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					December 2006
                Icy Herbs - building quality in the mountains
                              By Dr Garth Cambray

         Adding value to agricultural products is the only way to stay
       competitive in the global economy. In this article we see how Icy
      Herbs in South Africa breaks new ground in the production of snap
                             frozen organic herbs.
 High in the mountains of the Eastern Free
 State Flip Minaar, a farmer and
 agricultural engineer has used ingenuity
 and science to perfect a way of freezing
 herbs so that the freshness stays in,
 allowing fresh herbs to be available 24
 hours a day from your freezer.

 If you freeze plant matter, such as say a
 bunch of parsley or spinach, it normally
 reduces the leaves to soggy blackened A centre pivot irrigated basil field.
 blobs. As water freezes it expands and
 crystallizes. If one looks at the structure of a cell it has a cell membrane and
 then various bodies within the cell which are also enclosed by membranes.
 Some of these contain powerful enzymes, which if released into the cell
 digest and destroy it. As the cell freezes the membranes, which are made up
 predominantly of lipids (fats) become more rigid and the ice crystals punch
 holes in the membranes. When the cell thaws out, these holes allow the
 contents of the cell to mix and rapidly digest itself, going soggy. Enzymes
 such as hydantoinases then cause browning reactions which darken and spoil
 the colour of the now soggy plant. In short, freezing spinach or lettuce is not
 an ideal way of preserving these plants.

 An alternative to freezing is snap freezing, where the temperature of the
 cells is dropped so fast that the water does not have time to crystallize -
 snap freezing can therefore actually just freeze live viable cells in a state of
 suspended life. When they thaw out they are almost exactly like they were
 when frozen.
Flip and Riana Minaars primary business was
the production of herbs for extracting essential
oils. Taking the premium grade herbs and
freezing them for export however presented a
challenge. Blast freezing plants in Europe
usually use liquid ammonia based refrigeration
systems to produce super cooled air which is
then forced past the herbs freezing them in
three or so minutes. A great idea, but a super
cooled air freezing plant would cost in the
region of $8 million. Flip Minaar put his
understanding of agricultural engineering to
good use determined to design a low cost
system able to produce better quality herbs.

After careful initial experimentation they
                                                 A dill field
determined that liquid nitrogen froze the herbs
faster than super cooled air and produced a
better quality product. The next step was to design a system capable of
handling large volumes of herbs - this is now done in a freezing tunnel with
liquid nitrogen. The advantage here over super cooled air (-40º C) is that
liquid nitrogen has a temperature of -196º C meaning that the herbs freeze
perfectly in three minutes. And thus the company Icy Herbs was born.

The farming operation has produced up to
300 tons per annum of herb matter for sale,
with 60 % of this being basil and the
remainder being Parsley, Thyme, Coriander,
Fennel, Rosemary, Oregano, Tarragon,
Chives, Garlic Chives, Sage, Spearmint, Dill,
Rocket and Marjoram. But the story goes
beyond getting the thumbs up for a quality
product both in the South African and EU
markets, its also about how science can help
                                                 Parsley and the processed
create jobs.
                                                 frozen chopped parsley
The farm currently employs 11 people in the
freezing and packaging line and approximately 100 agricultural labourers on
a varied schedule in the fields.

          Science in Africa - Africa's First On-Line Science Magazine