09/08/2017: Learning extrusion techniques from the master - Aquatic products and trends

by Joe Kearns, of Wenger Manufacturing, USA 

  

Joe Kearns

International Aquafeed was fortunate to co-host an informative and insightful extrusion seminar given by retiring Wenger extrusion expert, Joe Kearns prior to the WAS 2017 South Africa event in Cape Town from June 26-30, 2017

Listening to the final lecture by Joe Kearns, delivered on behalf of Wenger Manufacturing, it was interesting to pick up on several of the key points he imparted to his audience. In his typical, engaging manner he captivated an audience of just over 60 extrusion process operators at the half-day seminar ‘African Extrusion 2017’, hosted jointly by Wenger Manufacturing and International Aquafeed. The key points he covered, in his own relaxed and informative style although not in any particular order, included: 
 

Making feed
We had worked hard for 25 years on shrimp feed. We can always make the feed hold together in the water and work perfectly, but we could never make the volumes required. Pellet mills could achieve higher capacities per hour.

Our team had to figure out how to make these extruders produce six, seven and even eight tonnes per hour of shrimp feed. We solved the problem by putting two dies on which greatly increased the extruder's capacity. You want to sell feeds eight percent moisture or do you want to sell them at 10-11 percent moisture?

The difference in achieving the correct moisture level may mean you could pay for your whole line in just two years on the savings to be made. Then you do the numbers, you have to figure out the cost of the raw materials, the cost of the product while making a feed that's more even and one that will accept oil evenly; if you have a feed that has varying moisture levels, the one with the most moisture will take up more oil.

We can make some very big pellets. We have some examples of making feed with huge pellets for tuna in Australia that had 50 percent of the formulation as ground-up fish. I was asked in Australia if we could make feed ‘swim’ in water.

“If you could figure out how to do that it would be great. Our tuna don't really like to eat the pellets.”

So we got to thinking that high fish-inclusion works perfectly however, they have to catch pilchards to feed their tuna. They didn't want to give that up. But if we fed them half as much pilchard they could raise twice as much fish couldn't they?

By splitting this up and making a formulation that had vitamins and minerals, syrup rings and proteins they were going to figure out something. Blue-fin tuna are said to have never willfully eaten a commercial feed.

Well we made some pellets and trained these wild-caught tuna to eat a prepared feed. It was slightly warped to be able to make a feed for a fish that really wouldn't normally eat what came out of a process like ours. Using different shapes, the currents that helped to move the pellets around, the shading on the pellet and the sun hitting them, there were splashes and these fish were suddenly learning how to eat prepared diets with added vitamins and minerals that made these fish grow faster than just eating simple, frozen or ground-up fish thrown to them.

So there's a lot to be learned about a lot of species and how they feed that we haven't really studied yet.

Sea urchin feed
Back in the late 1900s we were challenged by Dr John Lawrence, who's famous for his studies of Sea Urchins at the University of South Florida. His brother, Dr Addison Lawrence, was big into shrimp feeds and calls me and says “My brother's got a problem, we need to make some sea urchin feed for him.”

I say I don't know anything about sea urchins, tell me something about your feed and he says, “Well, they're feeding them agar protein material and cutting up little jelly pieces and its not working out.” I said you need something that's moisturised.

So I went and brought four different types semi-moist pepsin strand peas, chuck peas, oat pieces, and set them down and said, “What do you think of these products?” He said, “We could do that,” and so we ended up making what we now call a semi-moist feed for sea urchins.

Obviously, with sea urchins you can see their colour, there's carotenoids in this because we had to be concerned about colour as they were mainly for the Japanese market. We made these feeds at 25-30 percent moisture using propylene glycol, phosphoric acid and potassium sorbate as liquid ingredients to hold the water, to lower pH and achieve a little mould inhibitor.

The fact that these feeds were made with high-end moisture, meant they weren’t soaking water into a pellet that would have happened with nine or 10 percent moisture pellets. The reason for the patent is these feeds can stay in water for five days which is what is wanted in order to feed sea urchins every day – it’s too costly to feed daily so they wanted to go out and feed them once a week.

Then come back a week later and put more feed in, and this actually works pretty well. The interesting thing about it was, we started off making a product like this for sea urchins because they normally ate kelp leaves.

Well, we quickly found out that our shape was better because the sea urchins could store pellets in their spines, where other sea urchins couldn't get it. I actually watched one of them manipulate those pellets around and into a position where it would eat and kept the other ones on top. I would never have figured sea urchins would figure this out so quick, they must have great brains.”

It was amazing just to see animals that hardly move and eat kelp, but you throw extruded pellets at them they know what to do with them immediately. It just so happened that when we did this it became a popular shape for abalone, which we didn't have to add carotenoids as it wasn't so important for colour, but the formulation just happened to be pretty much exactly the same and we sent a lot of this feed to Chile where they were fed in conjunction with seaweed.

I learnt a lot about seaweeds; some promote growth more than others. So, I thought the next time we make abalone feed why not pick the right seaweed instead of using the one that doesn't give such good growth? We did this and achieved extremely good growth with the extruded product in terms of the size of the abalone over a 180-day test period.

Read the full article, HERE.

Visit the Wenger website, HERE.

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