The effect of extruder on the ups and downs of fish feed

The unique function of the extruder is to change the bulk density of the feed to make a floating, sinking or slow sinking fish feed.

In North America, most fish feed is made buoyant. Floating fish feed can not only improve feed efficiency, but most importantly, it allows farmers to see the feeding situation of fish and reduces environmental pollution. The processing of floating fish feed requires the injection of steam and water, and the material should contain 20% starch, which functions as a binding agent and an energy substance. The puffed product should have a temperature of 125～138℃, 34～37 atmospheres (33～36kg/cm2), 25%～27% moisture before being ejected from the mold; after puffing, the bulk density should be 320～400g/L, and the moisture content should be 21%～ twenty four%. This shows that the extruded product will lose 3 to 4 percentage points of water when it is ejected from the mold. Just when the extruded product is out of the mold, the pressure is suddenly released so that the superheated water becomes steam and the moisture of the extruded product is reduced; this also causes a lot of small bubbles, and the extruded feed can float. Usually, the fish feed is further dried (moisture content below 10%), which can also improve floating. The bulk density of 480g/L is regarded as the turning point of the pellet feed floatation. When necessary, fish feed can also be made into sinking feed with an extruder. When making heavy feed, inject water into the modulator (no or less steam), the ring mold should have 26-30 atmospheres (25-29kg/cm2), the extruded product should contain 28%-30% water, and the bulk density after expansion It is 450～550g/L, the temperature is 120℃, and the moisture content is 26%. The wet-curing extruder uses a die with a vent, and the dry extruder uses a secondary extruder die (Rokey and Huber, 1994), which can reduce the temperature, moisture and expansion rate of the extruded product to make a sinking feed. The die with a vent is close to the template, so it can also be used where vitamins, pigments and flavor enhancers need to be added to the puffed product to avoid excessive maturation. The sinking fish feed should contain 10% starch and 12% fat, and the final extruded product contains 10%-12% water. Excessive drying will cause the sinking feed to float.

Soybean meal is commonly used as a source of protein in terrestrial animal feed. The content of anti-trypsin such anti-nutritional factors in soybean meal is only 3.0～3.5mg (antitrypsin unit, TIU)/g, which is very high in raw soybeans. Puffing and maturation reduces the TIU of full-fat soybeans from 46.5mgTIU to 46.5mgTIU. 7.6～8.5mgTIU. Soybean meal is also widely used in warm water fish feed, such as channel catfish, tilapia and carp feed. However, there are reports that cold-water fish such as trout and salmon are more sensitive to soybean meal. Therefore, commercial trout and salmon feed contains a large amount of fish meal, only about 5% to 10% soybean meal. At present, the production of fishmeal in the world is stagnant, and it is necessary to explore the possibility of soybean meal used in trout and salmon feed production. Cheng Zongjia et al. (2003) replaced 0, 25%, 50%, 75% and 100% of fish meal in rainbow trout feed with soybean meal. The fish meal control diet had 32.8% fish meal (herring meal) and 42% crude protein. The nitrogen content is the same as the energy level, and it is cold-formed and expanded. After 4 weeks of testing, there was no significant difference in weight gain and feed efficiency between fish fed with 75% fish meal instead of 75% fish meal and fish fed with fish meal control feed (P>0.05, Table 12). This shows that the content of soybean meal that can be used in trout feed is as high as 24.6%. This experiment illustrates the potential of soybean meal in cold-water fish farming. However, the use of soybean meal and soybean products in aquafeeds clearly requires more research. For example, full-fat soybeans need to be evaluated; methods to feed more soybean meal and soybean oil need to be studied, and soybean oil and soybean lecithin should be used instead of fish oil. , In order to reduce the cholesterol content in trout and shrimp; it is necessary to study the addition of commercial phytase to full-fat soybean and soybean meal to reduce the phytate phosphorus and total in fish and shrimp feed based on full-fat soybean and soybean meal Phosphorus and improve the utilization of minerals.

Shandong Arrow Intelligent Equipment Co., Ltd. twin-screw extruder produces aquatic feed with high protein content and rich nutrients. The product can float on the surface or sink to the bottom, and can also be used to determine the buoyancy and sinking properties of various fish and shrimp. Feed, no waste of feed and supplement of micronutrient elements can promote the rapid growth of aquatic products, making it an ideal choice for all kinds of farmers.