Australian Stonefruit Grower Magazine Issue 4 April 2017 | Page 25

Research
Using 1-MCP
Apples respond particularly well
to 1-MCP. Once the storage room
is filled, encapsulated 1-MCP
(SmartFresh) is mixed with water,
releasing the gas. Only tiny amounts
are required, in the order of 0.5 to
1.0 μl.L-1 (0.5-1.0 ppm). Treatment
generally takes 24 hours, after which
1-MCP is undetectable in the fruit.
Apples are ideal for this treatment
Enter 1-MCP. Molecules of
1-MCP bind irreversibly
to the ethylene receptors
within the fruit. This
not only stops the
fruit producing its own
ethylene, but also makes
it insensitive to ethylene in
the air around it.
Plums
Plums are unusual, in that they can
be hard to define as either climacteric
or non-climacteric. In many varieties
ethylene production is suppressed,
with minimal ripening after harvest.
For example, Tegan Blue, Gulfruby
and Beauty ripen with a distinct rise
in ethylene production, whereas
Angeleno, Shiro and Ruby Red are
considered suppressed climacteric
because they are the best they can plums, with little to no ethylene
be right at harvest. We don’t want increase.
apples to ripen further and soften; we
like them crisp and crunchy. Treatment with 1-MCP
Climacteric plum varieties are the most
likely to benefit from 1-MCP treatment. For these fruit
means that they can be held in a type of suspended 1-MCP can delay softening and increase storage and shelf
animation for months. As it happens, 1-MCP also protects life. For example, a recent Australian trial with Dapple
apples from scald, a serious disorder that could previously Dandy plums found a small, but significant improvement in
only be prevented by treating with the chemical DPA
(diphenylamine).
Application of 1-MCP is more problematic for products
that we DO want to ripen and soften after harvest – such
as stonefruit. The trouble is that the effects of 1-MCP wear
off at different rates for individual fruits, resulting in mixed
ripeness. An example is avocados. These respond well to
1-MCP, which both delays ripening and reduces chilling
sensitivity. This allows lower temperature storage, thereby
reducing rots during long distance export. However, the
fruit do not ripen homogenously, so trays may need to be
re-sorted to remove both hard and over-soft fruit.
Also, timing of application is critical. 1-MCP is most
effective when applied before fruit commence ripening.
Once ripening has started it initiates a cascade of other
processes within the fruit, so is pretty well impossible
to stop. So, if 1-MCP is applied to mature fruit that have
started to produce ethylene then the effects ra nge from
simply slowing ripening by a number of days to nothing at
all.
Stonefruit vary widely in how they ripen, and so how
they respond to 1-MCP.
Blackamber (A) and Red Lane (B) plums untreated or
treated with 0.5ul 1-MCP then stored at 0 or 10C for 10
days plus 6 extra days at 20C. From Minas et al, 2013.
summerfruit.com.au
April 2017 | Australian Stonefruit Grower
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