Application Example: Breakfast Cereal Mixing and Extrusion with Coperion K-Tron Smart Weigh Belt Feeders

Mixing of breakfast cereal with dried fruits (e.g. raisins, apple pieces, nuts, banana slices) using traditional or modern methods

Traditional Method:

All ingredients are fed one after the other into a vessel. The total batch is then mixed. A homogenous mixture is difficult to obtain since the ingredients generally have large differences in particle size, shape or density. There is also the risk of destruction of shear sensitive ingredients.

Modern Technology:

Weigh belt feeder in food process features continuous taring

Modern processes mainly use continuously operated feeders. Shear sensitive ingredients are generally conveyed mechanically with belt or vibratory conveyors. Ingredients, which are not shear sensitive, are conveyed pneumatically or mechanically.

If one ingredient is an extruded breakfast cereal (e.g. corn flakes), the mass flow rate is normally measured by a weigh belt meter and the other ingredients are fed in the correct ratio, as defined by the recipe, onto a belt or vibratory conveyor which is installed after the weigh belt meter. If no extruded breakfast cereals are used, all ingredients are fed directly in the correct ratio, as defined by the recipe, onto a belt or vibratory conveyor. The final mixture of ingredients is then conveyed by a belt or vibratory conveyor to the packaging machine.

Features of a modern process:

Simple single stage process, no risk of segregation of ingredients. Smaller feeders are required (because of continuous, simultaneous operation)

  • No destruction of shear sensitive ingredients caused by the process
  • Higher productivity
  • Less space requirement
  • Better and more consistent quality of the final product
  • Lower running costs (energy and labor charges)
  • No intermediate storage required (as between the batch mixing and the sequential continuous packaging process)
  • Less cleaning effort
  • Easier to automate and to control the process

Weigh Belt Feeder: Features of a weigh belt feeder with continuous taring enabled by a second weigh bridge:

  • Dust build-up on weighing device has no effect on accuracy
  • Better short-term accuracy
  • Higher accuracy with low feed rates
  • Higher accuracy if belt load is very thin
  • Higher accuracy with low density bulk solids
  • Higher accuracy with temperature fluctuation
  • Indication for cleaning

Extrusion Application

Cereal or a mixture of cereal is formed in a way to make their shape more attractive and more consumer-friendly.

Traditional Process:

Liquids and dry cereal ingredients (whole grains and grits) are separately weighed and fed into rotary cereal cookers on an automated batch basis. The cereal is gelatinized by passing steam under pressure through the cooker. Since the cereal tends to agglomerate in the cooker, the cooked grains are discharged into lump breakers to break up the cereal.

Food extrusion with feeders, vacuum canveyors and batch mixer

Modern Technology:

Modern processes mainly use continuously operated twin or single screw extruders. They can be used for flaked, shredded, expanded and co-extruded cereal.

Material handling upstream of the extruder can be handled in two ways:

  1. The dry ingredients and additives are conveyed pneumatically or mechanically and are weighed into a batch mixer. This dry premix is conveyed pneumatically or mechanically and fed by a volumetric or gravimetric feeder into an extruder. Liquid additives are pumped into the extruder. A forming and a cutting device is installed at the discharge of the extruder to define the shape of the breakfast cereal.

  2. All components are fed individually with dedicated feeders. Heat sensitive additives (e.g. vitamins, flavorings and spices) are normally not fed into the extruder because of the high product temperatures inside the extruder of more than 120 °C (250 °F). These products are normally added in a coating process after the extrusion and cooling process.

Choice of Procedure
Feeding of dry premixes:

If the dry ingredients and additives have very low differences in particle size, in particle shape or in bulk density, the risk of segregation of dry ingredients and additives is very low. In this case the premix of the dry ingredients and additives can be fed into the extruder.

The feeding of dry premixes has the following benefits:

  • No limitations in the number of dry ingredients and additivesEasier to add new dry ingredients and additives
  • Easier arrangement of many feeders (no space restrictions as at the inlet of an extruder)
  • Less height required above the extruder
  • Less cleaning effort in case of changing dry ingredients and additives
  • Higher productivity in case of a lot of dry ingredients and additives
  • Lower investment costs for a high number of dry ingredients and additives

Separate feeding of all dry ingredients and additives

If the dry ingredients and additives have big differences in particle size, in particle shape or in bulk density, the risk of segregation of dry ingredients and additives is very high. In this case a consistent product quality can only be achieved if similar dry ingredients and additives are classified in groups, which are fed together, or if all dry ingredients and additives are fed separately.

The separate feeding of dry ingredients and additives has the following benefits:

  • No risk of segregation
  • More consistent product quality
  • Smaller feeders required
  • No mixing step required
  • Higher productivity in case of a few dry ingredients and additives
  • Simpler to automate and to control
  • Lower running costs (energy and labor charges)
  • Less space requirement
  • Lower investment costs for a few dry ingredients and additives

Features of a Modern Process:

  • Continuous self-cleaning of the screws of the twin screw extruder
  • Simple, continuous process
  • Less product content
  • Higher throughput rate
  • Shorter mean residence time in extruder
  • Higher productivity
  • Reduced space requirement
  • Less thermal decomposition because of shorter residence time
  • Better and more consistent quality of the final product
  • Lower running costs (energy and labor expense)
  • No intermediate storage required between the batch cooking process and the subsequent continuous process such as coating or packaging
  • Less cleaning effort
  • Easier to automate the process
  • Easier to control the process

Potential New installations

Breakfast cereal has a large growth potential in all countries of the world. The industry is very innovative in designing new products, which leads to new installations.

Retrofits

Retrofits of existing plants to increase the product quality is expected to grow in the next years (e.g. elimination of the mixing step and installation of loss-in-weight feeding devices instead of volumetric feeding devices).

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Typical breakfast cereal mixing process using continuous feeders