Study On Water Stability And Sinking Of Shrimp Feeds

Water stability and sinking are important processing quality indexes of shrimp feeds and have a direct effect on culture benefit. Processing technology and parameters are the key factors influencing product processing quality. So studying water stability and sinking is scientific and reasonable and necessary from the processing technology.Decreasing material grinding particle size and increasing conditioning time, material moisture content and temperature after conditioning and post-cooking time contribute to increasing starch gelatinization and water stability. When passing through 0.18 mm grading sifter after grinding, conditioning through two or three conditioners, the material moisture content and temperature reaches to 16.5%~18.0% and 80~90℃separately and then the pellets post-cook at 90~100℃for 1 h, water resistant time of the finial product is above 4 h. So it can meet the demand of water stability of shrimp feeds. Surface quality also influences water stability and sinking of shrimp pellet feeds. Surface having cracks, uneven incision and inconsistent length can decrease the water stability; inconsistent length and rough surface can decrease sinking rate.Density is very important in the production of extruded shrimp feeds. Single factor experiment indicates that increasing material moisture content and opening ratio of die orifice can reduce expansion ration and improve density; increasing feed rate, screw speed, barrel temperature of discharging segment can improve expansion ration and reduce density. Orthogonal experiment shows that material moisture content,screw speed and barrel temperature of discharging segment have significant effects on product density (P<0.05). The optimum extrusion process conditions are that material moisture content 26%, feed rate 40 r/min, screw speed 70 r/min, barrel temperature of middle segment 110℃, barrel temperature of discharging segment 50℃. In the extruded shrimp feeds, loss percentage of dry matter has great increase because of rough surface. The feed producers should pay attention to the surface quality and strength production supervision.This research is helpful to improve production quality of shrimp feeds and promote the healthy and sustainable development of shrimp cultivation industry.