Chemistry Reference
In-Depth Information
TABLE 12.3
Observed Rate Constant (
k
obs
) and Activation Energy (
E
a
) Values Found for Carotenoid
Thermal Degradation in Food Systems
Parameters
Measured
Food Systems
T
(°C)
k
obs
(min
−1
)
E
a
(kcal/mol)
Reference
Papaya puree
Total carotenoids
a
×
b
90
6.0
×
10
−3
4.91
7.78
Ahmed et al.
(2002)
4.2
×
10
−3
Pumpkin puree
Total carotenoids
L
Δ
E
90
6.51
8.04
7.26
Dutta et al.
(2006)
7.0 × 10
−3
7.0 × 10
−3
n.r.
Orange juice
90
26.27
37.26
29.33
Dhuique-Mayer
et al. (2007)
β-Carotene
β-cryptoxanthin
Zeinoxanthin
5.3 × 10
−3
4.3 × 10
−3
3.9 × 10
−3
Tomato pulp
Lycopene
100 (increased TS)
100 (constant TS)
n.r.
Sharma and Le
Maguer (1996)
2.3 × 10
−3
1.7 × 10
−3
Insoluble tomato
solids in water
Lycopene
100
n.r.
Sharma and Le
Maguer (1996)
1.3 × 10
−3
Oleoresin from
tomato cv. Roma
Total lycopene
100
11.5
Hackett et al.
(2004)
5.9 × 10
−1
Oleoresin from
tomato cv. High
lycopene
Total lycopene
100
1.97
11.7
Hackett et al.
(2004)
Oleoresin from
tomato cv.
Tangerine
Total lycopene
100
6.27
15.0
Hackett et al.
(2004)
Notes:
n.r., not reported and TS, total solids.
kinetics, and the dependence of the rate constant (
k
) followed the Arrhenius relationship. Similar
kinetic behavior of both total carotenoids and color parameters (
L
and
E
) was verii ed for the
thermal degradation of pumpkin puree blanched for 2 min in 1% NaCl solution (Dutta et al. 2006).
As a result of the heating, the CIELAB color parameters
a
,
b
, and
L
decreased indicating losses on
yellowness color and reduced luminosity due to the degradation of carotenoids and the formation of
darker compounds by parallel reactions, such as Maillard reaction (Dutta et al. 2006).
As can be seen in Table 12.3, higher activation energy
E
a
was calculated from the kinetic analysis
of the color parameters as compared to those from the decay of the total carotenoid contents. This
mismatch is a consequence of the complex thermal degradation mechanism and the type of informa-
tion that can be extracted from the analyzed parameter. For instance, color parameters are global
properties of the reacting mixture and can represent an average change between the consumption of
the starting material with the formation of new colored carotenoid species, e.g.,
cis
-isomers, epox-
ides, apo-carotenoids, and also brown-pigments formed by parallel Maillard reaction between reduc-
tive sugars and free amino groups of proteins (Machiels and Istasse 2002). On the other hand, total
carotenoid concentration also considers the increasing concentration of products, which could have
an important contribution after 10% of reactant conversion. Thus, the kinetic decay analysis at lon-
ger time and larger conversion values underestimate the degradation rate of the starting carotenoid
(usually the all-
trans
isomer) because of the formation of the other colored carotenoid products.
Mango puree was produced on a laboratory scale, mimicking typical operations in continuous
and small-size batches, applying pasteurization between 85°C and 93°C up to 16 min (Vásquez-
Caicedo et al. 2007). Although signii cant
trans
- to
cis
- isomerization of
Δ
β
-carotene occurred,
especially by the formation of 13-
cis
-
β
-carotene, provitamin A (
trans
- +
cis
-
β
-carotene) losses
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