Application of screw extruder in food industry

Screw extruder is mainly used in the production of starch extruded food, protein extruded food and extruded feed in the food industry, and can also be used as a special chemical or biochemical reactor.
Starch puffed food
The starch in the grain will gelatinize (αize) under the high temperature and pressure of the extruder. The results showed that the degree of starch αization was more than 98% and the crude fat decreased by 60% or even disappeared after the puffed corn flour. Water solubility increased by more than 40%. Therefore, extruder can replace roller dryer to produce gelatinized starch. Gu Zhengbiao et al. used an extruder to deeply process starch and prepared starch phosphate and caramel pigment with starch as raw material. Scholars Carr and Cunningham successfully used a twin-screw extruder to produce glycol glycosides from starch. M euser et al. produced anion and cationic starch from starch derivatives in a twin-screw extruding machine.
Protein extrusion food
Under high temperature and high pressure, plant proteins are organized. Under the action of shear force between the screw groove and the drum wall of the extruder, the vegetable protein was strongly unfolded and relatively presented linear arrangement. The unfolded molecular chains are free to reorient and recombine to form a fibrous state. Its fibrous tissue structure is similar to lean meat, and after rehydration, it has a certain elasticity and a chewable feeling. In addition, fish proteins such as surimi and dried fish meal can be re-organized to produce food that mimics the flavors of prawns, turtle and chicken. Use double screw extruder to grind and chop meat to produce all kinds of engineering meat products. Such as beef jerky, pork jerky and so on.
Expanded feed
In the feed processing technology, extruder is mainly used to deal with full-fat soybean meal, corn starch, various cake meal, rice husk, rice bran, egg shell, fish meal, blood meal and so on. The feed produced has fish like floating feed, high protein shrimp feed, piglet feed, chicken feed, toy animal feed, special aquatic feed and so on.
(1) By extruded full fat soybean, the urease and other anti-nutrition factors in it are inactivated, and the palatability and digestibility of soybean feed are improved, which can be used as the source of protein and energy in the feed of piglets.
(2) Feed starch raw material is mainly corn. Chinese corn starch content (71~72)%, in which amylose accounted for 27%, amylopectin accounted for 73%. The starch content of feed mainly affects the expansibility of feed. Among them, amylose or modified starch content is high, it is easy to expand. If the feed formula contains low starch content or no starch at all, it is difficult to achieve a certain degree of expansion.
(3) All kinds of oil cakes are rich in protein, which is denatured by high temperature and high pressure treatment, destroying anti-nutrient factors and improving the digestibility and utilization rate of energy materials. And these cakes contain a certain amount of toxic ingredients, extrusion method can effectively detoxify.
(4) After the extrusion treatment of rice husk and bran, the storage life can be extended by 10 times, the lipase and oxidase are inactivated, microorganisms and pests are killed, and the fat is not easy to hydrolyze and oxidize, and is relatively stable.
(5) As an unconventional feed resource, crop straw has coarse texture, poor palatability, low digestibility and low nutritional value. However, after cooking and pupping, the nutritional value and digestibility can be improved. It has been reported that plant cell walls are destroyed by cooking at 5×10 ~ 9×10°Pa. After high pressure water vapor treatment, the sudden depressurization destroyed the structure of the fiber and had a good effect on the orange rod.