In view of the above, smoking in order to preserve meat can only be considered as an emergency measure when no other preservation methods can be carried out. This may be the case during wet weather or generally under a humid climate, or when the preservation has to be completed as fast as possible because of the need of immediate transport, for instance after game-hunting.
Intensive meat smoking is always a combination of two effects, drying the meat by reducing its moisture content through hot air and the condensation of smoke particles on the meat surface together with their penetration into the inner layers of the product. Both have preservative effects and prolong the shelf-life of the product.
To smoke the meat, large strips and/or pieces, with and without bones, are dried by smoking in special drying/smoking places. The smoke is produced in these cases by glowing wood. Often, meat is prepared quickly by drying and smoking over a fire. In this case, the meat is not only smoked, but "half-cooked" or roasted. Normally, meat from this treatment is not well prepared and has to be consumed soon after drying, otherwise it will spoil quickly.
The quality of traditionally smoke-dried meat is generally poor. This is not only owing to poor meat quality or inadequate smoking devices, but mainly because smoke-drying is a rather rough treatment for the meat. The process is fast and has a certain preserving effect, but at the cost of quality.
Quality losses are even more obvious when failures in preparing the raw material occur. When, for example, the thickness of the meat parts to be smoked ranges from about 3 cm to 15 cm, uniform drying will not be achieved. The smaller pieces will be overdried and the thicker ones may still remain with a high moisture content in the product centre. The results of faulty drying and smoking are a too strong smoke flavour, lack of rehydration capacity of the smaller parts and fast spoilage of the thicker parts. For effective smoke-drying, the meat thickness should not exceed 7 cm to achieve products which are stable for a certain period without refrigeration.
Apart from primitive smoking places with just a fire below the meat, the construction of special smoking kilns has been suggested for smoke-drying of meat.
The effect of light smoking could be of interest for the production of dried meat. Light smoking is not suitable for meat preservation without a cold chain, but it adds a smoke flavour to the product and inhibits the growth of moulds and yeasts on the product's surface owing to the fungistatic smoke compounds. Thus light smoking may be used for the prevention of growth of moulds during the storage period of dried meat, especially under humid climatic conditions.
MEAT PRODUCTS SUITABLE FOR CANNING
Basically all meat products which require heat treatment to prepare them for consumption are also suitable for heat preservation. Only meat products which do not receive any form of heat treatment before being consumed, such as dried meat, raw hams or dry sausages, are naturally not suitable for canning. These products are conserved by a low pH value and/or low water activity.
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The following groups of meat products, when not consumed freshly cooked, are frequently found as canned products:
cooked ham
sausages with brine of the frankfurter type
sausage mix of the bologna or liver sausage type
meat preparations such as corned beef, chopped pork, etc.
ready-to-eat dishes with meat ingredients such as beef in gravy, chicken with rice, etc.
soups with meat ingredients such as chicken soup, oxtail soup, etc.
Raw and dry sausages
Germany, more than any other country, has influenced the production of sausage throughout the world. The industry in Germany has developed a system of classifying sausages. In principle, this classification is based on the temperature treatment of either the final product or the raw materials.
Most cooked sausages consist of fine-meat emulsion, but many combinations are made with either semi-coarse lean or semi-coarse fat and with both. Among the salamis, combinations of semi-coarse lean and fat and coarse-lean and fat are seen. Many similar kinds of sausage have different names. The terminology of sausage is rather complex as the system of naming is based on association with localities, special occasions, sensory perception, etc.
The main equipment for raw and dry sausage production consists of the mincer and/or bowl chopper, vacuum mixer, stuffer, climate chamber and, in a number of cases, the smokehouse. In bigger operations the vacuum chopper is gaming popularity. In Italy and in some parts of eastern Europe the mincer is the exclusive machine for comminution. In most other countries, and particularly for those factories using deboned frozen meat, the bowl chopper is applied. In some cases, part of the lean meat is minced and blended with the balance of the chopped meat and the fat, either at low speed in the bowl chopper or in a vacuum mixer, to achieve a better binding and coherence.
The sausage mix may be stuffed at a lower temperature than was formerly used. The fast continuous stuffers must have a low temperature ( 4C) to prevent smearing. In some factories, the stuffed sausages are hung overnight in a cool place (510C) to avoid a too rapid change in temperature before they are transferred to the fermentation chamber. Stuffing is done in natural, artificial and collagen casings.
Raw sausages like Mettwurst and Teewurst are fermented in airy rooms for the formation of a stable color and then smoked to the desired color and taste. Generally, coarse products such as some types of Mettwurst are cold smoked, whereas very fine and spreadable sausage such as Teewurst are warm smoked.
For dry sausage production on a large scale, mincing, blending and stuffingare performed continuously. After blending, the sausage mix is automatically transferred by a plunger into stainless steel cylinders which are transported by rail and automatically fitted to the stuffers.
Fermentation, drying and smoking are done at temperatures between 12 and 15C during times ranging from weeks to several months. Fermentation is performed at temperatures between 20 and 25C and relative humidity (RH) of 9295%. The subsequent smoking and drying are done at temperatures preferentially below 20C and gradually decreasing RH down to about 78%. This method takes from 5 days to 3 weeks. Limited amounts of glucono delta lactone (GDL) are used to acidify the product. However, starter cultures are more frequently used.
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Fresh sausages, such as pork and beef sausages, are raw items and not fermented. As far as Europe is concerned, their production is limited to the United Kingdom. They are made in the bowl chopper at temperatures not exceeding 5C, stuffed into medium hog casing, wrapped in plastic film, distributed under refrigeration and fried by the consumer. Some types of fresh sausage are artificially colored by using pink rusk. Bratwurst, which is quite popular in Austria, Switzerland, Germany and the Scandinavian countries (known as Medister), was originally a fresh sausage. At present, however, most Bratwurst is cooked by the manufacturer.
The raw materials normally used are either lean pork or beef or a combination thereof, and hard pork fat, mostly pork-back fat. The use of mutton is rare. In Scandinavian countries, excellent dry sausages are produced from reindeer meat. For cheaper types of dry sausage, hearts, rinds and, in some cases, rind emulsions are used. Formulations range between 30-50 % fat.
For fresh sausage the main ingredients are either lean pork or beef and pork fat, and a relatively high percentage of extenders. Rusk, flour, skimmed milk powder, soy isolate and concentrate, milk proteins and dextrins are used in countries where extenders are permitted. Normal additives are salt, nitrate, nitrite, polyphosphates, ascorbic acid, mono and diglycerides of fatty acids derived from animal fat, dextrose, malto dextrins, sucrose and lactose. Wine is used in some special types of salami.
The most popular spices are pepper, paprika, mace, garlic, cardamom and cloves. For fresh sausage production, soaked bread, cooked rice and potatoes have been used. At present, rusk and some starch are more frequently applied. Amounts up to 10 % or higher of these ingredients are not unusual.
Sausage made with cooked ingredients
On the European continent most liver-and-blood sausage is made of precooked fat, meat, rinds, tripe and stomachs. Liver is not precooked. In the United Kingdom the use of precooked ingredients is not common practice.
On the continent, liver is chopped with a part of the salt and curing ingredients. After some chopping, bubbles begin to form and precooked fat and broth are introduced as this time. Chopping is continued until the desired fineness is almost achieved. Then the balance of the salt and spices is added. At a temperature between 35 and 50C, the sausage mix may be stuffed as a fine liver sausage or used as a base for other liver sausage. By chopping in precooked meat, or mixing in pieces of cooked meat, fat or liver, many different types of liver sausage are made.
For liver sausage containing a certain amount of broth, water in which fat and the other ingredients are precooked is used as the broth. Both broth and fat are brought in the bowl chopper, where the fat is emulsified by means of sodium caseinate. The prechopped liver is then added to the emulsion, and after a short chopping the sausage mix is ready. The liver may also be minced and added to the emulsion. Finally, the mixture is passed through a mill. This method is convenient and allows more recipe variation than the conventional process. More stable products are obtained for high temperature baking or canning. This technique is used for the incorporation of fresh fat in the United Kingdom.
Sausages are stuffed either in natural or artificial casings. For some types of liver sausage a fat lining may be applied in artificial casings or molds.
Fat, meat and rinds are precooked for use in blood sausage. The blood is cured with salt, nitrite and either citrate or phosphate to prevent clotting. Precured and aerated blood results in sausage with a pink color. Otherwise, the sausage becomes black on cooking. The pretreated blood is warmed and chopped with the rinds, and, in some types, with precooked meat or cubed fat. During cooking and cooling, sausages are turned to achieve an even distribution of cubes. Large casings, hog stomachs and molds are utilized.
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Jellied products are made with either pure gelatin or cooked rinds as the gelatin base. Cooked rinds are finely ground and sifted after cooking at about 80C. For improved flavor and gelatin strength, vinegar or white wine may be added. The cubes of meat and the fat are cooked, precured if a pink color is wanted, then mixed with the rind jelly and seasoning. The product is then stuffed into casings or hog stomachs, cooked and cooled. According to another technique, the product is cooked once more and hot filled into clean molds and then chilled.
Liver sausage may consist of a 50:50 liver-to-fat ratio plus seasoning, down to as little as 15% liver with 30% broth, 35% fat, some cooked rinds and extenders. The product ranges from spreadable to sliceable, depending on the amounts and proportions of meat, collagen and binders. Other variations are created by adding coarse meat, liver and pieces of fat to the fine sausage emulsion. The degree of fineness of the meat and fat ingredients, as well as the seasoning, determines the type of liver sausage.
Ingredients for blood sausage include blood and cooked rinds as well as cubed fat, tongue, kidney and pork belly. For cheaper types, tripe, lungs and stomachs may be used.
For jellied products the principal raw materials are rinds, gelatin, lean meat trimmings, pigs foot, calves foot, defatted head meat, firm fat tissue and, in some cases, hearts.
For liver sausage the following extenders are used: sodium caseinate, skimmed milk powder, wheat flour, soy protein concentrate, soy protein isolate and some potato starch. Egg white, whole egg and blood plasma are occasionally used in liver sausage.
The most popular spices for liver sausage are pepper, nutmeg, marjoram, mace, pimento, cloves, ginger, cardamom, cinnamon, onions, shallots, truffles and pistachios.
Cereals such as barley and rye flour are used in blood sausage. The most prevalent spices in blood sausage are pepper, marjoram, cloves, pimento, thyme, cinnamon, ginger, onions and coriander.
In jellied products, flavorings utilized are pepper, pimento, marjoram, ginger, cloves, kummel, celery, bay leaf, vinegar and white wine.
Sausage cooked after formulation
The mincer, bowl chopper, vacuum mixer, blender, mill and stuffer are the machines most used. Small quantities are manufactured in batches, while large quantities are prepared semi-continuously. The preblending system is gaining popularity in Europe. Although originally a means to obtain uniform raw material, the combination of mincer, preblender, mill and stuffer now provides a more or less continuous production system. For critical products the conventional chopper mixer stuffer process is preferred. Many types of casings are used, but in central Europe many small sausages are produced in natural casings.
Pork and beef are the most popular meat ingredients, with limited use of mutton, horse and poultry. Variety meats such as hearts, diaphragm, tripe, pork skin, stomachs, etc. are allowed in most countries, although not in every product. In some countries, sausage products are divided in two or three quality categories. For each of them the raw materials which can be used are defined. Mechanically deboned meat is used in an increasing number of countries. In some countries the amounts are limited by law, in other countries by technological or sensoric considerations.
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The use of all adipose tissue in any form is allowed: as whole cuts, such as pork bellies, or as fat trimmings. The successful production of cooked sausage depends, among other things, on the type of fat used. Firm adipose tissue such as pork-back fat, belly fat, jowl and ham fat are preferred for different applications. The European sausage manufacturers use all kinds of fat in any cooked sausage which is not the case in the American meat industry. Europeans produce stable cooked sausage of good quality with any type of animal fat by pre-emulsifying the fat in water by means of a non-meat protein such as soy or milk. This process became known and popular about 20 years ago and is still widely used today.
In many factories, all kinds of fat trimmings and other fatty tissue are emulsified. The fresh or chilled fat is chopped, the casemate is added, followed by the addition of boiling water. After 46 min chopping, 1.52 % salt is added. After another minute of chopping, the emulsion is taken out of the chopper and chilled. After chilling, the emulsion can be incorporated in almost any type of cooked sausage. For optimal emulsion stability, chopping time and emulsion temperature are of great importance. For some purposes, emulsification can be performed with the use of cold water; or the hot emulsion, made with a part of the water, may be cooled with the balance made up by ice. This method is used for cooked meat sausage and loaves and enables direct incorporation of the emulsion into the sausage mix.
About one-third of the total fat in the formula can be used in pre-emulsified form. This method provides better fat and water binding, greater heat stability, an absence of any greasy taste and a production process which is considerably less sensitive to chopping time and emulsion temperature.
The legal regulations have a great influence on the ingredients of the sausage. Where the authorities are generous with respect to added water but forbid most of the extenders and polyphosphate, sausage making still is an art and recipe variations are limited. When the use of connective tissue is restricted, the sausage products are of excellent quality but also expensive.
Where added water is forbidden, the possibilities of producing a good quality sausage are rather low and the manufacture of lower-priced sausage necessitates the extensive use of collagen-rich material, often combined with a high fat content.
Most of the extenders used are starches and flours (potato, corn, wheat), milk proteins (sodium caseinate), skimmed milk powder, soy products (isolate and concentrate), wheat gluten, egg white, and blood plasma, either frozen or dried.
Other additives used are water, salt, phosphates, citrates, ascorbic acid, nitrate, nitrite, monosodium glutamate, glucono delta lactone, dextrose, malto dextrin, lactose and smoke concentrates. The most popular spices are pepper, nutmeg, coriander, ginger, mace, cardamom, paprika and garlic.
HOMOGENIZATION
For the manufacture of several milk products (ice cream, condensed milk, etc.) normal cream-line milk should be homogenized, that is treated under pressure to reduce the size and increase the number of tiny fat globules.
Homogenization is accomplished by subjecting the milk being processed to such physical action that will result in a breaking-up of the large fat globules into ones of smaller size. The pressure necessary to bring about homogenization is developed by pumping the milk through a restricted outlet, which may be a well-sealed valve or a series of small plates held at close proximity.
Homogenization increases the number of fat globules and the amount of fat surface. Homogenization destroys practically all tendencies for fat to rise or to cluster. Thus, the fat emulsion is almost stable: no cream forms and it is nearly impossible to separate it or to churn it. Homogenized milk is uniform in fat content.
Homogenization thus causes considerable changes in the fat dispersion. Other parts of the milk may also undergo changes, particularly the casein micelles. Homogenization induces profound changes in structure and in several properties of the products.
The effect of homogenization on clumping is sometimes useful: homogenizing ice-cream mix to prevent excessive churning during freezing; avoiding free fat in dried milk. But homogenization may also be harmful: impaired churning or whipping properties of homogenized cream; poor separation of fat from homogenized milk.
Homogenized milk does not readily develop the oxidized flavor so common in unhomogenized milk. However, care must be taken to avoid rancid and sunlight flavor defects. Homogenized milk is more quickly affected by sunlight than regular milk.
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EVAPORATION OF MILK
The removal of water from foods provides microbiological stability, reduces deteriorative chemical reactions, and reduces transportation and storage costs. Besides, the addition of sugar or sterilization of the finished product increases its keeping quality to several months. This makes it possible to use these milk products under conditions, which would make the use of the liquid milk impossible. Different kinds of concentrated milk are used for household application or for feeding infants, or for manufacturing purposes by bakeries, confectioneries and ice-cream factories. Both evaporation and dehydration are methods used in the dairy industry for this purpose.
Evaporation refers to the process of heating liquid to the boiling point to remove water as vapor. Because milk is heat sensitive, heat damage can be minimized by evaporation under vacuum to reduce the boiling point. The basic components of this process consist of heat exchanger, vacuum, vapor separator, and condenser.
The heat exchanger is enclosed in a large chamber and transfers heat from the heating medium, usually low-pressure steam, to the milk usually via indirect contact surfaces. The vacuum keeps the product temperature low and the difference in temperature high. The vapor separator removes entrained solids from the vapors, channeling solids back to the heat exchanger and the vapors out to the condenser. It is sometimes a part of the actual heat exchanger, especially in older vacuum pans, but more likely a separate unit in newer installation. The condenser condenses the vapors from inside the heat exchanger and may act as the vacuum source.
The driving force for heat transfer is the difference in temperature between the steam in the coils and the milk in the pan. The steam is produced in large boilers, generally tube and chest heat exchangers. The steam temperature is a function of the steam pressure. Water boils at 100C at 1 atm., but at other pressures the boiling point changes. At its boiling point, the steam condenses in the coils and gives up its latent heat. If the steam temperature is too high, burn-on/fouling increases so there are limits to how high steam temperature can go. The milk is also at its boiling point. The boiling point can be elevated with an increase in solute concentration.
DIFFERENT TYPES OF CULTURED
MILK PRODUCTS
Before the revolution in bacteriology in the middle of this century the manufacture of different types of cultured milk products was confined to common house-keeping and often regarded as a real art surrounded by a lot of mystery and superstition.
Today, modern dairy equipment, skilled labour and the availability of starter cultures in pure cultivation make it possible to produce all the different types of cultured milk products, regardless of climatic and local conditions, with the result that an increasing variety of different fermented milks is offered to consumers in most countries.
One of the best methods of preserving milk is the common process of souring, or culturing. All fermented milks such as kefir, koumiss, yogurt, buttermilk, acidophilus milk are the result of an acid fermentation in which the sugar of the milk is split up into lactic acid. According to kind and temperature of fermentation different taste and flavor substances are produced by the microorganisms involved.
Fermented (cultured) milk is a nutritious refreshing and easily digestible food. The protein precipitate in them is in the form of a fine curd which may permit them to be digested more quickly than plain milk.
Characterization of the different types of cultured milk products may be done in many ways, such as regarding bacteriological composition, flavour, composition of the product with respect to fat, solids-not-fat, different types of additives and many others.
The different types of cultured milk are grouped according to the physical structure of the coagulum and the types of micro-organisms used in the manufacture. Within each group, examples are given of typical products belonging to the group.
To these products could be added products such as cottage cheese and quark, but these products are usually regarded as special of cheese.
Lactic acid inhibits the putrefactive and protein decomposing bacteria in the intestinal tract, and that is why cultured milk is often used for treating several gastric and intestinal troubles, and koumiss is known to be a therapeutic agent in the treatment of tuberculosis.
The different cultured milk beverages are produced by subjecting the fermented and cooled coagulum to a heavy mechanical treatment usually carried out using a piston homogenizer.
Fermented milk beverages may be flavoured and they are usually stabilized to prevent sedimentation, and it is a question whether this product should be called cultured, because it consists of common market milk fortified by living Lb. acidophilus bacteria, which are added to the milk after it has been cooled.
KINDS OF CHEESE
There are lots of different kinds of cheese depending upon (a) whether made from whole milk or skim milk; (b) the method of coagulation of the milk; (c) the amount of whey retained in the curd; (d) whether the curd is ripened or unripened; (e) the method of ripening; and (f) the source of milk (cow, sheep, or goat).
Soft cheeses made from whole or from skim milk, which derive their flavor mainly from the lactic culture used and the cream added, are generally consumed while fresh. Hard or semi-hard cheeses are generally made from whole milk coagulated by rennet and are usually ripened or aged before they are consumed. Cheeses also differ according to the bacteriological or enzymatic treatment of the milk before coagulation or according to the addition of proteolytic and lipolytic mold cultures added to the curd before pressing.
According to the method of coagulation of casein cheeses are classified into two large general groups: rennet cheese and lactic acid (acidic) cheese, according to whether they are started by the rennet or lactic acid method.
According to the method of manufacture we distinguish: (1) uncured, or unripened cheese (the Cottage cheese, Sweet Curd cottage, Popcorn cheese, Cream cheese, Neufchatel cheese); (2) rennet cheese with milk being coagulated by rennet ferment; (3) acidic cheese with milk being coagulated by generating lactic acid; (4) brine cheese seasoned in strong brine during the process of maturing and storage (the Brick cheese); (5) processed cheese prepared from various sorts of natural cheeses by means of melting; (6) rindless cheese which matures sealed under vacuum in polymer pellicles (the Rindless Swiss cheese).
According to the consistency and body cheeses may be further classified as hard (the Cheddar, Swiss (the Emmental, Sweitzer)); semi-hard (the Roquefort, Stilton, Gorgonzola, Brick cheese, Blue-veined cheese, Blue Mold cheese) and soft (the Camembert).
According to the method of ripening, or maturing soft and semi-soft cheeses can be mold-ripened (the Roquefort-group), or bacteria-ripened, or both (the Camembert).
Cheeses may be also classified according to the source of milk. They can be made from the milk of any milk-giving animal, though it is universally made from cow's milk. Roquefort is the only world famous cheese made from ewe's milk. Goat's milk cheese is extremely popular in Scandinavian countries. Laplanders make cheese from the reindeer's milk; and a famous early Italian cheese variety, the Scarmorze, was originally made from buffalo's milk.
More than 400 named varieties are officially recognized, but these can all be classified as variations of about twenty distinctive types. Thus, over 200 varieties of soft cheese are reported to be manufactured in France, but the names of most are only of local significance.
Nevertherless, according to Federal Standards we can identify the common requirements to the composition of cheese: Moisture - 30-75%; Fat in the solids - 0-50%; Salt - 0-2%; Ptotein - up to 25%.
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