How Does Sugar Grow?

 

Sugarcane is any one of several species of true tall perennial seed grasses native to tropical and subtropical regions of South Asia.  The stalks are jointed and measure 6 to 19 feet tall.  Sugarcane species have been interbred, so the major commercial cultivars are complex hybrids.  The main product of sugarcane is sucrose which is extracted and processed as raw material in human food or is fermented to produce ethanol.

 

Seasonal Growth

 

Health Benefits

 

History

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Sugar cane is a giant grass that is native to India, particularly the Ganges delta. However currently there are only related wild plants that reside in that region.  The classic species, thought to be a result of mutation, is no longer found anywhere in India, except in its cultivated form. The ‘sweet redd’ which is known as ‘sweet calamus’ of the Bible, was brought to the Mediterranean by caravans in the early days of import business, 3rd century B.C.

 

Propagation

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Sugarcane produces seeds, but stem cutting is the most common and efficient propagation method. There are small buds that sprout along the length of the stalk.  Cuts are made on either side of the bud and planted in the ground.  Large growers use mechanical planters that plant the cuttings or whole stalks and cover them with soil.  Cane takes approximately 1 to 2 years to reach maturity. 

 

A stand of sugar cane can be harvested many times.  Stalks re-grow after each harvest with smaller yields after each successive harvest, so they need to be freshly re-planted after two to ten harvests.

 

Harvesting

 

Harvesting is done by hand or mechanically.  

 

By hand:  First the field is set on fire which burns the leaves without hurting the stalks and roots.  Then the stalks are cut with a knife or machete right above ground level.  A skilled worker can harvest approximately 1,000 lbs. of can an hour.

 

Mechanical harvesting is done by large machines that cut the cane at the base, strip the leaves and chop the stalks into regular lengths that are then dumped into a transporter following alongside the harvester.  The remainder of the plants are blown back onto the field.  A harvester cuts over 100 tons an hour.

 

Making sugar is a complicated process divided into two stages:  Milling and refining.  These are sometimes done in two separate locations or, in the case of a large processing plant, in one big facility.

 

1. Extraction: The first step after harvest is to bring the sugarcane to a sugar mill where juice is extracted from canes by running them through a series of large roller mills that operate like the old-fashioned wringers used to squeeze water out of washed clothes a century ago.  The leftover fiber, or “bagasse”, is used to power the sugar mill and the furnaces that heat the boilers for the next step in the milling process.  

 

2.  Evaporation:

The sugar juice runs through a boiler (or series of boilers) in order to clean it of impurities.  Lime is added to settle out the dirt and the remaining  juice is reduced to a thicker syrup by boiling off the water. Mixing also stops the decay of cane sucrose into glucose and fructose. 

 

3.  Crystallization

The sugar syrup is moved to a large container where it continues to boil until conditions are right for sugar crystals to grow.  The crystallization is triggered by adding some crystals or sugar dust to initiate crystal formation.  Then the resulting mixture is poured into a centrifuge where the crystals are separated from the remaining “mother” liquid.

 

4. Drying and storage:

The crystals are then dried with hot air and moved to a storage warehouse where they await further processing or transport to a processing plant.  This sugar is still in a very raw state, dirty from storage, heavy with molasses and without the distinctive sugar taste consumers expect. 

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1.  Raw milled sugar is mixed with a heavy syrup and cleaned in a centrifuge.  This washes away the outer coating of the sugar crystals leaving a pure, clean crystal.

 

2.  The crystals are dissolved into a syrup and phosphoric acid and calcium hydroxide are added that further combine with impurities and float to the surface where they are skimmed off.  Carbon dioxide may be used instead of phosphoric acid to the same effect.

 

3.  The clarified syrup is decolorized by filtering it through a bed of activated carbon.

 

4.  The purified syrup is repeatedly crystallized under vacuum and then separated from the molasses by centrifuge to produce refined white sugar.

 

5.  Light and dark brown sugar are produced by mixing molasses back in with the white refined sugar.

 

6.  Granulated sugar is made by first thoroughly drying it and then blowing cool air through it for several days.
 

Storage

 

Fun Facts

 

Brazil, India, China, Thailand, Pakistan

  

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