FAO Corporate Document Repository 4. PROCESSING 4.1 Technological Processes The main objective of canning is to obtain a shelf-stable product that can be stored in suitablecontainersforaconsiderablelengthoftime(atleasttwoyears)without undergoing food spoilage, while retaining desirable nutritional and sensory qualities. To achieve satisfactory shelf-life the following conditions must be observed:i.The contents of the cans must be commercially sterilized.ii.Theinsideofthecanmustberesistanttoanddamagingeffectsfromthe contentsandtheoutsidemustberesistanttocorrosionunderreasonable storage conditions.iii.The can ends must be sealed to prevent ingress of water and/or air or any form of contamination.4.2 Processing Operations 4.2.1 General Fish should be chill stored at a temperature between 0 and 2 C, or sorted frozen in freezers at temperatures below -28 C. When frozen fish is used, it must be thawed before grading and/or dressing. In the following descriptions of the processing stages for various products, operations which are similar are described in Chapter 4.2.2 "Description of canning tuna in brine", and subsequently only mentioned. 4.2.2 Description of canning tuna in brine Thedescriptionisrelatedtocanningplantwithacapacityof20tonswholerawfish (bluefin or yellowfin tuna) per 8 hours. The overall yield is approximately 50-55% which gives approximately 10 000 450 g (1 pound) cans or 20 000 225 g (1/2 pound) cans per 8 hours. See Figure 4 "Layout for tuna cannery". Simplified flow sheets for canning tuna in brine, tuna flakes with vegetables and tuna. pet food are shown in Figures 5, 6 and 7 respectively.Sequential processing operations for canning tuna are described as follows:a.Frozen tuna is thawed, preferably, by means of running water at a temperature of 10-15 C. Loss during thawing is 0.5-1.0%.Holding of frozen tuna for long periods before thawing may lead to oxidation of fat resulting in a yellow to orange discolouration on the surface of the cooked loins.Usuallythissurfacediscolourationcanberemovedwhenthefishis cleaned.Fish Canning Process1FAO Corporate Document Repository Figure 4 Layout for tuna cannery Fish Canning Process2FAO Corporate Document Repository Figure 5 Flow sheet for canning tuna in brine Fish Canning Process3FAO Corporate Document Repository Figure 6 Flow sheet for tuna flakes with vegetables Fish Canning Process4FAO Corporate Document Repository Figure 7 Flow sheet for tuna pet food b. Longitudinalcutsarecommonwithlargesizedtunaandthevisceraare removed from the fish on board fishing vessels prior to freezing. Bonito and skip jack are frozen with viscera. Once thawed, the tuna is washed and inspected for spoilage. If tuna is not eviscerated on board vessels this must be done in the plant. The splitting and evisceration procedure is the only butchering operation performedonthetunawhileitisintherawcondition.Allothercleaningis performed after the tuna has been cooked. Loss of weight is approximately 24-27%. The tuna is given a pre-cook by heating at a temperature in range of 102 to 104 C. This operation is necessary to make it possible to hand pick the light meat from the carcass and also to remove some of the oil from oily fish.The fish is placed in baskets which are placed on racks. The racks of butchered fish are rolled into the cookers which are usually of rectangular cross section and made of reinforced steel plate with a door, or doors, at one or both ends. The pre-cooking is a batch type operation. Steam is admitted through a steam spreader on the floor of the cooker. Steam ventanddrainvalvesareprovidedtopermitremovalofairandcondensate. Pre-cooking may also be carried out in boiling brine. Fish Canning Process5FAO Corporate Document Repository The pre-cooking time for individual batches varies widely according to the size of tuna. For example, the cooking time may vary from 1 1/2 hours for small tuna to 8 to 10 hours, or more, for larger tuna. Loss of weight is approximately 22-26%.d.Tuna is cooled thoroughly to firm the flesh before the manual cleaning operation can be performed. Loss of weight is approximately 3-5%.e.After the pre-cooking and cooling operations, tuna is individually cleaned. The head is removed and the fish is skinned and split into halves before removing the tail and backbone. The loins are produced by splitting the halves of the fish along the median line. Red meat is then removed from each loin; the blood and dark meat are scraped away and the loins, edible flakes and waste products are separated; of these portions approximately 15% is flake tuna.f.Theproductionofsolidpackswasformerlyahand-packingoperation,butis now carried out by machines. This machine produces a cylinder of tuna loins of uniform density from which can be cut can-zised segments of uniform weight.Chunk packs are produced from loins which are cut on a moving belt by means of reciprocating cutter blades. The cut loins are then filled into cans by tuna filler machines. Flakes and grated tuna, which is produced from broken loins and flakes, are Jpacked in the same way as chunk packs.g.The open cans next pass the line where additives such as salt, vegetables and finally either water or oil are added. Oil should be added slowly over a sufficient stretch of the line to permit its thorough absorbtion by the tuna meat. When oil is not added an equivalent amount of water replaces it. The oil temperature is recommended to be 80 C-90 C.h.Small cans may be closed, without a vacuum, and processed directly, whereas larger ones must be vacuum sealed.As the pressure in the can increases considerably during heat processing , the vacuum is necessary to minimize the pressure increase in order to reduce the chance of distortion (peaking) and damage to the double seam. After processing and cooling the formation of .the vacuum causes the ends of the can to assume a concave profile which is characteristic of vacuum packed andhermeticallysealedcans.Thevacuumalsoreducestheresidualoxygen content in the can and therefore the extent of internal corrosion. In order to form a vacuum, cans are seamed by using either vacuum seamers or an exhaust system. Whenusingtheexhaustingmethodthelidsofthecansarefirstclippedor clinched on to the body in such a way as to allow free passage of gases and vapoursoutofthecan.Thecanandcontentsarethenheatedbypassage through an exhaust box. The lid is seamed to the can immediately it emerges fromtheexhaustbox,sothatwhenthecontentscoolavacuumisobtained. Fish Canning Process6FAO Corporate Document Repository Thusthesystemreliesonsealingthecanwhilethecontentsarehotand allowing product contraction to create the vacuum. An alternate method of achieving a vacuum in sealed cans is by using vacuum seamers. These machines close the cans and while so doing draw the air out thus creating a vacuum.i.The double seaming method is usually used to seal metal containers. The seam is created in two operations. See Figure 8. "Seaming Operation -Double Seam (CAC/RCP 10-1976) .The can, with the lid (can end) placed or clinched on top, stands on a base plate which is raised so that a chuck fits into the countersink part of the lid, holding both in position.The can end which is lined with a plastisol sealing compound is crimped intoplacesothatitformstheso-called"cover-hook"aroundthelipof the container body. The "cover-hook" and the enclosed lip of the container are folded down against the container and interlock about the "body-hook". Both hooks overlap to form a strong joint which acts as a hermetic seal.The sealing compound renders the seam air tight (hermetic). Around its circumference the double seam consists of five layers of metal -three layers of the can end and two layers of the can body, however at the intersection with the side seam there are seven layers of plate, the extra two being due to side seam overlap. Theseamingoperationmustbemonitoredthroughouttheprocessingandvisual inspections should be carried out at least every 30 minutes (Warne, 1993). Good manufacturing practice indicates that the. overlap should be at least 45 % of the internal seam lenght to ensure that the seam will function correctly and resist to minor abuse. Figure 8 Seaming operation -double seam Fish Canning Process7FAO Corporate Document Repository j.Thesealedcansaretransferredbyaconveyorthroughacanwasherwhich cleansthecansindetergentandwaterbeforedischargingthemintoretort baskets.Theretortbasketsaretransferredintotheretortandthecans sterilized.Table 7 Examples of retorting temperatures and times for canned tuna Nominal capacityof cans Alternative Processing temp.(C) conditions time (min) I1162301.8 kg (4 pound) II121190 I11695450 g {l pound) II12180 I11675225 g (l/2 pound ) II12145 I11665112 g (l/4 pound) II12140 All canned fish products are sterilized at temperatures above 100 C. Sterilization takes place in retorts, with or without water. Overpressure is between 2-3 kg/cm. Processing conditions shown are suitable for those canneries , operating under conditions of good manufacturingpractice.Individualcanneriesmayselectdifferentprocessingtimes and/or temperatures to suit their manufacturing requirements. The simplest and most common retorts today are horizontal, or vertical, batch retorts. The following general description. applies to processing in batch retorts using saturated steam as the heating medium. After the retort is loaded the door or lid is closed and the seal is checked to confirm that all the lugs are fastened securely. The temperature recorder is checked to ensure that it is working correctly. Following this the vents and bleeders are opened and the drain and overflow are closed {unless the over flow is used for venting). The retort is now ready for operation during which the following operational procedures should be adopted:Steamisadmittedbygraduallyopeningthecontrollerandthesteamby pass lines.Whenthecorrectventingtemperatureisreached(>100C)and/orthe specified, vent time has elapsed, the vents are closed. It is bad practice to ventlessthantherecommendedtime;norshouldreliancebeplacedon agreement between the mercury thermometer and pressure gauge readings as a criterion for complete air elimination, as this is not necessarily a true indicationoftherequiredcondition.Ifthepressuregaugeisreadinghigh whilethetemperatureisreadinglow,thereisstillairintheretortand venting should be continued until agreement between pressure reading and the corresponding retort temperature is reached.Fish Canning Process8FAO Corporate Document Repository Graduallyclosethebypassastheretortapproachestheprocessing temperature. This will prevent a sudden drop in temperature as the steam supply is cut when the retorting temperature is reached.Whentheretorthasreachedtheprocessingtemperature,checkthe temperature indicated on the mercury and recording thermometers. While it is not serious if the thermograph indicates a temperature slightly lower (say 1 C) than the mercury thermometer, it is most important that it never reads higher.Atalltimesthemercurythermometershouldbeusedasthe reference, for indicating true retort temperature.At the start of the process, record on the production records the time, the mercury thermometer reading, the pressure, and the temperature indicated by the recording thermometer.Keep a record of the come-up time to make certain it has been long enough to . allow sufficient venting.Maintaintheretorttemperatureattherecommendedprocessing temperature.Throughouttheprocess,checkthatthespecifiedtemperatureisbeing maintained.Leave all bleeders wide open during the entire process.Whentherecommendedprocessingtimehaselapsed,turnoffthesteam and immediately start the cooling cycle.k.Whenprocessingmediumsizedorlargercans(saygreaterthan250g)in retorts using steam it may be necessary to cool the cans under pressure so that theendsdonotpeakduringcooling.Steammaybeusedtomaintainthe pressure but compressed air is more usual. The cooling time depends on the processing temperature, the temperature of the water used for cooling, the can size and the nature of the pack (i.e., liquid to solid ratio).l.Ifnecessarythecansshouldbewashedbeforetemporarystorage,however under no conditions should the processed cans be manually handled while wet.4.2.3Descriptionoftheprocessingoperationsofanautomatic canning line for skipjack The descriptions are related to a plant with a capacity of 10 tons whole fish per 8 hours. The overall yield is 50-55% and approximately 9 000-10 000 450 g (1 pound) cans are produced per 8 hours. See Figure 9 "Layout por skipjack cannery". The weight of the fish to be processed is approximately 2 to 5 kg per fish.a.From the chill room the whole fresh skipjack is brought to a bulk elevator which transportsthefishtoaguttingmachinewhichconsistsofasemi-automatic machineinwhichthefishisplacedwithitsbellyupermost.Arotatingknife opens the fish and removes the viscera.Fish Canning Process9FAO Corporate Document Repository Thefishisconveyedtoarotatingnylonbrushunderwhichitiscleanedby water spray nozzles. Aftereviscerationthetunaisconveyedtoaninspectiontablewherethefinal cleaning is completedmanually;orwherethosefish,toolargeforthegutting machine, can be butchered. At the discharge of the gutting machine the offal is directed to a rotating filter drum for separations of water; the retained offal, is pneumatically pumped to containers. Figure 9 Layout for skipjack cannery Fish Canning Process10FAO Corporate Document Repository b.Inspectors examine the fish, while it passes on the conveyor, to ensure that is has been satisfactorily cleaned.c.Fishareautomaticallysize-gradedtoassistinfeedtotherotorcookerand regulation of cooking time.d.Rotory cookers are frequently built with counter flow and discharge belts, and a capacity of approximately 1.3 tons per hour with variable cooking times of up to 2 hours.The cooker is divided into 16 cells into which the fish is fed. The bottom of the cookerisseparatedbyaheavymeshplate,andunderthisareplacedheat exchangers for indirect steam heating. After cooking the fish are transported on a continuous belt to the counter-flow cooler (a stainless vessel with freshwater supply) and then on to the cleaning stations.e.Typical cleaning arrangements consist of:One working table for cleaning the tuna after coolingOne rotating table fitted with holders/cups for loinsOnedischargeelevatorfortransportationofloinportionsfromthe rotating table to the packing machineOne offal conveyor monted beneath the cleaning station to collect and " discharge offal.The operations are as follows:The1stoperatorremovesthefishfromtheconveyorandtransfersittoa working. table where the skin and the head are removed.The2ndoperatoropensthefish,removesthebackboneanddividesthefish into4loins.Simultaneouslythemajorityofdarkmeatisremovedandsingle loins are placed in the cups on the rotating table.The 3rd and 4th operators clean the loins, removing the remaining dark meat. Thecleanedloinsarethenremovedautomaticallyfromtheircupstoa rubberbelt conveyor which transports them to an overlying conveyor.f.The loins then pass to an automatic scale for continuous weighing which makes itpossibletomonitorproductionyields.AfterweighingtheloinspasstoanI accumulationstationpriortopassingtoapack-shaperwhichpackstheloins into cans.Thefilledcanspasstoanoil/brinefillingmachinebeforethevacuumseaming machine. Description of the subsequent operations and their effects on yield are similar to those described for canning tuna in brine. Fish Canning Process11FAO Corporate Document Repository 4.2.4 Description of canning sardines in oil The method for canning sardines in oil is often called the raw packaging method which contrasts with the method in which the sardines are thermally treated before packing into cans. The processing plant related to the description has a capacity of 15 tons raw fish per 8 hours. The overall yields is approximately 50% of the weight of raw fish. See Figure 10 "Layout for sardines in oil, cannery" which shows a plant of this capacity. Figure 10 Layout for sardines in oil cannery Fish Canning Process12FAO Corporate Document Repository One ton of raw sardines is required to produce 5 200 (5 263) 1/4 club cans, packed into 52 cases of 100 cans each or 5 800 (5 882) 1/4 dingley cans packed into 58 cases of 100 cans each. Figure 11 shows "Flow sheet for canning sardines in oil". The operations after the thawing of the frozen fish or after transporting the fresh fish from the chill store are as follows:1.The sardines are size-graded by an automatic grading machine which selects sardines to suit the size of cans used in the plant.Thenumberofsardinespercanpermittedforvariouscantypesisgivenin Table 8 Table 8. Number of sardines per can permitted* for various can types Number of sardines Type of can MinimumMaximum 1/4 dingley 1 layer6 sardines12 sardines 1/86 sardines12 sardines 1/16 oblong 2 layers8 sardines14 sardines 1/4 club 1 layer4 sardines8 sardines * Permitted by ?The smallest size of sardines allowed for canning (in Norway) is 9.5 cm.2.After grading, the sardines are discharged onto a conveyor for transportation to the nobbing machine where the head and guts of the fish are removed. On a typical nobbing machine, the fish are placed on continuous belts with one fish in eachcompartment.Thebeltfeedsthefishtoacuttingwheelwhichcutsthe head,andtogetherwiththeguts, drawsitawayfromthebodywithrollers.If necessary the tails are cut in the same operation.Thepackersexaminethefishtoensurecompleteremovalofguts.Lossofweight during nobbing is approximately 21%. Nowadaystherearealsonobbingmachineswithgreatercapacity,servedbyfouror more operators, which can complete following operations:Removal of the headEviscerationRemoval of the tailWashing the fishPacking the fish into cansThe automatic nobbing/packing machine has a capacity of 35-80 cans per minute and requiresapproximately50%ofthemanpowerrequiredbyatraditionalcanningline (Perovic, 1983). Fish Canning Process13FAO Corporate Document Repository Figure 11 Flow sheet for canning sardines in oil 3.Afternobbingthesardinespassthroughawashingprocesstoremoveblood andsurfaceslime.Washingmachinesofmanytypesmaybeused.Washing should be with potable water or sea water of similar quality. (For certain species withhardandinediblescales,suchaspilchard,specialwashingmachines suitable for removing scales are used).4.The sardines are then transported, usually by a conveyor, to a brining machine. The brining can either be a batch or a continuous operation. The speed of the processandtheconcentrationofthebrinecanbecontrolled.Thefishare loaded into the brining unit in one end where they are immersed in concentrated salt solution, and then screwed through the unit and simultaneously brined. The fish are then discharged at the opposite end of the unit.Salt is absorbed by the flesh; a salt content of about 1-2% of fish weight, when in boxes is acceptable. The brining machine is equipped with a filter to screen particles from the brine. Inadditiontogivingtheproductthedesiredsaltcontent,brininghasother beneficialeffects.Theprocessbrightenstheappearanceofthefishby Fish Canning Process14FAO Corporate Document Repository removing remaining slime and also toughens the skin; when unbrined fish are canned much of the skin adheres to the can.Afterbrining,thefishareallowedtodrainbeforebeingtransportedtothe packing table. The brine must be prepared from salt which does not contain large quantities of magnesium chloride, a common contaminant in unrefined salt. The brine should be replaced regularly as otherwise it becomes a source of contamination.5.Afterthebriningprocessthesardinesarepacked(manuallyorautomatically) into pre-washed cans.A manually operated packing line is equipped with conveyor belts, the speed of which can be altered in order to ensure a smooth supply of sardines and cans to the packers. The filled cans and waste are removed by the conveyor after packing. In common sardine lines the filled cans pass over a weight control unit to a can alignerandthentoacanpusher,whichautomaticallyfeedstheconveyor transferring them to the pre-cooker. Changeofyieldduringthepackingprocessdependsonthequalityofraw material, but on average 5% loss of weight is expected.6.Atypicalflashcookerforsardinesconsistsof2sections,oneforcooking(in steam at about 95 C) and one for drying (in hot air at about 130 C). The cans withtheopenendupwardsareautomaticallytransferredtocrates,whichare hangingoncrossbarsmountedonacontinuouschainconveyorrunningin slingsupawardsintothecookingsection,andintoslingsdownwardsinthe drying section.Between the two sections water is drained from cans as the crates are turned through360aroundatumbler.Theheatinthecookingsectionisobtained fromsupplyofdirectsteamwhiletheheatinthedryingsectionisindirectly suppliedfromaheatexchanger.Afanlocatedonthetopofthesection circulates the heated air. Weight loss during this operation is approximately 25 %.7.From the cooker the cans are automatically transferred onto a conveyor which takes then to the oil dispenser and onto the seaming machine where they are sealed.8.Before the retorting process the cans are washed to remove fish residues and oil from the outside of the containers.9.Further operations as for canning tuna in brine. See chapter 4.2.2.

Fish Canning Process15FAO Corporate Document Repository Table9Examplesofretortingtemperatures and time for canning sardinesCan typeTemp. (C) Retorting time (min)1/4 club115-11655 1/4 dingley115-11665 4.2.5Descriptionofcanningpre-smokedsardinesintomatosauce or oil Mostoftheoperationsinthisprocessaresimilartothosedescribedforcanning sardines in oil. The description is related to a plant capacity of 5 tons of raw fish per 8 hours. The yield from canning of sardines and other pre-smoked small fishes approximate the yields obtained when canning sardines in oil. See Figure 12 "Flow sheet for canning pre-smoked small fish in tomato sauce and oil", and Figure 13 "Layout for pre-smoked small fish cannery" which shows a plant of the capacity mentioned above. The various operations are described below.1.Grading is similar to the operation described for canine sardines in oil.2.Brining is similar to the operation described for canning sardines in oil.3.The fish are rodded, i.e, hung on rods through the eyes. This operation can be done automatically or manually.The automatic rodding being a complicated process is only practised in large plants. The rodded fish are placed into frames which are fitted to the smoking racks. The frames have usually accommodate for 30 rods, each with 30 fish.4.The fish are smoked for approximately 1 hour at temperatures up to l30 C. The mainpurposesofthesmokingistoenhanceflavourandtolowerthewater content of the fish.Usuallytunneltypesmokingkilnsareusedinwhichthereisacontrolled temperature gradient between 30 and 125-130C. Theairpassesthroughaheatexchangerwhilesmokeadded.Thesmokeis producedbyasmokegeneratorusingsawdustfromhardwoods(oakor similar). Loss during smoking is approximately 25%.5.Aftersmokingthebodiesofthefishareseparatedfromtheheadswithan automatic cutting machine. The heads are then removed from the rods with an automatic rod stripping machine. Loss of weight during the deheading operation is approximately 10-12%.Fish Canning Process16FAO Corporate Document Repository 6.The packing, the filling of sauce or oil and the double seaming operations are similar to those described for canning sardines in oil.When preparing tomato sauce, puree of good quality must be used and to this is added olive oil or fish oil, etc. Typicalmixturescompriseonepartoilandtwopartstomatopuree(20% concentration).7.All subsequent operations are similar to those described for canning sardines in oil.4.2.6 Description of canning fish paste products The description is related to a fish paste canning plant with a capacity of l0 tons whole raw fish per 8 hours. The production is based on either deheaded, gutted fish with an average weight of 1.5 kg or smaller industrial fish. See Figure 14 "Layout for fish paste products cannery" which shows a plant of the capacity mentioned above. Overallyieldwhenmanufacturingcannedfishpasteproductsdependsonspecies involved, however, approximately 45-65% of raw fish weight could be used for planning purposes. The output from a plant producing meat balls is approximately 25 000/850 ml cans per 8 hours; alternatively 8 000/850 ml cans of fish cakes or 15 000/850 ml cans of meat balls could be produced. The flow sheet for canning fish paste products is shown in Figure 15. The various processing operations are summarised as follows. The raw material has to go through a grinding/chopping and mincing process.1.The fish are washed, descaled when necessary, eviscerated and deheaded.2.According to skin thickness and size, the fish will have to be split into halves from head to tail along the backbone.3.The split and opened fish are washed and cleaned.4.The washed split fish is separated in a meat-bone separator. According to the typeoffishonewillgetanacceptablemincedproduct,andoffal,bonesand skin.5.If the mince is unacceptable, (i.e. ,discoloured because of blood etc. ), it may be necessary to have it washed and then dewatered by means of a screwpress6.The minced fish is mixed in a bowl chopper or mincer with the other ingredients. itisimportanttoaddthesaltfirstandtoallowthemincertoworkforafew minutes before adding the remaining ingredients to the mixture.This will improve the binding properties of the fish. See Figure 16 "Processing line for fish meat". Fish Canning Process17FAO Corporate Document Repository Figure 12 Flow sheet for canning pre-smoked small fish in tomato sauce and oil Fish Canning Process18FAO Corporate Document Repository Figure 13 Layout for pre-smoked small fish cannery. Fish Canning Process19FAO Corporate Document Repository Figure 14 Layout for fish paste products cannery. Fish Canning Process20FAO Corporate Document Repository Figure 15 Flow sheet for canning fish paste product. Figure 16 Processing line for fish meat Fish Canning Process21FAO Corporate Document Repository Figure 17 Layout for salmon cannery Fish Canning Process22FAO Corporate Document Repository 7.Starch, spices and, if necessary, onions, fat, etc., are added.8.Liquid milk is added and according to the type of mincer, it will take 10-12 min for the materials to reach a soft and formable conditions.9.Thefishballscanbeformedinmachines,byhandwithspoon,orbyhands only, and dropped into a 1 1/2% solutions of salt water at approximately 90 C.10. Aftercookinginthesaltsolutionforapproximately5-8minthefishballsare filled into cans.11. Hot brine or fish bouillon is added.12. After seaming the product goes immediately to retorting.Several alternatives for retorting temperatures and times are shown in Table 10. Table 10 Examples of retorting temperatures and times for canned fish paste products PreheatingHeating Alternative Initial product temp. (C) temp. (C) time (min) temp. (C) time (min) Fish meat balls in brine/ bouillon I201052012015850 ml (99 x 119 mm) cansII201052011540 I201082012013 425 ml (99 x 63 mm) cans II201082011535 Fish cakes in brine/ bouillon 850 ml (99 x 119 mm) cansI301003012025 450 ml (99 x 63 mm), cansI301003012020 Further descriptions are as for canning tuna in brine. 4.2.7 Description of canning salmon The description is related to a processing plant with a capacity of 8 tons of raw fish per 8 hours; this capacity has been based on using whole fish weighing 4 kg each. See Figure 17 "layout for salmon cannery". The overall yield when canning salmon is between 55 to 60 %, depending on the size ofthefish.Withayieldof55%,1tonofrawsalmonwillgive3400(3 437) 225 g (1/2 pound) cans. The processing operations are described below. See Figure 18 "Flow sheet for canning salmon"1.The fish are transported to a sorting table and sorted by species.Fish Canning Process23FAO Corporate Document Repository 2.Thesalmonareevisceratedwithanironchinkmachinewhichremovesthe head, fins and viscera from the salmon (see Figure 19). The loss of weight is approximately 35-40 %3.The eviscerated, deheaded fish is next conveyed to the sliming table. Sliming consists of removing fins, viscera and blood, etc. not removed by the buchering machine. During the sliming operation the fish is throughly washed. The loss of weight is approximately 3-5 %. Figure 18. Flow sheet for canning salmon. 4.From the sliming table the cleaned fish is conveyed to a fish cutter fitted with revolving sknifes which cut the fish into slices. The slices are then .fed into an automatic filling machine. The loss of weight is approximately 0.5-1.0 %.5.The filling machine fills the cans with the salmon after which salt is added.Fish Canning Process24FAO Corporate Document Repository 6.The filled cans pass through an automatic scale which sorts for under Weight cans.7.From the scale the cans pass into a vacuum seaming machine.8.Thefilledandsealedcansarethendischargedfromtheseamingmachine through a can washer.9.After seaming the product goes immediately to retorting. Retorting conditions of approximately 115 C for 100 min are used for 450 ml cans.10. Further descriptions are as for canning tuna in brine.4.2.8 Description of canning shrimps Headless,peeledshrimpsaregradedaccordingtonumberofshrimpsper100gof drained product. See Table 11 (Codex Stan 37-1981). 1. Header Knife 2. Fish In Position For Heading 3. Bull Ring Which Carries Fish Through The Machine 4. Back Pincers 5. Tail Pincers Advanced And Grasping Fish 6. Tail Cua Off Saw 7. Belly Finning Knife 8. Back Pincers Advanced And Grasping Fish 9. Back Finning Knife 10. Belly Slitting Saw 11. Guide To Open Belly Flaps For Gutting Reel 12. Gutting Reel To Remove Vicera 13. Knife And Reel To Slit Kidney Membrane And To Remove Kidney 14. Brush To Remove Blood And Membranes 15. Roller To Support Bull Ring 16. Fish Released As Back And Tail Pincers Retract 17. Conveyor To Remove Butchered Fish Figure 19 Iron chink for dressing salmon Fish Canning Process25FAO Corporate Document Repository Figure 20 Layout for shrimp cannery Fish Canning Process26FAO Corporate Document Repository Table 11 Number of shrimp per 100 g of drained product Size DesignationConventionalCleaned Extra large or jumboless than 12.3less than 13.4 Large12.3 to 17.7 inclusive19.4 to 19.1 inclusive Mediummorethan19.1butnotmore than 31.8 morethan19.1butnotmore than 34.6 Smallmorethan31.8butnotmore than 60 morethan34.6butnotmore than 65.3 Tiny or minuscularmore than 60.0more than 65.3 It is usual to can only those shrimp which fall in the medium to very small size range. The description is based on a processing plant capacity of 3.6 tons raw shrimp per 8 hours.Thiscorrespondstoproductionof12000-14000cans,eachcontaining75g shrimp, in 8 hours. The overall yield from canning shrimp is between 25 to 30% of raw weight. See Figure 20 "Layout for shrimp cannery " which shows a plant of the capacity mentioned above. The description is based on using iced raw shrimp as the raw material. The shrimps areusuallygradedbeforedeliverytothecannery.SeeFigure21"Flowsheetfor canning shrimps" . The operations in the canning process are summarized below:a.On arrival at the cannery, ice is removed before washing the shrimps.b.The shrimps are throughly washed while being conveyed into the plant.c.After washing the shrimps are inspected and foreign debris removed.d.Theshrimpsarethenconveyedtoapeelingmachine,whichseparatesthe shellsandheadsfromthebody.Thisoperationcanalsobedonemanually. Aproximately 46% of the total weight is lost during this process.e.After peeling, the shrimps pass through to a waste separator, which removes fragments left after peeling.f.Thecleanedshrimpsareloadedintobasketsandplacedintoaboilingsalt solution for cooking. Average salt concentration in the solution is 11-13%. The cooking time varies from 6-10 minutes depending on the size of the shrimps.g.After cooking the shrimps are inspected and any broken ones and/or pieces are removed. The shrimps are then dried by fans.h.The shrimps are weighed and hand-filled into cans. The weight of the shrimps . should be 64% of the content of the can. Aluminium cans are preferably used forshrimpcanning,howeveriftinplatecansareused,layersofparchment paper should be placed between the shrimps and the can to prevent corrosion. Hot or cold brine is filled into the cans.Fish Canning Process27FAO Corporate Document Repository i.Theexampleofmixtureforbrine:salt(2kg),sugar(1kg),citricacid(0,9l), water (100 l) j.The cans are automatically closed and transferred to retorts for processing. Figure 21 Flow sheet for canning shrimp Table 12 Examples of retorting temperatures and times for canning shrimp Preheating ConditionsProcessing Conditions Alternatives temp. (C) time (min) temp. (C) time (min) I1045011622 II10860 Further operations are as for canning tuna in brineFish Canning Process28