leche maillard actividad de agua
Post on 23-Feb-2018
218 Views
Preview:
TRANSCRIPT
-
7/24/2019 Leche Maillard Actividad de Agua
1/6
Maillard reaction kinetics in milk powder: Effect of water activityat mild temperatures
A.S. Pereyra Gonzales, G.B. Naranjo, G.E. Leiva, L.S. Malec*
Departamento de Qumica Organica, Area Qumica y Microbiologa de Alimentos, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Buenos Aires, Argentina
a r t i c l e i n f o
Article history:
Received 20 April 2009
Received in revised form
9 July 2009
Accepted 20 July 2009
a b s t r a c t
The kinetics of the Maillard reaction in skim milk powder was studied at a wide range of water activities
(0.310.98) under storage at mildly elevated temperature conditions (37, 50 and 60 C). The reaction rate
was determined by the loss of available lysine content using the o-phthaldialdehyde method. Water
activity affected the rate of loss of lysine above the glass transition temperature only at high water
activity values. However, the mobility of the reactants seemed to play a role in damage to lysine, as the
rate constant decreased considerably at temperatures close to the glass transition. Crystallization of
lactose did not affect the rate constant values. Water activity did not influence the temperature-
dependence of the reaction rate, although a significant increase in activation energy was observed in the
vicinity of the glass transition temperature.
2009 Elsevier Ltd. All rights reserved.
1. Introduction
Maillard reactions frequently occur between proteins and
reducing sugars in thermally-processed foods. Lysine is the main
amino acid involved in the initial states, producing an Amadori
compound in which lysine is unavailable, thereby affecting nutri-
tional value. Therefore, control of the reaction rate has been given
much attention in order to optimize processing and storage
conditions of foods prone to nonenzymatic browning (NEB) (Hur-
rell, 1990; Mauron, 1990).
In milk, NEB begins by condensation of lactose with proteins,
forming lactulosyl-lysine, a stable protein-bound Amadori product.
The high concentration of lactose and lysine-rich proteins make
milk products very sensitive to this reaction. The occurrence of
lactosylationmay not cause browning,but can lessen the nutritional
quality of milk due to the blockage of lysine, which is no longer
available for digestion (Finot, 1990; van Boekel, 1998). This reaction
is mainly induced by heat treatment. Nevertheless, some authorshave demonstrated that lactosylation also occurs during storage of
milk powder (De Block, Merchiers, & Van Renterghem, 1998;
Guyomarch, Warin, Muir, & Leaver, 2000; Kessler & Fink, 1986).
The rate of Maillard reaction is influenced by many factors, such
as temperature, water activity (aw), pH, reactant source and
concentration and the type and ratio of reducing sugar to lysine
(Labuza & Baisier, 1992). In particular, the rate of deteriorative
reactions and storage stability are related to water activity of foods.
The maximal rate of NEB reaction was reported to occur in the awrange of 0.50.75 (Kaanane & Labuza, 1989; Labuza & Saltmarch,
1981).
Glass transition has also been found to affect the kinetics of
diffusion-controlled chemical reactions such as Maillard reaction.
The high viscosity of a system below their glass transition
temperature (Tg) was associated with limited molecular mobility
and the consequent retarding of the reaction rate (Bell, Touma,
White, & Chen, 1998; Karmas, Buera, & Karel, 1992; Lievonen,
Laaksonen, & Roos, 1998). Water plasticization increases molecular
mobility, which may result in the conversion of lactose from the
amorphous state to the crystalline state (Roos & Karel, 1992). In
closed systems, lactose crystallization will induce an increase inawdue to the release of water from amorphous lactose and may also
accelerate deteriorative changes, such as NEB (Jouppila & Roos,
1994; Vuataz, 2002). Crystallization increases with increasing
relative humidity (RH) and heat treatment (Jouppila & Roos, 1994;Vuataz, 1988).
Most of the kinetic analysis of the Maillard reaction at different
aw values and temperatures has been accomplished using simple
model systems with reducing sugars and amino acids (Bell, 1996;
Buera & Karel, 1995; Karmas et al., 1992; Lievonen & Roos, 2002;
Miao & Roos, 2004) or proteins (Desrosiers, Bergeron, & Savoie,
1989; Desrosiers & Savoie, 1991; Malec, Pereyra Gonzales, Naranjo,
& Vigo, 2002). A few studies have reported browning rates during
heating of milk at different water activities, typically at tempera-
tures above 60 C (Acevedo, Schebor, & Buera, 2006; Franzen, Singh,
& Okos, 1990; Vuataz, 1988). So far, no information regarding the* Corresponding author. Tel./fax: 54 11 4576 3346.
E-mail address: malec@qo.fcen.uba.ar(L.S. Malec).
Contents lists available atScienceDirect
International Dairy Journal
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / i d a i r y j
0958-6946/$ see front matter 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.idairyj.2009.07.007
International Dairy Journal 20 (2010) 4045
mailto:malec@qo.fcen.uba.arhttp://www.sciencedirect.com/science/journal/09586946http://www.elsevier.com/locate/idairyjhttp://www.elsevier.com/locate/idairyjhttp://www.sciencedirect.com/science/journal/09586946mailto:malec@qo.fcen.uba.ar -
7/24/2019 Leche Maillard Actividad de Agua
2/6
influence of aw and temperature on Maillard reaction during
storage of milk powder at mild temperatures has been reported.
The purpose of the present work wasto evaluatethe influence of
aw on Maillard reaction kinetics in milk powder under storage at
mildly elevated temperatures. The effect of lactose crystallization
on the reaction was also analyzed. A kinetic analysis of the Maillard
reaction is difficult because it is a complicated reaction with many
consecutive and competitive steps. Here, to study the first stage of
this reaction, the loss of available lysine content was determined.
Three different temperatures were chosen to estimate activation
energies and to relate the influence of temperature and water
activity to the extent of lysine damage. Kinetic data were compared
with those of a previous study carried out in this laboratory with
a milk-like model system (Malec et al., 2002) in an attempt to
evaluate if the results obtained with the model system could be
applied to a real food.
2. Materials and methods
2.1. Materials
Commercial skim milk powder (51.7%, w/w, lactose and 34.2%,
w/w, protein, dry basis) was purchased at the local market.o-Phthaldialdehyde (OPA), N-acetyl-L-cysteine (NAC), MgCl2, K2CO3,
Mg(NO3)2, KI, KCl and K2SO4were purchased from Sigma Chemical
Co. (St. Louis, MO, USA) and potassium sorbate and sodium dode-
cylsulphate were purchased from Mallinckrodt (Hazelwood, MO,
USA).
2.2. Preparation of samples
A dispersion of milk powder (20%, w/w) with 0.06% (w/w)
potassium sorbate added as an antimicrobial agent was freeze-
dried. A Stokes freeze-dryer, model 21 (F.J. Stokes Company,
Equipment Div., Pennsalt Chem. Corp., Philadelphia, PA, USA) was
used, which operated at a40 C condenser plate temperature and
a chamber pressure of less than 100 mm Hgfor48 h.Portions of10 gof the freeze-dried sample were equilibrated at 25 C until weight
was constant in vacuum desiccators over saturated salt solutions at
the following water activities: 0.33 (MgCl2), 0.43 (K2CO3), 0.52
(Mg(NO3)2), 0.69 (KI), 0.85 (KCl) and 0.98 (K2SO4).
2.3. Kinetic study
Experiments were performed under mildly elevated storage
conditions at three temperatures: 37, 50 and 60 C. The system
equilibrated ataw0.33 was also analyzed at 30, 40 and 45C. After
the systems were equilibrated to the desired water activity, several
200 mg samples were sealed immediately into glass flasks to avoid
adsorption or desorption of water from the ambient, weighted and
stored at the different temperatures; the awwas controlled beforeheat treatment of the powder and no changes were detected due to
the transfer. Two flasks were removed from the oven at regular
periods of time and the extent of available lysine loss was deter-
mined. Control samples of the systems after equilibration at each
aw valuewithout thermal treatment were analyzed in triplicate and
designated as time zero.
Zero and first-order kinetic rate constants for loss of lysine (k)
and their standard error were calculated by linear regression
analysis of either (i) Lt L0 kt or (ii)Lt L0ekt for zero and first-
order, respectively, where Lt available lysine concentration at
time tand L0 available lysine concentration at t 0. The confi-
dence intervals were estimated for a significance level of 95% by
means of the Student t-test. Analysis of variance (ANOVA) was
performed to check if the rate constants were significantly different
from zero. The validity of the linear equations was tested by F-test
for lack of fit. Activation energies with 95% confidence limits were
estimated by the point by point analysis suggested by Labuza
(1984).
2.4. Measurement of water activity and available lysine
The water activity of the milk systems were measured using an
AquaLab Water Activity Meter Series 3TE with internal temperature
control (Decagon Devices, Inc., Pullman, WA, USA). The awat each
storage temperature was recorded. As aw may change during
storage due to crystallization and/or Maillard reaction, it was
reported as initialaw.
Available lysine was measured by the o-phthaldialdehyde/N-
acetyl-L-cysteine (OPA/NAC) spectrophotometric method (Medina
Hernandez & Garca Alvarez-Coque, 1992). For analysis, samples
were dissolved in 5% (w/v) sodium dodecylsulphate solution. To
10 mL of OPANAC reagent (25 mL of a 0.05 M ethanolic OPA
solution, 25 mL of a 0.05 M aqueous NAC solution and 200 mL of
0.02 M boric acid-borate buffer solution, pH 9.5, in 1 L of water),
2.0 mL of the sample solution were added and diluted to 25 mL
with water. Absorbance was measured at 335 nm with a Hewlett
Packard spectrophotometer HP 8453 (Hewlett Packard, Palo Alto,CA, USA). Three replicates of each sample were analyzed and, as
two flasks were taken at each time, the average of six measure-
ments is reported. The coefficient of variation for this assay was
-
7/24/2019 Leche Maillard Actividad de Agua
3/6
The first-order rate constants for available lysine loss at 37, 50
and 60 C are shown in Table 1; the extent of loss of lysine was quite
different at each temperature studied. At 50 and 60 C, significant
losses of lysine were detected only at prolonged times of heating,
too much longer than those generally used during processing of
milk products. Thus, heat treatment at mild temperatures would
not significantly affect the lysine content of milk proteins. At 37 C,
extensive losses were noticed after a few days of storage at mostawvalues analyzed. For example, when milk powder was stored at an
initial aw of 0.47, there was a 20% loss of lysine after 7 days.
Considering that, in some places, ambient temperatures are closeto
37 C, it can be concluded that long-term storage conditions of milk
powder products should be carefully controlled to maintain
nutritional quality, particularly when packages have been opened.
3.2. Effect ofawon rate constants
To analyze the effect ofawon rate constants at 37, 50 and 60C,
ln(k) values were plotted against the initial aw for the three
temperatures (Fig. 2; full lines). The curves at 50 and 60 C showed
similar trends: the rate constants of samples stored in the initialawrange 0.310.71 were not significantly different (P>0.05). There-
fore, at 50 and 60 C, no maximum values were observed at inter-
mediateaw. At an initial aw of 0.85, the rate constants decreased
slightly, and at aw of 0.97 their values were approximately four-foldlower than at the initial awof 0.70. This decrease at high awmay be
explained by the dilution of reactants and the inhibitory effect of
water, a product of the reaction (Eichner & Karel, 1972; van Boekel,
2001). Corresponding results have been reported by other authors
(Acevedo et al., 2006; Franzen et al., 1990) who found a wide awrange, 0.440.85, in which nonenzymatic browning was at
a maximum for milk powder heated at temperatures from 70 to
130 C.
At 37 C, the behaviour at intermediate and high aw was the
same. However, at the initial aw of 0.32, the Maillard reactionoccurred at a much slower rate than at aw of 0.470.70. This
substantial reduction in the rate constant at 37 C seems not to be
caused only by the decline inaw, since at 50 and 60 C no lessening
was observed at aw of 0.32. It should be noted that 37 C is very
close to the Tg reported byJouppila and Roos (1994)for skim milk
stored at aw0.33 (33 C). The effect of glass transition on Maillard
reaction was reported by many authors, since the physical state of
the matrixmay affect the rate of diffusion-controlled reactions such
as NEB. The rate of the reaction is extremely low in the vicinity of
the glass transition temperature, because of limited molecular
mobility as due to of the high viscosity of the system (Craig, Parker,
Rigby, Cairns, & Ring, 2001; Karmas et al., 1992; Lievonen et al.,
1998). At aw 0.43,Jouppila and Roos (1994) reported a Tg of 9 C,
much lower than 37
C. Hence, at this temperature, the increase inthe mobility of the reactants at awvalues above 0.33, as shown by
the dramatic rise in reaction rate, could be mainly attributed to the
plasticizing effect of water, which lessened the glass transition
temperature, rather than to the influence of water activity. Similar
results were obtained by Bell (1996), who compared the effect of
glass transition and aw on browning rate and concluded that the
rate of pigment formation was more significantly influenced by the
Tg of a material than by its aw. Unlike at 50 and 60 C, the lowest
reaction rate at 37 C occurred at the initial aw of 0.32 (Fig. 2).
Consequently, the physical state of the system would have a more
rate-limiting effect on the reaction than the dilution of the
reactants.
It must noted that, during storage at mild temperatures, lactose
could crystallize, affecting the rate of Maillard reaction by
Table 1
First-orderrate constants (k) and activationenergies (Ea) with 95% confidence limits
for available lysine loss from skim milk powder stored at 37, 50 and 60 C and
equilibrated at various water activities (aw).
aw k 103 (hs1) Ea (kJ mol1)
37 C 50 C 60 C
0.33 0.0198 0.0020 7.14 0.51 17.46 0.93
0.43 1.115 0.075 7.24 0.78 27.4 1.9 121.1 2.7
0.52 0.762 0.095 6.35 0.32 26.0 1.3 129.2 3.7
0.69 0.802 0.046 7.08 0.53 27.2 1.9 131.4 3.1
0.85 0.538 0.051 4.56 0.34 20.8 1.4 135.4 2.9
0.98 0.245 0.020 1.89 0.13 7.54 0.58 128.5 4.1
-12
-11
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
aw
lnk
Fig. 2. Effect of water activity on rate constants of loss of lysine (ln k) in skim milk
(closed symbols) and in a lactose-casein system (open symbols; Malec et al., 2002)
stored at 37 C (C, B), 50 C (:, 6) and 60 C (-, ,).
10
100
100500 150 200 250 300 350
Time (days)
Remainingavailablelys
ine(%)
Fig. 1. Loss of available lysine in skim milk stored at 37 C at initial water activities of
0.32 (:), 0.47 (C), 0.56 (6), 0.70 (,), 0.85 (A) and 0.98 (A) as a function of time.
A.S. Pereyra Gonzales et al. / International Dairy Journal 20 (2010) 404542
-
7/24/2019 Leche Maillard Actividad de Agua
4/6
increasing theawdue to the release of water from the amorphous
lactose (Jouppila & Roos, 1994; Vuataz, 2002). To analyze crystalli-
zation behaviourof lactose in systems stored at the initial aw of 0.32
and 0.43, loss of adsorbed water was recorded. When milk powder
was exposed to RH 32% and 50 C, the system did not show
decreasing water content over 200 h of storage (Fig. 3). Thus, no
crystallization of lactose occurred during the experiment. At 60 C,
a loss of adsorbed water was detected after a delay of 40 h; hence,
under these conditions, crystallization of lactose did not affect the
reaction rate, as it occurred when more than 50% lysine was lost.
Instead, at RH 43% and 37 C, adsorbed water was lost because of
lactose crystallization in a rather short time (within 23 h).
Although, at 50 and 60 C and at the same RH, faster crystallization
could be expected, there were no significant differences between
the rate constant values of samples equilibrated ataw0.33 and 0.43
at 50 and 60 C. Apparently, in this study crystallization of lactose
had no effect on the reactivity of lysine. Similar results were
reported by other authors (Morgan, Appolonia Nouzille, Baechler,
Vuataz, & Raemy, 2005; Vuataz, 1988) who suggested that, despite
the fact that an increase ofawcould accelerate NEB, crystallization
immobilizes lactose and thus less dissolved lactose is available for
reaction with proteins.
It should be noted that aw could also rise during storage, aswater is a product of Maillard reaction. However, in this study the
early stage of this reaction, which only produces a small amount of
water, was predominant, and its contribution to the overall increase
ofawwas not relevant (Vuataz, 2002).
Data reported in our previous study (Malec et al., 2002) for
a lactose-casein system stored at the same temperatures, equili-
brated to similar water activities and with the same reactant
concentrations, are included for convenient comparison in Fig. 2
(dotted lines). The kinetic constants obtained in this study were
slightly different from those corresponding to the model systems at
similar conditions. Most of the rate constants were lower (P< 0.05)
in milk powder than in the model system. The differences could be
mostly attributed to the use of phosphate buffer in the model
system; this avoids the decrease in pH due to Maillard reaction, andthus the reduction of the reaction rate throughout the experiment.
In certain conditions, such as elevated temperatures or dilute
solutions, phosphate buffers have been shown to increase the rate
of nonenzymatic browning (Bell, 1997; Potman & van Wijk, 1989;
Saunders & Jervis, 1966). Nevertheless, in low-moisture solid
systems, no enhancing effect was observed on the extent of loss of
amino acids (Bell, White, & Chen, 1998). In addition, the rate
constant values in milk powder could also be affected by the pres-
ence of salts and whey proteins. The greatest difference between
the rate constants of both systems was observed at the initial awof
0.32 and 37 C. Unlike in milk, no glass transition was detected in
the model system around 37 C and this was probably the reason
why the decrease of the reaction rate was much less. Another
notable difference was that, in themodelsystem at 37 and50 C,the
largest rate constant value was observed at an initial aw of 0.52, and
at 60 C the rate was maximal at a wider range ofaw. Instead, no
maximum was observed in milk powder stored at intermediateaw.
Therefore, the effect ofaw at intermediate values was less significant
in milk powder than in the model system, despite the similar
composition and conditions of storage of both systems.
3.3. Loss of lysine and temperature-dependence
The rate constants of the systems equilibrated at the six
different aw values increased with increasing temperature. Thetemperature-dependence of the kinetic constants was analyzed
using the Arrhenius equation. Linear relationships were obtained
when ln k wasplotted against T1 for the systems equilibrated at aw0.430.98. The activation energies (Ea) of the Maillard reaction
calculated for systems equilibrated at aw 0.430.98 are shown in
Table 1, together with their 95% confidence limits. The values varied
from 121 to 135 kJ mol1 and were within the range found by other
authors for loss of lysine in milk-related systems (Kessler & Fink,
1986; Malec et al., 2002; Morales, Romero, & Jimenez-Perez, 1995;
Naranjo et al., 1998). Some authors (Malec et al., 2002; Miao & Roos,
2004) found a higher temperature-dependence of Maillard reaction
with decreasing moisture content. However, in this study, the water
activity did not affect the temperature-dependence of the rate of
loss of lysine, as Ea values for the systems equilibrated at awvaluesof 0.430.98 were not significantly different (P> 0.05).
Regarding the Arrhenius plot of the system equilibrated at aw0.33, no linear relationship was observed. In order to analyze the
temperature-dependence of kinetics of lysine loss at this aw, value
other temperatures near Tg were studied (30, 40 and 45 C). The
equation was fitted to the experimental data in three parts, with
different slopes (Fig. 4). The shape of the figure was similar to those
0
1
2
3
4
5
6
7
8
9
10
0 10 20 30 40 50 60 70 80 90 100
Time (h)
Waterconten
t(g100-1g
solids)
Fig. 3. Water sorption of skim milk powder stored at relative humidities of 32% (C),
31% (-) and 43% (:) at 50 C, 60 C and 37 C, respectively as a function of storage
time.
-12
-10
-8
-6
-4
-2
0
0.00295 0.003 0.00305 0.0031 0.00315 0.0032 0.00325 0.0033 0.00335
1/T (K-1
)
lnk
Tg = 33 C
Fig. 4. Arrhenius plot for loss of lysine in skim milk equilibrated at aw0.33.
A.S. Pereyra Gonzales et al. / International Dairy Journal 20 (2010) 4045 43
-
7/24/2019 Leche Maillard Actividad de Agua
5/6
reported previously for browning rate in different model systems
(Karmas et al., 1992; Lievonen & Roos, 2002). Three zones were
observed and the three straight lines corresponded to temperature
ranges of 3040 C, 4050 C and 5060 C. The activation energies
for lysine loss were calculated separately for each temperature
range and were 65.2, 498.0 and 79.9 kJ mol1, respectively. Ea in
the intermediate region (4050 C) was considerably higher than
the two others, and also much higher than typical values for the
Maillard reaction. This higher temperature-dependence of the
reaction rates was explained by the abrupt change of the viscosity
of the system above the glass transition temperature. In the present
study, the break was observed at 7 C above Tg, which was in
agreement with previous studies ofKarmas et al. (1992), Lievonen
and Roos (2002) and Roos, Jouppila, and Zielasko (1996), who
reported that a large increase in NEB occurred at a range of
2 C40 C above Tg. At 30 C, where the system was in the glassy
state, the Maillard reaction still occurred, although at a very low
rate, and the Ea corresponding to the temperature range in the
vicinity of the Tg (3040 C) was lower than the usual values
reported for the loss of lysine (85166 kJ mol1)(Kessler & Fink,
1986; Labuza & Saltmarch, 1981; Malec et al., 2002; Naranjo et al.,
1998). The second break occurred at 13 C above the Tg and the Ea
at the higher temperature zone (5060 C) was closer to the rangeof rate constant values for the loss of lysine informed above, indi-
cating that at temperatures well above Tg, the reaction became
diffusion-controlled and followed Arrhenius kinetics.
4. Conclusions
In contrast to the results obtained in our previous study with
a milk-like model system, the effect ofaw above the glass transition
on the rate of loss of lysine by mildheattreatment orduring storage
of milk powder was only significant at high aw values, and the
temperature-dependence of the reaction rate was not affected by
aw. However, the mobility of the reactants seemed to play a role in
lysine damage. Although the Maillard reaction did not stop in the
glassy state, the rate constant decreased considerably at tempera-
tures close toTg. The influence ofaw on Maillard reaction kinetics in
milk powder can be interpreted as a consequence of concentration
and diffusion of reactants. A dilution effect was observed ataw over
0.7, which was independent of the temperature of the system, at
least up to mild temperatures. At low aw, loss of lysine decreased
only at temperature conditions where the high viscosity affected
molecular diffusion. For this reason, as milk powder is commonly
exposed to extended periods of storage, it is critical to keep the
system at temperature andaw conditions below the glass transition
in order to minimize its nutritional damage.
Acknowledgements
This work was supported by grants UBACYT X021 and UBACYT
X062 from Secretara de Ciencia y Tecnica de la Universidad de
Buenos Aires.
References
Acevedo, N., Schebor, C., & Buera, M. P. (2006). Watersolids interactions, matrixstructural properties and the rate of non-enzymatic browning. Journal of FoodEngineering, 77, 11081115.
Baisier, W. M., & Labuza, T. P. (1992). Maillard browning kinetics in a liquid modelsystem. Journal of Agricultural and Food Chemistry, 40 , 707713.
Bell, L. N. (1996). Kinetics of non-enzymatic browning in amorphous solid systems:distinguishing the effects of water activity and the glass transition. FoodResearch International, 28, 591597.
Bell, L. (1997). Maillard reaction as influenced by buffer type and concentration.
Food Chemistry, 59, 143147.
Bell, L. N., Touma, D. E., White, K. L., & Chen, Y.-H. (1998). Glycine loss and Maillardbrowning as related to the glass transition in a model system. Journal of FoodScience, 63, 625628.
Bell, L. N., White, K. L., & Chen, Y.-H. (1998). Maillard reaction in glassy low-mois-ture solids as affected by buffer type and concentration. Journal of Food Science,63, 785788.
van Boekel, M. A. J. S. (1998). Effect of heating on Maillard reactions in milk. FoodChemistry, 62, 403414.
van Boekel, M. A. J. S. (2001). Kinetic aspects of the Maillard reaction: a criticalreview.Nahrung, 45, 150159.
Buera, M. P., & Karel, M. (1995). Effect of physical changes on the rates of nonen-zymic browning and related reactions. Food Chemistry, 52, 167173.
Craig, I. D., Parker, R., Rigby, N. M., Cairns, P., & Ring, S. G. (2001). Maillard reactionkinetics in model preservation systems in the vicinity of the glass transition:experiment and theory. Journal of Agricultural and Food Chemistry, 49,47064712.
De Block, J., Merchiers, M., & Van Renterghem, R. (1998). Capillary electrophoresis ofthe whey protein fraction of milk powders. A possible method for monitoringstorage conditions. International Dairy Journal, 8, 787792.
Desrosiers, T., Bergeron, G., & Savoie, L. (1989). In vitro digestibility of thermallyprocessed diafiltered whey as influenced by water activity. Journal of DairyScience, 70, 24762485.
Desrosiers, T., & Savoie, L. (1991). Extent of damage to amino acid availability ofwhey protein heated with sugar. Journal of Dairy Research, 58, 431441.
Eichner, K., & Karel, M. (1972). The influence of water content and water activity onthe sugar-amino browning reaction in model systems under various conditions.
Journal of Agricultural and Food Chemistry, 20, 218223.Finot, P. A. (1990). Metabolism and physiological effects of Maillard reaction
products (MRP). In P. A. Finot, H. U. Aeschbacher, R. F. Hurrell, & R. Liardon(Eds.), The Maillard reaction in food processing, human nutrition and physiology(pp. 259272). Basel, Switzerland: Birkhauser Verlag.
Franzen, K., Singh, R. K., & Okos, M. (1990). Kinetics of nonenzymatic browning indried skim milk. Journal of Food Engineering, 11, 225239.
Guyomarch, F., Warin, F., Muir, D. D., & Leaver, J. (2000). Lactosylation of milkproteins during the manufacture and storage of skim milk powders. Interna-tional Dairy Journal, 10, 863872.
Hurrell, R. F. (1990). Influence of the Maillard reaction on the nutritional valueof foods. In P. A. Finot, H. U. Aeschbacher, R. F. Hurrell, & R. Liardon (Eds.),The Maillard reaction in food processing, human nutrition and physiology (pp.245258). Basel, Switzerland: Birkhauser Verlag.
Jouppila, K., & Roos, Y. H. (1994). Glass transition and crystallization in milkpowders. Journal of Dairy Science, 77, 29072915.
Kaanane, A., & Labuza, T. P. (1989). The Maillard reaction in foods. In J. Baynes (Ed.),The Maillard reaction in aging, diabetes and nutrition (pp. 301327). New York,NY, USA: A.R. Liss Press, Inc.
Karmas, R., Buera, M. P., & Karel, M. (1992). Effect of glass transition on rates ofnonenzymatic browning in food systems. Journal of Agricultural and Food
Chemistry, 40, 873879.Kessler, H.-G., & Fink, R. (1986). Changes in heated and stored milk with an inter-pretation by reaction kinetics. Journal of Food Science, 51, 11051111, 1155.
Labuza, T. P. (1984). Application of chemical kinetics to deterioration of foods.Journal of Chemical Education, 61, 348358.
Labuza, T. P., & Baisier, W. M. (1992). The kinetics of nonenzymatic browning. InH. Schwartzberg, & R. Hartel (Eds.), Physical chemistry of foods (pp. 595649).New York, NY, USA: Marcel Dekker.
Labuza, T. P., & Saltmarch, M. (1981). The nonenzymatic browning reaction asaffected by water in foods. In L. Rockland, & G. F. Stewart (Eds.), Water activityinfluences on food quality (pp. 605650). New York, NY, USA: Academic Press.
Lievonen, S. M., Laaksonen, T. J., & Roos, Y. H. (1998). Glass transition and reactionrates: nonenzymatic browning in glassy and liquid systems. Journal of Agri-cultural and Food Chemistry, 46, 27782784.
Lievonen, S. M., & Roos, Y. H. (2002). Nonenzymatic browning in amorphous foodmodels:effectsof glass transitionand water.Journalof FoodScience, 67, 21002106.
Malec, L. S., Pereyra Gonzales, A. S., Naranjo, G. B., & Vigo, M. S. (2002). Influence ofwater activity and storage temperature on lysine availability of a milk likesystem.Food Research International, 35, 849853.
Mauron, J. (1990). Influence of processing on protein quality. Journal of NutritionalScience and Vitaminology, 36(Suppl. 1), 5769.
Medina Hernandez, M. J., & Garca Alvarez-Coque, M. C. (1992). Available lysine inprotein, assay using o-phthaladehyde/N-acetyl-L-cysteine spectrophotometricmethod. Journal of Food Science, 57, 503505.
Miao, S., & Roos, Y. (2004). Nonenzymatic browning kinetics of a carbohydrate-based low-moisture food system at temperatures applicable to spray drying.
Journal of Agricultural and Food Chemistry, 52, 52505257.Morales, F. J., Romero, C., & Jimenez-Perez, S. (1995). New methodologies for
kinetic study of 5-(hydroxymethyl)-furfural formation and reactive lysineblockage in heat-treated milk and model systems.Journal of Food Protection, 58 ,310315.
Morgan, F., Appolonia Nouzille, C., Baechler, R., Vuataz, G., & Raemy, A. (2005).Lactose crystallisation and early Maillard reaction in skim milk powder andwhey protein concentrates. Lait, 85, 315323.
Naranjo, G. B., Malec, L. S., & Vigo, M. S. (1998). Reducing sugars effect on availablelysine loss of casein by moderate heat treatment. Food Chemistry, 62, 309313.
Potman, R. P., & van Wijk, T. A. (1989). Mechanistic studies of the Maillard reactionwith emphasis on phosphate-mediated catalysis. In T. H. Parliament, R. J. Mc
A.S. Pereyra Gonzales et al. / International Dairy Journal 20 (2010) 404544
-
7/24/2019 Leche Maillard Actividad de Agua
6/6
Gorrin, & C.-T. Ho (Eds.), Thermal generation of aromas (pp. 182195). Wash-ington, DC, USA: American Chemical Society.
Roos, Y., Jouppila, K., & Zielasko, B. (1996). Non-enzymatic browning-induced waterplasticization. Glass transition temperature depression and reaction kineticsdetermination using DSC. Journal of Thermal Analysis, 47, 14371450.
Roos, Y., & Karel, M. (1992). Crystallization of amorphous lactose. Journal of FoodScience, 57, 775777.
Saunders, J., & Jervis, F. (1966). The role of buffer salts in nonenzymatic browning.Journal of the Science of Food and Agriculture, 17, 245249.
Vuataz, G. (1988). Preservation of skim-milk powders: role of water activity andtemperature in lactose crystallization and lysine loss. In C. C. Seow (Ed.), Food
preservation by water activity control (pp. 73101). Amsterdam, TheNetherlands: Elsevier Applied Science.
Vuataz, G. (2002). The phase diagram of milk: a new tool for optimising. Lait, 82,485500.
Warren, R. M., & Labuza, T. P. (1977). Comparison of chemically measured availablelysine with relative nutritive value measured by a Tetrahymenabioassay duringearly stages of nonenzymatic browning. Journal of Food Science, 42 , 429431.
A.S. Pereyra Gonzales et al. / International Dairy Journal 20 (2010) 4045 45
top related