The material is pulverized both in the extruder and pelletizer. However, the process diverges here completely.
In a pelletizing machine, the moist feed admixture is not always cooked with steam and, if done, it is done at normal atmospheric pressure.
The wet mixture is cooked with steam before being extruded out through a screw into a die with a specific shape in the process of extrusion.
The steam creates a high pressure, which allows you to cook the feed at a higher temperature. The cooking temperature rises above 100°C when the pressure is greater than 1 atmosphere.
The hotter the temperature, the more thoroughly the ingredients are cooked. The procedure is comparable to that of cooking meat in a pressure cooker, which makes it more tender in a shorter amount of time than when cooked in an ordinary pot.
The Cost-Benefit Advantage of Extrusion
The main advantage of feed extrusion is the cost-benefit advantage it offers. The technology can be used to create a feed for a variety of animals, including poultry, livestock, and fish.
The feed can be customized to meet the specific needs of each animal, which helps to improve the overall health and productivity of the animal.
In addition, the feed can be fortified with vitamins and minerals to further improve the health of the animal. The extrusion process also creates a more uniform feed pellet that is easier for the animal to digest.
The partially broken bonds of molecules and the presence of anti-nutritional factors from plant materials that limit the availability of several substances, nutrients, vitamins, and minerals means that even if the pelletized feed is subjected to steam throughout processing, it can only be considered half-cooked and has a lower digestion rate.
The extruded feed, on the other hand, is cooked to a higher degree owing to the greater temperature and pressure it is subjected to. This makes it more digestible and more of its nutrients are changed into flesh and tissues. As a result, the FCR (feed conversion ratio) is lower.
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The stability of the feed is another significant benefit of extrusion that can be seen regardless of whether or not you have special equipment. Feed that has only been pelletized is more gritty and produces more "powder" as a result of handling.
These fines are frequently blown away, especially when the wind is blowing strongly, and they are simply wasted, and thus a higher FCR.
Another benefit of the extrusion process is that extruded feeds can be manufactured to float. This is quite significant in fish cages. Extruded feeds result in a lot less waste and all of it goes to the fish.
When not consumed promptly, pelletized diets sink as soon as they become wet, limiting the fish's access to them. They are no longer accessible to the fish once they have sunk.
It's not only a waste of money, but it's also harmful to the environment because they'll rot on the bottom.
Extruded feeds are 30% more accessible than pelleted versions of the same feed, according to research.
Extrusion cooking technology dramatically improves the digestibility and availability of all nutrients in a feed, including fiber, starch, proteins, minerals, and fats, resulting in enhanced absorption.
The extrusion enables considerably more fat to be included in meals. It ensures that substances are delivered to the animals rather than being lost, resulting in decreased feed consumption.
Extruded feeds eliminate almost all dust and fines. The less dust at the bottom of the bag, the more nutrients make it into the fish, less waste, and a lower FCR.
The primary bond that holds the chain of amino acids together is destroyed by the extrusion process.
The heat of extrusion destroys noxious chemicals such as urease and the trypsin inhibitor that might be found in raw soybeans.
By compressing carbohydrates, the extrusion process greatly improves their use.
When starch is extruded, it is gelatinized and swells as a result of this process.
The starch granule is then gelatinized, and it can no longer return to its original form. It is now water-soluble.
During the extrusion process, oil is extracted from soybeans and other raw materials, making fat more accessible for absorption.
The oil aids in the dietary fatty acid supply and improves the feed's energy density.
The high temperature during the extrusion process aids in the eradication of germs in the feed that would otherwise cause decay. Feeds with a longer shelf life are now possible as a result of this.
Extrusion for The Fish Farming Industry
For instance, for the fish farming industry, capital is one of the most significant barriers to entering aquaculture. Many newcomers, who are often inadequately prepared in the sector, believe that they will save money by feeding fish with low-quality pelleted diets.
The cost of producing one kilogram of fish is greater when FCR is higher because pelleted feed usage is increased. Instead of saving, the use of pelletized feeds increases the cost of production.
Extrusion increases digestibility, reduces waste and FCR significantly compared to pelletizer systems.
In addition to that, pelletized feeds have a higher risk of stunting, pollution, and fatalities.
In addition, extruded feeds save money by an average of 18.28 percent and 16.80 percent in milkfish and tilapia, respectively, in intensive cage culture systems.
Extrusion of plant meals enhances their nutritional value, allowing for more efficient and efficient usage. Extrusion provides for more effective and efficient usage of vegetable components, lowering the need for sea fishmeal. Extrusion reduces feed waste and uneaten feeds by 27-33 percent, lowering the risk of pollution in coastal and interior seas.