Agriculture Reference
In-Depth Information
(a)
25
20
15
10
5
0
(b)
8
6
4
2
0
0
5
10
15
20
25
30
Evaluation period (days)
Figure 13.3
Weight loss (%) and overall quality scores in prickly pear cactus stems (cladodes) held for up to 30
days at 5
C with and without packaging in modified atmosphere. Without packaging (black:
): packaging
°
in polyethylene bags with holes (high relative humidity), MAP (light grey:
) and packaging in modified
atmospheres (dark grey:
). Vertical bars indicate standard error of the mean (Guevara
et al
. 2001, with
permission).
very slightly during all of the storage period, and there was
a close relation between them, indicating that the retention
in texture might be due to the positive effects of MA on
preventing crude fibre losses (Figure 13.4, Guevara
et al
.
2003). It is possible that the decrease in crude fibre content
was due to the decrease in the activities of enzymes such as
cellulases, hemicellulases and pectinases.
The decrease in chlorophyll (total, a and b) was the least
in cladodes that were maintained in MAP, and chlorophyl-
lase activity was very low in cladodes held in MAP
(Figure 13.5, Guevara
et al
. 2001). Therefore, the slow
decrease in chlorophyll in cladodes held in MAP is
apparently due to the decrease in the chlorophyllase activity.
The lower chlorophyllase activity in cladodes maintained
in MAP is probably due to the lower ethylene accumula-
tion or the reduced ethylene action.
MAP reduced microbial activities in cladodes stored at
5°C for up to 30 days (Figure 13.6; Guevara
et al
. 2001).
Therefore, packaging of prickly pear cactus cladodes in
MA (up to 8.6% O
2
and up to 6.9% CO
2
) and holding at
5°C for up to 30 days prolonged their storage life and
maintained their quality (Guevara
et al
. 2001; 2003). MAP
decreased the loss in water, texture, crude fibre content,
chlorophyll content and colour, and decreased the activity
of chlorophyllase, mould, yeast and mesophilic aerobic
microorganisms.
