According to a recent research,aquaculture industry has the highest increasing speed in the world feed industry. Its booming development bring aquatic feed to people’s attention as it plays the significant role in aquatic animals healthy growth. Among the various types of aquaculture feed, it is the extruded feed that win most popularity due to its obvious advantages such as advanced extruding process, palatable flavor,easy digestion and wide application to aquatic animals. The innovative extruded feed processing technology will largely lower down fishermen cost on aquatic animal feeding which accounts for 80% of their cost, thus it can bring them greater profit by way of less investment. We will introduce extruded aquatic feed processing in details.
1. Aquatic Feed Introduction and Classification
Aquatic feed refers to all kinds of aquatic animal feed in seawater and fresh water. The classifications are as follows:
1.1 According to the buoyancy in water, aquatic feed is categorized into sinking feed, floating feed, and slow sinking feed.
1.2 Due to different feeding objects, aquatic feed is classified into fish feed, shrimp feed, frog feed, etc.
1.3 Because of the appearance, aquatic feeds can be divided into powdered feed and granular feed; And based on the different processing technologies, granular feed can be classified into extruded aquatic feed and pressed aquatic feed. Among aquatic feed classification, the powdered feed and granule feed are commonly used in fishery and granule feed is more popular because of its higher dissolve-loss ratio. Although powdered feed is beneficial to food taking and digestion for some animals, it dissolves easily so that brings contamination to water and trouble in cleaning. Thus granule feed is the ideal choice.
2. Aquatic Feed Processing Technology Brief Introduction
Manufacturing aquatic feeds is a little more complex than that of common feed. There are mainly two technologies used in aquatic feed processing: pelletizing and extrusion technology.
Actually, extruded feed technology development is based on pelleted technology, while these two feed processing technologies have their own characters respectively. During the whole aquatic feed production process, they have the similar working flowchart which are grinding and blending, feed producing,drying and cooling. Here are the complete processing flowchart.
–Grinding means to crush grains like corn, wheat and soybean into powder. This process is achieved by feed hammer mills. Feed grinding is beneficial for the mixing operation and can improve the raw materials nutritional utilization. Generally, the smaller, the better.
–Blending is the process of mixing proportioned raw materials tighter to obtain a homogeneous mixture. Additives or micro ingredients are added at this step to increase its stickiness and nutrition. During this blending process, feed screw belt blender or double shaft feed mixer is the most commonly used equipment.
–Feed forming stage. Uniformly blended feed materials are fed into conditioner and pressed on a die with fixed size holes. While extruded feed forming process is in fact the interaction of heat, water and pressure which makes raw material coagulated because of the sudden change of temperature. Heat and water both exist in vapour form to soften protain and starch and bond them together.
–Drying and cooling. Both extruded feed and pelleted feed should go through drying and cooling stages. Feed particles discharged from pellet machine or extruding machine are fragile and humid which are not convient to convey and store. Drying and cooling can lower down the excrescent moisture and increase their strength. If coating is needed, coat feed particles after drying stage because high temperature can help feed absorb animal oil and fat. After cooling, preserve feed particles in dry and ventilated room for use.
2.1 Aquatic Feed Extrusion Technology
The extrusion process of aquatic feed is essentially a cooking process during which the starch-containing components are decomposed and the proteins are denatured. Raw materials are strongly impacted by the high speed rotating shaft and fully cooked by the heating system where the temperature in extruder can reach upto 120-170 C. Finally, when the material is extruded through extrusion die, the pressure is released to normal state suddenly and the pellets are expanded into puffed form. In addition, the density and length of extruded pellets can be adjusted according to customers’ requirements. Extruded feed has various forms: floating feed to sinking feed.
2.1.1 wet extrusion and dry extrusion
We have two types of extrusion methods: wet extrusion and dry extrusion. The exact difference between them is whether there is steam preconditioning in feed processing stage. Wet type extrusion processing needs a boiler to offer steam for the conditioner so as to ripen the raw material in advance. The output of wet aquatic feed is higher than the dry type feed in the case of same power consumption. Dry extruders are used in processing low moisture, highly expanded starch products and dry feed pellets are stable for relatively long periods & convenient for storage. We manufacture extrusion feed machines which can produce both wet and dry aquatic feed.
2.2 Extruded Feed Merits
Increasing the feed utilization rate. Most aquatic animals have relatively simple digestive systems which is such an key point when choosing feed for them. Extrusion technology can improve starch gelatinization degree, and thus makes the extruded feed fragrant and palatable, so the feed taking rate is increasing. At the same time, the protain in vegetable protain feed can be degenerated after heating, while this change will make the protain molecular grow larger and increase the contact with enzyme in animal body and is good to aquatic animal digestion and absorption, which turns out that the nutritional ingredients digestion rate is increased by 10%-35%.
Good to the environment. Extrusion feed is stable in water. The extrusion technology makes starch inside feed materials gelatinization and protain unionization which produces sticky aquatic feed and their stability can reach more than 12 hours(36 hours-the longest stable time), in this case, the nutrition ingredients dissolve or lose amount is decreasing a lot. Data suggests that adopting extruded feed can save you 5%-10% aquatic feed amount compared to powdered feed and pelleted feed. Extrude feed stability reduces water contamination in this way.
Reducing sickness. There are harmful microorganisms in raw feed material such as Aerobic raw material, Neutrophilic bacteria, escherichia coli and salmonella, etc. especially in animal feed materials. While extrusion process creates high temperature, high moisture content and high pressure and can kill most of the harmful organisms. It is revealed that extrusion process can kill escherichia coli from 10000 to less than 10 per gram. The salmonella can be killed completely when temperature is above 85℃.
Convenient to feed. The floating feed can stay at water surface for a long period of time so that there is no need to settle special stands for feeding but feed them at a certain stand. Fish will emerge from water when eating and we can directly watch and adjust feeding amount in time; fish growing and healthy condition can be attended, too. Therefore, extrusion food feeding is a scientific way to raise aquatic animals-saving time&cost and increasing productivity.
Wide application. Extrusion feed has three types which are floating feed, slow-sinking feed and sinking feed. About 80% aquatic animal such as shrimp,salmon, tuna and so on like sinking feed; while catfish, tilapia,eel and most other young fish prefer floating fish feed. What’s more, extrusion feed can satisfy some special requirements like low moisture content feed and high fiber feed which can be produced easily during extrusion. Thus extrusion feed seems a cost-effective choice for fishermen.
No matter how many types of aquatic animal feed in the market, how to choose the better type is exact what we concerns. It is reasonable that you should take into consideration of aquatic feed processing technology, feed nutrition content, aquatic animals, and cost and profit, etc. Maybe extruded aquatic feed is a nice choice for your aquaculture sound development, it totally depends on yourself!
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