san xuat kerfir

8/7/2019 San xuat kerfir

1/81

TRNG I HC AN GIANG

KHOA NNG NGHIP - TI NGUYN THIN NHIN

NG TH CM T

MSSV: DTP010842

NGHIN CU CH BIN SA KEFIR

LUN VN TT NGHIP K S NGNH CNG NGH THC PHM

GIO VIN HNG DN

ThS. Dng Th Phng Lin

KS. Trn Xun Hin

Thng 6 . 2005


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Anh 4 x 6

TIU S C NHN

H v tn : NG TH CM T

Ngy thng nm sinh : 08/11/1982

Ni sinh : Chu Thnh, Hu Giang

Con ng : NG ANH TUN

v B : NG TH THU BA

a ch : 040/10 QL 91A, Khu vc Bnh Phc, Phng Phc Thi, Qun

Mn, Thnh Ph Cn Th.

Vo Trng i hc An Giang nm 2001 hc lp DH2TP1, kha 2 thuc Khoa

Nng Nghip v Ti Nguyn Thin Nhin, tt nghip k s ngnh Cng Ngh ThcPhm nm 2005.


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LI CM T

tch ly c vn kin thc qu bu, c th hon thnh tt lun

vn tt nghip, l n su ngha nng ca tt c thy c, ngi thn, bn b-nhng ngi ch bo, gn gi, gip ti trong 4 nm qua.

Xin chn thnh cm n c Dng Th Phng Lin -Thc s Trng

i Hc Cn Th, Thy Trn Xun Hin-B mn Cng Ngh Thc Phm, khoa

NN-TNTN, i Hc An Giang tn tnh hng dn, gip , cung cp thng

tin, kin thc tht hu ch cho ti trong qu trnh nghin cu.

Cm n Ban Gim Hiu, qu thy c b mn Cng Ngh Thc Phm,

khoa NN-TNTN, Trng i Hc An Giang, cc ging vin HCT, gio vinphn bin, cc thy c ph trch th vin, phng th nghim, ha cht, thit

b nhit tnh ging dy, truyn t nhng kin thc qu bu, cng nh

to mi iu kin thun li nht cho ti trong sut thi gian hc tp v thc hin

ti.

Con xin ghi nh cng n ba m, ngi sinh thnh, dng dc, du

dt ti nhng bc i u i, to cho ti hnh trang v gi bc vo cuc

sng mi.

Li cm t sau cng xin dnh cho cc bn b ti, nhng ngi gn

gi, chia s, gip , v ng hnh vi ti trong sut qung i i Hc.

Long xuyn, ngy 25 thng 5, nm 2005

ngTh Cm T

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TM LC

Sa ln men Kefir l dng thc phm mang gi tr dinh dng cao, rt

cn thit cho con ngi v hin ang c sn xut ph bin nhiu nc trnth gii. y cn l sn phm c vai tr sinh hc rt cao i vi c th trong

trong vic chng lo ha v phng nga mt s bnh mng tnh. Tuy nhin,

Kefir vn cn kh xa l vi ngi tiu dng Vit Nam c bit l khu vc

BSCL. V th, gp phn gii thiu rng ri dng thc ung ny cng nh

gp phn lm a dng, phong ph nhng dng sn phm ln men t sa, ti

tin hnh nghin cu cc yu t nh hng n cht lng v tnh thng mi

cho sn phm Kefir trn c s chn la cc thng s ti u nht qua cc thnghim :

- Kho st nh hng ca thnh phn nguyn liu n qu trnh ln men

v cht lng sn phm. Th nghim tin hnh phi ch vi ng lactose 3

hm lng 0%, 5%, 10% v nc p du vi 3 t l 0%,10%, 20% so vi dch

sa, hm lng ng c sn trong sa nguyn liu l 4,6g/100ml, t l men l

4%, ln men nhit phng n acid dng 950T, sau tin hnh phi ch

thnh phm vi dch siro v bo qun 4-60C

- Kho st nh hng ca t l men ging n thi gian ln men v cht

lng sn phm.Th nghim kho st 4 t l men: 2%, 4%, 6%, 8%.

- Kho st acid dng thch hp kt thc qu trnh ln men. Th

ngim c kho st 4 mc: 850T, 950T, 1050T, 1150T.

- Kho st t l phi ch thch hp cho thnh phm vi siro nng 3

20%, 25%, 30% vi cc t l 20%, 30%, 40% theo dch sa.

- Kho st kh nng bo qun sn phm.

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Sau thi gian nghin cu, phn tch v tng hp s liu chng ti rt ra

cc kt lun nh sau:

- T l phi ch tt nht cho nguyn liu l 5% ng lactose v 10%

dch du- T l men ging thch hp nht l 6%

- acid dng thch hp nht l 1050T

- T l phi ch cho thnh phm l 30% dch siro nng 25%

- Thi gian bo qun tt nht l 15 ngy 4-60C

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MC LC

Ni dung Trang

CM T................................................................................................................i

TM LC.........................................................................................................iiMC LC...........................................................................................................iv

DANH SCH BNG....................................................................................... viii

DANH SCH HNH......................................................................................... ix

Chng 1 GII THIU......................................................................................1

1.1. t vn ......................................................................................................1

1.2. Mc tiu nghin cu......................................................................................1

Chng 2 LC KHO TI LIU..................................................................32.1. Gii thiu v nguyn liu.............................................................................. 3

2.1.1. Tnh cht l ha ca sa..............................................................................3

2.1.1.1. Sa l h phn tn cao.............................................................................3

2.1.1.2. chua ca sa.......................................................................................3

2.1.1.3. Tnh oxi ha ca sa................................................................................3

2.1.1.4. Khi lng ring......................................................................................3

2.1.1.5. p sut thm thu v nhit ng bng............................................... 42.1.1.6. Tnh khng khun....................................................................................4

2.1.2. Thnh phn ha hc ca sa.......................................................................4

2.1.2.1. ng lactose..........................................................................................6

2.1.2.2. Cht bo...................................................................................................7

2.1.2.3. Protein......................................................................................................7

2.1.2.4. Khong.....................................................................................................8

2.1.2.5. Vitamin....................................................................................................8

2.1.2.6. Hormone..................................................................................................8

2.1.2.7. Cc hp cht khc....................................................................................8

2.1.3. Thnh phn ha hc v gi tr dinh dng ca du Ty.......................... 10

2.2. C s khoa hc ca qu trnh ln men.........................................................10

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2.2.1. Ln men lactic.......................................................................................... 10

2.2.2. Ln men ethanol....................................................................................... 12

2.2.3. Cc yu t nh hng qu trnh ln men..................................................13

2.3. Gii thiu v ht Kefir.................................................................................152.3.1. Ngun gc ht Kefir................................................................................. 15

2.3.2. Thnh phn ht ging Kefir......................................................................16

2.3.2.1. Vi sinh vt trong ht Kefir.....................................................................16

2.3.2.2. Chu k pht trin ca ging Kefir......................................................... 18

2.3.2.3. Kefiran...................................................................................................21

2.4. Mt s loi vi khun lactic quan trng........................................................ 22

2.5. Dinh dng v li ch sc kho ca Kefir...................................................252.6. Phng php ch bin v bo qun ging Kefir..........................................25

2.7. Qui trnh ch bin Kefir...............................................................................27

2.7.1. Qui trnh sn xut men ging................................................................... 27

2.7.2. Gii thch qui trnh....................................................................................27

2.7.3. Qui trnh sn xut Kefir............................................................................28

2.7.4. Gii thch qui trnh....................................................................................28

Chng 3 PHNG TIN V PHNG PHP NGHIN CU................. 303.1. Phng tin..................................................................................................30

3.1.1. a im nghin cu.................................................................................30

3.1.2. Nguyn liu...............................................................................................30

3.1.3. Dng c v thit b....................................................................................30

3.1.4. Ha cht....................................................................................................30

3.2. Ni dung b tr th nghim.......................................................................... 31

3.2.1. Th nghim 1: Kho st nh hng ca thnh phn nguyn liu n qu

trnh ln men v cht lng sn phm................................................................31

3.2.1.1. Mc ch ...............................................................................................31

3.2.1.2. S b tr th nghim..........................................................................31

3.2.1.3. Chun b th nghim.............................................................................. 31

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3.2.1.4. Tin hnh th nghim.............................................................................32

3.2.1.5. Ch tiu xc nh....................................................................................32

3.2.2. Th nghim 2 Kho st nh hng ca t l men ging n thi gian ln

men c cht lng sn phm.............................................................................. 343.2.2.1. Mc ch ...............................................................................................35

3.2.2.2. S b tr th nghim..........................................................................34

3.2.2.3. Chun b th nghim.............................................................................. 35

3.2.2.4. Tin hnh th nghim.............................................................................35

3.2.2.5. Ch tiu xc nh....................................................................................35

3.2.3. Th nghim 3 Kho st nh hng ca acid dng n thi gian ln men

v cht lng sn phm...................................................................................... 353.2.3.1. Mc ch ...............................................................................................36

3.2.3.2. S b tr th nghim..........................................................................36

3.2.3.3. Chun b th nghim.............................................................................. 36

3.2.3.4. Tin hnh th nghim.............................................................................36

3.2.3.5. Ch tiu xc nh....................................................................................37

3.2.4. Th nghim 4: Kho st t l phi ch thch hp cho thnh phm............38

3.2.4.1. Mc ch ...............................................................................................383.2.4.2. S b tr th nghim..........................................................................37

3.2.4.3. Chun b th nghim.............................................................................. 38

3.2.4.4. Tin hnh th nghim.............................................................................38

3.2.4.5. Ch tiu xc nh....................................................................................38

3.2.5. Th nghim 5 Kho st v tm ch bo qun thnh phm....................39

3.2.5.1. Mc ch................................................................................................38

3.2.5.2. Tin hnh th nghim.............................................................................38

3.3. Phng php phn tch v x l s liu....................................................... 38

3.3.1. Phng php phn tch............................................................................. 40

Chng 4 KT QU V THO LUN..........................................................40

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4.1. nh hng ca thnh phn nguyn liu n qu trnh ln men v chtlng

sn phm.............................................................................................................40

4.2. nh hng ca t l men ging n thi gian ln men

v cht lng sn phm..................................................................................... 454.3. nh hng ca acid dng n thi gian ln men

v cht lng sn phm...................................................................................... 49

4.4. nh hng ca t l phi ch sau ln men n hnh thi

v cht lng sn phm...................................................................................... 51

4.5. nh hng ca thi gian bo qun n cht lng sn phm ....................52

Chng 5 KT LUN V NGH............................................................... 54

Ph chng I................................................................................................... pc-1Ph chng II.................................................................................................. pc-4

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DANH SCH BNG

Bng s Ta bng Trang

1 Mi lin h gia cc n v o chua ca sa................................. 3

2 Thnh phn ca mt s loi sa.......................................................... 4

3 Cc thnh phn chnh ca mt lt sa..................................................4

4 Thnh phn ho hc ca du ty....................................................... 10

5 Bin i cc thnh phn ca sa to thnh Kefir.............................. 14

6 Cc vi sinh vt c trong ht Kefir......................................................197 Gi tr nhit v pH ti u cho s sinh trng ca mt s loi

vi khun lactic....................................................................................24

8 Bng im nh gi cm quan sn phm Kefir.................................33

9 nh hng ca hm lng ng lactose v nc p du n

thi gian ln men, cn v mt s vi sinhvt................................. 40

10a Kt qu nh gi cm quan mi v sn phm ( tng nhn t)........... 44

10b Kt qu nh gi cm quan mi v sn phm ( tng tc 2 nhn t).4511 nh hng ca t l men n cn, nm men, vi khun

v thi gian ln men.......................................................................... 46

12 Kt qu cm quan mi v sn phm...................................................48

13 Kt qu cm quan mi v v hnh thi sn phm...............................51

14a Kt qu cm quan mi, v v hnh thi sn phm theo thang im

m t (tng nhn t)......................................................................... 51

14b Kt qu cm quan mi, v v hnh thi sn phm theo thang im

m t (tng tc 2 nhn t)...............................................................52

15 Bng ch tiu l ho, vi sinh ca sn phm theo thi gian bo qun..53

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DANH SCH HNH

Hnh s Ta hnh Trang

1 S tm lc chuyn ho cc cht trong qu trnh ln men sa..........12

2 Ht Kefir sau khi c vt ra khi sa...................................................16

3 Hnh dng, kch thc ht Kefir nguyn vn sau khi ct i.............17

4 nh chp ht ging Kefir di knh hin vi in t gm

vi khun nm men v cc cht gian bo.................................................18

5 Ht Kefir v bo qun ht Kefir..............................................................26

6 Nguyn liu dng cho ch bin sa Kefir...............................................39

7 th biu din s tng quan gia acid theo hm lng ng

lactose v dch du........................................................... 41

..............................................................................................................................42

8 th biu din s tng quan gia cn theo hm lng ng

lactose v dch du................................................................................. 42

9 th biu din s tng quan gia mt s nm men theo ng lactose

v dch du.............................................................................................. 43

10 S tng quan gia mt s vi khun theo hm lng lactose v

dch du..........................................................................................43

11 S tng quan gia acid v cn theo t l men ging...................47

12 S tng quan gia acid v thi gian ln men theo t l men ging..47

13 S tng quan gia mt s nm men v vi khun theo t l men ging.48

14 S tng quan gia thi gian ln men v cn theo acid dng......51

15 Sn phm Kefir....................................................................................... 54

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Chng 1 GII THIU

1.1. t vn

Ngy nay, sa ln men chua l mt trong nhng sn phm ang c

a dng v p ng nhu cu ngy cng cao ca con ngi. Ngoi vic cung

cp ngun dinh dng thit yu, n cn c bit n vi tnh cht khng

mt s bnh: ung th, chng lo ho v tng cng tiu ho. Mang y

tnh cht trn v ang c tim nng pht trin cao trn th gii - Sa Kefir

(mt sn phm sa chua mi) cn c quan tm nghin cu v pht trin.

Khc vi sa chua thng thng, Kefir l sn phm va ln men lactic nh

nhm vi khun lactic a m, va ln men ru nh nm men. Sn phm t

lu c bit n nh mt loi thuc thin nhin vi nhiu dc tnh c

minh chng qua qu trnh s dng nhiu vng trn th gii, n gip tng

cng kh nng min dch, gim cng thng thn kinh, lm tan sn mt, sn

thn, iu ho huyt p, lm ngng s tng trng ca t bo ung th v

nhng li ch sc kho khc m cho n nay vn cn c xem l nhng iu

b mt.

Song, sn phm ny tuy c mt t rt lu i trn th gii, nhngvn cn rt mi trn th trng tiu th Vit Nam. Do , gp phn gip

cho sn phm Kefir ngy cng ph bin v quen thuc vi ngi tiu dng,

vic nghin cu nng cao cht lng v lm a dng phong ph cho sn

phm Kefir s c gii thiu lun vn ny.

1.2. Mc tiu nghin cu

Sa kefir s c nghin cu ch bin phng th nghim vi trng

tm l gii quyt cc vn c lin quan n cht lng v thi gian bo

qun. Trn c s ti nghin cu cc vn sau:

- Kho st nh hng ca thnh phn nguyn liu n qu trnh ln

men v cht lng sn phm.

- Kho st nh hng ca t l men ging n qu trnh ln men v

cht lng sn phm.

- Kho st nh hng ca acid dng n cht lng sn phm.

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- Kho st t l phi ch thch hp cho thnh phm.

- Kho st kh nng bo qun thnh phm.

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Chng 2 LC KHO TI LIU

2.1. Gii thiu v nguyn liu2.1.1. Tnh cht l ho ca sa

2.1.1.1. Sa l h phn tn cao

Cc thnh phn ca sa tuy c tnh cht khc nhau nhng khi ha vo

mi trng nc c th ng nht v phn tn cao. Lactose v glucose tan

trong nc dng phn t, cn mui ca acid hu c, v c tn ti dng

ion. Protein dng keo, cht bo sa dng ht phn tn cao.

2.1.1.2. chua ca sa

C nhiu n v biu din chua ca sa nh Soxhlet Henkel

(0SH), Thorner (0T), Dornic (0D). Thng thng chua ca chun

c nh ngha l s ml dung dch NaOH 0.1N dng trung ha acid ca

100ml dch sa. Sa thng c chua trung bnh l 16180 T ( Thorner).

Bng 1: Mi lin h gia cc n v o chua ca sa

0SH 0Th 0D0SH 1 2,50 2,250Th 0,40 1 0,900D 4/9 10/9 1

(Lm xun Thanh, 2003)

2.1.1.3. Tnh oxi ho kh ca sa

Do trong sa cha nhiu cht c kh nng kh hay oxi ha nh: acid

ascorbic, tocopherol, riboflavin, systin, men..lm cho sa cng c tnh cht

.

2.1.1.4. Khi lng ring

Khi lng ring ca sa ph thuc hm lng cht bo cng nh

cc cht tan trong sa. Trung bnh sa c khi lng ring d = 1,0271,032,

s liu ny thay i ty ging, loi, thi k cho sa. Khi pha thm nc vo

sa s lm thay i gi tr ny.

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2.1.1.5. p sut thm thu v nhit ng bng

p sut thm thu (Ptt) ca sa c to ra bi nhng cht phn tn

cao nh ng lactose, mui. Bnh thng Ptt = 6 atm 00 C.

Nhit ng bng ca sa l -0,550

C. Cn c vo nhit ngbng c th bit c sa c b pha thm nc vo hay khng.

2.1.1.6. Tnh khng khun

Sa khi mi vt xong, thng vi sinh vt khng pht trin c m

c th b tiu dit v trong sa c cht khng th.

2.1.2. Thnh phn ho hc ca sa

Nguyn liu s dng chnh trong sn xut Kefir l sa, thnh phn c

bn trong sa cc loi ng vt bao gm nhm ch yu nh bng 2

Bng 2:Thnh phn ca mt s loi sa

Loi sa Protein

%

Casein

%

Whey protein

%

Cht bo

%

Cacbohydrat

%

Tro

%Sa m 1.2 0.5 0.7 3.8 7.0 0.2

Sa nga 2.2 1.3 0.9 1.7 6.2 0.5Sa b 3.5 2.8 0.7 3.7 4.8 0.7

Sa tru 4.0 3.5 0.5 7.5 4.8 0.7Sa d 3.6 2.7 0.9 4.1 4.7 0.8Sa cu 5.8 4.9 0.9 7.9 4.5 0.8

(L Th Lin Thanh, 2003)

Bng 3: Cc thnh phn chnh ca mt lt sa

Cc thnh

phn

M t Trng

lng

%

Nc Pha lng 902 87,40

Glucid(40-60g/l)

Dng t do: lactose ( do galactose vglucose) trng thi phn t.

Dng kt hp: galactose, galactozamin,

acid sialic trng thi keo, c lin kt

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bo: cc sc t ( caroten),

sterol(cholesterol), cc vitaminHp cht

Nit(25-40 g/l)

dng mixen 28g: dng huyn ph, l

phc ca phosphat canxi lin kt vi mtlin hp ca casein.

dng ho tan 4,7g: l nhng cao phn t

ca albumin v imunoglobulin

Nit phi protein 0,3g: ure axit uric creatin

33 3,20

Cht khong

(25-40g/l)

trng thi keo v ho tan:

dng phn t v ion: axit citrit, K, Ca, P,

Na, Cl, Mg dng cc nguyn t trung lng

(oligo-elemen): Zn, Al, Fe, Cu, I

9 0,87

Cht kh

tng s

(MST)

Sa c lm bc hi nc

130 12,60

Cc cht

khc

Cc cht xc tc sinh hc: cc vitamin (A,

D, E, K, B1, B2, PP, B6, B12, C) v cc

enzim.

Cc kh ho tan: CO2, O2, N2 chim 45%

th tch sa

Vt

(Lm Xun Thanh, 2003)

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2.1.2.1. ng lactose

Lactose l mt disaccharide do mt phn t glucose v mt phn t

galactose lin kt vi nhau to thnh. Trong sa ng lactose tn ti di

hai dng:- Dng -lactose monohydrat C12H22O11.H2O (phn t -lactose ngm

mt phn t H2O)

- Dng -lactose anhydrous C12H22O11 (phn t -lactose khan). T l

hm lng gia -lactomonohydrate v -lactose anhydrous trong sa ph

thuc vo gi tr pH v nhit ca sa.

Khi ho tan ng -lactose monohydrat dng tinh th vo nc, gc

quay cc ca dung dch s l +89,40C

Nu gi dung dch ny nhit phng, sau 24 gi gc quay cc s

gim xung gi tr +550. l do mt s phn t -lactose monohydrat

chuyn sang dng -lactose anhydrous. Khi dung dch s tn ti cn bng:

L--lactose monohydrat L--lactose anhydrous

Vic gim gi tr gc quay cc ca dung dch - lactose monohydrat

s din ra vi tc nhanh hn nu pH c kim ho v gi tr 9,0 hoc

dung dch c gia nhit 750C.

Lactose l ng kh, ngt ca lactose thp hn nhiu so vi cc

disacharide v monosacharide thng gp. Nu nh ngt ca saccharose

c nh gi vi ch s 100, ca maltose l 32, glucose l 74 v fructose l

173 th ngt ca lactose ch t 16. Lactose c th b thu phn to ra 2

monosacharide l glucose v galactose bi enzim -galactoside (lactase)

Cc ng n gin nh glucose, fructose, saccharose, c nhiutrong thc vt (hoa, tri cy cc loi). Tuy nhin ch c sa ng vt l ngun

cha lactose duy nht trong t nhin

Ngoi lactose, trong sa cn c glucose (hm lng trung bnh

70mg/l), galactose (20mg/l) v cc hp cht glucid cha Nit nh N-acetyl

glucosamine, N-acetyl galactosamine, acid N-acetyl neuraminic... Tuy nhin,

hm lng ca chng rt thp, ch dng vt.

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2.1.2.2. Cht bo

L thnh phn quan trng, v dinh dng cht bo c sinh nng

lng cao, cha cc vitamin trong cht bo (A, D, E). Vi sn phm sa ln

men, cht bo nh hng ti mi v, trng thi sn phm. C 9899% chtbo l triglyxerid, 12% cn li l cc phospholipid, cholesterol, vitamin A,

D, E, K.

Trong sa c 18 acid bo. Mi glyxerol c th kt hp vi 3 acid bo

cng loi hoc khc loi nn s glyxeride khc nhau l v cng ln. Lp

vng sa trn b mt c nhiu th hnh cu kch thc khc nhau ni t do

trong sa, mi th cu c bao bc bng mt mng mng. Th cu m ny

c mng bao t protein v cc phosphatide (rt bn) c tc dng bo v gi

cho chng khng b ph hy bi cc enzim trong sa (ng knh cu m

0,120m (trung bnh 34 m), c 3000 n 4000 triu cu m/1ml sa, l

thnh phn nh nht trong sa (t trng 0,925g/cm3) v c xu hng ni ln

b mt. Phn cn li ngoi cc cu m l sa gy.

Acid bo chim 9899% tng cht bo, khc vi m ng vt l

cha nhiu acid bo no khi lng phn t thp.2.1.2.3. Protein

Bao gm casein t 24,5%, -lactose albumin: 0,5%1% -lactose

globulin 0,1%, khong 0,1% l cc protid khc.

Protein sa l loi protid hon thin cha hu ht cc loi acid amin

c trong t nhin v c t l cn i thch hp cho s hp thu v ng ho ca

c th ngi. Casein c tnh cht keo, c ng dng rng ri trong cng

nghip ch bin sa. Casein thng dng phc cht casein-calci-phosphat

bn vng vi hai lp bo v (lp in tch tri du v lp nc lin kt, cc

phc cht lin kt li vi nhau to thnh kt ta (keo ho), c th keo ho

bng acid lactic hoc men chyomozin theo phn ng:

H+

Casein-calci-phosphat Casein trung ho v in (kt ta)

Casein-Calci-phosphat Paracasein + Ca2+ (kt ta)

Chymosin

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21/81

Sa tch casein bin thnh dng trong, nc cn li cha cc

protein ho tan nh -lactose-globulin v globulin khng th c gi l cc

protein nc sa (whey). Cc cht cha nit phi protein bao gm cc acid

amin t do, creatin, acid uric, polipeptit, ure Trong tt c hp cht trn thacid amin l c ngha hn c.

2.2.2.4. Khong

Hm lng cht khong trong sa dao ng t 810g/l cc mui

trong sa dng ho tan hoc dung dch keo (kt hp vi casein)

Trong s cc nguyn t khong c trong sa, chim hm lng cao

nht l calci, phospho v magie. Mt phn chng tham gia vo cu trc

micelle, phn cn li nm di dng mui ho tan trong sa. Cc khong

khc nh K, Na, Cl ng vai tr cht in ly. Cng vi lactose chng gp

phn cn bng p lc thm thu ca sa trong bu v ng vt vi p lc

mu.

Ngoi ra, sa cn cha cc nguyn t khc nh Zn, Fe, I, Cu, Mo.

Chng rt cn thit cho qu trnh dinh dng ca con ngi. Mt s nguyn

t c hi nh Pb, As i khi cng c tm thy dng vt trong sa b.2.1.2.5. Vitamin

Vitamin sa c chia lm hai nhm: Vitamin ho tan trong nc

gm B1, B2, B3, B5, B6, Cv vitamin ho tan trong cht bo gm A, D, E, K.

Nhn chung hm lng vitamin nhm B trong sa b thng n nh do

chng c tng hp ch yu bi vi khun trong ngn th nht d dy ca

nhm ng vt nhai li v khng ph thuc vo iu kin ngoi cnh. Tuy

nhin, hm lng vitamin tan trong cht bo b nh hng su sc bi thnhphn thc n v iu kin thi tit.

2.1.2.6. Hormone

Hormone do cc tuyn ni tit tit ra v gi vai tr quan trng trong

qu trnh sinh trng ca ng vt. Trong sa b ta c th tm thy nhiu loi

hormone, chng c chia thnh 3 nhm l proteohormone, hormone peptide

v hormone steonide, trong s prolactine c nghin cu nhiu hn c.

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Hm lng trung bnh prolactine trong sa b l 50g/l, trong sa non l

23mg/l. a s b mt hot tnh khi thanh trng nhit thp (60650C).

2.1.2.7. Cc hp cht khc

Trong sa b cn cha cc cht kh, ch yu l CO2, O2 v N2. Tnghm lng chng chim t 56% th tch sa. Cc cht kh trong sa thng

tn ti 3 dng: dng ho tan, dng lin kt ho hc vi cc cht khc v

dng phn tn. Kh dng ho tan hay phn tn thng gy ra mt s kh

khn trong cc qui trnh ch bin sa. Do sa ti thng c qua x l

bi kh trc khi ch bin.

Thnh thong ngi ta cn pht hin trong sa c cc hp cht ho

hc khc nh:

- Cht khng sinh: penicilline, chloramphenicol...

- Cht ty ra: nc Javel, kim...

- Pesticide: heptachlore v cc epoxyde, aldride duldrine, chlordane.

- Kim loi nng

- Nguyn t phng x, nitrat, c t vi sinh vt.

Nhng hp cht ny gy c cho ngi s dng. Hm lng chngtrong sa thng dng vt v thng nhim vo sa t ngun thc n, thit

b, dng c cha v mi trng chung tri...

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2.1.3. Thnh phn ha hc v gi tr dinh dng ca du Ty

Bng 4: Thnh phn ha hc ca du Ty

Thnh phn Hm lng n vNc 89,90 gProtein 0,70 gBo 0,50 gCabohydrat 8,40 gCa 21,00 mgP 21,00 mgFe 1,00 mg

Na 1,00 mgPotassium 164,00 mgMg 12,00 mg

Vitamin A 60,00 UIVitamin B1 0,03 mgVitamin B2 0,07 mgVitamin C 59,00 mg

Niacin 0,60 mgNng lng 37,00 Cal

(Nguyn Minh Thu, 2003)

2.2. C s khoa hc ca qu trnh ln men

2.2.1. Ln men lactic

Trong cng ngh vi sinh vt, nhn chung vi khun lactic ng hnhlun chim u th. Tuy nhin, trong cng ngh sn xut cc thc phm ln

men truyn thng nh phomai, Kefir, vi khun lactic d hnh i khi vn c

s dng nhm mc ch a dng ho ch tiu v mi v v cu trc cho sn

phm.

Qu trnh ln men din ra trong t bo cht ca vi khun. u tin

ng lactose trong sa c vi khun lactic a vo t bo nh c ch vn

chuyn c trng ca mng t bo cht (Cytoplasmic membrane). Tip theo

lactose s c phn thnh 2 monosacharide ri i vo cc chu trnh chuyn

ho khc nhau.

i vi nhm vi khun lactic ng hnh nh gingLactococcus, cc

loi Streptococcus thermophylus, Lactobacilus bulgaricus, Lactobacilus

helveticus, Lactobacilus lactic.... chu trnh ng phn l con ng chnh

chuyn ho glucose thnh acid lactic.Phng trnh tng qut ca ln men ng hnh:

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C6H12O6 + 2ADP + 2Pi 2CH3-CH-COOH + 2ATPOH

Ln men lactic l mt qu trnh trao i nng lng. Cc phn t

ATP c hnh thnh trong qu trnh chuyn ha c cht (lactose) s c vi

khun gi li trong t bo phc v cho qu trnh trao i cht v sinh

trng ca vi sinh vt. Ngc li, cc sn phm nh acid lactic, ethanol, CO 2

c vi khun thi vo mi trng ln men. Kt qu l hm lng acid lactic

tch lu trong mi trng ln men ngy cng tng, lm gim pH mi trng

v ko theo nhng bin i ha l khc.

Trong qu trnh ln men lactic ngoi sn phm acid lactic (ln men

ng hnh), acid acetic, ethanol, CO2 (ln men d hnh) trong dch ln men

cn xut hin c trm hp cht ha hc mi khc. Chng l sn phm trung

gian hoc sn phm ph ca qu trnh ln men. Hm lng ca chng trong

dch ln men thng rt thp (vi ppm hoc t hn). Mt s hp cht trong

nhm trn rt d bay hi. Chng ng vai tr quan trng trong vic gp phn

hnh thnh nn mi v c trng cho nhng sn phm ln men lactic. ng

ch nht l diacetyl v acetaldehyde, y l nhng hp cht quan trng

quyt nh n mi v c trng cho sn phm ln men t sa.

Lactose

Glucose Galactose

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Sn phm trung gian AcetaldehydeC2H5OH

CH3CHO

+CO2,CH3CHOAxit Pyruvic

CH3COCOOH Acetoin+1/2O2 CH3COCHOHCH3

+ 2H +2H2O +1/2O2 -2H+2H

Axit lactic axit lactic CO2 + CH3COOH CH3COOH DiaxetylCH3COCOCH3Ln men Ln men d thng th

Hnh 1: S tm lc chuyn ho cc cht trong qu trnh ln men sa

T l hm lng diacetyl v acetaldehyde nh hng n gi tr cm

quan ca yaourt v b. T l ny ph thuc vo thnh phn cc vi sinh vt s

dng trong t hp ging v cc thng s k thut ca qu trnh ln men nh

nhit , pH u, lng ging cy...

2.2.2. Ln men ethanol

Trong cng ngh sn xut cc sn phm ln men t sa, qu trnh ln

men ethanol c thc thc hin ch yu bi cc nm men thuc ging

Sacharomyces vKluyveromyces. Sau khi c vn chuyn vo trong t bo

cht, ng hexose c chuyn ha theo chu trnh ng phn to thnh

acid pyruvic. Tip theo acid pyruvic s c chuyn ho thnh acetaldehyderi thnh ethanol

Dihydroxyacetone phosphat l mt sn phm trung gian trong chu

trnh ng phn, hp cht ny c th chuyn ho thnh glyxerol.

Trong mi trng pH acid, glycerol ch c to ra vi hm lng

nh. Ngc li, trong mi trng pH kim lng glyxerol sinh ra s tng ln

rt nhiu v glycerol s tr thnh mt trong nhng sn phm ch yu ca qu

trnh ln men.

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Phng trnh tng qut ca qu trnh ln men trong mi trng pH acid

C6H12O6 + 2ADP +2Pi 2 C2H5OH + 2CO2 + 2ATP

S chuyn ha ng hexose thnh ethanol v kh CO2 din ra trong

t bo cht ca nm men. y l qu trnh trao i nng lng ca nm men

trong iu kin k kh. Ethanol v CO2 trong t bo cht s c nm men

thi vo mi trng ln men. Ngoi ra t bo nm men cn tng hp v thi

vo dch ln men hng trm sn phm ph v sn phm ln men khc, nhng

hp cht ny c tm thy vi hm lng rt nh, chng c chia thnh 4nhm: glyxerol cng ru bc cao, aldehyde, acid hu c v ester.

Trong qu trnh ln men ethanol, nhiu acid hu c c to thnh

(The Moll, 1990). Mt s acid hu c c sinh tng hp t chu trnh Crebs

nu nh qu trnh ln men khng din ra trong iu kin k kh nghim ngt,

cc acid hu c chim hm lng cao nht trong dch ln men l: acid citric,

malic, acetic, lactic...

2.2.3. Cc yu t nh hng qu trnh ln menCc qu trnh ln men trong sn xut cng nhip c th tm tt nh sau:

Mi trng trc khi ln men Mi trng sau ln men

Trong cng nghip sn xut cc sn phm ln men t sa nh: yaourt,

Kefir... . Cc giai on x l sn phm sau qu trnh ln men thng n

gin, sn phm cui cng bao gm c sinh khi vi sinh vt, cc sn phm trao

i cht ngoi bo do vi sinh vt tit ra v c cht st. Thnh phn v hm

lng ca tng cht s gp phn hnh thnh nn hng v sn phm. Do , sn xut thc phm ln men vi cht lng mong mun, cn phi:

13

C cht + ging vi sinh vt

C cht st + sinh khi vi

sinh vt + sn phm trao

i cht ngoi bo do vi

sinh vt tng hp nn.


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- Chn c ging vi sinh vt thch hp.

- Xc nh mi trng ln men vi c cht y theo t l ti u.

- Xc nh c cc iu kin ln men thch hp nh lng ging

cy nhit v thi gian ln men. Ngoi ra cn phi quan tm n nhng vn nh cung cp oxy v khuy trn.

Bng 5: Bin i cc thnh phn t sa to thnh Kefir

Thnh phn Ch thch

Cht bo Ph thuc ngun sa ban u (b, d...) v lng bo

ca sa c dng (nguyn bo, tch bo mt phnhay khng bo)

Lactose Tiu th mt phn lactose, bi vi khun lactic v nmmen. Lactose trn 100 g sn phm sa Kefir: 22,5 g

Acid lactic Hnh thnh bi vi khun lactic. Trn 100 g sn phmsa Kefir c 0,61 g

Protein Chim 33,4 g/100 sn phm sa Kefir

Ethanol Sn sinh bi nm men nu dng men: lng cn l

0,010,1/100 g sa, nu dng ht Kefir lng cn l0,021,8 g/100 g sa

Cc acid hu ckhc

Axetic, fomic, propionic, Succinic, pyruvic, isobutyric, caproic, acid lauric gp phn to hng choKefir hay c tiu th bi chnh loi vi khun trongsut qu trnh ln men.

CO2 Sinh ra nh nm men v vi khun lactic ln men d thsinh CO2 to tnh c trng cho Kefir.

Hp cht thm Acetaldehyde, diacetyl, acetone gp phn vo hng

ca sn phmVitamin Tng vitamin B (i vi sa cu), pyridoxine (t sa

cu, d, nga), acid folic (tr sa nga), orotic,nicotinic, acid pantothenic: khng i hay gim khi cc

(Nguyn T Thanh, 2003)

2.3. Gii thiu v ht kefir

2.3.1. Ngun gc ht Kefir

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Cch y hng nghn nm, Kefir c bit n nh mt th nm

dng cha bnh, n xut x t cch nui ring ca cc tu s n Tng . y l

loi nm vi khun c th lm bin i sa nh mt h vi sinh vt phc tp

gm nhiu loi vi khun v nm men c chng minh l rt c li cho sckho. Dn min ni Caucasus thuc nc X Vit c - nguyn qun ca

Kefir - bo ch n t sa ca cc sinh vt khc nhau v Kefir c ln

men t nhin trong nhng ti da th, theo cc b tc ngi y h xem

Kefir nh l qu tng ca ng Allah, nh ngun ti sn ca gia nh v ca

b tc, h tiu th Kefir t thu u th v c nh vy duy tr t th h ny

n th h khc. H khng h bit n bnh ung th, bnh lao, bnh d dy..

v h th n trung bnh l 110 tui. Ni Caucasus l vng duy nht trn a

cu m ngi ta t sc kho hon ton la tui ny. T rt sm cc bc s

Nga rt tin tng rng Kefir c li cho sc kho v c kh nng cha

bnh.

Mi n nhng nm u ca th k 20 ht Kefir mi c sn xut

vi s lng nh Moscow . Nguyn liu sn xut Kefir c th l sa d,

sa cu hay sa b. Theo Oberman H v Libudiziz Z (1998) u tin ngi ta

ln men sa thnh Kefir trong cc ti bng da th hoc bn bng g si. n

cui th k 19, Kefir tr thnh sn phm quen thuc ca dn cc nc vng

ng u (Nga, Ucraina, Balan, Czech, Hungari...) v cc nc vng

Scandinavia. Tuy nhin sn xut sn phm Kefir cho mc ch thng mi

m vn gi c cht lng nh sn phm truyn thng l mt iu khng d

dng v theo truyn thng th ngi ta khng s dng nhng vt dng bng

kim loi cho qu trnh ch bin m ch t cc dng c bng g, t st hocda th. n 1950, mt phng php sn xut Kefir mi c cng nhn

v cht lng l phng php ln men c khuy trn.

Hin nay c hai loi Kefir, mt loi c v ngt c ln men vi

nc tri cy v ng, mt loi c ln men t sa. H vi sinh vt s dng

trong sn phm Kefir bao gm vi khun lactic v nm men. Chng cng pht

trin cng sinh trn mi trng sa. Do sn phm Kefir c v chua c

trng v thong nh mi nm men.

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lun vn ny s nghin cu s ln men kt hp gia hai loi nc

p tri cy v sa, mt loi sn phm khc vi nhng loi sa ln men truyn

thng nh yaourt vi hng v rt mi l, c trng v c li cho sc kho.

Hnh 2: Ht Kefir sau khi c vt ra khi sa(www.Kleibers.de/.../guido/4a_kefir_tibet.jpg)

2.3.2. Thnh phn ht ging Kefir

2.3.2.1. Vi sinh vt trong ht Kefir

Trong sn xut Kefir, ngi ta s dng t hp ging vi sinh vt di

dng ht Kefir ( Kefir Grains). Cc ht Kefir c mu t trng n vng nht,

hnh dng khng n nh v thng kt thnh chm vi nhau to dng tng

t hoa Chou-fleur vi ng knh trung bnh 0,32 cm. Ht Kefir l phc h

vi sinh vt gn vi nhau bi cht polisacharide. Ging ny bao gm vi khun

lactic (Lactobacilli, Lactococci, Leuconostoc..) v nm men. i khi ta cntm thy vi khun A.aceti vA.racens cng vi cc vi sinh vt khc t chc

thnh khi cu vi sinh vt . Tuy vn cha c lm sng t hon ton nhng

t hng nghn nm qua s tiu th chng minh c rng h vi sinh vt

trong Kefir l khng gy bnh m cn c kh nng ngn chn s pht trin

ca vi sinh vt gy bnh nh Salmonella hay Singella.

16
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Hnh 3: Hnh dng, kch thc ht Kefir nguyn vn v sau khi ct i.

(http://user.chairot.net.au/~dna/thumb3-WKG.jpi)

Polisacharide ch yu l nc, vt cht ho tan c bit l

Kefiranofaciens vL. kefirsn sinh ra polisacharide ny. Chng l mt phn

ca ht, nu khng c s hin din ca chng th ht Kefir khng th hnh

thnh. Ngoi t bo vi sinh vt, ht Kefir cn cha protein (chim khong

30% tng cht kh) v Carbohydrate (2550%). Nh vy t mt s thng tin

a ra thnh phn hp thnh ca ht ging Kefir l phc protein

Polisacharide bo. Thnh phn ht ging sy kh ng lnh vi hm m 3,5%

c tm thy bao gm: bo 4,4%, tro: 12,1%, Muco-polisacharide (Kefiran):

45,7%, protein tng s 34,3% gm c: protein khng ho tan 27%, protein

ho tan 1,6% v acid amin t do l 5,6%.

Nhm vi khun lactic lactobacilli chim khong 65-80% tng s vi

sinh vt trong ht Kefir. Chng gm nhng loi a m v a nhit thc hin

qu trnh ln men lactic theo c ch ln men ng hnh ln d hnh. Nhm vikhun lacticLactococci chim 20% tng s t bo,Bacilli 69%, Streptococci

11-12%

Ring nm men chim 510% tng s vi sinh vt trong ht gm

nhng loi ln men c ln khng ln men c ng lactose. Cc loi

nm men ln men c ng lactose thng c tm thy ti cc v tr gn

b mt ht Kefir. Ngc li, cc loi nm men khng ln men c ng

lactose li tm thy ti cc v tr su bn trong tm ht

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Hnh 4: nh chp ht ging Kefir di knh hin vi in t gm vi

khun, nm men, v cc cht gian bo

(Kefir.vilabo.oul.com)

2.3.2.2. Chu k pht trin ca ging Kefir

Kefir l nhng ging gc t nhin, chng c hnh thnh t nhng

mng bao bc mng khng theo mt quy tc no c bao gm hn hp protein,lipid, polisacharide. Nhng mng bao bc pht trin vi hnh dng khng

nht nh, hnh thnh cc thu phc tp v khng ng u, cc thu ny li

c xu hng tr v nguyn bn to thnh cu trc sinh hc bao gm nhiu

thu con bao quanh mnh. Vi du hiu pht trin c bit nh th chng

hnh thnh nhng ht con, mi tiu thu c kt ni vi nhau phn gia,

xe ra trong khi n c gn vi cc im trung tm ca ht ging m.

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Bng 6: Ccvi sinh vt c trong ht Kefir (Oberman H v cng s, 1998)

Ging vi sinh vt LoiVi khun

Lactobacilli

Streptococci

Lactococci

Leuconostoc

Acetobacter

Lb. brivis

Lb. cellobiosus

Lb. acidepphilus

Lb. Kefir

Lb. casei ssp. alactosus

Lb. casei ssp. rhamnosusLb. helveticus. ssplactis

Lb. delbruevii.ssp.lactic

Lb. paracasei.ssp.paracasei

Lb. casei

Lb. lactis

Lb. plantarum

Lb. delbrueckii. ssp. hulgaricusLb. fructivorans

Lb. hilgardii

Lb. kefiranofaciens

Lb. kefirgarnum sp.nov

Lb. parakefir sp.nov

S. thermophilus

S. lactisS. filant

S. durans

Lc. lactis.ssp.lactis

Lc. lactis.ssp.lactisvar diacetylactis

Lc. lactis.ssp.cremoris

Leuc. mesesteroides.ssp.dextranicum

Leuc. mesenteroides.ssp.cremoris

Acetobacters casei

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Acetobacters rasens

Nm men

Kluyveromyces

Sacchromyces

Candida

Torulaspora

K. lactis

K. marxinnus. ssp. bulgaricus

K.morxianus. ssp. marxianus

S. lactis

S. cerevisiae

S. florentinus

S. globosus

S. unisporus

S.carlsbergensis

S. ssp. torulopsis holmii

C. kefir

C. pseudotropicalis

C. tenuis

C. rancens

T. delbrueckii

(L Vn Vit Mn, 2004 v cc ngun trn internet)

Nh s xut hin m cc ht con tch ra c mu hnh pht trin

ging nh ht m ban u. Mt vi ht Kefir cng tch ra ging vi cu trc

vt l ca no ngi, tuyn ty v cc c quan bn trong. Sau mt thi gian

c th do chn thng hoc nhng tc ng bn ngoi, mt phn thy con

gn vi ht m b tch ra thnh ht t do. Nhng ht con ny li tip tc nhn

ging thnh ht m. Chu k pht trin c lp li vi chu trnh gn ging

nhau (t nhn ging). Trong vi trng hp c bit, c nhng ht khng thcho ra bt c ht con no trong mt thi gian di m thay vo , chng hnh

thnh nn mt khi ln (khi ht Kefir)

B mt ngoi ca ht bin i t dng phng n khng ng u

gm nhiu th phc tp, c nhng ch li lm ri rc khp b mt. Mt vi

ht c th c nhng vng rng phng, trong khi t m tng t c th c

nhng ht c b mt khng ng u. Nu iu kin thun li, sau mt thi

gian, nhng ht nhn ny thng tr li dng nguyn th, sau hnh thnh

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cc ht bao quanh mnh, ni m c th nhn ging ln. Thng nhng vng

khng phng, x x thng c s hot ng mnh ca nm men, trong khi

vng phng vi khun li chim u th. Nm men hnh thnh nhng khm nh

nh ra trn b mt, Streptococci th bn vo nhau vi cc vi khun khc chkhng hnh thnh dng cm

su bn trong ht,Lactobacilli chim u th v c rt t t bo nm

men, chng c gi gn trong dch polisacharide, cc vi khun hnh que v

nm men hnh thnh cc cm ring bit bn ngoi v bn trong ht.

Lb.Kefiranoficients c xem l nguyn nhn hnh thnh polisacharide ha

tan Kefiran. Trong khi L. bacitophilus l nguyn nhn hnh thnh v bc

bn ngoi polisacharide m c th gip ht co gin. Mt s nghin cu cho

rng vi khun c th gy ra s nhn ging ht Kefir v vic nhn ging ca

ht khng xy ra khi vng mt Lb. kefiranoficients - l vi khun sinh ra

Kefiran trung tm ht.

2.3.2.3. Kefiran

C ch phc tp v cu trc gian bo vi sinh vt trong ht Kefir hin

nay cha c gii thch r rng. Ngi ta khm ph c gel ha tan

polisaccharide trong ht kefir l iu duy nht cho tn gi kefiran (KGF-

C). Ht kefir sy kh bao gm cht gian bo khong 45% l kefiran.

Polisaccharide ny gm hai ng n glucose v galactose vi t l cn i.

Kefiran hnh thnh trung tm ht, vi iu kin k kh thun li cho vic

tng hp kefiran trong s hin din ca ethanol. Mt vi loi Lactobaccilli

khc cng sinh ra polisaccharide nh Lb. brevis, Lb. sp.

Cc loi Lactobaccilli khc nhau c th sn sinh ra dng gelpolisaccharide gn ging nhau tc khc nhau. y l mt phn trong c

ch phc tp ca ht kefir. C th do nhng khuynh hng khc nhau ny m

Lactobaccilli sn sinh cc phn trung tm ht.

Mt th nghim trn chut pht hin tnh khng ung bu ca

Kefiran. Trong th nghim ny kefiran c cung cp t ng ming ca

chut v kt qu cho thy kch thc khi u gim i r.

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2.4. Mt s loi vi khun lactic quan trng

Streptococcus lactic: vi khun ny pht trin tt trong sa v mt s

mi trng pha ch t sa, trong khi li pht trin km trong mi trng

nc tht pepton. y l loi vi khun hiu kh tu tin nn c th pht trinsu trong thch v cho khun lc hnh cy c nhnh. c im sinh ho quan

trng l ln men glucose, lactose, galactose, maltose, dextrin, khng ln men

saccharose. V vy Streptococcus lactic ng vai tr quan trng trong vic

ch bin sa chua. Pht trin tt nhit 30350C, nhit ny vi khun

gy ng t sa sau 1012 gi, acid gii hn do Streptococcus lactic to

nn thng dao ng trong khong 110-1200T, mc d c nhng chng yu

ch to khong 90-1000T . Sa c ln men chua bi Streptococcus lactic

lun lun c hng v c trng ca sn phm sa chua. nhit ti u

Streptococcus lactic pht trin trong sa c th t n s lng ti a l

1,22 t t bo/ml sau 1012 gi. Thi gian ny tng ng vi thi gian ln

men chua sa n 600T. acid sa tng ln rt nhanh trong vi gi u, sau

gim dn v ngng hn khi t n gn 1200T . ng biu th acid trong

sa ln men khng c hng i xung v sau khi t cc i chua cgi nguyn theo thi gian m khng gim i

Streptococcus cremoris: loi lin cu khun ny thng thy trong

sa di dng chui di hoc hin din di dng song cu khun, pht trin

tt 20250C. Cc iu kin nui cy khc vi ging S.lactic. Tuy nhin,

nh hng ca chng i vi sa hi khc, chng thng lm ng sa

nhng chng cng c th lm cho sa b nht. Mt s chng loi ny pht

trin trong sa cho mi c bit d chu c ng dng trong ch bin b.

Cng nh S.lactic, S. cremoris ln men lactose thnh acid lactic nhng khng

ln men saccharose, maltose, dextrin. Streptococcus cremoris lm cho sa c

chua thp hn (1101150T) to nn sn phm c v ngon thng c

dng trong sn xut b chua.

Streptococcus thermophillus v Streptococcus bovis y l hai vi

khun thuc nhm Viridams Streptococci chng khng pht trin 100

C,pht trin tt 40450C khi ln men sa to c khi ng, khng pht

22


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trin khi c s hin din ca 0,1% xanh methylen, 6,5%NaCl, pH=9,6,

arginin, pepton, khng to thnh amoniac. Streptococcus thermophillus l vi

sinh vt a nhit ging nh tn chng, nhit thch hp khong 40450C v

b tiu dit nhit 530C. Khi lm mi trng nui cy t sa thanh trngv 320C s lng ln khun lc ca Streptococcus thermophillus xut

hin. Streptococcus thermophillus l mt vi sinh vt quan trng trong sn

xut yaourt, phomat, n b ngn cn s hot ng bi 0,01 mg penicillin hay

5 mg streptomycin/ml. Streptococcus bovis ctm thy trong sa b v c

th xm nhp vo sa t ngun ny hay ngun khc, n sng st trong sa

thanh trng, c th tch chng t sa thanh trng hay mt s loi phomat

Cc trc khun lactic: trc khun lactic pht trin rng ri trong thin

nhin, chng lun lun c mt trong sa v cc sn phm sa chu c

acid cao, pht trin phm vi nhit rng trong mi trng c hoc khng

c khng kh. Trc khun lactic ng vai tr rt quan trng trong ch bin

sa chua, qu trnh lm fomat.

Trc khun lactic cng chia thnh nhm in hnh v nhm khng

in hnh tu thuc vo kh nng to thnh sn phm ph. Nhm trc khunlactic gm cc trc khun a nhit, trc khun xp chui cn nhit trung

bnh (a m),Bacterium thuc nhm trc khun khng in hnh.

Nh nhiu loi enzim thch hp nn cc vi khun lactic in hnh c

kh nng phn gii cc ng n (glucose, galactose, levulose...) thnh acid

lactic. Cc loi khc nhau c th tch t lng acid khc nhau:

Lactobacterium bulgaricum tch t n 3,5%, Thermobacter, Ribirium cerea

l 2,2%,Lactobacterium plantarum l 1%.Cc trc khun lactic a nhit pht trin tt mi trng acid yu

(pH=6,5), tuy nhin c loi pht trin pH=5,4 nh Lactobacillus

bulgaricus, cng c loi pht trin tt pH =3,8 trong khi cc trc khun xp

chui khng th pht trin c, nhit ti u l 40450C, y l vi khun

to c acid rt cao 3003500T.Lactobacterium helveticum (trc khun

phomat) pht trin 22-51

0

C, lm cho sa chua ti 2003000

T,Lactobacterium bulgarium pht trin 22530C to acid trong sa

23


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2003000T, gii hn l 2002500T. Lactobacterium lactic pht trin

22500C acid gii hn l 1101800T

Betabacterium trn mi trng thch to nhng khun lc ging nh

khun lc ca trc khun lactic u nhit. Khi pht trin trong sa vi khunny cho t acid, nu cho dch t phn ca nm men vo mi trng, vi khun

ny pht trin mnh hn ln, ng sa b ln men bi vi khun ny khng

ch to thnh acid lactic m cn to nhiu acid d bay hi. Trong sa thng

c hai loi chnh lBetabacterium causasium vBetabacterium breve.

Leuconostoc: l nhm gm nhng vi khun ln men lactic khng in

hnh. Chng c dng hnh cu nhng trong mi trng acid chng nhn hai

u v di ra sinh ra lng acid c hn v th khng lm ng sa. Tri li

chng hnh thnh t ng, acetyl metyl carbonyl hoc acetoin lm cho b

thm. Loi vi khun in hnh ca ging ny l Leuconostoc citrovorium

c ng dng trong sn xut b.

Bng 7: Gi tr nhit v pH ti u cho s sinh trng ca mt s

loi vi khun lacticLoi vi sinh vt Topt, (0C) pHopt

Lactococcus lactis

Lactococcus cremoris

Lactococcus diacetylactis

Streptococcus thermophilus

Lactobacillus bulgaricus

Lactobacillus helveticus

Lactobacillus casei

Lactobacillus kefir

Lactobacillus acidophilus

Lauconotoc lactis

Lauconotoc cremoris

Bifidobacterium bifidum

29 34

2832

3034

4042

4346

4346

3037

30

37

2027

2530

3741

6,06,5

6,06,5

6,06,5

6,06,5

5,56,0

5,56,0

-

-

5,56,0

5,56,0

-

-(L Vn Vit Mn, 2004)

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2.5. Dinh dng v nhng li ch v sc kho ca Kefir

Bn cnh nhng vi khun c li v nm men, Kefir cn cha nhiu

khong cht v nhng acid amin cn thit gip cha bnh v duy tr cc chc

nng cho c th. Cc protein hon chnh trong Kefir c tiu ho hon ton,v th c th hp thu mt cch d dng. Tryptophan l mt trong nhng acid

amin cn thit rt phong ph trong Kefir, c tc dng xoa du h thng thn

kinh. Kefir rt giu Ca v Mg, l nhng cht quan trng cho mt h thn kinh

kho mnh, nu dng Kefir thng xuyn s c tc dng tt cho h thn kinh.

Kefir cung cp mt lng ln phospho, y l khong cht cn thit

th hai trong c th con ngi, n gip s dng carbohydrat, cht bo,

protein gip t bo pht trin tt, duy tr v cn bng nng lng.

Kefir rt giu vitamin B12, B1 v vitamin K. y l mt ngun

Biotin tuyt vi gip c th hp thu nhng loi vitamin khc nh acid folic,

acid pantothenic v B12.

Nu dng Kefir mt cch thng xuyn s c nhiu li ch rt ln.

Mt s thng tin cho rng nh n m ngi ta tr c cc bnh ri lon

ng tiu ha, bnh au tht d dy, vim rut mn tnh v nhng bnh v

gan, mt, thn, bng quang. Kefir l mt mn n b dng. N cha nhiu

cht cn thit nh: ng sa, khong cht, vitamin, bo. V chua v men ca

Kefir gip d dng tiu ha nhng thc n khc. Hn na, Kefir cha mt

lng khng l nh khun i khng vi nhng vi trng gy bnh r

rng cu to.

2.6. Phng php ch bin v bo qun ging Kefir

Hin nay c rt nhiu thng tin khc nhau cho vic chm sc v boqun ging kefir. Cch n gin nht l lm kh chng bng khng kh ri

gi trong giy v gi ni kh mt, nhng ht ny vn c th hot ng tt sau

mt hay nhiu nm. Sau ngm chng vo nc, lc sch v th vo mt

tch sa yn trong vi ngy, chng s hot ng tr li.

Hu ht cc phng php u ngh nn ra ging trc khi s

dng, nhng mt s khc li khng cho php, h cho rng h vi sinh vt c

li xung quanh con ging s b xo trn hoc b tiu it hon ton trong

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nc c chlorine hay flourine v ng ra ging ngoi tr mc ch lm kh

hay mun ngng ln men trong thi gian ngn. Ging Kefir do dai hn mi

ngi ngh, c th t chng trong sa ti v tr trong t lnh 40C khi bn

khng mun n ln men. Tt nht nn thay sa mi tun gi ging v nuichng lun hot ng.

Ngoi ra, c mt cch tr ging khc l t n trong t ng mt

thi gian di m khng c vn g n vic ti kch hot ging.

Kefir s c cht lng tt trong khong 14 ngy nu tr 40C. Theo

phng php ch bin hin nay ngi ta c th thm cng on chn bng

cch sau khi cho ln men nhit phng, lm lnh xung 14160C

khong 12 n 14 gi. Lc ny tc trao i cht ca vi khun v nm men

b chm li. Khi sn phm t n chua yu cu, a vo bo qun lnh

di 60C v s dng 12 tun.

Hnh 5 Ht Kefir v bo qun ht Kefir

2.7. Qui trnh ch bin

2.7.1. Quy trnh sn xut men ging Kefir

Sa ti tit trng

Ht Kefir (5%) Cy men

Ln men (pH = 4,5)

Ht Kefir Lc thMen ging Kefir

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2.7.2. Gii thch qui trnh sn xut men ging

- Mi trng chun b ging: Sa ti, sa gy hoc sa hon

nguyn. Hm lng cht kh trong mi trng khong 1112%. Sa c

thanh trng 90950C trong thi gian 3045 pht (thi gian thanh trng ko

di nhm v hot enzim v c ch n mc ti thiu s c mt ca vi sinh vt

l trong mi trng gip cho ging pht trin tt v khng b tp nhim),

sau a v 22240C chun b cy ging. y s dng sa ti tit

trng ca Vinamilk .

- Cy ging : s dng ht Kefir vi lng ban u 5% theo khi lng,

qu trnh nhn ging cng c thc hin nhit phng (23250C) . Do

ht Kefir c kch thc ln nn chng thng b chm xung di y nn

cn phi khuy trn mi trng trong thi gian 1015 pht sau mi 25 gi .

Qu trnh nhn ging kt thc khi pH mi trng gim xung cn 4,5.

- Lc: khi t pH yu cu, canh trng c lc. Ht kefir c x l

bng cch ra trong nc v khun nhit thp (6100C) loi b tp

cht bm trn b mt ht (c th s dng sa gy v trng ra ht, HtKefir qua ra sch v bo qun trong nc v khun hoc dung dch mui

NaCl 0,9%. Khi cn nhn ging cho m tip theo, s dng tip ht Kefir trn

nhn ging

- Dch thu c sau qu trnh lc th cha cc vi khun lactic v

nm men c th s dng cy ging vo mi trng sa nguyn liu sn

xut Kefir. Qu trnh sn xut ging cng c thc hin 2530 0C thi

gian nui trung bnh l 20 gi (cn kim tra gi tr pH ca canh trng l 4,5

xc nh thi im kt thc qu trnh nui).

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2.7.3.Qui trnh ch bin KefirSa ti

Phi ch

Men ging Kefir Cy ging

Ln men

Phi ch (iu v)

V bao b

Bo qun (46oC)

2.7.4. Gii thch qui trnh sn xut Kefir

- Nguyn liu: Sa c cht lng cao, khng cha khng sinh v tcc mc ch tiu v vi sinh. Hm lng cht bo c th thay i tu th hiu

ngi tiu dng, sn phm Kefir thng c hm lng cht bo t 2,53,5%.

Trong cc th nghim ny, s dng nguyn liu l sa ti tit trng ca

Vinamilk.

- Phi ch: sa nguyn liu c b sung thm ng lactose v dch

du nhm to iu kin ti u cho vi khun lactic pht trin v to hng v

a dng cho sn phm- Cy ging: Ging Kefir c chun b theo qui trnh sn xut men

ging (mc 2.7.1)

- Ln men: trong qu trnh ln men Kefir, vi khun lactic s chuyn

ng lactose thnh acid lactic, mt s loi nm men s dng ng lactose

s chuyn ho lactose thnh ethanol v kh CO2. Trong dch ln men cha

hng trm sn phm ph t hai qu trnh ln men lactic v ethanol ni trn.

Chng ng vai tr quan trng trong vic hnh thnh nn hng v ca sn

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phm, ng ch nht l cc acid hu c nh acid propiomic, acid formic,

acid succinic, cc hp cht bay hi thuc nhm aldehyde (aldehyde acetic,

diacetyl) v ru cao phn t, nhit ln men 25300C

- iu v: Sn phm sau ln men s c nht tng i cao nn cnb sung thm nc v ng saccharose sn phm t cu trc v hng

v mong mun

- V bao b: Thc hin trong iu kin v trng hn ch cc vi

sinh vt t mi trng xung quanh nhim vo sn phm

- Bo qun: sn phm hon thnh c bo qun 46 0C. Trong qu

trnh bo qun h vi sinh vt Kefir vn tip tc trao i cht vi mi trng

v lm bin i dn cc ch tiu ho l ( chua, hm lng ethanol) v ch

tiu cm quan (mi v...) ca sn phm.

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Chng 3 PHNG TIN V PHNG PHP NGHIN CU

3.1.Phng tin

3.1.1. a im nghin cu

Qu trnh tin hnh th nghim, thu thp v x l s liu ti phng th

nghim B mn Cng Ngh Thc Phm, Khoa Nng Nghip-Ti Nguyn

Thin Nhin, Trng i Hc An Giang.

3.1.2. Thi gian nghin cu

Thi gian thc hin th nghim t thng 3/2005 n thng 5/2005.

3.1.3. Nguyn liu

- Sa ti titt trng ca Vinamilk

- Ging Kefir

- Du Ty

- ng Lactose

- ng RE

3.1.4. Dng c v thit b

- T cy, t - Cn phn tch, cn in t

- Thit b chng ct

- T lnh

- T sy

- Mt s dng c thng thng phng th nghim

3.1.5. Ha cht

- Ha cht chun acid: NaOH 0,1N

- Ha cht xc nh lng cn: HNO3 m c, KI 10%, K2Cr2 O7 ,

Na2S2O3 0,1N

- Mi trng nui vi sinh vt: Fluid lactose Medium (vi khun)

Potato dextrose agar (nm men)

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3.2. Ni dung b tr th nghim

3.2.1 Th nghim 1: Kho st nh hng ca thnh phn nguyn liu n

qu trnh ln men v cht lng sn phm

3.2.1.1. Mc ch: Tm cng thc phi ch nguyn liu thch hp qutrnh ln men t hiu qu cao v sn phm c cht lng tt.

3.2.1.2. S b tr th nghim

Sa ti tit trng

Phi ch

L1 L2 L3

F1 F2 F3 F1 F2 F3 F1 F2 F3

Men ging Kefir Cy ging (4%)

Ln men (28-35 0C, 950T)

Phi ch

Rt chai, ng np

Bo qun (46oC)

Th nghim tin hnh hon ton ngu nhin trn hai nhn t L v F vihai ln lp li . L l t l ng Lactose b sung; F l t l dch du b sung

L1: 0% F1: 0%

L2: 5% F2: 10%

L3: 10% F3: 20%

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3.2.1.3. Chun b th nghim

Nguyn liu th nghim l sa ti tit trng khng ng ca

Vinamilk vi cc thnh phn n nh: lactose: 4,6g, bo 3,5g, m 3,3g/100

ml saDu ty ra sch, p ly nc, chnh v kh v pH c nh (

Brix =5%, pH=4.0) thanh trng 800C (5 pht)

Cn hm lng ng Lactose b sung theo t l trn. Men ging

Kefir c chun b theo quy trnh:

Sa ti tit trng

Tr trong nc v trng Cy ging (5%)

Ln men (pH = 4,5)

Lc

Ht kefir Men ging Kefir ( dng cho th nghim)

Men ging c xc nh tng lng vi khun, nm men bng cchm s khun lc mc trn mi trng dinh dng thch hp

3.2.1.4. Tin hnh th nghim

Sa ti chia lm 9 mu ( mi mu 100ml), tin hnh phi ch

ng lactose v dch du vi t l trn. Cy men ging t l 4% (v/v) v ln

men nhit phng, acid dng l 950T. Sau tin hnh phi ch vi

dch siro (nng 25%) vi t l 30% . S dng loi ng RE.

3.2.1.5. Cc ch tiu xc nh acid theo thi gian

cn

Mt s vi khun v nm men

nh gi cm quan theo theo thang im m t (bng 8).

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Bng 8: Bng im nh gi cm quan sn phm Kefir

im M tMi

5 Sn phm c mi thm c trng ca sa chua, mi thm

du ca du Ty ha hp vi mi ca ru etylic, d chu.

4 Sn phm c mi thm nh ca sa chua, mi thm du ca

du Ty v thong mi ru etylic, nhng t c trng hn.3 Mi thm ca sa chua v du Ty khng th hin r, mi

ru qu nh hoc qu nng, km hi ha.2 Sn phm c mi km, khng cn mi thm t nhin ca

sa chua, khng c mi du hoc mi du b bin i,

mi acid acetic qu mnh.1 Sn phm c mi l, khng th nhn bit c mi ca sa

v du0 Sn phm c mi ca qu thi, mi ca sa h hng, kh

ngiV

5 Sn phm hi ha gia v ngt v v chua du ca acid

lactic, v nng nh ca cn v CO2 kh hp dn.4 Sn phm c v chua ngt hi ha nhng cn hi cao

hoc hi thp, tng i hp dn.3 V chua ngt ca sn phm km hi ha, hi chua hoc hi

ngt, cn qu nhiu hoc qu t, khng hp dn lm.2 Sn phm qu chua hoc khng chua, v ngt km, khng ha

hp, khng pht hin cn hoc cn qu mnh, hi ng.1 Sn phm c v l, nht nho.0 V rt kh chp nhn, ng cht, biu hin ca h hng.

Hnh thi

5 Sn phm ng nht, khng phn lp, nht va phi

4 Sn phm tng i ng nht, t ln cn

3 Sn phm c du hiu tch nc, hoc nht hi cao.

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2 Sn phm b phn lp (lp nc bn trn, dch sa bn di

ng nht) hoc nht qu cao.

1 Sn phm b phn 2 lp r rt, dch sa bn di khng

ng nht, (c ln cn ln)

0 Sn phm b phn lm nhiu lp

3.2.2. Th nghim 2: Kho st nh hng ca t l men ging n qu

trnh ln men v cht lng sn phm

3.2.2.1 Mc ch: Xc nh t l men ging thch hp qu trnh ln men

t hiu qu cao v sn phm t cht lng tt

3.2.2.2 . S b tr th nghim

Sa ti

Phi ch (L:5%, F:10%)

Men ging Kefir Cy men

K1 K2 K3 K4

Ln men (950T)

Phi ch

Rt chai ng np

Bo qun (46oC)

Th nghim kho st nh hng ca nhn t K vi hai ln lp li. K

l t l men ging Kefir (%)

K1:2%

K2: 4%

K3: 6%

K4:8%

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3.2.2.3. Chun b th nghim:

Qu trnh chun b men ging, nc p du, ng lactose ging th

nghim 1

2.2.2.4. Tin hnh th nghimTh nghim tin hnh vi thnh phn nguyn liu b sung gm

lactose 5%, nc p du: 10%. Ln men n acid dng 950T nhit

phng. Cy men ging theo t l kho st.

2.2.2.5. Ch tiu xc nh

acid theo thi gian

cn

Vi khun, nm men

nh gi cm quan theo bng 8.

2.2.3. Th nghim 3: Kho st nh hng ca acid dng n thi gian

ln men v cht lng sn phm

3.2.3.1. Mc ch: Tm acid dng thch hp cho thi gian ln men tt v

sn phm t cht lng cao.

3.2.3.2 . S b tr th nghim

Sa ti

Phi ch (L:5%, F:10%)

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Ln men

A1 A2 A3 A4

Phi ch

Rt chai ng np

Bo qun (46oC)

Th nghim b tr hai ln lp li vi nhn t A l acid dng ca

sn phm

A1: 850T

A2: 950T

A3: 1050T

A4: 1150T


cc bc chun b nh th nghim 1


Sa ti chia lm 4 mu v phi ch vi t l lactose 5%, dch du

10%. Sau cy men ging Kefir vi t l 6% (v/v)v tin hnh ln men

nhit phng, theo di s bin i acid theo thi gian v cho kt thc lnmen 4 acid dng nh trn, thnh phm c phi ch v bo qun lnh

46oC.

3.2.3.5. Ch tiu nh gi

Thi gian ln men

cn

Mt s nm men v vi khun

nh gi cm quan theo bng8.

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3.2.4. Th nghim 4: Kho st t l phi ch thch hp cho thnh phm

3.2.4.1. Mc ch: Tm cng thc phi ch thch hp nng cao tnh

thng mi v cht lng sn phm.

3.2.4.2. S b tr th nghimSa ti

Lactose 5% Phi ch Dch du 10%


Ln men (1050T)

Phi ch

W1 W2 W3

S1 S2 S3 S1 S2 S3 S1 S2 S3

V bao b

Bo qun (46oC)

Th nghim b tr 2 ln lp li trn 2 nhn t W v S. Vi W l t l siro phi

ch; S l nng dch Siro

W1: 20% S1: 20%W2: 30% S2: 25%

W3: 40% S3: 30 %


Cc bc chun b nh th nghim trn, chun b dch siro vi cc

nng xc nh bng cch cho ng RE vo nc vi cc t l 20%, 25%,

30%, un nh ha tan ht ng v thanh trng dch siro.


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Sa ti chia lm 9 mu phi ch 5% ng lactose, 10% dch qu,

cy ging vi t l 6% v cho ln men n acid dng 1050T. Kt thc ln

men, sn phm c phi ch vi dch siro theo t l kho st

2.2.4.5. Ch tiu xc nhSn phm c nh gi cht lng bng phng php cm quan

theo thang im m t (bng 8)

3.2.5. Th nghim 5: Kho st kh nng bo qun thnh phm

3.2.5.1. Mc ch: Theo di v chn thi gian bo qun thch hp cho thnh

phm.

3.2.5.2. Tin hnh th nghim:

Sn phm c bo qun trong chai nha ng np kn nhit

4-60C, theo di s thay i cc ch tiu acid, cn v cht lng sn

phm theo thi gian xc nh thi gian bo qun thch hp.

3.3. Phng php phn tch v x l s liu

3.3.1. Phng php phn tch

- acid: Phng php xc nh chua ca sn phm (ph chng 1)

- cn: Phng php xc nh cn ( ph chng 1)

- Vi sinh vt: Phng php xc nh hm lng vi sinh vt(ph chng

1)

3.3.2. x l s liu

S liu c x l thng k bng chng trnh Statgraphic 3.0 v

Minitab

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Hnh 6 Nguyn liu dng cho ch bin sa Kefir

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Chng 4 KT QU V THO LUN

4.1. nh hng ca thnh phn nguyn liu n qu trnh ln men v

cht lng sn phm.

kho st nh hng ca thnh phn nguyn liu n kh nng ln

men v cht lng sn phm, th nghim tin hnh kho st hm lng

ng lactose v dch du b sung theo cc t l: Lactose 0%, 5%, 10%, Dch

du: 0%,10%, 20%. Vi t l men ging c nh 4% (theo th tch). Kt qu

xc nh vi sinh vt trong men ging gm: vi khun: 3,18*1014 (cfu)/ml, nm

men: 9,60*1011 (cfu)/ml. Hm lng lactose c sn trong nguyn liu l

4,6g/100ml, dch du c pH = 4,0, Brix = 5; acid dng l 950T. Kt qu

thng k cn, vi khun, nm men v thi gian ln men c cho trong

bng 9

Bng 9: nh hng ca hm lng ng lactose v nc p du n

thi gian ln men, cn v mt s vi sinh vt

Thnhphn

Hm lng(%)

Thi gian(gi)

cn(g/l)

Vi khun(A.1014 cfu/ml)

Nm men(A.1014 cfu/ml)

Lactose

(L)

0

5

10

17,00

16,50

14,50

0,39a

0,45a

0,46a

2,2a

2,5a

3,7b

7,4a

8,5b

9,3c

Dch

du

(F)

0

10

20

17,00

16,00

15,50

0,21a

0,32b

0,77c

2,3a

2,9b

3,1b

7,8a

8,3b

9,1c

Lactose F = 1,20 F = 488,93 F = 211,00

P = 0,33 P=0,00 P = 0,00

Dch du F = 64,57 F=122,07 F = 96,75

P = 0,00 P=0.00 P = 0,00

(Cc ch s c cng k hiu khng c s khc bit mc ngha 95%)

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Hnh 7: th biu din s tng quan gia acid theo hm lngng lactose v dch du

Theo bng 9 v hnh 7 cho thy, hm lng ng lactose v t l

dch du nh hng n acid ca mi trng ln men, hm lng ca cc

thnh phn ny cng tng th cng c nhiu c cht cho vi sinh vt s dng.

Khi b sung lactose, tc l b sung c cht chnh cho nhm vi khun

lactic hot ng nn trong cng thi gian ln men hm lng lactose cao,lng acid sn sinh vo mi trng cng nhiu do vi khun lactic hot ng

mnh m. Ngoi ra, khi dch qu c b sung s lm gim pH mi trng

(pH= 5,56), to pH ban u ti u cho s pht trin ca nhm vi khun

lactic, gip vi khun thch nghi v pht trin tt hn. Khi vi khun bt u

pht trin tt s cung cp acid cho mi trng n 110-120oT hoc cao

hn .

Khi hm lng lactose b sung thp (


55/81

-0.0019*x^2+0.0017*y^2-0.00023*x*y+0.0148*x-0.00384*y+0.21

0 2 4 6 8 10Lactose (%)

04

812

1620

Dich qua (%)

0

0,2

0,4

0,6

0,8

1

Alcohol(g/l)

Hnh 8 th biu din s tng quan gia cn theo hm lng

ng lactose v dch du

Qua hnh 8 nhn thy, t l dch du b sung c nh hng ln n

cn ca sn phm, tuy nhin hm lng lactose li khng nh hng

nhiu, khi b sung ng lactose, lng cn sinh ra c thay i nhng khng

c ngha v mt thng k. Trong khi , dch du li c tc ng r nt, do

trong men ging kefir c cha tng i mt lng ln t bo nm men

(chim 5-10% tng s vi sinh vt trong ht kefir), trong ch c mt s t s

dng c ng lactose, cn c cht chnh cho hu ht t bo nm men l

fructose, glucose. Do vy, fructose trong dch qu l nguyn nhn chnh lm

cho lng cn trong sn phm tng vt, ng thi sinh CO2 v mt s cht

sinh hng to mi cho sn phm .Theo bng 9 v hnh 9, mt s nm men b nh hng nhiu bi c

hai nhn t ng lactose v dch du, qua cc nghin cu v h vi sinh vt,

trong men kefir c cha nhiu loi nm men, trong c mt s loi s dng

c ng lactose, do ng lactose cng l nguyn nhn nh hng n

sinh khi ca nm men.

42


56/81

-0.04*x^2+0.015*y^2+2.33*x+0.35*y+68.33

0 2 4 6 8 10Lactose (%)

04

812

1620

Dich qua (%)

68

78

88

98

108

Namm

en(*10^10)

Hnh 9 th biu din s tng quan gia mt s nm men theo

ng lactose v dch du

Nh vy, khi hm lng ng lactose v dch du cng cao, cng

c nhiu c cht cho nm men s dng, hot ng v pht trin, lm cho mt

s nm men tng cao v sinh ra mt lng cn tng i v CO2 to cho sn

phm c v nng v mi thm mnh m.

187,278 + 1,89333*x^2 - 0,181667*y^2 - 6,1*x + 6,46667*y + 0,19*x*y

0 2 4 6 8 10Lactose (%)

04

812

1620

Dich qua (%)180

220

260

300

340

380

420

Vikhuan(*10^12C

FU/ml)

Hnh 10 S tng quan gia mt s vi khun theo hm lng lactose v

dch du

43


57/81

Hnh 10 cho thy s nh hng mnh m ca dch du v ng

lactose n mt s vi khun. Trong men Kefir, nhm vi khun lactic chim

u th, chng s dng c cht chnh l ng lactose, glucose v galactose

nn khi lng lactose cng cao th mt s vi khun cng cao v tc phttrin cng nhanh hn.

Vi dch du cng vy, khi fructose b phn ct thnh cc glucose s

cung cp thm c cht cho vi khun hot ng v pht trin, do vy mt s

ca chng cng tng nhanh khi hm lng dch du tng.

Bng 10a: Kt qu nh gi cm quan mi v sn phm

(tng nhn t)Thnh phn Hm lng (%) Mi V

Lactose

0

5

10

3,40b

4,03a

3,70ab

3,36b

4,03a

3,70a

Dch qu

0

10

20

3,33b

4,03a

3,76

a

3,83a

3,70a

3,57

a

Lactose F =6,81 F = 10,42

P =0,00 P =0,00

Dch du F = 8,47 F = 1,67

P = 0,00 P = 0,19

Theo kt qu bng 10a, hm lng lactose b sung c nh hng n

v ca sn phm, mi v gia mu c b sung lactose v khng b sung

lactose c s khc bit ngha, nhng gia mu b sung 5% v 10% latose

th mi v li khng khc bit, da vo s im trung bnh v yu t kinh t,

mu b sung 5% lactose c xem l hiu qu nht.

Nng dch du b sung li khng nh hng nhiu n v, v sn

phm khng c s khc bit ngha nhng s khc bit v mi gia mu c

v khng c b sung dch du li rt r do dch du c mi thm kh mnh v

li l c cht chnh cho nm men s dng, pht trin v sinh hng cho sn

phm. Tuy nhin, gia mu b sung 10% v 20% dch du th s khc bit v

44


58/81

mi li khng c ngha thng k nn chn mu b sung 10% dch du l ti

u hn

Bng 10b: Kt qu nh gi cm quan mi v sn phm

(tng tc 2 nhn t)

Lactose Dch du Mi V0

0

0

0

10

20

3.20ab

3.60ab

3.40ab

3.70ab

3.00b

3.40ab

5

5

5

0

10

20

3.60ab

4.50a

4.00ab

4.00a

4.30a

3.80ab10

10

10

0

10

20

3.20b

4.00ab

3.90ab

3.80ab

3.80ab

3.50ab

F=0,67 F=2,55P=0,617 P=0,04

Nh vy, kt hp kt qu nh gi cm quan t bng 10a v 10b,

hm lng ng lactose 5% v dch du 10% c chn b sung vo

nguyn liu.

4.2. nh hng ca t l men ging n thi gian ln men v cht lng

sn phm

kho st nh hng ca t l men ging n cht lng sn

phm, th nghim c b tr 4 t l men: 2%, 4%, 6%, 8%. Sa ti

nguyn liu c b sung 5% ng lactose v 10% dch qu v c cy

men ging vi 4 t l kho st. Acid dng l 950

T. Cc ch tiu xc nh ccho trong bng 11

Bng 11: nh hng ca t l men n cn, nm men, vi khun v

thi gian ln men

45


59/81

T l men

ging (%)

cn

(g/l)

Thi gian

(gi)

Nm men

(A.1011 cfu/ml)

Vi khun

(A.1014 cfu/ml)2

4

6

8

0,05c

0,20b

0,34a

0,66a

20,00

17,50

14,00

13,00

5,2

6,6

7,2

8,1

2,1

2,8

3,5

4,2

F = 337,54

P = 0,00

Theo hnh 11 cho thy, khi lng men ging cy vo cng nhiu,

lng acid v lng cn cng tng. Tuy nhin, khi t l men cao (>6%) th tc tng acid chm hn, do khi mt s vi sinh vt cao xy ra hin tng cnh

tranh sinh hc lm cho qu trnh pht trin ca vi sinh vt khng c thun

li. V th, tc sinh acid b chm li.

Tc sinh cn chm hn khi b sung t l men trn 8% v khi

lng men cao th mt s vi khun cao, trong c s hin din ca nhm vi

khun acetic nn c s chuyn ha cn thnh acid acetic lm cho sn phm

c v chua gt v mi khng hp dn.

i vi sn phm Kefir i hi lng cn khng qu cao cng khng

qu thp, v chua du v mi hng mnh m, v vy t l men ging nn

chn sao cho ha hp c cc ch tiu ny.

46


60/81

Hnh 11: S tng quan gia acid v cn theo t l men ging

24,0861 - 0,0845823*y^2 -0,449219*x^2 + 3,69854*y + 3,90608*x + 0,359325*y*x

0 2 4 6 8 10Ty le men (%)

04

812 16

20

Thoi gian len men (gio)

0

30

60

90

120

150

Acid(o

T)

Hnh 12: S tng quan gia acid v thi gian ln men theo t lmen ging

47

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

2 4 6 8 10

Ti le men giong (%)

ocon(g/l)

0

20

40

60

80

100

120

oacid(doT)

o con (g/l)

o acid (do T)


61/81


62/81

Hnh 13 th hin mt s nm men v vi khun tng mt cch u n

theo mc tng ca t l ging, ngha l khi t 95 0T, lng c cht trong

mi trng vn cn cung cp cho nm men v vi khun hot ng nn cha

thy c s suy gim mt s, do vy cn c mt ch bo qun thch hp saukhi kt thc qu trnh ln men c ch s pht trin ca chng.

Qua cc hnh 11, 12, 13 cho thy, tc sn sinh cc cht vo mi

trng khng u n nh mc tng ca mt s vi sinh vt. V ln men l

mt qu trnh phc tp, ch mt thay i nh trong iu kin mi trng nh

pH, nhit , t l men ging.th qu trnh sn sinh sn phm vo mi

trng din ra theo nhiu chiu hng khc nhau, c khi chng s dng c

cht ch tng sinh khi m khng sinh sn phm vo mi trng, nht l

khi ln men trong iu kin hiu kh.

4.3. nh hng ca acid dng n thi gian ln men v cht lng

sn phm.

kho st nh hng ca acid dng, th nghim c b tr cho qu

trnh ln men kt thc 4 acid dng khc nhau: 850T, 950T, 1050T, 1150T.

Sa nguyn liu c phi ch vi 5% ng lactose v 10% dch qu, t l

men ging s dng c nh 6% theo th tch.

Hnh 14: S tng quan gia thi gian ln men v cn theo acid dng

49

0

5

10

15

20

85 95 105 115 125

Do acid dung (do T)

Thoigianlenmen(gio)

0

0.1

0.2

0.30.4

0.5

0.6

Docon(g/l) Thoi gian (gio)

Do con (g/l)


63/81

Hnh 14 cho thy, acid tng mt cch tng i u n theo thi

gian, cch khong 2 gi th acid tng thm 100T. Tuy nhin, khi t n

acid cao (>1100T), tc tng acid chm dn v thi gian ko di hn. Do

acid tng cao lm cho pH mi trng xung, c ch tr li s hot ng cavi khun lm cho qu trnh sinh acid chm dn, nu qu trnh ln men vn

tip tc th n mt lc no acid ca mi trng s c ch ton b s pht

trin ca vi sinh vt.

Hnh 14 cng th hin mc tng ca hm lng cn theo acid

dng, acid dng t 95-1150T, tc sinh cn nhanh hn do gii hn

acid ny s to pH mi trng thun li cho s pht trin ca nm men nn

chng sinh cn rt nhanh. Nhng khi t n acid >1150T th qu trnh

sinh cn b gim hn li. iu ny c th do mt s vi khun tng cao nn c

hin tng cnh tranh sinh hc gy nh hng n s pht trin ca nm

men. Ngoi ra, c th do lng c cht trong mi trng gim nn qu trnh

ln men sinh cn chm li. Bn cnh , c s chuyn ha ca cn thnh acid

acetic do s hin din ca nhm vi khun acetic, v vy qu trnh ln men vn

tip tc xy ra n acid cao, sinh nhiu acid acetic gy v chua gt cho sn

phm. ng thi, khi mt s nm men cao lm cho sn phm c v hi ng

ca xc men.

Hn na, khi acid cao, cc mixen cng c khuynh hng kt hp

cc khi ng li vi nhau, dch nc - whey - ng d b tch ra, lc bn

gel ca sn phm gim, rt d lm cho sn phm b phn lp. Tuy Kefir l sn

phm c nht kh cao nhng t tnh thng mi v to mi v thch

hp th cn c thm cng on phi ch vi dch siro sau khi qu trnh lnmen kt thc. Do vy, vic chn la acid dng thch hp va m bo

cho hnh thi sn phm c n nh trong qu rnh bo qun, va to cho

sn phm c v chua ngt hi ha l iu rt quan trng.

Qua kt qu kho st v nh gi cm quan cho cc ch tiu, acid

dng 1050T c chn kt thc qu trnh ln men v mi v hnh thi gia

cc mu khng c s khc bit nhng v ca mu c acid 105 0T li c

khc bit r v c nh gi tt hn.

50


64/81

Bng 13: Kt qu cm quan mi v v hnh thi sn phm

acid dng (0T) Mi V Hnh thi

85

95

105

115

3.10a

3.30a

3.80a

3.10a

3,00b

3,00b

4,00a

3,30ab

3.80a

3.30a

3.80a

3.30a

F= 2,25 F=3,99 F=2,63P=0,10 P= 0,01 P=0,65

4.4. nh hng ca t l phi ch sau ln men n hnh thi v cht

lng sn phm

tin hnh kho st t l phi ch, sau khi kt thc qu trnh ln

men acid dng 1050T, th nghim tin hnh phi ch vi dch siro theo

cc nng v t l khc nhau. Nng siro c kho st 3 mc 20%,

25%, 30% v t l phi ch vo dch sa sau ln men l 20%, 30%, 40%. Kt

qu chn la da vo nh gi cm quan .

Bng 14a: Kt qu cm quan mi, v v hnh thi sn phm(Tng nhn t)

Nhn t Hm lng Mi V Hnh thi

Nng siro

(S)

20

25

30

3,77a

3,93a

4,13a

3,07b

3,70a

3,97a

3,67a

3,58a

4,03a

T l phi ch

(W)

2030

40

3,87a

3,97a

4,00a

3,20b

3,93a

3,40b

3,57a

4,03ab

3,67b

S F=2,35 F=12,60 F=3,04P=0,10 P= 0,00 P=0,05

W F= 2,35 F=7,03 F=3,04P=0,10 P= 0,00 P= 0,05

Qua bng 14, mi gia cc mu khng c s khc bit nhng nng

dch siro c nh hng n v ca sn phm, v gia nng siro 25% v

51


65/81

30% khng c khc bit, do vy nn chn nng siro 25% c kinh t

hn. nng ny sn phm vn t c s hi ha v v chua ngt. Vi

nng siro nh trn th t l phi vo sn phm l 30% s thch hp nht, v

khi phi vi t l 20% nht sn phm cn kh cao, khng ph hp lm chosn phm dng ung v t c a chung hn. Khi phi vi t l 40% c th

mang li hiu qu kinh t nhng sn phm li long, d b phn lp, gy kh

khn cho qu trnh bo qun. ng thi, t l phi ch 30% v ca sn phm

cng c khc bit ngha

Bng 14b: Kt qu cm quan mi, v v hnh thi sn phm(Tng tc 2 nhn t)

Nng siro T l phi ch Mi V Hnh thi20

20

20

20

30

40

3,5ab

3,7a

4,1a

2,5b

2,9b

3,8a

3,7a

3,4ab

3,9a

25

25

25

20

30

40

3,8a

4,4a

4,2a

3,3ab

4,4a

4,2a

3,1b

4,4a

3,2b

3030

30

2030

40

3,8a

4,3a

4,7a

3,6ab

3,8a

3,7a

3,9a

4,3a

3,9a

F=3,2 F=4,5 F=3,68

P=0,01 P=0,00 P=0,00

4.5. nh hng ca thi gian bo qun n cht lng sn phm

Thnh phm sau khi phi ch s c acid l 750

T, cn l14,75g/l c a vo bo qun 46oC v tin hnh o cc ch tiu cht

lng theo thi gian

Bng 15: Ch tiu ha l, vi sinh ca sn phm theo thi gian bo qun

52


66/81

F= 17,80 F=22,36

P=0,00 P= 0,00

Qua bng 15 cho thy, khi bo qun sn phm 46oC, thi gian

cc ch tiu cht lng vn cn duy tr c l trc 15 ngy, tuy nhit

lnh nhng vi sinh vt vn hot ng nhng vi tc chm hn nn cc ch

tiu ha l ca sn phm vn tip tc thay i. Mc d sau 20 ngy sn phm

vn cha c du hiu h hng nhng acid, cn c s thay i

ngha. Vy m bo c cht lng nn gi sn phm 46oC v s

dng trc 15 ngy. Qua kim tra vi sinh, sau 20 ngy trong sn phm

khng tn ti vi sinh vt gy bnh

Thi gian (ngy) acid ( T) cn

(g/l)*10-2Salmonell

a(cfu/ml)

E.coli

(cfu/ml)0

510

15

20

75a

75a

76a

77ab

80b

14,75a

14,75a

14,85a

15,10ab

15,40b

0

00

0

0

0

00

0

0

53


67/81

Hnh 15: Sn phm Kefir

54


68/81

Chng 5 KT LUN V NGH

5.1. Kt lun

Qua qu trnh tin hnh th nghim, thu thp s liu v tng hp cc

kt qu thu nhn c, c th rt ra cc kt lun nh sau:

- qu trnh ln men tt v sn phm t cht lng cao th t l b

sung ti u nht cho nguyn liu l: ng lactose 5% v dch qu 10%.

- T l men ging tt nht cho qu trnh ln men l 6%.- acid dng thch hp nht cho sn phm t mi v v hnh thi

tt l 1050T.

-T l phi ch cho thnh phm sau ln men c nh gi cao

nng siro 25% vi t l phi vo dch ln men l 30%.

- Thi gian bo qun thch hp nht sn phm vn gi c cht

lng n nh l 15 ngy 46oC.

Quitrnh kt lun:

Sa ti

Phi ch (lactose 5%, Dch du 10%)


Ln men (1050T)

Phi ch (siro nng 25%, t l 30%)

V bao b

Bo qun (46oC)

55


69/81

5.2. ngh

Kefir l sn phm tuy c t rt lu i nhng trn th trng Vit

Nam th vn cn rt mi l. Hn na do qu trnh pht trin v h vi sinh vt

trong Kefir cn rt phc tp nn phng php ch bin Kefir trn qui mcng nghip cn nhiu kh khn, tnh thng mi khng cao v cht lng

sn phm kh c th trng chp nhn. iu ny l mt hn ch ln trong

cng nghip ch bin sa v Kefir ngoi vic s dng nh mt loi sa chua

thng thng, n cn c quan tm nh mt lai dc phm cha bnh v

rt c li cho sc khe, Kefir cha y v qun bnh cc t cht cn thit

cho c th, n thch hp cho mi la tui, c bit l tr em, ngi bnh v

ngi gi. C rt nhiu thng tin v dc tnh ca Kefir m n nay ngi ta

vn cn xem l iu b mt

Do thi gian nghin cu ngn, thit b v phng tin th nghim cn

nhiu hn ch nn ni dung th nghim khng th kho st ht cc yu t c

lin quan n cht lng v tnh thng mi cho sn phm Kefir. V vy

gp phn nng cao gi tr v a dng ha cho sn phm, to iu kin cho

Kefir ngy cng quen thuc v gn gi vi ngi tiu dng Vit Nam, sn

phm cn c nghin cu tip nhng vn sau:

- Kho st thi gian v nhit chn sn phm sau ln men kefir

c hng v mnh m v hp dn hn.

- Kho st phi ch dch qu vi cc loi qu khc, hoc b sung

cafe, cacao a dng ha sn phm.

- Nghin cu s pht trin ca ht Kefir trn cc mi trng mi nh

nc da, sa u nnh, sa da, dch qu nguyn cht.- Nghin cu bin php ko di thi gian bo qun sn phm

- Nghin cu phng php sn xut Kefir trn qui m cng nghip

hin i v kh nng pht trin sn phm.

56


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TI LIU THAM KHO

1. ANNONYMOUS. 2005. About Kefi (http://www.heliosnutrition.com)

2. Bi Th Nh Thun, Nguyn Phng Tin, Bi Minh c.1991. Kim TraCht Lng v Thanh Tra V Sinh An TonThc Phm. H Ni: NXB Y

Hc.

3. Dom s Kefir in-site (http://user.chairot.com.au/~dna/Kefirpage.html).

4. Dng Th Phng Lin.1999. K thut ch bin sa v cc sn phm

sa( bi ging).Cn Th: HCT

5. Early, R.1992. The Technology of Dairy Products. Newyork: VCH

Publishers, INC.

6. Hunh c Hiu. 1970. Food Chemistry. Modern Asia Editions.

7. L Ngc T, Bi c Hi, Dun. 2001. Ho hc Thc Phm. H Ni:

NXB Khoa Hc K Thut H Ni.

8. Lm Xun Thanh. 2003. Gio trnh cng ngh ch bin sa v cc sn

phm t sa. H Ni: NXB Khoa Hc K Thut. .

9. L Vn Vit Mn. 2004. Cng ngh sn xut cc sn phm tsa.TPHCM: NXB i Hc Quc Gia TPHCM.

10. L Th Lin Thanh, L Vn Hong. 2002. Cng ngh ch bin sa v cc

sn phm sa. H Ni: NXB Khoa Hc K Thut.

11. L Xun Phng. 2001. Vi sinh vt cng nghip. H Ni: NXB Xy

Dng

12. Nanak, S. 1997. Dairy Chemistry . Aman Publishing house

13. Nguyn Minh Thu. 2003. Cng ngh sau thu hoch rau qu. Cn Th:

Khoa Nng Nghip - i hc Cn Th

14. Nguyn T Thanh. 2003. Kho st cc yu t nh hng n qu trnh ln

men Kefir - Lun vn tt nghip. Cn Th: Khoa Nng Nghip - i hc Cn

Th

15. Phm Vn S, Bi Th Nh Thun. 1991. Kim nghim lng thc thc

phm. H Ni: Trng i Hc Bch Khoa H Ni.

57
http://www.heliosnutrition.com/http://user.chairot.com.au/~dna/Kefirpage.htmlhttp://www.heliosnutrition.com/http://user.chairot.com.au/~dna/Kefirpage.html


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PH CHNG I

1.1 Phng php xc nh cn ca sn phm :

1.1.1. Dng c vt liu v thuc th :

- Thuc th Nitr Cromic :

Kali bicromat 4,9 g

Acid nitric n c da 1000 ml

- Dung dch Kali iodua 10%

Kali iodua 100 g

Nc ct da 1000 mlPha khi dng : dung dch Natri hyposunfit O. I N. ( Na2S2O3 )

1.1.2 Tin hnh th :

Ly 100 ml mu a loi CO2 cho vo my ct ly dch ct cho n

khi gn cn. Cho thm nc ct vo dch ct va 100ml.

Cho vo bnh nn c nt kn :

- Dch ct 5ml

- Nc ct 5ml

- Dung dch nitro cromic 10ml

y kn nt v tip xc 30 pht, cho thm :

Dung dch kali iodua 10ml

Nc ct 100ml

Lc u. Sau 2 pht, chun iod c gii phng ra th t do bng

dd natri hyposunfit O, I N. Phn ng kt thc mu chuyn t mu vng sang

xanh lc ca cc mui crm III.

Trng hp nu khi cho dung dch nitro cromic vo c ngay mu

xanh lc l cha c tha dung dch nitro cromic, cn phi cho thm hoc

dng lng dch th t hn na.

Lm song song vi 1 mu trng vi 10 ml dung dch nitro cromic v

10 ml nc ct, theo ng thao tc v thi gian nh mu th.

pc-1


72/81

1.1.3. Tnh kt qu :

1 ml Na2S2O3 O.1 N tng ng vi 1.15 mg ru etylic tnh bng

mg trong 1 lt mu cn th :

( N - n )*1,15*1000 / 5

trong :

N : s ml Na2S2O3 0, 1 N dng nh lng mu trng.

n : s ml N2S2O3 0, 1 N dng nh lng mu th.

Mun chuyn sang ru, ngha l s ml ru etylic nguyn cht

trong 100 ml mu, th chia hm lng ru etylic trong 100ml cho 0,79433 t

trng ca ru etylic.

(Ngun : Kim tra Cht lng v Thanh tra V sinh An ton

Thc Phm - Bi Th Nh Thun, Phng Nguyn Tin v Bi Minh c -

NXB Y Hc - 1991).

1.2 Xc nh chua ca sn phm :

Xc nh chua ca sa bng phng php nh lng chua.

1.2.1. Tin hnh th :

- Cho vo mt bnh nn :

Sa cn th : 10ml.

Dung dch Phenolphtalein 5 git.

Chun bng dung dch NaOH 0.1N cho n mu hng nht bn

vng.1.2.2. Tnh kt qu :

chua ca sa, tnh bng T ( Thorner) ngha l s ml NaOH

0.1N dng trung ha cc acid t do trong 100ml sa.

chua ( oT ) = n* 100/10

Trong : n l s ml NaOH 0.1N dng chun 10ml sa.

pc-2


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1.3. Hm lng VSV :

1.3.1. Hm lng vi khun ln men trong sa chua

- Nguyn tc : m s khun lc mc trn mi trng thch dinhdng t mt lng mu xc nh trn c s mi khun lc hnh thnh t 1 t

bo duy nht.

- Mi trng nui cy : Fluid Lactose Medium.

- Tin hnh : s dng phng php m a (Total Plate Count) cc

nng khc nhau. Ly 1ml mu pha long bng pipet v trng cho vo gia

a petri. Rt vo mi a 15ml thch dinh dng. Lc trn xui v ngc

chiu kim ng h, mi chiu 5 ln. t a trn mt phng nm ngang cho

ng t nhin. m 370C trong thi gian 24 - 48 gi.

- c kt qu : m s khun lc trn cc a, tnh gi tr trung bnh

ca cc nng pha long v qui ra lng VSV trong 1 ml mu.

1.3.2.Escherichia Coli

- Mi trng nui cy:

Mi trng tng sinh: Fluid Lactose Medium

Mi trng phn lp: EMB (Eosine Methylene Blue Agar)

- Nguyn tc v tin hnh:

Tng sinh: cy 1ml dung dch mu vo ng nghim cha 5ml mi

trng tng sinh. Dng hai ng nghim cho mi mu

Phn lp: sau 24 gi, dng que cy dch mu t ng c phn ng

dng tnh (c sinh hi, lm c mi trng mu vng) ln mi trng phnlp, 370C trong 24 gi

Nhn dng: trn mi trng EMB khun lc c mu ta, c nh

kim, trn, b u, ng kn

san xuat kerfir

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