Agriculture Reference
In-Depth Information
Table 5.3.
Effect of pressure treatment on tristimulus color of mango pulp (var. 'Alphanso').
E
Pressure (MPa)
Duration (min)
L
a
b
a/b
C
H
0.101
—
51.05
14.32
39.69
0.361
42.19
70.15
100
15
51.19
14.12
36.16
0.390
38.82
68.89
3.58
100
30
51.46
14.20
36.27
0.392
38.95
68.62
3.44
200
15
51.81
13.98
36.00
0.388
38.63
68.78
3.77
200
30
50.60
14.16
36.67
0.386
39.30
69.58
3.06
300
15
51.07
14.35
35.93
0.399
38.69
65.55
3.76
300
30
51.02
13.95
35.13
0.397
37.80
65.94
4.57
400
15
51.51
14.13
34.97
0.404
37.71
66.32
4.75
400
30
51.55
14.28
34.87
0.410
37.68
66.08
4.84
Source: Ahmed et al. (2005).
were less marked, presumably due to baroprotection by the
syrup. Overall, lychee POD was more pressure resistant
than PPO.
pulps ('Alphanso' and 'Chousa' varieties), and no signif-
icant change in color (
L
∗
,
a
∗
,and
b
∗
) of 'Chousa' pulp
was observed after HP treatment (Tables 5.3 and 5.4). The
quality parameter (
a
/
b
), chroma (
C
), and hue (
h
) remained
almost constant, indicating minimal effect on pigments.
The total color difference (
Pigment/color
Pigments (chlorophyll, carotenoids, anthocyanins, etc.)
that contribute to fruit color are generally con-
sidered to be unaffected by HP (Ahmed and
Ramaswamy, 2006). Thus, in fruit products, no visual (tris-
timulus) color changes in
L
∗
,
a
∗
,and
b
∗
values are expected
immediately after HP treatments. The color compounds
of HP processed fruits can, however, change during stor-
age due to incomplete inactivation of enzymes and micro-
organisms, which can result in undesired chemical reactions
(both enzymatic and nonenzymatic) in the food matrix.
Ahmed et al. (2005) studied the effect of HP treatment
(100-400 MPa/20
◦
C/15 and 30 min) on color of mango
E
) (equation 5.3) parame-
ters decreased with an increase in pressure intensity with
fresh pulp. Higher pressures decreased the magnitude of
E
while treatment time had no effect:
(
L
0
−
E
=
L
)
2
+
(
a
0
−
a
)
2
+
(
b
0
−
b
)
2
(5.3)
where
L
0
,
a
0
,and
b
0
represented the readings control sam-
ple, and
L, a,
and
b
represented the individual readings after
HP treatment.
Phunchaisri and Apichartsrangkoon (2005) reported that
the color of lychee sample remained unaffected when pres-
sure treatment was carried out at 20
◦
C for 20 min. The
Table 5.4.
Effect of pressure treatment on rheological parameters of mango pulp (var. 'Chousa').
Consistency
Coefficient
(
K
), Pa sec
n
Flow
Behavior
Index (
n
)
Pressure
(MPa)
Duration
(min)
Yield Stress
(Pa)
Standard
Error
0.101
—
6.242
8.82
0.338
11.12
100
15
1.151
11.91
0.327
7.83
100
30
2.219
12.09
0.270
9.47
200
15
1.085
14.81
0.260
13.05
200
30
2.657
18.55
0.245
16.28
300
15
1.348
13.26
0.268
11.79
300
30
2.956
15.97
0.267
16.12
400
15
3.779
11.73
0.293
14.31
400
30
2.273
13.45
0.278
14.02
Source: Ahmed et al. (2005).
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