Extrusion of fish feed

This looks like cold extrusion in the old days and there will be limited cook to the dough and you have to heat it up by means of mechanical energy input and creating friction in the extruder. Its aquestion of time, temperature, water content and shear . With 30% of water you have sufficient water to gelatinize. The question is do you have sufficient temperature and time in the extruder; only a matter of secons in order to gealtinize the starches. it would be intresting to know what gelatinization degrea of your starches you will get and the SME specific mechanical energy input you have in your extruder. Normal fish feed extrusion is around 30 kWh/t. Without steam you save the steam yes but you need a lot of energy for drying the additional water afterwards and you will have higher SME requierments in the extruder resulting in higher wear of the screws and barrels.

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As I understand from the comments of Mr. Lu you have a Zheng Chang extruder. He mentioned that screws are different for sinking and floating. This is most likeley only the case for this machine. Normal twin shaft extruders you do not need to change the screw or even screw patterns for sinking and floating products. This is one of the advantages of twin shaft extruders. Due to the forced transportation you an adjust sections in your extruder and as I mentioned after the inlet you would have your cooking section with a number of reversed elements in order to get the desired SME input. There you cook your starches. The next section you have to lower the filling degrea by means of long pitch screws and you have an evacuation port where you can aerate yiur barrel and have one of the most efficient devices to cool down the dough before forming at the die. This control can be done online with modern extruders and you adjust the bulk density accordingly by changing the degrea of aeration or in the maximum case by means of vacuum. Extruder issues should be documented well with all parameters necessary to make a decision which parameters to change. This can be done in a simple table wher you note all the parameters from the extruder (cap. water addition, rpm, torque, temperatures and pressure at the die plus a sketch of your screw configuration and die design, product type and diameter and quality assesment of the product after the extruder.

How can I use single screw extruder for fish feed to make pet food I need the parameters of heat / water / steam cooking time

Dear all, Extruder is energy intensive machine we can save energy for sinking feed by using pelletizer, however extruder are used for making floatable feed. Now meeting all ends possible such as optimum processing, nutritional and feed safety and cost balance and also easy access and availability of raw ingredients is very complex task. But we need a machine that is versatile one and can solve the process problem. In this regard can anyone suggest the floatability to achieve by using pelletizer please. thanks and with regards, P P AMBALKAR

Did anyone use thermal twin extrusion?I would like to talk about it!

Dear Mr.Prakash With palletizer you have a lot of dislikes .You have high risk of bacteria, the food is not cook good and it is only for sinking with extrusion you have enormous possibility BR Denis Dimovski

Dear Sir, Mr. Denis i agree that there would be poor cooking in comparison to extruder but we can dry the product in mechanical dryer and may also ensure reduction in protein quality loss as in pelletizer the temperature does not exceed beyond 80 degree centigrade while in extruder it will reach 130-40 degree because of increased length of barrel.. PP AMBALKAR

Extruders should have been the best but can't be affordable by most medium feed mill industry due to the cost. As mentioned by Mr. Prakash P Ambalkar, I will be grateful if the member can discuss on how to use pelletizer in formulation feeds in place of extruder. I still believed that if food stuffs are well cooked and well dried under high temperature, it will make almost the quality floating feeds as fish feed extruder at a very cheap and more easy way. This will go a long way to reduce the cost of feeding livestock and encourage more farmers (especially in developing countries) to produce more quality feeds instead of highly cost imported feeds as a result of very high foreign exchange rate. Thank you.

Dear Dennis, Upon my experience, I think single screw extruder is easier to operate and control the quality of finished products. Here is YouTube video of one of the single screw extruder: https://www.youtube.com/watch?v=YImp6e9m73g for your reference only! regards.

Dear all, It appears from the conversation, there is no more confusion in the context of extruded pellets and dry pellets. Without mentioning reputed names, can check out few papers just few years back, dry pellets cited as the extruded pellets in standard scientific journals. Numerous research to replace moist pellets/trash fish with extruded pellets have been carried out. However, many of them were not exactly extruded just dried pellets. As we all know, extrusion process is intended not only to provide the feed buoyancy but also digestibility, pellet ability and so on. As a result, EP has got demand in bottom feeders as well. Agreeing with the high cost involved in EP systems. Without distracting and dragging further, I would like to recommend Engineer Prakash, to the best of my experience, play around with binders in yours feed formation, it affects the pelletability to certain extant, as a result feeds sinking rates. Best Wishes

Please wonder why in Egypt the pelletmills are being replaced by many extruders in the recent years.

Dear all! Thanks for discussion. I am trying to evolve an opinion an idea. I may be different here but adding to further discussion I admit that Extruder is a better machine no doubt for better quality feed production, but it is a complex machine and also cost of feed production goes up by around 50 % than that of pelletizer. Moreover alongwith aquaculture pelletizer can also be used for livestock and poultry feeding. For intensive aquaculture quality of pelleted feed can also be improved by effective mechanical drying. I think in my opinion We need to focus on improved and more versatile pelleting machine for manufacturing cost effective fish feed which would serve both purpose (sinking as well as floating feed production). I may be contradictory here but it is recommended and need of the hour. PRAKASH P AMBALKAR

We produce small quantities of pelletted feed for reserach experiments in our station and one thing we have been doing successfully over the years is to simply use very hot (nearly boiling) water for the initial dough formation in the mixer before we run it through the pelletizer. While the gelatinization is admittedly not complete, this simple step promotes better binding. I am sure an arrangement can be rigged to wet the feed and inject steam in to the hopper for production on a bigger scale accomplishing essentially the same thing. I hope this is of some use.

If you look at the performance of pelleted versus extruded fish feed in farming you will see the benefit of extruded feed. Take the example Myanmar: traditional feed FCR 1:4.5; pelleted feed FCR1:2,5 (0,3 USD/kg); Extruded feed 1:1,5 (0.48 USD/kg) If you start calculating costs and results you will see the benefit of extruded feed and besides the benefits of reduced waste into ponds, water quality, controlled feeding, etc. The fact is that pelleted feed due to the process of pelleting will always sink and gelatinization of starches used as a binder are very limited and in the range of 30-35% max (amylase method). Due to the limitation in water used in pelleting gelatinization is limited. With 17 to 18% of water in a pelleting process good gelatinization is just not possible. There is not sufficient shear in this process to get better result. Single shaft extruders have improved in price performance ratio and are simple to use especially for floating feeds, oild addition is much more easy in comparison to pelleted feed. The clear worldwide trend is pelletmills are replaced by extruders and fish feed is made in dedicated fish feed plants due to cross contamination and hygenic issues, except shrimp feeds there pelleting is still the standard process in many areas.

Dear All! There is tremendous scope for engineering intervention to improve the performance of pelletability with respect to improved FCR in pelletizer . It is more a re-searchable issue can be tried with various feed formulations. Process and machine parameters can also be tried for cost effective and more efficient output from pelletizer. The technology of pelleting need to further evaluate with various permutation and combinations for maximum return. PRAKASH P.AMBALKAR

It is interesting reviewing this line of discussion. Pellet mills can easily make a feed sink in water while it is difficult if not impossible to make a pelleted feed float. Not enough water in the process or temperature and pressure development between behind the die and post die to get expansion. You will go broke trying. Extruders as pointed out by Urs above are designed to cook and expand starches contained in the cereal grains used. Die designs are so different and the open area per tone used results in pressures where expansion can occur. When using a extruder to make sinking feeds as also outlined by Urs, you arrange the machine to do both so as you only have a die change and running conditions to make a sinking feed. Floating and sinking can be made on both single screw and twin screw extruders. There are differences and it is considered very important to use a twin when small diameter pellets are made. Also the additional difference in making sinking feeds by pellet mills and extrudes is the extruder offers the possibilities to make a feed that preforms very well with a lower cost formulation. How?, less starch is needed in extrusion to make a sinking feed then a pellet mill offering the space for lower cost proteins and still be able to achieve the desire final protein content. Thermal twin screw extruders are designed to cook with steam not mechanical energy. Designed for high levels of fresh meat type or other liquid ingredients.

Gentlemen; With a lot of appreciation I can see how well known manufacturers such as Anderson International (represent by us R&D Equipment), Buhler, Insta-Pro, Andritz, Wenger and others participate on this kind of discussions, this is the type of feedback and information we need to create and share on this Community; with surprise I can see how the Spanish Community can have 200+ participations on a theme like this and in less than one week here we went from 5 to 40 participations, this is what the people want to read from us. Colleagues, let's keep the communication and participation open. Happy Holidays! Enrique Diaz.