Low cost Medium Shear Extruder for pet food and aquafeed

^{_{This article was originally published in Aquafeed (2013), Vol. 5, No.3, 41-45.}}

The single screw extruder has been the heartbeat of dry pet food and aquatic feed for over 50 years. Today, the single screw extruder still is the choice for manufacturing dry expanded pet food as opposed to baked or pelleted feed.

Over 70% of global pet food is being manufactured by six companies. The United States supplies over 40% of the estimated 20 million tons of pet food manufactured. This high volume demand requires high capacity extruders. The majority of manufactured dry pet food is being produced by single screw, twin screw extruders or expanders. For this reason, the strategy of extruder and expander manufacturers has been to offer high capacity equipment. In the pet food industry, there has been interest from veterinarian, kennel owners and small feed manufacturers to customize their own feed through either toll milling or by establishing their own processing facilities. Finding a dependable, high quality, small to medium capacity extruder that requires relatively low capital investment has been a challenge.

The steady growth of aquaculture and the demand for more feed, especially for tilapia and catfish sparked the interest of small producers to investigate the possibility of processing their own feed rather than purchasing complete fish feed. Again, the challenge has been to find a reliable source for an affordable small to medium capacity extruder to fill their needs.

In the past, some of our customers ventured into manufacturing of pet food and aquatic feed utilizing their Insta-Pro® High Shear Extruder. They managed to produce quality products from a nutritional standpoint but, controlling the shape and consistency were some of the challenges.

As Insta-Pro pioneered and developed the High Shear Extrusion technology of processing soybeans in the 1960s in response to the market need for an affordable and practical soy processing method, Again, in 2009, it found itself in the same situation, this time regarding the market demand for development of a small and affordable extruder for the production of shaped products.

With frequent requests and demand for small scale, dependable and cost effective extrusion systems that can produce fish feed and pet food, Insta-Pro was convinced that there is a void in the market for those small and medium enterprises. Being responsive to our customers needs and upon studying the market, a decision was made to respond to the demand with the development of the MS 3000 Medium Shear Extruder which would fill the market void.

The Insta-Pro MS 3000 Medium Shear Extruder was developed with the following objectives:

Production of high quality shaped products from the nutritional aspect, functionality and uniformity of the pellet.
Depending on the size of the pellet, formulation and other factors, a capacity range of 1000-1500 kilograms per hour should be achieved.
Reduction in need of drying to achieve energy saving and maintaining the highest possible nutritional quality.
The flexibility to use local ingredients as an alternative to conventional ingredients
Sourcing a small scale grinding and pulverizing equipment to match the anticipated capacity of extruded product.
Provide a conversion kit for existing customers that are interested in pursuing the Medium Shear option for manufacturing shaped products.
Provide all the above with an affordable cost. Along with the tests done in our R & D facility, the prototype MS 3000 Medium Shear Extruder is being tested in the field for continuous run. A commercial aquatic feed manufacturer in Nigeria was provided a Medium Shear barrel kit and has achieved tremendous improvement with the uniformity, shape and size control of the fish feed pellets while retaining the nutritional quality of the pellet.

R & D results

The smallest pellet size that has successfully produced with the formula tested was about 2.5mm through a 2mm die diameter for floating fish feed, however, we were successful in producing shrimp feed (sinking pellets) of 2mm. The production rate we achieved ranged from 900 -1500 Kilogram per hour based on the size of the pellets. Using sifted formula and 1 mm die openings, we were able to achieve floating fish pellets of an average diameter of 1.4 mm.

Achieving the desired shape, uniformity and the needed capacity of extruded pet food has to be accompanied with optimal cook of the feed.

Since dry pet food contains up to 50% starch from grains, the degree of cook has to be high enough to prevent digestive problems. As for the aquatic feed, the starch gelatinization is also important for the cohesiveness of the pellet and the required buoyancy along with water stability.

Low cost Medium Shear Extruder for pet food and aquafeed - Image 1

Figure 1. Pet Food by Medium Shear extrusion

Low cost Medium Shear Extruder for pet food and aquafeed - Image 2

Figure 2. Four samples on left are different size medium shear pellets for floating fish feed.

The starch gelatinization and degree of cook was performed on dog food produced by the MS 3000 Medium Shear Extruder. Two sizes of typical dog food nuggets produced by the Medium Shear Extruder (MSDF 13mm and MSDF 6.5 mm) (Figure 1) were compared with a premium commercial dog food as a control along with pet food produced with the Insta-Pro High Shear extrusion. The results are reported in Figure 4. The degree of cook through the preconditioner was also reported.

As for the fish feed, the Medium Shear extruded catfish food of pellet sizes of 2.5, 3.5 and 4.5 mm were tested (Figure 2). The results are reported in Figure 5.

As mentioned above, it is also of interest for our customers and prospects to know we were able to produce shrimp feed with pellet diameter of 2 mm. (Figure 3).

The pellet size will be affected by the formulation of concern, the fat or oil content, extrusion temperature, starch content and other factors.

Low cost Medium Shear Extruder for pet food and aquafeed - Image 3

Figure 3. 2mm shrimp feed pellets


Figure 4. Percent cook of Medium Shear pet food		Figure 5. Percent cook of floating fish feed

As mentioned earlier, a commercial operation in Lagos, Nigeria has been running our Medium Shear extruder for over a month now with remarkable improvement in the pellet uniformity, functionality and performance.

All catfish pellets achieved 100% floatability and were stable in water for over 12 hours.