Extrusion Cooking Systems for Feed Production. Joe Kearns (Wenger)
Published:March 26, 2012
Joe Kearns, Aquaculture Process Engineering Manager at Wenger Manufacturing, Inc., talks about latest developments Wenger has made regarding Aquaculture Products at Victam 2012.
Can you share some more details on the trials you have performed on the tuna feed production? What was the proximate moisture content in the feeding section before steam and slurry addition and what was calculated moisture content in the barrel (counting the steam and slurry part as well)? Did you use glycerol as the humectant? Was it a semi-moist product (16-18%)? What was the model of the extruder?
"A desirable fish pellet should be durable enough to remain floating and absorb water, but not change its shape (i.e. disintegrate) after being in the water for a couple of hours".
Where is the connection between "durable enough" "remain floating" " absorb water" " not change its shape i.e. disintegrate" after being in water for couple of hours...?
- First: If a pellet absorbs water, it will change shape, i.e. become swollen.
-Second: Durability is the resistance of a pellet to breakage (how much fines are produced) when the pellet is subjected to stress i.e. handling, transport etc..
-Third: Durability is not the main factor determining float-ability. Bulk density of the pellet, oil content, starch source and content and processing parameters during extrusion and more...
Lastly, my question was: What would the binding agent do exactly? Increase the water stability of the pellet, or the durability, or the hardness, or combination?
Thanks
Loses its durability? Do you mean disintegrates completely in water? What would the binding agent do exactly? Increase the water stability of the pellet, or the durability, or the hardness, or combination?
I would like to add a few more comments regarding making sinking vs floating fish feed.
1. Floating or sinking pellets are dependent on the formulation. Both the type of starch and inclusion rate of starch will make a shaped fish feed float. Generally, sinking pellets incorporate less starch and higher fat, with post-fat application likely.
2. Additionally, the type of die plate used will help with expansion (for floating) and gelatinization (binding) of the fish feed. For floating fish feed, a longer land length can assist with more expansion, hence, floating characteristics of the pellet. Alternatively, a shorter land length and more back pressure at the die plate can generate sinking characteristics due to less room for expansion. The type of starch used will affect the amount of gelatinization (or cook) of the fish feed. If a high quality starch is used then the sinking pellets will hold together better. Post-extrusion handling is also important to sort fines (especially with small diameter feeds < 2 mm) that may interfere with the ability of the feed to float vs sink.
3. Extrusion is an adaptable technology for generating shaped products, such as fish feed. Small changes in the formulation of the feed can affect pellet characteristics such as binding, size, shape, and sinking/floating. It is important to work with someone that has experience developing different types of fish feeds to match your application. It is possible to produce aquatic feed with small scale production (about 1 ton per hr), which results in a smaller investment in equipment. This also leaves potential to expand by adding more equipment as the business grows.
To summarize, final desired product will influence what type of extruder (single vs twin screw), scale of production, and types of ingredients you will use in your operation. Feel free to reach out if you have any further questions about the use of extrusion for developing fish feed.
Thank you, Joe Kearns, for starting and continuing the discussion on how extrusion can be used to produce high-quality fish feed.
If you are interested in learning more about the extrusion process and how it can be applied to the aquaculture industry, check out this short course in aquaculture hosted at Texas A&M by PERDC (https://perdc.tamu.edu/event/aquaculture-feed-extrusion-nutrition-and-feed-management-short-course/).
How about I respond to this one also. The answer is yes a functional small version of large well designed extruder can make floating and sinking feeds. The question is not technical but cost effectiveness. Unless the feed is of such a high value the cost of a small proper extruder is not justifiable.
Dear Jayaraj, There are a number of feed ingredients which are important, all selected based on the nutrition of the fish being fed. For floating starch is needed at about 20% to insure floating. Feed ingredients need to be ground to a minimum of 1/3 the die hole size. I would think the finer the better for small fish down to about 200 micron.
Dear Halim,
You are correct, attractants can be beneficial to the first feeding. If the fish are started out when young they will eat the feed more readily throughout their growth cycle.
Myself involved in Asian seabass Aquaculture. As you are well aware that, weaning of fry stage is become challenging in marine finfish particularly Asian Seabass. The stability of feed varies from freshwater, brackishwater and then marine. We prefer to have slow sinking type of extruded feed with high protein composition. Whether cooking process during extrusion for slow sinking type of feed can meet the requirements while rearing in various physical water parameters.
Thanks for educating us on the best way to manufacture floating fish pellets feeds. However, please educate us on some of the best natural binders for the pellets.
Many thanks Joe about the topic !!, Joe Kearns is my friend and he has more than 42 years working with Wenger selling Extruders and Dryers for petfood and aquafeed, so he really can manage this Forum in a technical approach.
Extrusion cooking systems, I will speak in particuar to single screw extrusion as well twin screw extrusion.
Both machines must be fed with a specific formulation regarding the specie you are feeding --in terms its nutritional requirements and the stage in the life cicle of the animal--. (assumming the first stages of the process been: intake, grinding, dosing, mixing and preconditioning, prior to extrusion).
The advantage of extrusion cooking rather that pellet mill´s --another alternative to cook starches--, is that extruders can obtain a much more digestibility of the end products from the animals, thus, obtaining a much better performance in terms of conversion factor, i.e., the amout of feed necesarry to make grow the animal in 1 kilo of meet. Other relevant aspect is the management of the bulk density of the extruded feed (for sinking purpuses in fish feed), and that the extrudate is a very stable structure--out of the extruder-- from a chemical point of view (another advantage for fish feed --salmon, tilapia, sea bass, sea bream, schrimp, etc.)
This way, its possible to desing and formulate specific extrudates for the fish or other animals --at different stages of the life cicle in terms of its nutritional requirements. i.e., fat content, proteins, fibre, energy--, diferent sizes and shapes, and with this scope, feed the animal at the most efficient economical performance. Thus, as the upwardig protein gap related to global expansion of the population, from my mind, aquaculture and the ocean, aquaponics inland aquaculture, offshore aquaculture, is where the focus will be, and a very interesting place to be in, considering that by 2100 the population is going to be 19 billion people and by 2050 11 plus billion people --from my forecast with UN data--
This is the technology that is going to grow at the same exponential rate..Extrusion Feed Plants !!
BIg Hug Joe !!
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