Mechanical and Temperature Effects on Shelf Life Stability of Fruits and Vegetables - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 54

and pathogen infection of the lettuce heads increase ethylene production. Coupled
with a high temperature especially at over 5°C, russet spotting can develop during
storage and transport. Russet spotting occurs on the lower midribs of outer leaves
consisting of clusters of olive-brown spots. 72 Ethylene production can also be induced
during cold storage by fuel emission, particularly from propane, from forklift trucks,
or in retail storage rooms and in home refrigerators containing ripening fruit. 73
MEASURES TO MINIMIZE MECHANICAL INJURY
C AREFUL H ANDLING
Care should be exercised in handling fresh produce. Staff should be trained on the
proper techniques of harvesting, in placing the produce in the container, as well as
in the loading and unloading of containers for transport and storage. Loading aids
such as trolleys, roller conveyors, pallet, or forklift trucks should be used to reduce
handling of individual packages. Handling bananas by the bunch should be avoided
as this predisposes the fruits to mechanical injury. Likewise, handling of dehanded
bananas in sacks or placement of these fruits directly in the truck or ship's container
should be avoided. Bananas are dehanded and packed in boxes for transport. How-
ever, for local markets, locally available containers can be used with adequate lining
materials, such as bamboo baskets lined with newspaper. During the manual har-
vesting of fruits and vegetables such as citrus and mangos, harvesting aids like
clippers, shears, or picking poles with nets and cutting knives are employed to avoid
cuts and punctures. Pulling or plucking fruits and root crops by hand may cause
bruises and cuts at the stem end. Leafy vegetables should be packed loosely in the
container as they are very prone to damage. Bins used in harvesting fruits should
be lined. A 35 to 40% reduction was observed when the bins used in harvesting
apples were lined with foamed plastics. 30 For delicate fruits like strawberries and
starfruits, or carambolas, transfer from one container to another during picking and
handling should be avoided. 74 Potatoes taken out of bulk storage must be handled
gently and appropriate equipment must be used. Mechanical injury results when
potatoes are loaded and unloaded from the store. One likely solution to this problem,
if economics will allow, is to use palletized boxes for storage so that the handling
equipment will not be in direct contact with the tubers, and the tubers will not have
the opportunity to tumble upon each other. Fluming (wet handling) was suggested 75
as a possible means of handling potatoes to minimize tuber damage. The technical
determinants of damage in potatoes and the measures that can be taken to minimize
such damage are given in Table 2.5 .
Bruising often occurs in the packinghouse when the produce is sorted, cleaned,
graded, and packaged. Packing lines should be laid out in such a way so that the
number of transfer points and drops that the produce will undergo is minimized. As
much as 51% reduction of bruising in apples can be realized if cushioning materials
are placed on hard surfaces. 77 Schulte and co-workers 29 showed that the addition of
6.35-mm-thick Poron cushion on surfaces where apples fall can increase the maxi-
mum drop height to 226 mm before bruising occurred. Gan-Mor and Mizrach 78
introduced a new material to cushion impact and reduce fruit bruising due to impact