Biomedical Engineering Reference
In-Depth Information
C
CONTROL
HANDLED
0.6
H
H
SUCROSE
0.5
H
H
H
0.4
0.3
0.2
C
C
C
0.1
GLUCOSE
H
H
H
C
C
0.0
0
C
5
10
15
20
Days
TIME FOLLOWING HANDLING TREATMENT
FIGURE 2.2
Sucrose and glucose concentrations in control and handled norchip tubers
(7 months in storage 9°C, 90% RH) as influenced by increasing times between handling and
sugar analysis (0, 5, 10, and 20 days). (From Orr, P. H.,
ASAE Paper No. 85-6024
, American
Society of Agricultural Engineers, St. Joseph, MI, 1985. With permission.)
the amino acid tyrosine. Phenols including chlorogenic and caffeic acid are now
involved.
40
High storage temperatures after the inflection of the bruise accelerates
the development of this undesirable coloration. The undesirable color of potato chips
after months in storage is due to the rough handling of the tubers upon loading to
and unloading from the storage.
68
Usually in dry handling of potatoes, bulk scoops,
hoppers, and multi-tiered conveyors are employed. Potato-on-potato tumbling can
inflict damage to the tubers and it has been claimed
68
that a rapid increase of sucrose
in the handled samples was induced by stress on the tubers (
Figure 2.2
).
Increased
sucrose concentration that is detrimental to chip color developed in five days after
handling. Mechanical stress on the potato tubers can also stimulate the synthesis of
glycoalkaloids (an antinutrient) in the peel and the flesh.
69
High temperatures pro-
mote faster glycoalkaloid synthesis than low temperatures. Its synthesis after
mechanical injury was reportedly accomplished within 15 days. Cutting of tubers
resulted to the highest glycoalkaloid content, followed by puncturing, dropping,
hammering, and bruising.
During harvest, peas are subjected to bruising and undergo tenderization. It was
shown that even slight damage of peas during vining leads to marked changes in
their metabolism.
70
Rapid development of off-flavors of vined peas may arise after
mechanical shelling. Due to bruising sustained by peas during vining, respiration is
affected, resulting in decreased amounts of CO
2
, aldehyde, and alcohol produced.
71
Textural changes often accompany bruising. Delays between harvesting (vining) and
processing must be avoided to maintain the quality of the produce. Physical damage
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