Ngh.

2/ Ngc Qu, Cy ch Vit Nam: sn xut, chbin, tiu th3/ Ks.Bi Tht - PGS.TS V Khc Nhng, K thut gieo trng chbin ch v cph

4/ K thut ch bin ch (http://voer.edu.vn/content/m10954/latest/),

5/www.tailieu.vn

6/www.ebook.com

7/http://thuvienluanvan.com/decuong/DAN317.doc

8/http://voer.edu.vn/content/m10955/1.1/
http://voer.edu.vn/content/m10954/latest/http://voer.edu.vn/content/m10954/latest/http://voer.edu.vn/content/m10954/latest/http://www.tailieu.vn/http://www.tailieu.vn/http://www.tailieu.vn/http://www.ebook.com/http://www.ebook.com/http://www.ebook.com/http://thuvienluanvan.com/decuong/DAN317.dochttp://thuvienluanvan.com/decuong/DAN317.dochttp://thuvienluanvan.com/decuong/DAN317.dochttp://voer.edu.vn/content/m10955/1.1/http://voer.edu.vn/content/m10955/1.1/http://voer.edu.vn/content/m10955/1.1/http://voer.edu.vn/content/m10955/1.1/http://thuvienluanvan.com/decuong/DAN317.dochttp://www.ebook.com/http://www.tailieu.vn/http://voer.edu.vn/content/m10954/latest/

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