F ed -b atc h cu ltu res w ere ex am in ed in o rd er to in crease ethanol con tent in the green becr.. Metaboỉiíe production Tim e hours Fig... * The initial volume of the wort was 1,50
Trang 1V N U Jo u m a l of Science, N a tu ra l Sciences a n d T echnology 23 (2007) 166-173
Application of fed-batch fermentation in high-gravity brewing
Vu Tran Khanh Linh, Le Van Viet Man*
Department o f Food Technology, Faculty o f Chemical Engineering, Ho Chi Minh City University o f Technology, Vietnam National University, 268 Ly Tỉiuong Kiet, District 10, Ho Chi Minh City, Vietnam
R eceiv ed 18 M ay 20 0 6
A b s tr a c t E co n o m ic d e m a n d s to in ten sify th e b re w in g p ro c e ss and in cre ase the ferm enter
p ro d u c tiv ity have stim u late d in terest in h ig h -g ra v ity brevving Hovvever, in c re a sin g w o rt sugar
co n c en tratio n can h a v e a d etrim en tal effect o n íerm e n ta tio n p e río rm a n c e , a d v e rse ly a íĩe c tin g yeast
p h y sio lo g y and alterin g th e p h y sical and íla v o r p ro p erties o f th e b e e r p ro d u c t M an y m eth o d s such as: h ig h er p itch in g rates, h ig h er fe rm en tatio n tem p eratu res, m ore e ffic ie n t a e ra tio n than in con v en tio n al b re w in g , a n d im m o b ilised y east w ere u sed to im p ro v e this p ro cess
T h is stu d y fo cu sed o n the a p p lica tio n o f fed-batch fe rm en tatio n in h ig h -g ra v ity brew in g T w o fed-batch cu ltu re s w ith d iffe re n t specific g ra v ity o f the su p p le m e n te d w o rts w ere ex a m in e d T he
sp ec iíĩc g ra v ity a fte r th e su p p lem en tatio n w as the sam e D e sp ite the h ig h er p rim a ry ferm entation tim e, b o th fe d -b atch cu ltu re s ach ie v ed h ig h er co n c en ư atio n o f ethanol a n d lo w e r d iace ty l content than those in b atch fe rm en tatio n T h ese re su lted in the p o ssib ility o f in c re a sin g the fínal b eer volum e an d o f sh o rten in g th e m atu ra tio n tim e
K eyw ords: F ed -b a tc h íerm e n ta tio n , hig h gravity brew in g , S a c c h a ro m y c e s cerevisiae.
1 I n tr o d u c tio n
T h e traditional b rew in g is g en erally app lied
to ferm ent w o rts w ith 1 l- 1 2 ° B x sp ecific g ravity
to pro du ce beers o f 4 - 5 % (v/v) eth ano l W ith
the need to in crease p ro d u ctiv ity and
co nsequ ently co m p etitiv en e ss on the m arket,
m any b rew eries are ch an g in g th e ir m eth o d s and
processes for p ro d u cin g beer A m ajo r
innovation in b rew in g is hig h g rav ity b rew in g
te c h n o lo g y -th e ferm en tation o f w o rt co n tain in g
16 g o r m ore o f đ isso lv ed so lid s p er 1 0 0 g o f
w ort T h is techn olog y h as b eco m e p o p u la r due
to such ad vantag es as in c re asin g p la n t
* Corresponding author Tel.: 84-8-8646251
E-mail: Iwman@ hcmut.edu.vn
effic ien cy an d cap acity , re d u c in g energy, lab o u r
an d Capital co sts, as w ell as increasing in ethanol y ie ld p er u n it o f ferm en table extract
M o re o v e r, it can h e lp im p ro v e b eer stability,
p ro d u ce sm o o th e r ta ste an d g reater flexibility to the fm al p ro d u ct [1-4] O n the other hand, the dravvbacks o f th is p ro cess include decreased
m aterial efficien cy , as w ell as red u ced foam stab ility an d íla v o u r m a íc h in g [5] In addition,
d u rin g ferm e n tatio n o f h ig h -g rav ity w ort, the
y e a st a re ex p o sed to ex trem e conditions:
in c re ased osm otic p ressu re and increased
to x icity o f p ro đ u ced eth an o l [2,6,7], nutrient lim itatio n esp ecially c o n c e m in g oxygen and assim ilab le n itro g en [ 1 Ị
T h e a risin g p ro b lem s h av e been solved by
u sin g h ig h e r p itch in g rates, h ig h e r ferm entation
Trang 2V.T.K Linh, L.v.v Man / V N U Ịoum al o f Science, Naturaỉ Sciences and Technology 23 (2007) 166-173 1 67
te m p eratu res [1], m o re e ffic ie n t aeratio n than in
co n v en tio n al brevving [8] a n d im m o b ilised
y east [2] O ne o f th e p o ssib ilitie s to red u ce the
d etrim en tal factors acting in h ig h -g rav ity
b rew in g co u ld b e fed -b atch ferm en tatio n T his
tech n iq u e is co m m o n ly u se d in m icro bial
ferm en tatio n b e c a u se it co m b in es the
ad v an tag es o f b o th b atch an d co n tin u o u s
ferm en tatio ns F ed -b atc h íe rm en ta tio n is used
to p rev en t or d ecrease su b strate-a sso ciated
grovvth in hibition by c o n ừ o llin g n u trien t
su pply P ro cess is starteđ as a b atch p ro cess
w ith a sm all am o u n t o f b io m ass an d su b strate in
the íerm en to r T h e n th e su b strate feed is applied
w hen m o st o f th e in itially a d d e d su b strate has
been co n su m ed T h is p ro ced u re h elp s to
increase th e total su b strate co n ten t in the
ferm entor, w h ile alw ay s m a in ta in in g a low
su b strate co n ce n tratio n d u rin g ferm e n tatio n for
reducing the n e g a tiv e effect o f o sm o tic pressure
on yeast T h u s, fed -b atch ferm en tatio n allow s
đecreasin g th e in itial y east c o n ce n tratio n and
the co st o f in o c u lu m p ro p ag atio n
T h is stud y fo cu sed on the prim ary
ferm entatio n in b rew in g F ed -b atc h cu ltu res
w ere ex am in ed in o rd er to in crease ethanol
con tent in the green becr
2 M a te r ia ls a n d m e th o d s
2.1 Wort production
16 °B x w o rt w a s p ro d u ced fro m 80% b arley
m alt (im p o rted ữ o m A u stralia) and 2 0% rice
(V iet N am ), b y d eco c tio n m ash in g T h e 28 °Bx
an d 24 °Bx w o rts w ere p re p a re d b y v acuum
co n cen tratio n at 60°c fro m th e 16 °Bx w ort
2.2 Microorganừm andfermentation conditions.
Y east u sed in th is stu dy w a s a lag er strain
o f Saccharomyces cerevisiae, supplied by
F o ster T ie n G ian g Ltd C o m pany T h e pre-
in oculum w as o b ta in ed from y east cultures
m a in tain ed on m alt-ag ar slan ts at 4°c The
in oculum p ro p a g a tio n w as carried out in the 10°Bx w o rt T h e p itch in g rate w as about
10 X 106 v ia b le cells m L '1 A ll íerm en tation s
w ere p e rfo rm e d in a b io re a to r B IO S T A T B (B B raun B io tech In tern a tio n a l) at 17°c w ith 1,5 L o f 16°Bx w ort In fed -batch ferm entation,
2 sam p les w ere ex am ined: 1,5 L o f fen n en tin g
w o rt w as su p p lem en ted b y 1,5 L o f 28°Bx w ort
or 2,5 L o f 24°B x w ort In th e 2 fed-batch sam ples, th e sp eciíìc g rav ity in the m edium
a íte r su p p lem en tatio n w as the sam e (16°Bx)
2.3 Analytìcaỉ methods
D u ring the ferm en tatio n , th e evo lu tio n o f
pH , total n u m b e r o f y east cell and viability,
w o rt sp eciĩic gravity , red u cin g sugar, íree
am in o n itro g e n , eth ano l and d iacety l contents
w ere ex am in ed T h e n u m b e r o f y east cell w as
d eterm in e d b y u sin g an Im pro ved N eu bauer
H aem o c y to m e ter at x 4 0 0 m ag n iíĩcatio n w ith a light m icro sco p e Y east viability w as
d eterm in e d b y u sin g th e m ethy lene blue staining [9] A fter rem o v in g y east bio m ass by
c e n trifu g atio n (6 0 0 0 rp m , 15 m ins, 4°C), the specific g rav ity w as m easu red by a
re ử a c to m e te r C o n cen tratio n o f red u cin g sugars
w as q u an tified b y sp ectro p h o to m etric m ethod usin g th e d in itro salicy lic acid reag e n t [10] Free
am in o n itro g e n (F A N ) co n ten t w as m easured
b y sp ectro p h o to m etric m etho d, u sin g ninhydrin reag en t [11] E th ano l co n cen tratio n w as
d eterm in e d b y a m eth o d b ased on distillation
an d d en sity q u a n tiíĩc a tio n [12] C oncentratio n
o f diacetyl w as determ ined b y spectrophotom etric
m eth o d u sin g o - p h en y len d iam in reag en t [1 1]
T h e su g ar up tak e rate (g /L h ) w as calcu lated as the ratio o f the re d u cin g su g ar co ntent (g/L )
co n su m ed b y y e a st to th e ferm entatio n tim e (h)
Trang 3168 V.T.K Linh, L.v.v M an / V N U Ịoum al o f Science, Natural Sãences and Technology 23 (2007) 166-173
3 Results and discussion
3.1 Yeast growth
Y east gro w th d uring th e íe rm en ta tio n is
p resen ted in Fig 1
In the b atch ferm en tatio n , d u rin g the íĩrst 60
h ours, y east cell n u m b e r in the cu ltu re increased
qu ick ly b ecau se the w o rt w as ric h in o xygen
and nutrients T h e m a x im u m co n ce n tratio n o f
cells (ap pro xim ately 120 X 106 cells/m L ) w as
o b tained after 108 h ours A fter that, the
b io m ass d ecreased p ro g ressiv ely T h u s th e 108*
íerm en tin g h o u r w as ch o sen as th e m o m en t for
wort supplementation in the tw o fed-batch cultures
In fed-batch íe rm en ta tio n , a fte r fresh w ort
feeding, th e y east co n cen tratio n in sam ple 2
w as low er th an th a t in sam p le 1 T h is w as due
to th e h ig h e r v o lu m e o f w o rt sup plem en tatio n
O u r experim en tal resu lts sh o w ed th at the
m axim um y east co n ce n tratio n reach ed in the
tw o sam ples w as sim ilar; h o w ev er, the grow ing
tim e o f y east in sam p le 2 w as 24 h o u rs lon ger
than th at in sam ple 1 (F ig 1)
T im e (h o u rs)
Fig 1 K inetics o f y ea st grovvth d u rin g the
íerm en tatio n o f 1,5 L o f 16 °Bx w orts: ( * ) b atch
culture, ( ♦ ) fed -b atch cu ltu re 1: su p p lem en ted w ith
1 L o f 28 °Bx w o rt after 108*1* ferm en tin g h ours, ( A )
fed-batch cu ltu re 2: su p p lem en ted w ith 1,5 L o f 24
°B x w ort
3.2 Substrate assimilation
T im e (h o u rs) Fig 2 K in etics o f sp ec ific g ra v ity durin g the
fe rm e n ta tio n o f 1,5 L o f 16 °Bx w orts: ( * ) batch
cu ltu re, ( ♦ ) fe d -b atch cu ltu re 1: su p p lem en ted w ith
1 L o f 28 °Bx w ort afte r 108* ferm enting h ours, ( A )
fe d -b a tc h c u ltu re 2: su p p lem en ted w ith 1,5 L o f 24
°B x w ort
Fig 2 sh o w s the ev o lu tio n o f the speciíĩc
g rav ity d u rin g th e b atch and fed-batch
íe rm e n ta tio n s
In th e b atch cu ltu re, afte r 108 ferm enting
h o urs, th e sp eciíĩc g rav ity did not change sig n iíĩc a n tly It w as due to th e low
c o n c e n ừ ^ tio n o f su b strates and high
c o n c e n tra tio n o f som e tox ic m etabo lites (eth an o l an d o th e r h ig h e r alco ho ls) p ro d u ced by
y e a st in th e m ed iu m It can be co n íĩrm ed that the c h o s e n m o m en t - th e 108th ferm enting hour for fre s h w o rt su p p lem en tatio n w as reasonable
In th e fed -b atch cu ltu res, fresh w ort
su p p le m e n ta tio n in creaseđ the n u trien t contents
an d d e c re a se d eth an o l co n cen tratio n in the
fe rm e n tin g m ed iu m T h erefo re, th e yeast
p ro p a g a tio n co n tin u ed (F ig 1) and the speciíìc
g rav ity d ecre ase d sig n iíĩcan tly , p articularly
d u rin g th e n ex t 48 h o u rs after supplem enting
F ro m th e 15 ó* ho ur, the sp eciíic gravity
d e c re a se d w ith a slo w er rate: the substrate assim ila tio n rate in fed -batch culture 1 w as
lo w e r th a n th a t in fed-batch cultu re 2 At the
en d o f th e p rim ary ferm entation , the speciíĩc
Trang 4V.T.K Linh, L.v.v M an / VNƯ ]oum al o f Science, Natural Sciences and Technology 23 (2007) 166-173 1 69
gravity o f g reen b eer in b o th fed -b atch cu ltu res
w ere still ra th e r h ig h e r than th at in th e b atch
culture P erh ap s the in creased co n ce n tratio n o f
ethan ol in the m ediu m c a u se d a h a rm íu l effect
on y east cells, w h ich led the ferm e n tatio n to be
slu gg ish o r ev en stuck
In this stu dy, th e p rim ary ferm e n tatio n was
con sidered to h av e co m p lete d w h en the ethanol
con cen tratio n in creased less th an 0,3 % (v/v) in
th e successiv e 24 ferm en tin g h o u rs T he
ỉe rm en ta tio n tim e in fed-batch cu ltu re s 1 and 2
w as 204 h o u rs and 228 h o u rs resp ectiv ely T he
fm al sp eciílc g rav ity in fed -batch c u ltu re 2 w as
lo w er than th at in fed -b atch cu ltu re 1 (10 ,7 °Bx
vs 11,5 °Bx) T h u s, it can b e c o n c lu d e d that in
fed-batch cu ltu re 2, y east co n su m e d m ore
n u tn e n ts than in fed -batch cu ltu re 1
Y east g ro w th in v o lv es the u p ta k e o f F ree
A m in o N itro g en (F A N ) for th e sy n th esis o f
cellu lar p ro tein (Fig 3)
Fig 3 ind icated th at d u rin g th e íĩrst 84
hours, F A N co n ce n tratio n d ecre ase d sh arp ly in
the 3 cultures A fter that, it b eg an to increase
slig h tly in b atch íerm en ta tio n , th a t m ay be due
to the autolysis o f dead cells T h is p h en o m en o n
led to a rele ase o f in tracellu lar n itro g e n based
co m po und s
Time (ho u rs) Fig 3 K in etics o f free am in o n itro g en assim ila tio n
during the íerm e n ta tio n o f 1,5 L o f 16 °B x w orts:
( * ) b atch cu ltu re, ( ♦ ) fe d -b atch c u ltu re 1:
su pplem ented w ith 1 L o f 28 °Bx w o rt a íte r 108*
fe rm en tin g h ours, (▲ ) fed-bũtch c u ltu re 2:
su p p lem en ted w ith 1,5 L o f 24 °B x w ort
A fter w o rt su p p lem en tatio n , the FA N
co n ce n tratio n in fed-b atch cu ltu re 2 w as hig her than th at in fed -batch cu ltu re 1 D uring th e n ex t
48 h ours, F A N co n c e n ữ a tio n d ecreased due to the cell g row th T h en it au gm ented w hen the
d eath p h ase o f y east began (after the 108* ferm en tin g h o u r - Fig 3) and the autolysis took place H ig h ethanol co n cen tratio n w as another harm ful facto r to the y e a s t’s viability,
in c re asin g the n u m b e r o f dead cells
D u rin g the last h o u rs o f the prim ary ferm entatio n, th e F A N level in fed-batch
cu ltu re 1 in creased m ore sứ o n g ly than that in fed-batch cu ltu re 2 It co u ld be reaso n ed that at the 156* h o u r, th e d eath p hase o f yeast in fed-
b atch cu ltu re 1 b eg an w h ile in fed-batch culture
2, the y e a s t g ro w th still continued T his
p h en o m en o n affirm ed th e resu lts ob tained in íĩg u re 2: a fle r 156 ferm en tin g hours, the yeast activ ity in fed -b atch cu ltu re 2 w as higher than that in fed-b atch cu ltu re 1 an d the sp eciíĩc
g rav ity in fed-batch cu ltu re 2 w as low er than that in fed -b atch cu ltu re 1
3.3 Metaboỉiíe production
Tim e (hours) Fig 4 K in etics o f eth an o l p ro d u c tio n during the
fe rm en tatio n o f 1,5 L o f 16 °B x w orts: ( * ) batch culture, ( ♦ ) fed-batch cu ltu re 1: sup p lem en ted w ith
1 L o f 28 °B x w ort afìe r 108* ferm cn tin g hours, (▲ )
fe d -b a tc h cu ltu re 2: su p p lem en ted w ith 1,5 L o f 24
°B x w ort
Trang 5170 V.T.K Linh, L.v.v M an / V N U Ịoum al o f Science, Natural Sríences and Technology 23 (2007) 166-173
Fig 4 sh o w e d th a t in b a tc h ferm e n tatio n ,
th e final eth an o l c o n c e n tra tio n c o u ld re a c h o n ly
6,46 % (v /v ) due to th e lo w n u trie n t c o n te n t and
h ig h eth an o l lev el In fe d -b a tc h ferm e n tatio n ,
th o se h a rm íu l e íĩe c ts c o u ld b e o v erco m e,
re su ltin g in h ig h e r íìn al e th a n o l co n ten t
T h e íìn al eth an o l c o n c e n tra tio n s w ere
8 ,52 % (v /v ) in b o th fe d -b a tc h cu ltu re s, a lth o u g h
th e resid u al su g ar c o n te n t w as still ra th e r high
It can b e su p p o se d th a t th e a c tiv ity o f the
Saccharomyces cerevisiae stra in u se d in th is
stu d y d ecre ase d re m a rk a b ly at th a t ethano l
co n ce n tratio n
T h e o b ta in e d re su lts in fíg u re 4 co u ld
ex p lain fo r th e đ a ta in íĩg u re 3 In fed -b atch
cu ltu re 1, fro m th e 18001 h o u r to the 2 0 4 th hou r,
F A N co n ce n tratio n in c re a se d sh a rp ly (F ig 3);
d u rin g this p erio d , th e in c re a se in eth an o l
co n ten t fro m 7,2 7 °/o (v /v ) to 8,52 % (v /v ) w as
o b serv ed (F ig 4) T h u s, it w as e v id e n t th a t the
in crease in eth an o l c o n te n t in th e cu ltu re h a d a
b a d e ffect on y e a st v ia b ility In fed -b atch
c u ltu re 2, the sam e p h e n o m e n o n w as also
o b serv ed F ro m th e 2 0 4 h o u r to th e 2 2 8 lh h o u r,
th e eth an o l c o n c e n tra tio n in c re a se d fro m 7,79
% (v/v) to 8,52 % (v/v), the F A N co n ce n tratio n
also au g m en ted in the m e d iu m d u e to the
au to ly sis o f d ead cells
Tim e (h o u rs) Fig 5 C h an g e in p H d u rin g th e fe rm e n ta tio n o f 1,5
L o f 16 °B x w orts: ( + ) b a tc h c u ltu re , ( ♦ ) fe d -b atch
cu ltu re 1: su p p le m e n te d w ith 1 L o f 28 °B x w ort
afte r 108* fe rm en tứ ig h o u rs, ( A ) fe d -b a tc h cu ltu re
2: su p p le m e n te d w ith 1,5 L o f 24 °B x w ort
D u rin g the alc o h o lic ferm en tatio n , the
d ecrease o f pH is re la te d to the fo rm atio n o f
C Ơ2 an d organ ic a ciđ s o f y east cells B esid es,
th e in c re ase o f pH m a rk s th e b e g in n in g o f y east auto ly sis
Fig 5 p resen te d th e ev o lu tio n o f p H in
b atch a n d fed -b atch ferm en tatio n s T h e re w as
no s ig n iíĩc a n t d iffe re n c e in pH v alu es o f the green b e e rs in th e 3 cu ltures
Tim e (h ours)
Fig 6 E v o lu tio n o f d ia c e ty l c o n c e n tra ú o n d u rin g
th e fe rm en tatio n o f 1,5 L o f 16 °Bx w orts: ( * ) b atch culture, ( ♦ ) fe d -b atch cu ltu re 1: su p p lem en ted w ith
1 L o f 28 °B x w ort afte r 108th íerm e n tin g h ours, ( A )
fe d -b a tc h cu ltu re 2: su p p le m e n te d w ith 1,5 L o f 24
°B x w ort
D iace ty l is One o f th e m ost im p o rtan t b y -
P ro d u cts in alco h o lic ferm en tation A t low levels, it gives b e e r a slic k m o u th íeel; at hig h er levels, th e íla v o r b e c o m e s bu ttery an d that
d e c re a se s the sen so ry p ro p erties o f the fm al pro d u ct
Fig 6 sh o w ed th a t the d iacety l level
in c re a se d du rin g th e íĩrst 84 h o u rs an d reached the m a x im u m c o n c e n tra tio n (ap p ro x im ately 2
m g/L ) M a n y a u th o rs affiim ed th at diacetyl
ío rm a tio n is clo sely re la te d to the y cast grow th,
p a rtic u la rly to th e v a lin e b io sy n th e sis [13] In
Trang 6V.T.K Linh, L.v.v M an / V N U Ịournal oịScừnce, Natural Sciences and Technology 23 (2007) 166-173 1 71
co m p ariso n w ith the o b ta in e d resu lts in Fig 1,
th e in tensive grow th o f y e a st w as ob serv ed
d u rin g this p eriod T h e n the d ia cety l c o n te n t in
th e ĩe rm en tin g m ed ia d e c re a se d by red u ctio n
reac tio n cataly zed b y th e e n z y m e sy stem in
yeast T h is re su lt w as s im ila r to th o se in m any
p rev io u s stu d ies [13,14]
A fter fresh w ort su p p le m e n ta tio n , d iacetyl
c o n ce n tratio n s in th e 2 fed -b atch cu ltu res
in creased again due to y e a s t g ro w th an d then
d ecreased It can b e n o te d th a t the seco n d p eak
o f diacetyl íò rm a tio n in fed -b atch cu ltu re 2 w as
m u c h lo w er than th a t in fed -b atch cu ltu re 1
T h e exp lanation can b e th a t th e F A N co n ten t in
fed-b atch cu ltu re 2 w a s m u ch h ig h e r than in
fed-b atch cu ltu re 1 L o w d iacety l level in green
b e e r is an ad v an tag e in b re w in g b eca u se the
m atu ratio n tim e w ill b e sho rter
T a b le 1 p re se n te d th e p a ra m e te rs o f the
p rim a ry íe rm e n ta tio n in b e e r p ro d u c tio n using
b a tc h an d fe d -b a tc h cu ltu res
In th e fe d -b a tc h c u ltu res, in sp ite o f th e
lo n g e r p rim a ry fe rm e n ta tio n tim e, the su gar
c o n te n ts a ss im ila te d b y y e a s t w ere h ig h e r than
th a t in th e b a tc h c u ltu re B esid e s, th e su gar
u p ta k e ra te in fe d -b a tc h cu ltu re 1 an d 2 w ere
30 ,2 % a n d 2 0 ,6 % h ig h e r th an th a t in the b atch culture
T h e fin al e th an o l co n c e n tra tio n in th e fed-
b a tc h fe rm e n ta tio n s w a s 32 % h ig h e r than that
in th e b a tc h ferm e n tatio n T h is is a very
im p o rta n t ad v a n ta g e o f h ig h g rav ity brevving
b eca u se th e h ig h e r c o n c e n tra te d b e e r w e ach iev e, th e m o re v o lu m e o f fm al b e e r w e
p ro d u c e T h e re su lts fro m ta b le 1 shovved that, the v o lu m e o f final b e e r in th e fed -b atch
fe n n e n ta tio n s w as m u c h h ig h e r th an th at in th e
b a tc h íe rm e n ta tio n
T ab le 1 P ara m e ters o f th e p rim a ry fe rm en tatio n in b e e r p ro d u c tio n u sin g b a tc h and fe d -b a tc h cu ltu res
B atch fe rm en tatio n “ F e d -b a tc h
íe rm e n ta tio n 1A
F ed -b a tc h
íe rm e n ta tio n 2C
( g / í )
b e e r (g/L )
b e e r (m g/L )
V olu m e o f final b e e r a fte r b e in g 1,50 L o f 16 °Bx w o rt -> 1,50 L o f 16 °Bx 1.50L o f 16 °Bx
d ilu te d to eth an o l c o n c e n ư a tio n o f 1.94 L o f b e e r w o rt a n d 1,00 L o f w o rt a n d 1,50 L o f
5 % ( v / v ) 2 ,5 0 L o f 16 °B x w o rt 2 8 °B x w o rt -> 24 °B x w ort ->
3,23 L o f beer 4 ,2 6 L o f b e e r 5,11 L o íb e e r
3 L o f 16 °B x w ort -> 3,88
L o f beer
* The initial volume of the wort was 1,50 L, the initial speciíic gravity was 16 °Bx
bThe initial volumc of thc wort was 1,50 L, the initial speciíic gravity was 16 °Bx The culture was supplemented with 1 L o f
28 °Bx wort The spccific gravity attcr supplementing was 16 °Bx
c The initial volume of the wort was 1,50 L, the initia! speciíic gravity vvas 16 °Bx The culturc was supplemented with 1,50 L
o f 24 °Bx wort The spcciíic gravity aftcr supplcmcnting was 16 °Bx
d It was supposed that the ethanol content in the green beer did not augmented during the secondary íermcntation
Trang 717 2 V.T.K Linh, L.v.v M an / V N U Ịo u m a l o f Science, Natural Sciences and Technology 23 (2007) 166-173
A lth o u g h th e e th a n o l c o n te n t in th e tw o fed-
b atch cu ltu res w a s sim ila r, fe d -b a tc h cu ltu re 2
w as co n sid e re d to b e m o re e ffic ie n t th a n fed-
b a tc h cu ltu re 1 fo r tw o reaso n s F irstly , lo w er
d iacety l o f g reen b e e r in fe d -b a tc h cu ltu re 2
m ad e th e m a tu ra tio n tim e b e c o m e sho rter
S eco nd ly , th e p itc h in g ra te in fed -b atch cu ltu re
2 w as lo w e r th a n in fe d -b a tc h cu ltu re 1 i f the
v o lu m es o f fínal b e e r in th e tw o c u ltu re s w ere
sim ilar
4 C o n c l u s ỉ o n
F e d -b a tc h c u ltu r e s h a v e s h o w n to b e m o re
a d v a n ta g e o u s th a n b a tc h íe r m e n ta tio n in h ig h
g ra v ity b re w in g In fe d - b a tc h íe r m e n ta tio n , th e
g re e n b e e r c o n ta in e d h ig h e r e th a n o l c o n c e n tr a tio n
a n d lo w e r d ia c e ty l c o n te n t In th is s tu d y , 2 fe d -
b a tc h c u ltu re s w e r e re a liz e d It w a s c o n c lu d e d
th a t, th e ra tio 1 : 1 o f th e v o lu m e o f w o r t fo r
s u p p le m e n tin g to th e in itia l v o lu m e o f w o r t in th e
íe rm e n to r w a s m o re e f f ic ie n t th a n th e ra tio 2 : 3
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