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Full automatic high quality potato starch production line

Efficient washing makes refining easier

The quantity of impurities adhering to the potatoes on delivery depends to a great extent on weather conditions and on the soil where the potatoes are cultivated.The quantity of water used for fluming and washing is identical with the quantity of clean water applied in the final high-pressure spray.

Rasping.

Rasping is the first step in the starch extraction. The goal is to open the tuber cells and release the starch granules. The slurry obtained can be considered as a mixture of pulp (cell walls), fruit juice and starch. With modern high-speed raspers, rasping is a one-pass operation only.

Use of Sulphur .

The cell juice is rich in sugar and protein. When opening the cells the juice is instantly exposed to air and reacts with the oxygen, forming coloured components, which may adhere to the starch.

Sulphur dioxide gas or sodium-bisulphite-solution therefore has to be added. A considerable reduction potential of the sulphur compounds prevents discoloration. Sufficient sulphur has to be added to maintain the juice and pulp light yellow.

potato starch production line machine

Potato starch production line machine

Extraction .

Operating Principle of a Starch Extractor.

The extraction is a counter current process in which the pulp-dewatering screen is actually the last step. If the pulp is required in almost dry form, the number of spray nozzles with washing water is reduced. Instead continuous back spraying is maintained to ensure that the dry pulp will slide down the screen.

Concentrating the crude starch slurry

On hydrocyclone unit as much juice is excreted as possible. The starch leaves the concentrator as pumpable slurry of approximately 19 oBe.

The concentrating stage typically consists of a unit with hydrocyclone blocks for defoaming, concentrating and starch recovering arranged in series.

Refining

It now remains to purify the crude starch milk (suspension) and remove residual fruit juice and impurities. The way it is done is more or less based on the same principles used when removing soap water from the laundry - you wring and soak in clean water again and again. Everyone doing laundry realises how often it is necessary to wring before the rinsing water is completely clear and that the harder you wring the fewer rinsing steps are required.

In the same way, the starch slurry is diluted and concentrated again and again. To save rinsing water the wash is done counter currently - i.e. the incoming fresh water is used on the very last step and the overflow is recycled for dilution on the previous step and so on.

potato starch processing machine

Potato starch processing machine

Hydrocyclones

In the strong gravitational fields of a hydrocyclone and a centrifuge, starch settle quickly, while fibres (pulp residuals) just float in the water. The juice is directly diluted in the water and goes with the water phase.

By creating a water flow moving towards the starch, lots of fibres just floating in the water may be forced into the overflow. Soil, sand and many fungi etc. are of equal density or heavier than starch and it is not possible to separate these particles from starch by centrifugal force - that is why it is so important to remove as many impurities as possible from the potato surface in the washing station.

Cooling

The lower the water consumption, the more pumps are involved in the process and the more heat is generated. To retard bacterial growth refrigerator temperatures are ideal.

In the effluent of concentrated fruit juice, cooling during extraction is a must because in hot juice microbes that break down protein and a bad smell may take control.

CIP – Cleaning in place .

Cleaning in Place is done with caustic and hypochlorite as cleaning agents. Caustic is a powerful agent for removal of the protein build-up on the interior walls and the hypochlorite is an efficient germ killer

During CIP it is of the utmost importance to keep the pipes filled up. Tanks are most efficiently CIP'ed with rotating disc nozzles - and covered tanks are required.

potato starch processing machine

Potato starch processing machine

Drying and sifting .

The moist starch from the rotating vacuum filters is dried in a flash dryer with moderate hot air. The air is indirectly heated.

Before delivery the starch is sifted on a fine sieve in order to remove any scale formed in screw conveyors etc.

Starch finds uses in fast food, sweets, sausages, tablets, and paper, corrugated board etc. and plays a prominent part in our everyday life.

 

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