Pelleting and extrusion in aquafeed technology


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Aquaculture is a developing activity around the world. As the industry grows, so does the aquafeed market. Aquafeeds are comprised of a number of ingredients that are mixed in various proportions to complement one another to form a nutritionally complete compound diet. According to the physical characteristics, they can be divided into powder, particle, pelleted and extrusion aquafeed. They can also be divided into sinking, slow sinking and floating aquafeed according to their buoyancy. On the basis of aquafeed energy, they can be divided into low energy, medium energy and high-energy aquafeeds.

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Pelleting and extrusion in aquafeed technology

  1. 1. May | June 2013Pelleting and extrusion in aquafeedtechnologyThe International magazine for the aquaculture feed industryInternational Aquafeed is published six 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 ofinformation published.©Copyright 2013 Perendale Publishers Ltd.All rights reserved.No part of this publication may be reproduced in any formor by any means without prior permission of the copyright owner. Printed by Perendale Publishers Ltd. ISSN: 1464-0058INCORPORATINGf ish farming technolog y
  2. 2. Pelleting and extrusionin aquafeed technologyby Doris Du, sales representative, Allance Machinery, ChinaAquaculture is a developing activity around the world. As the industry grows, so does the aquafeed market. Aquafeeds are comprised of a number of ingredients that are mixed in various proportions to complement one another to form a nutritionally complete compound diet. According to the physical characteristics, they can be divided into powder, particle, pelleted and extrusion aquafeed. They can also be divided into sinking, slow sinking and floating aquafeed according to their buoyancy. On the basis of aquafeed energy, they can be divided into low energy, medium energy and high-energy aquafeeds. Raw materials foraquafeed productionCommon basic raw materials to the manufacture of most aquafeeds are similar to those employed in the manufacture of other types of animal feeds. However, it should be noted that aquafeeds should avoid the use of high levels of plant or veg-etable fibres and carbohydrates which are poorly digested and transformed by fish. Raw materials for aqua-feeds include cereals (maize, wheat, barley, rice, oat etc.), cereal by-products (wheat flour, corn bran, wheat bran etc.), meat meal, fishmeal, shrimp meal, squid meal, blood meal, poultry by-product meal, (full fat) soybean meal, other vegetable protein meals, fats and oils, vitamin and mineral premix, salt, stabilizers and binders etc. The major components of aquafeeds are protein (plant protein, animal protein and single cell protein), starch (sinking aquafeed consists more than 10% and floating aquafeed consists more than 20%), crude fat, raw fibre, crude ash and micronutrients. Starch has great gelatinization under high temperature and high humidity conditions. It can improve the stability of aquafeeds and extrusion density of extruded aquafeeds. Aquafeed processing technologyThe manufacture of aquafeeds is more complex than common feed manufacture. Hardness, size, buoyancy, durability and water stability must all be taken into account. Aquafeed processing technology is not unique. It relies on the development made in conventional animal feed process-ing technology, but with some specific applications. The main processing tech-nology for aquafeeds is pelleting (mainly produce sinking aquafeeds) and extrusion (can produce sinking or floating extruded aquafeeds).Aquafeed pelleting technology is stricter than common animal pelleted feed. Typically, sinking aquafeeds are mostly made with feed pellet mills. Pelleting is still the predominate method for sinking feed production. The aquafeed pelleting processes is described below:GrindingIt is a particle size reduction process for raw materials by hammer mills. Grinding is benefi-cial for the mixing operation and can improve the nutritional utilization of raw materials. For aquafeed processing, an ultra fine feed hammer mill is necessary.MixingThe ground materials must be mixed with the proportioned raw materials to obtain a Table 1: Classification of aquafeeds based upon the energy levels and processing technologylow energy Medium energy High energyProtein (%) 30-40 43-52 40-48Fat (%) 6-13 12-25 22-35Processing machine aquafeed pellet mill extruder/aquafeed pellet mill extrudertarget species salmon, trout seabass, turbot carp, tilapia34 | InternatIonal AquAFeed | May-June 2013FEATURE
  3. 3. homogeneous mixture. During the mixing process, feed ribbon blender or double pad-dle feed mixer is the most commonly used equipment.PelletingPelleting can be defined as the agglomeration of small particles into a larger solid with a given shape and texture, by means of a mechanical process in combination with moisture, heat and pressure. The main factors which affect pelleting are ingredients characteristics, mois-turizing or steaming before pelleting, die thick-ness and binders etc. The ring die aquatic feed pellet mill is the professional pelleting machine for aquafeed processing.CoolingThe temperature of the aquafeed pellets squeezed out the pellet mill is high. They should be cooled before other operations. A counterflow pellet cooler is a high-efficiency cooling machine. CoatingCoating can improve upgrade the aquafeed quality. The physical property of the feed is improved. The fat sprayed on the aquafeed pellets has certain permeability; it can perme-ate into the pellets in subsequent crafts and transport process. That can reduce the scatter of feed particles and dust. The fat spraying machine is also known as feed pellet coating machine.CrumblingIt is a necessary process in aquafeed pellet processing as some fish need smaller pellets. The roll type crumbler can break the aqua-feed pellets into smaller particles.ScreeningIn order to improve aquafeed quality, fines from cooled aquafeed pellets should be removed and the pellet size should be uni-form. Rotary feed pellet grading sieve is just the machine.Aquafeed extrusion technologyA significant application of the extrusion process is in the production of aquafeeds. Extrusion has won some popularity and is widely accepted. Compared to the pellet-ing method, extrusion can be defined as a technological process, namely, forcing feed raw material in one or more of the following process conditions (such as mixing, heating, cutting etc.) flow through the die, make mate-rial forming or eruption gasification. Extrusion allows buoyancy control to make floating, sinking or slow sinking feed by changing the May-June 2013 | InternatIonal AquAFeed | 35FEATURETable 2: Starch contents of common energy feed raw materialsraw materialStarch content(dry matter)raw materialStarch content(dry matter)Whole maize 70-75% Sorghum 71.6%Flour 75-80% Whole rice 81%Wheat bran 5-8% Whole barley 60%Winter wheat 65.5-82% Whole oat 45%Wheat middling 21.5% Soybean meal (44%) 0.5%EXTRUDEREXPANDERAlmex b.v., Verlengde Ooyerhoekseweg 29, 7207 BJ Zutphen, The Netherlands, tel. +31 (0)575 572666, e-mail, www.almex.nlHigh capacity extrudersand expanders.EXTRUDEREXPANDER AD System
  4. 4. extrusion condition including temperature, pressure, die aperture diameter and shear rate etc. Dry or wet extrusionDifferent shapes and sizes of aquatic feed can be produced using extrusion technology. Extrusion with steam precon-ditioning is known as wet extrusion and extrusion without steam preconditioning is called dry extrusion. Dry extruders were used in processing low moisture, highly expanded starch products and in processing whole soybeans to full-fat soy flour for both the food and feed industries.Preconditioning is a very important part of the wet extrusion process for steam or water injection into either the conditioner and/or the extruder barrel. The most important aspect of the precon-ditioning system is the potential for additional mixing and the retention time, which is neces-sary for chemical or physical reactions to take place. The Allance aquafeed extruder for example, can produce dry and wet aquafeeds. Dry feed pellets are stable for relatively long periods, for convenient storage and distribu-tion. The wet type process-ing needs a boiler to make steam to the conditioner and ripen the raw material in advance. Twin-screw extrusionis ideal for aquafeedAccording to the opera-tion methods, extrusion equipment generally falls into two categories: single-screw extruders and twin-screw extruders. Producing small pellet aquafeed by single-screw extruders directly has many advantages, such as low ingredient cost, less fine generat-ed, good water stability and pleasant appear-ance. Twin-screw extruders were first used in the 1950s for manufacturing thermoplastics. They were developed on the basis of single-screw extrusion machine, with a double screw installed side by side in the barrel. A fully meshed co-rotating (both screws turn same direction) extruder greatly improved material conveying, pumping and mixing characteristics. Compared to a single-screw extruder, a TSE has a much wider operating range in terms of use of moisture, internal fat, mechanical energy input and product size. The domestic high quality twin-screw extruder has reached an advanced level in technical performance and manufacturing level with high property price ratio and is the best choice of the aquatic feed processing industry.The main advantages of twin extruder described as follows:• Twin-screw process mandatory delivery and self-cleaning feature, making the material stay in the barrel for a short time and uniformity• As two screws knead and rub each other, extruder enables material mixed and rip-ened more fully in lower energy consump-tion. The whole ripening degree can reach more than 95 percent, water stability last for 24 hours• The biggest characteristics is that it can mix all kinds of raw materials regardless of its formation. This will also enable fish farmers use a wider range of ingredientsConclusionThe production of aquafeed is the fast-est growing sector in the global feed industry. Although a large amount of aquatic feed is still produced by conventional pelleting technol-ogy, extrusion is being utilized to a larger extent because it has several advantages over pelleting. So, pelleting or extrusion? It’s according to various factors that discussed above.Table 3: extruded aquafeeds versus pelleted aquafeedsextruded feed Pelleted feedBonding degree strong strongFloating and sinking beneficial just sinkingStability in water better goodFines in aquafeeds fewer fewnutriment digestibility higher lowerFunding bigger smallerProcessing cost higher lowerequipment wear slower quicker36 | InternatIonal AquAFeed | May-June 2013FEATUREMore InforMatIon:Website:
  5. 5. www.oj-hojtryk.dkDie and roll re-working machinesO&J Højtryk A/SØrnevej 1, DK-6705Esbjerg ØCVR.: 73 66 86 11Phone: +45 75 14 22 55Fax: +45 82 28 91 41mail: info@oj-hojtryk.dkO&J HØJTRYK A/S endeavours to be a powerful, vigorousand energetic company. With our customers needs and theimmediate environment as our point of departure, we wantto be a trendsetter in our core area of business - MechanicalEngineering - Re-working of Dies and Rollers for themanufacture of Feedstuffs and Biopellets, as well as the saleand delivery of wearing parts in connectionwith Roller Re-working - as well as toremain open to new initiatives andbusiness opportunities.O&J HØJTRYK A/S has drawn up astrategy plan setting out guidelines forhow we as an organisation must conductand develop ourselves in order to makeour mark, not just in the present, but also in thefuture.O&J HØJTRYK A/S must achieve success by adaptingto the conditions of the market more quicklyand efficiently than our competitors. As a serviceorganisation we must, in relation to our customers,attach great importance to our own vitality and efficiencyby constantly living up to the ever-growing demands made onthe services we provide.
  6. 6.• See the full issue• Visit the International Aquafeed website• Contact the International Aquafeed Team• Subscribe to International AquafeedThey are what they eatEnhancing the nutritional value of live feedswith microalgaeControlling mycotoxins withbindersUltravioletwater disinfection for fishfarms and hatcheriesNiacin– one of the key B vitamins for sustaininghealthy fish growth and productionVolume 16 Issue 3 2013 - mAY | Ju NeINCORPORATINGfIsh fARmING TeChNOlOGyThis digital re-print is part of the May | June 2013 edition of InternationalAquafeed 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 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