Figure: Production diagram of sausage Process flow for production of sausage Chopping Grinding Mixing Emulsifying Stuffing Linking and tying Smoking and cooking Chilling Packaging

Ingredients Raw materials depends on 2 factors Classical raw-cooked product Products of relatively high quality and good nutritional value as they contain meat and fat as the main components and water as the major non-meat ingredient. Ingredients of plant origin, used in small quantities and do not serve as an extender but as binders, e.g. soy isolate (approx. 2% added) Extended raw-cooked meat products inferior quality as they contain higher quantities of extenders and fillers of plant origin contain higher amounts of low-cost non-meat ingredients mostly of plant origin for cost- reduction Examples are hotdogs and luncheon meat

Lean meat is the principle raw material for classical raw-cooked meat products. It provides the muscle proteins, which play an important role in the processing technology of raw-cooked products. The lean meat component comprises mainly chilled beef and/or pork, but also poultry meat (turkey, chicken) is becoming increasingly popular for this purpose. Other meats like mutton and venison are less suitable and not commonly used. The same applies to muscular slaughter by-products such as heart, diaphragm and oesophagus. Lean meat is used in quantities of 30-50% referred to the overall amount of batter for raw- cooked products The lean meat should have a relatively high pH, preferably in the range of , as such meat has a better water binding (also called water holding) capacity (WBC/WHC) 1) Meat

Figure: Canned product with separation of jelly and fat Good WBC is important to bind the amount of up to 30% of water, which is usually added to the batter to improve texture and palatability of the final products. Moreover, the lean meat itself has a water content of 70%, which also must be kept bound. The binding of all this water must remain stable in the sausage mix also during heat treatment, which is the hardest challenge for the water retention capacity. Low WBC results in loss of liquid during cooking visible as an accumulation of jelly under the sausage casing, inside cans etc.

2) Fat Fat, mainly chilled pork fat, but also chicken, beef or lamb fat or vegetable oil, is used in quantities of 15-30%. fat content in the final product should not exceed 25%, as otherwise the shrinkage by melting fat during frying or cooking would be high Not all animal fats are suitable for this purpose, as some would make the batter too “grainy” (kidney fat) and others too soft (intestinal fat). Back, belly (pork), skin (poultry) and to some extend intermuscular fat (beef) are suitable. Function of fat-make products softer and more palatable and support desirable flavour. In order to achieve a good quality product with typical taste and texture, preferably fresh chilled fats should be used Fats from long cold storage, in particular frozen fats, are less suitable, as they tend to become rancid. Fats should be free of hard connective tissue. The chilled fats are pre-minced (3mm grinder plate) for good immediate distribution in the batter. If vegetable oil is used instead of animal fats, this oil should be chilled but must remain liquid or viscous.

3) Water Water is added in quantities of approximately 15-35%. It makes products juicy and easily chewable. Water is not primarily used as “filler” in raw/cooked meat products. It is absolutely necessary as a carrier and solvent for the muscle proteins. Water together with salt and phosphates, which enforce the process, is indispensable for the desired extraction and water binding of the muscle proteins As the protein extraction is best under low temperatures, water is often added frozen as ice to keep the temperature of the meat batter low. Low temperatures are also needed to avoid excessive rise of temperature in the area close to the fast rotating bowl chopper knives. Excessive temperatures there would spoil the ability of affected proteins in water binding and gelation. For quick and even distribution (in order to achieve an instant cooling effect in all parts of the chopping bowl), small-size ice flakes should be used or ice blocks should be crushed into small pieces before being added to the batter.

4) Additives Additives and spices (salt, phosphates, ascorbic acid, various ground spices) are used in dry-powder form and must be stored in a cool and dry place in closed containers and frequently checked for impurities. Used in smaller quantities and need to be accurately weighed to avoid under or overdosage. Salt and/or nitrite curing salt serve for salty flavour, solution of muscle proteins and curing colour. Approximately 2% is normally applied Phosphates assist in solubilizing muscle proteins. Approximately 0.3% is normally used Ascorbic acid acts as a catalyst in the curing process. Approximately 0.05 – 0.1% is normally used

Additional measures for proper cohesiveness and water binding The protein network in the final batter will be the more complete and functional as more meat protein is used in the mixture. To further facilitate the formation of the protein network, where the meat content is low, the following measures can be taken: Addition of small amounts of proteins (approx. 2% of dry substance) mainly originating from soy beans (isolated soy protein, ISP), Texturised Vegetable Protein (TVP) or derived from milk (milk protein, caseinate) or blood (plasma protein) can be added. They increase the amount of available proteins resulting in more comprehensive protein network structures

Stuffing Figure: Air pockets caused by loose stuffing. Discoloration caused by enclosed air. Above right tightly stuffed, no discoloration The mixture is usually stuffed into thin or medium size calibre natural casings of the “edible” type Originally, derived from the small intestines of pigs or sheep, are either freshly prepared from local slaughter, or salted and stored until used. Need to be rinsed with sufficient quantity of clean water prior used for stuffing The casings are filled almost to their maximum capacity and thereafter divided into shorter units of the desired size by linking and twisting Replaced by edible collagen casings or cellulose casings of similar diameter. This allows for better standardisation of sausages and larger volumes of production

Fresh sausages are highly perishable products and subject to fast microbial spoilage and oxidative rancidity. Should be heat-treated and consumed as soon as possible after production, or must be stored immediately under refrigeration. Maximum storage life is normally three days at +4°C or below. If deep-frozen at - 18°C, the storage life can be extended up to three months. One difficulty associated with frozen storage is the oxidative rancidity. Storage in vacuum bags can prevent the fast onset of rancidity. Storage and preparation for consumption

Principles of sausage manufacturing 1)Extract and dissolve solid muscle proteins through physical (chopping) and chemical (salting) treatment of lean meat and blending with water Fig: Condition after dry chopping. Muscle fibre fragments (red) and connective tissue particles (green) present in mix Fig.: Condition after adding salt and water. Most muscle fibre fragments swell through water incorporation (blue) and become gelatinous or solubilized (b), some muscle fibre fragments (a) and connective tissue particles (green) remain unchanged. Water droplets may also be loosely bound between the fragments (blue) (c)

2)Establish a network structure of liquid or gelatinous muscle proteins in the meat batter capable of surrounding and enclosing small particles of fat and binding water. Fig: Condition after comminuting and addition of fat. Network structure of gelatinous (b) or liquid (d) muscle fibre proteins (dark red areas) established, fat particles (yellow) coated by protein (bright red). Connective tissue (green) and some muscle fibre fragments (a) unchanged. Water droplets (blue, c) incorporated in protein network

3)Stabilise the muscle protein network through heat coagulation by “cooking”. Core temperature of products should be not lower than 70°-72°C. Fig.: Condition after heat treatment: Protein network structure becomes rigid and firm elastic (purple areas) through protein coagulation/denaturation. Connective tissue particles (green) swell in size and become softer, may interlink (arrows) if large amounts present

4)Cool products down through immersion in cold water or cold water spray immediately after cooking, pass quickly temperature range from +40°C - +20°C, store in refrigerated rooms Fig.: Cooling in ice water (+5°C) of sausages of different calibre (20 mm, 40 mm, 75 mm). Decrease in core temperature depends on calibre of sausage and temperature of cooling water