Biomedical Engineering Reference
In-Depth Information
TABLE 5.2
Influence of Cutting on Respiration
of Broccoli and Carrots
Respiration Rate
(mL CO 2 kg -1 h -1 )
Product
10°C
20°C
Broccoli
Whole heads
59
104
Cut florets
78
147
Carrots
Whole unpeeled
9
29
Whole peeled
12
26
Julienne
65
145
Adapted from McLachlan and Stark. 27
the respiration rate of the tissue, 27,28 and most authors have observed an increase in
respiration in cut tissues ( Table 5.2 ). 2 7 The difference in respiration rate for whole
and cut produce has been attributed to differences in gas exchange area and metabolic
activity. 29 Fruits such as apples, pears, tomatoes, and avocado experience a marked
and transient increase in respiration during ripening, known as the climacteric rise,
associated with an increased production of ethylene. The rate of respiration in plant
products is also influenced by changes in O 2 and CO 2 in the atmosphere ( Table 5.3 ). 2
Exposure of fresh produce to O 2 concentrations below their tolerance limits or to
CO 2 levels above their tolerance limits ( Table 5.4 ) 2 may increase anaerobic respira-
tion and lead to development of off-flavors.
S TORAGE R EQUIREMENTSAND Q UALITY C HANGESFOR F RUITS
AND V EGETABLES
Fruits
Conditions for the optimal storage of fruits and vegetables are influenced by a variety
of factors including crop species, cultivar, growing conditions, maturity, quality
temperature, relative humidity, packaging, and storage duration. Storage under CA
and MA is influenced by the concentration of O 2 , CO 2 , ethylene, and other gases. 30
Table 5.5 1 1,31 shows CA storage conditions for the most commonly grown apple
cultivars. Storage life quality and susceptibility to disease and physiological disorder
can be modified considerably by production practices, weather, soil, and other
factors. Delay in cooling after harvest of apples, for instance, can result in reduced
storage life because of accelerated softening and ripening, and increased probability
of scald development, breakdown, and decay. 1,31 Most apple cultivars benefit from
storage at temperatures just above the freezing point of the fruit, a relative humidity
of 90 to 95%, O 2 concentration of 1 to 2%, and CO 2 level of 1 to 2% ( Table 5.6 ). 3 1
 
 
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