Bi ging ru bia 2012

Chng 1: TNG QUAN V RU, BIA1.1 Khi nim

Bia l mt loi nc ung cha cn c sn xut bng qu trnh ln men ca ng l lng trong mi trng lng v n khng c chng ct sau khi ln men. Ni mt cch khc, bia l loi nc gii kht c cn thp, bt mn xp v c hng v c trng ca hoa houblon. c bit CO2 ha tan trong bia c tc dng gii nhit nhanh h tr cho qu trnh tiu ha, ngoi ra trong bia cn cha mt lng vitamin kh phong ph (ch yu l vitamin nhm B nh vitamin B1, B2, PP). Nh nhng u im ny, bia c s dng rng ri hu ht cc nc trn th gii vi sn lng ngy cng tng, i vi nc ta bia tr thnh loi ung quen thuc vi sn lng ngy cng tng v tr thnh ngnh cng nghip mi nhn trong ngnh cng nghip nc ta.Qu trnh sn xut bia c gi l nu bia. Do cc thnh phn s dng sn xut bia c khc bit ty theo tng khu vc, cc c trng ca bia nh hng v v mu sc cng thay i rt khc nhau v do c khi nim loi bia hay c s phn loi khc nhau. 1.2 Lch s nc ta, ngh nu ru th cng c t ngn xa v cha c ti liu no cho bit im khi u.

Hnh 1.1 : Ly bia lager c mu vng ng v bt pha trnBia l mt trong cc ung lu i nht m loi ngi to ra, c nin i t nht l t thin nin k th 5 trc cng nguyn v c ghi chp li trong cc th tch c ca Ai Cp c i v Lng H (Mesopotamia).

Ging nh phn ln cc cht cha ng khc c th b ln men mt cch t nhin, rt c th l cc ung tng t nh bia c pht minh mt cch c lp gia cc nn vn minh trn ton th gii. Vic kim nh ha hc cc bnh gm c pht hin ra rng bia (tng t nh ru vang) c sn xut khong 7.000 nm trc khu vc ngy nay l Iran v l mt trong s cc ngnh cng ngh sinh hc bit, trong cc quy trnh sinh hc ca s ln men c p dng.

Ti Lng H, chng c lu i nht v bia c cho l bc v 6.000 nm tui ca ngi Sumeria miu t nhng ngi ang ung mt th ung bng cc cn ht bng sy t thng cng cng. Bia cng c cp ti trong thin s thi Gilgamesh, mt bn trng ca 3.900 nm tui ca ngi Sumeria t lng tn knh n thn Ninkasi, v thn bo tr cho bia, n cha cng thc lm bia c nht cn st li v miu t vic sn xut bia t la mch thng qua bnh m. Bia tr thnh thit yu i vi tt c cc nn vn minh trng ng cc th gii phng Ty c xa, c bit l Ai Cp v Lng H.

Ngi Thracia cng c bit l s dng bia sn xut t la mch en, thm ch t th k 5 trc cng nguyn, nh Hellanicos vit trong v cc opra. Tn gi cho bia ca h l brutos hay brytos.

S b sung hoa bia vo bia to v ng, bo qun v hng v cho bia l mt pht kin tng i mi. Trong thi trung c nhiu hn hp khc ca cc loi tho mc thng thng c cho vo bia ch khng phi hoa bia. Cc hn hp ny thng thng c gi l gruit. Hoa bia c trng ti Php sm nht l vo khong th k 9. Vn bn c nht cn st li c ghi chp v vic s dng hoa bia trong bia c nin i vo nm 1067 bi n tu vin trng kim nh vn Hildegard: "Nu ngi ta nh lm bia t yn mch, n c chun b cng hoa bia."

Ti chu u, trong thi Trung c, bia ch yu c sn xut trong gia nh. Vo th k 14 v 15, vic sn xut bia dn dn chuyn t hot ng gia nh sang hot ng th cng, vi cc qun bia v tu vin sn xut bia ca mnh hng lot tiu th. Trong th k 15, Anh loi bia khng c hoa bia c bit n nh l ale, cn vic s dng hoa bia th ung gi l bia. Bia c cha hoa bia c nhp khu vo Anh t H Lan sm nht l t nm 1400 Winchester, v hoa bia c trng trn quc o ny t nm 1428. Tnh ph bin ca hoa bia ban u l hn hp Cng ty bia ru London i xa ti mc ra thng bo "khng hoa bia, khng tho mc hoc nhng g khc tng t c cho vo bt k ale hay ru (mi) no s c sn xut m ch c liquor (nc), mch nha v men bia. Tuy nhin, vo th k 16, ale c dng ch cc loi bia mnh (nng cn cao) bt k, tt c ale v bia u s dng hoa bia.

Hnh 1.2: Bia Ha Lan Bia Chu

Nm 1516, William IV, Cng tc x Bavaria, thng qua Reinheitsgebot (lut tinh khit), c l l quy nh v thc phm c nht cn p dng n nay. Gebot quy nh rng thnh phn ca bia ch c bao gm nc, la mch, hoa bia, vi men bia c b sung sau pht kin ca Louis Pasteur vo nm 1857. Lut ca ngi Bavaria c p dng trong c nc c nh l mt phn ca nc c thng nht nm 1871 thnh ch c di thi Otto von Bismarck, v k t c cp nht phn nh xu hng hin i trong sn xut bia ru. Cho n nay, Gebot vn c coi l tiu chun ca tinh khit cho bia, mc d iu ny c th gy tranh ci.

Phn ln cc loi bia cho n thi gian gn y thc cht l th m ngy nay gi l ale. Bia lager c pht hin ra mt cch tnh c vo th k 16 sau khi bia c lu tr trong cc hm lnh mt thi gian di, k t n c sn xut nhiu hn ale. Vi s pht minh ra ng c hi nc nm 1765, cng nghip ha sn xut bia tr thnh s tht. Cc ci tin mi trong cng ngh sn xut bia xut hin cng vi s ra i ca nhit k v t trng k vo th k 19, cho php cc nh sn xut bia tng tnh hiu qu v kim sot nng cn. Cho n cui th k 18, mch nha ch yu c lm kh bng la do t g, than ci, tru, v sau nm 1600 l t than cc. Ni chung, khng c loi mch nha no trong s ny c che chn tt khi khi sinh ra trong cc l sy, v do cc loi bia thi k c thnh phn hi khi trong hng v ca chng, cc chng c ch ra rng cc nh sn xut mch nha v bia thng xuyn phi c gng gim thiu s m khi ca bia thnh phm. S pht minh ra l nng hnh trng nm 1817 ca Daniel Wheeler cho php to ra mch nha nng chn k v to tin cho sn xut cc loi bia en (porter v stout). S pht minh ra vai tr ca men bia trong qu trnh ln men vo nm 1857 bi Louis Pasteur gip cho cc nh sn xut bia phng php ngn chn v chua ca bia bi cc loi vi sinh vt khng mong mun.

Nm 1953, Morton W Coutts, mt ngi New Zealand pht trin k thut ln men lin tc. Morton ly bng sng ch cng ngh ca ng v n l mt cuc cch mng trong cng nghip bia do n lm gim thi gian v sn xut bia trc y l 4 thng xung cn cha y 24 gi. Cng ngh ca ng vn c s dng bi nhiu nh sn xut bia ln nht th gii ngy nay, bao gm c Guinness .

Ngy nay, cng nghip bia l cng vic kinh doanh khng l ton cu, bao gm ch yu l cc t hp c ra i t cc nh sn xut nh hn. Trong khi bia ch yu l ung cha cn th mt s bin thi ca n cng tn ti, xut pht t th gii phng Ty, l cc loi bia i qua cng on x l loi b bt cn, sn xut ra ci gi l bia khng cn.Chng 2: NGUYN LIU TRONG LN MEN RU, BIAC mt s loi nguyn liu chnh dng cho sn xut ru bia nh: nguyn liu cha tinh bt, malt i mch, hops, nc, nm mc v t bo nm men.

2.1 Nc

2.1.1 Cng dng ca nc trong qu trnh sn xut ru bia

Trong cng nghip sn xut ru, bia nc c s dng rng ri vi nhiu mc ch khc nhau nh: dng x l nguyn liu, nu nguyn liu, pha long dung dch, lm ngui bn thnh phm v thnh phm, v sinh thit b, cp nc cho l hi,... ngoi ra trong sn xut bia nc ng mt vai tr rt quan trng nh hng n cht lng bia thnh phm nh nc Brewing (nc nu bia) v nc Dilution (nc pha bia).

+ Nc Brewing (nc nu bia):

Nc ging ( x l Fe, ion kim loi nng (ti trong khng kh cho hp th O2 khng kh) ( Loi Cl (hp ph qua than hot tnh) ( Nc Brewing (hm lng Cl < 0,01ppm).

+ Nc Dilution:

Nc Brewing ( tit trng bng tia UV ( pha vi soda ( Nc dilution.

Ngun nc cung cp trong nh my thng l nc sng ngi, nc my hoc nc ngm, nc ging. Nc thin nhin thng chy qua cc lp nham thch, t nn mang nhiu hp cht v c, hu c v cc loi vi sinh vt gy bnh khc nhau. Nu ngun nc gn khu dn c th trong nc cn nhiu hp cht khc nh: NO3, NO2, NH3,... Ty vo ngun nc s dng v ty vo cng dng ca tng loi nc m c cch x l khc nhau ph hp vi yu cu cng ngh ca nh my.2.1.2 Tiu chun ca nc trong cng nghip sn xut ru bia.

cng khng qu 7mg ng lng/ lt, phi trong sut, khng mu, khng mi. Hm lng mui khng c vt qu gii hn sau:IonHm lng (mg/l)IonHm lng (mg/l)

Cl-0,5F3

SO42-80Zn5

As0,05Cu3

Pb0,1Fe0,3

NO3-40

Khng c hoc ch c rt t cc mui kim loi nng nh: Hg2+, Ba2+,...Kh nng oxi ha 1 lt nc khng qu 2ml dung dch KMnO4 (0,01N).

Cht cn khng vt qu 1000mg/l. Nc mt sng h thng c lng mui khong thp, dao ng t 40 50 mg/l. Nc ngm c lng mui khong nhiu hn, khong 500 3000 mg/l. Hm lng cc cht hu c khng c vt qu 4 mg/l. Vi sinh vt hu nh khng c.

pH kim khng thch hp cho qu trnh nu nguyn liu, c kh nng to iu kin thun li cho vi sinh vt gy bnh pht trin v thc y qu trnh to thnh glyceryl trong qu trnh ln men.

Mui CaSO4, MgCl2, NaCl vi lng t 300 400 mg/l thch hp cho hot ng ca enzyme amylase, lng ng kh tng ln nhng thun khit ca dung dch ng li gim.

Mui sulfat (CaSO4, MgSO4) 400 800 mg/l s lm tng lng ng khng ln men, lm gim tc ng ha v ln men.

Mui CaCO3, MgCO3, Fe2+, Fe3+ vi lng 400 mg/l, mui nitrat 400 mg/l v mui nit 200 mg/l s nh hng khng tt n qu trnh ln men.NH3 vi lng t hn 20 mg/l li c tc dng lm tng hiu sut ln men. Hm lng ln hn th li khng cho php.

Cc mui nitrat, nitric, photphat v silicat vi lng nh hn 200 mg/l khng nh hng n qu trnh ng ha. Mui bicacbonat vi lng khng qu 200 400 mg/l khng nh hng n s ng ha, nhng lng ln hn nh hng r rt n enzyme amylase.E. Coli < 20 t bo/ lt.

2.1.3 Tiu chun ca nc nu biaHm lng cc cht ha tan trong dch ng trc lc ln men l 10 13% i vi bia vng v 16 22% i vi bia en. Do , nc trong sn xut bia c xem nh thnh phn nguyn liu ch yu.

Hm lng cc mui trong nc khc nhau th kh nng tc ng v nh hng ca n ln qu trnh sn xut bia, cht lng bia cng khc nhau.

Ion Ca2+ c mt trong cc loi nc ngm. Hm lng ca n dao ng trong khong kh rng 5 250 mg/l (tnh theo CaO). N tn ti nhiu nht cc dng Ca(HCO3)2, CaSO4, hai mui ny c nh hng tri ngc nhau. Mui bicacbonat th c hi v chng lm gim chua ca dch ng ha do tc dng vi mui photphat ca malt.2KH2PO2 + Ca(HCO3)2 ( K2HPO4 + CaHPO4 + 2H2O + 2CO2Nu pH tng th kh nng thy phn ca enzyme s gim v do hiu sut thy phn cng gim.

Mui CaSO4 lm tng chua ca dch cho. Tc ng ny rt c li cho qu trnh ng ha.4K2HPO4 + 3CaSO4 ( Ca3(PO4)2 + 2KH2PO4 + 3K2SO4Trong sn xut, tng cng s hot ng ca enzyme trong nhiu trng hp cn b sung thm thch cao (CaO), CaCl2.

Ion Mg2+ dao ng trong khong 3 100 mg/l. Chng cng c nh hng tng t nh ion Ca2+. Tuy nhin nu hm lng MgSO4 cao s gy v ng kh chu trong bia.

Ion Na+ tn ti trong nc dng Na2CO3, NaHCO3, Na2SO4, NaCl 15 20 mg/l tnh theo Na2O. Dng natri sulfat nu hm lng cao s c v ng kh chu. Mui n vi hm lng ln cng khng tt nhng vi hm lng khong 200 mg/l s to v m cho bia.Ion K+ trong nc khng nhiu, tc ng ca n ln qu trnh sn xut cng tng t nh Na+.

i vi cng ngh sn xut bia th st (Fe) l yu t kh quan trng. N tn ti trong nc di dng Fe(HCO3)2. Hm lng cao chng nh hng trc tip n cht lng ca malt v bia. giai on ngm trn v ht ta mt lp mng Fe(OH)3. Lp ta ny ngoi vic nh hng ti mu sc (nu ), mi v l cho sn phm m cn nh hng n tc ht nc ca ht v s lm chm tr tin trnh sn xut. Nu hm lng Fe ln n s rt ngn chu k sinh trng ca t bo nm men, lm cho s cn bng trong tin trnh sn xut b ph v. Ngoi ra n cn xc tc qu trnh oxy ha trong bia, lm gim bn keo v to c cho sn phm. Nng ti a cho php ca Fe l 0,2 0,5 mg/l.Mn2+ cng c tc dng tng t nh Fe2+.Hm lng SO42+ trong nc dao ng trong khong 2 250 mg/l. Nu cao qu s lm gim v ng ca hoa houblon, lm c ch s hot ng ca vi sinh vt.

Trong nc cha rt t nitrat v nitric. Nu hm lng ca n cao chng t nc b nhim bn. Ngoi tr Ca(NO3)2, Mg(NO3)2 tt c cc mui nitrat v nitrit u khng nh hng n qu trnh ng ha, cn vi giai on ln men ch c nitrit l c ch hot ng ca nm men.

Trong nc nu bia khng cho php c NH32+Acid cilic c mt trong nc vi hm lng khong 10 30 mg/l. Nu hm lng ln s cn tr qu trnh ln men. Ngoi ra chng cn gy c trong bia.

Cn kh (cht ha tan khng bay hi v cc ht li ti v c, hu c khng ha tan) khng qu 200 500 mg/l. Trong thnh phn ca cn kh cc cu t quan trng nht l:

CaO: 80 160 mg/l

MgO: 20 40 mg/l

SiO2: 5 -15 mg/l

SO3: 5 80 mg/l

Cl: 10 40 mg/l

N2O5: 0 10 mg/l

2.2 Nguyn liu cha tinh bt

2.2.1 c im

L ngun cung cp nng lng chnh, cung cp cht dinh dng cho s hot ng ca vi sinh vt ln men.- Yu cu v nguyn liu: Hm lng glucid cao, tr lng ln, d tm, ng u v kch c, thnh phn ha hc tng i ging nhau, gi thnh thp, d bo qun. iu kin vi sinh vt phi m bo.

m bo cht lng sn phm, tnh ng u ca nguyn liu l mt trong nhng yu t u tin la chn. Do trong cng ngh sn xut bia, nh sn xut thng chn i mch c hai hng ht lm nguyn liu sn xut chnh. Ngoi i mch, gim gi thnh sn phm ngi ta a mt s loi nguyn liu khc dng thay th nh go, bp, tiu mchCc loi ht ny c s dng trng thi cha m mm v a vo ch bin di dng bt nghin mn. T l thay th cc nc thng t 15 20% c khi ln n 30%.

Khi la chn nguyn liu phi da trn thnh phn nguyn liu. Phi phn tch thnh phn amylose, amylosepectin, thnh phn protein, lipid, vitamin, vi sinh vtng thi phi x l nguyn liu trc khi a vo dy chuyn sn xut.2.2.2 Thnh phn nguyn liu ca mt s ht cha tinh bt (tham kho)

Ng cc v cc dng c khcH2O (%)Cht trch ly (%c.k)Nhit gel ha (oC)Cht bo (%c.k)Protein (%c.k)Tinh bt (%c.k)Amylose (%)

Ni nh bp

Tinh bt bp

Ni nh go

Ni nh cao lng

Tinh bt la m

i mch

La m

La mch en

Yn mch

K

Tinh bt khoai ty

Bnh khoai m11-13

8-12

10-13

10-12

10-14

12-16

8-14

10-15

10-16

10-13

10-12

8-1188-93101-106

89-94

75-82

101-107

75-80

70-75

76-80

45-50

79-84

101-105

87-9762-7562-74

61-78

68-75

52-75

57-65

55-70

55-70

55-62

67-77

56-69

52-700,8-1,3250Rt tt

200 - 250Tt

150 - 200Trung bnh

100 - 150Km

< 100Rt km

Hot lc catalaza: l ch s c trng cho mc sy kit ca malt. Qua i lng ny c th hnh dung ra mc to thnh melanoid trong loi malt .

V d: malt vng c ch s ny t 50 80 n v iu kin.

Gi tr ca i lng ny cng cao th lng melanoid to thnh trong malt cng t.

2.4.10 Sn lng ca malt v hao ph trong sn xut

T 100kg i mch lm sch s thu c khong 148 150 kg malt i mch t, 140kg malt ti v 75 78 kg malt kh thnh phm.Trong qu trnh malt ha i mch, hao ph khong 20 25% so vi khi lng i mch lm sch em vo ngm. Trong gn 10% thy phn ca i mch ban u b mt i do qu trnh sy malt (hm m ca i mch l 12 14%, cn ca malt kh l 3,5%). Nh vy, thc cht v hao ph cht kh trong qu trnh malt ha i mch l 10 15%. Phn b cht kh c th hin bng sau:

Dng hao phHt lnHt nh

Ht lp loi ra trong lc ngm

Hao ph c hc trong lc ngm

Hao ph do h hp giai on ngm, m mm v sy

Hao ph theo r1,0

0,6

6,6

4,51,2

0,8

5,5

5,0

Tng hao ph11,613,6

2.5 Hoa HoublonHoublon l nguyn liu c bn, ng v tr th hai sau i mch ca cng ngh sn xut bia.

Hoa houblon lm cho bia c v ng du, hng thm rt c trng, lm tng kh nng to v gi bt, lm tng bn keo v n nh thnh phn sinh hc ca sn phm.

Cy hoa houblon c tn Latinh l Humulus lupulus. c im ca cy ny l hoa c v hoa ci sinh ra hai cy khc nhau. Trong cng ngh sn xut bia, ngi ta s dng nhng hoa ci cha th phn. Khi hoa houblon sp chn th phn hnh nn xut hin nhng ht trn c mu vng xanh ng nh v nhn dnh. l ht luputin l phn gi tr nht ca hoa. Nhng ht ny c ca cht thm, cc cht c v ng c trng nh bia c v ng d chu, c hng thm, bt lu tan, bia bn khi thi gian bo qun ko di.

Hoa houblon c thu hoch vo thi k c gi l chn k thut. thi k ny cc cnh hoa hnh nn ng cht, mu vng xanh hay xanh vng, nhn dnh v ta hng thm. Nu khng thu hoch ng lc th thi k chn k thut s qua i v tip theo l thi k chn sinh l, lc ny cc cnh hoa hnh nn m ra, ht luputin ri rng, hoa mt phn gi tr nht.

Hnh 2.3: Hoa houblonTrong cng ngh sn xut bia, hoa houblon c bo qun di cc dng sau:

+ Sy kh vi nhit sy t 45- 65oC, ty theo tng giai on. m cui cng trong hoa houblon t 10 13%.

+ Ht hoc thi hnh tr: dng my p c p sut cao p cht hoa thnh bnh, bnh hoc thi hnh tr.

+ Cao hoa houblon: hoa houblon c trch ly bng cn 96% ri c c dch trch ly thnh cao. Cao c th bo qun trong thi gian t 3 4 nm.

Thnh phn ha hc ca hoa houblon dng trong sn xut bia thng dao ng trong khong sau: (tnh theo phn trm cht kh)

Nc: 11 13

Cht ng: 15 21

Polyphenol: 2,5 6Protein: 15 21

Cellulose: 12 14

Cht khong: 5 8

Tinh du thm: 0,3 1

Cc hp cht khc: 26 28

Trong cc cu t trn y th cht ng (gumulon v lubulon) l cht c gi tr nht, tip n l tinh du thm v th ba l polyphenol.

Thnh phn ha hc ca hoa houblon ph thuc vo chng ging, k thut canh tc, iu kin kh hu, t ai gieo trng.

2.5.1 Cht ng

Vai tr:

Cht ng c vai tr to ln trong cng ngh sn xut bia. Chng lm cho bia c v ng du, to ra mt c tnh cm quan rt c bit cho bia. Cc cht ng c hot tnh sinh hc cao, to ra sc cng b mt gip cho bia gi bt lu. Ngoi ra cc cht ng c kh nng c ch rt mnh s pht trin ca vi sinh vt. V vy, chng c tnh khng khun rt cao v nh lm tng bn sinh hc ca bia thnh phm. Thnh phn

Cht ng trong hoa houblon bao gm nhiu hp cht. Thnh phn ca chng c th c phn loi theo s sau:

* acid ng: (humulon)

+ Cu to:

Cu t ng quan trng ca acid ng bao gm sau hp cht: humulon, cohumulon, adhumulon, prehumulon v 4 deoxyhumulon. Bn cht ca nhng hp cht ny l nhng axyl alkyl hydroxyl xiclo hexandienon vi cng thc nh sau:

Hnh2.4: Cng thc cu to ca acid ng v acid ng + Tnh cht ca acid ngKh nng ha tan ca acid ng trong cc dung mi khc nhau th khc nhau. kim ca dung mi cng cao th kh nng ha tan ca chng cng nhiu.

V d:

+ Trong nc 500mg/l

+ Trong dch ng < 500mg/l

+ Trong bia 10 30 mg/l

Cc cht ny c kh nng to mui trong phn t ca n khng c cha nhm cacboxyl.

Cc nhm cht ng ny c tnh acid l nhm enol ( C- OH) to nn. giai on un si dch ng vi hoa houblon, cc hp cht humulon khng trc tip ha tan vo m chng phi tri qua mt giai on trung gian l qu trnh ng phn ha. Sau cc cht ng phn ny ha tan v b thy phn thnh cc sn phm c ng cao hn rt nhiu so vi cc hp cht nguyn thy

* acid ng (hupulon)+ Cu to:

Nhm acid ny bao gm bn hp cht: lupulon, colupulon, adlupulon v prelupulon. Cng thc cu to ca chng nh trn.

+ Tnh cht

Lupulon l hp cht dng tinh th, mu trng, dng lng knh hoc hnh que di, nng chy 92oC. So vi humulon th lupulon km ng hn nhng li c tnh khng khun cao hn. Kh nng ha tan ca acid ng trong nc, trong dch ng thp hn nhiu so vi acid ng.

Khi un si hoa houblon vi dch ng, lupulon cng b ng phn ha v sau cc ng phn mi b phn ct v khi lng nh git.

Khi b oxy ha cc acid ng chuyn thnh acid ng lm tng kh nng ha tan vo dch ng. Nhng nu phn ng ko di, humulon s b oxy ha v s tr thnh nha mm sau thnh nha cng.

Nha mm:

Nha mm l polyme ca cc acid ng, l cht v nh hnh. Kh nng ha tan ca nha mm vo dung dch ng cao hn acid ng, v vy chng to ra c lc ng kh ln cho bia. Nha mm l hp phn c gi tr ca cht ng.

Nha cng:

Nha cng l polyme ca cc acid ng nhng mc cao hn nhiu so vi nha mm. Cu t ny hu nh khng ha tan vo nc v dch ng. Chng b thi ra ngoi theo cn lng. y l hp phn khng c gi tr trong cng ngh sn xut bia.Cng thc lc ng ca Wollmer

acid ng + nha mm

Lc ng = acid ng +

92.5.2 Tinh du thmTinh du thm ca hoa houblon ha tan vo dch ng, tn ti trong bia v to ra cho n mi thm c trng, rt nh nhng v d chu.

Tinh du thm l nhng cht lng trong sut mu vng nht hoc khng mu, tinh du thm c mi thm rt mnh. T trng ca chng l 0,88. D ha tan trong ru etylic nng cao. Tinh du thm bay hi kh mnh nhit thng.

Thnh phn ha hc ca tinh du thm trong hoa houblon rt phc tp, bao gm 103 hp cht khc nhau. Ch yu l nhng terpen, ru, ceton, aldehyde, ester v acid.

i din tiu biu ca nhm hydrocacbon l miroxen (C10H16), humulen (C15H24). Trong nhm ru tiu biu l geraniol (C10H18O), linalool (C10H18O) l ng phn ca geraniol.

i din tiu biu ca nhm ceton l luparol (C13H23O)

i din tiu biu ca nhm aldehyde thm l formaldehyde

Trong thi gian un si dung dch ng vi hoa houblon, c n 98% lng tinh du thm bay ra ngoi theo hi nc, ch cn li 2% tn ti trong bia.

2.5.3 Polyphenol

Gi tr ln nht ca polyphenol l kt lng v loi b cc hp cht protit cao phn t ra khi dch ng, lm n nh thnh phn v tng bn keo ca bia thnh phm.Polyphenol trong hoa houblon trong nhm flavonoid l d dng thc hin phn ng ngng t to thnh oligome v d dng polyme ha to thnh polyme. Mt khc, oligome to thnh d dng kt hp vi protein cao phn t to thnh cc phc cht khng ha tan. V l do , polyphenol ca hoa houblon c dng loi tr cc cu t protein kh bin tnh v kt lng ra khi dch ng.

Chng 3: NG HA TRONG SN XUT RU, BIA3.1 Th no l mt qu trnh ng ha

ng ha l mt qu trnh chuyn ha bin tinh bt thnh ng ln men phc v cho qu trnh ln men. Sn phm thu c gi l dch ng ha. y l cng on rt quan trng trong cng ngh ln men.

ng ha c nhiu phng php khc nhau tuy nhin chng ta c th phn thnh 2 loi c bn: ng ha bng phng php vi sinh vt (mold) v ng ha bng phng php enzyme (phng php malt). Ngoi ra cn c c phng php thy phn bng acid (t c s dng do c tnh ca sn phm), phng php s dng men thuc bc, phng php amylomyces rouxii.

Tuy nhin d trong phng php ng ha bng vi sinh vt hay phng php malt th vic s dng ngun enzyme c sn trong nguyn liu (malt) hay c sn sinh t vi sinh vt l vic lm ht sc quan trng.

3.2 H enzyme amylase trong qu trnh ng ha

H enzyme amylase l mt trong cc h enzyme c s dng rng ri nht trong cng nghip, c bit l ngnh cng nghip ru bia.

Nhng nghin cu thc nghim v enzyme ni chung v v amylase ni ring c bt u vo nhng nm 1811 - 1814. Nhng nghin cu ny gn lin vi tn tui ca nh bc hc ngi Nga - Vin s K.S Kirhof. ng nghin cu qu trnh phn gii tinh bt di tc dng ca dch chit i mch ny mm (malt) v nhn thy rng trong malt c cha cc cht phn gii tinh bt thnh ng. n nm 1983, hai nh khoa hc Payen v Persoz tch c cht phn gii tinh bt t malt v t tn l diaslase (phn gii). Sau ny theo ngh ca Duclo, enzyme thy phn tinh bt c gi l amylase.

Enzyme amylase c trong nc bt, dch tiu ho ca ngi v ng vt, trong ht ny mm, nm, vi khunNhng ngi ta ch yu sn xut amylase t vi khun, nm mc v mt s loi nm men (Nguyn c Lng, 2004).C nhiu ngun cung cp amylase khc nhau nn ty vo ngun sinh ra m enzyme s c iu kin pht trin ring, v d: nhit , pH,...Cng mt loi enzyme amylase ( amylase) nhng khc ngun cung cp th cng s c iu kin v nhit , pH khc nhau.

Amylase l enzyme rt thng dng, c s dng nhiu trong cng nghip thc phm. Enzyme ny lm nhim v thy phn tinh bt thnh cc phn t ng n gin nh glucose, maltose. Enzyme amylase c xp thnh hai nhm:

* Endoamylase (enzyme ni phn): gm c -amylase v nhm enzyme kh nhnh.

* Exoamylase (enzyme ngoi phn): gm c -amylase v -amylase.

Hnh 3.1 C ch xc tc phn ng thy phn tinh bt ca enzyme amylase

3.2.1 -amylase (EC 3.2.1.1)

-amylase, cn c gi l 1,4--D-glucan glucanohydrolase, xc tc thy phn tinh bt cho ra dextrin v cc oligosaccharide c nhm C1-OH v tr . Enzyme ny c trong ng vt, thc vt, vi khun v nm mc (Naz, 2002).

-amylase l mt metaloenzyme, trong phn t lun c t nht mt nguyn t gam calci c tc dng lm bn cu trc bc 2, 3 ca phn t enzyme, -amylase l nhng protein n gin, c cha nhm amin t do. Cc -amylase kh giu tyrosine, tryptophan nhng cha t methionine (L Nguyn Bnh, 1997).

Enzyme -amylase phn ct cc lin kt -1,4-glucoside nm bn trong phn t c cht (tinh bt, glycogen,) mt cch ngu nhin khng theo mt trt t no c.

-amylase c hot ha bi ion n ha tr nu chng c ngun gc ng vt v vi sinh vt. Nu c ngun gc thc vt th c hot ha bi ion ha tr II. Hot ha bi ion ha tr I nh sau: Cl- > Br- > I-. Chng b kim hm bi ion kim loi nng nh: Cu2+, Hg2+.

-amylase km bn trong mi trng acid nhng kh bn nhit (bn nht trong h enzyme amylase).

Kh nng chu nhit ca enzyme amylase trong vi khun > malt > mc.

Ngun gcNhit ti thchpH ti thch

MaltMold

Vi khun72 7550 60

60 - 705,5 5,75,0 6,0

6,0 7,0

Qu trnh thy phn tinh bt bi -amylase l mt qu trnh a giai on:

- Giai on dextrin ha: giai on ny ch mt s lin kt trong phn t c cht b phn hy to thnh mt lng ln dextrin phn t thp.

- Giai on ng ha: cc dextrin phn t thp va c to thnh b thy phn tip tc to ra cc tri, tetra-maltose khng cho mu vi iod. Cc cht ny b thy phn rt cao bi -amylase cho ti disaccharide v monosaccharide.

Di tc dng ca -amylase, amylose b phn gii kh nhanh to thnh oligosaccharide gm 6-7 gc glucose. Sau mch ny c b ct ngn dn v b phn gii chm n maltotriose, maltose. Qua mt thi gian tc dng di, sn phm thy phn ca amylose cha 13% glucose; 87% maltose.

Tc dng ca -amylase ln amylopectin cng tng t nhng v -amylase khng phn ct c lin kt -1,6-glucoside v tr mch nhnh trong phn t amylopectin nn d c chu tc dng lu th trong sn phm cui cng ngoi maltose (72%), glucose (19%) cn c dextrin phn t thp v isomaltose (8%).

Tuy nhin, thng thng -amylase ch thy phn tinh bt thnh dextrin phn t thp khng cho mu vi iod v mt t maltose (L Nguyn Bnh, 1997).

3.2.2 -amylase (EC 3.2.1.2)

-amylase cn c gi l 1,4--D-glucan-maltohydrolase, l mt exoenzyme xc tc thy phn tinh bt cho ra maltose c nhm C1-OH v tr . -amylase ch ph bin trong cc ht ca thc vt bc cao v trong khoai lang (Naz, 2002).

Maltose l sn phm ch yu ca hot ng -amylase. Khc vi -amylase, -amylase rt bn khi khng c ion Ca2+. -amylase b km hm bi Cu2+, Hg2+, ure, iod, ozon(L Nguyn Bnh, 1997).

Theo c tnh tc dng ln tinh bt, -amylase khc -amylase mt s im: n hu nh khng thy phn tinh bt nguyn lnh m li thy phn mnh m h tinh bt.

Enzyme -amylase phn gii 100% amylose thnh maltose v 54-58% amylopectin thnh maltose. Qu trnh thy phn amylopectin c tin hnh t u khng kh ca cc nhnh ngoi cng. Khi gp lin kt -1,4-glucoside ng k cn lin kt -1,6-glucoside th -amylase ngng tc dng. Phn saccharide cn li l dextrin phn t ln c cha rt nhiu lin kt -1,6-glucoside v c gi l -limit dextrin. nht ca dung dch gim chm (L Nguyn Bnh, 1997).

3.2.3 Glucoamylase (EC 3.2.1.3)Glucoamylase l mt exoamylase, cn c gi l -amylase hay amyloglucosidase. Enzyme ny xc tc thy phn c hai lin kt -1,4 v -1,6-glucoside cho ra sn phm thy phn l glucose vi nhm C1-OH v tr . y l loi enzyme c tm thy trong vi sinh vt, ch yu l nm men v nm mc. Enzyme thng mi thng c sn xut t Aspergillus (Naz, 2002). Theo l thuyt, enzyme ny c th thy phn tinh bt to ra glucose c hiu sut n 100% (Nguyn c Lng et al., 2004).

Tc dng ca glucoamylase rt ging -amylase: thy phn polysaccharide t u khng kh to ra glucose, nhng khc vi -amylase ch n thy phn tun t tng lin kt glucoside to thnh phn t glucose. Enzyme glucoamylase c kh nng xc tc thy phn c lin kt -1,4-glucoside ln -1,6-glucoside trong tinh bt, glycogen v polysaccharide ng loi.

Ngoi tc dng phn ct cc lin kt -1,4-glucoside v -1,6-glucoside, glucoamylase cn c kh nng phn ct c lin kt -1,2-glucoside v -1,3-glucoside na. Enzyme glucoamylase c kh nng thy phn hon ton tinh bt, glycogen, amylopectin, dextrin, isomaltose v maltose ti glucose. Khi thy phn tinh bt, cng vi vic to thnh glucose cn c th c s to thnh cc -oligosaccharide. Cc c cht c cu to phn nhnh (amylopectin, glycogen) b glucoamylase tn cng vi vn tc kh ln. Tuy nhin, n khng thy phn c cc dextrin vng (L Nguyn Bnh, 1997).

Enzyme ny kh bn vi acid nhng li km bn di tc dng ca ru etylic, acetone, khng bn vi ion kim loi nng nh Cu2+, Hg2+N c gi tr c bit trong sn xut ru, thy phn nhng dextrin c phn t cao khng ln men c v do nng cao c hiu sut thu hi ru t cc nguyn liu tinh bt (Lng c Phm, 2004).3.2.4 Pullulanase (EC 3.2.1.41)y l -1,6-glucosidase, c c tnh ring l tn cng polysaccharide (hp cht pullulan). Pullulan l mt chui ca nhng n v maltotriose c ni bi lin kt -1,6. Maltotriosyl l chui polyme ca glucose ni vi nhau bi lin kt -1,4. Pullulanase tn cng lin kt -1,6 bt k trong chui polysaccharide (hp cht pullulan). Ko di s thy phn, kt qu hn 90% pullulan chuyn ha n maltose. Pullulanase cng s thy phn lin kt -1,6-glucoside trong amylopectin v dextrin ti hn, cho ra t nht cng l hai n v D-glucose (L Nguyn Bnh, 1997).

3.2.5 Isoamylase (EC 3.2.1.68)

L enzyme ct nhnh, thy phn nhng lin kt -1,6-glucoside trong amylopectin, glycogen, maltodextrin v oligosaccharide. Khng ging vi pullulanase, isoamylase c hot tnh mnh i vi amylopectin v glycogen, hot tnh rt yu vi pullulan. Nu lng enzyme dng ln, isoamylase s thy phn hon ton pullulan n maltose. Enzyme ny thng c thu nhn t nm men v nm si (L Nguyn Bnh, 1997).

Mc d isoamylase v pullulanase u c cng kiu ct mch amylopectin nhng chng c tnh chn lc ring. Isoamylase ch yu ct lin kt -1,6-glucoside trong cc mch di, cn pullulanase ch yu ct lin kt 1,6-glucosid ni nhng mch ngn hn (Beldman v Vincken, 2002) Ch : Khi s dng h enzyme amylase trong sn xut ru bia:

- Ngun gc ca h enzyme amylase bit c khong nhit , pH thch hp. Nm c cht hot ha, cht c ch i vi tng enzyme lm tng kh nng hot ng ca n. Tng nhanh hiu sut ng ha.

- Ty nguyn liu c th c thnh phn amylose, amylosepectin khc nhau m s dng loi enzyme, t l enzyme thch hp, cn i.

- Ty tng loi men, tng loi sn phm ln men m c thnh phn nguyn liu khc nhau, hm lng ng ln men khc nhau, dn n chng ta dng loi enzyme khc nhau. Ni cch khc chng ta phi bit c cc tnh cht ca ngun enzyme ang s dng nh t l loi enzyme, nhit , pH thch hp ca enzyme . Mun nm c cc c tnh ny chng ta phi thc hin cc php th nghim. 3.3 Cc yu t nh hng n qu trnh ng ha3.3.1 nh hng ca nng enzyme

Trong iu kin khng thay i v chng loi enzyme, nng c cht, thi gian thy phn, nhit mi trng, pH mi trng th khi tng nng enzyme th tc ng ha tng.

Trong sn xut tc ca s thy phn l mt hm s, l s tc dng tng hp ca phc h enzyme mc v men. Phc h enzyme nu c s khc nhau v loi, lng, hot tnh khc nhau th kt qu ca s thy phn tinh bt cng khc nhau.

Nhn chung, trong iu kin tha c cht, tc phn ng ph thuc tuyn tnh vo nng enzyme, ng biu din c dng nh sau (L Ngc T et al., 2005).

Hnh 2.3 th biu din s ph thuc ca tc phn ng vo nng enzyme

3.3.2 nh hng ca nhit

Tc phn ng ca cc enzyme cng nh phn ln cc phn ng ha hc khc u tng khi nhit tng. Tnh ph thuc ca hng s tc phn ng vo nhit c th hin nh sau:Trong :

dlnK E

=

dT RT2T: nhit tuyt i

R: hng s cht kh

E: nng lng hot ha thy phn tinh bt

K: hng s vn tc phn ng.

Nng lng hot ha tinh bt E = 13.000 16.000 Kcal/mol.Mi loi enzyme c nhit thch hp cho s pht trin khc nhau. Nu vt qu nhit ny th chng s b bin tnh v tr nn tr hn i vi c cht.

Khi ng ha nhit cao dextrin to ra nhiu hn so vi ng kh. Thm vo trong nm men khng c hoc c rt t amylase v glucoamylase nn khng th thy phn tip tc dextrin thnh ng. Do vy dn n hiu sut thu hi gim.

Qu trnh ng ha trong sn xut ru t tinh bt khng c phn hy hon ton, thng ch t 20 30%. Khng c ko di thi gian ng ha qu lu to thnh nhiu ng, v nh vy chu k sn xut ko di hot tnh enzyme amylase s b nh hng. Khng nn cho enzyme amylase hot ng trong iu kin nhit vt qu gii hn nhit ti thch, v thc nghim cho thy s lm mt hot tnh enzyme amylase rt nhiu. Tt nht l cho chng hat ng nhit thp hn nhit ti thch mt t. Nhit ti u bo v hot tnh ca enzyme khng hon ton tng ng vi nhit ti u ca s ng ha.Khi sn phm ng mi hnh thnh vi lng t, nhit ti thch bo v hot tnh ca enzyme amylase l 50 56oC. Khi sn phm hnh thnh tng i nhiu, nhit ng ha khng nn vt qu 57 58oC. Nu vt qu nhit ny th hiu sut tng thu hi thp. Nhit ng ha cao hn c tc dng st trng nhng nh hng xu n amylase v s to ra nhieeud dextrin (sn phm ny cng t cng tt). Nhit thy phn thp (40 45oC) s b vi khun c trong dch nm mc, dch sa malt tn cng. Tuy nhin nhit ng ha thp s to ra nhiu ng hn c th t 67 80% qu trnh ln men ru trit hn.

So vi amylase ca malt, amylase ca mc nhy cm hn vi nhit . Khi ng ha bng enzyme amylase ca Aspergillus oryzae, nhit < 50 52oC, enzyme glucoamylase ca Aspergillus niger bn nhit hn so vi amylase do nhit ngha c th cao hn cht t.Do bn cht ca enzyme l protein nn nhit c nh hng rt ln n cu trc ca chng. Khi nhit tng th tc phn ng tng, tuy nhin tc phn ng ch tng theo nhit trong mt gii hn xc nh khi m cu trc ca protein cha b ph v. Vt qua nhit , tc phn ng enzyme s gim v dn n mc trit tiu. Nhit tng lm gia tng c hi ph v cc lin kt phi cng ha tr (lin kt hydro, tng tc Van der Waals), nh hng n cu trc khng gian ba chiu, dn n vic lm bin tnh enzyme (L Ngc T et al., 2005).

Hnh 2.4 th biu din nh hng ca nhit n tc phn ng enzyme

Nhit tng ng vi tc phn ng enzyme cao nht c gi l nhit ti u. Nu nhit tng ln cao hn mc nhit ti u th hot tnh ca enzyme s gim. Khi enzyme khng c kh nng phc hi li hot tnh.

3.3.3 nh hng ca nng ion H+Bn cht ca enzyme l protit do vy tnh cht ca n cng ging nh protit. Nhng nhm ha hc c bn ca enzyme c kh nng ion ha. S hin din ca ion H+, OH- l gim kh nng ion ha ca cc nhm ny hay nhm khc. Nu nhm ny l trung tm hot ng ca enzyme th n s gy ra s km hm hoc kch thch enzyme ty nng

pH ti thch ca enzyme amylase dao ng trong khong 4,5 5,5

nh hng pH i vi enzyme cn ph thuc vo nhit . Kt qu nghin cu cho thy khi nhit tng th pH cng c xu hng tng theo.

Bng mi quan h gia nhit v pH trong qu trnh ng haNhit (oC)Vng pH thch hp

30 40

50

60

704,4 5

4,6 5

5,2 5,5

5,3 5,8

3.3.4 nh hng ca cht st trng ngn chn s nhim khun trong qu trnh ng ha, cc nh my sn xut ru thng s dng Na2SiF6, formol vi nng 0,02 1,25% khi lng. Cho vo khi nu trc khi ng ha hay cho vo trong dch sa malt hoc c th ng thi chho vo khi nu v dch ln men.Nu cht st trng cao d tiu dit lun c mc, men nhng n khng gy c ch enzyme c khi li kch thch s hot ng ca enzyme.3.3.5 nh hng ca nng ruQu trnh ng ha xy ra trong thi gian ngn, tinh bt khng hon ton b thy phn m qu trnh thy phn cn tip tc n khi kt thc qu trnh ln men. Trong qu trnh ny nng ru tng dn do ng ln men c tc dng nht nh n phc h enzyme amylase.

Bng: nh hng ca nng ru n hiu qu qu trnh ng ha

Thi gian ng ha (thy phn), gi

Mu i chngng glucose to thnh, %

Nng ru cho vo, %V

4610

12

24

36

504,47

5,12

6,35

6,825,15

6,18

6,43

6,824,90

5,92

6,35

6,824,66

6,18

5,97

7,04

3.3.6 Thi gian ng ha

Thi gian ng ha c ngha thc tin trong sn xut. N ph thuc vo phng php lm ngui khi nu v phng php ng ha. Thi gian lm ngui quyt nh nng sut thit b, cht lng ca dung dch ng ha v tng hiu sut thu hi.

Thi gian ng ha c nh hng n s ha tan tinh bt khng ng ha. Khi ng ha khi nu 55 58oC trong thi gian 15 150 pht, hu nh ng ln men khng tng, nhng nng cht tan tng ln l do s ha tan ca tinh bt khng ng ha. Nh vy thi gian ng ha tng nng cao hm lng cht kh ha tan v nng cao tnh m ca dung dch. Tuy nhin ko di thi gian ng ha 55 58oC s lm gim hot tnh ca amylase, kh nng nhim khun tng, do vy hiu sut thu hi gim.3.4 Qu trnh ng ha tinh bt thnh ng ln men

3.4.1 Nu nguyn liu

- Mc ch:

Tinh bt ca cc ht ng cc nh ng, go, la mc mng t bo bo v nn men amylase khng th tip xc trc tip c. Khi nghin nguyn liu th ch c mt phn tinh bt b ph hy. Mt khc tinh bt sng khng ha tan trong nc do vy nn khi ng ha enzyme amylase tc dng vo rt chm. Do , nu ph v t bo tinh bt, bin tinh bt t trng thi khng tan thnh trng thi ha tan. Gip cho qu trnh tip xc gia enzyme v t bo tinh bt c d dng.- S trng n v ha tan tinh bt:S trng n ca tinh bt l hin tng tinh bt ht nc trng ln tng th tch v khi lng ca ht. Nu l tinh bt kh tuyt i th giai on u tinh bt s ht nc 20 25% km theo hin tng ta nhit. Giai on sau s khng c hin tng ta nhit v thay i ln i vi t bo.

Khi nu tinh bt vi nc n nhit 40oC ht bt u trng n. Nu tip tc tng nhit th ht tip tc trng n n khi to thnh mt th ng nht gi l s trng n v hn. Khi nhit tng n gii hn nht nh, th tch ca ht tinh bt tng 50 100 ln. Lc lin kt gia cc phn t yu dn n mc tinh bt tan ra gi l s h ha tinh bt. trng thi ny ch mi mt phn nh tinh bt b ph v. iu ny chng t rng s cu to bn vng ca tinh bt l do s kt hp gia cc phn t ln ca cc chui tinh bt gia cc mch chnh v nhnh thnh nhng mng gia cc mng l amylose v amylopeectin.Cc mch thng trong ht tinh bt lin kt vi nhau bng lc Vanderval v lin kt hydro. Ngoi cc lin kt trn trong mch tinh bt cn c nhng lin kt khc chc chn hn (do s xon mch ca cc mch amylose lm cho chng sit cht ly nhau) chnh cc nguyn nhn ny lm cho qu trnh nu mun ph v chng cn phi tiu tn mt nhit lng cn thit.Nhit h ha ca amylose thp hn so vi amylopectin do c im cu to. Do , i vi tng loi nguyn liu khc nhau, kch thc ht tinh bt khc nhau, thnh phn cng khc nhau nn c nhit h ha khc nhau.V d: khoai ty 56 70oC, la m 50 80oC, go 65 73oC.

Tc trng n ca cc ht nh sau:

Mch en > la mch > kiu mch > k > la m > ng.

qu trnh nu c tt, khi nu nguyn liu ht, ngi ta b sung mt lng nc cn thit bo m cho s ha tan tinh bt. Mt khc nhm t c nng cht kh theo yu cu. Ty theo phng php ch bin, nguyn liu m phi b sung lng nc nht nh hay khng cn b sung. V d, khoai ty, khoai lang ti, sn 35 40oC nht khi nu thp nht v nht ca nc gim xung, sau tng chm. nhit 63 85oC nht t n cc i, nhng tip tc gim na th nht li tip tc gim nhanh chng.

Khi lm ngui dung dch amylopectin ng c nhanh hn, nhit 55oC bin thnh keo lm cho men amylase khng th tc dng c. i vi dung dch amylose th rt khng bn vng v nhanh chng lin kt vi nhau to thnh nhng ht nh li ti kt ta xung v cng lm cho enzyme amylase khng tn cng vo c. Do , gim kh nng ng ha (gi l s lo ha). V vy trong sn xut ru sau khi nu xong phi lm ngui nhanh khi nu n nhit 60 62oC v ng ha. Ngoi ra c th p dng cc phng php k thut khc khc phc hin tng trn. Bin php ph bin l dng enzyme amylase dch ha trc hay sau khi nu nguyn liu.Trong sn xut ht thng c nghin nh nn ngay trong qu trnh nu, d l phng php gin on hay lin tc cn ch rng s trng n rt nhanh do phi chn nhit v thi gian sao cho khng c s h ha cc b.

3.4.2 Cc giai on ca qu trnh ng ha

- Giai on dch ha:

Khi cho enzyme amylase tc dng ln dung dch h tinh bt, hin tng xut hin u tin l nht ca dung dch s gim xung, dung dch b long ra. Cc sn phm to thnh trong giai on ny l dextrin phn t cao v mt lng nh ng. Nh vy c th quan nim s dch ha l s ph hy cc tp hp tinh bt thnh nhng phn t ring bit, ri li phn ly tip tc thnh cc dextrin phc tp.Trong h enzyme amylase th amylase l enzyme in hnh gy ra s dch ha. C th lm tng s dch ha bng 3 phng php:

+ Thm cc cht lm tng hot ca enzyme v cc cht n nh enzyme. Cc cht ny c th tc dng nh nhng cht kch thch tht s hoc c tc dng ha tan hay n nh enzyme trong iu kin no hay to ra nhng iu kin thun li cho tc dng ca enzyme. Chng hn bn nhit ca amylase tng ln khi thm mt lng nh Ca2+.+ Tch cc cht km hm enzyme trong nguyn liu. Thng thng l ion Cu2+ d mt lng nh cng nh hng km hm n hot ca enzyme.+ nh hnh mt phn tinh bt trc khi cho enzyme tc dng.

Khi sn xut ru t ht, ngi ta thng dng enzyme amylase dch ha trc khi nu. Vi s dch ha nh th kh nng nu cho c nng m c hn, tit kim hi v thit b. dch ha, ngi ta trn ht nghin nh vi nc cha enzyme dch ha, gi 10 15 pht nhit h ha ca tinh bt. Nng nhit ln nhit h ha v gi 15 20 pht, sau tin hnh nu.- Giai on dextrin ha:

Trong giai on ny, cc phn t tinh bt s b thy phn ngn dn. Do , nht ca dung dch gim dn. Phn ng ca h tinh bt vi iod cng thay i t mu xanh n ri nu v cui cng l khng mu. Nh vy dextrin chng qua l mt loi polysaccharide trung gian gia tinh bt v maltose, ng vi gam mu t tm n xanh ri khng mu. Tc nhn gy ra qu trnh dextrin ha l amylase , amylase ty theo c ch tc dng ca chng m c th chia ra cc dng dextrin ha nh sau:+ Nu cho amylase thun khit thy phn th trong ton b qu trnh ta s thy xut hin y cc dng dextrin. Dextrin ny thng c tn l amylodextrin. Sn phm cui c mu vi iod. y c th xem nh va c s dextrin ha va c s ng ha amylase v maltose to thnh khng hon ton v dextrin to thnh phc tp.+ Nu cho hn hp (amylase th s to thnh ng kh cng nh s to thnh dextrin v khng c mu xanh vi iod.- Giai on ng ha

L giai on phn ly cc dextrin thnh maltoz v glucoz gm hai giai on phn ng:

+ Giai on u: xy ra khi lng c cht rt ln so vi lng enzyme. V th tc ng ha ph thuc vo enzyme mt cch tuyn tnh.+ Giai on sau: phn ng tin trin chm hn v khng ph thuc vo nng enzyme. Da vo c ch tin trin ca tin trnh c th chia tin trnh ng ha thnh 3 dng:

Tc nhn ng ha duy nht l amylase th to thnh nhm kh tuyn tnh, ph thuc vo nng enzyme. Phn ln qu trnh ng ha khng phi do enzyme tc dng trc tip ln dextrin m l do s phn ly sau ny ca dextrin. Nu tc nhn l amylase s ng ha xy ra nhanh chng giai on u v c th ph thuc tuyn tnh vo nng amylase. S to thnh ng gim dn giai on sau v kt thc khi c khong 80% dextrin chuyn thnh maltoz. Nu tc nhn l , amylase th giai on u dextrin chuyn nhanh thnh maltoz, giai on sau phn ng xy ra chm nhng ng vn to thnh lin tc v u n cho n khi ht dextrin chuyn thnh maltoz v glucoz.3.4.3 Thy phn protein (trong sn xut bia)Hm lng cc hp cht cha nit trong thnh phn cht ha tan ca dch ng i vi bia ch chim khong 5 7% so vi tng s cht ha tan. Tuy nhin n ng vai tr rt quan trng trong vic bo m tin trnh ln men c bnh thng v nh hnh cht lng ca sn phm. Pha sn phm thp phn t ca qu trnh thy phn (acid amin v peptid) l ngun dinh dng cho nm men sau ny. Pha c phn t lng trung bnh (albumoza, pepton v polypeptid) gp phn khng nh cho vic to v m cho sn phm. N cn tham gia vo vic to v gi bt cho bia (cng vi s hin din ca hoa houblon).

Trong cng ngh sn xut bia, hm lng cc hp cht thp phn t cha nit l mt ch s quan trng, nhng quan trng v c ngha hn l t l gia cc pha thy phn. Mi loi bia u c nhng yu cu ring v t l gia pha thp phn t v phn t lng trung bnh. V c cu thnh phn ca sn phm thy phn protein, ni chung l c nh ot giai on ng ha.Protein c nhiu tnh cht v kh nng ht sc k diu. C c iu ny l do chng c 4 dng cu trc 1, 2, 3, 4. Trong cu trc bc 1 l cu trc ph bin v quan trng hn c.

- H enzyme v c im ca qu trnh thy phn protein:

Phn ng thy phn protein bi enzyme thc t xy ra giai on m mm i mch. giai on s thy phn xy ra chm, nhng trit , c ngha l qu trnh thy phn mang tnh b su, sn phm to thnh ch yu l cc hp cht thp phn t d ha tan bn vng vo nc. n giai on ng ha, qu trnh ny tip tc nhng vi tc cao hn v cc iu kin thun li hn cho s hot ng ca cc enzyme thy phn. Khc vi tinh bt (hn 80% cc chuyn ha thnh cc sn phm ha tan) giai on ny ch c khong 1/3 2/5 tng lng cc hp cht cha nit c chuyn ha thnh cc sn phm ha tan, phn cn li b thi ra ngoi theo b malt hoc di dng kt ta. trong i mch thng c khong 1,5 1,6 % lng protein ha tan (cc hp cht cha nit tnh theo protein) ngha l khi lng ca chng chim khong 15 16% ca lng m tng s. Thy phn protein trong giai on ng ha khc vi giai on ny mm thnh phn cc cht to thnh. Thy phn giai on m mm th mang tnh chiu su (sn phm ch yu l phn t thp). Giai on ng ha c mc th hn (sn phm to thnh ch yu thuc phn t trung bnh: albumoza, pepton, peptid bc cao). Theo Kolbach th 56% lng m formol trong dch ng l c to thnh thi im m mm, cn giai on ng ha ch to c 23%, phn cn li 21% l c sn trong i mch.Mt phn cc sn phm thy phn ha tan vo dch ng, s bin tnh v kt ta ngay giai on ng ha, mt phn na s b bin tnh v kt ta qu trnh un si dch ng vi hoa houblon. C ngha i vi bia l phn cha nit tn ti li trong dch ng ha sau 2 giai on . Gi chng l cc protein bn nhit. Trong phn ny vn cn hai loi sn phm: loi th nht l khng bao gi kt lng, tc l chng to thnh dung dch bn vng; loi th hai tuy trc mt cha kt lng nhng iu kin no s kt lng v y chnh l nguyn nhn gy c cho dch ng v bia. Trong qu trnh sn xut cng loi b c dng ny cng nhiu th cng tt. giai on ng ha ca protein n gian v phc tp u chu tc ng phn ct ca proteaza nhng c ngha hn trong sn xut bia l s thy phn ca cu t th nht (protein n gin).

Tham gia thy phn giai on ng ha c hai loi enzyme exopeptidase (cn gi l peptidase phn ct polypeptide thnh dipeptide v sau thnh acid amin, c tnh c hiu rt cao vi c cht) v endopeptidase (proteinase phn ct lin kt peptide ca protein to thnh albumoza, pepton, polypeptit, pH ti thch l 4,6 4,9).

- Cc yu t nh hng n c cu sn phm thy phn proteinBng nh hng ca nhit v pH ca dch cho n cc sn phm to thnh

pH

Nhit (oC)S gia tng hm lng nit trong giai on ng ha, mg/100g cht kh ca malt

Nit ha tan bn vngNit aminNit kt ta vi MgSO4

6,56,0

5,5

5,04050

60

40

50

60

40

50

60

40

50

6097114

140151

203

220

220

298

323

278

370

3863041

41

55

60

56

71

90

85

84

110

1031114

36

13

24

49

19

33

62

23

40

63

Bng: nh hng ca nhit v thi gian ng ha n hm lng cc pha sn phm cha nit.

Nhit dch cho (oC)Hm lng nit, mg/100g cht chit ca dch ng

Tng lng nit ha tanNit ha tan bn vngm formol

Thi gian ng ha, gi

232323

040

50

55

60

65

70-293

528

547

535

517

481437615

661

645

618

568

519-642

681

664

625

572

518-345

383

406

423

420

413292452

503

519

516

490

452-481

532

544

533

499

463-143

146

159

162

166

154128191

207

201

194

180

164-203

221

213

203

183

164

3.5 ng hc ca qu trnh ng haS thy phn tinh bt bng enzyme amylase l mt loi phn ng ha hc, trong enzyme amylase ng vai tr cht xc tc sinh hc, cht tham gia phn ng l tinh bt (i vi c cht), sn phm ca phn ng l cc ng kh v dextrin.

c trng ca phn ng ha hc l vn tc phn ng. Vn tc phn ng l o hm bc 1 ca nng ca mt cht bt k tham gia phn ng (K) hoc cc sn phm cui cng ca phn ng (M) theo thi gian (t). i vi s thy phn tinh bt th nng tinh bt l (K) v sn phm cui cng c to ra l (M) v d maltose ta c:

dK

dMV = - =

dt

dtDu tr biu th cho s gim nng tinh bt theo thi gianTc phn ng t l vi cc thnh tham gia phn ng v nh vy, gim i theo thi gian. C th xc nh vn tc ca s thy phn bng phng php gin tip, t s thay i nng ca tinh bt v s hnh thnh cc sn phm ca phn ng (cc hydratcacbon c tnh kh), hoc theo s thay i tnh cht ha l ca dung dch: gc quay cc, nht, phn ng mu vi iod v nhng ch tiu khc.S tng ln ca tng s cc cht kh trong qu trnh ng ha (tnh theo maltose) thi k u ca s thy phn (t 50%) c th m t bng phng trnh ng hc bc nht:

dM

= k(a M)

dt

Trong ,M: hm lng maltoz

t: thi gian

a: hm lng ban u ca tinh bt (tnh i theo maltose)

K: hng s vn tc phn ng

Sau khi ly tch phn phng trnh trn ta s c:

1 a

K = ln( M = a (1 e-k.t) t (a M)Phn ng ca s thy phn tinh bt l phn ng ca phn t kp, nhng v xy ra trong mi trng d nhiu nc nn tc phn ng biu th bng phng trnh bc nht. V vy, thc t vn tc phn ng t l vi nng ca tinh bt cn hng s vn tc khng ph thuc vo nng ban u ca tinh bt.Khi mc ng ha trn 50% th trt t ng hc ca phn ng b ph v, hng s vn tc phn ng gim xung. iu xy ra do nhiu nguyn nhn. nh hng c bn nht c th do s khc nhau v cu trc cc polyoz ca tinh bt. Thc nghim cho thy rng lc ban u amylopectin b thy phn nhanh hn so vi amylose. iu c th gii thch nh sau: phn t amylopectin c mch nhnh cng knh nn v tr tip xc ca chng vi enzyme amylase nhiu hn. Nhng nu tip tc thy phn th s thy phn i vi amylopectin kh khn hn so vi amylose.Khng phi tt c cc lin kt 1,4 glucozit, nng lng phn ct bng enzyme khng ln, nhng giai on sau i hi mc nng lng phn ct ca enzyme tng ln. Tnh c hiu ca mi loi enzyme khng ging nhau. S km hm phn ng cn c th do c s tranh chp ca enzyme i vi c cht v s km hm ca enzyme do cc sn phm ca phn ng to ra.

Ngoi ra enzyme cn c nhng c tnh bn vng khc nhau i vi nhit , pH mi trng. V vy, trong qu trnh thy phn, enzyme b c ch do nhiu nguyn nhn khc nhau, biu hin r qua vn tc ca s thy phn.

Chng 4: QU TRNH LN MEN RU4.1 Khi qut qu trnh ln men

Ln men l mt qu trnh trao i cht nh tc dng ca cc enzyme tng ng c gi l cc cht xc tc sinh hc. Ty theo sn phm tch t sau khi ln men m ngi ta chia ra lm nhiu kiu ln men khc nhau, hoc da vo s tham gia ca oxy m chia ra thnh 2 loi ln men:

- Ln men hiu kh: l qu trnh phn hy ng vi s c mt ca oxy t do nh cc qu trnh ln men acid acetic, acid citric,

- Ln men ym kh: qu trnh phn hy cc cht hu c phc tp (ch yu l ng) thnh nhng cht n gin, khng c s tham gia ca oxy phn t, nh qu trnh ln men acid lactic, ln men ru etylic,Ln men dch ng ha thuc kiu ln men ym kh, sn phm ch yu l ru etylic nn cn c tn gi khc l qu trnh cn ha, ru ha hoc ln men ru.

Ln men ru, bia u l qu trnh ln men ym kh vi s c mt ca nm men (yeast). Nm men chuyn ha ng ln men thnh ru etylic v CO2. Ngi ta cn c th gi l qu trnh ru ha hay cn ha. Trong qu trnh ln men ru ngi ta chia thnh hai thi k chnh:

+ Thi k pht trin sinh khi: giai on ny vi s c mt ca O2 t bo nm men pht trin sinh khi (gia tng kch thc v s lng)

+ Thi k ln men chuyn ha ng thnh ru v CO2: giai on ny nm men hp th cc cht dinh dng v s dng cc enzyme sn c ca mnh thc hin xc tc sinh ha trong qu trnh trao i cht duy tr s sng to thnh ru v CO2.4.2 C s l lun ca qu trnh ln men ru

4.2.1 C ch ca qu trnh ln men ru

ln men ngi ta phi cho vo dch ng mt lng t bo nm men nht nh. Ty theo phng php ln men khc nhau m lng nm men cho vo khc nhau v di hnh thc khc nhau. Thng thng khi ln men, lng t bo nm men phi t c > 100 triu t bo trong 1ml dch ln men. Do din tch b mt ca t bo nm men rt ln nn kh nng hp th cc cht dinh dng rt mnh. ng ln men v cc cht dinh dng khc trong mi trng ln men trc tin c hp thu trn b mt nm men.Nm men hp th cht ng, cht mu v cc hp cht khc. Cc cht dinh dng b hp th qua b mt t bo ri thm thu vo bn trong. bn trong t bo, cc enzyme s tc dng qua nhiu giai on trung gian cui cng to ra sn phm chnh l ru v kh CO2. Ru etylic to thnh khuch tn ra mi trng bn ngoi qua mng t bo. Do ru ha tan trong nc vi bt k t l no nn khuch tn rt nhanh. CO2 cng ha tan trong nc nhng ha tan khng ln. ha tan ca CO2 trong ru ln gp 3 ln ca CO2 trong nc. Khi bo ha, CO2 bm quanh t bo nm men hoc nhng cht l lng khc hnh thnh nhng bt kh. Bt kh CO2 v t bo nm men thng dnh lin vi nhau. Khi bt kh to n mc nht nh v khi lng ring b so vi khi lng ca t bo nm men th bt kh v t bo nm men cng ni ln trn b mt dung dch. n b mt dung dch, do thay i sc cng ca b mt nn bt kh v tung, CO2 thot ra ngoi, nm men lc ny li chm xung. Qu trnh ny din ra lin tc nn lm cho t bo nm men t trng thi khng chuyn ng sang trng thi chuyn ng trong dung dch ln men, lm tng qu trnh tip xc gia t bo nm men vi c cht, tng nhanh qu trnh ln men. (L Nguyn Bnh, 1997).

Kh CO2 c ch qu trnh ln men, nhng trong qu trnh thot kh CO2 lm gia tng kh nng ln men ca nm men. Kch thc, vt liu ch to ca thit b ln men, cc cht ha tan mang in tch, cc vt l lng khc hin din trong dch ln men khi ln men u nh hng n s thot kh CO2 nn cng nh hng n qu trnh ln men.4.2.2 ng hc ca qu trnh ln menTc ca qu trnh ln men c th quan st c bng cch theo di s thay i ca hm lng ng trong dch ln men, quan st bng cch theo di s thay i lng ru v CO2 to thnh cng nh s thay i tr s ca nng dch ln men.

Qu trnh ln men chia lm 3 thi k chnh:

+ Thi k u: khong 60 gi k t khi cho nm men tip xc vi dch ln men. S ln men xy ra rt chm, ng ln men khng ng k.

+ Thi k 2: y l thi k ln men chnh. Chim khong 60-120 gi sau thi k u s pht trin ca nm men v s ln men sau mi gi tng nhanh ng k v t n tr s cc i.

+ Thi k cui: y l giai on ln men ph xy ra rt chm ng thi l thi k n nh to mi cho sn phm. Ty theo phng php ln men, loi sn phm m thi gian ln men ph ko di khc nhau khng quan st c.

Thi k ln men chnh l thi k bin i su sc cc thnh phn trong dch ln men chng nh hng ti kt qu ca qu trnh ln men. Trong giai on ny, trong iu kin ln men bnh thng sau mi gi nng ng trong dch ln men s gim i khong 1 (Brix, %) ty loi sn phm, dy chuyn sn xut.

S tn ti ca thi k ln men cui l c trng i vi qu trnh ln men dch ng ha t nguyn liu cha tinh bt.

Trong dch ln men nu biu th hm lng ng tn ti trong dch ln men l 100% th 4 6% l dng cht khng tan, 75 77% c chuyn thnh maltose v 19% l dextrin.

Trong giai on ln men s ng ha cng xy ra nhng rt chm v khng hon ton, c bit kh khn i vi tinh bt khng ha tan. Do tc ln men trong thi k ny khng ph thuc vo s lng t bo nm men m ch yu l ph thuc vo s thy phn hm lng dextrin khng ln men cn li. Tuy vy, chnh nhng loi ng khng ln men ny s to thnh v ngt cho sn phm. Nh vy, chu k ln men dch ng ha tinh bt ph thuc vo thi gian ln men cui hay ph thuc vo kh nng ng ha ca phc h enzyme amylase. Rt nhiu th nghim cho thy rng cng ko di thi gian ln men cui th cng gia tng hiu sut ca qu trnh ln men.

Tuy vy, ty theo sn phm ca s ln men, nng glucid ca dch ng ha, phng php ln men, nh sn xut cng s to ra mt qui trnh sn xut ring bit vi cht lng v thnh phn mong mun ca h.

giHnh 4.1 th biu din s thay i nng ng ln men theo cc thi k ca qu trnh ln men4.3 Cc yu t nh hng n qu trnh ln menMi hot ng sng ca vi sinh vt ni chung, ca nm men ni ring, lin h mt thit vi ngoi cnh. Mi yu t ca ngoi cnh c ba mc nh hng khc nhau n hot ng sng ca nm men.

- im cc tiu: l iu kin ti thiu nm men tn ti. iu kin ny bt u xut hin cc hot ng sng.

- im cc thch (ti u): l iu kin tt nht cho hot ng sng. Nm men c cng hot ng mnh nht.

- im cc i: l iu kin ti a v l gii hn trn tn ti ca hot ng sng. Qu gii hn ny nm men s cht.

Do vy, vn quan trng l phi iu chnh iu kin ngoi cnh sao cho t c gii hn ti u.

+ nh hng ca cc yu t bn trong- Ngun gluxit: L ngun nng lng cn cho cc vi sinh vt khc do s phn hy cc hp cht cao nng thnh cc hp cht thp nng (ngun nng lng ca s trao i cht).

- Phosphat v c: Phosphat c vai tr quan trng trong qu trnh chuyn nng lng ca h thng sinh hc. Phosphat thng uc a vo mi trng di dng kali phosphat hoc amon phosphat. Nng phosphat thng x dch t 0,1 0,5%.- Nit: Nit l hp phn c bit ca protein, acid nucleic v phn ln cc hp cht phc tp ca cht sng. Nhiu vi sinh vt c th ng ha nit di dng ion amoni, mt s di dng nitrat, cn a s i hi hp cht nit c ngun gc sinh hc.

- Cc nguyn t vi lng: Ngoi cc nguyn t trn, cc nguyn t vi lung cng rt cn thit. Cc nguyn t vi lung thng gp l: Mn, Mo, Zn, Cu, Co, Ni, Vd, B, Cl2, Na, Si. Ngoi cc nguyn t vi lng v c cc nguyn t vi lng hu c cng rt quan trng.

- Vitamin: Nhng cht sinh trng hay nhng yu t sinh trng u c lin quan n cc vitamin nhm B, nh B1, B2, pan-totenic, PP, B6, biotin.

- nh hng ca nhit :Nhit lm vic c nh hng n vi sinh vt v cc qu trnh trao i cht ca chng.Nhit cn ng vai tr trong cc qu trnh sinh tng hp.- nh hng ca pH:Cc vi sinh vt c vn tc sinh trng cc i trong mt khong pH hn ch v cng b v hot hon ton hoc b cht pH hn ch.- Vi sinh vt: L tc nhn ch yu gy ln men.

+ nh hng ca yu t mi trng

- Nhit

Nhit c nh hng r rt n hot ng sng ca nm men, c th l nm men saccharomyces cerevisiae Rasse XII trong qu trnh ln men ru. Nm men chng XII pht trin tt nht nhit 30-33C , nhit ti a 38C, ti thiu l 5C. Nm men c nui cy nhit thp hn nhit ti u, thng 17- 22C c hot lc ln men rt ln. i vi qu trnh ln men th nm men s chu c nhit kh rng t 1- 45C, nu nhit qu 50C th nm men s cht.

- Acid (pH)

Nm men c th pht trin trong mi trng pH t 2-8 nhng thch hp nht l 4- 4,5. Vi khun bt u pht trin pH= 4, 2 v cao hn, khi thp hn mc ny ch c nm men c th pht trin c v vy trong qu trnh ln men ru nn thc hin pH=3,8- 4,0. Tuy nhin c nhng loi vi khun do quen dn (thun ha) vi pH thp nn ngoi vic ng dng iu chnh pH thch hp cn phi kt hp s dng cc cht st trng. Khi pH=8 th nm men pht trin rt km, ngc li vi khun pht trin rt mnh. pH=3,8 nm men pht trin mnh th hu nh vi khun cha pht trin.

to pH thch hp trong mi trng nui cy nm men (k c ln men) ngi ta c th b sung vo mi trng ln men bt c mt loi acid no, min l anion ca acid khng gy nh hng mnh m n trung tm hot ng ca nm men.

- Nng ru

Qu trnh nui cy nm men ch yu l to mi trng thch hp cho nm men pht trin sinh khi, t s lng theo yu cu. Song nm men cng thc hin mt qu trnh ln men ru ng k (cn ph thuc vo khng kh).

Thng trong dch nm men c khong 4-6 % ru. Nng ru sinh ra c nh hng n tc v kh nng pht trin ca nm men. iu ny cn ph thuc vo thi gian mi trng nui cy, s lng t bo nm men cho vo bng nhau, iu kin nui cy ging nhau th nng ru ban u 1 % c nh hng n tc v kh nng pht trin ca nm men t 4-6 % c nh hng xu.

- S lng t bo nm men

S lng t bo nm men cho vo dch ln men nh hng rt ln n qu trnh ln men. Nu s lng t bo nm men cho vo thch hp th qu trnh ln men din ra tt v hiu sut thu hi cao, cht lng sn phm cng tt hn. Nu lng t bo nm men cho vo qu t th tc ln men chm, sinh khi t bo nm men thp to iu kin thun li cho vi sinh vt pht trin, s lng t bo nm men qu nhiu th mi trng dch ln men khng cho nm men pht trin, t bo nm men s cht dn sn phm sinh ra mi l, v l ng thi ph i mt lng ng k men khng c t.

- nh hng ca vic thng khng kh v o trn

Oxy l thnh phn khng th thiu c giai on pht trin sinh khi. Tuy nhin n li l nguyn nhn gy h hng cho ru, bia trong cc giai on ch bin cn li. Vi s c mt ca CO2 nm men s khng ln men hon ton v chng s tip tc pht trin sinh khi. Trong gia on bo qun th chng s lm cho sn phm c nhiu aldehyde, sn phm rt d b bin mu do cc phn ng oxy ha, phn ng ha nu gy ti mu cho sn phm, lm chua sn phm do s hnh thnh cc acid hu c (do ru, bia l mi trng rt dinh dng thch hp cho s pht trin ca nhiu vi sinh vt gy thi).

Mt s qu trnh ln men trong giai on u din ra qu chm do khng lng O2 cho s pht trin sinh khi, do vy khng s lng t bo ln men nh hng n cht lng sn phm v dy chuyn sn xut. Tuy nhin li c mt s chng nm men pht trin nhanh v to ra hm lng ru nhiu hn trong mi trng thng kh, chng ny thng nui cy v pht trin trong mi trng ban u c y O2.Ty theo sn phm m nh sn xut qui nh hm lng O2 ti a c th c trong sn phm cui. V d, bia chai thng thng hm lng O2 < 0,01ppm. O2 l thnh phn c kim sot ht sc cht ch trong cc giai on ca qu trnh sn xut.

Thng khng kh tc l cung cp oxy cho qu trnh h hp ca nm men. Vic thng khng kh kt hp vi vic o trn c nh hng r rt n qu trnh sinh trng v pht trin ca nm men. Thiu khng kh, tc l iu kin ym kh, nm men s thc hin qu trnh ln men ru, nng ru trong mi trng tng ln nhanh chng, khi s pht trin ca nm men dn dn s b kim hm.Vic thng kh v o trn cn c tc dng lm cho mi trng lun trng thi ng, tng cng s tip xc gia t bo nm men vi mi trng dinh dng, do rt ngn c thi gian nui cy. Trong thc t sn xut, nu thng khng kh y c th rt ngn 1/3 thi gian nui cy so vi iu kin thiu khng kh.Mc d qu trnh ln men ruu l mt qu trnh ln men ym kh, nhng khi ln men nht thit trong giai on u phi cho dch ln men tip xc vi oxy khng kh cho nm men sinh trng v pht trin (tng s lng). Tuy nhin oxy ch c t trong giai on u, khi s lng t bo nm men tng n mc thch hp th phi ngn cn dch ln men tip xc vi oxy khng kh nm men c th chuyn ha ng c trong mi trng thnh sn phm ru .

- Cht st trng

Cc cht st trng c trong sn xut nh: formol, Na2SiF6, NaF, CaOCl2, Cc mui kim loi nng, cc tia cc tm iu c nh hng rt ln n hot ng ca nm men. Tuy nhin, mi mt yu t (hay mi cht ha hc) c nh hng khc nhau trong tng iu kin nui cy v tng chng nm men khc nhau.

4.4 Sn phm ph trong qu trnh ln menTrong qu trnh ln men ngoi sn phm chnh l ethanol v CO2 cn to ra nhiu cht khc. Bng phng php phn tch sc k ngi ta pht hin ra trn 50 cht khc nhau, nhng c th xp thnh 4 nhm chnh: acid, este, aldehyde v alcol cao phn t.

S to thnh acid

Trong qu trnh ln men ru lun lun c s to thnh cc acid hu c: acetic, lactic, citric, pyruvic v succinic nhng nhiu nht l acetic v lactic.

+ Acid acetic c th c to thnh t phn ng oxy ha kh gia hai aldehyd acetic:

CH3CHO+CH3CHO+H2O=CH3COOH+C2H5OH

Acid lactic c to thnh bi pyruvat dehydronase theo phn ng:

CH3CO - COOH+NAD.H2=CH3CHOHCOOH+NAD

Hoc

CH2O(H2PO3)CHOHCHO + H2O= CH3CHOHCOOH + H3PO4Glycerin v aldehyde u l sn phm trung gian ca s ln men ru ( trnh by phn din bin qu trnh ln men).

S to thnh alcol cao phn t

Mt trong nhng sn phm ph quan trng c to thnh trong qu trnh ln men ru, l cc ru c s nguyn t carbon ln hn hai. Cc ru ny tuy t nhng nu c ln vo sn phm s gy nh hng xu ti cht lng sn phm. l cc ru propylic, izobutylic,Hm lng ca chng ch chim khong 0,4-0,5% so vi cn etylic nhng gy cho sn phm c mi hi kh chu.

Nhiu nh nghin cu cho rng, s to thnh alcol cao phn t ch ph thuc vo cu trc v hm lng acid amin c trong dch ln men. Theo gio s Vexelop, vic to thnh alcol cao phn t xut hin ch yu trong giai on sinh trng ca nm men. Trong gii hn pH t 3,0-5,0, alcol cao phn t tch t trong dch ln men s nhiu hn, nhng nu tip tc tng pH th hm lng alcol cao phn t s gim. Sc kh vo dch ln men s lm tng s to thnh alcol cao phn t (Nguyn nh Thng, 2000).

S to thnh este

Song song vi vic to acid v ru, di tc dng c enzyme esterase ca nm men, cc acid v ru s tc dng ln nhau d to ra nhng este tng ng:

R1CH2OH+R2COOH

R2COO CH2R1+H2O

S to thnh este s xy ra d hn khi cu t tham gia phn ng l cc aldehyde:

R1CHO+R2CHO

R1COO-CH2R22.8.2 Cc dng h hng thng gp trong qu trnh ln men

Ln men lactic:

Vi khun lactic nhim vo thng s ln men to thnh acid lactic lm cho acid trong dch ln men tng tng ln, gy c ch hot ng ca nm men.

C6H12O6

2CH3CHOHCOOH

glucose

acid lactic

Ln men butyric:

Vi khun butyric khi nhim vo thng s gy ln men butytic, to ra nhiu kh hidro, tuy nhin acid khng cao.

C6H12O6

CH3CH2CH2COOH +2CO2 +2H2 Ln men di

Thng gp cc loi nm men hnh oval ln, ln men rt nhanh, to acid cao v ru ln, lm c ch hot ng ca nm men nh.4.5 Cc phng php ln men4.5.1 Phng php ln men gin on

y l phng php thng c s dng nht cc nh my ru bia. c im ca phng php ny l sut c qa trnh ln men t u n cui c thc hin trn cng mt thit b ln men.Trc khi s dng, thng ln men c v sinh sch s, kh trng bng hi nng v cht st trng. Nu dng formol st trng th t l l 0,03 0,05% th tch. Ty vo loi sn phm, phng php ln men, yu cu v v sinh t ra nh my m c phng php v sinh khc nhau. Cng on ny l mt trong nhng cng on quan trng nht nh hng trc tip n cht lng sn phm. Trong phng php ny th t dch ng ha v nm men cho vo thit b ln men l khng quan trng. giai on u ca s ln men, vic thng kh cung cp O2 cho nm men pht trin sinh khi l quan trng nhng khng kh phi c x l tit trng trc khi s dng, nu khng thit b ln men s b nhim vi sinh vt l. Thm vo do sut qu trnh ln men ch s dng mt thit b nn cn tnh ton lng O2 tht chnh xc va cho chng pht trin sinh khi, sao cho khi lng t bo nm men va s lng th ht O2 nm men chuyn sang giai on ln men ngay.Trong sut qu trnh ln men, c bit giai on ln men chnh, nhit dch ln men lun tng dn do vy phi s dng h thng lm mt khi dch ln men trong sut thi gian ln men (dng nc ti hay gin lnh).

pH dch ln men gim dn trong sut qu trnh ln men. Trng hp ln men bnh thng, pH s gim trong khong 0,2 0,3 so vi ban u. Nu c s thay i pH qu t ngt th s ln men ny khng bnh thng phi kim tra ngay ton b h thng ln men (nhim bn thit b, r r, nc s dng, nguyn liu,) c bin php x l kp thi.

+ u im v khuyt im:

Thao tc n gin

Nu c s c ln men khng bnh thng do nhim bn, nm men km pht trin, pH tng nhanh) th ch h hng trn mt thit b m thi khng nh hng n thit b ln men khc

Chu k ln men ko di do phi c nhiu thit b ln men.

Hiu sut ln men khng cao v khng n nh.

Tn nhiu nng lng (hi, nhit), mi thit b ln men u phi c thit b khuy trn, gin lnh hay h thng lm ngui, ng dn ring. S lng thit b nhn ging nm men cng nhiu hn.

4.5.2 Phng php ln men bn lin tc (phng php chu k)

y l phng php ln men m giai on ln men chnh thc hin lin tc, giai on ln men ph thc hin gin on.

Hnh 4.1: s h thng ln men theo phng php bn lin tc (pp chu k)Bt u chu k th nht c tin hnh nh sau:

Nm men nguyn chng thng (1) cho xung thng ln men th (2) vi t l 8 10% (hoc c th ln hn), tip chuyn dch ng ha y thng, khi y thng, sang i qua thng ln men th (2) v tip tc chuyn dch ng ha vo ng thi c hai thng. Nh vy, hai thng ln men u coi nh va lm nhim v pht trin nm men va thc hin ln men chnh.

Khi c hai thng y, m van cho dch ln men t chy sang thng ln men th 3, c nh th n thng th 7, th 8, khng ch thi gian sao cho n khi y thng th 8 t 60 62 gi ln men. Gi cc thng tip tc ln men cui mt thi gian na cho n khi t tiu chun dm chn, a i ct ru. Tun t cho ct ru t thng th 8 ri th 7, th 6,Trc khi ct ru, thu hi lng nm men thng th 8 a v thng (1), x l bng acid ri tip tc pht trin, dng cho chu k tip. Cng c trng hp khi ln men bnh thng, ngi ta s dng ngay nm men ca thng ln men th 1 (2) a ln thng gy men (1), tip thm mi trng dinh dng pht trin theo yu cu sn xut. Vic s dng li nm men phi rt thn trng, kim tra xem xt kp thi v khng dng li qu 5 ln.Sau khi bm ht dm chn thng th 8 i ct ru (thng c b tr h thng bm chuyn sang 1 thng d tr dm chn), tin hnh lm v sinh, st trng thng th 8. Chu k ln men ln th 2 li bt u ln men t thng s (8), qu trnh din ra ngc li vi chu k trc.Theo kt qu nghin cu th vi phng php chu k, thi gian lu li ca dch ln men trong mi thng khng ging nhau. Thi gian lu li cc thng u rt ngn v lng dch ng ha chuyn vo nhiu, cc thng mi, dch ln men chy vo vi tc chm hn.

cc thng u, do c lng nm men rt ln nn coi nh khng c giai on ln men u v ngay c giai on ln men chnh cng xy ra rt nhanh, kt thc giai on ln men chnh thng th 2. Nu ln men trong h thng 6 thng, thng th nht ln men gn 64%, thng th 2 23% v cc thng ln men cui 13% lng ng trong dch ln men.

Phng php ln men chu k c u im l n gin, rt ngn c chu k ln men, bo m thi gian ln men cui, nn nng cao c hiu sut ln men.

4.5.3 Phng php ln men lin tc

Bn cht ca phng php ln men lin tc l ri u cc giai on ln men, m mi giai on c thc hin trong mt hay nhiu thit b ln men c lin h vi nhau.

Hnh: s h thng thit b ln men lin tc dch ng ha t tinh bt

1. Thng pht trin nm men nh

2. Thng pht trin nm men ln

3. Thng ln men u dy (3a, 3b)

4. Thng ln men tip tc

5. Bm chuyn thng u dy

6. Bm chuyn thng ln men tip theo

7. Thit b thu hi cn trong CO2.

Qu trnh ln men lin tc c thc hin nh sau:H thng thng ln men lin tc thng t 11 12 thng, c ni vi nhau bng cc ng chy chuyn 150 200, c van iu chnh. Th tch thng ph thuc vo nng sut nh my. Hai thng u ca dy thng ln men lin tc (3a, 3b) c gi l thng u dy, c chiu cao thng cao hn cc thng ln men tip tc 4 (1), 4 (2),4 (12) khong 0,5 0,7m. S d 2 thng u dy phi cao hn v: Giai on ln men chnh c thc hin ti 2 thng ny. Lng CO2 thot ra nhiu nht. Hin tng to bt trn b mt dung dch ln men nhiu, nht l i vi trng hp ln men dch ng ha t tinh bt c dnh ln, khi lp bt cng cao.

m bo cho dch ln men t chy d dng t thng u dy n thng cui dy. chnh lch chiu cao ny thng phi t 0,4 0,6m. Nh vy, h s s dng cc thng ln men tip vn m bo.

Trn cc thit b v h thng ng dn u c ng nc sch v hi nhit v sinh v st trng thun tin nht. Trong ln men, ngay thng u dy, u khng s dng khng kh nn.

Sau khi v sinh st trng v kim tra k thit b, h thng ng dn, ngi ta cho nm men nguyn chng thng (2) xung thng ln men u dy (3a), tip bm u n dch ng ha n y thng. C th thc hin bng hai cch:

a. Sang i thng 3a sang thng 3b. Sau bm tip dch ng ha vo ng thi c hai thng n y. Khi thng 3b y, m van ng ng chy chuyn cho dch ln men t chy sang thng ln men 4 (1), ng thi m van ng ng chy trn t thng 3a sang thng 3b. Tip tc bm u n dch ng ha vo c hai thng. Nh vy coi nh c 2 thng pht trin nm men v ln men chnh. Dch ln men c tip tc chy trn t thng 4 (1) sang 4 (2)cho n thng 4 (10) hoc 4 (11) th kt thc qu trnh ln men. Dm chn chuyn sang b phn chng ct.b. Khi thng 3a y, m van ng chy chuyn t 3a sang thng 4 (1), khng qua 3b. Khi 4 (1) y, m van ng chy chuyn sang thng 4 (2), c nh th cho n thng cui cng, kt thc ln men. Dch ng ha ch bm vo thng 3a, thng 3b gi vai tr thng d tr thay th.

Cc thng s k thut ca dy chuyn ln men

Thng ln menNhit (oC)Nng dch ln men (os) acid ()pHLng t bo nm men (triu/ml)

3a3b

4(1)

4(2)

4(3)

4(4)

4(5)

4(6)

4(7)

4(8)

4(9)

4(10)29-3233-34

32-33

30

30

30

30

30

30

30

30

304,5-8,05,0-7,0

3,0-5,0

2,0-2,8

1,7-2,0

1,3-1,7

1,0-1,3

0,8-1,1

0,8-1,0

0,8-1,0

0,7-0,8

0,5-0,70,45-0,500,40-0,45

0,40-0,45

0,45-0,50

0,5

0,5

0,5

0,5

0,5

0,5

0,5

0,54,2-4.34,3-4,4

4,3-4,4

4,3-4,4

4,3-4,4

4,3-4,4

4,3-4,4

4,3-4,4

4,3-4,4

4,3-4,4

4,3-4,4

4,3-4,445-5545-60

60-70

60-70

60-70

60-70

60-70

60-70

60-70

60-70

60-70

60-70

Thi gian ln men tng cng t khong 62-68 giDm chn thng t cc ch tiu sau:

Nng ln men: 0,6-1,5os (ph thuc vo loi nguyn liu v nng ln men ban u) acid 0,45 0,6 (tng hn so vi ban u 0,1o Kh nng ng ha (lng enzyme amylase trong dch ln men): 1,0 1,55 n v/ml

Cht kh tng s (ch yu l ng kh): 0,15 0,3g/100ml

Nng ru: 8 9%.

4.6 Cc ch tiu cng ngh ln men ru4.6.1 Nng dch ln men

Nng dch ln men c biu th bng nng biu kin v nng thc. Thng ngi ta hay s dng nng biu kin. Nng biu kin c xc nh bng cch o trc tip dch ng ha hoc dch ln men ( qua lc sch) bng ph k saccharomet (hoc brix k, baume k, balling,).

1 saccharomet, vit tt 1os, tng ng 1% ng sacharose trong dung dch. V vy, ngi ta dng n v saccharomet lm n v xc nh nng biu kin.Nng biu kin ph thuc vo hm lng cht kh trong dung dch v hm lng cc sn phm ca dm chn. Khi hm lng cht kh thp, cc tp cht khc nhiu hn th nng biu kin thng ln hn khng, c gi tr dng. Ngc li, hm lng cht kh cao, ln men trit , hm lng ru nhiu th nng biu kin c th t tr s m.Nng thc ca dch dm chn c xc nh bng cch lc v chng ct ui ht cc cht bay hi. Do , nng thc bao gi cng ln hn nng biu kin.

Hm lng cht kh ha tan trong dung dch ph thuc vo tnh cht ca nguyn liu, vo phng php nu, phng php ng ha, thi gian ln men v nhit ln men. V vy, nng dch ln men, ngay c khi ng ln men hon ton, vn cho gi tr khc nhau. Thc t cho thy rng, khi thay i nng cht tan trong dung dch (tng hoc gim) 1%, tng ng vi s tng hoc gim nng dch ln men biu kin trong dm chn 0,2%.Mc d nng dch ln men biu kin thay i ph thuc vo nhiu yu t, nhng trong thc t sn xut, vi nguyn liu sn xut tng i n nh, vic xc nh nng biu kin c th gip ta bit c qu trnh ln men c bnh thng hay khng. Qua thc t sn xut, khi ln men bnh thng th nng dch ln men biu kin ca dm chn i vi tng loi nguyn liu nh sau: Ht ng: 0 0,2os Ng bt: 0,5 1os Tm ng: 0 0,5os Sn: 0 1os Bt m: 1,5 1,8os4.6.2 acid

Trong qu trnh ln men, nu ch do hot ng sng ca nm men th acid ch tng ln khong 0,2% so vi ban u. Nu acid tng hn 0,2% l do c s pht trin ca cc loi vi khun khc hin tng nhim khun, thng gp l vi khun lactic. Nng ru trong dch ln men 3 -5%v rt thch hp cho vi khun lactic pht trin, nng cao hn c tc dng c ch. Khi nhim khun lactic, acid tng nhanh. acid tng lin quan n s hao tn ng to ra acid, ng thi c ch hot tnh ca enzyme, nht l amylase. Khi aicd trn 1o th kh nng ng ha nh ch, to ra nhiu dextrin. aicd tng 0,2%, tng ng s tn tht 0,6% ng. S lin quan gia acid, pH v hot tnh ca amylase c biu th bng. acid ()0,30,50,60,750,80,91,11,42,02,1

pH4,64,54,54,54,34,34,03,93,93,7

Hot tnh ca amylase+++++-----

Mc d acid thay i nhiu, nhng pH thay i khng ln. iu ph thuc vo nng [H+] trong dung dch.Hm lng acid tng 2g/lt c xem l c hin tng nhim khun.4.6.3 Nng ru

Nng ru trong dm chn thng c khng ch trong khong 8 -9%v. Nu cao qu, i hi nng dch ln men cao, thi gian ln men di, ln men khng trit , hiu sut ln men thp. Nhng nu nng ru trong dm chn thp (6%v), thi gian ln men c th b rt ngn, hiu sut ln men c th m bo nhng c nhiu iu khng li:

D b nhim khun

Gim nng sut thit b (nu, ng ha, ln men v chng ct). Tn nhiu nng lng cng on chng luyn. Cng vi s lng thit b, nhng nu tng nng cn trong dm chn ln 1%, c th nng nng sut ca nh my ln gn 20% v tit kim hi nhit gn 10% cng on chng luyn.Chng 5: CNG NGH SN XUT BIA

5.1 K thut nuTrong sn xut bia, qu trnh nu bao gm mt s cng on sau:

+ lm sch v xay malt

+ Xay nguyn liu ph

+ Thy phn protein v ng ha tinh bt trong malt, trong nguyn liu ph

+ Lc dung dch trch ly

+ un si dung dch vi hoa houblon

+ Lm trong v lm lnh nc nha.

5.1.1 X l nguyn liu (malt, ng cc)

Trc khi au vo sn xut, malt c lm sch v nghin nh. Mc ch chnh ca vic nghin nh malt l to iu kin tng tc qu trnh l hc v ha sinh hc trong khi ha thm ht vo nc, bo m ti a cc cht trch ly chuyn t ht vo dung dch.

Mc nghin nh ca malt, go c vai tr quan trng, v ht cng c nghin nh th din tch chu enzyme cng ln. Tuy nhin vic nghin nh phi c k thut.Chng hn, ht malt gm hai phn: v xellulose v ni nh. Hai phn ny c tnh cht l ha hc rt khc nhau, c bit tnh cng ngh hc th cng khc nhau hn. Thnh phn ca v ch yu l xellulose, lignin, tannin v tro. Xellulose khng ha tan trong nc, cn cc cht nh tannin, cht ng, tro th ha tan vo dung dch, to v v mu khng bnh thng cho nc nha, gy nh hng xu n cht lng sn phm. Do vy, khi nghin malt l ch gi cho phn v xellulose cng nguyn vn cng tt. Phn ni nh th ngc li, cng nghin nh cng tt. Khi kch thc cc ht cng b, cc enzyme phn hy d dng v chuyn thnh dng ha tan trong nc mt cch trit . Tuy nhin, mc nghin nh cn ph thuc vo thit b lc. Nu nghin qu nh cc ht ni nh s lm bt kn cc l lc gy cn tr cho qu trnh lc.

Nu lc bng thit b lc khung bn, t l cc dng hnh trong ht malt nghin nh sau: v tru 9 12%, tm ln 12 15%, tm b 30 35%, bt 40 45%. Cn s dng thit b lc thng thng th v tru 15 18%, tm ln 18 22%, tm b 30 35%, bt 25 35%.5.1.2 Qa trnh thy phnNhim v ca qu trnh thy phn l chuyn ha cc thnh phn chnh ca malt v nguyn liu thay th (go, bt m, bt ng) thnh nhng cht ha tan trong nc, quan trng nht l cc loi ng v cc acid amin.

5.1.2.1 Th no l mt qu trnh ng ha (chng 4)

5.1.2.2 H enzyme amylase trong qu trnh ng ha (chng 4)

5.1.3 Qu trnh ng ha tinh bt thnh ng ln men (chng 4)

5.1.4 Phng php nu

C nhiu phng php nu nh phng php phn on v phng php ton khi. Nhng t c hiu sut ng ha cao, phng php phn on thng c s dng.

gim gi thnh sn phm, a s cc c s sn xut bia nc ta u s dng t l nguyn liu nh sau: 70% malt i mch v 30% go. i vi vic p dng t l nguyn liu ny phng php nu thng c tin hnh nh sau: Ni nu go: Trc ht cho nc vo ni nu, tng nhit nc n 40 50oC ri tt c bt go vo, va va khuy cho bt go tan u trong nc. y l nguyn liu khng cha enzyme cho nn cn phi b sung 10% tng lng malt i mch d kin dng cho m nu. Sau khi hn hp c trn u, tng t t nhit hn hp ln n 50 52oC, gi hn hp nhit ny khong 20 pht. Sau , tip tc tng nhit hn hp mt cch t t, tt nht l c mi pht tng 1oC cho n 70oC th gi hn hp nhit trong 30 pht. Ri un si hn hp 30 pht h ha hon ton tinh bt. Sau cho nc lnh vo gim nhit xung 55oC. Ni nu malt: tng t nh ni nu go, nc cng c bm vo ni nu, sau cho tt c lng malt cn li vo, khuy u v thy phn nhit 50 52oC, y l giai on thy phn protein. Gi giai on ny khong 30 pht.

Sau khi ni nu go t yu cu, bm tt c hn hp t ni nu malt sang ni nu go. Ton b hn hp ny c tng nhit ln n 63oC v gi nhit ny khong 30 pht to maltose. Cui cng l nng ln n 72oC, duy tr nhit ny cho n ng ha hon ton trong khong 30 40 pht.Sau khi kt thc ng ha c th tin hnh lc dung dch trch ly. My lc thng dng l my lc khung bn.

5.1.5 Lc nc nha v nu hoa houblon5.1.5.1 Lc nc nha

- Mc ch: tch cc phn t khng tan v cc phn kt ta trong qu trnh un si ra khi dch ng.

+ Vic lc trong thng c tin hin trn cc my lc p, ni lc hay thng lc. Da trn hai nguyn l c bn: l hc v hp ph.

+ Qu trnh lc gm c lc cho v ra b cho. Nng cht tan trong dung dch sau khi hon tt qu trnh lc l 10 11 o balling+ Tc lc ph thuc vo mc nghin malt, mc phn hy ca malt, cu to mng lc v cc yu t khc nh: bt tr lc, nht dch lc, p sut lcNgoi lp nguyn liu lc, b ca malt m c bit l v malt hnh thnh mt lp tr lc rt hu ch.+ Nhit thch hp cho qu trnh lc l 70 75oC, tng ng vi pH thch hp = 5,5, nc ra b cho php ti a la 78oC. Cc thit b lc

+ Thng lc

+ My p lc khung bn

Cho malt i vo trong cc khung xp xen k vi cc bn lc. Gia khung v bn lc c ngn cch bng vt liu lc nh: vi lc, giy hay bt lc.

Dch trong i qua nguyn liu lc chy theo cc rnh trn mt bn lc, vo ng ng tp trung a v thng cha.

B cho b gi li trong khung, dn cha y khung v to thnh mt lp nguyn liu lc ph. Trng hp ny v malt c vai tr quan trng lm xp lp nguyn liu lc.

Tin hnh lc: Cho nc c nhit khong 76 80oC i vo my lc khung bn. sau tho nc v bm cho vo khong trng trong cc khung lc. Nng p sut lc tng ln khong 0,2 0,3at. Khi cho y cc khung tin hnh ly dch trong ra. Khi dch ng trong ra ht, dng nc 76oC ra b (p sut p< 1at (0,5 0,6 at) v nu nc c nhit cao hn nc nha s b c lm nh hng n cht lng ca bia.

Khi ra xong tho khung v bn ri nhau ly b v vi lc ra. Vi lc c git sch dng cho me lc sau.

Tng thi gian lc trung bnh khong 2 gi 30 pht, trong thi gian ra b l 1 gi 30 pht. Nc nha u v cui s c trn ln vo nhau, balling t t 12 16 o. Yu cu nc nha phi trong sut, v nu c nhng ht nh khng ha tan trong nc nha s to nn v kh chu cho bia v c th gy tr ngi cho vic lc bia sau ny.

5.1.5.2 Nu hoa houblon

Tt c nc nha u v nc nha cui c bm vo ni nu hoa houblon. khu ny, nc nha cn c nng nhit nhanh v si mnh. Mc ch:

Chit cc cht ng cn thit ca hoa houblon to hng v cho bia.

To iu kin cho s hnh thnh ta gia cc protit km bn vng vi tanin

Tiu dit cc enzyme xc tc sinh hc

Kh trng dch ln men

Lm bay hi mt phn nc ca dch ln men.

Ngoi ra, un si dch ng vi hoa houblon gp phn gia tng mu, acid, to thnh cc cht kh, gim nht, tng bn sinh hc, nh hng ti kh nng to v gi bt cho bia thnh phm.

Trong lc un si hoa houblon, nhiu qu trnh l ha xy ra. l s ha tan cc cu t c trng ca hoa, s ha tan cc cht melanoid, cc cht caramen. S ha tan cc cht ng lm thay i v ca nc nha t ch ch c v ngt tr thnh va ngt, va ng. Du ca hoa houblon c nh hng n mi thm ca nc nha, mt phn cc pha ca du houblon chuyn ha thnh cc cht khng bay hi v c gi li trong nc nha nh l mt yu t sinh hng.S ng t protein xy ra trong qu trnh un si hoa houblon rt quan trng. Qu trnh ny xy ra theo hai bc:

+ Ph hy cu trc ca phn t protein

+ ng t

S c mt ca protein trong nc nha un si vi hoa houblon c th lm cho sn phm b c v lm gim bn sinh hc ca bia. S hnh thnh cn: dch ng l h thng keo nhiu lp a phn dng ha tan, khi nhit tng cc keo km bn vng b ph v, cc phn t keo dnh li vi nhau xy ra hin tng keo t.c bit cc cht tannin ca houblon v cc protit km bn rt d hnh thnh cc cht hp ph, to iu kin cho keo t to thnh cn.

Khong 20% cht ng ca hoa c trong dch ng (khong 29% thi ra ngoi theo b, 50% ta vi protein v mt phn hao ph theo bt). Nhit v thi gian un si dch ng vi hoa houblon. un si l qu trnh kh trng cho dch ng trc khi ln men, nhit un si l 100oC, thi gian un si l 1,5 2 gi, pH = 5,2 5,5.

Dc ng l mt h oxy ha kh phc tp, khi un si s lm thay i th oxy ha kh c li cho vic ln men bia sau ny.

Khi un si, ph hy ton b cc enzyme thy phn, chm dt vai tr xc tc ca chng cho qu trnh ln men bia ng theo yu cu k thut.

Ngoi ra, qu trnh un si hoa houblon cn lm cho mu sc ca nc nha thay i t nht sang m v hin tng caramen ha cc ng, s hnh thnh cc cht melanoid v v cc cht mu ca hoa houblon chuyn t trong hoa vo dch.

Lng hoa houblon dng trong sn xut bia nhiu hay t cn ty thuc vo th hiu ca ngi tiu dng. Thng t 1 2 gam hoa cho 1 lt nc nha.

5.1.6 Lm lnh v lng trongTrong nc nha nng khng c oxy ha tan, m ch c cn bn sinh ra trong qu trnh un si hoa. Cc cn bn s nh hng xu n ton b cng ngh tip theo l ln men chnh, ln men ph, lc v bo qun bia.

5.1.7 B sung oxy cho dch ng- Mc ch: oxy hu nh b loi ht trong qu trnh ch bin dch ng nn phi np oxy cho dch ng c lng oxy cn thit cho t bo nm men sng v pht trin, c bit trong qu trnh sinh sn giai on u ca qu trnh ln men bia.

- Phng php: c hia phng php:

+ B sung oxy dng khng kh v trng t my nn. i vi oxy dng kh nn c b sung ngay trn ng ng dn dch ng (xui chiu) hay trc tip vo thng ln men.

+ B sung oxy cc bnh oxy th n c phn b qua mt b phn c bit v theo ngc chiu vi dng chy dch ng trn ng dn.

Vic b sung oxy c kim tra v iu chnh bng ng h o lu lng trung bnh, thng cn 35 ml khng kh/ 1 lt dch ng hoc 5 8 mg/lt.

5.2 K thut n men bia.

5.2.1 Ln men chnh

5.2.1.1 Nhng yu t nh hng ti tin trnh ln men chnh

+ Tc pht trin sinh khi+ Tc hp th c cht

+ Mc hp th c cht (mc ln men)

+ Nng cc sn phm chnh v sn phm bc hai to thnh trong qu trnh ln men.

a. Cht lng nm men sn xut

Tc v mc ln men

Hm lng sn phm bc hai to thnh, hm lng sn phm bc hai thp th bia c cht lng cao

Tc v kh nng kt lng

Mc thoi ha

Kh nng chng chu khi b tn cng

b. Lng nm men gieo cy ban u

Thi gian thit lp mi cn bng ng gia qun th nm men vi c cht: ph thuc vo lng nm men ban u

Lng t bo ny chi

Thi gian ln men

Hm lng cc sn phm bc hai v t s tng quan gia chng (v d: nu lng t bo nm men u l 10 x 10 6 lng diexetyl to ra l 0,45 mg/l, khi lng t bo nm men ban u 20 x 10 6 lng diexetyl to ra l 0,32 mg/l, tng t diaxetyl, aldehyde v ru bc cao cng gim).

c. Nng cht ha tan ca dch ng houblon ha

T 11 12%, cng sinh sn v pht trin ca t bo nm men t l tuyn tnh vi nng cht ha tan, hm lng nit trong .Theo Rubner, t 2,5 12% khng nh hng n tc ln men

Khi nng tng n 15 20% hoc gim di 2% th cng ln men gim ng k.

d. Nhit ca dch ln men

Khi nhit ln men cao th:

+ Thi gian ln men nhanh

+ Mt ti a t c cao hn so vi nhit thp

+ Ln men trit hn nhng hm lng sn phm bc hai, c bit diaxetyl v aldehyde to ra nhiu hn.

+ Lng sinh khi to ra nhiu hn, lng t bo cht tng lm suy gim cc c tnh cng ngh nhanh hn.

+ T s gia cc cu t trong bia khng cn i, cht lng bia gim.

e. p sut b mt

Xc nh mc bo ha CO2 trong bia, c ch qu trnh ln men (c bit giai on logarit) lm nh hng ti lng sinh khi to thnh. Khi p sut b mt l 3 4 kg/cm2 s nh ch qu trnh ln men, do vy khi ln men chnh p sut b mt trong thit b ln men nn duy tr nh hn 1 kg/cm2.

nh hng ti trng thi sinh l, p sut cao nm men chng gi.

Khi qu trnh ln men chnh gn kt thc nn tng p sut b mt v: hn ch c qu trnh oxy ha v tng bn ca bia.f. Hm lng oxy

Cn thit cho s pht trin sinh khi ca t bo nm menHm lng oxy nh hng trc tip n tc sinh sn ca t bo nm men lng sinh khi to thnh.

Lng oxy ha tan trong dch ng houblon ha ch khong 6,7 7mg/l.

g. Cng khuy o dch ln men

Thc y c qu trnh ln men, rt ngn thi gian ln men nhng sn phm cha nhiu sn phm bc hai lm nh hng n hng v ca bia.

h. Nng ca sn phm ln men

Nng ru etylic tao thnh nh hng n qu trnh ln men nh sau:

2% kh nng ny chi ca t bo nm men gim

> 5% kh nng ny chi ca t bo nm men chm dt.

>12% nh ch hon ton qu trnh ln men.

Kh nng chu cn ca cc chng nm men khc nhau th khc nhau.

5.2.1.2 Hp th dinh dng ca nm men

- Hp th cacbon

- Hp th nit5.2.1.3 Sinh tng hp cc sn phm bc hai (sn phm ph)

a. Glycerin

L mt cu t rt qu i vi bia, n lm du v v lm tng thm m cho sn phm.

b. Ru bc cao

Gm c: propylic, izopropylic, izobutylic, amylic, izoamylic v nhiu loi khc.

Ty theo phng php ln men m hm lng ru bc cao khc nhau.

Ru bc cao nh hng xu n gi tr cm quan ca bia.

c. Acid hu c

Gy ra do vi khun (khi dch ng houblon ha b nhim)

Do qu trn diamin ca acid glutamin hoc qua phn ng chuyn amin.

d. Ester hoc aldehyde

Ester to thnh do s tng tc gia cc sn phm bc hai thng trc, ester ha cc acid bay hi v khng bay hi vi cc loi ru khc nhau. Ester hnh thnh vng thm ca bia, c hnh thnh ch yu trong giai on ln men chnh (18,6mg/l), trong bia thnh phm l 25mg/l.Aldehyde l sn phm trng trc ca qu trnh trao i cht ca nm men, vi mt lng nh aldehyde s lm tng thm hng v cho bia, vi mt lng ln s lm gy nh hng xu n cht lng ca bia. Lng aldehyde gim nhiu trong giai on ln men ph.e. Acetoin, diaxetyl v 2,3 butandiolBa hp cht ny to ra do hot ng sng ca t bo nm men trong giai on ln men chnh. Trong , diaxetyl gy nh hng rt xu n cht lng ca bia, c mi hi mnh, v ng kh chu v tc ng n h thn kinh ca con ngi.

Diaxetyl to thnh trong ln men chnh t 0,35 0,55mg/l v chng b kh trong thi gian tng tr, thi gian cn thit cho qu trnh kh ny t nht l 3 tun.

f. Hydro sunfua (SH2) v mercaptan

To thnh do cc hp cht cha gc sunfat, sunfit v cc amin c cha lu hunh trong dch ng.Do hin tng t phn ca nm men.L nhng hp cht c hi ti mi thm v v ca bia.

5.2.1.4 Cc qu trnh v nhng bin i khc

a. S thay i chua v nng lc m

- chua gia tng do s to thnh CO2 v cc acid hu c trong qu trnh ln men (pH = 5,5 5,6 gim xung cn 4,4 4,5).Ph v nng lc m ca h thng phosphate (pH = 5,57 7,07) v to thnh h m mi acid hu c v mui ca chng (pH = 4,27 5,67)

b. S thay i th oxy ha kh v cng mu

Thay i th oxy ha kh do gim lng oxy ha tan trong dch ng.Cng mu gim do cc hp cht polyphenol d oxy ha b kh v sau b kt lng li.

c. S kt mng ca t bo nm men

L qu trnh t bo nm men hp ph v dnh vi nhau thnh mng do:

V ca t bo nm men tit ra cc nim dch.

Thay i in tch tnh in

d. S to bt

CO2 to thnh trong qu trnh ln men lin kt vi cc cht hot ng b mt nh: protein, cht ng, polyphenol to thnh bt.

Hnh: Bn ln men

5.2.2 Ln men ph

5.2.2.1 Din bin cc qu trnh giai on ln men ph v tng tr

Cc qu trnh ha sinh, ha l, sinh l din ra tng t nh trong giai on ln men chnh nhng chm hn v nhit giai on ny ch t 0 1oC.

L qu trnh chuyn ha tip tc ca ln men chnh: chuyn ha ht ng c kh nng ln men trong bia non.

L qu trnh kh diaxetyl, lm gim hm lng aldehyde, hm lng ru bc cao, phn ng to ester. Thc cht y l qu trnh lo ha bia non tng cht lng cm quan ca sn phm.

Thi gian tn tr v nhit ca mi trng l hai yu t quan trng c bit nh hng n cht lng v bn keo ca sn phm.

Kh nng ha tan ca CO2 ph thuc vo nhit v p sut trn b mt ca n.

Da vo nh lut Henry

P

k =

c Trong :k: hng s ph thuc vo nhit ca bia

p: p sut CO2 trn b mt ca bia

c: nng CO2 ha tan vo trong bia

S lng cn

+ T bo nm men

+ Cc ht cn mn khc

giai on u

* Qu trnh ln men vn tip din vi tc rt b, kh CO2 to thnh c chiu hng si ngc ln trn b mt* Nhit ca bia cha ng nht, pha ngoi thnh thit b nhit t 0 1oC, trong khi nhit bn trong vn cn cao t 8 10oC nn vn xy ra hin tng i lu nhit

giai on sau:

* Nm men kt lng, hp cht protein polyphenol ta, do vy thi gian cng ko di tc lm trong bia cng nhanh.Kim tra qu trnh ln men ph, b sung:

Cht hp ph

Cht kt lng

Cht chng oxy ha.

5.2.2.2 Thnh phn ca bia sau khi ln men ph- Bia sau khi ln men chnh, t bo nm men tiu th ht cc ng ln men, ch cn li mt t ng maltotrioza.- gip cho hng v tt cho bia cc t bo nm men lng xung di y thit b u b loi b.- Trong giai on ln men ph diacetyl c chuyn thnh acetoin, acid hu c v ru thnh ester gip n nh thnh phm v lm tng tnh cm quan ca sn phm.

5.3 Hon thin sn phm

Sau mt thi gian di c nhit thp, thnh phn ha hc v tnh cht cm quan ca bia c nh hnh. Tuy nhin, tr thnh hng ha thng mi, bia cn c x l qua cc cng on sau:

Lm trong tng thm gi tr cm quan, n nh thnh phn c hc, lm tng bn sinh hc v bn keo ca bia.

B sung thm CO2 cho t hm lng cn thit nhm lm tng cht lng cm quan, chng oxy ha, chng kt lng v l mi trng tt bo qun bia.Chit bia vo chai, vo block, vo lon d vn chuyn v bo qun.Thanh trng dit nm men nng cao bn sinh hc cho bia.5.3.1 Lm trong bia

- Mc ch: lm trong bia l loi b cc phn t gy c cho bia nhm mc ch tng thi gian bo qun cho bia khi chng lu hnh trn th trng.

- Phng php lm trong: lm trong bia da vo hai phng php chnh l lc v ly tm.

> Lc:

Hnh: H thng lc khung bn

Nguyn tc:

Gi cht bng lc c hc cc ht c kch thc ln hn kch thc l hng ca vt liu lc.

Hp ph cc ht c kch thc b hn, thm ch cc ht ha tan dng keo v cc ht ha tan phn t.Vt liu lc:

+ Khi lc: c lm bng x bng trn vi bt amin ri p cht thnh bnh.

+ Tm lc: si cellulose c dt v p thnh tm.

+ Bt diatomit

u, nhc im ca phng php lc:

u im: lm cho bia sng lp lnh, tng gi tr cm quan ca sn phm

Nhc im: lm gim nng cht ha tan trong bia, lm gim hm lng CO2, lm gim kh nng to bt

Ly tm:Nguyn tc: da vo tnh cht c hc tch cc ht phn tn ra khi pha lng

u, nhc im ca phng php ly tm:

u im: thnh phn v tnh cht ca bia sau ly tm thay i khng ng k

Nhc im: sau khi ly tm nhit ca bia s tng ln, c tnh kh yu hn so vi bia lc v kh nng c lnh cng cao hn so vi bia lc.5.3.2 Chit bia

5.3.3 Thanh trngTrong bia thnh phm lun cha cc t bo cn sng bao gm nm men v mt s vi sinh vt ngoi lai nh vi khun acetic, si nm. Do phi thanh trng bia tiu dit cc vi sinh vt. Thi gian thanh trng bia ph thuc ch yu vo nhit , thng thng thanh trng bia (i vi dng bia chai) th ngi ta gi khong 15 pht nhit 62 63oC.Malt (75%)

(2)4

(2)1

hi

Nc

0 40 60 100 140 180 220 260

Lng ng ln men trung bnh mi gi, %

1.75

1.50

1.25

1.20

1.00

0.75

0.50

0.25

Cht ng (tan trong ete dietyl)

Acid ng (hp cht tinh ch)

Nha ng (hp cht v nh hnh)

acid ng 6 9%

acid ng 3- 4 %

Nha mm 5- 6%

Nha cng 1 2%

-amylase

Glucoamylase

Glucoamylase

thy phn chm

Isoamylase

hay pullulanase

-amylase

Tc phn ng

nng enzyme

Tc phn ng

Nhit

(2)5

(2)8

Dch ng ha

Nc

Hi

Nm men

Dm chn

Nghin

Cn

Lm sch

X cn

Ln men

Lm lnh nhanh xung 8oC

Ly tm ton b dch ng

Thi b

Lm ngui n 90oC

Tch b non

Dch ng houblon ha

Dm chn

Nm men

Dch ng ha

Nc

Hi

hi

Nc

(2)8

(2)5

(2)4

(2)1

Lc dch ng

ng ha

7

5

6

2

1

4

4

3b

3a

Houblon ha

Hoa houblon

Go 25%

Lm sch

cn

Nghin

H ha

Lc hoa houblon

B hoa

Lng

Lm lnh nhanh

Ln men chnh

Ln men chnh

Men ging

Nhn ging

Thu hi men

Thu hi CO2

Ln men ph

Lc bia

Bo ha CO2

X l

Chit chai

Chit lon

Lon

Thanh trng

Sn phm bia lon

Thanh trng

Dn nhn

Sn phm chai

Men ging

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