Process and equipment for puffing snack food

Puffed snack food is a kind of widely consumed food. This type of food is named for the direct expansion from the extruder die and does not require further processing other than drying. The typical examples of direct puffing snack foods are corn loops, crispy nuts, onion balls, potato chips and recently popular three-dimensional snack foods. 

The extruded product has five processing sections: mixing → transportation → extrusion → drying → coating. 

1, mixing - its role is to mix dry materials and water to achieve pre-wetting effect, to provide some time for starch hydration, this process has a great impact on the final swelling effect. Generally, the total water content of extruded materials is 13-20%, which is completed by the mixer. 

2. Transport - transport the mixed materials from the powder mixer to the hopper. Long use bucket elevator, screw conveyor or vacuum conveying device. 

3, extrusion - this is the key to extrusion extrusion processing. The extruder digests the material and converts it into a plastic melt under a certain pressure. The digested material forms a certain shape through a small die hole under the pressure. The cutting device cuts the continuous discharge into the desired size. The operating device of the extruder can be used to control the density and texture of the direct extruder. Template resistance is also a parameter that can be independently controlled, but it will not change during the stable process after assembly by extruder. 

4, drying - the direct extrusion of food processing after drying. The water content of the extruded raw materials is 13%-16%, which is reduced to 8%-12% after the extrusion due to the evaporation of water into steam, and then the water content is reduced to 2-5% to form the environment needed for crisp texture and stable price life. Due to the low product density, the drying time is very short to achieve the effect. 

5. Paint - the expanded and dried products should be sprayed with oil and flavoring agent. The coating of oil and flavoring agent usually accounts for about 20-35% of the weight of the finished product.