FEATURE
INCORPORATING COLD CHAIN
Reducing post-harvest
losses of fruit
By Ilana Koegelenberg
F
ood waste is one of the most significant
problems facing the global food supply.
In fact, according to the United Nations,
a third of all the food produced in the world
for human consumption is wasted.
From farm to fork and beyond our
borders and oceans, we throw away more
food than people even realise. But we don’t
have to. Some food wastage will always be
unavoidable. But by strengthening the cold
chain, produce will have an improved shelf
life, increasing its chances of consumption
as opposed to simply being thrown away,
rotten, useless.
To learn more about refrigeration’s role
in reducing post-harvest losses on fruit
farms, we chat to three prominent industry
associations about their experience and
insights, looking at table grapes, citrus, and
subtropical fruit in particular.
Reducing food waste is a global
problem. But we can make a difference
locally. Through clever engineering and out-
of-the-box thinking, we can do our part in
alleviating world hunger.
HOW BIG IS THE PROBLEM REALLY?
So how much is actually wasted? It is hard
to say in South Africa specifically …
“One often hears broad statements that
30–40% of all fresh produce goes to waste.
When someone claims these figures for
export produce to discerning markets, one
tends to question the claim, since the table
grape export industry will not survive at
such high levels of waste,” explains Dawie
Moelich, manager: technical and market
access at the South African Table Grape
Industry (SATI).
Exported table grapes are seldom
wasted ‘in totality’ and when this happens,
it can usually be traced to a specific failure
of equipment. Sometimes, mild deviations
from quality specifications or non-conformity
on arrival, can have financial implications
due to a requirement for re-packing or
diversion to less-discerning buyers and lower
price structures, explains Moelich.
Accurate figures on the extent of non-
conformity leading to financial losses are
not easily available. When large claims
are received, it is essential to objectively
establish the possible cause. If an incorrect
assessment of the possible cause or causes
is made, non-appropriate ‘corrective
measures’ may be chosen, leading to
even more unintentional consequences.
“Make sure that quality claims based on
quality control (QC) reports conducted
on a limited quantity of grapes are well
substantiated, before making adjustments
to well-proven practices on a large scale,”
Moelich advises.
For citrus, it is also hard to get an exact
figure. “This is difficult to say, but I would
estimate that 3–6% of exported citrus
cannot be sold in the market,” says Dr
Tarl Berry, Citrus Research International,
Department Horticultural Science, University
of Stellenbosch. Dr Berry and his colleague
Dr Paul Cronje answered the questions on
behalf of the Citrus Growers Association of
Southern Africa.
“It is difficult to measure how much
produce is actually wasted in terms of post-
production losses,” says Kamukota Kaluwa,
South African Avocado Growers Association
(SAAGA) horticulturist / technical advisor,
on behalf of the larger Subtrop Association,
which also includes the South African
Mango Growers Association (SAMGA) and
the South African Litchi Growers Association
(SALGA). “This information varies with each
individual pack house,” he says. “Accurate
figures can be obtained from the individual
pack houses.”
It may be hard to pinpoint an exact
figure, but it is undeniable that food waste
Every link in the cold chain has a role to play in reducing food waste. Starting at the source, what role can
refrigeration play to minimise food wastage on farms?
When exporting citrus for a steri market, there are very strict regulations in terms of
temperature control. (Taken at the Fresh Produce Terminal in Cape Town.)
does occur. How can it be addressed with
the help of refrigeration?
COOLING IS KEY
Cooling from very early on is vital when it
comes to most fruits.
For table grapes for example, forced-
air cooling should ideally start as soon
as possible after the table grapes are
harvested (cut from vine), explains Moelich.
In practice, the refrigeration is delayed
for a while, to facilitate the preparation,
packing, and palletisation of table grapes.
Operationally, there is often a build-up of
harvested grape bunches produce prior
to the sorting and packing line, in which
case evaporative cooling is employed to
reduce field-heat and raise the humidity
surrounding the fruit. “There is no doubt,
though, that the sooner forced-air cooling
refrigeration can be initiated, the better,”
explains Moelich.
When it comes to subtropical fruit,
refrigeration comes in immediately after
harvest as well, explains Kaluwa. It is also
used when storing fruit in the pack house
and during transportation to the market. A
valuable step in the subtropical cold chain
from the start.
In citrus, cooling starts a bit later. The
first step of the cold chain occurs in a cold
store near to the port, explains Dr Berry.
Here the fruit is either pre-cooled using
forced-air pre-coolers, or are loaded at
ambient temperatures into the containers.
The container then reduces the product
temperature to set-point to start the
cooling process.
SHELF LIFE
When exporting fruit, refrigerated containers need to be used to ensure that the cold chain
isn’t broken and that the fruit last longer.
Refrigeration has a massive impact on the
shelf life of produce. “Storage life of fresh
fruit is directly affected by the lapse of time
and the level of temperature maintained
COLD LINK AFRICA • January/February 2019
during the multiple components of the
export chain,” says Moelich.
The grape berries, stems, and bunches
are living organisms and after removal from
the vine (harvest), metabolic processes
continue at cellular level, which eventually
leads to senescence. “Low temperature
remains the single-most effective
technology at our disposal to slow down
various processes which are associated with
the loss of quality of fresh produce, including
the rate of moisture loss,” he explains.
In the post-harvest environment,
the respiration rate of produce is most
commonly used as a parameter to explain
and demonstrate the rate of biological
activity. The respiration rate as well as the
rate of moisture loss of the grape stems
and the grape berries are very different
and present different challenges in terms of
maintenance of post-harvest quality, within
the same pack. Without refrigeration — in
combination with the barrier properties of
specific packaging components — there
would be almost no chance of marketing
table grapes in the distant markets abroad,
says Moelich. “It simply makes a lot of sense
to optimise the refrigeration process.”
It is important for citrus, too. Proper pre-
cooling is vital to reduce decay and
physiological disorder development in
citrus, confirms Dr Berry. However, more
importantly, it is used to cool fruit to comply
with phytosanitary temperature protocols to
markets like the US, China, and EU.
It should be noted that citrus fruit are non-
climacteric and are therefore harvested
after they have ripened on the tree,
explains Dr Berry. Citrus also have a relatively
low respiration rate compared to many
other fruit types. “The motivation to apply
proper cooling is therefore less motivated
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