Biomedical Engineering Reference
In-Depth Information
under low O 2 conditions, the loss of volatiles is considerable. 32-40 The severity of
flavor loss depends on the atmospheric composition and duration of storage. The
higher the CO 2 concentration, the lower the O 2 concentration, and the longer the
duration in CA storage, the greater the flavor loss. Disorders of apples likely to
occur in storage include bitter pit, scald, shriveling, water core, chilling injury,
coreflush or core browning, decay, and breakdown. Of these disorders, scald, core-
flush, breakdown, and decay can be modified by handling and storage practices. 41
Delays in storage, high temperature, hot weather before and during harvest, imma-
turity, high fruit nitrogen, and extended storage periods all tend to increase scald.
Controlled atmosphere and low O 2 storage reduce scald. 20,34 Coreflush, or core
browning, a common storage disorder of McIntosh apples is associated with low
storage temperature and senescence. 42 This disorder, which is accentuated by imma-
turity and excess fruit nitrogen level, generally appears in apples after 3 to 4 months
of storage at -1 to 0°C and is intensified by a further 5 to 6 days at room temperature.
Apricots, peaches, cherries, raspberries, strawberries, and plums have a short
storage life. In air at -1 to 0°C and 85 to 95% relative humidity, sweet cherries have
a storage life of about 3 weeks, sour cherries only a few days. Mature soft fruit
normally has a maximum 2-week storage life, whereas firm fruit can be stored for
2 to 4 weeks. Fresh strawberries can be held for a maximum of 10 days and rasp-
berries can be held for a maximum of 5 to 7 days at 0°C and 85 to 95% relative
humidity. Controlled atmosphere storage of soft and stone fruits can provide addi-
tional storage life. Controlled atmosphere storage of apricots using 3 to 5% CO 2
and 2 to 5% O 2 at -1 to 0°C can extend the storage life from 12 to 14 days to 18 to
20 days. 43 Similarly, storage of sweet cherries in atmospheres containing 20% CO 2
and 21% O 2 at -1 to 0°C can extend storage life for 5 to 6 weeks. 44 Recommendations
for CA storage of pears, peach, nectarine, plum, avocado, cherry, chestnut, and
kiwifruit are given in Table 5.6 . 31 For peach, the CO 2 and O 2 concentrations given
in that table may be too low. In tests with various atmospheres, Deily and Rizvi 45
found optimum gas concentrations for peach to be 10 to 15% O 2 and 15 to 25% CO 2 .
Vegetables
Recommended storage temperature, gas concentration, and storage life expectancy
of selected vegetables are given in Table 5.7 . 10 For vegetables, such as potatoes,
carrots, garlic, and horseradish, which can be successfully stored in air, controlled
atmosphere storage is not an economical option. For most other vegetables, the
benefits of CA are generally low and consequently the level of application is slight. 10
The highest level of appreciation of CA in vegetables is with broccoli, cabbage,
lettuce, asparagus, and Brussels sprouts. In broccoli, CA may extend the storage life
by 1 to 2 weeks over that normally expected in cold storage. 46,47 Optimum CA
conditions (10% CO 2 , 1% O 2 at 3 to 5°C) have been shown to retard chlorophyll
loss, flower bud senescence, and toughening of broccoli. 1 At O 2 levels below 0.5%,
however, strong off-odor and off-flavor develop. 47 A recent study by Forney et al. 48
identified ethanol, methanethiol, hydrogen sulfide, ethyl acetate, dimethyl disulfide,
acetaldehyde, methyl acetate, and octane in broccoli stored under a CA containing
0.5% O 2 . They considered the methanethiol primarily responsible for the objectionable
 
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