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Starch

Starch drying and cooling of native and modified starches are core process steps where Ingetecsa has decades of experience. With dozens of references worldwide and a unique static drying technology, we help producers achieve superior product quality, lower energy consumption, and highly hygienic operation across starch applications.

Our newest drying technology has several distinctive advantages to offer for starch applications such as:

  • Proven better product quality
  • Lower energy use, saving up to 28% when heated with steam
  • Superior hygiene as there are no moving parts in the drying zone
  • Lower maintenance and higher safety rates due to the static technology
  • Entirely indoor installation with faster installation times
Native starch

Click here to go directly to the starch drying section.

 

 

STARCH INTRODUCTION

Starch or amylum is a carbohydrate (polysaccharide) and is present
in large amounts in tubers (potatoes and cassava), and in cereals
(such as corn, wheat, and rice), and to a smaller extend in pulses,
fruits, vegetables and grasses. Starch is extracted from more than
50 types of plants. The molecules arrange themselves in the plant
in granules varying in size and in shape for each plant species.

The oldest application of starch is as a thickening as well as a gluing
agent for food products. Today, it is the most common
carbohydrate in human diets. Its applications are widespread.
Not only are food starches used as thickeners but also as stabilizers.
As a result, they provide the final characteristics of the products.
For instance the viscosity, the texture, the mouth-feel, and its
consistency.

The oldest application of starch is as a thickening and a gluing agent for food products. Today, starch is the most common carbohydrate in human diets. Its applications are widespread. Food starches are typically used as thickeners and stabilizers. They provide the characteristic viscosity, texture, mouth-feel, and consistency of many food products.

The extraction method of the starch granule depends on the plant species. Overall, starch isolation from tubers is based on breaking the vegetal cells to release the starch. Starch from cereals can be isolated by wet milling. These two groups account for the largest volumes of starch production globally. Starch extraction from pulses, fruit and vegetables is more complex and typically based on wet milling techniques.

The process of starch extraction releases at the same time several by-products such as fibres, and proteins. Each stream requires isolation as most by-products have their own applications, some with high value.

Starch is commonly mechanically dewatered from a slurry to a cake. This can be either by filter press or by centrifuge. The cake requires thermal drying to obtain the final dried starch. The final product is an unmodified starch and also named native starch.

 

Potato starch granules in potato cells

Potato starch granules captured in the cells

Drying of native starch

Since the humble beginning of our company, we have been designing and manufacturing equipment to dry starch. In the early days we dealt mostly with the wider known starches from potato, corn, wheat, cassava, and rice. Over the years also the less common starch sources such as pulses (for instance bean, pea, chickpea), locust bean gum (carob), yucca and even non-food plants such as trees (for instance sago) came into vogue. Every starch has its own specific set of functionalities.

Even today, the technology to industrially dry the dewatered starch cake is still regularly based on conventional flash dryers. Flash dryers are capable of handling high throughputs, evaporating large amounts of water, they are relatively simple in operation and the product temperature stays low enough to not change the functionality of the product. Too high a product temperature modifies the starch and its properties.

A conventional flash drying system basically consists of the following elements:

≡  The feeding system, to bring the wet starch cake in the dryer
≡  The heater, to make hot gas for drying the starch cake
≡  The flash pipe, where most of the starch dries to powder
≡  A serie of cyclones or a bag house filter, to separate the
dry starch from the drying air
≡  The exhaust fan

Simplified process flow diagram of a conventional Flash Dryer for native starch

 

Ingetecsa's Flash Dryer, offering optimised particle dispersion, aerodynamics, and possibility to dry at very high temperature

Our conventional flash dryer with top bend and very high efficiency cyclones

Top bend

In almost every conventional flash dryer, the top bend is half an annular shaped duct piece. It is merely used to create drying time and to reverse the direction of the starch flow. In the flash pipe, hot air and starch quickly travel at almost the same speed and in the same direction. This reduces the heat transfer efficiency. The top bend should disturb the direction of the air and that of the starch in order to improve the heat transfer efficiency. In a smoothly shaped duct piece, air and starch continue to travel at a reduced heat transfer. The result is a lower drying efficiency and a higher product temperature.

The Ingetecsa top bend is different. It is designed to create turbulence by changing the direction and the speed of the air and of the starch particles. The differences in speeds and directions increases the heat transfer, causing the evaporation speed to ramp up again. Higher evaporation speeds will keep the product cooled while drying. The end product is cooler than in an installation without an Ingetecsa top bend.
A cooler end product requires less heat.

This can be demonstrated in our test units.

Inefficient top bend

An inefficient top bend: A curved duct piece that only extends drying time but not improves the drying efficiency

Impact of the Ingetecsa top bend on particle quality and energy consumption

A conventional flash dryer with an Ingetecsa top bend will subject the starch particles to lower product temperatures and requires less energy.

 

Ingetecsa Flash Dryer with cyclones at Tate & Lyle Zaragoza, today Tereos

The Ingetecsa flash dryer with top bend and very high efficiency cyclones for corn starch

Eccentric feeder

The eccentric feeder has several names in the industry. Some call it a sling, or atomiser, while others describe it as a cascade or centrifugal feeder.

In every conventional starch dryer, the eccentric feeder is an element that requires some extent of ‘feeling’ of the operators to make the correct adjustments. Furthermore, it requires quite frequent cleaning, and has a significant maintenance cost.

Over the years we improved the eccentric feeder: We reduced the dimensions and substantially cut the electric power consumption. Furthermore, most of our slings in a food grade production are cleaned no more than 2-3 times a year only. Maintenance has been optimised to a once a year service interval only.

 

Developments

Ingetecsa started using a newer type of flash dryer in the end of last century. After several years of excellent feedback and results, it became our new standard for native starch drying:
The Spiral Flash Dryer.

The advantages of the Spiral Flash Dryer as opposed to the conventional flash dryer are:

≡  Proven better product quality
≡  Lower energy use, up to 28% when heated with steam
≡  Superior hygiene as no moving parts in the drying zone
≡  No eccentric feeder needed. The Spiral Flash Dryer breaks up the starch cake just by its high air speeds
≡  Lower maintenance and high safety rates due to static technology
≡  Entirely indoor installation with faster installation times

Spiral Flash Drying with Flash Cooling: proven superior product quality, compact and short installation time

 

Starch dried in a Spiral Flash Dryer typically comes out 2-3°C less warm than dried in a conventional Flash Dryer. This not only improves product quality, it also reduces the thermal energy required for the drying process.

The starch is dried so efficiently in the entire drying chamber, that the top bend has become obsolete.

Since there is no eccentric feeder anymore, no product can hold up that could burn and produce black particles. No black particles have been detected by the users of the Spiral Flash Dryer.

Our test units are available to demonstrate the above advantages.

 

Principle of operation of the Spiral Flash Dryer

Principle of operation of the entirely static Spiral Flash Dryer

Flash Cooling

Regularly we cool the dried starch and transport it to the packing line. Our Flash Cooler is ideal for this: it transports the starch while cooling the product to close to ambient temperatures. Conveying distances of in total 200m are effortless, both horizontally and vertically, and allow product to be transported to the top of a building for gravity filling, or to transport to another building or packing area.

Simplified process flow diagram of a Spiral Flash Dryer with a Flash Cooler for starch

Starch is a fine powder and ideal for flash cooling. The dried starch is fed straight from the drying line in the cooling duct. This can be seen on the picture on the right where product is collected in the hoppers under the cyclones. Through a rotary valve, the starch drops straight in the ducting of the flash cooler where the cooling air picks up the product and transports it to the next destination.

This flash cooling concept is nicely visible on the picture on the right side.

Ingetecsa's Flash Cooler is ideal for instant cooling and transporting of starch

Ingetecsa's Flash Cooler for instant cooling and transporting of starch

 

Workshop report
Workshop report: “Drying optimisation for the sustainable development of cassava industry”.

 

 

Pregelatinised starch

By modifying the starch, its functionality changes and a new range of opportunities and applications open up. Modification can occur by heat, by chemicals or by enzymes.

If the modification occurs by heat in presence of ample water, followed by drying, a pre-gelatinised starch is formed. Pre-gel starches have a huge range of applications in the food industry, let alone in other industries too. They are highly digestible.

Pre-gelatinisation gives native starches the ability to form a cold water paste. They develop viscosity without the need for heat which means that the food manufacturer does not need to pre-cook the starch. This makes starch an excellent binder to thicken sauces, roux or soups. While this is just only one of the applications.
Pre-gelatinised starches retain most of the functional properties and viscosity of the original base material.

 

Gelling of starch

When starch in presence of sufficient water is heated, its granules will start to swell due to the penetrating water. Further heating to a certain temperature breaks the hydrogen bonding of the starch molecules open. The granule structure disintegrates. This allows the starch molecules to dissolve in the water. The temperature at which the starch granules irreversibly break open, is called the gelanitisation temperature, or pre-gel temperature.

The pre-gel temperature of starch varies upon several factors, such as the plant source, the amount of water present, and the pH. Pre-gel temperatures vary between 58-80°C, although the most commonly used pre-gel starches are more in the 62-70°C range.

 

Drying of the pre-gelatinised starch

After the starch is gelled and has thickened to a viscous slurry, it requires drying.

The drum dryer can be used for this.
The homogeneous slurry of water and starch are pumped to the single drum dryer. On the heated drum, the slurry is heated up to above the gelanitisation temperature. Above the drum surface are several applicator rolls with scraper knives ensuring proper mixing and retention time of the starch mixture. This guarantees an almost 100% gelatinisation degree.

The starch granules swell, the bonding breaks and the starch dissolves in the water. In a matter of seconds, the starch is thermally modified and dried to specification. The starch has become cold soluble and highly digestible.

The dried starch is scraped off the drum as a thin film which only requires milling to specification so it can be easily dosed in its final blend or application.

 

 

Drying of modified pre-gel starch on a drum dryer

Drying of a modified pre-gel starch on a drum dryer

More information can be found at our download centre.
Here you find all brochures with footage, examples, and background details.

If you are interested how we can help you with your starch project, please contact us. Our very experienced process team looks forward to discussing your questions.

 

 

 

Starch drying and cooling expert

We look forward to discussing your questions with you

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