Fruit Ripening & Ethylene Management Page 100
room is important to ensure uniform ripening. Suffi-
cient ventilation is required to keep CO2 levels low
(<2%) or ripening will be slowed.
Tomatoes should respond within 3-3.5 days to ethyl-
ene treatment and reach breaker-turning stages of ripe-
ness. Fruits not showing external color change by that
time indicate fruits which were immature at harvest
and which should be discarded. Once ethylene has ini-
tiated ripening and external color change, the rate of
ripening can be managed at a range of temperatures as
shown in Table 4.
Poor flavor in tomatoes harvested as mature-green
fruit and ripened may be due to:
• harvesting immature fruit rather than well developed
• long delays from harvest to final ripening
• storing at lower than recommended temperatures and
• mechanical damage which can lead to off-flavors.
Lack of uniform color in a tomato box
“Checkering-boarding” or lack of uniform coloration
is still a problem with mature-green ethylene treated
fruit and a high percentage of fruits require repacking.
Although this problem should not occur with vine-ripe
greenhouse tomatoes, it can happen if the packers are
not well trained or do not have sufficient time to dis-
tinguish between tomatoes with small differences in
external color. These small differences at the time of
packing will lead to greater heterogeneity during the
shipping and marketing period. Greenhouse fruit
should have a minimum of 20 or 30% external color to
ensure ripening uniformity in the box and to avoid
Ripening Long Shelf-life Varieties
There are many varieties and experimental tomato
lines called long shelf-life (LSL) or extended shelf-life
(ESL) varieties which contain ripening mutant genes.
Figure 4 illustrates the effects of the rin mutant on
tomato ripening physiology. If these varieties are har-
vested too early in color development, they may not be
able to attain a final full red color. Lycopene synthesis
in tomatoes is linked to ethylene production capacity.
In such cultivars, harvesting fruit with more color en-
sures they are able to complete postharvest color de-
velopment. This is the case of many varieties grown
for greenhouse production and they need to be har-
vested with 30% or more color development. The rip-
ening physiology of both so called ‘conventional’ and
‘long-shelf life’ tomato cultivars may vary substan-
tially (Table 6).
Tomato ripening and 1-MCP (SmartFresh®)
SmartFresh® or 1–MCP is a very potent inhibitor of
ethylene action in fruits and can be used to manage
fruit ripening. An example of the impact of 1-MCP on
tomato ripening is described in Table 7. Fruit at four
color stages (3.5, 4, 4.5 and 5; see color chart of ripen-
ing) were treated with 500ppb 1-MCP and then held at
15, 20 or 25°C (59, 68 or 77°F) to complete ripening.
SmartFresh® treatment substantially extended the time
to ripen and the impact was greater at lower tempera-
ture. The final firmness of the 1-MCP treated fruit can
be less than the respective control fruit since total
weight loss during ripening can be higher due to the
longer period necessary. Final red color was good in
all cases, except for some fruit stored at 25°C in which
red color development, especially of early ripening
fruit, was inhibited at this temperature. In numerous
tests we found that composition of ripe tomatoes was
similar in untreated and the 1-MCP treated fruit.
Days at 20°C from Breaker stage
T3rin x T5
Figure 4. The respiration and ethylene production
rates of tomato fruits of conventional parent (T3, T5),
mutant (T3rin) and hybrid (T3rin x T5) breeding