Water and Its Relation to Fresh Produce 277
differences between the produce and its environment. Kays (1997) described the
advantages that can be gained by air movement under closed refrigerated systems.
The higher the volume of air circulated per unit of time over the cooling coils, the
lower the differential in temperature between the return air and the delivery air. With
a small temperature differential, a decreased amount of water is removed by the
refrigeration coils, resulting in a decreased gradient in vapor pressure between the
produce and air. Therefore, controlled, increased air movement can help maintain
high humidity within the enclosed refrigeration container. Light also has an effect
on the opening and closing of stomatal apertures, and loss of water in harvested
products occurs through this avenue. The temperature of fresh produce can also be
affected by light: water loss increases at higher light intensity.
9.6 EFFECT OF INJURY ON WATER LOSS
Any form of surface mechanical injury such as bruising or abrasion accelerates water
loss from harvested fresh produce. The injury damages the surface cell tissues and
thus allows migration of water through the damaged area. Greater damage occurs
with cutting the produce because of the complete break of the protective surface
layer and direct exposure of underlying cell tissues to the atmosphere (Bolin et al.,
1991; Wills et al., 1998). In addition, any injury causes physical damage, physio-
logical stress, and increased transpiration and enhances microbial growth (McDonald
et al., 1990; Barry-Ryan and O’Beirne, 1998; Maguire et al., 2001). Hodges and
Forney (2000) reported that the degree of damage during harvesting, processing,
and packaging had an effect on increased electrolyte leakage in fresh-cut spinach
leaves. Barry-Ryan et al. (2000) found minimal processing steps such as peeling
and shredding of carrots caused physical and physiological damage and stress and
enhanced microbial growth, leading to reduced shelf compared to that of whole
carrots. However, these effects were reduced by storage in microporous film with
CO 2 permeability of 29 × 103 mL·d–1·atm–1.
Fresh-cut is a large section of fresh produce where the products are intentionally
sliced or cut into different sizes and shapes. The cuts can be peeling, slicing,
shredding, trimming, coring, or the removal of the protective epidermis cells. Watada
et al. (1996) reported that fresh-cut products (also known as lightly or minimally
processed) are highly perishable because a large proportion of their surface area is
without the epidermis, the outer protective layer of tissue, and they recommended
that the products be held at 0 to 5°C. Barry-Ryan and O’Beirne (1998) observed
that injury such as that arising from slicing of fresh produce cuts through cells,
leaving large areas of internal tissues exposed, and leads to leakage of cell contents
during subsequent storage. The total impact of physical damage is increased surface
dehydration and total moisture loss. Osornio and Chaves (1998) reported significant
exudate loss of 60% in grated beets but noted that this loss could be reduced by
proper selection of packaging material. The loss in exudate was responsible for the
dryness on the surface of the grated beets. Agar et al. (1999) found that peeling and
slicing of kiwifruit resulted in increased mass loss compared to intact whole fruit
after 3 days of storage at 2°C. Fresh-cut kiwifruits were found to have more water