Extrusion had shaped the food process

Extrusion had shaped the food process

Extrusion is one of the most frequently used food manufacturing processes. Its versatility enables its end products to be diversified. Food extrusion was started in 1930 for dry pasta and breakfast cereals production. In 1950, it was also applied to pet food manufacturing.

Over 80 years of development, the application had improved and can process continuous extrusion processing. According to IMARC Group, the global extruded snack food market had a value of $50 billion in 2016. It shows a growth rate of 3% as compared to the past seven years.

It is currently still growing, due to the continuous developments of urbanization and the busy lifestyle of consumers around the world. They will prefer to take a bite when they are hungry or craving food. Furthermore, our youngsters are also contributing to the market for snacks.

An Overview of Extrusion Technology

The food extruder is a short bioreactor that enables the continuous transformation of raw ingredients into a wide range of final products. Extrusion has the advantage that it frequently can process foods in one manufacturing step. It is a widely used technology, producing hundreds of food products, including traditional snacks, breakfast cereals, pet food, ingredients, pasta, texturized vegetable protein, baby food, bread, and more.

Simply described, the extruder is a continuous processing machine consisting of one or two screws (composed of a variety of screw elements) that are mounted on shafts and rotated in a fixed closed housing called a barrel. Single-screw extruders utilize one screw and twin-screw extruders use two intermeshing screws. Both styles of extruders operate similarly, providing transport, compression, mixing, cooking, shearing, heating, cooling, and shaping of raw material final products.

As extrusion was introduced to various industries, it has replaced less efficient technologies such as batch processing and has also allowed the development of new products. The success of extrusion technology in the food industry is mainly due to its ability to continuously manipulate very viscous and complex fluids and powders. The basic processing functions are easily modified within the unit: heat and mass transfer; kneading and mixing; micro-mixing; and chemical reactions, cooking, and texturization.

The Extrusion Process

During extrusion, raw materials are forced to flow under controlled conditions along the length of the extruder barrel and through a shaped opening (called die assembly) at a defined throughput. First, raw materials are common ground to the preferred particle size. Frequently they are passed through a preconditioner in which other ingredients are added and steam may be injected. During extrusion, the product is cooked and mixed by three separate energy sources: mechanical energy (shear caused by the screw elements), thermal energy that comes from the heating system, and self-heating due to the melt viscosity in the barrel. As the rheological behavior of the dough in the barrel greatly affects finished product quality, it is very important to control temperatures and process times to optimize food quality and heat transfer.

Variables that influence the extrusion process can be separated into three main categories:

1) Raw material composition and formulation (viscosity, moisture content, chemical composition);

2) thermomechanical cooking factors, including technology design (screw profile, length/diameter of the machine) and operating conditions (screw speed, temperature profile, water content, dry mix rate, residence time); and

3) die texturization factors (die design, insert shape, opening section).

There are four main categories of extrusion processes: cold, hot, steam-induced, and co-extrusion. Cold extrusion is used to gently mix and shape dough without direct heating or cooking within the extruder. It is used mainly for producing pasta and pet treats. Hot extrusion thermomechanical transforms raw materials through short-time and high-temperature conditions under pressure. This type of extrusion is used mainly to cook raw materials to produce textured food and feed products. Steam-induced expansion defines the melt expansion at the die exit due to water flashing off, leading to highly expanded products. Subsequent processing then determines the textural attributes of extruded products. Examples of products produced using this type of extrusion are expanded snacks and breakfast cereals. Expanded co-extrusion combines steam-induced expansion and filling injection for expanded products with dual textures (usually crispy shell and soft filling).

Extruder manufacturers must offer highly flexible equipment to meet the broad scope of applications. For example, the material that the extrusion die is made from can have a significant effect on the final product properties. Flexible vertical cutting systems are popular with snack manufacturers to realize new product geometries, including cup-shaped snacks and a wide range of 3D shapes. As product development is usually performed on small-sized machines, it is critical to be able to scale up easily from an R&D machine to a production-sized extruder.

Darin is both a supplier and manufacturer of these extruders for our customers. Providing quality and durable food machinery lines, at an attractive price. Our sales consultants are also professionally trained to provide excellent service and useful tips and recommendations for our customers.