For shrimp feed to have the desired effect, that is to provide optimal energy for maximum growth, it must meet the following characteristics: Shrimp feed pellets must achieve 100% sinkablility and have a water stability greater than 2 hours. Additionally, the starch is used to hold pellets together hold no real nutritional value for shrimp. Therefor a process that allows for starches to be replaced by protein can further support the goal of optimized feed conversion ratio.
When pelleting, grind quality is very important. When oversized or inconsistent particles are incountered in the feed ingredients, pellet durability is adversely affected. While both processes will benefit from the addition of grinders or pulverizers, when choosing the pelleting process for your shrimp feed production, consider the addition of classifiers for the processing of recycling oversized particles.
The pelleting process is highly sensitive to excessive moisture content, high moisture causes rollers to slip and consequently creates machine blockages.Therefore, post conditioning is a necessary in the pelleting line, in order to achieve a suitable level of starch cooking, and to meet the requirement for water stability.
Pelleted feed is a densification process by nature and therefore, coating feed with liquid palatants or wet nutritional ingredients (fats and oils) post pelleting can be a challenge. Another factor that affects pellet quality is control of pellet size and length which poses additional challenges process.
Intensive pre-conditioning is a decisive stage of the extrusion process. To prevent expansion of pellets out of extruder the temperature of meal ingredients must be kept at a precise temperature.
Additionally, because of all the excess moist added during both preconditioning and extrusion, drying is also mandatory so moisture stability can be maintained in the finished pellets. However, post conditioning can be eliminated from the extrusion process all together.
Several benefits of extrusion include precise control over pellet length, a factor that is important in starter feed where pellets should be as small as Ø0,6mm. This process is not possible on a pellet mill without the addition of a crumbler. Additionally control over pellet pourosity means they can be easily coated with palatents and oils.
The extrusion technique also allows for substitution of functional starch with nutritional proteins and the expansion control system ® allows to precisely adjust the pellet expansion obtaining full and complete sinkablity, the two primary factors for production of high quality shrimp feed.
Article made possible through the contribution of Nils Lastein and ANDRITZ