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As the name implies, there are two heat treatment procedures involved in the manufacture of precooked-cooked products. The first heat treatment is the precooking of most of the raw meat materials at temperatures below 100°C, usually in the range of 80°C. The second heat treatment is the cooking of the finished product mix at the end of the processing stage. This second heat treatment is carried out either at pasteurization temperatures (around 80°C) for sausages filled in natural and artificial casings resulting in a limited shelf-life and the need for refrigeration. At sterilization temperatures (above 100°C) canned products are filled in glass jars, tin or aluminium cans or similar, have extended shelf-life and do not require refrigeration. Precooked-cooked meat products are not only distinguished from the other categories of processed meat products by precooking most of the raw materials prior to grinding or chopping, but also by utilizing the greatest variety of meat, animal by-product and non-meat ingredients (Fig. 185, 186).

The raw meat materials used for precooked-cooked products are lower-grade muscle trimmings, fatty tissues, head meat, animal feet, animal skin, blood, liver and other edible slaughter by-products.

Fig. 185: Typical precooked-cooked products. Liver sausage (left), blood sausage (centre) and gelatinous meat mix (right)

Fig. 186: Typical precooked-cooked products in glass jars. Liver sausages (left), gelatinous meat mix (centre) and blood sausage (right)

Precooked-cooked meat products contain mixes of those animal tissues which are generally of good nutritive value.

The processing to precooked-cooked products results in attractive and palatable varieties of animal food items. In many formulations, precooked-cooked products also contain cereals and other plant materials, depending on local availability and consumption habits.

General principles of manufacture

The animal tissues for precooked-cooked products are heat treated (“precooked”) prior to their further processing. The precooking is done for the following reasons: Precooking facilitates the removal of soft animal tissues (muscle meat, fat, connective tissue) from bones of heads, feet etc. and makes tissues such as skin softer and better to handle for the processing steps to follow. In addition, precooking substantially reduces the bacterial content of the mentioned raw materials. These raw materials (skin, trimmings, heads, feet etc.) often have relatively high bacterial loads as they are more exposed to contamination during slaughtering and meat handling than muscle meat. Hence not only the second heat treatment but also the precooking is crucial for the shelf life of the final products. Remaining hairs on skin, feet and heads should be carefully removed before precooking.

The raw materials of animal origin used for precooked-cooked products are all highly perishable. Therefore meat processors should not only rely on the germ-reducing effect of the two heat treatments, but must also obtain and process these materials under good hygienic conditions. Internal organs must be trimmed and cleaned thoroughly immediately after slaughter. Product manufacture should start immediately after preparing the animal tissues for further processing in order to obtain fresh flavour and taste in the final products.

The fact that all ingredients of animal origin were subject to precooking applied to the initial fabrication of precooked-cooked meat products. In modern meat processing, modifications in processing technology were introduced regarding the use of blood and liver. Liver (for liver sausage) and blood (for blood sausage) are added uncooked (raw) to the mixtures, with the aim of improving fat- and water-binding ability in processed liver products and colour in processed blood products. The addition of raw liver and raw blood requires very careful hygienic handling of these materials before processing in order to keep their microbial load low.

Precooking periods depend on the nature and size of the carcass part, age of the animal and desired characteristics of the final product. As the precooking times for most of the animal tissues differ, they have to be cooked separately. Raw materials with bones and rich in connective (collagen) tissue, such as pig heads, tails and feet are cooked until the soft tissue can be easily manually separated from the bones. Pig skin (with meat, fat and hairs carefully removed) is only partially cooked until soft enough to be ground in the mincer. Over-cooking should be avoided, as it would make tissues too soft. The precooking temperatures must be carefully balanced and should be kept in the range of +80°C to +90°C, with tissue core temperatures not exceeding +65°C. The precooking also results in weight losses (cooking losses; up to 30%) of the heat treated animal tissue. The cooking loss is often compensated by adding equivalent amounts of water or hot meat broth (deriving from precooking in the cooking vat) to the final mixture. The addition of cooking broth will also enrich the taste of the final product. National regulations need to be observed regarding the amount of broth added.

Combined equipment for precooking and comminuting

A new and advanced technology for precooked-cooked meat products is the utilization of “cooker-choppers”. These are bowl choppers with a steam heating device covering the bowl from below and a double jacket for steam injection in parts of the lid. Low pressure steam is injected, which heats up the chopper bowl and the lid and allows the precooking of raw materials directly in the bowl. This way, precooking and comminuting can be done simultaneously in one process, which, apart from time saving, has the advantage of avoiding cooking losses from the raw materials. As in all heat treatments, process water, proteins, fats and minerals will be cooked out from the raw materials. But unlike in cooking vats or cooking chambers, these substances are not wasted but remain in their full amount in the product mix in the cutter bowl. This contributes favourably to flavour and nutritional value of the final products. By regulating the steam supply, precooking periods and temperatures can be adjusted as in conventional manufacture. In the specific case of liver or blood products, liver or blood is added raw after the precooking phase similarly to conventional manufacture. Cooker cutters are technically complicated and relatively expensive and are mainly applied in industrial scale meat processing.

Fig. 187: Schematic drawing of cooker-chopper (cross section)
Steam injection in chopper lid and in space below chopper bowl (pink colour).
a = chopper bowl
b = chopper lid
c = steam container below
chopper bowl
d = plastic washer between
rotating bowl and
stationary steam
container (to prevent
escape of steam)
e = steam inlet
f = opening for cleaning
g = chopper knife

According to the ingredients used, five types of precooked-cooked sausage products can be distinguished:

Liver sausage
Blood sausage
Cooked gelatinous meat mixes
Cereal sausage
Corned beef

Pork belly, soft tissues, meat bones

Pork skin, heads and feet

Fresh (raw) blood

Fresh (raw) liver, lungs, heart

Lower-grade muscle meat/beef (for corned beef etc.)

Lower-grade muscle meat / beef (for corned beef) from close range

The choice of animal tissues and quantities to be used depends on the type of precooked-cooked meat product to be manufactured (Fig. 188). For liver sausage or liver pate products, which are ground to finely comminuted mixtures, the amount of fatty tissues is usually high while connective tissues should be reduced. This is because these foods are commonly used as sandwich spreads and should be soft. Blood sausage products should be rich in connective tissues (e.g. addition of animal skin and utilization of meat from heads and feet) in order to obtain a gelatinous texture of the final product. Similarly also for gelatinous meat mixes, animal parts with high connective tissue content are needed. These latter two types of precooked-cooked products can be cut in slices when cold, which is the usual form of preparation for consumption. For Corned beef lean beef is the main ingredient and only for lower qualities also second grade beef with some adhering fat and connective tissue may be used. For cereal sausages there are no firm rules but local habits and preferences apply.

Liver sausage / liver pate products (recipes page 418, 419)

Liver sausages or liver pate are amongst the most popular precooked-cooked products. The basic product mix may be composed of precooked lean meat trimmings (see page 45), softer or firmer fatty tissues preferably from pigs (body fats such as jowls, belly fat or back fat; internal fats such as kidney fat or intestinal/mesenterial fat, see page 11) and for low cost products other soft animal tissues (for example hearts, lungs, spleen, tripes, Fig. 188). At least 10% and a maximum 35% liver is added as the major and typical component and provides the name for this meat product and contributes to its unique flavour and taste. Liver contents of more than 35% are unusual and could result in a bitter taste in final products. The main types of liver products are the coarse-mixed type and the fine-comminuted (“emulsion-like”) type, but also combinations of the two types (fine-comminuted basic mix with integrated coarse particles) exist.

Animal tissues used and their origin

The correct treatment of the fresh livers plays an important role for the quality of the final products and should be effected immediately after slaughtering. All white bile ducts and large blood vessels as well as the liver lymphnodes should be cut out. The trimmed livers should be rinsed in cold water to wash out remaining bile content in order to remove bitter taste. This procedure is also needed for those livers which cannot be used instantly for further processing but must be stored refrigerated or frozen.

Pork liver as well as soft fatty tissues from the pork carcass have proven to be particularly well suited to achieve the desired texture and taste in liver sausage/liver pate products. Moreover, there are no significant differences in the processing suitability of the various types of pork fatty tissues for finely comminuted liver products. For coarse liver products it is preferable to use the firmer body fats.

Where local and cultural traditions demand meat from other animal species, pork meat materials can be replaced by meats deriving from bovines, small ruminants and poultry (including large birds with high meat yield such as ostriches). In particular chicken liver has proven to be a suitable replacement for pork liver. Up to a certain extend vegetable oils can be used as pork fat substitute. The manufacturing techniques remain basically the same, no matter from which animal species the raw materials derive.

Coarse-mixed liver products

This type of liver sausage can be manufactured in a simple way even in small operations as only meat grinding and filling equipment and a cooking vat (see page 244) is required. The animal tissues are precooked as soon as possible after slaughtering to retain the fresh taste and flavour. Then the precooked materials are cut in smaller pieces and mixed with the fresh1 liver and all other ingredients such as common salt2 and spices. Usually also vegetables (mostly peeled and blanched onions) are added. The mixture is then coarsely minced by using a meat grinder with a perforated disc with holes of the desired size (3-6mm) (Fig. 189).

After mincing, the coarse mix is portioned. The most popular way of portioning is to fill the coarse mix in natural or artificial casings of medium to larger diameters (Fig. 189). The coarse mix can also be filled in glass jars or cans for heat sterilization (see Fig. 189, 195). After filling, the second heat treatment takes place.

1) In the case of coarse-mixed products liver can also be added blanched or precooked instead of fresh as no fat and water binding properties are required. Precooked liver will keep the bacterial load of the mix at a lower level.

2) In the coarse-mixed type liver sausage products usually common salt is used, hence a curing reaction does not take place and the colour of the final products remains grey.

In smaller operations, coarse-mixed liver sausages are heat-treated (pasteurized) in hot water in an open cooking vat. To prevent bursting in case of using natural casings (see Fig. 192), the water temperature in the cooking vat must be kept below +85°C. However, a core product temperature of +74°C must be achieved. For tropical regions, synthetic casings may be better suited as the cooking can be done more intensively even in boiling water including higher core temperatures above +74°C. The cooking time also depends on the calibre of the sausages. As a rule of thumb, one minute cooking time per mm diameter is recommended, which means that sausages of calibre 60 (60mm diameter) have to be cooked for 60 minutes (one hour). In larger industrial operations, heat treatment is not done in an open water bath, but by using steaming chambers or by passing the goods through steam conveyer cookers.

Fig. 189: Production steps for coarse liver sausage

Step 1: Preparation of raw materials:
fresh (raw) liver (right), precooked
lean and fatty tissue (left) and fried
onions (centre)

Step 2: Manual pre-mixing of raw materials, spices and salt

Step 3: Mincing of mix through a perforated disc (3 mm)

Step 4: Stuffing of mixture into natural casings

Coarse liver sausage mix in different formats: (natural casings, artificial

After cooking the immediate cooling of the products has to be initiated. In most cases this is done by submerging the hot liver sausages in cold running water with a temperature below +12°C to initiate a fast drop of temperature in the product. In tropical countries the use of ice water is recommended. Sausages in artificial casings can be cooled down completely in cold water and directly transferred to the cold room for storage. Sausages in natural casings are also initially cooled down in cold water until a core temperature below +20°C is achieved. They are then transferred to the cold room for complete cooling down. Excessive cooling in cold water would extract flavour and also soften the natural casings. If smoking is intended it should be only done after the sausages have been chilled completely. For coarse-mixed liver sausages in natural casings cold smoke (below +20°C) is applied for flavour, taste and preservation (see page 41). Sausages with wider calibres are usually consumed cold as sausage spreads. Sausages with smaller calibres are sometimes also fried and consumed hot.

Fine emulsion-like liver sausage and liver pate

As a first step in the manufacture of fine emulsion-like liver sausage/liver pate, fresh cold liver1 with its high protein network building potential is chopped in the bowl cutter (Fig. 190) with all the nitrite curing salt2 calculated for the whole batch until a fine batter with a light pink colour is achieved. Sodium ascorbate (0.05%) can also be added to further enhance the curing reaction (see page 37, 68). If sugar is part of the recipe, it should also be added here to counteract any possible bitter taste originating from the liver. The liver batter is then transferred to the chiller and usually kept overnight for processing the next day. This resting period facilitates the development of a desired curing colour and further extraction of protein.

In the next step, hot (65°C) pre-cooked meat materials (mixture of trimmings of lean meat, fatty tissues, often also head meat and other soft tissues) are first minced (8-13mm) and placed in the bowl cutter. Hot meat broth (to compensate for the cooking loss of the pre-cooked materials) and optionally emulsifying agents 3 are added and the mixture is chopped until a fine structure is achieved.

1) The processing suitability of frozen liver is similar to fresh liver. But it should be noted that trimming and washing immediately after slaughter and before freezing is required.

2) In this specific case the blood pigment haemoglobin, present in larger quantities in the fresh liver tissue, is cured.

3) Emulsifying agents serve to enhance the emulsifying properties of liver. For fresh sausages specific mono– and di–glycerides are available. If the sausage mix is to be used for canned sterilized products, glycerides are not suitable and milk protein (2%) is used instead.

Fig. 190: Pre-chopping of raw liver (with curing salt). This batter is added later to the precooked hot meat materials (see Fig. 191)

Fig. 191: Addition of chilled liver batter: The liver batter is added to hot precooked and pre-chopped meat materials in the bowl cutter. Bowl cutter is kept rotating in low gear.

When the mixture reaches a temperature between 45°C and 60°C, the cold pre-chopped liver and all spices are added (Fig. 191) and the mixture is chopped to its final degree. Thereafter the mixture is ready for stuffing. The type of liver sausage mix or liver pate is usually filled in plastic casings or larger diameter natural casings. During filling, the temperature must be kept above +35°C to avoid possible fat separation at this stage, below +35°C fat starts to solidify.

The subsequent second heat treatment should be carried out without delay after fabrication of the product mix to minimize hygienic hazards. By keeping the batter or filled casings and cans over a prolonged period uncooked, strong microbial growth and enzymatic activities can start and will rapidly deteriorate the products resulting predominantly in an unpleasant acidic taste. This is due to the elevated temperature of the mix, which can contain significant numbers of microorganisms, in particular because some of the ingredients (liver, non-meat additives) were incorporated without precooking.

The fine emulsion-like liver sausage type is consumed cold as a sausage spread. As local specialties, finely chopped liver sausage may contain non-meat ingredients such as onions, mushrooms, special herbs and in particular cream/milk. Such products are called “liver patÄ—” (Fig. 196).

Texture building in fine emulsion-like liver products

The finished liver sausage or liver pate products have a soft creamy texture and are spreadable on sandwiches, crackers etc. They are fabricated from finely comminuted mixes of lean and fatty animal tissues and liver. Because of the complexity of the raw materials used, these finely comminuted mixes are not true emulsions, hence the term "emulsion-like" is used. It appears that the fat particles in the mix are not equally and completely coated by protein, which would be the characteristic pattern of an emulsion. It is believed that part of the liver proteins in the comminuted batter form a protein network structure, where fat particles are embedded. Upon heat coagulation of the proteins the network becomes more rigid and the fat particles are held in place, as long as enough liver protein – in combination with salt and water – is available for network building. The subsequent cooling of the final products changes the consistency of the fats from liquid to firm and completely immobilizes them in the product. If fat separation did not take place during the heat treatment, it can no longer happen in the cooled product. It has been experimentally established that increasing fat contents from 10% to 40% in the finely comminuted mixes require increasing liver contents from 20% to 35% to avoid fat separation during cooking to a core temperature +74°C.

Fine emulsion-like liver sausage with course ingredients

Fig. 192: Fine liver sausage with coarse ingredients

In order to achieve this kind of product, coarse liver and/or meat particles of 2-6 mm size are added to the fine emulsion-like basic liver sausage mix. The liver particles can be added raw or cooked, the meat particles always cooked. The addition of the coarse ingredients takes place at the final stage of the fabrication of the fine emulsion-like mix (Fig. 192).

Fig. 193: Production diagram for liver sausages

Impact of heat treatment on product quality

Fine emulsion-like liver sausages without or with coarse ingredients are usually filled in natural or synthetic casings of medium diameter. They are cooked in a cooking vat or cooking chamber at around 78°C. At temperatures >84°C natural casings may break. The core temperature to be reached is 74°C. Products in plastic casings are rapidly cooled in cold running water. In tropical countries the use of ice water is recommended. Also emulsion-like liver sausages in natural casings are initially cooled down in cold water until a core temperature below +20 is achieved. They are then transferred to the cold room for completely cooling down. Smoking will be only done after the sausages have been chilled completely at a temperature not exceeding +20°C.

The three types of liver sausage (fine emulsion-like, partly coarse-mixed, fully coarse-mixed) are basically fabricated with the same raw materials and undergo similar heat treatments. The chopping methods applied are different which eventually lead to different textures and variations in appearance and taste in the final products.

Liver sausages and liver pate generally have a medium to high fat content, which is needed to achieve the desired spreadable products. However, sausages containing more than 45% fatty tissue give an extremely fatty impression in taste and appearance and may not be accepted by many consumers from the nutrition point of view (see also page 15). Moreover, fat may separate during heat treatment (see Fig. 194), which spoils product appearance. To avoid such failures, fat has to be reduced. A simple butcher trick is addition of water if the fine liver sausage batter appears to break (visible fat separation during chopping). Water seems to interfere in the emulsion-like structures with the result that fat gets more firmly bound and fat separation can be reduced. Products containing 30-40% fatty tissue (preferably pork jowls and bellies) have a pleasant meat-liver flavour. At high fat levels, care must always be taken to avoid fat separation. When adding less than 25% fatty tissue, products start getting dry but still have acceptable meat-liver flavour.

Fig. 194: Liver sausage with high fat content. Due to high fat content the sausage mix destabilizes during heat treatment resulting in fat separation (right)

The fine emulsion-like type (Fig. 196) is well suited for canned sterilized products, as the fat is embedded in a protein network structure derived from the liver proteins and will not easily separate during heat treatment even at high temperatures. Addition of milk proteins (2%) (see page 63, 69) also assists in keeping the mix stable during sterilization. The average liver content in finely comminuted products is 20%, which usually provides sufficient fat binding capacity. During sterilization fat separation may occur in products with 20% liver content. This can be solved by reducing the fat content. Also the coarse liver sausage mixes (Fig. 195) can be used for canned sterilized products. In these products fat separation, and possibly also jelly separation, is unavoidable and accepted by consumers.

Fresh liver contents in all sterilized liver products should not exceed 20%, because liver is very heat sensitive and higher contents would lead to unpleasant bitter taste. Similarly, fat contents in sterilized goods should be kept lower than in cooked (pasteurized) goods, as higher temperatures provoke more fat separation.

Fig. 195: Coarse liver sausage mix in glass jar (sterilized product)

Fig. 196: Emulsion-like liver pate in sealable plastic container (sterilized product)

Blood sausage / blood products (recipes page 420, 421)

Approx. 10 litres of blood are obtained from one bovine during slaughter and approx. 3 litres per pig. This blood with its 20% protein content is a valuable source of animal protein and is used in many parts of the world as a raw material for processed meat products. A large variety of food products have been developed which contain blood as one of the main components. During manufacture of these products, blood is mixed with other ingredients such as animal tissues of different origin, cereals, vegetables, salt and spices. For socio-cultural reasons there are some restrictions where blood is not used as food, for example in Halal products. In many developing countries blood is often wasted due to low-standard slaughter facilities and practices, although its consumption is permitted. Improvements in this field could significantly increase the collection and use of blood and contribute to an increased supply of valuable animal proteins to needy consumers.

Blood as a raw material

In principle, blood from all livestock can be used for the manufacture of blood food products. In most cases pig blood is preferred for further processed goods as it provides the best colour and taste, but also cattle blood can be a suitable raw material. Fresh blood with its high water content and pH over 7.0 (7.3-7.5) favours bacterial growth leading to spoilage and must be collected in the most hygienic way during slaughtering. It should either be used immediately or kept under refrigeration (below +3°C). In some instances, also blood from small ruminants and poultry is collected for human consumption and used for a variety of blood products. In the process of bleeding poultry, and small ruminants, contamination is more likely to occur than in pigs and cattle. Therefore special care has to be taken during collection and such blood should be treated immediately.

Fig. 197: Fresh, stirred blood

Fig. 198: Coagulated blood (not stirred)

Fig. 199: Fibrin, stirred out

Basic blood-based products

In East and South East Asia, blood collected at slaughter places is commonly used as an ingredient for soups and meat and vegetable dishes. In these cases the blood is allowed to coagulate immediately after bleeding. The viscous mass is cooked as soon as possible either in special blood pans or even in containers suspended in hot water. Through the cooking a great deal of the remaining liquid fraction of the blood is separated and the resulting solid product of dark brown to black colour is used as a food ingredient.

Blood sausages

Unlike the above simple application of blood, blood sausages are fabricated as mixtures of raw un-coagulated blood and other food ingredients (meat, fats and non-meat ingredients) filled into casings with subsequent heat treatment. For most of these blood sausages a firm to strong-elastic texture is required. Blood added in its liquid form is well suited to achieving such a texture. Blood coagulation during heat treatment of the mixes filled in casings, cans etc. contributes to a firm structure. These mixes must undergo heat treatment immediately after filling or portioning to make the final products palatable and safe from the hygienic point of view.

Blood to be used for this type of further processing must be kept liquid after collection at point of slaughter. This can simply be achieved by immediate intensive manual or mechanical stirring of the blood from the moment of collection in a container. This way, the blood protein fraction fibrinogen, which is an indispensable factor in the biological blood clotting reaction for stopping the blood flow in wounds, is transformed into fibrin and separated as solid fibrin fibres. As a result, the remaining blood stays liquid (Fig. 197, 198, 199). Another way of preventing blood from coagulating is the addition of anticoagulant chemicals (2% sodium citrate or sodium phosphate solutions). The advantage of using anticoagulants is that the protein substance fibrinogen is not converted into fibrin and remains integrated in the blood as a valuable liquid protein fraction.

Traditional blood sausages

These products have a blood content of between 5-30 % and also contain precooked materials such as cheaper meat parts, often with high collagen content and edible slaughter by-products such as kidneys and spleen.

In one type of traditional blood sausages, only blood and precooked edible carcass parts such as pork skin, head meat and meat derived from cooked bones are used. No non-meat ingredients/meat extenders are added except common salt and dried herbs and spices for flavour improvement. All components for the product are mixed together, ground to the desired size in a meat grinder, filled into natural casings and subjected to heat treatment. The natural casings may derive from the slaughter animal. One typical example for this group of blood sausages is the South American Morcilla (see page 219), which is popular for traditional BBQ’s. In English speaking countries traditional blood sausages are known as Black Pudding (Fig. 201).

Other local variations of blood sausages have been developed over the centuries using low-cost raw materials of plant origin such as cereals and/or vegetables as ingredients (Fig. 202) replacing the more expensive meat. In some Asian countries a mixture of blood, flour, cooked pieces of pig feet and spices is stuffed into casings and fried before consumption. In Ireland the black pudding contains oats. In Southern Germany farm blood sausages (Fig. 202) can contain a mixture of roasted bread and onions. In a product found in East Africa the blood is mixed with fermented milk and sometimes with ground cassava and other vegetables.

Fig. 200: Typical blood sausage composition

Precooked meat trimmings with high collagen content (left), fresh (raw) blood (right), onions and garlic (centre)

Mixing of precooked materials with fresh blood and extenders before mincing

Fig. 201: Black pudding

Central European blood sausages

Blood sausage varieties in Central Europe (Fig. 202 centre) usually contain 10 to 20% blood, pork skin, lean meat and back fat. All meat raw materials used in the manufacture are previously cooked, with the exception of fatty tissues, which are only briefly scalded, and of course the blood, which is always added raw (uncooked) (Fig. 200). While the traditional blood sausages contain common salt and are dark brown to black in colour, modern Central European blood sausages are known for their bright red shiny colour. This appearance together with a typical flavour is best achieved by using pig blood. The red colour is obtained by adding nitrite curing salt to the blood.

The blood is usually pre-salted with nitrite curing salt immediately after collection, which is the traditional method to achieve an attractive red colour in the final product. Pre-salting also has the advantage of presenting a significant hurdle for bacterial growth in the fresh blood during storage under refrigeration. Care must be taken that the pre-salted blood is not added to the precooked materials at temperatures above +45°C, as this could destabilize the curing reaction. Curing enhancing substances such as ascorbic acid should only be added at the end of the mixing process as this supports the formation of a stable red colour. Recent studies suggest that the utilization of fresh unsalted blood in blood sausage manufacture and addition of nitrite curing salt in the final stages of the mixing process, can still lead to a shiny red colour in the final product.

In order to create the desired firm-elastic texture in the final products, the liquid blood is mixed with precooked pork skin, which is rich (up to 30%) in connective tissue/collagen and has a strong gel-forming capacity. Pork skin should be fat-free and preferably from younger animals, as they have softer and more elastic skin. The blood/pork skin mix, usually in a proportion of 1:2, is the basic matrix for this type of blood sausage. In small-scale manufacturing a meat grinder can be sufficient to prepare the matrix. In this case the precooked pork skin is mixed with the pre-salted blood and minced through the 3mm disc. The use of a bowl cutter has the advantage that the precooked pork skin and raw blood can be intensively chopped, which results in a very homogenous blood/skin-mixture. In practice, before starting the chopping, the hot precooked pork skin (+65°C) is coarsely minced, transferred into the cutter bowl and chopped with some hot meat soup (fat-free liquid remaining from pre-cooking). As soon as a temperature below +45°C is reached, the blood is incorporated and the chopping process completed. The temperature of the final mix should be between +30 and +40°C.

Fig. 202: Blood sausage mix in natural casings: Traditional blood-cereal mix (left), European blood sausage (centre), farm-style blood sausages (right)

These blood/pork skin mixes are combined with portions of precooked coarse meat and fat particles. Precooked lean meat pieces (mostly cured prior to cooking to achieve an attractive red colour) are cut into cubes or stripes. The raw fatty tissue is diced (<5mm) and briefly scalded in hot water (+95°C) to remove greasy layers from the surface and harden the connective tissue structure inside the dices. This will prevent grease extraction during cooking as well as blood infiltration. Lean meat particles are rinsed with hot water in order to remove all greasy surface layers and to achieve good binding with the blood/pork skin mix. The meat pieces and fat dices are mixed with spices and some salt and incorporated in the blood/pork skin mix. After filling into casings (for attractive presentation larger calibre natural casings are preferred over synthetic casings) (Fig. 202, 203). The products are cooked at <84°C to avoid casing rupture. Core temperatures of +75°C are recommended for sufficient microbial stability. Due to their firm-elastic texture the chilled products can easily be sliced and are mainly consumed cold. Blood sausage mixes can also be sterilized resulting in shelf-stable products (Fig. 204).

Fig. 203: Blood sausage (above) and gelatinous meat mix in synthetic casings

Fig. 204: Blood sausage (right) and gelatinous meat mix (left), sterilized in glass jars

Cooked gelatinous meat mixes

The low-cost variety of this cooked meat/by-product specialty uses high-collagen meat sources similar to the collagen-rich mixtures of ingredients as used for blood sausages, but without adding blood (Fig. 203, 204). These products usually contain higher amounts of head trimmings (including skins, snouts and pork under-lips), veal and pork feet, tongues and other animal tissues according to local preferences. All raw materials are precooked to some degree, depending on the nature of each individual tissue. After cooking, they are cut into small pieces or ground, salted and seasoned. The uniformly blended mixes are filled in casings of larger diameters (natural or synthetic) and subsequently cooked. As natural casings only endure cooking temperatures of up to +84°C, but on the other hand the core temperatures should be in the range of +74°C, cooking times in large casings are relatively long. As a rule of the thumb, one minute cooking time should be considered per one mm diameter.

Fig. 205: Low cost product (mainly pig head meat) filled in pig stomach

Fig. 206: High quality product (lean cured ham pieces in jelly) in synthetic casing

The characteristic of the ready-to-eat products is the gelatinous texture (Fig. 205, 206). The jelly, which holds the mix together, is derived from the collagen-rich raw materials used. Cooking such tissues releases and solubilizes part of the collagen, which solidifies upon cooling of the products. Moreover, the jelly-rich water, in which the individual raw materials were cooked, is a valuable ingredient to improve the binding properties and the flavour of the products. For this reason, the jelly-rich water is concentrated by boiling and added to the mixes in this form.

High quality variations of gelatinous meat mixes are also on the market and contain larger portions of lean meat. Some of them even fulfil the criteria of dietary meat products with low fat content (less than 10%). The lean meat is usually first treated with nitrite curing salt for an attractive red colour and later precooked. The precooked meat pieces are diced and rinsed with hot water to remove all smaller particles and fatty layers, which would limit the binding of the final mix (Fig. 206).

The lean meat used for this high-quality variety does not contain sufficient collagen to produce the required jelly. In some more traditional products, ground precooked pork skin is used as a collagen source, but provides a turbid jelly. In order to achieve the desired “elastic” gelatinous structure and obtain a clear appearance of the jelly, in industrial applications gelatine powder, dissolved in hot potable water is used, replacing the precooked ground pork skin. In some recipes pieces of vegetables (e.g. carrots) are added, which are embedded in the gelatinous matrix in a similar way as the meat pieces and provide an attractive product appearance.

Cereal sausage

For this type of precooked-cooked sausages sizeable quantities of various non-meat ingredients such as breadcrumbs, rusk (flours mixed with water, baked and crushed), rice, sweet and Irish potatoes, cassava, plantain, etc. are used (see page 64, 78, 81). With the exception of breadcrumbs or rusk, all other plant ingredients are precooked. They are incorporated into a basic mixture of pre-cooked lower value animal parts deriving from animal heads and feet, bone scraps and any other edible tissues. Also liver or blood may be added thus making those cereal sausages to some extent similar to either the liver or blood sausage variety.

Cereal sausages in Europe originate from a time when meat as a raw material for sausage production was relatively expensive and hardly affordable by the bulk of the population. Hence products were created with cereals mostly combined with edible slaughter by-products to keep the cost low (Fig. 207). From poor peoples’ food some of these products have now become local delicacies and achieve relatively high prices. They are also seen as contributing to more balanced diets, if they are low in fat and high in fibre.

Fig. 207: Cereal sausage

Nevertheless, for developing countries with population segments who may find it difficult to afford expensive meat products, these traditional formulas offer a good opportunity to provide access to and increase consumption of animal proteins at low cost for all. The methods of production are simple. Meat/cereal mixes are prepared similar to the usual methods for low-cost cooked gelatinous meat mixes. If blood or liver is used, all these ingredients are usually added precooked, unlike the technology used for blood or liver sausages where blood and liver are mostly used raw (see page 150).

Corned beef varieties (recipes page 415 – 417)

Corned beef with jelly

Corned beef with jelly is produced from cured pre-cooked beef. The pre-cooked lean beef should be shredded in order to maintain the fibrous structure of the muscle tissue to some extent. This shredding is done in bowl cutters with a specific shredding device in the form of blunt knives. Cutter knives fitted in the reverse way to avoid sharp cutting of the tissues and operated in slow gear can also serve for this purpose.

Typically for corned beef with jelly a certain quantity of liquid, which is usually the cooking broth of the lean meat, is added to the shredded lean meat. This cooking broth may have been concentrated by boiling or enriched with gelatine. Normally only the quantity equivalent to the loss of meat juice is replaced that had been cooked out during the precooking of the raw meat.

Before adding the liquid, the shredded precooked beef is mixed with spices and additives. The aim is to achieve a juicy soft texture of the final product. For this purpose, the mix is filled either in synthetic casings (Fig. 208) and pasteurized (cooked below +100°C to core temperatures of +74°C) or filled in cans and sterilized (Fig. 209) (e.g. as fully preserved products, see page 288).

There are high quality products on the market with lean beef only as raw material (Fig. 208, 209). For lower price products beef or buffalo meat trimmings are used with higher fat and connective tissue content, some also contain meat extenders (red coloured TVP, approx. 5%) (Fig. 105, 211, 212).

Fig. 208: Corned beef with jelly, in casing (Europe)

Fig. 209: Corned beef with jelly (high amounts of jelly)

Classical Corned beef

The classical corned beef was originally a by-product of meat extract production. More than one century ago, before refrigeration was available, the only way of utilizing the surplus beef from Latin-America and other regions of the Southern hemisphere for shipments to Europe, was to produce meat extract. Meat extract is a viscose concentrated protein-mineral paste obtained by evaporating the process water (cooking broth) of beef. Meat extract is shelf-stable and can be shipped over long periods at ambient temperatures. It is a useful ingredient for seasoning and protein enrichment of meat dishes.

Fig. 210: Classical corned beef in typically shaped cans. Right: open can showing product

The remaining product of the meat extract production was the cooked beef, where part of the proteins and minerals had been extracted, but which still was a valuable food in terms of protein content. With the development of the food canning technology, this cooked beef was filled into cans and heat sterilized. The result is the classical corned beef. Thus, besides the meat extract, another shelf-stable and attractive meat product was obtained, that could also be shipped without refrigeration to consumers in Europe. Canned classical corned beef is still a popular product worldwide.

The manufacture of classical corned beef is simple. The raw material is lean beef of lower grades, usually from cows. In industrial plants the precooking of the beef takes place in continuous cooking lines. Visible connective and fatty tissue is separated from the precooked beef. The remaining lean precooked meat is mixed with spices and curing salt and coarsely minced. This mix is filled into the typically shaped corned beef cans (Fig. 210, 211) and sterilized. The product quality is not significantly affected by high temperatures, hence the sterilized products, for safety reasons (long transport and storage at high temperatures!) should reach F-values of 12. F-value is the measurement for the intensity of the heat sterilization (see chapter “Canning” page 289).

There is one interesting feature in the manufacture of classical Corned beef. In industrial corned beef lines it is not possible to treat the raw beef with curing substances before cooking, as it would interfere in the meat extract production. Nitrite curing salt is only added to the final precooked mix before filling it in cans, and one would expect a grey product after sterilization. Nevertheless, the final products achieve a slight pink colour. Obviously there is still some myoglobin available that was not destroyed by the precooking and reacts with the nitrite.

Fig. 211: Classical corned beef (left) and low cost corned beef (right)

Fig. 212: Low cost corned beef upon removal from the can

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