Food Chemistry

438 8 Food Additives

Table 8.5.Amino acid sequence of thaumatin I. (Disulfide bonds: 9–204, 55–66, 71–77, 121–193, 126–177, 134–
145, 149–158, 159–164; the sequence YFD shown inbold type, which is localized in aβ-turn, is regarded as
a part of the structure responsible for the cross reaction of thaumatin with antibodies against monellin as well as
for making contact with the sweetness receptor (cf. Table 8.4 and Fig. 8.7 and 8.8)

5 10 15202530 35 40

ATF EI VNRCS Y TVWA AAS KG DAALD AGGRQ LN S GE SWTI N

41VEP GTNGGKI WART D CYFDDS GS GI CKTGD CG GLL RC KRF

81GRP P TTLAEF S LNQ Y GKDYI DI S NI KGF NV P MNF S PT TRG

121CRGVRCAADI V GQC P AKLKA P GGGC NDACT VF QTS EY CCT

161TGKCGPTEYS RFFKR LCPDAFSYVL DKPTT VTCPGSS NYR

201 V T F C P T A

8.8.6 CurculinandMiraculin

Curculin is a sweet protein (fsac, g( 6. 8 )=550)
of known sequence (Table 8.6). It occurs in the
fruit ofCurculigo latifolia. The sweet taste in-
duced by this protein disappears after a few min-
utes, only to reappear with the same intensity
on rinsing with water. It is assumed that Ca^2 ⊕
and/or Mg^2 ⊕ions in the saliva suppress the sweet
taste. Rinsing with citric acid (0.02 mol/l) con-
siderably enhances the impression of sweetness
(fsac, g( 12 )=970). Thus, like miraculin, curculin
acts as a taste modifier.
Miraculin is a glycoprotein present in the fruit
ofSynsepalum dulcificum(a tropical fruit known
as miracle berry). Although it is tasteless, it has
the property of giving sour solutions a sweet taste
and therefore it is called a taste modifier. Thus,
lemon juice seems sweet when the mouth is first
rinsed with a solution of miraculin. The molecu-
lar weight of this taste modifier is 42–44 kdal.

8.8.7 Gymnema silvestreExtract................................

The extract fromGymnema silvestreis related to
the taste modifier miraculin. It has the property
of eliminating the ability to perceive sweetness
for a few hours, without interfering with the per-

Table 8.6.Amino acid sequence of curculin

5 10152025303540

D NVLLS GQTL HADHS LQAGA YT LTI QNNCN LVKYQ NGRQI

41WAS NTDRRGS GCRLT LLS DG NL VI Y DHNNN DVNGS ACCGD

81A GKYALVLQK DGRF V I YGP V LWS LG P NGCR RVNG

ception of other taste qualities. The active sub-

stance has not yet been identified.

8.8.8 Stevioside..............................................

Leaves ofStevia rebaudianacontain approx. 6%

stevioside (fsac, g( 4 )∼300). Its structure is shown

in Formula 8.7. This compound is of interest as

a sweetener, however its toxic properties are un-

clear.

(8.7)