LandLearn would like to gratefully acknowledge
the input of Dr Rod Jones of DPI Knoxfield with
1 hour plus follow up time in the classroom.
This activity allows students to undertake a simple
experiment to explore the chemical process involved
in ripening fruit.
Students will be able to:
investigate the role of ethylene gas in ripening
the role other fruit plays in the ripening
conduct and present results of a scientific
Did you know that fresh tomatoes purchased at
the supermarket are rarely "fresh"? Tomatoes and
other fruit are often picked while green and transported
to storage sheds where they are stored in ventilated
conditions until ethylene gas is added to make
them ripen and turn red. Because of this artificial
ripening process they often do not have the same
flavour as a vine ripened tomato and won't keep
very long on a supermarket shelf or in the kitchen.
gas (H2C=CH2) is a colourless gas with a faint
smell that occurs naturally and is also created
by human sources such as combustion engines. The
largest natural producers of ethylene are plants.
Ethylene is manufactured and released by rapidly
growing tissues in roots, senescing (ageing) flowers,
and ripening and rotting fruit. Most fruit and
vegetables produce ethylene in small amounts however
certain fruits produce larger quantities of ethylene
and ripen rapidly and uniformly when exposed to
an external source of ethylene. Ethylene affects
the growth, development, ripening, and senescence
of all plants.
and vegetables contain receptors that bond with
ethylene gas and after the gas binds to these
sites, they quickly ripen. Ethylene actually destroys
chlorophyll thus removing the green colour from
the fruit or vegetable allowing other pigments
such as red and yellow carotenoids to be revealed.
This is why ripening produce usually changes colour.
of ethylene producing plants include apples, avocados,
bananas, melons and pears (see table 1). Ethylene-sensitive
plants that have low ethylene production include
broccoli, cabbage, cauliflower, lettuce and other
leafy greens. Storing ethylene-sensitive plants
with ethylene-producing plants can spoil fresh
1: Examples of ethylene production levels in selected
fruit and vegetables
pears, passionfruit apricot, nectarine,
peach mango, avocado, banana, cantaloupe
blackberry, strawberry lettuce, cucumber,
spinach lemon, orange, mandarin water melon,
grape, tomato (med-low)
from Jenny Jobling 'Postharvest Ethylene: Effects
of ethylene on fresh produce'. Accessed at
> Postharvest information sheets > Postharvest
Ethylene: A critical factor in quality management
growers take advantage of the ripening effects
of ethylene by picking fruit before it is ripe,
holding it under controlled gas conditions to
minimise the ethylene concentration, and then
exposing the fruit to ethylene just before taking
it to market. This enables growers to provide
consumers with newly ripened Australian-grown
apples in spring and summer, even though apples
naturally ripen in autumn.
is possible to apply these principles to ripening
fruit by placing them in a paper or plastic bag
(sealed plastic bags are more air tight) with
another already ripe high ethylene-producing fruit
(see table above). The ethylene produced by the
fruit is contained in the bag and increases in
concentration therefore stimulating ripening.
If left too long this can lead to spoiling. A
similar effect of ethylene concentration can occur
in refrigerators and shipping containers.
the role of ethylene in ripening fruit is important
for the horticulture industry. For example, picking
tomatoes when they are green reduces the amount
of time fruit spends hanging on plants where birds,
insects, disease or the weather may damage them.
Fruit is also less prone to damage during transport
when green and can be ripened when the consumer
demand is present. Withholding ethylene from fruit
and vegetables allows producers, handlers and
sellers to spread produce availability between
seasons and meet demand from consumers. In addition,
removing ethylene from storage and shipping containers
slows spoilage and reduces waste.
brown paper bags
mature green tomatoes or unripe avocados (same
degree of ripening - try a green grocer or
For levels 3-4
table 2 ask students to predict whether they
think certain fruits will ripen when placed
in a bag with other fruits, record the predictions.
Ask students to identify reasons for their
points of view.
the experiment, place a tomato in a bag with
two ripe bananas. In the second bag (the control),
place only a tomato.
students observe the tomatoes until one or
both of them ripens and record observational
as a class or investigate in groups, the effect
of the ethylene gas on the rate of ripening
of the tomatoes.
Revisit original predictions: were they proved
or disproved? What factors led to a change
in student thinking?
fruits give off more ethylene than others.
Ask students to design an experiment to investigate
which fruits release off ethylene and which
Table 2 Observations
with one tomato (control)
with one tomato and two bananas (test sample)
For level 5
students to design an experiment to test the
effects of ethylene on fruit based on some
of the information in the Background Information
and explain how they arrived at their design.
(Consider the types of thinking that benefit
the process of designing scientific experiments).
tests using different variables eg: fruit
position - light, dark, room temperature,
fridge or freezer, length of time exposed
to ethylene or the effect of different fruit
and vegetables on each other (see Table 1
for high and low ethylene producing fruit).
the saying 'it only takes one rotten apple'.
What effect does an over-ripe apple has on
a bag of apples?
Effects of ethylene on fresh produce http://www.postharvest.com.au/EthylenePDF.PDF
Grow and Gobble activity booklet available
on LandLearn Resource Booklets CD. Activities
include - 'Capturing wild yeast', 'How much starch
is in my bread?', 'How much vitamin C can you
see?', 'Browning apples', 'Curds and whey', 'Making