Tomatoes - Crop Post-Harvest: Science and Technology - page 13

surface, (3) skin not torn by scraping, (4) the appearance of
brown corky tissue around the stem scar in some cultivars
and (5) the fruit size and position on the plant - larger fruit
and those borne lower on the plant are likely to be more
mature than smaller fruit higher up on the plant.
Tomatoes harvested at the mature-green stage or later
will attain better flavour upon ripening than those picked at
the immature or partially mature stages, and will be less
susceptible to water loss because of their better developed
cuticle (Kader et al . 1978c). Tomatoes harvested at the
breaker stage were superior in flavour to fruit harvested
mature green (Kavanagh et al . 1986). Vine-ripened toma-
toes will accumulate more sugars, acids and ascorbic acid,
and will develop better flavour than mature-green tomatoes
ripened off the plant (Betancourt et al . 1977; Bisogni et al .
1976; Sakiyama & Stevens 1976; Soto-Zamora et al .
2000). Tomatoes harvested over-ripe were shown to have
lower ascorbic acid content and higher ascorbate oxidase
activity (Soto-Zamora et al . 2000; Yahia et al . 2001a).
Intensities of sweetness, saltiness and fruity-floral flavour
were higher in tomatoes harvested at the table-ripe stage
than at earlier stages (Watada & Aulenbach 1978). Early
harvesting is a practice for obtaining firmer fruit suitable
for transport and to attain a longer marketable period
(Auerswald et al . 1999). However, trade journals have
begun recommending that tomatoes should be harvested at
a later, partially ripe stage to satisfy consumer demands for
better flavour (Janse & Knoys 1995; Watzl et al . 1995).
Therefore, while tomatoes for distant markets should be
picked at the mature-green or breaker stages, tomatoes for
nearby outlets can be picked at the breaker, turning, pink
or light-red stages. Cluster tomatoes are typically har-
vested at the light-red to the table-red stages and carefully
packed in single-layer, padded trays.

(Grierson & Kader 1986). Physical damage during the
handling process increases the rate of respiration, ethylene
production and fruit water loss. The physical damage also
serves as an excellent entry point for pathogens.

Fruit handling (washing, waxing and packaging)
After harvest, tomatoes are usually washed to remove
dust and other foreign materials. The wash water needs to
be warmer than the tomato pulp temperature to avoid
cooling the submerged fruit, which causes water and
microorganisms to be drawn into the fruit (Showalter
1993). The wash water may be chlorinated (100-150 ppm
chlorine) to disinfect the fruit surface and prevent
microbial inoculation (Sabaa-Srur et al . 1993). The pH of
the chlorinated water should be maintained at about 7.0 to
maintain the chemical primarily in the hypochlorous acid
form, which is the most effective sanitizer. Disinfection
of tomatoes with sodium hypochlorite before packaging
greatly reduced subsequent microbial spoilage (Bhowmik
& Pan 1992). However, chlorination has no residual effect
(Sawyer 1978), and therefore tomatoes exposed to patho-
gens after treatment remain susceptible to re-infection. A
naturally derived plant compound, trans -cinnamaldehyde,
has been shown to exhibit fungicidal effects, especially
when applied as an aqueous solution (Smid et al . 1995,
1996). Treating tomatoes with an aqueous solution of
13 mM cinnamaldehyde reduced the number of bacteria
and fungi by one order of magnitude within 10 and
30 min, respectively. With the tomatoes treated for 30 min,
visible mould growth was delayed by seven days
during storage under modified atmosphere at 18°C.
Cinnamaldehyde is not currently in commercial use for
tomato decay control.
After washing and disinfection, the fruit are usually dried
with hot air, and waxing may be done after drying, using a
heated food grade wax. Wax coating reduces water loss,
enhances gloss of the fruit and may improve the lustre
(Amarante & Banks 2001). Fungicides may be added in the
wax for protection against fruit rot pathogens (Hall 1989).
After washing and disinfection, fruit are then sorted/
graded and packaged. Automatic systems for fruit sorting
based on weight and colour are widely used in large
commercial greenhouses or packinghouses. Tomatoes
are packed in a variety of packages, depending on the type
of fruit, maturity or ripeness stage, and type of market and
market requirements. The package should be sufficiently
strong and adequately designed for sufficient ventilation,
depending on the air circulation system employed in
storage or during transit. Tomato packages are commonly
constructed from double-wall corrugated fibreboard with

Harvest
Tomatoes destined for fresh market are harvested by hand
and usually in the morning to avoid the heat of the day. In
most cases, individual fruit are removed from the vine
by gentle twisting, without tearing or pulling. For cluster
tomatoes and occasionally for cherry tomatoes, the whole
fruit cluster is cut from the plant. Tomatoes should not be
kept in the sun for an extended period of time after harvest.
Greenhouse tomato fruit are usually harvested with the
calyx and a short section of pedicel (stem) to distinguish
them from field tomatoes. The freshness of the calyx is
used as an indication of freshness and quality of the fruit.
Care must be taken to avoid the pedicel puncturing other
fruit, especially for tomatoes picked at a later stage,
because they are much more susceptible to physical injury