Pelletized snacks are produced when the raw material is extruded into a recognizable shape, this can be done using a process known as direct expansion or alternatively using a process known as indirect expansion.

by Tudor Vintiloiu

The direct expanded pellets are produced in a one step extruder and are ready for consumption following the extrusion process.

The indirect expanded pellets are extruded and then generally sold on as a semi-manufactured product to companies who finish the process by frying them in hot oil then dosing them with flavoring or seasoning before packaging.

According to John Eshelman, director of Pretzel and Snack Machinery Sales, Reading Bakery Systems, extruding systems are classified by their pressure rating: High, medium and low-pressure systems.

High-pressure systems, also known as cooking extruders, operate in the 2,800 psi range. These systems typically process course grit ingredients such as corn meal/grits and other added ingredients such as dehydrated potato products resulting in highly expanded snack products. Medium-pressure systems operate in the 1,200 psi range and are capable of extruding dense low-moisture dough without cooking inherent to the high-pressure extrusion process. Low-pressure systems operate in the 150 psi range with the main objective being not to change the physical characteristics and properties of the dough during the low-pressure extrusion process.

“RBS low-pressure extruders offer extrusion widths from 380mm to 2000mm to accommodate the nominal widths of customer’s tunnel ovens and frying equipment. As customer requirements for efficiency, food safety and employee safety have increased, RBS continues to update our designs. The Low Pressure Extruder was recently redesigned to be safer, more efficient and easier to clean. The features of the redesigned LP Extruder include augers that deliver more product flow with less work to the product; new lightweight, seamless, single-piece hoppers that eliminate harborage areas; pre-feed rolls made of plastics that are safe for food processing; an improved cutting mechanism with a longer service life; improved guarding for increased safety; and a band-cutter cam that is positioned away from the product zone to reduce contamination and provide easier maintenance access,” Eshelman explains.

GEA is another leading equipment manufacturer that has recently rounded out its xTru Twin series of high-capacity extruders with the flagship xTru Twin 140. The new top-of-the-range machine is equipped with an advanced profile; powered screws provide users up to 40% increased capacity with the same efficiency, quality and footprint as previous models. Additionally, this high-capacity technology can be applied to the other models of the GEA xTru Twin extruders too – models 70/92/112 – and retrofitted to older machines to increase their capacity without changing the floorplan of the factory.You can read the rest of this article in your complimentary e-copy of the July/August Issue of Potato Processing International magazine, which you can access by clicking here.