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The processing ofcrab meat for canning - Part ICanned fish products are important components of the export trade in several ofthe countries in the INFOFISH region and canned shellfish products are particularlyso. In this article, the author focuses on the catching and handling of crabs" withparticular emphasis on cooking and picking of crab meat. In the next issue, theauthor takes us to a cannery to observe processing techniques plus some qualitycontrol aspects in the canning of crabmeat.by P HowgateJ H Nierentz and Kheriah Arif. writing in the Advance Issue ofINFOFISH Marketing Digest. estimated that the Asia/Pacific region isresponsible for about half the worldproduction of canned shellfish. Thescope for expansion in this arealooks good . For example. van derErden in surveying the markets forcanned fish in the Netherlands andin the UK (INFOFISH MarketingDigest: Advance Issue. October1981 and Issue No 2. March 1982)considered that there was potentialfor increased penetration of cannedshellfish products from theINFOFISH region in those countries.Presumably. this is true for othercountries with similar food consump-tion patterns. Canned crab mr. et fro m the region has aconsiderable price advantage ove r that from many countries. including North America, ,,' other big supplier tothe market. The product hd'> als ' ,wed to be of acceptable quality. Some c o u n t r i l ~ . M '> :"- ia and Thailand. forexample. already have wl'll-estabiished canning industries taking advantage of t h ~ s Inar!-..-' ;c ( ~ ! g h . , ,reasesin production could be limited by S: " (!'SI"urces - andthere could be room for further dt:vdopment in othercountries.This article describes the production of canned crabmeat with an emphasis on handling and p r o c e ~ i n g before canning . The description is based on proceduresalready adopted, or would be suitable for adoption, inthe INFOFISH region . Th e process of canning crab meatis not essentially different from that of canning otherfish, or indeed food products generally. and need not bedescribed in detail here.Processing

Two parts of the total process of canning crab meat.the cooking and picking of the meat. can be carried outat the "cottage industry" level. and are well suited tocountries with artisanal fisheries . Cooking and picking ofcrabs do not require much in the way of equipment and

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is not capital intensive . It is labour intensive. but thereis often a surplus of labour, particularly female labour, infishing villages which can be employed in the task.Indeed the nimble fingers of women make them adept atpicking crab meat. There are social as well as economicadvantages in carrying ou t some processing at the villagelevel. It gives women an opportunity to be involved inthe cash economy and it means that families. and thecommunity as a whole, benefit from the added value of apartially processed product over production of a rawmaterIal alone. This makes village communities moreviable and reduces the incentive for people to drift tocities.Processing at the village level. of course. leads to considerable technological and quality control problems.Processing crab meat is not unique in this respect but,given sufficient will and dedication on the part of thevillagers, merchants and canning companies. these problems can be overcome. Methods described here areoriented towards village-level processing and discussesthe problems of quality control under these conditions.

A general description on fish canning can be found in INFOFISHMarketing Digest No 3/84.

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Catching and handling the crabsThe crabs caught in the waters of the INFO FISHregion are mostly swimming crabs of the family Por-tunidae. Of the many species making up this family. two

of commercial significance for the canning industry arethe mangrove crab (Scylla serrata) and the blue swimming crab (Porttmus pe/agicus). Both make excellentcanned products but the mangrove crab. because it isable to stay alive ou t of water for a long time. is usuallymarketed live to retail and catering outlets. It usuallyfetches a higher price at markets than the blue swimmingcrab and the latter, and similar species. are used forcanning.

Th e swimming crabs live in shallow coastal waters andcan be caught in pots and in fixed or free nets . Fishingfor swimming crabs can be carried out by small day boatsand hence is suited to an artisanal fishery. Catching byday boats is also to be recommended on technologicalgrounds because it ensures that the crab can be landedand processed in very fresh condition. Crabs are caughtby trawlers but, as these bigger boats may stay at sea forseveral days. much of the catch is not suitable for cannedcrab processing.

Crabs should be carefully handled on board the fishingvessel and precautions should be taken to keep themalive and fresh. On a day boat, which will only have oneor two of the crew using a drift net, it is usually notpossible to disentangle the crabs from the net while atsea; this is done at the landing site. Th e crabs should bekept wet with sea water and shaded from the sun . Thevessel should return to the landing site as soon as thecatch is aboard and a start should be made on recoveringthe crabs immediately.Cooking

Crab meat deteriorates rapidly after the death of theanimal predominantly because of the action of enzymesin the white flesh and in the hepato-pancreas, the brownmeat. While the crab is alive, the enzymes are undernatural biochemical control but, on the death of the crab.they work indiscriminately to degrade the quality of themeat. Digestive enzymes break down the flesh, reducingyield and imparting off-flavours to it. Other enzymes inthe flesh break down the compounds which impart thesweet, creamy flavours typical of fresh crab meat. resulting. in a lack of flavour.These enzymes are inactivated by heating. and the bestflavoured meat of the highest yield is obtained from crabswhich have been cooked alive or very soon after death .Hence. crabs should be boiled as soon as possible afterthey have been recovered from the catching vessel. I fthere is likely to be a delay between catching and delivering the picked meat to the canning factory , the crabsshould still be cooked as soon as possible. Th e cookedcrabs should then be stored, whole, in clean ice andpicked just prior to the time of collection. Where crabsare caught by boats which are not returning to landimmediately, the crabs should be boiled on board thevessel - clean sea water can be used - and the cookedcrabs stowed in ice for butchering and picking ashore.The extra effort involved is compensated for by a higheryield of better quality meat compared with landing raw.but stale, crabs.

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PROCESSINGCrabs can be cooked very simply by dropping them

into a pot of boiling water. The pot should not beoverloaded and the crabs should be fully immersed in thewater when added. The pot should be covered with a lidand heated strongly to bring the water back to the boilquickly . The crabs should be cooked for at least five minutes after the water has returned to the boil. The crabsshould not be undercooked. otherwise the meat will bemore difficult to pick from the shell. An integratedprocessing and canning factory might use a continuouscooker. These cookers, using boiling water or steam. aremore fuel efficient and give greater control over processing time than batch cookers but are clearly tooexpensive for small-scale use.

After they are cooked. the crabs should be cooled bydropping them into clean water or by spreading them ona surface to cool by radiation and evaporation of water.Butchering before picking

Butchering. i.e . the operation of evisceration of thecrab and separation of the bodies into pieces suitable forpicking, should be carried ou t just before picking of themeats and as a separate operation. Crahs should not bebutchered and picked in the same operation . Butcheringis an important step in processing and must be carriedou t carefully. cleanly and hygienically so as to achieve ahigh quality product free of contamination. Butcheringshould be carried ou t in a clean area and strenuous stepsmust be taken to keep this area free of dirt and insects.The subject of contamination is discussed in the nextsection. Receptacles for butchered sections must be madefrom metal or plastics and not from natural fibres.Natural materials cannot be cleaned properly. whilewoven materials harbour dirt and insects. Obviously.containers must be scrupulously cleaned before use.

The cooked crabs should first be washed to removesand, mud and protein scum. The claws and legs aredetached and put in a container. The back shell. thecarapace, is pulled of f the body and the viscera completely and carefully removed . The coral. the gonads.can be separated out from the viscera to be used in thehome or sold to restaurants.

Th e cleaned-out body is broken into two pieces downthe mid line of the shell and small pieces of shell re-Blllchered crabs alld bags vf picked alld graded /1/ell/I- - ! I ' - " " " ' " " ! " ' l ' I I I I l ~ ~

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Crab pickingmoved. It is important that all the small appendagesaround the mouth are completely detached as well . If lefton, there is the danger of the small hair-like setae withwhich they are covered .getting into the meat at thepicking stage. The body sections should then be washedin clean, potable water and inspected to ensure they arefree from shell particles and foreign matter. The cleanedand inspected sections are put in clean containers, separate from the claws and legs. The containers should becovered to keep their contents free from insects and dirt.

Picking the meatsPicking is the operation of extracting meat from thebody sections, claws and legs. The extracted meats arevulnerable to contamination and great care must be

taken to keep the meats free from dirt and insects duringpicking and on subsequent storage. Picking must becarried out under clean and sanitary conditions and,though ideal conditions for exclusion of contaminationare difficult to achieve in a village industry, there aresimple precautions which can be taken to reduce itsincidence.Containers of butchered crab and the receptacles forholding the picked meats should be raised off the flooron a table or bench. The outsides of the containersshould be wiped clean before they are put on the table.The legs of the table should be stood in containers of oilto prevent crawling insects from getting onto the workingsurface. In addition, the containers for the picked meat,small basins or plastic bags, should be stood in a tray ofwater as a further barrier to crawling insects. Containersof butchered pieces and the containers of picked meatsshould be covered by cloth as far as possible consistentwith carrying out the job . Butchering and picking shouldbe carried out in areas as free from flies as possible. i .e.in areas which are clear of rubbish.Meat can be picked from body sections by fingers only,but many workers often find it easier to use a small,narrow-bladed knife. The most valuable meat, referredto as lump meat or shoulder meat. is found withinchambers around the edge of the shell corresponding tothe points where the legs join the body. The sections can

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be carefully broken at these chambers and the piecespicked out intact. More white body meat can be extracted from elsewhere in the shell.

Meat is extracted from the separate segments of thelegs, and claws. I f fingers are being used for picking. thesegments are carefully broken by striking with a piece ofwood or by bending until they crack and the meat extracted. The aim is to remove the meat as a single piecebut this is not always easy if the segments have to bebroken. It is somewhat easier if a knife is used. Thesegment is cut near a joint exposing the end of the pieceof meat. This is carefully pulled out in one piece. Legand claw meat is mottled brown on the surface and mustbe kept separate from the white meat.

The yield of meat from blue swimming crab is about30% of the uncooked weight when carefully picked.Canners pay the highest price for lump meat and least forsmall pieces of leg meat. The various grades must notbe mixed. It is best if the meat is put directly intoseparate containers for each grade. Plastic bags are veryconvenient, otherwise basins can be used. The containersshould rest on a clean surface and be protected frominsects and dirt. Waste material should be disposed ofinto a container away from the surface where the pickedmeats are laid out. For example. if the containers ofmeats are on a table, the rubbish should be thrown into abasket under it.When picking is finished. the bags of meat should beclosed or the basins covered and stored in a cool place. I fpossible, the containers should be packed in ice. _

Code of Practice Crabs should be alive or only just dead whenthey are cooked. Crabs should be cooked for at least five minutesin boiling water. Crabs should be butchered and the meats pickedstraight away after cooking or , if there must be adelay, stored in ice. At the butchering stage, all the viscera and all

the mouth parts should be removed and thebutchered sections well washed . The meats should be picked in clean, sanitarypremises and protected from contamination byflies and any other foreign materials. Picked meats should be packed to prevent contamination, chilled quickly and, if not picked inthe canning factory, kept chilled during distribution.

Mr Peter Howgate is Principal Fisheries Officer with the Torry Re-search Station, Aberdeen, Scotland, UK, since 1965. He is involvedlargely in research and the practical application of quality control forfish products in both developed and developing fisheries.This article is Crown Copyright, 1984

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