Packaging and Produce Degradation 133
However, this mode of action of carbon dioxide makes it phytotoxic for much
produce and causes physiological disorders. Therefore, produce tolerance to elevated
CO 2 should be taken into account before applying this kind of atmosphere.
Some other atmospheric gases such as noble gases and nitrous oxide (N 2 O) have
also been tested for their antimicrobial effects [89]. Qadir and Hashinaga [104]
showed that N 2 O delayed and reduced lesion growth rate on some fruits inoculated
with Alternaria alternata, Penicillium expansum, Botrytis cinerea, Fusarium
oxysporum f. sp. Fragariae, Rhizopus stolonifer, Geotrichum candidum, Fusarium
oxysporum f. sp. lycopersici, and Colletotrichum acutatum, regardless of the phys-
iological nature of the fruits or group of fungi.
5.2.2.5 Effect of Gas on Quality Attributes
5.2.2.5.1 Firmness
The firmness of plant tissue is a combination of the internal pressure of the cells
(or turgor) and the resistance of the cell walls, including middle lamella integrity.
Therefore, either plasmolysis or disruption of the middle lamella results in firmness
breakdown. The mechanisms involved in these phenomena are detailed in Chapters
2 and 5 of this book.
The effect of atmosphere composition on climacteric fruit is closely associated
with ethylene production, but CA and MAP show specific effects on the firmness
retention of some plant tissue; mushroom, strawberry, and kiwi fruit slices will be
taken as examples.
FIGURE 5.10Diameter of necroses (in millimeters) caused by Monilia and Rhizopus inoc-
ulated on peaches maintained under various controlled atmospheres at 10°C (full line). Dotted
lines present data obtained from peaches kept for 2 d in normal air after controlled atmosphere.
(From Nguyen The, personal communication. With permission.)
010203040506001020
CO 2 (%)Diameter of the necroses (mm)Monilia l. (CA + 2days in air)
Monilia l.
Rhizopus st. (CA + 2days in air)
Rhizopus st.30