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THE OCCURRENCE OF STARCH
Starch makes up the nutritive reserves of many plants. During the growing season, the green leaves collect energy from the sun. This energy is transported as a sugar solution to the starch storage cells, and the sugar is converted to starch in the form of tiny granules occupying most of the cell interior.
The conversion of sugar to starch takes place by means of enzymes. Then, the following spring, enzymes are also responsible for the re-conversion of starch to sugar - released from the seed as energy for the growing plant.
STARCH DEWATERING.
The purified starch milk is discharged to a peeler centrifuge for dewatering. The peeler filtrate is recycled to starch refining. The dewatered starch is batch-wise peeled off and discharged by gravity to the moist starch hopper.
STARCH DRYING
From the moist starch hopper the starch is fed by a metering screw conveyor into a flash dryer and dried in hot air. The inlet air temperature is moderate. The dried starch is pneumatically transported to a starch silo ready for screening and bagging. The moisture of cornstarch after drying is normally 12-13 %.
Before delivery the starch is screened on a fine sieve in order to remove any scale formed in screw conveyors etc.
MODIFICATION
Most starch is used for industrial purposes. Starch is tailor made to meet the requirements of the end-user giving rise to a range of speciality products. Many and sophisticated techniques are applied. A most versatile principle comprises a three step wet modification:
By applying different reaction conditions - temperature, pH, additives - and strict process control speciality products with unique properties are made.
These speciality products are named modified starches. They still retain their original granule form and thereby resemble the native (unmodified) starch in appearance, but the modification has introduced improved qualities in the starch when cooked. The paste may have obtained improved clarity, viscosity, film-forming ability etc.
APPLICATION.
Commercial cornstarch is used in the manufacture of sweeteners, sizing of paper and textile and as a food thickener and stabilizer. The by-products are valuable feed ingredients.
Being a pure renewable natural polymer, starch has a multitude of applications.
Starch finds uses in fast food, sweets, sausages, tablets, and paper, corrugated board etc. and plays a prominent part in our everyday life.
In 2004 more than fifty percent of starch was converted to High Fructose Syrups (HFS). Per capita sweetener consumption is now evenly divided between sucrose and HFS.
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