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Food extrusion process

Food Extrusion Process

Food extrusion is an established and highly versatile technique for the production of food, feed, nutritional additives and flavors.

The extrusion process allows the mass production of food through a continuous and efficient system. Generally, extruded food products have a high starch content. Some examples include pasta, bread, many breakfast cereals and snacks, confectionery, prepackaged cookie dough, bread sticks, some baby food, whole soy, textured vegetable protein, feeds, croquettes, some beverages and dry and semi-moist pet foods.

food extrusion

Food Extruders

The most commonly used extruders in the food industry include single-screw and twin-screw systems, with twin-screw systems more widely used because of their flexibility. This is valid also for Bausano in food extrusion, both the E-GO single screw extruders and MD twin screw extruders are valid options.

Laboratory extruders are also used for food processing, by mixing soft mixed ingredients through an opening in a perforated plate or die designed to produce the required shape. The food, passing through the Bausano extruder, is cut according to the required size. In general, also with regard to this sector, the Bausano extruder is typically a large rotating screw that fits tightly inside a fixed barrel, at the end of which the mold is located.

It is a system for Bausano, that resemblance the one for plastic Extrusion, that encompasses multiple unit operations such as mixing, kneading, cooking, forming, and cutting all into a single piece of equipment. This results in having a relatively simple process with high efficiency and low cost compared to other processing methods.

Extrusion cooking

Extrusion cooking takes the process to the next level by utilizing the Bausano extruders’ precise temperature control and shear energy which is applied by the rotating screws. When passing through the extruder, the food is actually cooked. Due to the changed physical condition of the food, specific denaturation of proteins can occur as well as the rupture of starches resulting in such complex products as meat analogues. Simultaneously the short and controlled residence time in the extruder restricts unwanted decomposition of vitamins, amino acids and enzymes.

Due to high humidity and high heat, many products during the process swell, changing consistency. The phenomenon is known as the expansion ratio. The extrudate is cut by some blades at the exit of the extruder, which rotate quickly around the openings of the die. The product is then cooled and dried, becoming rigid.

Inside the Bausano extruder cooking takes place where the product, thanks to the pressure generated, produces heat and friction. The process can lead to both denaturation of proteins and gelatinization of starch.

Many food extrusion processes produce high temperatures for a shorter or longer period of time. Important factors affecting the process are:

  • Composition of the extrudate

  • Temperature and humidity of the cylinder

  • Length of the screw and the speed of rotation

  • Shape of the mold

  • Speed of rotation of the blades

These factors are closely monitored to ensure consistency of output.

One of the factors that most influences the success of the extrusion process is the humidity which influences the viscosity of the mixture. Increasing the humidity will reduce the viscosity, torque and temperature of the product and increase the bulk density. This will also reduce the pressure to the mold. Normally, to remedy this problem, food processing takes place at a low or intermediate level of humidity (humidity level below 40%). High humidity extrusion is known as wet extrusion. The main factor in the wet extrusion of high starch content extrusions is the temperature.

Post-extrusion processing operations, such as cutting the extruded products into appropriate sizes, drying the products to the desired moisture, as well as seasoning or coating to provide the desired flavor and taste to the products before they go on to packaging. Along with these major sets of processing, there may be additional steps depending on the type of products being produced and their intended uses. So, in conclusion, the food extrusion process in many cases is similar to the plastic one, for this reason Bausano extruders are suitable for food extrusion.

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