Mechanical and Temperature Effects on Shelf Life Stability of Fruits and Vegetables - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 55

TABLE 2.5
Technical Determinants of the Extent of Mechanical Damage of Potatoes
and the Corresponding Measures to Minimize Them

Factor Effect on Mechanical Damage Measure to Minimize Effect of the Factor

Falling height Increase with increased falling height Falling height should not exceed 40 cm.

Conveyor belt
speed

Increase with increased belt speed Belt speed should not exceed 0.5 m/s

Impact
surface

Hard surfaces cause more damage on
potatoes

Use of padding like plastic or rubber foam

Tuber weight Heavier tubers sustain more damage

than lighter ones

Limit the number of possible falls
Avoid right angle bends in conveyor
transfers and sharp edges

Tuber specific
gravity

High specific gravity tubers sustain
more blue discoloration

Efficient organization of unloading,
transport, grading, and dispatch

Tuber
temperature

At low temperature (4 to 6°C), tubers are
more susceptible to blue discoloration
than at higher temperatures (15 to
20°C)

Tubers are heated at the end of storage
season

Data from de Haan, P. H., Damage to potatoes, in Storage of Potatoes: Post-Harvest Behavior, Store
Design, Storage Practice, Handling, Rastovski, A. and van Es, A., Eds., Centre for Agricultural Publishing
and Documentation, Wageningen, The Netherlands, 1987, 371-380.

in the packing line by utilizing thin steel plates in place of soft pads (which are
subjected to rapid abrasion). Brushing can also bruise fruits that are sensitive, like
the incidence of rind pitting on “Meyer” lemons reported by Wild. 79 Reduction of
brushing times is needed to avoid bruising the rinds of citrus fruits. To prevent
mechanical injury in tomatoes, the following were recommended: (a) better crop
management; (b) use of improved crates for transporting; (c) filling crates at a proper
level; (d) reducing exposure to excessive temperatures; (e) more care in handling of
tomatoes in the system; (f) improving tomato grading techniques; and (g) better and
consolidated management of the postharvest handling system. 11

P ROPER P ACKAGING

Preventing the occurrence of vibration damage is the function of properly designed
packaging. If commodities are loosely packed in a container, their tendency is to
bounce and impact with one another or against the package or container walls leading
to bruising. Vibration damage can be reduced by attenuating the resonant amplitude
levels, rather than eliminating resonant frequencies from the system. 3 If the natural
frequency band of the containers in the stack is removed from the natural frequency
band of the fruits inside, then the acceleration level input to the fruits may be
significantly reduced. Pason and co-workers 34 found that less bruise damage was
sustained by apples packed in cellmaster cartons with polystyrene soft cell trays,
whereas damage was higher in traymaster cartons with paper pulp trays. Bruise