We face urgent challenges as we move ever closer to 2050, when it is predicted that the world’s population will reach more than 9 billion and our growing global population will face food shortages if we cannot double food production. An important contribution to this effort can come from reducing food waste. Improved food production processes and innovations in technology must play a part in ensuring that from field to fork, food wastage is significantly reduced.

1. W
e face urgent challenges
as we move ever closer
to 2050, when it is
predicted that the world’s
population will reach
more than 9 billion and
our growing global
population will face food
shortages if we cannot
double food production. An important contribution to this effort
can come from reducing food waste. Improved food production
processes and innovations in technology must play a part in
ensuring that from field to fork, food wastage is significantly
reduced.
In terms of meeting this growing demand, the outlook does
not look promising in light of prevailing circumstances around
the world. Drought areas are expanding rapidly, while natural
resources are drying up faster than expected. Further still, the
denial of global warming by some means that we do not have
a clear picture as to how urgently we need to act. However,
organisations such as the International Rice Research Institute
are playing a pivotal part in the development of high yielding,
drought resistant rice varieties.
Under these circumstances the only sensible response is to work
to save food throughout the production process. Food saving
is not only a matter for the future, but a thing we must turn our
attention to now.
If we consider today’s post-harvest handling, at every step
there are tremendous losses involved in turning crops into food.
In the rice milling industry alone, the yield of finished rice can
be as low as 40 percent, with 30 percent broken rice resulting as
a by-product. However, broken rice can still be processed into
usable rice, with specific characteristics, with the help of state of
the art technology. Bühler is just one company at the forefront of
producing top quality reconstituted rice that is indistinguishable
from the natural product.
In terms of the overall process about 15 percent of rice is lost,
as a raw material, when it makes its way to the milling facility.
A further 20 percent is lost due to moisture problems giving a
total loss amounting to about 35 percent just in raw material
form. Therefore broken rice production in the milling process
should be regarded as a serious issue. Milling machines are
generally blamed for breaking rice but, with the right technology,
the cracking of rice can be minimised. Rice is a delicate natural
material and should be treated as such.
Cracked grains are the product of excessive breaks, which are
formed in the grains by the drying operation and during storage.
Grain is often cracked under the influence of stresses, namely 1)
moisture stress, 2) thermal stress, and 3) mechanical stress.
Mechanical stress is easily understandable and happens during
milling. Moisture stress is created by the accumulation of
moisture on the grain surface or retained within the grain itself.
Thermal stress is generated by heat - either by internal heating
(the respiration process) or by external heat (during drying).
Grains are still alive even after they have been cut from the plant
and they will continue to breathe. Like other living things they
produce heat, carbon dioxide and moisture. If this heat and water
are not taken away immediately they create stresses in the grains,
which lead to cracking.
Freshly harvested paddies contain a lot of external moisture
that must be removed immediately. In storage paddy rice can
accumulate heat by the respiration of grains. This is harmful - not
only in terms of the grain cracking but for other qualities too.
Thus effective removal of heat during storage is essential.
If the cracking of rice cannot be avoided, cracks that form
during the drying process should be minimised at the very least.
There is a balance between the damage that might be done by
the heating involved in drying the grain and the damage done
by too much moisture. The two extremes are demanding and the
drying work should be carried out with extra care, particularly
when drying the grain’s interior. Removing moisture from the
peripheral parts of the grain is relatively quick and carried out
using a higher temperature.
However, heating the inner parts of the grain requires
more heat, which risks burning the surface and therefore the
temperature should not be too high. This temperature control will
mean that the rice is exposed to heat for longer, during which
time the moisture is able to expand within the rice grain.
Making food go further
- where saving cracked rice could help
by Dr Ye Aung, rice technician and consultant
40 | Milling and Grain
F

2. Having energy, warm moisture moves along the passages
exerting pressure against the cohesion of the rice cells. Therefore
the heat should not be too great lest the movement of moisture
be too fast, which could immediately turn the grain’s internal
passages into cracks. In this scenario heating should be halted
to slow the moisture-flow. If heating continues it could create
turbulence since moisture moves from inner to outer where heat
comes from outer to inner.
Turbulence in the passages could weaken the rice cells’
integrity and can quickly split them. Therefore, heating should
stop at the correct time – when the heat reaches the internal
moisture. Then the stoppage time should be long enough to stop
the flow of moisture completely. This kind of interval is usually
called ‘tempering’.
Therefore, the drying process is carried out in two stages with
different settings for external and internal moisture removal.
In an experiment, just putting tempering bins into the drying
sequence slashed daily broken turnover significantly. Air
temperatures were also reduced in the later phases of drying.
Apart from stress cracks, grain suffers from another kind of
crack - ignition. This is activated by humidity pressures inside
the grain and is prevalent when the internal humidity pressure is
not equal to the ambient humidity pressure.
Grains release moisture into the atmosphere when the latter
has lower humidity. A reversed scenario takes place when
grain has lower humidity than the ambient atmosphere. If this
action repeats frequently, cracks appear in the grains. This
often happens during storage when the stock is affected by
respiration heat and released moisture. This activity will stop
when the level of humidity on both sides is the same. The
moisture content of the grain at that time is called ‘equilibrium
moisture content’ (EMC) and this condition can be created by
ventilation at correct times and with correct settings. Cracked
grains are easily broken, even by the slightest impact of milling
machines. Therefore it is crucial that when designing a plant
the right equipment is carefully selected and specified by expert
consultants.
If we are able to minimise (if not prevent completely) the
cracking of grains, our world will benefit greatly. If we can save
a further one percent of the total grains harvested annually from
cracking, we will gain an extra 6 million tonnes of milled rice
out of the 600 million tons of paddy presently produced every
year.
Fortunately, innovative technology is playing an important role
in minimising breakages during processing. It is also playing
an integral role in converting any broken or cracked grains into
other useable forms: ground rice, used as an ingredient in other
products, and extruded fortified rice grains with an appearance
like that of natural rice. Saving cracked rice saves food.
“As we move ever closer to 2050
when it is predicted that the
world’s population will reach
over 9 billion. Our growing
global population will face food
shortages if we cannot increase
food production twofold”
March 2015 | 41
F
Introducing NIR calibrations
on demand.
Analyse your proteins and
cereals using the new online
service - AusScan Online.
AusScanO n l i n e
For more information visit www.aunir.co.uk
Die and roll re-working machines
O&J Højtryk A/S
Ørnevej 1, DK-6705
Esbjerg Ø
CVR.: 73 66 86 11
Phone: +45 75 14 22 55
Fax: +45 82 28 91 41
mail: info@oj-hojtryk.dk
www.oj-hojtryk.dk