FAO Corporate Document Repository 2. RAW MATERIALS 2.1 Fish and Other Marine Foods Manytypesoffish,andothermarinefoodsaresuitableforcanning,thesizeofthe individualfishvaryingfromthatofthesmallestsardinestothatofthelargesttuna species.Forsomespeciesliketunaandsardinescanningisthemostimportant processing method. Other species, suitable for canning are salmon, mackerel, herring, clams, oysters, shrimps, octopus, crab and white fish paste products. TheCodexAlimentariusCommissionrecommendsthefollowingspeciesofTuna, Bonito, Salmon and Shrimps to be canned: Canned Tuna and Bonito (CODEX STAN 70-1981) Thunnus alalungaEuthynnus affinis Thunnus albacaresEuthynnus alletteratus Thunnus atlanticusEuthunnus lineatus Thunnus obesusEuthynnus pelamis (syn: Katsuwonus pelamis) Thunnus thynnus maccoyiiSarda chiliensis Thunnus thynnus orientalisSarda orientalis Thunnus thynnus thynnusSarda Sarda Thunnus tongollSarda velox Canned Sardines (CODEX STAN 94-1981) Sardinops melanostictaSardinella aurita Sardinops neopilchardusSardinella anchovia Sardinops ocellataSardinella brasiliensis or Sardinops Sagax or Sardinops caeruleaSardinella maderensis Sardina pilchardus (Walbaum) Clupea harengusHyperlophus vittatus Clupea antipodumNematolosa vlaminghi Clupea bassensis orEtrumeus microps Clupea fuegensisEthmidium maculatus Sprattus sprattusEngraulis anchoita (Clupea sprattus)Engraulis ringens Canned Pacific Salmon (CAC/RS 3-1969. Rev.1) Oncorhynchus nerkaOncorhynchus gorbuscha Oncorhynchus kisutchOncorhynchus keta Oncorhynchus tschawytschaOncorhynchus masou Species of the families PenaeidaeCrangonidae and PandalidaePalaemonidae A variety of products can be made using minced fish as main raw material. Fish Canning Process1FAO Corporate Document Repository Unutilizedorunderutilizedspecies(socalledtrashfish)withanutritionalvalue comparable to that of valued food species can be an excellent source of raw material. To plan the handling and processing of fish and to manage problems connected with all operations from transport and processing through storage, it is essential to know the physicalandchemicalpropertiesofthespeciesinvolved;thesepropertiesinclude shapeandsize.thermalconductivity,chemicalcompositionoffishandconditions regarding post mortem changes. See Table 4. Table 4.Various parts of the fish expressed in percentage of total weight and total fish weight per cubic metre, for some important species used in canningPercentage of total weight Species Head Skin & flesh BonesFinsViscera ton/m Atlantic herring 12.562.26.51.515.00.91 Sardines21.058.06.52.59.50.85 Atlantic mackerel 22.552.08.01.019.50.96 Tuna18.064.08.02.08.0 Pink salmon 16.071.0 1/-5.08.00.95 1/ Including bones and gonads 2.2 fish handling 2.2.1 General InformationaboutfishhandlingpriortocanningisgivenindetailinPlanningand Engineering Data, Fresh Fish Handling, FAO Fish. Circ. 735. In this context these data are of most value where they concern operations of special importance for canning. 2.2.2 Fish handling on board After washing, the raw material should be chilled as soon as possible, and kept chilled until unloading. Depending on the type of fishing vessel the catch can be iced in boxes, containers, or shallow bins. Inpractice,however,methodsforhandlingfishonboardvaryfromdoinglittleor nothing, to chilling or freezing, depending on the type of vessels, area of catching and fish species.Withlargefishliketunathemostcommonmethodofhandlingonboardsmaller vessels is washing and chilling with water and/or ice. Larger vessels are equipped with tanks in which the fish is chilled. These tanks are either chilled sea water (CSW) tanks or refrigerated sea water (RSW) tanks. The CSW- tanks are chilled with ice, and the RSW- tanks are chilled by refrigeration. Air blast and brine freezing methods are also commonlyused.Formoredetailsconcerningfreezingmethods,see"Freezingin Fisheries". FAO Fisheries Technical Paper no. 167. Fish Canning Process2FAO Corporate Document Repository Smaller species are chilled in CSW or RSW- tanks, and when in small quantities, iced in boxes.Industrial species intended for mincing must be handled (as with any high valued food fish)accordingtogoodhandlingpractice.Thefishmustbewashed,andiftheraw material is by-catch from bottom trawling, all mud, sand, etc. must be rinsed away. If possible, the fish must be sorted, but in some areas this is difficult as the catch consists of several species, each in small quantities. 2.2.3 Unloading fishing vessels Care must be taken during unloading and handling in order to avoid bruised fish and/or skin abrasions. Allhough systems for unloading and handling fish depend on various factors, the most common methods are as follows:i.Freshfishishumpedfromthefishholdthroughscalesorvolumemeasuring equipment to rolling conveyors for further -transport, or directly to tanks, bins, etc.ii.Freshorfrozenfishisloadedintobasketsorcases,heavedtothequay,by eitherelectricaldockhoistsorbyuseofthevessel'sownwinch.andthen tipped into containers, before transport, or into bins before gutting or transport. When the fish is iced into boxes, Jor containers. on board. it is unloaded in a similarway.Whentheboxesarestackedonpalletstheentirepalletloadis heaved up.iii.Fish kept in CSW or RSW-tanks is heaved from the fish tank by use of nets. Fish in bulk may also unloaded this way.iv.A conveyor system may be used for unloading fresh and frozen fish.2.2.4 Fish handling on land The processes and principles involved in preparing fresh fish for canning are, for the most part, similar to those that would be involved in preparing them for marketing as freshfish.ThereforethegeneralinstructionsdescribedintheRecommended InternationalCodeofPracticeshouldbeusedasaguideforthehandlingand preparation of fresh fish for canning (CAC/RCP 9-1976 and CAC/RCP 10-1976). Forinformationconcerningicing,CSW,RSW,chillstorage,containersforraw materials, materials, freezing and frozen storage, readers are referred to planning and EngineeringDataI-FreshFishhandling,FAO,Fish.Circ.735,andfreezingin Fisheries, FAO Fisheries "-"' Technical Paper no. 167". If the fish consists of industrial species, and sorting is not practical, the raw material can be stored in containers and mixed with ice until use. If possible, the fish should be kept in the same boxes or containers, without emptying and reicing, as this will be the best means of maintaining quality;. sometimes however this is not possible, especially incaseswherethefishermenwanttheircatchesweighedimmediatelyafterlanding. The less the handling of the iced and boxed/containerized raw material, the longer will quality be maintained. It is not recommended to freeze fish which is to be used as a minced raw material. Fish Canning Process3FAO Corporate Document Repository Frozen fish can be thawed by immersion in chilled water (temperatures above 15 C are not advisable), water spraying or air current exposure. Thawing of frozen fish is an important step in canned fish manufacture. For larger species, like tuna, thawing up to 12 hours or more is not unusual. As thawing of the fish is progressive, smaller species, and exterior parts of larger species may reach the desired state of thaw while the inner parts of larger species remain frozen. Deteriorationoffreshfish,especiallywholeunevisceratedtuna,israpidat temperaturessufficienttohastenthawing.Thequalityofthefreshtunabeginsto diminish before the last thawed portions have become unfrozen. 2.3 Ingredients and Additives 2.3.1 Quality requirements for water All water available for use in those parts of an establishment where fish and shell fish are received, kept, processed, packaged and stored should be potable water or clean sea water and should be supplied at pressure of no less than 1.4 kg/cm. An adequate supply of hot water of potable quality at a minimum temperature of 82C should be available at all times during the plant operation (CAC/RCP 9-1976). Thecoldwatersupplyusedforcleaningpurposesshouldbefittedwithanin-line chlorination system allowing the residual chlorine content of the water to be varied at will in order to reduce multiplication of micro-organisms and prevent the build-up of fish odours. Water used for washing or conveying raw materials should not be recirculated unless it is restored to a level of potable quality. Non-potable water may be used for such purposes as producing steam, cooling heat . exchangersandfireprotection.Itisveryimportantthatboth-systemsofstorage and distributionofpotableandnon-potablewaterareentirelyseparateandthereisno possibility for cross-contamination or for inadvertent usage of non-potable water in the fish or shellfish processing areas. Only potable water should be used for the supply of hot water. The same requirements for the separation of systems would apply to clean sea water when it is used in the processing of fish (CAC/RCP 9-1976). 2.3.2 Quality requirements for other ingredients and additives Saltusedformakingbrineorotherpurposesshouldbepureandnotcontain appreciablequantitiesofmagnesiumchloride,acommoncontaminantofunrefined salt.Ifthesaltcontainstoomuchmagnesiumchloridetheriskofstruviteformation increases; this may concern consumers as struvite can form crystals resembling glass in the canned fish. Salt should comply with the "Codex Alimentarius Specifications for Food Grade Salt" (being-developed by the Codex Committee on Food Additives). Olive oil intended for canning has to be one of the two following categories (Research Laboratory of the Norwegian Canning Industry): Fish Canning Process4FAO Corporate Document Repository i.Virgin olive oil produced by mechanical processes, or:ii.Olive oil produced by blending of virgin olive oil with chemically refined virgin olive oil which is produced from pure virgin olive oil.Olive oil intended for canning Norwegian sardines may be blended to a maximum of 35 %withchemicallyrefinedoil.ForcannedfishotherthanNorwegiansardines, chemically refined virgin oil as such is accepted in addition to the olive oil specified. Oliveoilshouldbeextractedfromsoundolives,withoutanyadmixtureofotheroils (fat). Further, the oil must be free from any admixture of refined solvent-extracted olive oil. Synthetic olive oil is strictly forbidden. The oil shall be clear, free from mucilage, mould or other impurities. The oil shall also be free from moisture. The colour of the oil shall be yellow to golden with only a slight tinge of green. Odour and taste of the oil shall be pure, good and natural, not acrid, bitter or too strong. The oil must be resistant to cold. Soya bean oil should be free from foreign and rancid odour and taste. Colour additives are permitted for the purpose of restoring natural colour lost in processing or for the purposeofstandardizingcolour,aslongastheaddedcolourdoesnotdeceiveor misleadtheconsumerbyconcealingdamageorinferiorityorbymakingtheproduct appear to be of greater than actual value. Maximum level of use is not limited for such additives. Natural flavours and their identical synthetic equivalents, except those which are known torepresentatoxichazard,andothersyntheticflavoursapprovedbytheCodex Alimentarius Commission, are permitted if they fullfill the limitations mentioned in the text above. Other additives as antioxidants, antioxidant synergists and crystallization inhibitors are permitted in soya bean oil. Tomato sauce should be made from sound raw materials without any decomposition by mould, yeast or bacteria. The canned tomato sauce should not contain microbes which can develop at a normal storage temperature. The colour should be red, even with a faint tinge of yellow, but never brownish. Odour and taste should be pure and natural. The tomato sauce should be heterogeneous and not contain too much seeds or skin. The total solids shall not exceed 30% (Tripple concentrated tomato sauces are not be permitted). The content of sugar is not permitted to be reduced below 40% of. the total amount of solids. Thetomatosaucemustnotcontainanyextraneousmatters(suchascarrotsetc.). Artificiallycolouringoranykindofpreservatives,exceptsaltarenotpermitted. (Research Laboratory of the Norwegian Canning Industry). Examples of other ingredients and additives used in the canning process are: Fish Canning Process5FAO Corporate Document Repository Pepper (Piper nigrum l.)Cardemon (Elletria cardamomum)Ginger (Zingiber officinale roscae)Onion (Allium cepa allium ascalonicum)Spiritvinegar(Solutioncontainingvinegaracid,CH3COOH, concentrate from 4 to 12 %)Ground mustard seed (Brassica species)Curry powderStarch (potatoes flour)Mono Sodium Glutamate (MSG)Stabilizing agents as sodium alginate and gum tragacanthMilkSugarWineBeerThe ingredients should be suitable for human consumption and be free from abnormal taste, flavour and odour. 2.4 Packaging Materials The most common material used for manufacturing containers for fish products are tin plate, aluminium and lacquered steel plate (TFS). Flexible packaging as an alternative tometalcanshasbecomemorecommonduringthelastyearsandglassjarsare sometimes used for speciality packs. 2.4.1 Tin plate Tin plate is steel sheet coated with a thin layer of tin on each surface. Because of its strength and rigidity tin plate forms an ideal material for food containers. In addition to the benefits of its bright appearance and ease of soldering, the major function of the tin layeristoprotectthebasesteelfromcorrosion.Mechanicalpropertiessuchas strength,stiffness,etc.,arecontrolledinthemanufacturingprocesstosuitthe specifications of the can maker. Minimum thickness of tin plate for can making is 0.15 mm(Palling,1980).Themainfactorsofimportancearechemicalcompositionand physical properties of the base plate, thickness of tin coating, application of protective coatings and relative corrosivity of the product which is to be canned. Low carbon steel is used for can manufacture. The chemical composition of the base steelplateisofprimaryimportanceinobtainingadequateservice-lifeforcorrosive, products; the most critical element is phosphorus, but other elements such as copper nickel, chromium and silicon may also affect the corrosion resistance of the plate. 'Two basic types of stell (L and MR) are used for different food products and a third type (D) is used for unusual drawing operations. For low-acid products, such as fish the steel typehasnoimportantinfluenceoncorrosionandanyoftheavailabletypesmaybe used,neverthelessMRsteelisusuallyrequired.Originallytinplatecoatingweight specificationswereexpressedintermsofthe"basebox"whichwasanindustry measure. Tin plate was sold in only one size sheet (356 x 508 mm), and bundled 112 sheets to a package. The total area of plate in such a package (20.22 m2) came to be known as a base box, the weight of which varied with the thickness of the steel (Ellis, 1979). Fish Canning Process6FAO Corporate Document Repository Formerly, tin plate was made by immersing sheets of "black" plate in molten tin (hence thisplatewasknownashotdipplate).Nowadayselectrolyticplatingtechniquesare used to apply tin to the base steel plate. This method permits thinner tin coatings (0.38 to2.03microns)oneachsideoftheplatesurface.Theelectrolytictinningprocess permits also a close control over deposition of the tin coating layer. The most common coating weights are 0.25, 0.50, 0.75 and 1.00 lb per base box which corresponds to 5.6, 11.2, 16.8 and 22.4 g/m, respectively (when considering both plate surfaces). In themetricsystemcoatingweightisexpressedastheweightoftinoneachsurface. Thus a total tin coating weight of 5.6 g/m is listed as 2.8/2.8 g/m (Ellis 1979), which signifies that on each surface the tin coating weight is 2.8 g/m. Differentially coated tin platehasdifferenttincoatingweightsoneachsurface;theheaviercoatingusually being on the inside of the container. 2.4.2 Tin-free steel (TFS) The tin-free steel is one of the newer can-making materials. Untinned steel on which verythinlayersofchromium-oxidehavebeenelectrodepositedisresistanceto corrosion and discolouration. Disadvantages are that the plate must be, coated on both sides and that it cannot be soldered. It is principally used for the ends of the cans. 2.4.3 Aluminium alloys Aluminium alloys are finding increasing use in the can making industry. Advantages of aluminium include the light weight of the material resistance to atmospheric corrosion andtosulfide-bearingproducts(commonlyfoundinfishproducts)andversatilityfor makingcontainersbydifferentmethods.Disadvantagesincludedifficultiesinclosing the body seam by soldering and the necessity for heavier gauges which are required to obtainstrengthcomparablewithtinplate.Sheetmadewithpurealuminiumhas mechanicalandphysicalpropertieswhichlimititsuseasacan-makingmaterial. Increasedstrengthisobtainedbyalloyingaluminiumwithoneormoreothermetals such magnesium and manganese. Minimum thickness of aluminium for use in fish cans is 0.28 mm. 2.4.4 Enamel coatings Enamel coatings are used to protect tin plate, aluminium alloys and TFS, The coatings canbeappliedtosheetsandcoilseitherbeforeandaftercansaremade.Insome cases, coatings make it possible to use more lightly coated grades of tin plate or tin-free steel. The enamels or lacquers were originally prepared from polymerized fish oil buttodaylacquersaremadefromsyntheticmaterialswhichprovidebetter performance. 2.4.5 Retortable pouches Retortablepouchesforthermoprocessedfoodasanalternativetometalcansand glassjarshavefoundincreaseduseduringrecentyears.Thepouchesareheat sterilized in retorts and the sterility maintained by the impermeability of the material and the hermetic seals of the pouches. Characteristics for their use include (Lampi, 1979) convenience fore-heating by immersion in boiling water. rapid sterilization as the flat. thincrosssectionofthepouchpermitsrapidheattransfertothecontents.energy conservation. and space utilization. Fish Canning Process7FAO Corporate Document Repository Retortablepouchesaremadefromrigidorflexiblematerials.Rigidpouchesare constructed with high density polyethylene (HDPE), whereas flexible pouches may be made from a lamination which consists of an outer polyester ply, an aluminium foil, as the primary material. and an inner ply which is made of modified polyolefin (medium to highdensitypolyethylenemodifiedwithpolyisobutylene)orcastpolypropylene. Products are being commercially packed in a film described as 12 microns polyester, 9 microns aluminium oil, 15 microns nylon and 50 microns polypropylene, and processed at temperatures up to 135 C for times ranging from 2.7 to 9 minutes (Lampi, 1979). 2.4.6 Glass The principles of processing with glass are substantially the same as for cans, except that there are some modifications necessary because of the sealing mechanism used andthethermalcharacteristicsoftheglass.Aswithcans,glasscontainersmustbe hermeticallysealed;thisisachievedbyusingametalclosureintowhichhasbeen placed a plastisol lining compound that acts as a sealant between the glass and the metal cap. Glasscontainersareprocessedunderwaterinacounter-balancedretort.Thewater preventsthermalshockbreakageassteamenterstheretortwhilethecounter-balancingairtransmitspressurethroughthewaterensuringthatatalltimesthe pressure in the retort is greater than that in the sealed container. As glass is resistant to all food products no internal surface treatment is required. The metalclosureshowevermustbeprotectedfromcorrosionandforthisreasonare internally and externally lacquered. Table 5 Size of 2-piece cans for different types of the most important fish products Type of can Material Volume (ml) Length(mm) Width (mm) Height(mm) Product Net weight (g) Fish weight(g) 1/4 dingley aluminium tin plate 1121057621.5 sardines, small fish 10685 1/4 club * aluminium tin plate 1151056029 sardines, small fish, tuna 12595 1/2 hansa * aluminium tin plate 2001488126herrings195130 1/2 oblong aluminium tin plate 212154.76130kippers225225 1/3 ovaltin plate2001498125mackerel195130 1/2 ovaltin plate2701498125mackerel250180 * Noblikk-Sannem A/S standards. Table6Sizeof2-and3-piececansfordifferenttypesofthemostimportantfish products Type of can Material Volume (ml) Diameter(mm) Height (mm) Product Net weight (g) Fish weight (g) 2-piece round aluminium2259040shrimp217150 2-piece round aluminium1157832shrimp11175 Fish Canning Process8FAO Corporate Document Repository Type of can Material Volume (ml) Diameter(mm) Height (mm) Product Net weight (g) Fish weight (g) 2-piece 1/2 pound round aluminium tin plate 2459044 fish with vegetables, herring, tuna 230* 2-piece 1 pound round tin plate49012049 fish with vegetables, herring, tuna 460* 3-piece round tin plate21283.846tuna200155 3-piece round tin plate40099.560tuna377292 3-piece round tin plate45072119 cod roe in brine 425300 3-piece round tin plate45010164fish cakes400260 3-piece round tin plate900101121fish balls800520 3-piece 5 kg round tin plate4 250218123 tuna, sardine 4 0003 100 3-piece 10 kg round tin plate8 500218245tuna8 0006 200 * Depends on amount of vegetables. 2.4.7 Construction of metal containers Metal containers are normally divided into two groups:2-piece cans (square, oval or round).3-piece cans with soldered or welded body (square, oval or round).Specifications for the most common metal containers are shown in Tables 5 and 6. Fish Canning Process9