Full text of DOI:10.1111/j.1365-2621.2001.tb08213.x

JFS: Food Chemistry and Toxicology
Effects of pH on Caramelization and Maillard
Reaction Kinetics in Fructose-Lysine Model Systems
E.H. AJANDOUZ, L.S. TCHIAKPE, F. DALLE ORE, A. BENAJIBA, AND A. PUIGSERVER
ABSTRACT: The nonenzymatic browning reactions of fructose and fructose-lysine aqueous model systems were
investigated at 100 ЊC between pH 4.0 and pH 12.0 by measuring the loss of reactants and monitoring the pattern of
UV-absorbance and brown color development. At all the pH values tested, the loss of fructose was lower in the
presence than in the absence of lysine. And, in lysine-containing fructose solution, the sugar disappeared more
rapidly than the amino acid. Lysine was moderately lost below pH 8.0. Caramelization of fructose, which accounted
for more than 40% of total UV-absorbance and 10 to 36% of brown color development, may therefore lead to
overestimating the Maillard reaction in foods.
Keywords: Maillard reaction, caramelization, lysine, fructose
Introduction
(Ellingson and others 1954; Bobbio and
The aim of this study was, there-
HE MAILLARD REACTION, WHICH others 1981; Baxter 1995). It has also fore, to describe the kinetics of the
T
links the carbonyl group of reduc- been reported that the browning of nonenzymatic browning reaction in
ing carbohydrates and the amino group fructose solutions was either more or fructose solutions heated either alone
of free amino acids as well as of lysyl less extensive than that of glucose, de- or in the presence of lysine at 100 ЊC at
residues in proteins, may have either pending on the heating conditions initial pH values ranging from 4.0 to
beneficial or detrimental effects. At ear- (Kato and others 1969; Buera and oth- 12.0. The extent of both the caramel-
ly stages of the reaction, an improve- ers 1987; Wijewickreme and others ization and the Maillard reactions was
ment of the functional properties of 1997). On the other hand, the influence compared at the initial, intermediate,
proteins was generally observed (Handa of pH on the Maillard reaction of amino and final stages. The kinetic behavior
and Kuroda 1999), and afterwards anti- acid-containing glucose or fructose of the nonenzymatic browning reac-
oxidant compounds are formed (Monti model systems has been studied at dif- tions of fructose was also compared to
and others 1999) as well as highly ap- ferent pH ranges and conditions of that of glucose under the same experi-
preciated browned flavors (Ho 1996). temperature and concentration of reac- mental conditions (Ajandouz and
However, loss of lysine and decrease in tants, namely pH 4-6 (Buera and others Puigserver 1999).
protein digestibility may also occur 1987), pH 5-7 (Petriella and others
Materials and Methods
(Friedman 1996), together with some 1985), pH 5.5-7.5 (Baxter 1995) and pH
antinutritive (Oste and others 1987; 6-12 (Ashoor and Zent 1984). It is worth
O’Brien and others 1994), toxic (O’Brien mentioning here that only the Maillard
and Morrissey 1989) or mutagenic browning intensity was measured in
(Wang and others 1999) effects. The most of these studies.
Materials
L-lysine, D-fructose, L-␣-amino-n-
butyric acid and triethylamine (TEA)
caramelization of sugars, which takes
Very little attention has been paid so were purchased from Sigma Chemical
place at the same time, also contributes far to the contribution of carameliza- Co. (St. Louis, Mo., U.S.A.). Phenyl-
to nonenzymatic browning reactions. tion to the nonenzymatic browning re- isothiocyanate (PITC) and the standard
In both the Maillard and caramelization actions of glucose or fructose, although mixture of amino acids were supplied
reactions, highly UV-absorbing and col- studying the chemical reactions in- by Pierce Chemical Co. (St. Louis, Mo.,
orless compounds are formed at inter- volved in caramelization is a prerequi- U.S.A.). All the other chemicals used
mediate stages, whereas the brown site for understanding the Maillard re- were of the purest commercially avail-
polymers are formed at final stages action (Mauron 1981). It has, however, able grade.
(Hodge 1953; Mauron 1981).
been clearly established that the frag-
Heating procedure
The nonenzymatic browning reac- mentation of sugars occurs to a signifi-
tion of fructose has not been as thor- cant extent at pH values below neutrali-
oughly investigated as that of glucose, ty (O’Beirne 1986; Buera and others
and it has usually been compared to the 1987) and increases considerably at
latter. In several early studies (Maillard high pH values and temperatures, yield-
1912; Hodge 1953; Reynolds 1965), the ing colored N-free polymers (Myers
browning of fructose aqueous solutions and Howell 1992; Clarke and others
in the presence of amino acids in model 1997). The Maillard reaction in foods
systems was found to take place more may then be overestimated and the em-
rapidly than that of glucose, although phasis placed on its detrimental rather
the contrary was also reported to occur than its beneficial effects.
An equimolar (0.05 M) mixture of
fructose and lysine (3 mL) was heated
in a 15-ml screw-sealed tubes for vari-
ous periods of time in boiling water at
various pH values. After 5, 15, 30, 60, 90,
and 120 min, the tubes were removed
and immediately cooled in ice. Part of
the heated solution was used directly
for UV-absorbance, browning, and final
pH measurements, while the rest was
926 JOURNAL OF FOOD SCIENCE—Vol. 66, No. 7, 2001
© 2001 Institute of Food Technologists

Maillard and Caramelization Reaction Kinetics . . .
stored at –20 ЊC for fructose and lysine intensity of the aqueous solutions con- well as in glucose solutions containing
loss determinations. Fructose and taining fructose or fructose and lysine either lysine, or methionine or threo-
lysine were separately heated under the were measured at room temperature at nine when heated to 100 ЊC at different
same experimental conditions. The fol- 294 nm and 420 nm, respectively, using pH values (Ajandouz and Puigserver
lowing buffers were used: 0.05 M sodi- a Beckman model DU 640 spectropho- 1999). In a number of studies in which
um acetate adjusted to pH 4.0 with 1 M tometer (Beckman Instruments, Irwin, proteins were heated in the presence of
acetic acid, 0.05 M sodium phosphate Calif., U.S.A.). When necessary, appro- reducing sugars at an intermediate
adjusted to pH 6.0, pH 7.0 and pH 8.0 priate dilutions were made in order to moisture content and a wide range of
using either monobasic or dibasic sodi- obtain an optical density of less than temperatures, a no-loss period was
um phosphate, 0.05 M Tris-carbonate 1.5.
found to occur when 50 to 75% of the
adjusted to pH 9.0 with 1 M hydrochlo-
All the experiments were carried out lysine was destroyed (Wolf and Thomp-
ric acid, 0.05 M sodium carbonate-bi- in triplicate and the mean values (over- son 1977; Labuza and Saltmarch 1981).
carbonate adjusted to pH 10.0 and pH all less than 10% standard deviation) The no-loss period might be due to
11.0 using either sodium carbonate or were used to draw up the kinetic plots.
sodium bicarbonate, and finally 0.05 M
some limitation in the reactants or to
the release of amino groups at ad-
vanced stages of the Maillard reaction.
The decrease in pH throughout the
heat treatment may also contribute to
the progressive lowering of the rates of
Results and Discussion
sodium bicarbonate adjusted to pH
12.0 with 1 M sodium hydroxide.
Early stages in the browning
reactions
Fructose loss
The initial stages in the nonenzymat- lysine loss. Under our experimental
ic browning reaction of the heated fruc- conditions, a pH drop of 0.25-3.8 units
tose solutions, with or without lysine, and of 0.5 to 1.8 units occurred in fruc-
was studied by measuring the extent of tose and fructose-lysine model systems
fructose and lysine degradation over after a 2-h heating period at starting pH
time. As expected, an increase in pH of values of 6.0 to 12.0, respectively. A
the heated solutions led to an increase more severe pH decrease has been re-
in the initial rate of degradation of both ported in unbuffered solutions of gly-
fructose and lysine (Figure 1). Lysine cine and glucose (Nicoli and others
degradation was already reduced at pH 1993). More attention should, therefore,
8.0, since it did not exceed 22% of the be paid to the pH decrease during non-
amino acid after 2 h of boiling, and only enzymatic browning reactions, espe-
5% after 15 min as compared to higher cially at intermediate moisture content
pH values (13 to 34% loss after 15 min and pH values below neutrality.
The remaining nondegraded fruc-
tose was monitored on high-perfor-
mance anion exchange-pulsed ampero-
metric detection equipment. Fructose
was eluted under isocratic conditions
from the CarboPac PA-100 (Dionex
Corp., Sunnyvale, Calif., U.S.A.) analyti-
cal anion exchange column (250 ϫ 4
mm) equipped with an IonPac AG4A-
SC (Dionex Corp., Sunnyvale, Calif.,
U.S.A.) guard column (25 ϫ 4 mm) con-
nected to a gold working electrode cell.
The eluent, a 5 mM sodium acetate so-
lution containing 0.1 M NaOH, was de-
livered at a rate of 1 mL.min–1 by a GP
40 Dionex gradient pump (Dionex
Corp.,). The injection volume was deliv-
ered by an AS 3500 Spectra System
autosampler from Thermo Separation
Products (Fremont, Calif., U.S.A.) and
the detection was carried out with an
ED 40 electrochemical detector (Dionex
Corp.). The area under the eluted peak
was integrated with an Olivetti Pentium
P 75i integrator (Olivetti, Paris, France)
using the Borwin chromatography Soft-
ware program (JMBS, Grenoble,
France), based on a 0- to 250-pmol
fructose calibration chart.
of heating at pH 9.0 to 12.0). Moreover,
Studies on the Maillard reaction
lysine loss resulted almost completely, if placing emphasis on the degradation of
not exclusively, from Maillard reaction, reducing sugars are not so numerous.
as no significant loss was observed Warmbier and others (1976) have re-
when the amino acid was heated in the ported that lysine loss was higher than
absence of fructose. Most of the loss that of glucose in a casein-glucose-glyc-
was, therefore, observed during the be- erol model system at 45 ЊC and a aw val-
ginning of heating; a no-loss period oc- ue ranging from 0.57 to 0.85, whereas
curred at later heating stages. A no-loss Baisier and Labuza (1992) have shown
period has also been observed in a gly- that glycine and glucose losses oc-
cine-containing glucose solution stored curred with the same rate constant in a
at 37 ЊC (Baisier and Labuza 1992), as solution stored at 37 ЊC. More recently,
Amino acid loss
The unreacted lysine was monitored
by performing reverse phase high-per-
formance liquid chromatography after
pre-column derivatization with phenyl-
isothiocyanate as described by Bidling-
meyer and others (1984). The eluted
amino acid was detected at 254 nm us-
ing a model 486 variable wavelength de-
tector (Waters Assoc., Milford, Mass.,
U.S.A.), and the resulting peak was inte-
grated as described above for fructose.
UV-absorbance and brown color
measurements
Figure 1—Time course of fructose (A) and lysine (B) loss in lysine-containing
fructose solutions when heated at 100 ЊC and at varying pH values.
The UV-absorbance and browning
Vol. 66, No. 7, 2001—JOURNAL OF FOOD SCIENCE 927

Maillard and Caramelization Reaction Kinetics . . .
glucose was found to be more rapidly dation was actually lowered in the pres- starting concentration of the sugar was
degraded than lysine, or methionine or ence of lysine as compared to that of the same. It is not really easy to define
threonine in solutions heated to 100 ЊC fructose alone. This protective effect precisely the respective contribution of
at pH values ranging from 4.0 to 12.0 may be due to some reversible interac- caramelization and Maillard reaction to
(Ajandouz and Puigserver 1999). When tion which takes place between the keto- the overall nonenzymatic browning.
cocoa bean extracts were heated to 150 se and the amino acid, since it was par-
Intermediate stages
ЊC for 8 min, both fructose and glucose ticularly conspicuous at pH values be-
were totally destroyed, whereas the loss tween 8.0-11.0 where the 2 lysine amino
of free amino acids did not exceed 50% groups are deprotonated. A similar pro-
(Mohr and others 1971). A high temper- tective effect has also been observed
ature may promote some carameliza- when glucose was heated in the pres-
tion reaction resulting in a higher deg- ence of lysine, methionine or threonine
radation of reducing sugar as com- (Ajandouz and Puigserver 1999). What-
pared to amino acids and, consequent- ever the pH conditions, the active con-
ly, in changing the amino group-to-re- centration of fructose in the presence of
Intermediate stages in the nonenzy-
matic browning reactions were detect-
ed by recording the UV-absorbance at
294 nm as described by Lerici and oth-
ers (1990). Figure 3 shows that, in both
the absence and presence of lysine in
the fructose solution, the higher the
starting pH value, the higher was the
absorbance. When fructose was heated
alone at initial pH values ranging from
4.0 to 7.0, a progressive accumulation
of the intermediate degradation prod-
ucts occurred as a function of time and
no lag time was observed, whereas the
hyperbolic curves which were obtained
at pH 8.0 and pH 9.0 no doubt reflected
the high level of fructose degradation
occurring during the initial stages of the
heating period (Figure 2). At higher pH
values, the UV-absorbance quickly
reached the maximum value and de-
creased thereafter, in agreement with
the almost complete degradation of
fructose during the 1st stages in the
heating period. The decrease in the UV-
absorbance may result from the trans-
formation of some intermediate prod-
ucts into brown polymers. In the pres-
ence of lysine, the amount of interme-
diate products accumulated was higher
than in the absence of lysine and fitted
a zero-order reaction model up to pH
9.0, as compared to pH 7.0 in the ab-
sence of the amino acid. Moreover,
even at pH 12.0, no decrease in the ab-
sorbance was observed. The difference
found in the kinetic behavior of fruc-
tose alone, and fructose in the presence
of lysine, might be due to the contribu-
tion of some Maillard reaction products
to the UV-absorbance, as well as to the
accelerating effect of the amino acid on
sugar caramelization reaction. As stated
by Mauron (1981), most reactions that
occur in pure sugars only at very high
temperatures take also place at much
lower temperature once they have re-
acted with amino acids. Based on the
slopes of the UV-absorbance curves of
the solutions heated between pH 4.0
and pH 7.0, the caramelization reac-
tions were found to account for as
much as 40 to 62% of the UV-absorbing
reaction products of fructose-lysine
mixtures.
ducing sugar molar ratio.
lysine is significantly different from that
As shown in Figure 2, fructose degra- in the absence of lysine, although the
Figure 2—Percentage of fructose loss when it is heated for 5 min alone or in
the presence of lysine at 100 ЊC and increasing pH values.
Figure 3—Time course of the appearance of UV-absorbance in aqueous solu-
tions of fructose (A) and in lysine-containing fructose solutions (B) after heat-
ing to 100 ЊC at increasing pH values.
Final stages
The final stages in the nonenzymatic
928 JOURNAL OF FOOD SCIENCE—Vol. 66, No. 7, 2001

Maillard and Caramelization Reaction Kinetics . . .
browning reaction of fructose heated in beginning of the heating period, re- were 25% and 43% at pH 4.0 and pH
the presence or absence of lysine were mained unchanged thereafter. The 6.0, respectively. It should be noted,
studied by measuring the absorbance at promoting effect of pH on browning however, that a 4-fold molar excess of
420 nm. The time course of the devel- development was in agreement with fructose with regard to lysine was used
opment of the brown color at increas- the literature data (Ashoor and Zent in their study and that in addition the
ing pH values is shown in Figure 4. The 1984; Petriella and others 1985; Buera reactivity of lysine and glycine may not
similarity between most of these curves and others 1987; Baxter 1995).
and the UV-absorbance curves suggests The rating of fructose caramelization
be the same.
In all cases, the caramelization reac-
that a large proportion of the interme- as a percentage of the overall brown tions contributed less to the browning
diate products are precursors of brown color intensity of the lysine-containing intensity than to the overall UV-absor-
polymers. No decrease in the absor- fructose solution between pH 4.0 and bance. The UV-absorbance values are
bance at 420 nm of the fructose solu- pH 7.0 was found to be between 10 and more or less representative of interme-
tion was observed at pH 10.0 and at 36%. These values were lower than diate compounds in the nonenzymatic
pH 12.0, in sharp contrast with the UV- those obtained by Buera and others browning reactions (Hodge 1953; Lerici
absorbance and the maximum brown (1987) in an aqueous glycine-fructose and others 1990), whereas the absor-
color value, which was reached at the model system heated to 55 ЊC, which bance values at 420 nm may be related
to the content in brown polymers, and
the 294/420 nm absorbance ratio is in-
dicative of the polymerization extent.
Figure 5 illustrates the effect of pH on
the transformation of intermediates
into brown polymers in fructose and
fructose-lysine model systems after a
1-h heating period at 100 ЊC. As regards
the caramelization reaction of fructose,
a pH increase from 4.0 to 8.0 strongly
enhanced the polymerization of the
carbonyl compounds generated by the
thermal degradation of fructose,
whereas at a higher pH value, the inter-
mediates were almost equally trans-
formed into brown polymers. When
fructose was heated in the presence of
lysine at a pH value between 4.0 and
8.0, formation of the intermediate poly-
merization products decreased, where-
as above pH 8.0 the rate of polymeriza-
tion reactions of the intermediate car-
bonyl compounds seem not to be de-
pendent on both the pH and the pres-
ence of the amino acid. Figure 5 strong-
ly suggests that changes in the mecha-
nism of the nonenzymatic browning re-
action occurred around pH 8.0. Ac-
cording to the general scheme of
Hodge (1953), dealing with the chemis-
try of nonenzymatic browning reac-
tions in model systems, the Amadori
compounds are supposed to give rise
preferentially to furfurals and related
derivatives under acidic conditions,
while reductones and highly reactive di-
carbonyls are formed essentially under
alkaline conditions.
Figure 4—Time course of brown color development in aqueous solution of
fructose (A) and in lysine-containing fructose solution (B) heated to 100 ЊC at
increasing pH values. The symbols are the same as in Figure 1.
As pointed out in the introduction,
there are some conflicting data about
the reactivity of fructose as compared
to glucose as far as browning is con-
cerned. With respect to the intermedi-
ate stages of the Maillard reaction, vola-
tile compounds such as furans, pyrans,
and pyrroles have been obtained in
larger amounts from fructose than
from glucose when each sugar was
heated in the presence of â-alanine
Figure 5—Influence of pH on the transformation of UV-absorbing compounds into
brown polymers in fructose and lysine-containing fructose solutions heated to
100 ЊC for 60 min. The plots at 30 min of heating are shown in the insert.
Vol. 66, No. 7, 2001—JOURNAL OF FOOD SCIENCE 929

Maillard and Caramelization Reaction Kinetics . . .
(Nishibori and Bernhard 1993). Other shown in Figure 6, the caramelization tions occur with lysine limiting pro-
products with the nitrogen atoms from reaction of glucose increased exponen- teins concomitantly with carameliza-
amino acids, such as pyrazines (Amra- tially from pH 7.0 up to pH 12.0, while a tion reactions. The results shown here
ni-Hemaimi and others 1995), as well as linear increase in the rate of the cara- throw some light on these questions.
more specific products from aspar- melization reaction of fructose oc-
References
agine (Shu and Lawrence 1995) were curred in the same pH range. No fur-
apparently formed irrespective of the ther change was observed regarding the
nature of the reducing sugar. Some browning when lysine was added to glu-
mechanistic differences seem very likely cose and fructose solutions.
to exist between the nonenzymatic
Ajandouz EH, Puigserver A. 1999. Nonenzymatic
browning reaction of essential amino acids: Effect
of pH on caramelization and Maillard reaction
kinetics. J Agric Food Chem 1 (15): 928-943.Kato H,
Yamamoto M, Fujimaki M. 1969. Mechanisms of
browning degradation of D-fructose in special
comparison with D-glucose-glycine reaction. Agr
Biol Chem 33 (6): 939-948.
CONCLUSION???
browning reaction of fructose and that
of glucose as suggested, for example, by
the existence of a lag time in the brown-
ing of glucose solutions and not in that
of fructose solutions (Kato and others
1969; Buera and others 1987; Ajandouz
and Puigserver 1999).
N ADDITION TO YIELDING INSIGHTS
into the nonenzymatic browning re-
Amrani-Hemaimi M, Cerny C, Fay LB. 1995. Mecha-
nisms of the formation of alkyl pyrazines in the
Maillard reaction. J Agric Food Chem 43 (11): 2818-
2822.
Ashoor SH, Zent JB. 1984. Maillard browning in
common amino acids and sugars. J Food Sci 49 (5):
1206-1207.
Baisier WM, Labuza TP. 1992. Maillard browning ki-
netics in liquid model system. J Agric Food Chem
40 (5): 707-713.
Baxter JH, 1995. Free amino acid stability in reduc-
ing sugar systems. J Food Sci 60 (2): 405-408.
Bidlingmeyer BA, Cohen SA, Tarvin TL. 1984. Rapid
analysis of amino acids using pre-column deriva-
tization. J Chromatography 336 (1): 93-104.
Bobbio PA, Imasato H, De Andrade Leite SR. 1981.
Maillard reaction V: preparation and character-
ization of melanoidins from glucose and fructose
with glycine. An Acad Brazi Ciênc 53 (1): 83-86.
Buera DP, Chirife J, Resnik SL, Wetzler G. 1987. Non-
enzymatic browning in liquid model systems of
high water activity: kinetics of color changes due
to Maillard reaction between different single sug-
ars and glycine and comparison with carameliza-
tion browning. J Food Sci 52 (4): 1063-1067.
Clarke MA, Edye LA, Eggleston G. 1997. Sucrose de-
composition in aqueous solution and losses in sug-
ar manufacture and refining. Adv Carbohydr Chem
Biochem 52: 441-470.
I
action of fructose, especially at pH val-
ues of foods (below 7.0), the results of
our study may have some useful prac-
tical implications at both the food
technology and nutritional levels as to
how low alkaline conditions should be
managed, especially regarding some
plant proteins such as those from soy-
bean which may be exposed to high al-
kalinity levels during their processing.
Further studies are now required to be
able to distinguish more clearly be-
tween the caramelization reaction and
that initiated by the interaction be-
tween the sugar and protein amino
groups in food. The increase in the ali-
mentary use of free fructose during
the last 2 decades, mainly in the form
of high-fructose corn syrup (Park and
Yetly 1993), has brought to the fore the
question as to how it is degraded dur-
ing heat treatment, especially at pH
values above neutrality, and what reac-
A possible explanation of this obser-
vation might be the formation of some
rate-limiting intermediates during the
nonenzymatic browning reaction of
glucose, but not in that of fructose, as
suggested by Kato and others (1969). In
this connection, it seems very likely that
multiple Heyns products rather than a
single Amadori product are formed in
the Maillard reaction (Suarez and oth-
ers 1989). Another point which should
certainly be taken into consideration
when comparing the reactivity of glu-
cose and fructose is the concomitant
caramelization reactions. This should
not be overlooked, as these reactions
may also give rise to a variety of prod-
ucts from each sugar (Shaw and others
1968; Yang and Montgomery 1996). As
Ellingson RC, Mueller AJ, Kemmerer KS. 1954. Dif-
ferences between fructose and glucose in the
browning reaction. Fed Proc 13: 24 (Abstr).
Friedman M. 1996. Food browning and its preven-
tion: an overview. J Agric Food Chem 44 (3): 631-
653.
Handa H, Kuroda N. 1999. Functional improvements
in dried egg white through the Maillard reaction. J.
Agric. Food Chem. 47 (5): 1845-1850.
Ho CT. 1996. Thermal generation of Maillard aroma.
In: Ikan R, editor. The Maillard reaction: conse-
quences for the chemical and life science. New York,
NY: Wiley & Sons, p. 27-53.
Hodge JE. 1953. Dehydrated foods : Chemistry of
browning reactions in model systems. J Agric Food
Chem 1 (15): 928-943.
Kato H, Yamamoto M, Fujimaki M. 1969. Mechanisms
of browning degradation of D-fructose in special
comparison with D-glucose-glycine reaction. Agr
Biol Chem 33 (6): 939-948.
Labuza TP, Saltmarch M. 1981. Kinetics of browning
and protein quality loss in whey powders during
steady state and nonsteady state storage condi-
tions. J Food Sci 47 (1): 92-96.
Lerici CR, Barbanti D, Manzano M, Cherubin S. 1990.
Early indicators of chemical changes in foods due
to enzymic or nonenzymic browning reaction.1:
Study on heat-treated model systems. Lebensm -
Wiss -Technol 23 (4): 289-294.
Maillard LC. 1912. Action des acides aminés sur les
sucres: Formation des mélanoidines par voie
méthodique. C R Hebd Séances Acad Sci. 154 (1):
66-68.
Mauron J. 1981. The Maillard reaction in food. A crit-
ical review from the nutritional standpoint. Progr
Fd Nutr Sci 5 (1): 5-35.
Mohr W, Roehrle D, Severin T. 1971. Die Bildung von
Kakaoaroma aus den Vorstufen. Fette Seifen An-
strichsm 73 (8): 515-521.
Monti SM, Ritieni A, Graziani G, Randazzo G, Man-
nina L, Segre AL, Fogliano, V. 1999. LC/MS analy-
sis and antioxidative efficiency of Maillard reac-
tion products from lactose-lysine model system. J
Agric Food Chem 47 (4): 1506-1513.
Figure 6—Effect of pH on browning development in aqueous fructose, glu-
cose, fructose-lysine and glucose-lysine model systems heated to 100 ЊC for
60 min.
Myers DV, Howell JC. 1992. Characterization and
930 JOURNAL OF FOOD SCIENCE—Vol. 66, No. 7, 2001

Maillard and Caramelization Reaction Kinetics . . .
specification of caramel colours: an overview. Fd
Chem Tox 30 (4): 356-363.
Nicoli MC, Anese M, Lerici CR. 1993. Effect of pH on
the kinetics of non-enzymatic browning in heat-
treated glucose-glycine model systems. Ital J Food Petriella C, Resnik SL, Lozano RD, Chirife J. 1985. Ki-
Sci 5 (2): 139-144.
(6): 938-942.
of glycerol on nonenzymatic browning in a solid
intermediate moisture model food system. J Food
Sci 41 (3): 528-531.
Wijewickreme AN, Kitts DD, Durance TD. 1997. Reac-
tion conditions influence the elementary composi-
tion and metal chelating affinity of nondialyzable
model Maillard reaction. J Agric Food Chem 45 (12):
4577-4583.
Park YK, Yetly EA 1993. Intakes and food sources of
fructose in the United States. Am J Clin Nutr 58 (Suppl)
: 737S-747S.
netics of deteriorative reactions in model food sys-
tems of high water activity: Color changes due to
nonenzymatic browning. J Food Sci 50 (3): 622-625.
Nishibori S, Bernhard RA. 1993. Model systems for
cookies: Volatile components formed from the reac-
tion of sugar and ␤-alanine. J Agric Food Chem 41 Reynolds TM. 1965. Chemistry of nonenzymatic Wolf JC, Thompson DR. 1977. Kinetics of available
(12): 2374-2377.
browning. II. Adv Food Res 14: 167-283.
lysine loss during thermal processing of a soy pro-
tein isolate: Reversion of no-loss to rapid-loss
phase. J Food Process Preserv 1 (4): 271-278.
O’Beirne D. 1986. Effect of pH on nonenzymatic Shaw PE, Tatum JH, Berry RE. 1968. Base-catalyzed
browning during storage in apple juice concentrate
prepared from bramley’s seedling apples. J Food Sci
51 (4): 1073-1074.
fructose degradation and its relation to nonenzy-
matic browning. J Agric Food Chem 16 (6): 979-982. Yang BY, Montgomery R. 1996. Alkaline degradation
Shu C-K, Lawrence BM. 1995. 3-Methyl-2(1H)-pyrazi-
of glucose: effect of initial concentration of reac-
O’Brien J, Morrissey PA. 1989. Nutritional and toxico-
logical aspects of the Maillard browning reaction
in foods. Crit Rev Food Sci Nutr 25 (3): 211-248.
none, the asparagine-specific Maillard products
formed from asparagine and monosaccharides. J MS 20000507
Agric Food Chem 43 (3): 779-781.
tants. Carbohydr Res 280 (1): 27-45.
Ajandouz is grateful to the Institut National de la Recherche
Agronomique for a 2-year fellowship. We also thank Mr. C.
Villard for technical assistance, and Mrs. J. Blanc for revising
the English manuscript.
O’Brien JM, Morrissey PA, Flynn A. 1994. Alteration Suarez G, Rajaram R, Oronsky AL, Garvinowicz MR.
of mineral metabolism and secondary pathology in
rats fed Maillard reaction products. In: Labuza TP,
Reineccius GA, Monnier V, O’Brien JM, Baynes J,
editors. Maillard Reactions in Chemistry, Food and
Health. Cambridge, U.K: The Royal Society of Chem- Wang MF, Jin Y, Li JG, Ho CT. 1999. Two novel beta-
istry. p. 397-401.
1989. Nonenzymatic glycation of bovine serum al-
bumin by fructose (fructation). Comparison with the
Maillard reaction initiated by glucose. J Biol Chem
264 (7): 3674-3679.
Authors are with the UMR Université Aix-
Marseille III/INRA, Marseille. Direct inquiries to
author Puigserver at: Antoine.Puigserver@
llbn.u-3mrs.fr
carboline compounds from the
Maillard reaction between xylose and tryptophane.
J Agric Food Chem 47 (1): 48-50.
Oste RE, Miller R, Sjostrom H, Noren O. 1987. Effects of
Maillard reaction products on protein digestion.
Studies on pure compounds. J Agric Food Chem 35 Warmbier HC, Schnickels RA, Labuza TP. 1976. Effect
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