Nam Men Banh Mi.hoan Chinh

8/7/2019 Nam Men Banh Mi.hoan Chinh

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Mn: CNG NGH LN MEN GVHD: NG LM TUN ANH

ti: CN SN XUT SINH KHI NM MEN BNH M 1

LI MU

Nu nhChu ch yu s dng go, th Chu u con ngi li dng

la m lm lng thc chnh. T la m, ngi Chu u sn xut ra bnh m, mt

sn phm truyn thng ni ting bn cnh bia, phomat,Do vai tr quan trng cabnh m i vi loi ngi nn quy trnh sn xut bnh m rt c quan tm v

khng ngng c con ngi ci tin.

Tuy khng hiu r nguyn nhn nhng con ngi bit cch to ra nhng

bnh men b sung vo quy trnh sn xut bnh m. n u th XIX, nm men bia,

nm men thi t nh my ru bia c con ngi s dng lm bnh m.

Cui th k XIX, nhiu ci tin k thut nh h thng thng kh ( nc Anh ), k

thut ly tm tch men ra khi mi trng tng trng (M) c dng sn

xut men bnh m. Con ngi ch lm theo thi quen, khng l gii c ti sao lm

nh vy th cht lng bnh m s tt hn. Sau i chin th I v th II, vic sn

xut nm men Sacharomyces v Candida pht trin mnh.

Ngy nay, vi s hiu bit v vi sinh vt hc, con ngi phn no gii

thch c nhng qu trnh xy ra trong quy trnh sn xut bnh m. T cho thy

c tm quan trng ca vic sn xut bnh men c nh hng trc tip n chtlng sn phm cui cng.

bi tiu lun ny, nhm em ch tp trung tm hiu loi nm men dng

trong sn xut bnh m bng vn kin thc t i v cc ngun ti liu ng tin cy

khc. Trong qu trnh tm hiu khng trnh khi nhng sai st v ni dung cng

nh cch trnh by. V vy, nhm em rt chn thnh cm n v sng gp kin

ca Thy cng cc bn.


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NI DUNG

Chng 1

TNG QUAN

1.1 Gii thiu chung v sinh khi nm men trong sn xut bnh m.1.1.1 Tn gi. [1]

Saccharomyces l mt chi nm men c s dng rng ri trong ngnh

thc phm nh lm bnh m, sn xut cn. Saccharomyces c ngha l nm ng

v l loi vi sinh vt duy nht uc sn xut vi quy m rt ln trn th gii.

1.1.2 Vi nt lch sv nm men trong sn xut bnh m. [1]

Nm men s dng trong sn xut bnh m l nm men Saccharomyces

cerevisiae. Loi ngi s dng nm men lm nbnh m t trc khi bit c

hnh thi, cu to v c tnh sinh l, sinh ha ca chng.

Lc u, ngi Chu u bt m ln men t nhin v lm bnh. Ngi ta

thy nu bt m ln men t nhin th khi lng bt s nhiu hn v khi nng

bnh s c mi thm v v chua hp dn, nhng ngi ta khng bit ti sao li th.

Sau , vo th k 17 ngi Chu u khng cho bt m ln men t nhin

na m s dng nm men bia nho bt. Kt qu ca vic lm ny l khi bt nu hn, bnh thm hn, c bit l khng chua nh cho t nhin.

Nm 1850 bt u giai on rt quan trng trong s pht trin ca cng

ngh sn xut nm men bnh m. Ngi Chu u bit sn xut sinh khi nm

men bnh m dng nho (dng paste). Lc u h ly cn nm men t qu trnh sn

xut ru, chuyn cn nm men ny sang thng ng nm men, ra sch nm men

bng nc lnh v a vo my p vt.

Nm 1878, L. Pasteur nghin cu nh hng ca oxy n s pht trin ca

nm men. Kt qu cho thy khi c mt oxy hiu sut thu nhn nm men rt cao.

Kh khn nht trong vic cung cp oxy cho qu trnh ln men giai on ny l

ngi Chu u s dng mi trng nho, do oxy rt kh phn tn u vo khi

nho ny.

Nm 1886, ngi Chu u bt u thay i mi trng. Ngi ta khng

dng mi trng nho na m s dng dung dch nc ng. Bt la m hay i

mch c thy phn thnh ng, sau ngi ta dng nc ng ny sn


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xut nm men. Nm 1900, ngi ta s dng my ly tm tc cao tch nc ra

khi nm men v phng php nui cy nm men c hon thin dn.

Sau , ngi ta thay bt thy phn bng mt r hoc ph liu nh my

ng, nh my bnh ko. Lng ng dng ln men cng gim dn, lulng kh c tng ln tng kh nng h hp ca nm men.

Nm 1916, xut hin nh my u tin thc hin nhng ci tin ny. Nm

1940 nh my men bnh m ln nht Chu u vi cng sut 16500 tn / nm c

xy dng Moscow. T n nay, hu nh nc Chu u no cng c hng chc

nh my ln, nh sn xut nm men bnh m.

1.1.3 c im hnh thi v kch thc. [2]

Nm men saccharomyces c hnh bu dc, gn trn, kch thc khong 6 -

8 m x 5 - 6 m.

Nm men Saccharomyces cerevisiae c hnh cu hay hnh trng, c kch

thc nh, t 5-14 mircomet.

Saccharomyces l loi nm men thuc nhm c thn bo, gm c nm

men chm v nm men ni:

Nm men chm (lager): hu ht cc t bo khi quan st th ny chi ng

ring l hoc cp i. Hnh dng ch yu l hnh cu.

Nm men ni (ale): t bo nm men m v con sau khi ny chi thng

dnh li vi nhau to thnh chui t bo nm men. Hnh dng ch yu l hnh cu

hoc ovan vi kch thc 7-10 micromet.

S khc nhau gia nm men ni v nm men chm: l kh nng ln men

cc loi ng trisaccharide, v d raffinose. Trong nm men chm c enzyme c

th s dng hon ton ng raffinose, trong khi nm men ni ch s dng c1/3 ng saccharose.

Ngoi ra chng cn khc nhau v kh nng h hp, kh nng trao i cht

khi ln men v kh nng hnh thnh bo t. Qu trnh trao i cht ca nm men

chm ch yu xy ra trong qu trnh ln men, cn ca nm men ni xy ra mnh

trong qu trnh h hp, v vy sinh khi nm men ni thu c nhiu hn nm men

chm. Nm men chm c nng enzyme thp hn nm men ni. Kh nng to bo

t ca nm men chm lu hn v hn ch hn nm men ni.


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1.1.4 Thnh phn cu to.[2]

Nm men Saccharomyces thuc h Saccharomycetaceae, ngnh

Ascomycota v thuc gii nm.

Nm men Saccharomyces gm nhng thnh phn ch yu sau:- Vch t bo

- Mng t bo cht: nm st vch t bo, c cu to ch yu l lipoprotein,

gi vai tr iu ha vn chuyn cc cht dinh dng cho t bo.

- T bo cht: gm c mng li ni cht l v tr ca nhiu h thng

enzyme khc nhau, m bo s vn chuyn vt cht cho t bo v cc cu t khc

nhau nh b my golgi, lysosom, khng bo, (cha cc sn phm b phn ct, hay

cht c l c th c hi cho t bo). Nng lng cung cp cho t bo qua nhng

phn ng xy ra trong ty th cng nm trong t bo cht. Trong t bo cht c nhn

cha thng tin di truyn cho t bo v cc thnh phn lin quan trong qu trnh sinh

tng hp v sinh sn ca t bo. Nhn nm men c phn trn l trung th

(centrosome) v centrochrometin v phn y ca nhn c thm khng bo

(vacuole), bn trong cha 6 cp nhim sc th (NST) v bn ngoi mng nhn c

nhiu ti th bm quanh. Ngoi ra cn c ht glycogen, ht m d tr cht dinh

dng cho t bo.

1.1.5 Thnh phn ha hc.[2]

Thnh phn ho hc ca t bo nm men Saccharomyces khc nhau tu

thuc vo iu kin mi trng nui cy, thnh phn cc cht dinh dng trong mi

trng nui cy v tnh trng sinh l ca t bo.

Nm men p c cha 70-75% nc, 25-30% cn li l cht kh.

Nc: bao gm phn nc nm bn ngoi t bo v phn nc nm trongt bo. Lng nc khc nhau tu thuc vo chng nm men, k thut nui v

phng php thu t bo. V d: khi nui trong mi trng NaCl th lng nc

trong t bo gim.

Thnh phn cht kh ca t bo nm men bao gm protein v cc cht c

nit khc chim 50% , cht bo 1,6%, hydratcacbon 33,2%, m t bo 7,6%, tro

7,6%. Thnh phn ca nhng cht ny khng cnh, n c th thay i trong qu

trnh nui cy cng nh qu trnh ln men.


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Hydratcacbon gm: polysaccharide, glycogen, trehalose (12 -12,5%),

mannan (18,7-24,9%), glucan (9,47-10,96%) v chitin . Nhng nghin cu ng

hc v s bin i hydrat cacbon trong qu trnh bo qun nm men cho thy l

glucan, mannan v dng glycogen tan trong kim v axit clohydric l yu t cutrc ca t bo, trong khi trehalose v glycogen tan trong axit acetic, l cht to

nng lng chnh cho t bo. Hm lng trehalose trong nm men c lin quan n

tnh bn vng ca n : lng trehalose cng cao nm men cng bn.

Cht mca nm men l m trung tnh glycerol, photpho lipide, sterol t

do v nhiu sterol, este.

Tro chim 6,5-12% lng cht kh trong nm men v dao ng ty theo

mi trng nui cy.

1.1.6 Cc cht dinh dng cho nm men.[2]

Trong cng nghip vi sinh, mi trng nui cy tt nht l mi trng cho

hiu sut thu hi sn phm cao nht, trong thi gian ngn nht vi gi thnh thp

nht i vi mi chng vi sinh vt.

Ngun thc n ch yu cho nm men l cc cht hu cdng d hp thu

v cc cht v c. Ngoi ra, nm men pht trin bnh thng cn mt lng nh

cc yu t vi lng v cc cht kch thch. Ngun thc n cho nm men rt a dng,

do cn nghin cu ring tng ngun.

1.1.6.1 Nc.

Nc rt cn thit cho hot ng sng ca t bo nm men. Khng c nc

khng th c qu trnh ng ha thc n v qu trnh trao i cht trong cth.

1.1.6.2 Ngun cacbon.

Ngun cacbon l ngun ch yu lin quan n qu trnh trao i cht vchuyn ha nng lng. Nm men c kh nng ng ha hon ton ng glucose,

fructose v mannose. Ngoi ra, ty thuc vo chng ging, nm men cn c th

ng ha hon ton hoc mt phn no ng galactose.

ng disaccharide quan trng cn quan tm ti l saccharose, lactose,

melibiose. Nm men ng ha ln men rt tt maltose v saccharose, ng ha mt

phn hoc hon ton ng lactose. Ring melibiose ch ln men c khi c

enzyme melibiozase.


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Nm men ni ( ln men ni ) ch ln men c 1/3 rafinose sau khi phn

gii ra mt phn t fructose v melibiose. Nm men chm (ln men chm ) c kh

nng thy phn hon ton rafinose do c enzyme invertase v melibiozase.

Cc polysaccharide cn c thy phn hon ton bng axit hoc enzymeth nm men mi c th s dng c.

1.1.6.3 Ngun nit.

ngha ch yu ca ngun nitl cung cp cho t bo nguyn liu hnh

thnh cc nhm amin (-NH2) v imin (-NH-) tng hp nn protein v cc hp

cht khc ca nguyn cht. Nm men ng ha c cc hp cht axit amin v nit

v c. Dng ha hn c l ion NH4+ v ammoniac NH3 vi lng s dng ln

nht l 20 35 mg N2/109 t bo. Ngun nitc coi l tt nht v c ng ha

hon ton l ure:

NH2 CO NH2 + H2O = 2NH3 + CO2

Nm men c th t tng hp axit amin. Tuy nhin, nu cho cc axit amin

vo mi trng th qu trnh sinh sn v pht trin ca t bo s nhanh hn. Nm

men ng ho cc axit amin bng cch amin ha (tch NH3 ra khi cc cht), do

cc ngun nitkhc nhau s c nh hng rt t ti hm lng axit amin trong t

bo nm men.

1.1.6.4 Cc cht khong.

Trong mi trng dinh dng cn phi c mt lng nht nh cc cht

khong m bo cho t bo pht trin. Nu trong mi trng tng hp th cc

cht khong sau y s cn thit cho nm men:

Bng 1.1: Cc cht khong cn thit cho nm men

Cht khong Hm lng (g/l)

K2HPO4

KH2PO4

MgSO4.7H2O

MgSO4.4H2O

1 2

1 2

0.2 0.5

0.02 0.1


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FeSO4.7H2O

ZnSO4.7H2O

CuSO4.5H2O

Na2SO4

CaCl2

0.05 0.2

0.02 0.1

0.01 0.02

0.02 0.05

Nu nng cc cht ny trong mi trng t hn nng ni trn th

qu trnh pht trin s chm li, cn nu nhiu hn th p sut thm thu tng c ch

qu trnh sinh sn.

Phospho rt cn thit cho qu trnh tng hp cc thnh phn nguyn sinh

cht v c trong thnh phn ca coenzyme, dng phospho ha cc hydrocacbon

trong qu trnh oxy ha. Phospho cn tham gia vo cc phn ng nng lng. N

c cung cp di dng mui natri hoc kali. Nu lng phospho t th tng hp

protein gim v tng hp lipide tng.

Kali v natri chim 1/5 3/4 hm lng cht tro. Nu thiu kali hoc natritrong mi trng nui cy th qu trnh pht trin s b chm li.

Magie c kh nng thc y qu trnh sinh sn v tng hp riboflavin. Hm

lng magie c trong t bo nm men l 0.3 0.4%.

Km tuy c rt t trong mi trng nhng ng vai tr cc k quan trng.

Nhc km, cc qu trnh oxy ha xy ra hon ton v kh nng ng ha glucose

tng.

1.1.6.5 Cc cht kch thch sinh trng.

Thng l cc vitamin v cc axit amin. Cc loi vi sinh vt khc nhau c

nhu cu v vitamin khc nhau. a s cc chng nm men ang giai on nhn

ging cn n isositol, canxi pantothenat, thiamyl v c bit l biotin.

T bo s dng cc cht ny to t bo cht. Nng ca vitamin c th

nh hng dn qu trnh sinh trng v pht trin l 0.01 1.10mg/l. Cc vitamin

quan trng nh B1, B3, B6, B7.


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1.1.7 Shp ph cht dinh dng ca t bo nm men.

Hin nay ngi ta nhn thy qu trnh dinh dng ca nm men gm 2 giai

on:

Cht dinh dng qua mng t bo cht vo t bo.Chui cc phn ng ha hc, bin i cht dinh dng tng hp cht

liu cho t bo. Mi trng dinh dng cha nhng thnh phn c p sut thm

thu khc nhau.

Cc cht khng in tch nhng saccharose, ru axit hu c, amino

axit xm nhp qua mng t bo bng cch khuch tn hay vn chuyn thng, do

s khc nhau v nng cc cht ny gia t bo v mi trng. Cc cht in tch

trong dung dch nh mui KCl, magie, canxi v cc kim loi khc c th vo t bo

thng theo thang nng hay vn ng ngc li thang nng (vn chuyn

hot ng).

Ngoi ngun hydratcacbon v ngun nit hoc v c hoc hu c, nm

men cn s dng cc nguyn t vi lng nh K, Na, Ca, Mg c vai tr quan trng

trong dinh dng nm men. Ring natri c ngha quan trng trong s tng trng

ca t bo nm men. Ion natri l thnh phn duy nht di chuyn vo t bo bng c

2 cch: thng v hot ng v khi n thm nhp vo t bo nm men, mang

theo c saccharose, amino axit, ngay c khi khng c s chnh lch nng cc

cht ny gia t bo v mi trng. Kt qu thi nghim cho thy: khi thm NaCl

vo mi trng t 1-1,5%, dn n qua trnh tng hp hot ng tng, gia tng hot

tnh sinh sn ca nm men v hiu sut thnh phm cao hn, phm cht thnh phm

c ci tin, ng thi hn ch s pht trin ca nm men l.

Bng 1.2: nh hng trn thnh phm men bnh m.

Thnh phn trong t

bo

Cht lng nm menPhng php nui

Cht

kh

m Hot lc

lm c bt

Tnh nhy cm

thm thu

(pht)


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Khng thm NaCl 34,7 65,3 60 - 75 5 20

C thm NaCl 40,0 60,0 45 55 0 6

Cht dinh dng sau khi vo t bo nm men sc bin i theo mt

trong hai con ng sau, tuy iu kin mi trng v phng php nui cy:

C6H12O6 2CH3 CO COOH + 2 H2

CH3CH2OH + 3CO2 [1] 6CO2 + 6 H2O [2]

Trong , con ng ch yu l to cn. Theo quan im nng lng, qua

trnh ny t kinh t hn v cn nhiu nng lng trong ru, trong khi cn ng to

ra cc thnh phn ch yu ca t bo. T nhng thnh phn ny khi lng t bao

gia tng n mt gii hn nht nh, sau t bo bt u ny chi. Vch t bo

mm i, cht nguyn sinh ca t bo chui qua vch ny, v bt u hnh thnh vch

cho ti sinh cht con. Chi tng dn kch thc cho n khi tch khi t bo m.

Ty chng v iu kin nui, qu trnh ny thng mt t 1-1,5 gi. Cho n nay

cha r l c bao nhiu t bo con c thc sinh ra t t bo m. Theo d kin

ca A.Kyker mi t bo nm men c kh nng to c trung bnh 25-40 t bo

mi.

1.2 Vai tr ca sinh khi nm men [1]

Trong cng ngh sn xut bnh m, giai on ln men bt m ng vai tr

quyt nh n cht lng bnh m. Qu trnh ln men c thc hin bi nm men.

Khi nm men chuyn ha ng c trong bt m thnh cn v CO2 theo phng

trnh phn ng sau:C6H12O6 Nm men 2 C2H5OH + 2 CO2

Chnh CO2 l tc nhn lm bnh m n. Khi CO2c to thnh s b gi

li trong mng gluten. Gluten trong bt m l loi protein rt c bit, chng c tnh

cht n hi v to mng. Cc protein khc khng c c tnh ny. Khi nng bnh

m nhit cao, CO2 s tng th tch, mng gluten s cng ra v to thnh nhng

ti cha CO2. Khi nhit cao hn, CO2 s thot ra khi ti cha v to ra

nhng l xp trong bnh, kt qu l bnh c xp. Kh nng ln men cng mnh


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th xp ca bnh cng nhiu v bnh cng n, th tch bnh cng tng. Tuy

nhin, khng phi th tch bnh ln quyt nh n cht lng bnh m. Mc

tng th tch ca bnh m ch ni ln kh nng ln men bt m ca nm men. Cc

nc sn xut bnh m c yu cu mc tng th tch khc nhau. iu ny ph thucvo thi quen khi s dng bnh m.

Trong sn xut bnh m hin nay cc nc chu u, ngi ta s dng 3

dng nm men lm nbnh:

Dng nm men lng. Dng nm men nho (paste). Dng nm men kh.

1.2.1 Nm men dng lng.

Nm men dng lng c u im l d s dng v c hot lc lm nbnh

rt cao.

Tuy nhin, nm men lng c nhc im rt ln l kh bo qun, thi gian

s dng ch nm trong gii hn 24 gisau khi sn xut. Chnh v th, vic sn xut

v s dng nm men lng thng c t chc nh mt phn xng ring trong

nhng cssn xut bnh m mang tnh cht t cung t cp.

Nm men lng l mt sn phm thu nhn c ngay sau khi qu trnh ln

men hiu kh kt thc. Ngi ta thu nhn dch ln men c cha sinh khi nm men

dng ang pht trin sn xut bnh m. Lng nm men s dng thng ln t 1

10 % so vi khi lng bt m em s dng. Ngoi ra, khi s dng nm men lng

th vn cht lng rt c quan tm do n rt d b nhim nhng vi sinh vt l,

b ln cc sn phm trao i cht ca nm men.

Hin nay nhiu c s sn xut bnh m cc nc chu u v chu Mkhng s dng nm men lng m s dng ch yu nm men dng paste v dng

kh.

1.2.2. Nm men dng paste:

Nm men paste l khi nm men thu c sau khi ly tm nm men lng.

Nm men paste thng c m khong 70 -75 %. Nm men paste thng c hot

lc nbnh km hn nm men lng do trong qu trnh ly tm v thi gian ko di,nhiu t bo nm men cht. Nu c bo qun lnh 4 70C, ta c th s dng


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nm men paste trong khong 10 ngy. Nh vy nu chuyn nm men long sang

nm men paste, ta c th ko di thi gian s dng v thun li trong vic vn

chuyn. nhiu nc, nhiu cssn xut bnh m s dng nm men dng paste.

Vit Nam, cc cssn xut bnh m cng thng s dng nm men paste. Liulng s dng khong 5 % so vi khi bt ln men, iu ny cng cn ty vo

cht lng nm men paste.

1.2.3. Nm men kh:

Nm men kh li c sn xut t nm men paste. Ngi ta sy nm men

paste nhit < 400C hoc s dng phng php sy thng hoa. Nm men kh c

m < 10%, hot lc nkhng cao nhng li c u im rt ln l thi gian s

dng rt lu v d vn chuyn.

1.3 Cc yu cu ( ch tiu cht lng ) ca sinh khi nm men bnh m.[1]

Nm men Sacchromyces cerevisiae dng cho sn xut nm men bnh m

m bo nhng yu cu sau:

- T bo nm men c kch thc ln, u, c kh nng pht trin mnh v

chu c nhit cao.

-C hot lc enzyme zymase < 45 pht (gi tr ny c xc nh khi cho

nm men (2,5% ) ln men 20 ml dung dch ng 5% gii phng ra c 10ml

CO2).

- Hot lc maltase < 70 pht (gi tr ny biu th thi gian cn thit gii

phng 10 ml CO2 khi ln men 20ml dung dch mantose 5% vi hm lng nm men

2,5%). Ch s ny dng nh gi kh nng ln men ng mantose ca nm

men.

- Lc nbt < 45 pht (gi tr ny biu th thi gian cn thit lm n280 gam bt vi 160 ml dung dch NaCl 2,5% v lng nm men la 5 g) trong

khun hnh bnh hnh c kch thc xc nh.

- bn ca nm men > 72 gi(xc nh s thay i thi gian lm nbt

ca nm men lc ban u v sau mt thi gian bo qun nht nh. Nu bn ca

nm men cao th sau 72 gibo qun nhit 0 - 4C, thi gian lm nbnh

khng c tng qu 5 pht).


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Chng 2

CNG NGH SN XUT SINH KHI NM MEN BNH M

2.1. Nguyn liu trong sn xut nm men bnh m

2.1.1. Nc

Nc c coi l nguyn liu chnh trong sn xut v y l cng ngh ln

men chm hiu kh. Nc s dng trong sn xut nm men bnh m l nc s

dng trong sinh hot hng ngy. Trong trng hp s dng nc ging hoc nc

b mt khc, phi x l t cht lng nc dng trong sinh hot. Yu cu ca

nc:

C cng t 4 - 8 (1 cng 10mg CaO/lt).Khng mu, khng mi, khng v.

Cc cht sau khng c qu mc cho php (mg/l): Cl- < 0.5; SO42- 72 gi.

Hot tnh zymase 45 pht.

Hot tnh maltase 70 pht.

Tnh nhy cm thm thu 10 pht.

Cng c thnh gi sb bng c im hnh thi v vi c im ca

mt s cquan ca t bo khi nhum v quan st di knh hin vi.

T bo ng nht khng ln.

Khng c th m.

Nhum t bo vi xanh metylen: nu t bo gi, cht s bt u t mu

xanh n xanh m, trong khi t bo tr khng bt mu.

Vng tun hon sau 200L c th ln n 10 ln ph thuc vo cht lng

men m, sch ca mi trng, nguyn liu, iu kin v sinh ca csmi vng

t 6 n 8 gi. cc nc pht trin giai an nui men m v men thng phm

c thc hin trong thit b ln men kn, kh ti u viu kin thng kh, iu

kin kim tra qu trnh c tng ho ,do kp thi x l nhng sst v k

thut.

Thit bnui men

Phuy nha 200L: 25 30 ci, y l thng nui men bnh m ph bin

thnh ph ta, thch hp vi iu kin sn xut bn th cng, d lm v sinh, sau mi

t nui. Tuy nhin, cng cn c mt s im hn ch nh h thng kh b trkhng ng u, chiu cao ct nc khng t, lng kh chi ph kh cao.

Nu c iu kin u t xy dng, nn thit k hai ni nui men qui m

0,5m v 2m. Dng thp khng r lm y v phm v bc xung quanh, np y

bng kim loi, c h thng phn b kh, hi nc, h kim tra nhit , pH,

lng kh,


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2.3.3. Nui cy nm men thng phm [1]

Gm cc phng php sau:

a.Nui nm men thng phm theo chu kTrong giai on nui cy cn phi lu my vn quan trng sau: Thnh phn mi trng: mi trng nui cy nm men thng phm

thng khng khc nhiu so vi mi trng nui cy trong qu trnh nhn ging.

Tuy nhin, thnh phn mi trng phi tuyt i n nh cht lng nm men

ng u tt c cc m nui trong sut qu trnh sn xut v mi trng nui cy

phi v trng.

Lng ng trong mi trng khong 2 3%, khng nn nhiu hn v

cng khng nn t hn. Nu lng ng cao s va lng ph v va to ra nhng

sn phm trao i cht khc, gy c ch ngc n qu trnh to sinh khi.

pH mi trng khang 4.2 5.4. Khng nn h thp pH ca mi trng

xung v lm nh vy nm men s kh pht trin. Nu pH cao qu va c ch nm

men pht trin, va to iu kin cho vi khun nhim vo dung dch nui v pht

trin, cnh tranh cht dinh dng, lm gim cht lng nm men.

Thit b nui nm men va c dung tch thch hp, va thun li cho vic

np mi trng, ph bt cng nh thu nhn sn phm. Thit b phi c lp t

hp l h thng thi kh, h thng cnh khuy v tm cn dng chuyn ng ca

mi trng lm tng qu trnh trao i cht ca vi sinh vt.

Vic cung cp oxy cho qu trnh to sinh khi rt cn thit. Oxy l mt

trong nhng yu t quan trng nh hng n sinh trng v pht trin ca nm

men Saccharomyces cerevisiae. Vi sinh vt nht l nm men khng th s dng oxy

dng ha tan trong mi trng lng.Lng oxy ha tan trong nc rt t. Trong qu trnh pht trin, nm men

s nhn oxy ha tan v nh vy lng oxy ha tan s gim, do cn phi cung cp

oxy t bn ngoi thit b.

Nm men Saccharomyces cerevisiae l loi vi sinh vt hiu kh ty tin.

Nu ch thiu oxy trong mt thi gian ngn, ngay lp tc chng chuyn qu trnh

ln men hiu kh sang qu trnh ln men ym kh. Nh vy lng sinh khi s to

thnh rt t v ng s chuyn ha theo cc chu trnh ng phn ca cc chu trnh


21/38



khc cui cng to ra nhng sn phm trao i cht bc hai. Do , qu trnh

nui cy nm men thu nhn sinh khi bt buc phi c cung cp oxy lin tc.

V nm men ch c th s dng oxy dng ha tan nn khi tc ha tan

ca oxy vo dung dch bng tc s dng oxy ca t bo nm men th sinh khi tbo nm men st cc i.

Tc ha tan ca oxy vo mi trng lng c tnh theo cng thc:

)( 1CCKdt

dcR La ==

Trong :

R: tc ha tan ca oxy

C: nng oxy bo haC1: nng oxy ha tan thi im kho st

KLa: hng s t l

t: thi gian.

Trong thit b ln men ngi ta phi lp t h thng phn phi kh v h

thng cnh khuy. H thng phn phi kh trong nui cy nm men thng c

lp t di y thit b.

Khi s vng quay ca cnh khuy v tc thi kh tng th ha tan ca

oxy vo dung dch mi trng s tng theo. ng thi lm tng s xo trn mi

trng, thc y qu trnh trao i cht v sinh sn tng nhanh.

Tuy nhin, vic tng tc khuy v tc thi kh chn mt gii hnh

nht nh. Nu tc ca hai yu t ny qu cao, s lm tng hin tng t phn

ca t bo v bt s to ra nhiu.

Vic cung cp oxy cho nhng thit b nh trong cc phng th nghimthng rt kh khn. Do , ngi ta thng s dng my lc lm tng s ha

tan ca oxy vo mi trng.

ha tan ca oxy b chi phi bi nhit ca mi trng. Khi nhit

ca mi trng tng th ha tan ca oxy s gim. Nhit thp thng lm tng

tc ha tan ca oxy.

Nu trong qu trnh ln men, nhit mi trng tng nhanh (do qu trnh

h hp ca vi sinh vt) th ngay lp tc phi thi kh mnh lm gim nhit ca


22/38



mi trng. Nu khng lm h nhit , ha tan ca oxy s gim v nng sut

sinh khi s gim.

Trong trng hp phi dng nhng cht hot ng b mt, cht ph bt,

hoc mt s cht chng nhim trng, ha tan ca oxy cng gim.Hin nay, c nhiu phng php xc nh oxy ha tan. Nhng phng

php ph bin nht nh sau:

Phng php ha hc

Phng php cc ph

Phng php o in th oxy ha kh

Phng php o trn my Vacbua

Khi xc nh lng oxy ha tan trong mi trng, ngi ta biu hin gi tr

ny theo cc n v sau:

Phn trm so vi kh nng bo ha p sut ring phn Milimol hoc miligamNghin cu nh hng ca oxy ha tan n s pht trin ca nm men

Saccharomyces cerevisiae cho thy: nng sut to thnh sinh khi tng dn khi tng

hm lng oxy ha tan. Nng sut sinh khi nm men t cao nht khi lng oxy

ha tan tng t 0.5 1 milimol/l/pht. Khi lng oxy ha tan tng ti 4

milimol/l/pht, sinh khi gim. Nu tng lng oxy ln na, sinh khi s gim

nhanh. iu cho thy s tng oxy ha tan khng phi t l thun vi s tng sinh

khi.

Khng kh trc khi a vo thit b ln men, phi c lm sch khi vi

sinh v cc tp cht.Nhu cu cung cp oxy cho qu trnh pht trin ca nm men khng phi lc

no cng ging nhau. Do , ta phi thay i mc cung cp oxy theo ng nhu

cu thc t ca nm men.

giai on tim pht, nm men cn c thi gian thch nghi vi iu kin

mi. giai on ny, vic to thnh acid amin, cc pectin v acid nucleic xy ra

nhanh hn cc qu trnh khc. Thi gian ny c th di, c th ngn ty thuc vo


23/38



tng loi nm men. Giai on ny thng khong 0.5 1 gi. Giai on ny ch cn

cung cp lng khng kh khong 50m3/gi/m3 mi trng l .

giai on tng trng, nm men tin hnh qu trnh trao i cht rt

mnh, khi lng nm men trong cc thit b tng r rt. Vic tng hp enzymec xc tin nhanh. Hm lng RNA c tng hp nhiu nht. Giai on ny

thng ko di khong 7 14 gi v cng l giai an nm men cn nhiu oxy

nht, do lng oxy cung cp phi gp i giai on u tin, khong 80

100m3/gi/m3 mi trng.

Giai on k tip l giai on cn bng. Giai on ny c nhiu thay i

quan trng. Lng t bo mi sinh gn bng lng t bo cht. Cc qu trnh trao

i cht gim mnh, do nhu cu oxy khng nhiu. Giai on ny ko di khong

1 2 giv ta phi gim lng khng kh cp vo mi trng. Lng khng kh

cp vo giai on ny t 20 50m3/gi/m3 mi trng.

Trong sn xut nm men bnh m, ngi ta thng kt thc qu trnh nui

nm men giai on 2, bi v, mt trong nhng yu cu quan trng ca nm men

bnh m l s lng t bo nm men sng phi chim i a s nn khng thi

n giai on cn bng mi tin hnh thu nhn sinh khi, lm nh vy nm men thu

c s cha nhiu t bo gi.

Trong nui cy nm men bnh m, ngi ta thng nui trong khong thi

gian 8 16 gi. Ti a l 16 gi.

b. Nui cy nm men bnh m theo chu k c b sung dch nui cyNui cy theo chu k c nhc im:

Tn tht thi gian cho giai on v sinh thit b v iu kin sn xut.

Sinh khi nm men thu nhn c bao gm c t bo mi sinh trng, tbo trng thnh v t bo gi.

B tc ng mnh bi cht dinh dng vi hm lng kh cao ngay t

thi gian mi nui cy.

khc phc nhc im th hai v th ba, ngi ta ci tin phng php

bng cch a cht dinh dng vo thnh nhiu t. Phng php ny gip t bo

nm men khng chu p sut thm thu cao. Cch b sung mt r x l c tm

tt trong bng sau:


24/38



Bng 2.4: Bsung mt rv cc cht dinh dng trong nui cy theo chu k

Ginui

cy

Rng

(%)

(NH4)2SO4

(%)

(NH4)2HPO4

(%)

H2O (%) Th tch

dch (m3)

0 5 10 10 50 1 4 - - - 27

1 2 4 15 15 2 27.5

2 3 5 15 15 6 30

3 4 6 15 15 6 37

4 5 7 15 15 7 51

5 6 8 15 15 8 59.5

6 7 10 15 15 9.5 70

7 8 12 - - - 70

8 9 13 - - - 70

9 10 14 - - - 70

10 11 12 - - - 70

11 12 n nh - - - 70

Tng s 2700 kg 130 kg 40 kg 43.5 kg 70m3

Ghi ch:

T l phn trm so vi tng s cht dinh dng cn cho vo.

Thit b trn dng cho thit b nui cy l 100m3, dung tch dch nui l

70m3.

c.Nui cy nm men thng phm theo phng php lin tc khc phc nhc im ca phng php nui cy theo chu k, ngi ta

thc hin phng php nui cy lin tc. u im ln nht ca phng php ny l

nng sut tng v t bo nm men lun lun c i mi cht dinh dng.

Phng php nui cy lin tc cn cho php ta kim sot v iu khin d

dng qu trnh. iu lu l vic cung cp oxy l phi lin tc v c cng mt mc

. y l im khc bit gia phng php lin tc v phng php theo chu k.

Mc cung cp khng kh trong phng php ny l 80 100m

3

/gi/m

3

mitrng sut qu trnh nui cy.


25/38



Thit bsdng: My nn kh (my thi) [2]

L mt trong nhng thit b quan trng nht trong b phn sn xut men.

Cn chn my c kh nng t hot ng c c v s lng kh vn dng v nng

lng tiu th, c th duy tr mt p sut n nh trong th tch ln. Khi cn gimth tch kh, nng lng tiu th ca my gim, ng thi p sut cng khng vt

qu mc ti a xc nh trc m bo an ton. Yu t ny cn thit v th

tch kh thay i ty giai on pht trin ca nm men v mi trng nui men.

2.3.4. Ly tm tch ra men bnh m:

Dch b l mt h thng cc cu t phc tp, gm c nc ( 82-90% theo

khi lng), cht kh (4-10%) v ru etylic v cc cht bay hi (5-8%) theo khi

lng (W) hoc 6-10% theo th tch (V). Dch ny lun lun c mt lng CO2 ha

tan nht nh (1-1.5% g/l), chua khong 0.5, pH 4.9-5.2. Dch men sau kt thc

qu trnh ln men ru c kh nhiu t bo nm men l lng trong dch v mt

phn b lng thnh cn xc men.[1]

Cht kh trong t dch men gm c t bo nm men, cn b ca mi trng

rng cng vi nhng cht ha tan trong hn hn hp ru-nc (ng khng

ln men, protein, cht khong)[1]

tch c sinh khi nm men gic hot tnh lm nkhi bt

nho khi khi dnh ngi ta thc hin bng cch ly tm tch ( seperator) 5 cp, 7

cp, ly tm tch hon ton, ra sch men lm trng mu, ri a qua sy kh

khng lm cho men cht.[1]

Qua cc cp thu c xc nm men cn phi ra sch v nng ln men

c dn c sng mu dn, sn phm thu c l men m c. tch men t

dng m c ta qua thit b lc p, men nm li gia cc bn lc.[1]Dng bm bm dch men vo my ly tm loi mi trng cn li.

Thi gian ly tm cng nhanh cng tt (khng qu 2gi). Ra khng lm

xu cht lng men nhng nc ra phi 2oC, nu ra nc nhit thng

lm tng thi gian ly tm, c thnh hng ln cht lng thnh phm. Trong khi

nui, nu c s c v k thut nh nhit tng khng cht khong th sau khi

ly tm ha t bo vo nc lnh 2oC kt hp vi x l sau:

Chlotetracylin-hydroclodrid 5g/m3 trong hn 30 pht.


26/38



Axit sorbic 1kg/m3 trong 30 pht.

KH2PO4 (8,5-20kg/m3 ) t 1-15 pht.

Nhng cht ny 1 phn hn ch s pht trin ca vi sinh vt gy nhim,

ng thi c tc dng dng trn hot tnh sinh sn ca men.Men p c m 71%-74% v a vo nh hnh, ng gi. Nu men qu

kh cn thm 10% nc theo khi lng ri mi nh hnh. Khi nh hnh nn thm

0,1% du thc vt v thc hin nhit 10-15oC (nhit cao hn c th thu

nhn c sn phm khng tt).

Men p c ct thnh bnh vi khi lng khc nhau (50, 100, 500, 1000)

v c gi vo trong giy thic hoc bng giy plastic ngoi v bao bng giy

thng. Men thnh phm dng ny l men bnh m dng bnh (hay dng t), bo

qun 0-4oC v m khng kh gi82-96%. Thi gian bo qun trn 12 ngy

trong iu kin ny.

Men p c m khong 75% trong nhit bnh thng tng i b mt

hot tnh. V vy khng nn vn chuyn khong cch xa, cng nh ginhit

thng trong thi gian di. V khc phc c nhc im ny ngi ta thng

cho qua sy.

Khi sn xut men bnh m cn ch n qu trnh ny v qu trnh ny c

nh hng ln n cht lng thnh phm. Trong qu trnh lng, khng cn cht

dinh dng trong mi trng, h enzyme trong t bo nm men chuyn t qu trnh

hot ng sinh tng hp sang qu trnh trao i ch nhm duy tr nhng chc nng

bnh thng ca t bo. Trong giai on ny, c dng t bo con, t bo tr va mi

to chi, t bo thnh thc. T s cc dng ny khc nhau ty thuc quy trnh k

thut v mi trng hot ng lc u. S t bo thnh thc cng cao men thnhphm cng gic tnh cht ca n lu hn. iu kin lng tt nht l:

Gim nhit n 27o C.

Gim lng khng kh 40-60% so vi giai on nui chnh.

Thi gian lng t 1,5-2 gi.

2.3.5. Lc p qut kh:

Ly tm xong, thu ly nm men cho vo my lc p trc khi ng gi.

Nm men c gi li trong lp vi lc v dch mi trng s thm ra ngoi. Tc


27/38



v lc ph thuc vo lc tc dng v si khng ca mi trng. Nu giai

on lc p tt, sau giai on ny s nhn c dng men p cha khong 75%

m c thng gi, khng qua giai an qut kh.

Trng hp lc p khng t hiu qu, c th dng qut gi x l tip tna gin 1gi.

2.3.6. Sn xut men p:

2.3.6.1 To hnh, ng gi men p:

cc nc, giai on ny c thc hin bng my, v c b sung du

thc vt (0,1%), lecithin m bo bn chc v mu sc sn phm. Cc cs

sn xut men bnh m nc ta do trnh cng nghip cha cao v c nhiu lao

ng th cng nn sau khi lc p men c nho trn cho u, ngi ta c th

nhi bng tay nh nhi bt lm bnh bao hay cho t 5-10kg men vo bao vi dy,

ct cht ming bao li v p bng chn cho n khi ng nht v mu sc v

chc. Cn men thnh tng phn nng 0,5kg cho vo ti nilon loi dy, p trong

khun cy c kch thc tng ng. p cht men theo khi vung vc ca khun,

vut bao li cho thng, bc kn v ct thun li. Ct vo t lnh bo qun t 2-400C.

Khu to hnh v ng gi men cng lm nhanh cng tt, v trong iu kin

sn xut ca ta, nu khng ra sch men, h enzyme ca t bo nm men ang

trng thi ngh, c th tip tc hot ng nh hng ln cht lng men, hoc c vi

khun gy nhim sinh sn mnh hn t bo nm men ang ngh. Hot ng ca vi

khun s to ra trong mi trng nhng cht c lm km hm t bo nm men, lm

cho s lng nm men sng trong thnh phm gim.(3)

2.3.6.2 Bo qun lnh men p:

Sau khi ng gi, nm men c chuyn n phng lnh 0 40

C, mkhng kh phi duy tr 82 96%w

2.3.7. Sn xut men kh [1]

2.3.7.1 Sy

Sau khi thu c dng men p bng phng php nui men c bit lm

men kh, qu trnh lm men kh tip theo gm hai giai on chnh:

Trc nm men p thnh dng si di c dy v chc ng nht.


28/38



Kh nc, lm kh si nm men trn li thp nhqut thng kh kt

hp vi nhit t 31 32C.

Trc nm men thnh dng si

thc hin giai on ny c th thit k da ng, c c l kch thc0,3 cm, gn u ra ca my nghin hay my gi.

C th lm m nm men nu cn bng cch nho trn n khi c ng

nht mong mun. Cho nm men vo phu, tu ra s nhn c nm men dng

chui di khng t, cng khng dnh nhp li vi nhau. Lp tc tri si nm men

ln mng lm kh, nhng nu nm men qu kh, chui nm men s vkhi ra khi

my, bt nm men ri xung mng lm kh. Nu nm men qu m, khi ra khi my

si nm men s dnh vo nhau, khng to thnh si c.

Khnc

Tri si nm men ln khay sy, cho vo my kh nc, dng lung kh do

qut cung cp, cng sut 2700m/pht, to ra s thng gi c tc 1,2m/giy.

Nhit ca my c iu ha nhh thng hi nc duy tr 31C trong 1 gi

u v 32C trong 3 gisau.

Hin nay ngi ta dng my sy thng hoa sn xut nm men kh. Ti

mt s cssn xut, ngi ta trn nm men vi dung dch mui NaCl lm tng

nhanh qu trnh thot m v tng kh nng chu nhit ca nm men.

Sy thng hoa l phng php sy bng cch h thp nhit sn phm sy

xung di im ng lnh (di -10oC) v c t trong bnh chn khng c p

sut gn vi p sut chn khng tuyt i, khi nc thot ra khi sn phm sy

trng thi rn, tc l thng hoa m. Sy thng hoa hay cn gi l ng kh l

phng php lm kh sn phm da theo hin tng vt l l thng hoa (chuynnc t pha rn sang pha kh). M hnh h thng thit b sy thng hoa gm 5 b

phn: bnh thng hoa, bnh ngng ca my lnh, my nn ca my lnh, bnh

ngng-ng bng, bm chn khng.

Qu trnh sy thng hoa gm 3 giai on: giai on ng lnh, giai on

thng hoa v giai on sy m d. Sy thng hoa c u im gim thi gian sy

xung 3 ln, khng nh hng ln n gi tr dinh dng v mi v sn phm, tuy

nhin chi ph nng lng ring cao hn cc phng php khc khong 50-60%.


29/38



Bng 2.5: Chscht lng men kh v cch bo qun tngng [1]

Ch s

Hot tnh

lm dy bt(pht)

m(%)

Trehalose

cht kh(%)

Axit tng

s(ml)

Thi gian

bo qun

(thng)

Hnh thc

bo qun

>12

5

Gi kn

Gi khng

kn

61-70

61-70

61-90

8,1-10

8

10

14,1-16

11,1-14

11

1,1-1,3

1,4-1,7

>1,7 Khng bo qun c

trong giy gi.

Sn phm men kh c thi hn s dng di hn men p, thng trn 1 nm

nu c ht chn khng v c tr trong iu kin thng.

u im: thi gian s dng rt lu, d vn chuyn.

Nhc im: hot lc lm nkhng cao.

Do thi gian bo qun nm men lng ngn nn ngy nay ngi ta dngnm men nho v nm men th l bnh m.

2.3.8. Gii thiu tnh hnh sn xut men kh nc ngoi

Sn xut men kh l qu trnh k thut kh phc tp; cn chng nm men

c bit, cc ch nui men m v men thng phm c khc so vi men p. Hin

nay cc nc pht trin, vn ci tin cht lng men kh vn cha c hon

chnh, cc nghin cu thng tp trung theo 3 phng hng sau y:

Chn lc chng nm men c bit t dng men p bn vng cho nkh, sau dng phng php thch hp nui, v pht hin nhanh thng s thch

hp vi qu trnh lm kh ca nhng chng ny.

T dng men kh bn vng qua thi gian bo qun, kho st v pht hincu trc hay ch s no ca chng thch hp vi vic bo qun.

Tip tc ci thin cch bao gi men kh. nui nm men lm men kh, quy trnh c thay i so vi phng php

nui men p:


30/38



Dng mi trng c nng cht kh cao (pha long rng t 7-14ln, thm mui NaCl vo mi trng nui men) hay ngng cung cp ngun thc n

cacbon vo cui qu trnh sinh sn.

Gim cng thng kh Tng nhit nui men ln t 30-33C.Sau khi c c dng men p qua ch nui c bit nh trn, nm men

p chu x l nhit nh sau:

Quc gia Phng php lm kh Thi gian

Anh 120C

41C

8 giy

45 giy

Php 50 - 70C 10 15 pht

Lin X 30 - 60C 3 6 gi

H Lan sn xut c loi men kh c bit gi l Ferminan, l hn

hp men kh v men p bnh m vi t l 1:3. Men Ferminan c hot tnh men cao

hn men kh 2 ln v cao hn men p t 4-6 ln.

2.3.9. c im men chu c qu trnh lm kh

2.3.9.1 Lng Trehalose trong t bo cao:

Trehalose l ngun cht d tr cho t bo. Nhng nghin cu v vai tr ca

hydratcacbon cho thy: Trehalose khng nhng l ccht giu nng lng cho cc

qu trnh ni bo, m cn l tc nhn iu chnh p sut ni bo, qua lm tng

hot tnh sinh tng hp. Phn tch ha hc cho thy lng Trehalose trong men p

c t 2,1 4,9%, trong khi lng Trehalose trong men kh c t 7,6 8,1%. c

nm men cha nhiu Trehalose c th dng mt s phng php sau:

Tng p sut thm thu ca mi trng

Gim cng thng kh

Khng cung cp ngun hydratcacbon 2-3 givo giai on cui ca qu

trnh sn xut.


31/38



Bng 2.6: nh hng ca ngun dinh dng hydrat cacbon trn cht

lng nm men [2]

Men p Men khCh cung

cp hydratcacbon

pha

long rng

Hiu

sut(%)

Hot lclm dy

bt

(pht)

LngTrehalose

(%)

Hot lclm dy

bt

(pht)

LngTrehalose

(%)

Khng bi

Bi 1 gi

Khng bi

Bi 1 gi

17

17

8

8

69,0

74,0

70,1

77,2

75

62

55

50

5,1

8,0

9,1

11,3

78

71

57

47

9,3

13,9

12,6

15,5

2.3.9.2 Lng saccharose ni bo:

Cng l mt ch s quan trng xc nh men thch hp lm men kh.

Ch s ny c xc nh bng cch o kh CO2 to ra khi cho lng nm men p

ln men 20ml nc my 30C. Trong qu trnh h hp hiu kh, ng ni bo

c bin i thnh kh CO2 v H2O. Do c th tnh c lng saccharose nibo nh s lng kh CO2 phng thch ra. Th tch kh CO2 tng ng vi lng

saccharose ni bo thch hp cho men lm kh l 20 ml CO2/gi.

2.3.9.3 Tnh nhy cm thm thu:

Th hin bng s chnh lch v thi gian lm dy bt ca nm men gia

bt khng c NaCl, v bt c 3,35% NaCl. S khc nhau khng qu 10 pht, c

chn l nm men bn vng lm kh.

2.3.9.4 Kh nng to bo t:

Nhng chng thch hp lm men kh c kh nng to bo t thp hn

40%.

2.3.10. Yu cu cht lng men kh

V cm quan, nm men kh c dng ht nh hay si ngn, mu vng sng

c mi thm c trng ca nm men.


32/38



Bng 2.7: Chtiu cht lng men kh [2]

Ch tiu ha l Men cao cp Men loi 1

m 8% 10%

Hot lc lm dy btThi gian bo qun

70 pht12 thng

90 pht5 thng


33/38



Chng 3

CC YU TNH HNG N SINH KHI NM MEN V PHNG

PHP BO QUN NM MEN

3.1. nh hng ca iu kin mi trng bn ngoi tc tng hp sinhkhi nm men.

3.1.1. Nhit .

C nh hng ln ln tc tng trng ca nm men. Nhit thch hp

nht nm men pht trin tt l 28-30C. Trn 43C v di 28C s sinh sn ca

nm men b chm hay ngng li.

3.1.2. pH ca mi trng.

pH tt nht cho s tng trng ca men bnh m l 4,5 5,5; pH= 4:

tc tch ly sinh khi gim. Nu pH=3,5 hay pH=3 s lm s sinh sn ca nm

men b ngng li. Mc hp th cht dinh dng vo t bo, hot ng ca h

thng enzym tham gia vo s tng hp protein, to vitamin u ty thuc vo

pH, pH ngoi 4,5-5,5, lm cht lng nm men gim i.

3.1.3. nh hng ca cht ha hc.

Nguyn liu ch yu sn xut men bnh m l r ng, amonium

sunphat, DAP, MgSO4, axit sunfuric trong cc ha cht ny i khi c s hin din

ca nhng cht lm c ch s tng trng ca t bo nm men.

Bng 4: nh hng ca mt s cht ha hc ln s tng trng ca t bo

nm men.

Cht Nng lm nm men

chm hay ngng pht

trin (%)

Nng cht lm nm

men cht (%)

Sunphuro

Natriflo

Axit nitric

Formalin

Karamen

Axit acetic

Axit formic

0,0025

0,002

0,0005

0,001

0,1

0,02

0,17

0,004

0,9

3


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Axit oxalic

Axit sunfuric

Axit photphoric

Axit clohidricEthanol

0,001

0,39

0,30

0,1412

0,34

1,3

2

0,7225

3.1.4. nh hng nng rng

Tc tng trng ca t bo nm men ph thuc vo s hp th cht dinh

dng, trong gii hn p sut thm thu ca mi trng v nng t bo. p sut

thm thu ca mi trng tng khi hm lng cht kh nh saccharose hay cht

hot ng thm thu nh NaCl nhiu. Hin nay, cc nh my sn xut men bnh m

nc ngoi nui nm men trong mi trng c nng saccharose ln n 5-6%

ci tin cht lng men p v lm men kh.

3.1.5. nh hng ca cng khng kh v khuy trn ln tc

tng trng ca nm men

Trong qu trnh nui nm men cn thit gi cho dch men lin tc bo ha

oxy ha tan. Ngng cung cp oxy trong 15 giy s gy nn tc dng mtrn hot

ng sng ca nm men. Oxy kh quyn chuyn vo t bo nm men qua hai giai

on :

- Ha tan oxy n dng lng.

- Hp thu oxy ha tan vo t bo.

V l thuyt cn 0,761m oxy oxy ha 1 kg ng, nhng thc t ch

mt phn nh oxy bm vo c nm men s dng, phn cn li b mt i do cc

qu trnh tip xc, nhit nng , nhy nht ca mi trng, cng khuytrn. Kch thc ca thit b nui cy nm men l tin cn thit, nh hng gin

tip ln s tng trng ca nm men v chiu cao ct dung dch mi trng cng

cao, thi gian kh bm vo t n b mt lu hn, v s hp th oxy c thc y

khi nhit tng gn thch hp cho hot tnh men. Chiu cao ct dung dch men tt

nht l 3m mi c thm bo hiu sut thnh phm v gim trng lng khi tiu

dng. R rng l tng 1kg nm men cn ty thuc vo chiu cao ct nc v

lng kh tiu dng do cng c khc nhau.


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Chiu cao ct nc Lng kh cn/gi

3m

6m

8m

16m3

8m3

6m3

Trong iu kin thng kh tt nht, tng s th tch oxy bm vo dch men

gp 7 ln tr s l thuyt(6). Nu tc ha tan oxy cao, c th thy bt kh nh si

ln tn gia b mt tip xc ca cht kh v cht lng.

3.2. Cc phng php bo qun men ging.

3.2.1. Phng php 1:

Gi ging thun khit trn mi trng thch nghing, cy chuyn sau 12-

24 ngy sau khi hot ha sb trn mi trng lng.

Mi trng thch nghing, nc malt ng ha (c 12% ng kh)

49,5%; dch men t phn (khong 9% cht kh) 1% v thch 2%

Mi trng lng hot ha nm men ngi ta dng dch malt khng c

hublon, lng cht kh 12%.

Nu khng cy chuyn v hot ha kp thi th hot lc maltaza v kh

nng thch nghi vi rng gim hoc trn b mt thch cc t bo nm men sinh

bo t ri kt hp vi nhau lm thay i tnh cht ca ging.

3.2.2. Phng php 2:

Gi t bo men trong dch saccharose 30%. Dch ng c cho vo

bnh v thanh trng.

Cy ging tng thch nghi ng nui 2 ngy v gito bnh thng.

Trong iu kin ny nm men hu nh khng pht trin, khng ln men. Khi s dng c th dng que cy hoc pipet v trng ly dch ging cy

chuyn vo mi trng lng hot ha.

Sau 24-36h ginhit 3000C dch ng ln men v cy chuyn tip

sang mi trng thch hoc cc mi trng nhn ging.


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3.2.3. Phng php 3:

Bo qun ging di lp du vaselin hoc parafin. Ging cy trn mi

trng thch nghing 2-3 ngy c ph ln b mt mt lp vaselin v trng.

Ngi ta thng dng vaselin c t trng 0,8 - 0,9 c un nng 1500C ui nc c trong du, ri hp thanh trng. Lp du trn b mt mi

trng khng qu 1cm. ng ging c vaselin c thto trong phng nhng tt

hn c l gi4-600C.

3.2.4. Phng php 4:

Gi ging iu kin ng kh.

Dch huyn ph ging c ng trong ng nghim ampul trng thi

ng lnh (- 4000C), sy kh di iu kin lnh v chn khng cao ti m cn

1,5-2,6 % .

Gn ming ampul di chn khng v v trng.

Thi gian bo qun ti 3 nm khng phi cy chuyn, mt vi chng men

c bo qun ng kh c t l t bo sng thp.


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KT LUN

Qu trnh sn xut bnh men mi nc nhn chung l ging nhau, nhng

mi ni ty theo iu kin kh hu, c im nguyn liu, vn ha m c nhng

bin i ring c trng cho tng nc, tng sn phm. tng loi bnh men, h visinh vt ging nhau nhng li c t l gia cc loi khc nhau, dn n sn phm

ln men cui cng c v, mu sc, hng khc nhau.

Hin nay, xu hng th gii l tin hnh cng nghip ho cc sn phm

truyn thng. iu ny tt yu s din ra, v cc nc pht trin mong mun mang

hnh nh ca nc mnh ra th gii. Trong , thc phm truyn thng ng vai tr

quan trng. Ngi ta cn mt lng sn phm ln m ch c cng nghip mi p

ng c.

Nhng iu ny ch thnh cng mt s sn phm t i. Kh khn t ra

y l h vi sinh vt. Ch vi sn phm l con ngi c th ch r vi sinh vt hay h

vi sinh vt nh hng qu trnh ln men, t mi pht trin ln quy m cng

nghip. Cn cc sn phm cn li, cht lng sn phm cn ph thuc nhiu vo h

vi sinh vt to hng c trng. Do cha xc nh r h vi sinh vt trn nn con

ngi cha th kim sot c hon ton qu trnh c ln quy m cngnghip.

V vy vic quan tm, tm hiu, nghin cu v vi sinh vt s gip

chng ta hiu r v chng v hot ng ca chng. T chng ta s ngy

cng khai thc c nhiu ng dng ca chng trong cuc sng v hiu r

hn v nhng hot ng ca chng ang din ra trong t nhin xung quanh

chng ta.


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TI LIU THAM KHO

CHNG I:

(1) Nguyn c Lng, Cng ngh vi sinh, tp 2, Nh xut bn i Hc

Quc Gia Tp.HCM.(2) GS.TS.Nguyn Th Hin, Khoa hc Cng ngh Malt v bia, Nh xut

bn khoa hc v k thut

CHNG II:

[1] CNG NGH VI SINH Tp 2, NGUYN C LNG

[2] www2.hcmuaf.edu.vn/data/quoctuan/Nhom%204_1.pdf

[3] Lng c Phm. Cng ngh vi sinh. NXB Nng nghip.

CHNG III:

[1] www2.hcmuaf.edu.vn/data/quoctuan/Nhom%204_1.pdf.

[2] CNG NGH VI SINH Tp 2, NGUYN C LNG.

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Nam Men Banh Mi.hoan Chinh