The processing requirements of extruded materials are more complicated than those of granular materials. The main differences are in the processes of conditioning, puffing and liquid spraying:
(1) Conditioning and tempering: In the process of tempering, water and steam are added together to produce the puffed material, and the moisture content after tempering is about 25%, while for the production of pellets, only steam is added, and the moisture content is low after tempering. is about 17%.
(2) Puffing and liquid spraying: There is no puffing process and liquid external spraying process in the production of pellets, but an additional granulation process. The raw materials required by the puffing material processing technology are pulverized more finely, and the high-temperature puffing process can improve the degree of starch ripening, which is conducive to the digestion and absorption of feed by fish.
(3) Advantages of puffing materials: puffing materials require the raw materials to be pulverized more finely, and the high temperature in the processing process not only improves the degree of starch ripening, but also the instant strong rubbing of high temperature, high humidity and heat during the puffing process can kill some harmful bacteria in the raw materials Therefore, compared with ordinary pellets, extruded feed can improve the digestibility and utilization rate of feed and reduce the incidence of disease.
On the other hand, the extruded material has a stability of 12-36 hours in water, which is convenient to visually check the feeding situation of the fish and reduce water pollution.
Comparison chart of extruded material and granular material.
With the enhancement of the concept of environmental protection and green and healthy farming, pellets will be gradually replaced by extruded materials. Compared with powder and pellets, although the extruded feed is more expensive, the feed conversion rate is higher, the comprehensive benefit is better, and the pollution to the water area is less. In recent years, farmers' acceptance of extruded feed has gradually increased. .
How to further improve and improve the level of feed processing technology to produce aquafeed with good stability, strong palatability and higher feed conversion rate is still the future development goal and direction of the aquafeed industry.