Food Chemistry 95 (2006) 357-381 www.elsevier.com/locte/!oodchem
"eview #imi $ir %e&'& - ti&'& #ritis rt *&derhe+e& , edwi+ eve& '$ert *erchtert 'y erdeli&c# Pusat Malting dan Brewing Brewing Sains, Katholieke Katholieke Universiteit Universiteit Leuven , Kasteelpark Arenberg Arenberg 22, B-3! "everlee, "everlee, Belgia
iterim 1 ovem$er 2004 me&erim dlm $e&t'# revisi &'ri 20054 diterim &'ri 2005 Abstrak
t i&i mslh #'lits 'tm $ir dlh %er'$h& #om%osisi #imi selm %e&yim%&& y&+ me&+'$h si!t se&sori#. er$+i rs m'&+#i& tim$'l ter+&t'&+ %d e&is $ir d& #o&disi %e&yim%&&. er$ed de&+& $e$er% &++'r $ir %e&'& $is&y di&++% di&++% &e+ti! '&t'# #'lits #'lits rs. Fo#'s 'tm 'tm dri %e&eliti& %e&eliti& %d $ir %e&'& telh telh mem%elri mem%elri #om%o&e& #rt'-%%&-rs () -2-&o&e&l d& %em$e&t'#&&y oleh o#sidsi li%id. "s $si li&&y #'r&+ diels#& t%i m'&+#i& setid#&y sm %e&ti&+&y '&t'# #es& se&sori# #esel'r'h& $ir $er'si. sl mere# telh sem#i& diteliti dlm $e$er% th'& ter#hir. ter#hir. ls& ls& i&i mer&+#'m %e&+eth'& %e&+eth'& st i&i te&t&+ sl #imi #imi dri $er$+i rs rs %e&'& d& me#&isme re#si $ert&++'&+ w$ '&t'# %em$e&t'#& mere#. el&'t&y el&'t&y h'$'&+& &tr %roses %rod'#si d& $ir rs st$ilits di$hs. : 2005 lsevier ;td ll ri+hts reservedeer4. <t #'&ci= stli&+4 %e&'&4 Flvo'rs4 rewi&+ 1. Pendahuluan
d%'& %rod'# m#&& li&&y '+ '&t'# $ir $e$er% s%e# ity >'l- d%t di#e&#& %er'$h& selm %e&yim%&&. ir r#-hid'% se$+i& $esr dite&t'#& oleh mi#ro$iolo+i y&+ col- loidl $'s wr& d& st$ilits rs. i ms ll' %e&m%il& ?es d& %ert'm$'h& %em$'s'#& $ir mi#ro-or+&isme y&+ di&++% se$+i #es'lit&-me&ye$$#& !e&ome& 'tm. m'& de&+& #em'& di $id&+ %em$'t& $ir #imi d& te#&olo+i mslh i&i se#r&+ se$+i& $esr di $wh #o&trol y&+ $i#. e$+i& $esr $'&+ telh $er+eser #e !#tor y&+ mem%e&+r'hi %er'$h& dlm $ir rom d& rs $ir rs di&++% se$+i y&+ %li&+ im%or %rmeter #'lits #'lits t&t %rod'#. m'& me&+i&+t me&+i&+t $hw de +'sti$'s et colo'ri$'s colo'ri$'s &o& est dis%'t&d'm #o&s'me& #o&s'me& tid# sell' tid# s'# rs $ir t'. @em&+ se$'h st'di (te%he&so& A m!orth 2002) de&+& 'i #o&s'me& me&'&'##& $hw rs %e&'& tid# sell' di&++% se$+i o!!-rs. ;e$ih %e&ti&+ $+i %resisi $ir dlh hr%&#o&s'me& %rmemili#i dlm me&+e&li rs h&y mere# terte&t' $ir y&+ 'm'm&y mere# mi&'m. &t'# meme&'hi hr%& s'mers co& rs mere# $ir terte&t' hr's #o&st&. m'& #re& rs y&+ dihr%#& dlh mlly t'rs $ir se+r terte&t' se$+i #i$t dri $ir %e&'& rs se%erti d%t $er'$h d& mim%im' !l- dihr%#& hil&+. B&i ter'tm hr's di&++% se$+i ls& y&+ %li&+ %e&ti&+ $hw $ir stli&+ tid# dii&+i&#&. @'li dri th'& 1960-& $e$er% %e&eliti& telh di!o#'s#& %d s%e# #imi $ir stli&+. @es#i%'& 30-0 th'& %e&eliti& $ir %e&'& tet% s'lit '&t'# me&+o&trol. e&+& me&i&+#t&y e#s%or $ir #re& mr- #et +lo$lissi mslh r#-hid'% d%t me&di etre- @ely is' %e&ti&+ '&t'# $e$er% %$ri#. ir %e&'& dlh !e&ome& !e&ome& y&+ s&+t s&+t #om%le#s. #om%le#s. B#htisr B#htisr i&i %d #imi #imi $ir %e&'& $erm#s'd '&t'# me&++m$r#& me&++m$r#& ity com%le- re#si %e&'&. 2. Perubahan sensorik dalam bir selama penyimpanan
, es'i %e&'lis. el el .= D32 16321604 != D32 16321576. -mil ddress=. $rt.v&derhe+e&E+r.#'le've&.c.$e $rt.v&derhe+e&E+r.#'le've&.c.$e (. *&*&- derhe+e&)
;itert'r te&t&+ $ir stli&+ me&+'&+#%#& h&y $e$er% l%or& $er'r's& de&+& %er'$h& se&sori# y&+ se$e&r&y selm $ir 0308-816 / - meliht hl de%& : 2005 lsevier ;td ll ri+hts reserved. doi=101016 / .!oodchem.2005.01.006
Ge&yim%&& l+liesh (1977) me&++m$r#& %er'$h& y&+ %li&+ ri&ci. m'& l+liesh %lot (m$r. 1) mer'%#& +e&erlissi dri evol'si se&sori# selm 'si $ir %e&yim%&& y&+ d& tid# $errti $erl#' '&t'# seti% $ir. Ge&'r'&& #o&st&t #e%hit& dimti selm %e&'&. l i&i se$+i& dise$$#& ms#i&+ se&sori# de&+& de&+& %e&i&+#t %e&i&+#t& & rs m&is. er$ed er$ed de&+ de&+& & %erce%t %erce%t&& wl %em$&+'&& %em$&+'&& m&is rom %em$e&t'#& %em$e&t'#& #rmel $'r&t- +'l d& rom %erme&-se%erti ('+ dise$'t #sr) CB $erte%t& de&+& %e&i&+#t& rs m&is. eli& it' !ormsi y&+ s&+t ce%t % y&+ di+m$r#& se$+i "i$es rs dimti. he "i$es mer''# %d $' y&+ #hs dri d'& $lc#c'rr&t ("i$es ("i$es &i+r'm). etelh-$&+sl etelh-$&+sl i&te&sits i&te&sits "i$es rs rs me&'r'&. @e&'r't l+liesh (1977) #rd's rs $&+& o%s setelh rom "i$es. i sisi li& me&'r't @eil+rd (1972) #rd's rs li%t& ter's di- me&c%i m#sim'm dii#'ti oleh %e&'r'&&. @e&di- sisi tem'& 'm'm li&&y mel%or#& %er'$h& dlm rs y&+ #ers setelh-%hit d& ctt& stri&+e&t stri&+e&t dlm rs (;ewis G&+$or& A &&o &&o 197) d& ctt& &++'r-d& wis#i-se%erti dlm $ir s&+t $er'si (rost *& erde oe#str A strti&+ 1971). tri$'t rs %ositi! $ir se%erti $'h / stery d& rom $'&+ ce&der'&+ me&'r'& i&te&sits&y. &t'# #es& #esel'r'h& %e&'r'&& rs %ositi! m'&+#i& t&t se%erti im%or- %e&+em$&+& rs $si (m!orth 1999$4 Hhiter Crr Cr$$ A c>'es 1979). eri&+#li $ir stli&+ disi#& se$+i h&y me&di ter#it de&+& #rd's %e&+em$&+& rs. eme&tr dlm $e$er% #s's d& ter'tm di $ir l+er #rd's rs dlh m&i!estsi 'tm $ir stli&+ i&i tid# d%t erli?ed +e&-. Ge&'& rs $ervrisi &tr e&is $ir d& te&t' '&t'# $ir #h's's rs $si li& dri- se%'l'h le$ih me&o&ol. Hhiter (1981) mel%or#& ctt& %e&'& dri le #'t se%erti ter$#r l#ohol #rmel $ers li>'od& rs stri&+e&t sed&+#& #rto& d& lo+m rs tid# ditem'#&. eli& it' #'t i&isisi 3#$ B% &anderhaegen &anderhaegen et al% ' (ood )he*istr+ # 2./ 3# 0-3$!
ese&sil di$#r rs di $ir +el% d%t me&'t'%i %em$&+'&& rs %e&'& d& me&+hsil#& st$ilits rs y&+ le$ih $i# dri e&is $ir i&i. m'& se%erti y&+ #& diels#& le$ih l&'t %d !#tor li& m'&+#i& '+ me&els#& %e&+mt& i&i.
3%!% 1eneral
Flvo'r #er's#& dlh hsil dri #ed' re#si %em$e&t'#& d& de+rdsi. Gem$e&t'#& mole#'l %d
#o&se&trsi di ts m$&+ $ts rs msi&+-msi&+ me&+rh e!e# terliht $r' seme&tr de+rdsi mole#'l '&t'# #o&se&trsi di $wh m$&+ $ts rs d%t me&ye$$#& hil&+&y wl rs $ir se+r. el&'t&y i&ter i&ter#si #si &tr &tr volti voltill rom rom y& y&++ $er$ed $er$ed d% d%t t me&i&+ me&i&+#t #t#& #& t' t' me&e# me&e#&& dm%# dm%# rs rs dri dri +elo$ +elo$&+ &+ (@eil+rd 1975). Rasa pahit Ribes manis aroma ytisnetn I & toffee-seperti Sweet aroma rasa dan rasa karton rasa
m$r. 1. Ger'$h& e&sory selm $ir %e&'& me&'r't l+liesh (1977). Waktu
3%2% Sen+awa volatil 3%2%!% Analisis
e&+& di%er#e&l#&&y #romto+r!i +s %d th'& 1960 me&di m'&+#i& '&t'# mem%elri %er'$h& voltil $ir selm %e&yim%&&. Gd #hir 1960-& $e$er% st'di (hre&st-;rse& A ;evi& &se& 19634 &+& 19694 mieso& Che& A *& hel'we 19694 rchm& A let& 19694 vo& ?ilvi&yi A G' GJ < 1969) mel%or#& %em$e&t'#& se&yw y&+ $erh'$'&+& stli&+. $el 1 me&'&'##& #lsi!i#si voltil st i&i di#e&l se$+i ter#it de&+& %er'$h& #o&se&trsi selm $ir %e&'&. lm $e$er% th'& ter#hir te#&i#-te#&i# $r' se%erti &lisis rom e#str#si %e&+e&cer& () telh di#em$&+- #& '&t'# me&+evl'si relev&si voltil terdete#si %erse%si $' dlm m#&&. (elit? A rosch 1999). e&+& me&++'&#& metode i&i $e$er% se&yw stli&+ telh diide&ti!i#si dlm $ir (is Chev&ce er#ovic A Colli& 20024 chie$erle 19914 chie$erle A
ri wl %e&eliti& te&t&+ se&yw stli&+ #r$o&il %li&+ me&ri# %erhti&. e&yw-se&yw terse$'t y&+ di#eth'i di#eth'i me&ye$$#& me&ye$$#& %er'$h& %er'$h& rs dlm dlm %rod'# %rod'# m#&& m#&& se%erti se%erti s's' me&te+ me&te+ sy'r& sy'r& d& mi&y#. mi&y#. shimoto (1966) dlh or&+ %ertm y&+ mel%or#& %e&i&+#t& l'r $is dlm ti&+#t #r$o&il m'dh me&+'% dlm $ir selm %e&yim%&& secr %rlel de&+& %er#em$&+& rs $si. ldehid cet- dlh slh st' se&yw %ertm y&+ %e&i&+#t& #o&se&trsi dimti %d 'm'r $ir (& +& 1969) d& %e&eliti& le$ih l&'t (@eil+rd li?o&do A @oy 19704 @eil+rd A @oy 19704 Glm&d A rdwic# 1969 ) %d l#&ls d& l#e&ls me&+'&+#%#& %ote&si rs ti&++i dlm $ir. lm #o&te#s it' Glm&d d& rdwic# (1969) %ertm #li diels#& () -2-&o&e&l se$+i mole#'l y&+ %d eli& $ir me&+i&d'#si %%& rs #rt'-miri% de&+& rs se%erti dlm $ir $er'si. eth'& #em'di& ide&ti!i#si dlm $ir dism#& di%&s#& dri () -2&o&e&l oleh mieso& d& *& hel'we (1970) se$+i mole#'l y&+ $ert&++'&+ w$ '&t'# #rto& mim%im' !l- di&++% se$+i tero$os& dlm $ir rs re B % &anderhae &anderhaegen gen et al% ' (ood )he*istr+ )he*istr+ # 2./ 3#0-3$! 3#
%e&cri. lm th'&-th'& $eri#'t&y %e&eliti& li& (rost et l 19714. @eil+rd ym ym A "'&o 19714 Hohle$ e&- &i&+s A ;ewis 1972) me&e+s#& hsil tet%i sem' re- !erred '&t'# di%&s#& d& dism#& (G2 ) $ir.
%e&eliti& li& (ree&ho!! A Hheeler 19814 ree&ho!! A Hheeler 1981$4 shimoto A shim 19774 mieso& A Che& 19724 te&roos H&+ ie$ert A @eil+rd 1976) %d ldehid dlm $ir te#&i# &lisis y&+ sm $erdsr#& #r$o&il 2-di&itro!e&ilhidr?o& !ormsi tio& di+'&#& d& mes#i%'& te#&i# isolsi y&+ $is&y $er$ed mere# mem$e&r#& %e&i&+#t& () -2- &o&e&l d& li&&y li&ier C
-C 10
l#e&ls d& l#&ls dlm $ir selm %e&yim%&&. <re& sem#i& %e&ti&+&y () -2-&o&e&l d& #r$o&il li&&y dlm $ir $er$+i te#&i# telh di's'l#& '&t'# me&+'#'r #o&se&trsi mere# dlm $ir. &y# metode tet% $erdsr#& vtistio& deri- dri #r$o&il '&t'# me&+'r&+i +&++'& y&+ dise$$#& oleh mtri#s $ir. +e& derivtissi se%erti o- (2356-%e&t!l'oro$e&?yl) hydroylmi& (GFJ) (ro &>vist iiril *irt&e& ome A G'&e& 19934 Jl
#r$o&il de&+& distilsi v#'m dii#'ti oleh C-@ &lisis (;erm'sie' oel ;ie+eois A Colli& 1999) t' destilsi '% e#str#si !se %dt d& dete#si G;C-* iso#rti# (&tos et l. 2003) . #re& mieso& d& *& hel'we (1970) dri %'$li#si hr%& y&+ ti&++i y&+ () -2-&o&e&l d%t di&++% se$+i mole#'l y&+ $ert&++'&+ w$ '&t'# $ir stli&+ d& metode '&t'# me&+'r&+i #o&se&trsi #& !i #hir&y memech#& mslh $ir stli&+. m'& di-&y $el 1 B#htisrdri se&yw voltil st i&i di#e&l ter$e&t'# selm %e&yim%&& $ir #els
li%t& selm %e&yim%&& tid# $errti di m&-m&. @e&'r't *& erde d& strti&+ (1981) () -2-&o& &l me&i&+#t %d 0 I C di $e$er% $ir dlm $e$er% hri #e ti&+#t di ts m$&+ $ts sed&+#& %d 20 I C i&i tid# ditem'#& $h#& setelh $'l& %e&yim%&&. e$'h s'lt re- ser'% di%eroleh r?iss @ied&er d& r! (1985). eli& it' %'$li#si ter$r' (Foster m%dori A Gti&o 20014 r?iss @ied&er A ;'sti+ 19994 chie$erle A
me&ye$'t#& d %e&i&+#t& y&+ si+&i!i#& dlm () co& -2-&o&e&l se&trsi selm $ir %e&'&. e$li#&y %e&'lis li& (;erm'sie' et l 19994. ;ie+eois @e're&s dot A Colli& 20024. &tos et l 2003) ter's mel%or#& %em$e&t'#&&y d& %e&+mt& $hw it' terdi secr i&de%e&de& dri #o&se&trsi o#si+e& dlm $otol $ir (r?iss et l 19854. oel et l 19994. Hlters esm& A '+hes 1997$). @es#i%'& l%or& tm%#&y $erte&t&+& terse$'t d i&di#si $hw $e$er% se&yw #r$o&il y&+ %e&ti&+ dlm rs stli&+. Ger&yt& i&i $is diil'strsi#& oleh demo&strsi shimotoLs (shimoto 1981) $hw %em'l'&+ #r$o&il se%erti hydroylmi&e se+er me&+'r&+i s%e#-s%e# terte&t' dri mim%im' !l- %e&'& dlm $ir(). ldehid li&er li&&y memili#i si!t rs miri% de&+& - 2-&o&e&l (@eil+rd 1975$).
-C 10
l#&ls l#e&ls d& l#edie&ls dlm $ir %e&'& telh di%elri %d ti&+#t le$ih re&dh. lm se$'h st'di dri ree&ho!! d& Hheeler (1981 1981$) ti&+#t sem' li&ier C
-C 10
2-l#e&ls sem#i& me&i&+#t. ecr #h's's r&ti %&&+ 2l#e&ls m'li dri 2-he%te&l melm%'i m$&+ $ts mere# selm %e&yim%&& $ir. &y r&ti li&er l#&ls %e&de#4 $'t&l %e&t&l d& he#s&l secr si+&i!i#& ter$e&t'#. ry- m yse d& <to (199) mel%or#& $hw &ls l#edie- ( M) -26-&o&die&l d& ( ) -2-decdie&l t#e $+i& dlm rs stli&+. ldehid li&&y ter$e&t'# selm %e&yim%&& $ir y&+ dise$'t trec#er ldehid= (. Hheeler Gr+&ell A Gierce 19714 ohm&& 1985$4 *esely d## 2003) 2-metil-%ro%&l 2-metil-$'t&l (@ied&er &r- MB A ichhor& 19914 *esely d## 2003) $'t&l 3-metil (@ied&er et l 19914.. *esely d## 20034. Hheeler et l 1971) $e&?ldehid (@ied&er et l. 1991.4 .. Hheeler et l 1971) %he&ylcetldehyde (@ied&er et l 19914. *esely d## 2003) d& meth- io&l (is et l 20024. *esely d## 2003).. m'm&y #o&se&trsi mere# me&i&+#t le$ih %d #o&se&trsi o#si+e& ti&++i (ohm&& 19854. @ied&er et l 19914. r?iss et l 1985). $ir $er'si 'l&+ veled y&+ methio&l (dims# #e&t&+-se%erti) (is et l 20024. chie$erle A
#eto& y&+ #o&se&trsi me&i&+#t de&+& 'si $ir 3-metil-$'t&-2-st' d& -metil%e&t&-2-o&e (shimoto A <'roiw 19754 ;'sti+ @ied&er &r- MB A H. 1993) d& di#eto&es vici&l4 dicetyl d& 23-Ge&t&edio&e. B&i #& le$ih %rh %d ti&+#t o#si+e& y&+ le$ih ti&++i d& dicetyl $h#& m'&+#i& melm%'i m$&+ $ts rs &y (Hheeler et l. 1971). 3%2%3% Asetal siklik
er'tm #eti# $ir dlm #o&t# de&+& o#si+e& setl si#li# 25-trimetil-13-diool&e 2-iso%ro- GN;-5dimetil-13-diool&e 2-iso$'til -5-dimetil-13-diool&e d& 2-sec-$'til-5-dimetil-13-dioo- l'r me&i&+#t
selm %e&yim%&& (*&derhe+e& et l. 2003$). m$&+ $ts rs 900 l+ / l d& #o&se&trsi m#sim'm dlm $ir se#itr 100 l+ / l dil%or#& '&t'# 25-trimetil-13-diool&e (Ge%%rd A lsey 1982). 3%2%% Sen+awa heterosiklik
se&yw heterosi#li# $e$er% de&+& tio&s #r$o&il !'&+si mew#ili #elom%o# $esr se&yw t'&d'# %d %er'$h& #o&se&trsi selm $ir %e&'&. he ti&d# i&+ !'r& ter$e&t'# (;'sti+ et l 19934 @di+& Gere? A Cleme&ts 19984 *rm'? tei&er li&s&er A
#o&se&trsi$e$er% %ir?i& me&'r'& s&+t ce%t (%yr?i&e 2- etil-6-methyl%yr?i&e 2-etil-5-methyl%yr?i&e) d& $e$er% $h#& hil&+ sm se#li (2-cetyl%yr?i&e 2 3- dimethyl%yr?i&e 25-dimethyl%yr?i&e 2-etil-36dimethyl%yr?i&e 2-etil-35-dimethyl%yr?i&e).
ester *oltile mem%er#e&l#& ctt& rs $'h d& di&++% tri$'t rs y&+ s&+t %ositi! dri $ir se+r. sett isomil di%rod'#si oleh r+i misl&y mem$eri#& rs %is&+ se%erti. m'& selm %e&yim%&& co&ce&trtio& dri ester i&i d%t me&'r'&#& ti&+#t di $wh ti&+#t m$&+ $ts (eve& elv' A erdeli&c# 19974 te&roos 1973). N&+ me&+hsil#& mim%im' !l- $'h $er#'r&+ $ir e$li#&y terte&t' ester voltil (etil 3-metil $'tirt etil 2-metil-$'tirt etil %ro%io&t 2-metil etil &icoti&te dietil s'#si&t etil l#tt etil %he&ylcette etil !ormte etil !'ro- m#& d& etil si&mt) disi&tesis selm $ir %e&'& (ohm&& 1985$4. is et l 20024 ;'sti+ et l 19934.. @ied&er et l 19914 Hillims A H+- &er 1978). Hillims d& H+&er (1978) ter#it %em$e&t'#& etil 3-metil-$'tirt d& $'tirt 2-metil '&t'# %e&+em$&+& rs m$'#. Ge&ti&+&y mole#'l-mole#'l '&t'# rs $ir $er'si '+ $r'-$r' dil%or#& me&++'&#& <B %e&+lm&- (chie$erle A
e&yws'l!'r 'm'm&y memili#i m$&+ rs s&+t re&dh dlm $ir d& #o&se&trsi #ecil %er'$h& m'&+#i& memili#i e!e# y&+ &yt %d rs. i- metil tris'l!ide (se+r $w&+-se%erti) $is me&i&+#t sm%i di ts m$&+ $ts rs &y 01 l+ / l (is et l 20024. is Ger%ete immerm&s A Colli& 20004 Hil- ;ims A rcey 1982) . #s%erime& veled 'l&+ y&+ '+ 3-metil-3-merc%to$'tyl !ormt (#ti "i$es) (chie$erle 1991) y&+ terli$t. "i$es mole#'l li& rs ter#it dlm $ir $er'si dlh -merc3.2 B% &anderhaegen et al% ' (ood )he*istr+ # 2./ 3# 0-3$!
%to--metil-%e&t-2-o&e (ressl hri A
se&yw &o&-voltile dlm $ir d%t me&di %e&ti&+ '&t'# rs d& mo'th!eel. . Ger'$h& #o&se&trsi #re& d%t me&ye$$#& %er'$h& se&sori# %e&ti&+ Bso--sm ?t %hit 'tm dlm $ir s&+t se&siti! terhd% de+rdsi selm %e&yim%&& (e Coom& erts Jvermeire A e
%oli!e&ol di#it#& de&+& m'&c'l&y #ers / seler stri&+e&t. &y d $e$er% l%or& ter#it %e&yim%&& %er'$h& $ir sm mi&o. ecr 'm'm sedi#it %e&'r'&& dimti dri $e$er% i&divid' mi&o-sm (srov - vel &o'se# A Ci?#ov 1999) d& +l'tmi&e telh di's'l#& se$+i %e&&d stli&+ (ill ;'sti+ A wt?#i 1998). 3%% Asal ki*ia bir rasa kerusakan
e$'h meliht le$ih de#t %d %er'$h& &t #o&stit'si #imi %e&'& $ir me&+'&+#%#& #om%le#sits $esr dri !e&ome& $ir stli&+. wl it' is'msi#& $hw ter'tm () -2-&o&e&l $ert&++'&+ w$ ts %er'$h& se&sori# t%i se#r&+ els $hw se+'d&+ se&yw rs $ert&++'&+ w$. e$'h rs $si di&++% hsil dri re#si %em$e&t'#& d& de+rdsi. e&+& $e$er% se&yw $r' memili#i l si% ditem'#& mes#i%'& msih di%erl'#& '&t'# mem%elri si!t rs-mem%e&+r'hi mere# me&++'&#& e#s%erime& i&+ s%i#- d& evl'si se&sori#. m$r& dri re#si #imi y&+ terli$t dlm $ir stli&+ d%t mem$&t' '&t'# le$ih memhmi !e&ome& $ir-%e&'&1988..4
ed et l chid A J&o 19964 chid A J&o 1999) d& chemil'mi&esce&ce (C;) (<&ed <&o Jsw <w#ishi A
c'#'% st$il d& tid# #& m'dh $ere#si de&+& mole#'l or+&i#. lm
Q d& $ir tid# dlm #esetim$&+& #imi. hermody&mid& C' D dio#sidsi '&t'# C'2 D (<&ed
Q. lm $ir &io& i&i m'dh
#o&se&trsi d& s'h' %e&yim%&&. Bcls hidro+e& (J-) #em'di& d%t %ero#sid ( 2
J 2). idro#sil dihsil#& dri 2
J 2
" %2% Spesies oksigen reakti4 dala* disi*pan bir
J#si+e& #h's's&y me&ye$$#& %e&'r'&& y&+ ce%t dri $ir rs y&+ $errti $hw o#si+e& hr's mem'li $e$er% re#si %e&'& y&+ s&+t %e&ti&+. Ge&ti&+&y s%esies o#si+e& re#ti! ("J) dlm $ir stli&+ dlh-i&divid' %ertm $erdedi#si oleh m!orth d& Grso&s (1985). lm $e$er% th'& ter#hir %e&eliti& me&++'&#& reso&&si s%i& ele#tro& (") de&+& re+e& $er%'tr tr%%i&+ (&derse& A #i$sted 19984 <&ed <&o
2 3O 2 pKa 16-18 pKa 11.6
OH + OH + OHFe2+ Fe3+ Fe2+ Fe3+ O
2 →
Fe2+ + O 2 - + 2H+
O 2 -
O 2 2Net: 2H 2 O 2 OH + OH- + O 2 - + 2H+ Reaction B:Haber-Weiss reaction pKa 4.5-4.9 Fe3+ + O2→
Fe2+ + O 2
HO 2
HO Fe2+ + H 2 Net: O2- + H 2 O H 2 2 O →
2
→O Fe3+ 2
+ + OH OH + OH- Reaction A + OHFe2+ Fe3+
O 2 Fe2+ Fe3+ Reaction B
Fi+. 2. "ectio&s %rod'ci&+ rective oy+e& s%ecies ("J) i& $eer (<&ed et l. 1999). B% &anderhaegen et al% ' (ood )he*istr+ # 2./ 3#053$! 3.3
%rocess $'t c& $e !ormed !ter de!i&ite time %eriod clled the UUl+ timeUU o! !ree-rdicl +e&ertio& (chid A J&o 19964 chid '+ A J&o 1996). he UUl+- timeUU seems relted to the e&do+e&o's &tioid&t ctivity o! $eer &d c& $e 'sed s & o$ective tool !or its evl'tio&. ydroyl rdicls re o&e o! the most rective s%ecies tht hve $ee& ide&ti!ied. here!ore it ws s'++ested tht they &o&-selectively rect with eth&ol i& $eer $e- c'se it is the seco&d most $'&d&t com%o'&d o! $eer &d +ood rdicl scve&+er. he !i&di&+s o! &derse& &d #i$sted (1998) which reveled the 1-hydroyethyl rdicl s >'&tittively the most im%ort&t rdicl i& $eer s'%%ort this. he 1-hydroyethyl rdicl rises i& the rectio& o! eth&ol with the hydroyl rdicl. e&- erlly the &d J-) rective oy+e& s%ecies (JP 2 JJ- 2
J 2 rect with ll #i&ds o! or+&ic molec'les i& $eer s'ch s %oly%he&ols isoh'm'lo&es &d lcohols res'lti&+ i& vrio's ch&+es i& the se&sory %ro!ile o! $eer. %3% Aging rea6tions produ6ing 6arbon+l 6o*pounds %3%!% 7*portan6e o4 6arbon+l *e6hanis*s
oo& !ter the im%ort&ce o! cr$o&yl com%o'&ds !or $eer stli&+ ws reveled %thwys !or their !orm- tio& were s'++ested. From the $e+i&&i&+ rectio& mech- &isms ledi&+ to ()-2-&o&e&l hve $ee& the !oc's o! this reserch. @&y ro'tes hve $ee& st'died i& $eer model systems &d it there!ore remi&s di!!ic'lt to tell to wht ete&t %rtic'lr rectio& mech&ism is rele- v&t '&der &orml stor+e co&ditio&s. %3%2% 89idation o4 higher al6ohols
he most im%ort&t lcohols i& $eer re eth&ol 2- methyl-%ro%&ol 2-methyl-$'t&ol 3-methyl-$'t&ol &d 2 %he&yl-eth&ol. *rio's reserchers hve re- %orted tht the co&ce&trtio&s o! the corres%o&di&+ ldehydes i&crese d'ri&+ $eer +i&+ i& %rtic'lr whe& oy+e& ws %rese&t (see $ove). shimoto (1972) st'died the i&cresed !ormtio& o! ldehydes d'e to e%os're o! $eer to hi+her oy+e& lev- els. i+h tem%ert'res low % &d the s'%%leme&ttio& o! dditio&l hi+her lcohols to $eer led to hi+her co&ce&trtio&s o! ldehydes. @oreover direct oidtio& o! lcohols $y molec'lr oy+e& ws &ot %ossi$le i& $eer model systems '&less mel&oidi&s were %rese&t. rec- tio& mech&ism ws %ro%osed i& which lcohols tr&s!er electro&s to rective cr$o&yl +ro'%s o! mel&oidi&s. @olec'lr oy+e& ccelertes the oidtio& o! the lco- hols %ro$$ly $ec'se the mel&oidi&s re tr&s!ormed i& s'ch wy tht the rective cr$o&yl +ro'%s re i&- volved i& the electro&-tr&s!er system. evre' loc#m&s &d v&de @eersche (1981) do'$ted the im%ort&ce o! this %thwy s they o$- served the re>'ireme&ts o! li+ht &d i&hi$itio& $y low 3. B% &anderhaegen et al% ' (ood )he*istr+ # 2./ 3# 053$!
co&ce&trtio&s o! %oly%he&ols. F'rthermore the rec- tivity o! lcohols decreses with their molec'lr wei+ht. Brwi& r#er &d Gi%sts (1991) !o'&d this %thwy irrelev&t i& the !ormtio& o! ()-2-&o&e&l $ec'se o! the very low e!!icie&cy (0.2V) o! 2-&o&e&ol to &o&e&l co&versio& i& model systems. oðeless it ws rece&tly re%orted tht the 1-hydroyethyl rdicl is >'&tittively the most im%or- t&t rdicl i& stle $eer d'e to hydroyl rdicls rect- i&+ with eth&ol (&derse& A #i$sted 1998). mi& de+rdtio& %rod'ct o! the rdicl is cetldehyde (Fi+. 3). ve& tho'+h eth&ol is more $'&d&t i& $eer th& &y other or+&ic molec'le "J my rect i& similr m&&er with the mi& hi+her lcohols. From this %ers%ective the !ormtio& o! "J &d their rectio& with lcohols c& $e re+rded s +e&erli?tio& o! the rectio& mech&ism %ro%osed $y shimoto (1972). %3%3% Stre6ker degradation o4 a*ino a6ids
mi&o cids i& stored $eer my $e so'rce o! lde- hydes. loc#m&s evre' &d @sschelei& (1975) o$served & i&cresed !ormtio& o! 2-methyl-%ro%&l &d 3-methyl-$'t&l whe& either vli&e or le'ci&e were dded to $eer &d oy+e& ws %rese&t. he rectio& ws ctlysed $y Fe &d C' io&s. his ws e%li&ed $y trec#er rectio& $etwee& mi&o cids &d -dicr- $o&yl com%o'&ds (Fi+. ). he rectio& i&volves tr&s- mi&tio& !ollowed $y decr$oyltio& o! the s'$se>'e&t -#etocid res'lti&+ i& & ldehyde with o&e cr$o& tom less th& the mi&o cid. dditio&l -dicr$o&yl com%o'&ds i& $eer re %os- si$ly !ormed $y the @illrd rectio& the oidtio& o! red'cto&es or the oidtio& o! %oly%he&ols. h'm @ied&er r?iss &d lc# (1995) me&tio& tht trec- #er de+rdtio& is o&ly im%ort&t t stro&+ly i&cresed mi&o cids co&te&ts $'t &ot t the mi&o cid co&ce&- trtio&s &ormlly %rese&t i& $eer (W1 +/l). %3%% Aldol 6ondensation
shimoto &d <'roiw (1975) s'++ested tht ldol co&de&stio& o! cr$o&yl com%o'&ds is %ossi$le '&der the mild co&ditio&s eisti&+ i& $eer d'ri&+ stor+e. For em%le ()-2-&o&e&l ws !ormed $y ldol co&de&s- tio& o! cetldehyde with he%t&l i& model $eer stored !or 20 dys t 50 IC &d co&ti&i&+ 20 mmol/l o! %roli&e (Fi+. 5). B& these rectio&s the mi&o cids my $e the $sic ctlysts thro'+h the !ormtio& o! & imi&e i&termedite. his %thwy c& %rod'ce cr- $o&yl com%o'&ds with lower !lvo'r thresholds !rom cr$o&yls %rese&t i& $eer which re less !lvo'r ctive &d which c& $e !ormed $y other %thwys. ltho'+h the ldol co&de&stio& %thwy seems %l'si$le it is &ot cler whether the mo'&ts o! rectio& %rod'cts re s'!!icie&tly hi+h to rech threshold co&ce&trtio&s '&der &orml $eer stor+e co&ditio&s (m!orth 1999$).
%3%#% :egradation o4 hop bitter a6ids
he de+rdtio& o! ho% $itter cids (iso--cids - cids &d $-cids) &ot o&ly decreses se&sory $itter&ess $'t lso res'lts i& the !ormtio& o! %rod'cts. here re B% &anderhaegen et al% ' (ood )he*istr+ # 2./ 3#053$! 3.# ethanol acetaldehyde
! ! H" #H $ #H "H #H $ %' ($' #H"H #H #H #H " " "" #H $ "H #H $ "" H"#H bimo)ecu)ar reactions
Fi+. 3. "ectio& o! eth&ol with the hydroyl rdicl i& $eer ccordi&+ to &derse& &d #i$sted (1998). R# #H" H""
#H "H H"#H #H" #H "" H " H""
Strecker degradation of amino acids amino acid ## * R #""H H #""H "" *H "H # # # " H * #""H # # "H # " R ##
*H
Strecker aldehyde a-di carbonyl compound
Fi+. . Formtio& o! ldehydes i& $eer $y trec#er de+rdtio& o! mi&o cids (h'm et l. 1995). R# #""H " R #H" "H R " #"
Formation of dicarbonyl compounds Amino acid ! Su+ar Amadoi eaan!ement "H ## "" R "H R, "H " " "
i&dictio&s tht some o! them re i&volved i& the %%er&ce o! +i&+ !lvo'rs. B&deed shimoto &d shim (1979) re%orted tht $eer $rewed witho't ho%s hrdly develo%s ty%icl stle !lvo'r eve& !ter lo&+ ! !!! ! other minor byproducts "H #H #H "H
shel! stor+e. he ect de+rdtio& mech&ism !or ho% cids &d the chemicl str'ct'res o! the voltiles !ormed hve &ot $ee& com%letely el'cidted. r. 6 %rese&ts the str'ct're o! the most im%ort&t $eer ho% $itter cids. Bso--cids >'ic#ly de+rde i& the %rese&ce o! "J (<&ed et l. 1989) the tr&s-isomer $ei&+ m'ch more se&sitive th& the cis-isomer (e Coom& et l. 2000). owever rece&t reserch ('vere et l. 2003) i&di- ctes tht electro&s re relesed !rom iso--cids i& the %rese&ce o! s'it$le electro& cce%tors which do &ot &ecessrily re>'ire the i&volveme&t o! oy+e& s%ecies. s res'lt oy+e&- &d cr$o&-ce&tred rdicls re !ormed. hese rdicls re very rective &d led to %rod'cts o! vryi&+ &t're4 however ll lc# the tricr- $o&yl chromo%hore. he do'$le $o&ds i& the side-chi&s o! the ho% cids re less rective towrd oidtio& th& ws commo&ly tho'+ht. Bt is &ow cler tht iso--cids c& $e s'$ect to oidtive-ty%e de+rdtio& i& the $se&ce o! molec'lr oy+e&. he red'ced side-chi& iso--cids 'sed to im%rt li+ht resist&ce hve !ewer str'ct'rl %ositio&s se&sitive to rdicl !ormtio&. Co&se>'e&tly they show more resist&ce to oidtive $re#dow&. ccordi&+ to shimoto &d shim (1979) voltile de+rdtio& %rod'cts o! iso--cids i& $eer model sys- tems re cr$o&yl com%o'&ds with vrio's chi& le&+ths s'ch s C 3
to C 11
2-l#&o&es C 2
to C 10
l#- &ls C
to C 7
2-l#e&ls &d C 6
to C 7
2-l#edie&ls. B& & erlier st'dy (shimoto A <'roiw 1975) ceheptanal acetaldehyde
amino-acid amino-acid (E)-2-nonenal
Fi+. 5. Formtio& o! ()-2-&o&e&l i& $eer $y ldol co&de&stio& o! cetldehyde &d he%t&l ccordi&+ to shimoto &d <'roiw (1975). 3.. B% &anderhaegen et al% ' (ood )he*istr+ # 2./ 3# 053$!
"# " H #
! #H $ # H "H "H H#H # * R #H #""H "H H "H #H "#H # H
to&e 2-methyl-%ro%&l 3-methyl-$'t&-2-o&e - methyl-%e&t&-2-o&e &d 2-methyl-3-$'te&-2-ol were lso ide&ti!ied s oidtio& %rod'cts. @oreover Hil- lims &d H+&er (1979) showed tht de+rdtio& o! the cr$o&yl side-chi& o! -cids &d $-cids releses 2-methyl-%ro%io&ic cid 2-methyl-$'tyric cid &d 3- methyl-$'tyric cid. s will $e e%li&ed lter these cids re %rec'rsors i& the !ormtio& o! stli&+ esters. .3.6. Jidtio& o! '&st'rted !tty cids .3.6.1. e&erl mech&isms &d i&termedites. From the strt o! reserch o& $eer stli&+ the oidtio& o! '&st- 'rted !tty cids received more tte&tio& th& &y other rectio&. oo& !ter the crd$ord !lvo'r o! $eer ws li&#ed to ()-2-&o&e&l !ormtio& it ws s'++ested tht its !ormtio& &d tht o! other st'rted &d '&st- 'rted ldehydes ws d'e to li%id oidtio& (le A Golloc# 19774 rost et l. 19714 mieso& A *& he- l'we 19704 ressl hri A ilwr 1979). his ws cer- ti&ly relted t tht time to the ete&sive reserch &d #&owled+e o! the oidtive $re#dow& o! li%ids i& !oods ledi&+ to cr$o&yl com%o'&ds &d r&cidity. B& $eer &d wort the o&ly li%id s'$strtes o! si+&i!ic&ce re li&oleic cid (C18=2) &d li&ole&ic (C18=3) cid ris- i&+ !rom mlted $rley. hese cids re mi&ly relesed !rom tricyl+lycerols $y the ctivity o! $rley &d mlt li%ses (ter 198). 'ri&+ mlti&+ sli+ht ch&+es i& !tty cids &d li%id com%ositio& occ'r. ydrolysis "" " " "H " "H "H " "H R R
α-acid β-acid trans-iso-α-acid cis-iso-α-acid
R aR b R c " " "H " #H#H $ " " "H " R R "H . / . #H #H#H $ / . #H#H $ /#H #H $
Fi+. 6. @ost im%ort&t ho% $itter cids i& $eer.
o! tricyl+lycerols to !tty cids occ'rs mi&ly d'ri&+ mshi&+. @lt li%se remi&s ctive thro'+h m'ch o! the mshi&+ %rocess (chwr? t&ley A ol$er+ 2002). t %rese&t there is stro&+ evide&ce tht li%id oid- tio& does &ot occ'r i& $eer !ter $ottli&+. ()-2-&o&e&l is relesed !rom other %rec'rsors i& &o&-oidtive %rocess s the oy+e& co&ce&trtio& o! $ottled $eer does &ot i&!l'e&ce the ()-2-&o&e&l relese (;er- m'sie' et l. 19994 oel et l. 1999). Jidtio& i&termedites o! li&oleic cid trihydroy !tty cids hve $ee& i&vesti+ted s %ossi$le %rec'rsors (rost et l. 19714 rvel&d Gesm& A *& erde 1972). owever they co&vert to ()-2-&o&e&l o&ly i& cidi!ied $eer (% 2) th's ecl'di&+ them s %l'si$le %rec'rsors i& $eer (te&roos et l. 1976). e&erlly it is &ow +reed tht d'ri&+ wort %rod'c- tio& e&?ymtic &d &o&-e&?ymtic oidtio& mi&ly o! li&oleic cid +e&ertes UU()-2-&o&e&l %ote&tilUU i&iti- ti&+ the ()-2-&o&e&l !ormtio& d'ri&+ $eer stor+e. rost v& de& er+ Freiee v& der *elde &d olle- m&s (1990) de!i&ed the &o&e&l %ote&til s the %ote&- til o! wort to relese ()-2-&o&e&l !ter its tretme&t !or 2 h t 100 IC t % .0 '&der & r+o& tmos%here. oe l &d Colli& (1995) !o'&d stro&+ evide&ce tht ()-2-&o&e&l i& wort !orms chi!!Ls $ses (imi&es) with mi&o cids or %rotei&s which %ss i&to $eer. 'ri&+ stor+e ()-2-&o&e&l is the& relesed &d this is e&- h&ced t low % (;erm'sie' et l. 1999). UUFreeUU ()-2-&o&e&l i& wort is red'ced to &o&e&ol $y yest !er- me&ttio& &d &o&e&ol is &ot si+&i!ic&tly re-oidi?ed d'ri&+ $eer stor+e (Brwi& et l. 1991). here hs $ee& some de$te $o't whether ()-2- &o&e&l is similrly relesed !rom &o&-voltile $is'l!ite dd'cts d'ri&+ stor+e. he s'l!ite !ormed $y yest d'r- i&+ !erme&ttio& wo'ld !orm reversi$le dd'cts with ()-2&o&e&l (r#er rcey Brwi& Gi%sts A ;eis# 1983). 'l!ite c& dd o& to the cr$o&yl !'&ctio& &d o& to the do'$le $o'&d o! ()-2-&o&e&l. s d'ri&+ stor+e the s'l!ite co&ce&trtio& +rd'lly decreses the ()-2-&o&e&l wo'ld $e relesed. owever '!o'r ;e's ter &d ym& (1999) rece&tly showed tht while $is'l!ite dditio& to the cr$o&yl !'&ctio& is reversi$le $is'l!ite dditio& to the do'$le $o&d i& ()- 2-&o&e&l is irreversi$le. 'e to the irreversi$le &t're o! the $is'l!ite dditio& to the do'$le $o&d &d the st- $ility o! s'ch dd'cts ()-2&o&e&l c&&ot $e relesed !rom these &o&-voltile s%ecies. his s'%%orts the o$ser- vtio&s o! other 'thors (<&ed #shio Jsw <w#ishi A m#i 19964 ;erm'sie' et l. 1999) descri$i&+ mi&iml !ormtio& o! reversi$le ()-2-&o&- e&l-$is'l!ite dd'cts d'ri&+ !erme&ttio&. he i&crese o! the crd$ord-!lvo'red com%o'&d ()-2-&o&e&l i& +i&+ $eer is th's %ro$$ly li&#ed to oidtio& %rocesses erlier i& the %rod'ctio& %rocess mi&ly i& the $rewho'se. @shi&+ &d wort $oili&+ B% &anderhaegen et al% ' (ood )he*istr+ # 2./ 3#053$! 3.0
re $oth im%ort&t !or the oidtio& o! li&oleic cid &d the s'$se>'e&t relese o! ()-2-&o&e&l. here re two %ossi$le oidtio& ro'tes= 'to-oidtio& or & e&?ymtic oidtio& with li%oy+e&ses (;JK) o&ly d'ri&+ mshi&+ &d mlti&+. here is +ret del o! co&troversy co&cer&i&+ the reltive im%ort&ce o! $oth ro'tes !or ()-2-&o&e&l relese i& !i&ished $eer (m- !orth 19994 te%he&so& iw @ircle A m!orth 2003). his is %rtly relted to the 'se i& $rewi&+ re- serch o! smll-scle e>'i%me&t i& which the oy+e& i&- +ress is m'ch lr+er th& i& i&d'stril scle $rewi&+. "ece&t st'dies (;erm'sie' et l. 19994 ;ie+eois et l. 2002) 'si&+ wort s%i#ed with de'terted ()-2-&o&e&l reveled tht 70V o! the ()-2-&o&e&l relesed d'ri&+ $eer stli&+ ws i&itilly %rod'ced d'ri&+ $oili&+ &d the other 30V d'ri&+ mshi&+. owever these res'lts do &ot ecl'de the %ossi$ility tht some oidtio& i&ter- medites o! !tty cids s'ch s hydroy !tty cids &d hydro%eroy !tty cids %rod'ced $y ;JK d'ri&+ mshi&+ my $e co&verted &o&-e&?ymticlly to ()- 2-&o&e&l '&der the etreme co&ditio&s o! wort $oili&+. .3.6.2. 'to-oidtio& o! !tty cids. 'to-oidtio& o! !tty cid is i&itited $y the $strctio& o! -tom !rom the molec'le $y !ree rdicls. s %revio'sly me&- tio&ed hydroyl rdicls (J-) re ece%tio&lly rec- tive towrd m&y molec'les !o'&d i& !ood. B& the com%le wort e&viro&me&t it is however de$t$le whether hydroyl rdicl c& rech !tty cid $e!ore it !i&ds m'ch more $'&d&t molec'les (e+ s'+rs). here!ore 'tooidtio& is more li#ely to $e i&itited $y the slower-recti&+ %eroy rdicls ("JJ-) $strct- i&+ the most we#ly $o'&d -tom i& the !tty cid. e- sides the %eroy rdicls tht re %rod'ced i& the %thwy (he&ce the 'to-
ctlytic chrcter) %erhydr- oyl rdicls (JJ-) my lso $strct the toms. Hith li&oleic cid the methyle&e +ro'% t %ositio& 11 is ctivted es%ecilly $y the two &ei+h$o'ri&+ do'$le $o&ds (Fi+. 7). e&ce this is the i&itil site !or $strctio& ledi&+ to %e&tdie&yl rdicl which is the& st$ili?ed $y the !ormtio& o! two hydro%eroides t %ositio&s 9 &d 13 (9-;JJ &d 13-;JJ) ech reti&i&+ co&'+ted die&e system. he mo&ollylic +ro'%s i& li&oleic cid (%ositio&s 8 &d 1) lso rect to smll ete&t &d !orm !o'r hydro%eroy cids (8-10- 12- &d 1-;JJ) ech isomer hvi&+ two iso- lted do'$le $o&ds. he %ro%ortio& o! these mi&or hydro%eroy cids is $o't V o! the totl. he hydro%eroy cids c& $e !'rther s'$ect to &o&- e&?ymtic oidtio& or de+rdtio& %rocesses ledi&+ to vriety o! com%o'&ds s'ch s voltiles. everl rec- tio& mech&isms hve $ee& s'++ested to e%li& their !ormtio&. Jhlo!! (1978) %ro%osed & io&ic mech&ism !or the !ormtio& o! ()-2-&o&e&l !rom 9-;JJ &d he&l !rom 13-;JJ i& >'eo's systems (Fi+. 8). heterolytic clev+e is i&itited $y %roto&tio& o! the
hydro%eroide +ro'%. !ter elimi&tio& o! wter mol- ec'le the oo-ctio& !ormed is s'$ected to & oy+e& tom i&sertio& rectio& ecl'sively o& the CSC li&#+e dce&t to the do'$le $o'&d. he cr$e&i'm io& is hydroylted &d the& s%lits i&to & oo-cid &d & ldehyde (2-&o&e&l or he&l). J& the other h&d i& the oil %hse o! some !oods $-clev+e o! hydro%eroy cids is the %redomi&&t de+rdtio& rectio&. Bt i&volves homolytic clev+e with !ormtio& o! short-lived l#oy rdicls. he clev+e !'rther wy !rom the do'$le $o&d is e&er+eticlly %re- !erred si&ce it yields reso&&ce-st$ili?ed com%o'&ds. B& this wy 2-decdie&l is !ormed $y the de+rdtio& o! 9-;JJ. 3.$ B% &anderhaegen et al% ' (ood )he*istr+ # 2./ 3# 053$! 9-hydroperoyoctadeca-!"#!2-dienoic acid (9-$%%&)
Fi+. 7. Formtio& o! the hydro%eroy !tty cids 9-;JJ &d 13-;JJ $y 'toidtio& o! li&oleic cid (elit? &d rosch 1999). hydroperoy fatty acid
"H R( #H #H #H #H #H R H " H ! " " ! H R( #H #H #H #H #H R " ! R( #H #H #H #H #H R R( #H #H #H #H "# ! R H "H R( #H #H #H #H "# R H #H
Fi+. 8. Groto&-ctlysed clev+e o! 9-;JJ &d 13-;JJ hydro%eroy cids o! li&oleic cid ccordi&+ to Jhlo!! (1978). H" " R( #H #H #H #H "H # R
H #H ! R(: R: " R1 CH CH C 9-LOOH 13-LOOH
H / 0 #H $ R(: #H / 1 #""H #H / 1 #""H R: #H / 0 #H $ #H $ #H $ (( #H $ #H / 0 #H #H #H #H #H #H
/ 1 #""H H ($ 2 #H R" R""H " RH R #H $ / 0 #H #H #H #H #H #H / 1 #""H #H "" #H "" #H / 0 #H #H #H #H #H #H / 1 #""H #H $ / 0
#H #H #H #H #H #H ""H / 0 #H #H #H #H #H #H / 1 #""H #H
ewly !ormed '&st'rted ldehydes re s'sce%ti$le to !'rther oidtio& rectio&s which i& t'r& %rod'ce other cr$o&yl com%o'&ds. .3.6.3. &?ymtic $re#dow& o! !tty cids. ermi&ted $rley co&ti&s two li%oy+e&se e&?ymes &mely ;JK1 &d ;JK-2 (ter 1982). ;JK-1 is %rese&t i& rw $rley &d i&creses d'ri&+ +ermi&tio& wheres ;JK-2 o&ly develo%s d'ri&+ +ermi&tio& (N&+ A ch- wr? 1995). hey c& oidi?e !tty cids with ciscis- 1 %e&tdie&e system s'ch s li&oleic cid &d li&ole&ic cid to their hydro%eroy cids. ;i&oleic cid is stereo- &d re+io-s%eci!iclly oidi?ed to 9-;JJ $y ;JK-1 &d to 13-;JJ $y ;JK-2 (oderer
/ 1 #""H RH R ""H / 0 #H #H #H #H #H #H / 1 #""H
het-st$le th& ;JK-1. his e&?ymtic !ctor seems re- lted to %eroy+e&se (GJK) mem$er o! the %l&t cytochrome G50-co&ti&i&+ systems tht 'se hydro%eroide !tty cid s s'$strte &d ctly?e the hydroyltio&s witho't G or molec'lr oy+e&. B& t'r& the &ew hydroy cids c& $e $ro#e& dow& &o&-e&?ymticlly to vrio's cr$o&yl com%o'&ds (ressl et l. 1979) $'t co&sider$le levels remi& %rese&t i& the !i&ished $eer (
9-hydro%eroide lyse-li#e der *ee& *l# A o'm 19914 r$e ' $#e A ressl 20034 '+'es et l. 199). oth e&?ymes re very het-se&sitive with ;JK-1 $ei&+ somewht more het- resist&t th& ;JK-2. here!ore d'ri&+ #il&i&+ most ;JK ctivity is destroyed &d the remi&i&+ ctivity i& mlt is mi&ly d'e to ;JK-1 (N&+ A chwr? 1995). he remi&i&+ ctivity seems to $e the mi& c'se o! !tty cid oidtio& d'ri&+ mshi&+. his is i& ccor- d&ce with & o$served co&ce&trtio& rtio o! 9-;JJ/ 13-;JJ o! 10/1 i& wort d'ri&+ mshi&+ t 52 IC (Hl#er '+hes A im%so& 1996). ;JK e&?ymes $e- come com%letely i&ctivted t tem%ert'res $ove 65 IC. oth e&?ymes ehi$it % o%tim'm t 6.5. ;JK-1 hs $rod % r&+e with the ctivity !lli&+ to 50V t % 5. he %-r&+e o! ;JK-2 is m'ch &r- rower &d this e&?yme is lmost com%letely i&ctive t % 5 (oderer et l. 1991). red'ced !ormtio& o! hydro%eroy !tty cids ws o$served t hi+her i&itil mshi&+ tem%ert'res (
en6ymatic factor acti7ity mono8 di8 trihydro5y acids 9/--nonena) mono8 di8 trihydro5y acids non-en6ymatica))y non-en6ymatica))y carbony) compounds carbony) compounds
Fi+. 9. Jverview o! the c'rre&tly #&ow& e&?ymtic oidtio& %thwys o! li&oleic cid ledi&+ to cr$o&yl com%o'&ds. B% &anderhaegen et al% ' (ood )he*istr+ # 2./ 3#053$! 3.
cr$o&yl com%o'&ds i& wort. he c'rre&tly descri$ed e&?ymtic %thwys !or oidtio& o! li%ids d'ri&+ $eer %rod'ctio& re s'mmri?ed i& Fi+. 9. %3%0% (or*ation o4 /-b-da*as6enone
()-$-dmsce&o&e $elo&+s to clss o! crote&oid- derived cr$o&yl com%o'&ds. Gote&til %rec'rsors o! dmsce&o&e i& $eer re lle&e triols &d cetyle&e diols !ormed $y de+rdtio& o! &eo&thi& which is %rese&t i& the $sic i&+redie&ts o! $eer (Chev&ce et l. 2002). @oreover it ws %rove& tht the %%er&ce o! ()-$dmsce&o&e i& $eer i&cresed d'ri&+ +i&+ whe& $- +l'cosidse ws dded. he &o&-e&?ymtic relese i& $eer ws e&h&ced t low % (is et l. 2002). s the %ro- %osed %rec'rsors re li&#ed to s'+rs s o$served i& wi&es ('re' 'mes A "?'&+les 2000) ()-$-dm- sce&o&e mi+ht lso res'lt !rom chemicl hydrolysis o! +lycosides d'ri&+ $eer +i&+. Co&se>'e&tly +lycosides my lso $e co&sidered s im%ort&t so'rces o! !lvo'rs relted to $eer +i&+ (ie&dl
he cyclic cetls (25-trimethyl-13-diool&e 2-iso%ro%yl-5-dimethyl-13-diool&e 2-iso$'tyl-5dimethyl-13-diool&e &d 2-sec $'tyl-5-dimethyl- 13-diool&e) ori+i&te !rom co&de&stio& rectio& (Fi+. 10) $etwee& 23-$'t&ediol ('% to 280 m+/l i& $eer) &d & ldehyde (cetldehyde iso$'t&l 3-methyl- $'t&l &d 2-methyl-$'t&l res%ectively) (Ge%%rd 30 B% &anderhaegen et al% ' (ood )he*istr+ # 2./ 3# 053$!
A lsey 1982). B& $eer & e>'ili$ri'm $etwee& 25-trimethyl-13-diool&e cetldehyde &d 23- $'t&ediol is reched >'ite r%idly. s res'lt the i&- crese i& the cetldehyde co&ce&trtio& d'ri&+ +i&+ c'ses the 25trimethyl-13-diool&e co&ce&trtio& to i&crese very similrly (*&derhe+e& et l. 2003$). %#% Maillard rea6tion
@&y heterocyclic com%o'&ds !o'&d i& +ed $eers re well #&ow& %rod'cts o! the @illrd rectio&. he diverse &d com%le rectio&s $etwee& red'ci&+ s'+rs &d %rotei&s %e%tides mi&o cids or mi&es s well s the &'mero's co&sec'tive rectio&s re ll clssi!ied s @illrd rectio&s. B& co&trst to li%id oidtio& st'dies o! @illrd rectio&s relted to $eer +i&+ re scrce. 'ch limited i&terest my stem !rom o$serv- tio&s tht the c'rre&tly #&ow& @illrd %rod'cts i& +ed $eer (e+ !'r!'rl &d 5-hydroymethyl !'r!'rl) remi& $elow their !lvo'r threshold. J& the other h&d the ty%icl !lvo'r o! m&y !ood %rod'cts is d'e to @illrd rectio&s. t'dies with model systems co&- ti&i&+ si&+le ty%e o! s'+r &d mi&o cid reveled the !ormtio& o! myrid o! @illrd com%o'&ds (o!- m&& A chie$erle 19974 m&o +i #hr hyoi A hi$moto 1995) s'++esti&+ tht i& !ood i&cl'di&+ $eer & eve& +reter vriety o! %rod'cts c& $e !ormed. Gro$$ly the list o! @illrd %rod'cts i& the %revio's sectio& is o&ly smll re!lectio& o! the c- t'l &'m$er o! $eer +i&+-relted com%o'&ds. ome o! them mi+ht merit more i&terest s it ws !o'&d rece&tly tht the @illrd rectio& is res%o&si$le !or the develo%- me&t o! $redy sweet &d wi&e-li#e !lvo'r &otes d'r#H $ #H "H ethanol
" #H $ #H $
! H ! #H $ "# H "H # ! H H " ! # H acetaldehyde
H " "H "H "H #H $ #H $ #H $ #H $ H ! 2#'-butanediol
"H #H $ "" #H $ #H $ 2##-trimethyl-!#'-dioolane
Fi+. 10. Formtio& mech&ism o! 25-trimethyl-13-diool&e i& $eer (*&derhe+e& 200).
'ri&+ i&+ $eer stli&+. his ws demo&strted thro'+h the 'se stor+e some @illrd i&termedites my re- o! the s%eci!ic @illrd rectio& i&hi$itor mi&o+'&ict with ty%icl $eer co&stit'e&ts to +ive stli&+ com- di&e (rvo et l. 2001$). %o'&ds. F'r!'ryl ethyl ether rises i& $eer d'e to & O'&tittively o&e o! the most im%ort&t heterocycid-ctlysed co&de&stio& rectio& (Fi+. 12) o! !'r!'- clic stli&+ com%o'&d is 5-hydroymethyl-!'r!'rl. Bts ryl lcohol &d eth&ol (*&derhe+e& et l. 200). !ormtio& $y the @illrd rectio& is show& i& Fi+. B& the %rod'ctio& o! $eer !'r!'ryl lcohol is !ormed 11. he rectio& strts with chi!!Ls $se !ormtio& $e $y @illrd rectio& mi&ly d'ri&+ mlt #il&i&+ &d twee& cr$o&yl +ro'% o! heose s'+r &d & mi&o wort $oili&+. vide&ce ws !o'&d tht @illrd rec- +ro'% ledi&+ to & imi&e. his '&der+oes & mdori tio& o! mltose &d -(1)-oli+o+l'c&s is res%o&si$le. rerr&+eme&t to more st$le 1-mi&o-1-deoy#etose "ed'ctio& o! !'r!'rl $y yest my !'rther i&crese (lso clled mdori %rod'ct). owever t the % o! the !'r!'ryl lcohol co&ce&trtio& d'ri&+ !erme&ttio& $eer the mdori %rod'ct is s'$ect to e&oli?tio& (*&derhe+e& et l. 200$). &d s'$se>'e&t relese o! & mi&e which leds to 3- deoy-2-heos'lose (3-). his rective -dicr$o&yl .6. y&thesis &d hydrolysis o! voltile esters com%o'&d c& (mo&+ vrio's seco&dry %rod'cts) +ive rise to @F. trti&+ !rom %e&tose !'r!'rl is Chemicl co&de&stio& rectio&s $etwee& eth&ol !ormed. t this st+e @F !'r!'rl &d other com&d $eer or+&ic cids occ'r t si+&i!ic&t rtes d'ri&+ %o'&ds re merely i&termedites o! the @illrd rec $eer stor+e. For em%le 3-methyl-$'tyric cid &d tio&. hey re s'$ect to !'rther rectio&s 2-methyl-$'tyric led to ethyl 3-methyl-$'tyrte &d (co&de&stio& dehydrtio& cyclistio& isomeristio&) ethyl 2-methyl-$'tyrte (Hillims A H+&er 1979). %rod'ci&+ $row& %i+me&ts o! hi+h molec'lr wei+ht he %rec'rsor cids re %rod'ced $y oidtio& o! ho% the mel&oidi&s. - &d $-cids i& $eer s me&tio&ed %revio'sly. B& co&- ccordi&+ to "&+el-ldo et l. (2001) 3- is
trst some esters s'ch s iso-myl cette c& $e %rese&t i& co&sider$le >'&tities i& !resh $eer (230 hydrolysed &d their co&tri$'tio& to the !lvo'r de- l@) &d de+rdes d'ri&+ stor+e t 28 IC. F'rthercreses. Chemicl hydrolysis &d esteri!ictio& re more the co&ce&trtio& o! de+rdtio& i&termedite cid-ctlysed %rocesses $'t the ctivity o! e&?ymes (3-) lso decreses stro&+ly (rvo &che? with esterse ctivity sometimes detected i& $eer c& cherer A "&+el-ldo 2001). B& co&trst other lso !!ect the ester %ro!ile. eve& (1997) showed tht deoyoso&es 1-deoy-23-heodi'lose (1-) 1-didesome esterses re relesed $y yest i&to $eer s res'lt oyheos'lose (1-) &d 1-dideoy-23-%e&todi'- lose (1-G) i&crese (rvo et l. 2001$). 1- is !ormed $y de+rdtio& o! the mdori %rod'ct o! he- oses wheres 1- &d 1-G re %ro$$ly !ormed $y trec#er de+rdtio& o! 1- &d 1-deoy-%e&todi'- lose (1-G). # #H"H #H"H #H " "H " "H "H #H #H #H "H maltose
#H ai))ard Reaction H"" "H #H # "H #H #H"H
"H #H"H / "H #H "H H "H *R *HR *HR # #H pentose
#H"H # " "H #H"H #H"H #H #H #H ! R*H #/ $ "H / $ / $ #H"H
/ $ "H "H "H #H "H ai))ard Reaction heose *madori product !#2-enaminol
H "H" #H"H furfuryl
# # alcohol
" #H "H " # H ! "H # "H # " # " % furfural
- R*H #H"H / $ - "H #H
#H #H"H "H #H"H #H #H #H"H #H #H A#I; cata)ysed S * ! #H $ #H "H "H ethanol
"H "H substitution '-deoy-2-heosulose '#-dideoyheosulose-'-ene ('-+&) ('-++&)
"H H #H" H"H " "H H"H
# #H" " #H " #H #H $ # "H " H ! -hydroymethyl furfural furfuryl ethyl ether (-&,F)
Fi+. 12. Formtio& mech&ism o! !'r!'ryl ethyl ether d'ri&+ $eer Fi+. 11. Formtio& o! 5-hydroymethyl !'r!'rl $y @illrd rectio&. stor+e &d its %rec'rsor !'r!'ryl lcohol d'ri&+ $eer %rod'ctio&. B% &anderhaegen et al% ' (ood )he*istr+ # 2./ 3#053$! 30!
o! cell 'tolysis d'ri&+ !erme&ttio& &d mt'rtio&. 'ch esterse ctivity is stri& de%e&de&t &d to%-!er- me&ti&+ yests re more ctive th& $ottom !erme&ti&+ yests. he o%timl ctivity i& $eer is $etwee& 15 &d 20 IC. F'rthermore the e&?yme is lr+ely i&ctivted $y $eer %ste'ristio&. orsted ey olm$er+ &d
*rio's %rec'rsor molec'les i& $eer my tri++er the !ormtio& o! dimethyltris'l!ide (@). ccordi&+ to Ge%%rd (1978) the rectio& $etwee& meth&es'l!e&ic cid &d hydro+e& s'l!ide leds to @ d'ri&+ $eer stor+e. @eth&es'l!e&ic cid is !ormed $y $-elimi&tio& !rom -methylcystei&e s'l!oide i&trod'ced to $eer !rom ho%s. Jther @ %rec'rsors my $e 3-methylthio%ro- %io&lehyde &d its red'ced !orm 3-methylthio%ro%&ol (is A Colli& 20024 is et l. 2000). he %rod'ctio& o! @ is e&h&ced t low % (is et l. 2002). %$% :egradation o4 pol+phenols
Goly%he&ols i& $eer esily rect with "J &d !ree rdicls. he str'ct'rl ch&+es d'e to oidtio& hve &ot $ee& com%letely el'cidted. Bt is $elieved tht sim%le %oly%he&ols %olymeri?e to hi+h molec'lr wei+ht s%ecies (t&&i&s) either $y cid ctlysis or $y oidtive mech- &isms (rd&er A @c'i&&ess 1977). Gossi$ly %oly %he&ols re !irst oidi?ed to >'i&o&es or semi->'i&o&e rdicls which i&terct with other %he&olic com%o'&ds. F'rthermore %olymeristio& rectio&s lso c& $e i&- d'ced $y cetldehyde !ormed $y yest or $y eth&ol oidtio& thro'+h the !ormtio& o! ethyl $rid+es $e- twee& !lv&ols (elco'r o&dey&e ro'sdle A i&- +leto& 19824 'cier o'r+eois *itry "o' A lories 1997). %rt !rom %olymeristio& ri&+ o%e&i&+ i& oidised %he&ols ws %ro%osed s & lter&tive de+- rdtio& mech&ism (Cilliers A i&+leto& 1990). 'ri&+ $eer stor+e %he&olic %olymers i&terct with %rotei&s &d !orm i&sol'$le com%lees &d h?es. %% 89idative versus non-o9idative beer aging
From the %revio's co&sidertio&s it $ecomes cler tht oy+e& tri++ers the relese o! !ree rdicls which 302 B% &anderhaegen et al% ' (ood )he*istr+ # 2./ 3# 053$!
c& esily rect with m&y $eer co&stit'e&ts ledi&+ to r%id ch&+es i& the !lvo'r %ro!ile. mo&+ these %rocesses re the oidtio& o! lcohols ho% $itter com%o'&ds &d %oly%he&ols. i&ce oy+e& is very detrime&tl !or the !lvo'r o! $eer $rewers hve tried to mi&imi?e the oy+e& %ic#-'% i& !i&ished $eer. @od- er& !illi&+ e>'i%me&t c& chieve totl oy+e& levels i& the $ottle o! less th& 0.1 m+/l. t s'ch low oy+e& levels it is de$t$le whether the !ormtio& o! rec- tive oy+e& s%ecies ("J) is the determi&i&+ !ctor i& the +i&+ o! these $eers. B&deed other molec'les %rese&t i& $eer hve e&o'+h rectivity to i&terct &d !orm stli&+ com%o'&ds. eer stli&+ is o!te& re+rded s o&ly the res'lt o! oidtio& $'t &o&- oidtive %rocesses my $e 'st s im%ort&t es%e- cilly t the low oy+e& levels reched i& moder& $reweries. o&-oidtive rectio&s c'si&+ !lvo'r deteriortio& re esteri!ictio&s etheri!ictio&s @illrd rectio&s +lycoside &d ester hydrolysis. ve& ()-2-&o&e&l com%o'&d lo&+ s's%ected to $e the mi& c'se o! oi- di?ed !lvo'r %rdoiclly %%ers to rise $y &o&- oidtive mech&isms i& $eer. his e%li&s why $eer stli&+ is %ossi$le i& the $se&ce o! oy+e&. J& the other h&d ltho'+h some com%o'&ds res'lt !rom oidtio& rectio&s it is t %rese&t &ot relly cler which com- %o'&d(s) is/re res%o&si$le !or the oidtio& o!!-!lvo'r o! $eer. B& co&cl'sio& some rectio&s hve received co&sider- $ly more tte&tio& th& others %rtly d'e to historicl !ctors. owever it remi&s im%ort&t to evl'te the relev&ce o! s%eci!ic re%orted rectio&s i& the overll $eer +i&+ %rocess. 'ch ssessme&t hs scrcely $ee& do&e &d it is c'rre&tly &ot cler how im%ort&t s%e- ci!ic +i&+ rectio& is !or the ch&+es i& !lvo'r %erce%- tio& o! %rtic'lr $eer.
oðeless $etter #&owled+e o! rectio& mech- &isms i&volved i& stli&+ %he&ome& llows closer st'dy o! the e!!ects o& %rtic'lr rectio&s o! wort &d $eer %rod'ctio& %rmeters. . !nhibitin" and promotin" e##e$ts on beer a"in" rea$tions
#%!% <+pes o4 rea6tions
Chemicl &d $iochemicl %rocesses which occ'r d'ri&+ $eer stor+e %roceed sim'lt&eo'sly ltho'+h t di!!ere&t rtes. o wht ete&t certi& rectio&s t#e %lce de%e&ds o& stor+e co&ditio&s &d $y com%etitio& &d i&terctio& o! %thwys. his lso %%lies to rec- tio&s d'ri&+ the $rewi&+ %rocess which determi&e the %rec'rsor co&ce&trtio&s !or stli&+ rectio&s i& the !i&l $eer. everl methods hve $ee& s'++ested to co&trol to some de+ree the rectio&s res%o&si$le !or !lvo'r dete- riortio& d'ri&+ $eer stor+e.
#%2% 89idative beer aging rea6tions #%2%!% 1eneral
s%ecilly i& $ottled $eer ecessive mo'&ts o! oy- +e& my c'se r%id ch&+e i& rom &d tste. B& re- ce&t yers it $ecme evide&t tht levels o! oy+e& thro'+ho't the $rewi&+ %rocess c& lso !!ect the $eer shel!-li!e dow&strem. @i&imi?i&+ the !ormtio& &d ctivity &d wort o! m'st "J $e (JP 2 !irst JJ- 2
&d J-) i& $eer ste% !or im%rovi&+ $eer !lvo'r st$ility. @olec'lr oy+e& itsel! is &ot very rective $'t its i&i- til co&ce&trtio& determi&es the level o! "J. B& the ctivtio& o! oy+e& tr&sitio& metl io&s (C'D &d Fe2D) ct s electro& do&ors. Co&se>'e&tly %rocess &d tech&olo+icl %rmeters sho'ld $e d%ted to mi&- imi?e wort &d $eer oy+e& %ic#-'% &d the co%%er &d iro& io& co&ce&trtio&s. he ctivtio& o! oy+e& c& $e stim'lted $y %ro- oid&t molec'les which re +e&erlly $le to red'ce metl io&s. B& this %rocess the %ro-oid&t itsel! my $e- come rdicl which rects with other co&stit'e&ts or de+rdes &d my %rod'ce o!!-!lvo'rs. ct'lly oid- tive rectio&s i& wort &d $eer m'st $e re+rded s chi& o! redo +e&ts i&volved i& electro& tr&s!er rec- tio&s. J& the other h&d the e!!ects o! oy+e& c& $e i&hi$ited $y certi& $eer or wort com%o&e&ts (&ti-oi- d&ts). e&erlly the &ti-oid&t ctivity is $sed o& the c%t're o! "J &d !ree rdicls. he c%t're o! me- tl io&s with some chelti&+ +e&ts is &other &ti-oi- dtive %%roch. B& the %st !ew yers the &ti- or %ro-oidtive ctiv- ity o! wort &d $eer hs $ee& i&vesti+ted $y vrio's methods i&cl'di&+ the determi&tio& o!= () the c%city to red'ce the iro&-(BB)-di%yridyl com %le (Ch%o& ;o'is A Ch%o& 1981)4 ($)the $ility to scve&+e the rdicl ctio& o! 220-?i&o$is-(3ethyl$e&?othi?oli&e-6-s'l!o&te) () i& & >'eo's %hse (r#i et l. 1999)4 (c)the 11-di%he&yl-2 %icrylhydr?yl (GG) !ree rdicl-scve&+i&+ ctivity (<&ed
(+)the redo %ote&til ('c#ee @om ye A mo&d 19974 lic Glic A Ci#ovic 1994 v& trie& 1987)4 (h) the c%city to dely methyl li&olete oidtio& i& li%idic medi &d t hi+h tem%ert're !ollowed $y +s chromto+r%hy (oivi& et l. 19934 @illrd A erset 1995)4 (i) li&oleic cid hydro%eroide i& Fe&to&-ty%e rectio& (ri+ht tewrt A Gti&o 1999)4 () the i&hi$itio& time o! 220-?o$is(2-midi&o%ro- %&e) dihydrochloride-i&d'ced oidtio& o! & >'eo's dis%ersio& o! li&oleic cid (;ie+eois ;er- m'sie' A Colli& 2000). he mor e&do+e&o's &ti- or %ro-oid&ts i& wort &d $eer re disc'ssed $elow. #%2%2% Sul4ite
Co&versio& o! s'l!te $y yest (!rom wter &d rw mterils) is the mor e&do+e&o's so'rce o! s'l!ite i& $eer. st'dy (&derse& J'ttr'% A #i$sted 2000) 'si&+ the " l+ %hse method (e) hi+hli+hted s'l!ite s o&e o! the most e!!ective &tioid&ts i& $eer. Bts %res- e&ce %ost%o&es the !ormtio& o! !ree rdicls (mi&ly the 1hydroyethyl rdicl) mes'red $y " s%i& tr%- %i&+. he e!!ective&ess o! s'l!ite seems to $e d'e to its two electro& &o&-rdicl-%rod'ci&+ rectio& with %eroides. #%2%3% Pol+phenols
Goly%he&olic com%o'&ds re im%ort&t &tioi- d&ts i& m&y systems. e&erlly i& $eer 70S80V o! the %oly%he&ol !rctio& ori+i&tes !rom $rley mlt &d &other 20S30V !rom ho%. ;ower molec'lr wei+ht %oly%he&ols i& %rtic'lr re ecelle&t &ti- oid&ts. Hith i&cresi&+ molec'lr wei+ht the red'c- i&+ %ower decreses ('++ey 2001). Goly%he&ols c& rect with !ree rdicls to %rod'ce %he&oy rdicls (Fi+. 13) which re reltively st$le d'e to delocli?- tio& o! the !ree rdicl over the romtic ri&+. ome %oly%he&ols re lso &tioid&ts $y their $ility to chelte tr&sitio& metl io&s. J& the other h&d cer- ti& %oly%he&ols $ehve s %rooid&ts d'e to their $ility to tr&s!er electro&s to tr&sitio& metl io&s (m!orth 1999$). here is some co&troversy co&cer&i&+ the relev&ce o! %oly%he&ols s &ti-oid&ts i& $eer &d wort. " l+ %hse st'dies (&derse& et l. 20004 &derse& A " #" " " # #
Fi+. 13. t$ili?tio& o! %he&oy rdicl $y delocli?tio&.
#i$sted 2001) showed &o si+&i!ic&t e!!ect o! %oly%he- &ols o& the !ormtio& o! !ree rdicls i& $eer d'ri&+ stor+e or i& wort d'ri&+ $rewi&+. his ws ttri$'ted to the etreme rectivity o! hydroyl rdicls &d their &o&-selective elimi&tio& thro'+h rectio& with other %romi&e&t com%o'&ds o! $eer (eth&ol) or wort (s'+- rs). his voids rdicl-scve&+i&+ with %oly%he&ols %rese&t i& reltively smll co&ce&trtio&s. owever it is &ot cler whether this %%lies lso to other rdicls s'ch s e+ !tty cid oidtio& rdicls i& wort. B& $eer %oly%he&ols co&tri$'te '% to 60V o! the e&do+e&o's red'ci&+ %ower mes'red i& the iro&-(BB)- di%yridyl test () &d the GG test (c) (<&ed et l. 19954 @c@'rro'+h et l. 1996). Grtil removl o! the %oly%he&ol !rctio& $y %olyvi&yl%oly%yrrolido&e (G*GG) tretme&t dimi&ishes the red'ci&+ %ower $y 9S 38V $'t does &ot m#e the $eer more s'sce%ti$le to oidtive dm+e (@c@'rro'+h et l. 1996). his ws co&!irmed i& se&sory e%erime&ts $y @i#ys# r$# s#ov &d ro+l (2002). he G*GG-treted $eers develo%ed less stri&+e&t chrcter. @oreover ccord- i&+ to Hlters et l. (1997$) &d Hlters esm& &d '+hes (1997) (D)-ctechi& &d !er'lic cid red'ce the !ormtio& o! %rtic'lr cr$o&yl com%o'&ds i& $eer t hi+h oy+e& levels $'t &ot t low oy+e& levels. F'r- thermore !er'lic cid levels determi&e whether it is %ro-oid&t (low co&ce&trtio&) or &tioid&t (hi+h- co&ce&trtio&). he mi& e!!ect o! %oly%he&ols o& !lvo'r st$ility is %ro$$ly sit'ted i& the mshi&+ &d wort $oili&+ ste%s (;ie+eois et l. 20004 @i#ys# et l. 2002). B& %rtic'- lr %oly%he&ols etrcted !rom ho% d'ri&+ wort $oili&+ si+&i!ic&tly co&tri$'te to the red'ci&+ %ower &d e!!ectively dimi&ish the &o&e&l %ote&til o! wort (;er- m'sie' ;ie+eois A Colli& 2001). e&sory e%erime&ts (@i#ys# et l. 2002) lso co&!irm the %ositive e!!ects o! ho% %oly%he&ols d'ri&+ $rewi&+ o& !lvo'r st$ility. #%2%% Melanoidins and redu6tones
@lt #il&i&+ ('% to 80 IC) mlt rosti&+ (110S250 IC) &d wort $oili&+ +e&erte &tioid&ts thro'+h @illrd rectio&s (oivi& et l. 1993). hese &tioi- d&ts i&cl'de red'cto&es &d mel&oidi&s. he red'ci&+ %ower o! red'cto&es is d'e to the e&diol +ro'% (Fi+. 1) which c& +e&erte cr$o&yls. scor$ic cid (vitmi& C) 30 B% &anderhaegen et al% ' (ood )he*istr+ # 2./ 3# 053$!
## " # "H # # "H # "5< endiol group
Fi+. 1. Jidtio& o! red'cto&e. " " "
is ty%icl red'cto&e $'t it is &ot %rod'ced $y @illrd rectio&s. owever i& the %rod'ctio& o! $eer scor$ic cid is o!te& 'sed s & eo+e&o's &ti-oid&t. "e- ce&tly " st'dies >'estio&ed the relev&ce o! scor$ic cid !or !lvo'r st$ility. J& dditio& to $eer rther %ro-oidtive ctivity ws !o'&d d'e to the !ormtio& o! more !ree rdicls (&derse& et l. 2000). limited &'m$er o! st'dies (Hiewic#reme
the str'ct'rl !et'res res%o&si$le !or &ti- oidtive ctivity re di!!ic'lt to drw. @oreover mel- &oidi&s or its %rec'rsors my lso %rese&t %ro-oidtive %ro%erties s shimoto (1972) showed their i&volve- me&t i& the oidtio& o! lcohols to ldehydes d'ri&+ $eer stor+e. he levels o! &tioid&ts res'lti&+ !rom @illrd rectio&s &d s'+r crmeli?tio& re low i& li+ht mlts $'t si+&i!ic&t i& dr# s%ecility mlts (ri+ht et l. 19994 Co+he *&derhe+e& Gel+rims stey&s A elv' 20034 ri!!iths A @'le 1997). he hi+her red'ci&+ %ower o! wort &d $eer %rod'ced !rom dr#er colo'red mlts my the& co&tri$'te to $etter !lvo'r st$ility o!te& re%orted !or s'ch $eers. #%2%#% )helating agents
%rt !rom %oly%he&ols vrio's other com%o'&ds i& wort &d $eer i&cl'di&+ mi&o cids %hytic cid &d mel&oidi&s (Hiewic#reme A
'estrtio& +e&ts !or metl io&s. B& wort &d $eer & e>'ili$ri'm eists $etwee& !ree &d che- lted metl io&s. e%e&di&+ o& cheltor ty%e $o'&d metl io&s hve either less or more c%$ility to %romote oy+e& rdicl !ormtio& (m!orth 1999$). #%3% n;+*ati6 o9idation o4 4att+ a6ids
@&y strte+ies hve $ee& %ro%osed !or red'ci&+ the e&?ymtic oidtio& o! !tty cids. ;i%oy+e&se ctiv- ity d'ri&+ mshi&+ c& $e co&trolled $y severl tech&o- lo+icl %rmeters. ;JK e&?yme ctivity d'ri&+ mshi&+ is i&!l'e&ced $y the tem%ert're re+ime &d the wort %. @shi&+-i& t hi+h tem%ert'res (X65 IC) e!!ectively i&hi$its ;JK e&?ymes (
$le 2 trte+ies !or deli&+ with $eer stli&+ ccordi&+ to m!orth (2000$) Grocess st+e rley @lti&+ rist @illi&+ @shi&+ A Hort collectio& oili&+ A Ferme&ttio& A ow&strem clri!ictio& co&ditio&i&+ %rocessi&+ Gc#+i&+ A distri$'tio& i+h relev&ce S low cost/ris# @i&im'm oy+e& '%t#e i& %c#+e se o! s'l!'r dioide @i&im'm %ic#-'% o! iro& &d co%%er i+h relev&ce S hi+h cost/ris# void&ce o! trte+ies to Jy+e& ecessively e&h&ce s'l!'r mi&imi?tio& %rolo&+ed dioide withi& heti&+ le+l limits "e!ri+erted stoc#holdi&+ &d tr&s%orttio& toc# rottio& &d lo+istics Jy+e&-scve&+er crow& cor#s ;ow relev&ce S low cost/ris# '%%ressio& o! B&cresed 'se o! '%%ressi&+ ri+ht worts se o! em$ryo develo%me&t s'+r d'&cts oy+e& i&+ress scor$ic cid S e+ rootlet i&hi$itors @imi?ed #il&i&+ tem%ert'res se o! red'ced iso--cids "ed'ced mshi&+ % ;ow relev&ce S hi+h cost/ris# se o! colo'red i+h mshi&+- mlts i& tem%ert'res
electio& o! %r+i&+ o! +rist @illi&+ re+imes $rleys with with i&ert +s which mi&imi?e low ;JK em$ryo dm+e %ote&til &ero$ic milli&+
%ro%osed (v& Hes$er+he 1997). ;ter m!orth (1999) s'++ested tht the vil$ility o! oy+e& i& the msh is more li#ely to limit li%oy+e&se ctivity th& the vil$ility o! e&?ymes. his ws co&!irmed $y
o&-oidtive rectio&s i& stored $eer re o! very di!- !ere&t &t'res. Co&se>'e&tly the e!!ects o! %rod'ctio& &d stor+e %rmeters re hi+hly vri$le. everthe- less severl &o&-oidtive +i&+ %rocesses s'ch s the relese o! ldehydes !rom imi&es esteri!ictio& etheri!i- ctio& ester hydrolysis dimethyltris'l!ide !ormtio& &d +lycoside hydrolysis re ll %romoted t low $eer %. low % my lso e&h&ce oidtive rectio&s $y %roto&tio& o! rective %erhydroyl s'%eroide rdicls RJP (JJ-). 2 Q rdicls to the more ll this s'%%orts the se&sory !i&di&+s tht $eer +es !ster t low % (<&ed #shio om#i A Jsw 1997). himi?' et l. (2001$) correlted the decrese i& % d'ri&+ !er- me&ttio& with the cell'lr si?e o! the %itchi&+ yest. hi+her % ws o$ti&ed with yest lr+e-cell si?es &d the res'lti&+ $eers showed $etter !lvo'r st$ility (himi?' r#i <'rod #shio A hi&ots'# 2001). Nest lso hs & im%ort&t role i& decresi&+ the mo'&t o! stli&+ com%o'&ds &d its %rec'rsors. Nest met$olism d'ri&+ the !erme&ttio& is mi&ly !er- me&ttive. his res'lts i& & ecess o! red'ced coe&- ?ymes &d G. o re+e&erte these coe&?ymes they re 'sed $y severl ldo#etored'ctses (e$o'r+ ;'re&t '%ire A @sschelei& 19934 e- $o'r+ *erli&de& *& e Hi&#el @sschelei& A *& edervelde 19954 *& Bersel %%i&# *& er#el "om$o'ts A $ee 19974 *& edervelde J'dm esmedt A e$o'r+ 19994 *& edervelde *erli&de& Ghili%% A e$o'r+ 1997). his so-clled UUyest red'c- i&+ %owerUU res'lts i& the red'ctio& o! wort ldehydes to lcohols d'ri&+ !erme&ttio&. "ece&tly & i&teresti&+ yest G-de%e&de&t red'ctse ws descri$ed (&- che? et l. 2001) c%$le o! red'ci&+ -dicr$o&yl i&termedites o! the @illrd rectio& s'ch s 3-deoy- 2-heos'lose (3-). owever !'rther i&vesti+tio&s m'st demo&strte whether '&der $eer !erme&ttio& co&ditio&s yest c& red'ce s'ch @illrd rectio& dicr$o&yls. @illrd %rod'cts s'ch s !'r!'rl i&cresed more d'ri&+ $eer +i&+ whe& mlt ws #il&ed t hi+her tem %ert'res &d the therml lod o& wort ws hi+her d'r- i&+ %rod'ctio& (r?iss c# @ied&er A ;'sti+ 1999). he stli&+ com%o'&d !'r!'ryl ethyl ether showed the sme $ehvio'r (*&derhe+e& et l. 200$). 30. B% &anderhaegen et al% ' (ood )he*istr+ # 2./ 3# 053$!
J& the other h&d @illrd rectio&s re i&hi$ited $y s'l!ite (Hed?ich A
J%timistio& o! the $rewi&+ %rocess with res%ect to !lvo'r st$ility re>'ires cler i&si+ht o! the ty%es o! !lvo'r ch&+es d'ri&+ stor+e &d the &t're o! the molec'les i&volved. his my however vry $etwee& $eer ty%es (e+ %ils&er $eers &d s%ecility $eers). ec- o&dly it is &ecessry to clri!y the rectio& %thwys i& $eer ledi&+ to the stli&+ com%o'&ds. Fi&lly the i&!l'e&ce o! the %rod'ctio& %rocess o& the stli&+ rec- tio&s m'st $e mde cler. <&owled+e o! the +i&+ %he&ome&o& i& %rtic'- lr ty%e o! $eer c& $e 'sed to develo% %%ro%rite tech&olo+icl %rocess im%roveme&ts to co&trol its %r- tic'lr !lvo'r st$ility. esides their relev&ce !or !l- vo'r st$ility the i&vestme&t costs !or s'++ested %rocess modi!ictio&s m'st $e evl'ted &d $l&ce sho'ld $e mde $etwee& $etter &d lo&+er !lvo'r st- $ility &d costs. $le 2 %rese&ted $y m!orth (2000 2000$) is hel%!'l i& s'mmri?i&+ s'ch co&sid- ertio&s. ltho'+h the strte+ies seem stri+ht!orwrd %rcticl e%erie&ce my soo& show tht !lvo'r st- $ility is still hrd to co&trol. here mi+ht $e o&e e%l&tio& !or this= the #&owled+e o! stli&+ com%o- &e&ts is still i&com%lete &ot o&ly co&cer&i&+ the &'m- $er &d ty%es o! com%o'&ds i&volved $'t lso the rectio& mech&isms.
Re#eren$es
hre&st-;rse& . A ;evi& &se& . (1963). schromto+r%h- ische &ters'ch'&+e& ' $er die eschm#sst$ilit t vo& ier. r'wisse&sch!t 16 393S397. &derse& @; J'ttr'% . A #i$sted ; (2000). Gote&til &tioid&ts i& $eer ssessed $y " s%i& tr%%i&+. o'r&l o! +ric'lt'rl &d Food Chemistry 8 3106S3111. &derse& @; A #i$sted ; (1998). lectro& s%i& reso&&ce s%i& tr%%i&+ ide&ti!ictio& o! rdicls !ormed d'ri&+ ero$ic !orced +i&+ o! $eer. o'r&l o! +ric'lt'rl &d Food Chemistry 6 1272S1275. &derse& @; A #i$sted ; (2001). @odi!ictio& o! the levels o! %oly%he&ols i& wort &d $eer $y dditio& o! hemethyle&etet- rmi&e or s'l!ite d'ri&+ mshi&+. o'r&l o! +ric'lt'rl &d Food Chemistry 9 5232S5237. &+eli&o F
reltio&shi% to $eer !lvor st$ility. o'r&l o! the meric& ociety o! rewi&+ Che mists 57 3S37. r#i . #shio @. A hi&ots'# <. (2002). &ew %rmeter !or determi&tio& o! the ete&t o! stli&+ i& $eer. o'r&l o! the meric& ociety o! rewi&+ Chemists 60 26S30. m!orth CH A Grso&s ". (1985). ew %roced'res to im%rove the !lvor st$ility o! $eer. o'r&l o! the meric& ociety o! rewi&+ Chemists 3 197S202. m!orth CH (1999). &?ymic &d &o&-e&?ymic oidtio& i& the $rewho'se= theoreticl co&sidertio&. o'r&l o! the B&stit'te o! rewi&+ 105 237S22. m!orth CH (1999$). he scie&ce &d '&derst&di&+ o! the !lvo'r st$ility o! $eer= criticl ssessme&t. r'welt B&ter&- tio&l 98S110. m!orth CH (2000). eer >'lity= oidtio&. rewersL 'rdi& 129 31S3. m!orth CH (2000$). @#i&+ se&se o! !lvor ch&+es i& $eer. @ ech&icl O'rterly 37 165S171. r#er "; rcey F Brwi& Gi%sts G. A ;eis# . (1983). ;i$ertio& o! stli&+ ldehydes d'ri&+ stor+e o! $eer. o'r&l o! the B&stit'te o! rewi&+ 89 11S15. r#er "; Gi%sts G. A rcey F (1989). mi&tio& o! $eer cr$o&yls s their oimes $y +s chromto+r%hySmss s%ectrometry. o'r&l o! the meric& ociety o! rewi&+ Chemists 7 9S1. srov . vel . &o'se# . A Ci?#ov . (1999). Ch&+es i& the co&te&t o! the mi&o-cids i& s%ite o! the &t'rl +i&+ o! $eer. @o&tsschri!t F'r r'wisse&sch!t 52 112S118. ter (1982). ;i%oidses i& @lti&+ &d @shi&+. o'r&l o! the B&stit'te o! rewi&+ 88 390S396. ter (198). "eco+&itio& o! 2 li%ses !rom $rley &d +ree& mlt. o'r&l o! the B&stit'te o! rewi&+ 90 277S281. elit? A rosch H. (1999). Food chemistry. erli& eidel$er+= %ri&+er *erl+. er&stei& ;. A ;'!er ;. (1977). F'rther st'dies o& !'r!'rl= the i&!l'e&ce o! rw mterils %rocessi&+ co&ditio&s &d %ste'ri?- tio& tem%ert'res. o'r&l o! the meric& ociety o! rewi&+ Chemists 35 21S35. ie&dl @.
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$itter&ess co&siste&cy i& reltio& to tetrhydroiso-l%h-cids. o'r&l o! the B&stit'te o! rewi&+ 106 169S178. e$o'r+ . ;'re&t @. '%ire . A @sschelei& C (1993). he s%eci!ic role &d i&terctio& o! yest e&?ymtic systems i& the removl o! !lvo'r-%ote&t wort cr$o&yls d'ri&+ !erme&ttio&. Groceedi&+s o! the 'ro%e& rewery Co&ve&tio& Co&+ress 37S. e$o'r+ . ;'re&t. @. *erli&de& *. *& e Hi&#el ;. @sschelei& C A *& edervelde ;. (1995). Nest %hysiolo+icl stte o& cr$o&yl red'ctio&. C-ym%osi'm immo$ili?ed yest %%lictio&s i& the $rewi&+ i&d'stry. @o&o+r%h KKB* (%%. 158S17). elco'r o&dey&e G. ro'sdle < A i&+leto& *; (1982). he rectio&s $etwee& %oly%he&ols &d ldehydes &d the i&!l'e&ce o! cetldehyde o& h?e !ormtio& i& $eer. o'r&l o! the B&stit'te o! rewi&+ 88 23S23. evre' . loc#m&s C. A v&de @eersche . (1981). Cr$o&yl com%o'&ds !ormtio& d'ri&+ +i&+ o ! $eer. C-Flvo'r sym%o- si'm. @o&o+r%h *BB (%%. 191S201). oderer .
'!o'r G ;e's @. ter A ym& " (1999). Chrcteri?tio& o! the rectio& o! $is'l!ite with '&st'rted ldehydes i& $eer model system 'si&+ &'cler m+&etic reso&&ce s%ectrosco%y. o'r&l o! the meric& ociety o! rewi&+ Che mists 57 138S1. ichhor& G. 'id chromto+r%hy &d hi+h %ress're li>'id chromto+r%hy. o'r&l o! the B&stit'te o! rewi&+ 86 35S1. ree&ho!! <. A Hheeler " (1981$). vl'tio& o! stle !lvo'r &d $eer cr$o&yl develo%me&t d'ri&+ &orml &d ccelerted +i&+ 'tili?i&+ li>'id &d hi+h %ress're li>'id chromto+r%hy. Groceedi&+s o! the 'ro%e& rewery Co&ve&tio& Co&+ress 05S12. ri!!iths A @'le G (1997). he e!!ects o! di!!ere&t cerel colo'red mlts o& red'ci&+ %ower d'ri&+ the $rewi&+ %rocess. Groceedi&+s o! the 'ro%e& rewery Co&ve&tio& Co&+ress 267S27. ri+s$y A Glm&d " (1976). he 'se o! 2thio$r$it'ric cid i& the mes'reme&t o! $eer oidtio&. o'r&l o! the meric& ociety o! rewi&+ Chemists 3 9S55. ro &>vist . iiril . *irt&e& . ome . A G'&e& . (1993). Cr$o&yl com%o'&ds d'ri&+ $eer %rod'ctio& &d i& $eer. Gro- ceedi&+s o! the 'ro%e& rewery Co&ve&tio& Co&+ress 21S28. rym <. yse F. A <to . (199). vl'tio& $y m'ltivrite-&lysis o! the stle !lvor !ormed while stori&+ $eer. ioscie&ce iotech&olo+y &d iochemistry 58 1595S1598. shimoto . (1966). "e%. "es. ;$ortori'm.
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