134 Produce Degradation: Reaction Pathways and their Prevention
Aging of the common mushroom Agaricus bisporus is characterized by a soft
and spongy texture partly due to cell growth and water migration. The senescence
mechanism of mushrooms after harvest is still unclear but CO 2 has a most important
effect on their texture (Figure 5.11). Oxygen apparently does not play a part in the
process. As a consequence, CO 2 also exhibits a marked effect on mushroom devel-
opment, as previously pointed out by Burton et al. [105]. Mushrooms stored for 7
d at 10°C under 15% CO 2 did not break their veil whatever the O 2 content. An
unbroken veil is a major quality criterion for French consumers. Therefore, CO 2 in
the marketing containers of mushrooms should be maintained at the highest level
compatible with the preservation of their whiteness.
It has been demonstrated that controlled atmosphere containing 2% O 2 and 5%
CO 2 was beneficial for intact kiwi fruit storage [106]. Fresh-cut processing of kiwi
fruit is responsible for a rapid decrease in firmness of the slices, but the mechanism
of the texture breakdown due to injury stress is not fully understood [107]. Vial [85]
demonstrated that MAP with CO 2 concentrations up to 60% did not significantly
affect their softening.
Maybe the most pronounced effect of CO 2 on firmness has been reported for
strawberries. Harker et al. [108] found that strawberries stored under air at 0°C were
firmer than at harvest and firmness was further enhanced irreversibly by CO 2 (5 to
40%) treatments, which confirms the findings of Larsen and Watkins [109] and Smith
FIGURE 5.11Residual firmness of the mushroom Agaricus bisporus L. as a function of
atmosphere composition after 7 d of storage at 10°C. Loss in firmness was measured as the
percentage of final firmness/initial firmness, both in newtons. This percentage is highly
correlated with both the opening of the cap and change in the length of the pileus. (From
Lopez-Briones, G. et al., Int. J. Food Sci. Technol., 27, 493, 1992.)
(^1510)
(^5) 2.5
5
10
15
20
0
10
20
30
40
50
60
70
80
Residual firmness (%)
CO 2 (kPa)
O 2 (kPa)