Extrusion technology for the production of micro-aquatic feeds and shrimp feeds


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Nowadays we often hear startling news such as, ‘seven billionth baby born’ or ‘world population may reach 9.2 billion by 2050’ (world news, msnbc.com). Hunger is the world’s number one health risk, it kills more people than AIDS every year, one in seven people in the world will go to bed hungry tonight.

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Extrusion technology for the production of micro-aquatic feeds and shrimp feeds

  1. 1. November | December 2012Extrusion technology for the production of micro-aquatic feeds and shrimp feeds International Aquafeed is published five times a year by Perendale Publishers Ltd of the United Kingdom. All data is published in good faith, based on information received, and while every care is taken to prevent inaccuracies, the publishers accept no liability for any errors or omissions or for the consequences of action taken on the basis of information published. ©Copyright 2012 Perendale Publishers Ltd. All rights reserved. No part of this publication may be reproduced in any form or by any means without prior permission of the copyright owner. Printed by Perendale Publishers Ltd. ISSN: 1464-0058The International magazine for the aquaculture feed industry
  2. 2. FEATURE Extrusion technology for the production of micro-aquatic feeds and shrimp feeds Image courtesy of Wenger Manufacturing, USAby Mian N. Riaz, Ph.D, Head of Extrusion Technology Program,Food Protein R&D Center, Texas A&M University, USAN owadays we often hear startling and commercial-scale feed, which is the key production of micro-aquatic feeds. The raw news such as, ‘seven billionth for growth of aquaculture industry. The fun- recipe is very finely ground or pulverized baby born’ or ‘world population damental components of extrusion systems and does not possess good flow properties. may reach 9.2 billion by 2050’ have consisted of the following items for a The feed system must be able to handle(world news, msnbc.com). Hunger is the number of years: these finely ground formulations and avoidworld’s number one health risk, it kills more 1) Feed delivery system bridging and non-uniform metering of thepeople than AIDS every year, one in seven 2) Preconditioning feed.people in the world will go to bed hungry 3) Extruder Automated feed delivery systems withtonight. 4) Die and knife assemblies PLC control are the norm. Slurry tanks and Although existing extrusion systems were liquid feeding devices (pumps) are utilized to To overcome these issues, farmers must able to produce a wide range of good quality accomplish uniform metering of liquid ingre-produce 70 percent more food by 2050 to aquatic feeds (both floating and sinking), small dients. The slurry tanks are often jacketedfeed the population. But the impending crisis diameter pellet sizes were difficult to produce for heating or cooking and are equipped withis that the earth may run out of food by 2050. at reasonable or cost-effective throughputs. agitators as required. Positive displacement2.4 billion extra people, no more land, how Recent innovations in the basic hardware metering pumps deliver metered liquids atwill we feed the world in 2050? components permit smaller diameter feeds at constant rates by varying length of stroke or At the same time we also hear in the news attractive production throughputs. speed of rotation. Slurries or liquids can bethat global fish consumption has hit a record premixed with dry ingredients but are prefer-high. We have seen the commercial fishing Feed delivery system ably injected into preconditioning devices ortrend is declining whereas aquaculture farming Hoppers or bins are an integral part of the extruder barrel. The nutrient profile ofis growing rapidly all over the world. a feeding device and are used to hold the larval feeds is critical and the precise metering Is this supply enough to feed the future dry ingredients above the feeders. The feed ensures correct formulations.population? May be not, but fish demand delivery system must be able to uniformlyis growing every day all over the world. To feed both a dry and/or liquid ingredient or a Preconditioningmaintain baseline consumption in every coun- blend of ingredients. The dry portion of the feed and thetry, 159 million tons of fish is needed to feed Generally, when the added fat content of a liquid portion are separately introduced intothe world population in 2030. This demand raw formulation exceeds 12 percent, the por- a preconditioning device where they areis driven by population and income growth. tion of fat above the 12 percent level should continuously mixed, heated, and moisturisedIf a country’s aquaculture production follows be introduced into the extrusion system in by the injection of hot water and/or steam.the recent trend, the expected aquaculture a separate ingredient stream. The dry feed The intense mixing of water and steam addedgrowth rate will need a four percent increase portion is delivered to the extrusion system to the dry feed and the ability to extend theannually. To feed a growing world population, through a specialised metering device capable retention time during the preconditioningthe required aquaculture growth rate is 5.6 of providing uniform flow at any desired phase allows the moisture level to be main-percent annually. extrusion rate. tained at an optimum. Some of the main challenges to achieve Dry ingredients are usually free flowing, This ability to maintain optimum moisturethese goals are proper and large-scale feed and there are a number of capable feeding distribution not only initiates proper cookingproduction systems for micro aquatic feed. devices which vary in their relative cost but also is reported as a significant factor inRecently extruder manufacturers came up and complexity. However, gravimetric or the reduction of extruder barrel wear andwith new technologies which can solve some loss-in-weight systems are necessary for the extruder shaft power per ton of productof the aquaculture issues related to large stable, precise metering of dry feed for the processed. The higher mixing intensity of new 20 | InternatIonal AquAFeed | november-December 2012
  3. 3. FEATUREpreconditioner designs improves hydration increase. The mechanism of shear does not desired final product texture, density, color,and cooking, helping to capture the steam in begin to play a dominant role until the screw and functional properties.the raw material. Excess steam can escape flow channel is full. This full flow channel Twin-screw systems are preferred forthe preconditioner and create fugitive dust condition begins in the kneading zone. extrusion of aquatic feeds smaller than 2which creates housekeeping concerns in the The flow channel fills, first, with loose mm diameter due to their positive transportplant environments. granular material which is compressed and and self-wiping characteristics which prevents Better cooking with new precondition- worked by shear as it passes through the significant product build-up in the extruderers gives lower product viscosities which kneading zone. It is in the kneading zone barrel which could later dislodge and plug the Image courtesy of Wenger Manufacturing, USAimproves extrudate flow through small where the discrete particles of material begin small die orifices. The C²TX system is a co-die orifices. The result is smaller pellets to agglomerate because of their temperature rotating system that includes a tapered screwand more uniform pellet size. The higher increase resulting from conduction, direct diameter which de-aerates the extrudate andmixing intensities in new preconditioner steam injection, and viscous energy dissipa- makes it easier to create high density feeds fordesigns is the result of unique beater tion. Here, the discrete particles begin to form good sinking characteristics without the needdesigns and more beater contacts per a more integral flowing dough mass. for vented barrels, pressurized density controlretention time. At the discharge end of the knead-Extrusion ing zone, the extru- Extruders are generally classified as either being date most typicallya single or twin-screw design. In both designs, the reaches its maxi-impact of final product characteristics are affected mum compaction.by screw and barrel profile, screw speed, process- The shear in thising conditions (temperature, moisture, etc.), raw area of the extrudermaterial characteristics, and die/knife selection. barrel is moderate The feeding zone of the extruder is that and the extrudatearea where the low-density discrete particles temperature beginsof raw material are transported into the to increase. Theextruder barrel inlet. This low-density, often final cooking zonepreconditioned, material is then transported is that area whereinto the interior of the extrusion processing amorphousizing andchamber. The flow channel of the screw is texturising occur.typically not filled in this zone due to the Temperature andair entrapped in the incoming material. The pressure typicallyincoming material is compressed slightly in this increase most rap-zone with the air being expelled. idly in this region Water, an excellent plasticizer, is typically as shear rates areinjected into the barrel in the feeding zone highest because ofto facilitate textural development, viscosity the extruder screwdevelopment, and to enhance conductive heat configuration andtransfer. The kneading zone of the cooking maximum compres-extruder continues the compression started sion of the extru-in the feeding zone, and the flow channels of date. The pressure,the extruder screw have a higher degree of fill. temperature, and As the degree of screw fill increases and resulting fluid viscos-pressure begins to develop in the extruder ity are such that thebarrel, leakage flow (flow over the outside extrudate will expeldiameter of the screw in a direction toward from the extruderthe extruder inlet) and pressure flow both die to form the november-December 2012 | InternatIonal AquAFeed | 21
  4. 4. Fatten up your bottom line. Bühler high-performance animal and aqua feed productionsystems are used by leading companies around the world. These producers know theycan rely not just on the technology itself, but also on the support that accompanies it. Aservice combining local presence with global expertise both lowers feed mill operatingcosts and increases capacity utilization. To find out more, visit www.buhlergroup.comBühler AG, Feed & Biomass, CH-9240 Uzwil, Switzerland, T +41 71 955 11 11, F +41 71 955 28 96fu.buz@buhlergroup.com, www.buhlergroup.comInnovations for a better world.
  5. 5. FEATURE which mini- die/knife area. The small diameter feeds mised nutrient results in spillage in this area and will destruction. cause sanitation problems. Floating prod- b) For product separation. Floating feeds ucts are pos- have a tendency to stick together sible by simply when wet on belt or HVH conveyors decreasing die and pneumatic conveying enhances open area. separation. c) For separation of ‘tails’ from pellets. Process Pneumatic systems ‘scrub’ the product guidelines and remove tails for later separation Image courtesy of Wenger Manufacturing, USA Process during sifting. guidelines 7) Fluid bed dryers are recommended required for die for products under 1.2 mm diameter holes smaller in size although horizontal dryers with than 1.2 mm polyester screens can work with some diameter: products. 1) Recipe to 8) Final product sifting after dryer and contain ade- before coating. This sifting operation is quate starch critical for three reasons: levels for bind- a) To remove ‘overs’ (large tails and ing (at least ‘doubles’) for regrind. 25% starch for b) To remove ‘fines’ for regrind. This floating feeds). prevents a mess during coating step devices, or double extrusion. By adding a BPV 2) Maximum particle size of the recipe where the fines are also coated and (Back Pressure Valve) after the extruder, the must be smaller than one third the die cause buildup. necessary restriction is provided to expand hole sizes. c) To separate good pellets into several the product if floating pellets are desired. 3) A spring-loaded knife blade is different diameters depending on the recommended. client criteria for size. The expecta- Die assemblies 4) All mass flow inputs must be free of tions from the industry will be for The die is the most critical part of the material that is large enough to block tight specs on pellet size and this can complete system as it determines prod- or partially block the die openings and easily be controlled at this point by uct shape and size, but also determines this includes the steam, water, fat, and sifting product and producing several throughputs and buoyancy properties of other liquid inputs. The water and steam different sizes at the same time and the final aquatic feed. As pellet diameters lines going to the extruder system need setting the standard for the industry. became smaller, the die created more to be fitted with screen filters having The primary-sized product can be sent restriction and drastically reduced through- 30 mesh (0.6 mm) openings and these on through the system for coating and puts. should be adequate if maintained. The into final product bins. The secondary One die assembly design that allowed fat line (and fat source) also needs to sizes can either be reworked or saved an increase in throughputs by increasing die be filtered to remove debris larger than separately in tote bags for coating and 30 mesh (0.6 mm). All strainers bagging later. or filters must be easy to clean 9) Production procedures. This small diam- or they will get removed ‘in the eter product requires a dedicated line,"This micro-aquatic floating heat of a run’ where liquid flows strict startup and shutdown procedures are interrupted due to plugged to avoid die plugging, and thoroughfeed will be the foundation filters. It may be necessary to cleanup techniques. The extruder andto start fish farming on have a dual filter set up for fish coater areas should be considered as solubles and fat lines. With this ‘wet areas’ for cleaning. The coatercommercial scale to fulfill the installation, if one filter is plugged may need to be cleaned between each you can close the valves to the different pellet size to avoid crossfish demand in the world" primary filter for cleaning and contamination. open the valves for the second By following these guidelines and using for continued operation. newly innovative extruder parts micro-aquatic open area is the OTD (Oblique Tube Die). 5) The dry feed must pass through a vibrat- floating feed can be produced on a large This die actually increased die open area (the ing sifter after the grinder and before scale basis. This micro-aquatic floating feed number of orifices) by two to three times the extruder live bin. This sifter must be will be the foundation to start fish farming on which maintained high throughputs even for sized to remove particles the same size commercial scale to fulfill the fish demand in small diameter products due to larger die hole or larger than the die openings. High the world. populations. The tubes created longer reten- fishmeal diets plug vibrating sifter screens tion times for improved cooking. Pressure very easily and the industry often employs drop in the tubes created a denser product rotary sifters to avoid this bottleneck. so that micro-aquatic feeds could be cooked 6) Pneumatic conveying is required from More InforMatIon: thoroughly but still maintain high densities the extruder die to the dryer inlet for Email: mnriaz@tamu.edu for sinking characteristics. The process was several reasons: still a short time/high temperature process, a) For product containment around the 22 | InternatIonal AquAFeed | november-December 2012
  6. 6. FEATURE Your challenge is our passion. MetAMINO® – The superior methionine source for your aquafeed. www.evonik.com/feed-additives | feed-additives@evonik.com RESOLVING THE BOTTLENECKS IN AQUAFEED through innovation and expertise smart aqua additives for sustainable and cost-efficient aquafeed AQUAGEST® AQUASTIM® Digestibility enhancers Immune-modulators AQUABITE® SANACORE® Attractants and palatability enhancers Natural growth promoters APEX® AQUA NUTRI-BIND AQUA Bio-active herbal extract Low inclusion binders www.nutriad.comNAD0031_AD_Aqua_190x132_W2.indd 1 17-02-12 09:59 november-December 2012 | InternatIonal AquAFeed | 23
  7. 7. This digital re-print is part of the November | December 2012 edition of International LINKSAquafeed magazine. Content from the magazine is available to view free-of-charge, both as a fullonline magazine on our website, and as an archive of individual features onthe docstoc website.Please click here to view our other publications on www.docstoc.com. VO L U M E 1 5 I S S U E 6 2 0 1 2 • See the full issue An overview of the UK fish vaccination industry • Visit the International Aquafeed website Why check selenomethionine levels in selenium yeast? Extrusion technology for the production of micro-aquatic feeds • Contact the International Aquafeed Team and shrimp feeds EXPERT TOPIC – Salmon • Subscribe to International Aquafeed THE INTERNATIONAL MAGAZINE FOR THE AQUACULTURE FEED INDUSTRYIAF12.06.indd 1 07/11/2012 17:39To purchase a paper copy of the magazine, or to subscribe to the paperedition please contact our Circulation and Subscriptions Manager on the linkabove. INFORMATION FOR ADVERTISERS - CLICK HERE www.aquafeed.co.uk