Biomedical Engineering Reference
In-Depth Information
symptoms of chilling injury in asparagus spears held at 0°C.
146
Compared to those
stored at 2.2°C, storage life of asparagus spears stored at 0°C was shorter due to
chilling injury. In peaches, chilling injury results in: mealiness which is characterized
by separation of mesocarp parenchyma cells, leading to increased intercellular spaces
and accumulation of pectic substances in the intercellular matrix and leatheriness
which is characterized by collapse of mesocarp parenchyma cells, increase in inter-
cellular space and accumulation of pectic substances in the intercellular matrix.
135
As internal breakdown progresses, the following changes are observed at the ultra-
structural level: dissolution of middle lamella; cell separation; irregular thickening
of primary cell wall; and plasmolysis of the mesocarp parenchyma cells.
Tomatoes are susceptible to chilling injury at temperatures below 12 to 13°C,
resulting in metabolic disorders and susceptibility to disease.
158
The following have
been observed resulting from storage below recommended temperature: (a) inhibi-
tion of the normal decrease in acidity during ripening;
159
(b) inhibition of flesh
softening and pigment synthesis;
160
(c) decline in reducing sugars;
160
(d) decline in
soluble solids;
161
(e) flavor loss;
65,125
(f) loss in ascorbic acid content;
162
and
(g) susceptibility to disease-causing microorganisms.
163
Mature green fruit cannot
tolerate temperatures below 16°C,
164
but red tomatoes can be stored at 8°C for 3 to
4 weeks. In mature green tomatoes, the major portion of injury was at the subtending
locules and on the stem end.
165
The location of the injury corresponded to the regions
where ripening was slower. Marangoni and co-workers
153
reported that chilling injury
in mature-green tomatoes involves the following events: microvesiculation of the
endoplasmic reticulum; loss of ribosomes, chloroplasts, and mitochondrial swelling;
loss of starch granules; disorganization of the internal lamellae of chloroplasts; and
grana unstacking, as well as plastoglobuli and tonoplast degradation.
MEASURES TO MINIMIZE THE DETRIMENTAL EFFECTS
OF TEMPERATURE ON THE PRODUCE
Chilling injury is a time- and temperature-dependent problem that seriously affects
marketability of many fruits and vegetables. The nature of the injury is not yet fully
understood. Until a theory is formulated to generally explain its occurrence, effective
prevention of this defect cannot be prescribed. Measures to ameliorate the injury of
agricultural crops vary for different crops. Nevertheless, scientists have proposed
several methods for reducing the susceptibility of fruits and vegetables to chilling
injury.
H
IGH
T
EMPERATURE
C
ONDITIONING
Klein and co-workers
108
carried out investigations at 38°C with apples (cv. “Anna”
and “Granny Smith”) for 4 days. They showed that after storage at 0°C, the fruits
were firmer than the control and softened more slowly during shelf life at 17°C.
The “Anna” variety favorably responded to the pre-storage heating because it usually
softens easily upon removal from storage. Retention of firmness in response to
heating was found to develop during just 1 month of cold storage compared to
4 months for “Granny Smith,” which is known to be a firm cultivar. Softening of
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