Raw material selection: meat and poultry S.J. James, Food Refrigeration and process engineering research Centre 3.1 Introduction Much poultry and red meat is sold in a chilled unprocessed state. However, an ncreasing proportion is used as a basic raw material for chilled meat products and ready meals. A growing trend is the development of added-value convenience meals, especially ethnic products, many of which are pre-or part-cooked and necessitate chilled storage. Many of these products contain meat as a key ingredient. This meat for further processing can be supplie chilled, as boneless blocks of frozen material or increasingly as minced or diced material. The dice or mince can be chilled or increasingly it will be supplied as bags of individually quick frozen (IQF) product. This chapter discusses a number of issues which influence the quality of meat as a raw material in high added-value chilled foods The quality of meat is judged by its bacterial condition and appearance Bacterial condition is subjectively assessed by the presence or absence of odour or slime. Quantitative tests can also carried out to determine the total viable counts and the presence of specific pathogens or indicator organisms Appearance criteria are primarily; colour, percentage of fat and lean and amount of drip exuding from the meat. Any unacceptable change in the microbial or appearance criteria will limit the shelf-life of the meat. After cooking its eating quality is partially judged by its appearance but mainly by its tenderness, flavour and juiciness Red meat and poultry are very perishable raw materials. If stored under ambient conditions. 16-30%C. the shelf-life of both can be measured in tens of hours to a few days. Under the best conditions of chilled storage, close to the initial freezing point of the material, the storage be extended to
3.1 Introduction Much poultry and red meat is sold in a chilled unprocessed state. However, an increasing proportion is used as a basic raw material for chilled meat products and ready meals. A growing trend is the development of added-value convenience meals, especially ethnic products, many of which are pre- or part-cooked and necessitate chilled storage. Many of these products contain meat as a key ingredient. This meat for further processing can be supplied chilled, as boneless blocks of frozen material or increasingly as minced or diced material. The dice or mince can be chilled or increasingly it will be supplied as bags of individually quick frozen (IQF) product. This chapter discusses a number of issues which influence the quality of meat as a raw material in high added-value chilled foods. The quality of meat is judged by its bacterial condition and appearance. Bacterial condition is subjectively assessed by the presence or absence of odour or slime. Quantitative tests can also carried out to determine the total viable counts and the presence of specific pathogens or indicator organisms. Appearance criteria are primarily; colour, percentage of fat and lean and amount of drip exuding from the meat. Any unacceptable change in the microbial or appearance criteria will limit the shelf-life of the meat. After cooking its eating quality is partially judged by its appearance but mainly by its tenderness, flavour and juiciness. Red meat and poultry are very perishable raw materials. If stored under ambient conditions, 16–30ºC, the shelf-life of both can be measured in tens of hours to a few days. Under the best conditions of chilled storage, close to the initial freezing point of the material, the storage life can be extended to 3 Raw material selection: meat and poultry S. J. James, Food Refrigeration and Process Engineering Research Centre
64 Chilled foods zen 979-80 Fig 3.1 Percentage of chilled and frozen poultry carcasses contaminated with salmonella found in UK surveys carried out in 1979-80 to 1994 cks for some red meat. even under the best commercial practice (strictly hygienic slaughtering, rapid cooling, vacuum packing and storage at super chill (-1+0.5C)the maximum life that can be achieved in red meat is approximately 20 weeks, however, freezing will extend the storage life of meat to a number of years In a perfect world, red meat and poultry would be completely free of athogenic(food poisoning) micro-organisms when produced. However, under normal methods of production pathogen-free meat cannot be guaranteed. For example, salmonella contamination of chilled and frozen poultry carcasses has UK(Fig. 3.1) still contaminated in 1994. While the internal musculature of a heal thy mammal or bird is essentially sterile after slaughter, all meat animals carry large numbers of different micro-organisms on their skin/feathers and in their alimentary tract Only a few types of bacteria directly affect the safety and quality of the finished carcass. Of particular concern are food-borne pathogens such as Campylobacter pp, Clostridium perfringens, Salmonella spp, and pathogenic serotypes of Escherichia coli. The minimum and optimum growth temperatures for some of the pathogens associated with red and poultry meat are shown in Table 3.1 Inevitably, small numbers of pathogens will be present on meat and cooking regimes are designed to eliminate their presence. Most red meat and poultry food poisoning is associated with inadequate cooking or subsequent contamina- tion after cooking and poor cooking and storage Normally it is the growth of spoilage organisms that has the mportant effect in limiting the shelf-life of meat. The spoilage bacteria of meats stored air under chill conditions include species of Pseudomonas, Brochothrix and Acinetobacter/Moraxella. Varnam and Sutherland state that in general, there is
approaching six weeks for some red meat. Even under the best commercial practice (strictly hygienic slaughtering, rapid cooling, vacuum packing and storage at super chill (10.5ºC)) the maximum life that can be achieved in red meat is approximately 20 weeks, however, freezing will extend the storage life of meat to a number of years. In a perfect world, red meat and poultry would be completely free of pathogenic (food poisoning) micro-organisms when produced. However, under normal methods of production pathogen-free meat cannot be guaranteed. For example, salmonella contamination of chilled and frozen poultry carcasses has been significantly reduced in the UK (Fig. 3.1). However, over one-third was still contaminated in 1994.1 While the internal musculature of a healthy mammal or bird is essentially sterile after slaughter, all meat animals carry large numbers of different micro-organisms on their skin/feathers and in their alimentary tract. Only a few types of bacteria directly affect the safety and quality of the finished carcass. Of particular concern are food-borne pathogens such as Campylobacter spp., Clostridium perfringens, Salmonella spp., and pathogenic serotypes of Escherichia coli. The minimum and optimum growth temperatures for some of the pathogens associated with red and poultry meat are shown in Table 3.1. Inevitably, small numbers of pathogens will be present on meat and cooking regimes are designed to eliminate their presence. Most red meat and poultry food poisoning is associated with inadequate cooking or subsequent contamination after cooking and poor cooking and storage. Normally it is the growth of spoilage organisms that has the most important effect in limiting the shelf-life of meat. The spoilage bacteria of meats stored in air under chill conditions include species of Pseudomonas, Brochothrix and Acinetobacter/Moraxella. Varnam and Sutherland state that in general, there is Fig. 3.1 Percentage of chilled and frozen poultry carcasses contaminated with salmonella found in UK surveys carried out in 1979–80 to 1994. 64 Chilled foods
Raw material selection: meat and poultry 65 Table 3.1 Chilled storage life of meat and meat products at different storage temperatures Storage time(days)in temperature range -4.lto-l.1 2.ltos.1°C 5.2to8.2°C Food Mean sd Mean sd Mean sd Mean Bacon 45 20 Beef 40263432 aooe 5086 10 461 18 Rabbi Offal 6 Sausage 10 little difference in the microbial spoilage of beef, lamb, pork and other meat derived from mammals The presence of exudate or 'drip, which accumulates in the container of pre- packaged meat, or in trays or dishes of unwrapped meat, substantially reduces its sales appeal. Drip can be referred to by a number of different names including purge loss,,press loss' and thaw loss' depending on the method of measurement and when it is measured. Drip loss occurs throughout the cold chain and represents a considerable economic loss to the red meat industry Poultry meat is far less prone to drip. The potential for drip loss is inherent in fresh meat and is influenced by many factors. Some of these, including breed diet and physiological history, are inherent in the live animal. Others, such as the rate of chilling, storage temperatures, freezing and thawing, occur during processing. Meat colour can be adversely affected by a variety of factors, including post-mortem handling, chilling, storage and packaging In Australia, CSIRO stated that Toughness is caused by three major factors advancing age of the animal, 'cold shortening '(the muscle fibre contraction at can occur during chilling)and unfavourable meat acidity(pH). 'There is general agreement on the importance of these factors, with many experts adding oking as a fourth equally important influent 3.2 The influence of the live animal Some of the factors that influence the toughness or meat are inherent in the live animal. Church and wood state that it is now well established that it is the properties of the connective tissue proteins, and not the total amount of collagen in meat, that largely determines whether meat is tough or tender. As the animal
little difference in the microbial spoilage of beef, lamb, pork and other meat derived from mammals. The presence of exudate or ‘drip’, which accumulates in the container of prepackaged meat, or in trays or dishes of unwrapped meat, substantially reduces its sales appeal.3 Drip can be referred to by a number of different names including ‘purge loss’, ‘press loss’ and ‘thaw loss’ depending on the method of measurement and when it is measured. Drip loss occurs throughout the cold chain and represents a considerable economic loss to the red meat industry. Poultry meat is far less prone to drip. The potential for drip loss is inherent in fresh meat and is influenced by many factors. Some of these, including breed, diet and physiological history, are inherent in the live animal. Others, such as the rate of chilling, storage temperatures, freezing and thawing, occur during processing. Meat colour can be adversely affected by a variety of factors, including post-mortem handling, chilling, storage and packaging.4 In Australia, CSIRO5 stated that ‘Toughness is caused by three major factors – advancing age of the animal, ‘cold shortening’ (the muscle fibre contraction that can occur during chilling) and unfavourable meat acidity (pH).’ There is general agreement on the importance of these factors, with many experts adding cooking as a fourth equally important influence. 3.2 The influence of the live animal Some of the factors that influence the toughness or meat are inherent in the live animal. Church and Wood4 state that it is now well established that it is the properties of the connective tissue proteins, and not the total amount of collagen in meat, that largely determines whether meat is tough or tender. As the animal Table 3.1 Chilled storage life of meat and meat products at different storage temperatures Storage time (days) in temperature range: 4.1 to 1.1ºC 1 to 2ºC 2.1 to 5.1ºC 5.2 to 8.2ºC Food Mean sd Mean sd Mean sd Mean sd Bacon 45 6 15 3 42 20 Beef 40 26 34 32 10 8 9 9 Lamb 55 20 41 46 28 34 Pork 50 58 22 30 16 16 15 18 Poultry 32 18 17 10 12 11 7 3 Veal 21 10 6 49 49 Rabbit 9 7 13 6 Offal 7 7 6 14 7 Bacon 45 6 15 3 42 20 Sausage 80 43 21 16 36 28 24 10 Raw material selection: meat and poultry 65
66 Chilled foods grows older the number of immature reducible cross-links decreases The mature cross-links result in a toughening of the collagen and this in turn can produce cially significant until a beast is about four years old o probably not commer- tough meat. Increasing connective tissue toughness is e. The pigment concentration in meat which governs its colour is affected by any factors affecting the live animal. These include species -beef, for example, contains substantially more myoglobin than pork; breed and age pigment concentration increases with age; sex- meat from male animals usually contains more pigment than that from female animals; muscle- muscles that do more work contain more myoglobin There are also two specific meat defects; dark, firm, dry(DFD) and pale, soft, exudative(PSE)associated with the live animal that result in poor meat colour DFD meat has a high ultimate pH and oxygen penetration is low. Consequently the oxymyoglobin layer is thin, the purple myoglobin layer shows through, and the meat appears dark In PSe meat the pH falls while the muscle is still warm and partial denaturation of the proteins occurs. An increased amount of light is scattered and part of the pigment oxidised so that the meat appears pale 3.2.1 Between species and breeds In all species the range of storage lives found in the literature is very large (Table 3. 1)and indicate that factors other than species have a pronounced effect on storage life. Overall, species has little effect on the practical storage life of meat. In general, beef tends to lose proportionately more drip than pork and lamb. Unfrozen poultry meat looses little if any drip. Since most of the exudate comes from the cut ends of muscle fibres, small pieces of meat drip more than large intact carcasses. In pigs, especially, there are large differences in drip loss from meat from different breeds and between different muscles. Taylor'showed that there was a substantial difference, up to 2.5 fold, in drip loss between four different breeds of pig(Table 3.2). He also showed that there was a 1.7 to 2.8 fold difference in drip between muscle types(Table 3.3) Although there is a common belief that breed has a major effect on meat quality CSirO state although there are small differences in tenderness due to Table 3. 2 Drip loss after two days storage at ooC, from leg joints from different breeds of pig cooled at different rates Breed Drip loss ( by wt. Slow Wessex X Large White Pietrain 0.6
grows older the number of immature reducible cross-links decreases. The mature cross-links result in a toughening of the collagen and this in turn can produce tough meat. Increasing connective tissue toughness is probably not commercially significant until a beast is about four years old.6 The pigment concentration in meat which governs its colour is affected by many factors affecting the live animal. These include species – beef, for example, contains substantially more myoglobin than pork; breed and age – pigment concentration increases with age; sex – meat from male animals usually contains more pigment than that from female animals; muscle – muscles that do more work contain more myoglobin. There are also two specific meat defects; dark, firm, dry (DFD) and pale, soft, exudative (PSE) associated with the live animal that result in poor meat colour. DFD meat has a high ultimate pH and oxygen penetration is low. Consequently, the oxymyoglobin layer is thin, the purple myoglobin layer shows through, and the meat appears dark. In PSE meat the pH falls while the muscle is still warm and partial denaturation of the proteins occurs. An increased amount of light is scattered and part of the pigment oxidised so that the meat appears pale. 3.2.1 Between species and breeds In all species the range of storage lives found in the literature is very large (Table 3.1) and indicate that factors other than species have a pronounced effect on storage life. Overall, species has little effect on the practical storage life of meat. In general, beef tends to lose proportionately more drip than pork and lamb. Unfrozen poultry meat looses little if any drip. Since most of the exudate comes from the cut ends of muscle fibres, small pieces of meat drip more than large intact carcasses. In pigs, especially, there are large differences in drip loss from meat from different breeds and between different muscles. Taylor7 showed that there was a substantial difference, up to 2.5 fold, in drip loss between four different breeds of pig (Table 3.2). He also showed that there was a 1.7 to 2.8 fold difference in drip between muscle types (Table 3.3). Although there is a common belief that breed has a major effect on meat quality CSIRO8 state ‘although there are small differences in tenderness due to Table 3.2 Drip loss after two days storage at 0ºC, from leg joints from different breeds of pig cooled at different rates Breed Drip loss (% by wt.) Slow Quick Landrace 0.47 0.24 Large White 0.73 0.42 Wessex X Large White 0.97 0.61 Pietrain 1.14 0.62 66 Chilled foods
Raw material selection: meat and poultry 67 Table 3.3 Drip loss after two days storage at 0@C from four muscles from two breeds of pig cooled at different rates Adductor Biceps Combined tendinosus membranous femoris (4 muscles) Pietrain Quick 2.82 4.115.30 Large white 1.04 Slow 1.95 2.323.2 breed, they are slight and currently of no commercial significance to Australian consumers.That said, there are substantial differences in the proportion of acceptable tender meat and toughness between Bos indicus* and Bos taurus* cattle. The proportion of acceptable tender meat has been found to decrease from 100% in Hereford Angus crosses, to 96% in Tarentaise, 93% in Pinzgauer, 86% in Brahman and only 80% in Tsahiwal. Toughness of meat increases as the proportion of Bos indicus increases 3.2.2 Animal to animal variation here is little data on any relationship between animal to animal variation and chilled storage life. However. it is believed to cause wide variations in frozen storage life; differences can be as great as 50% in the freezing of lamb. 2 Differences would appear to be caused by genetic, seasonal or nutritional variation between animals, but there is little reported work to confirm this view Variations were found between the fatty acids and ratio of saturated/unsaturated fatty acids in lambs from New Zealand, America and England. Differences related to sex, geographical area and cut were mainly a reflection of fatness, ith ewes having a greater percentage of body fat than rams. However, differences between areas were found to produce larger variations between animals than sex differences. a number of other trials have detailed differenc between animals There can also be significant differences in texture within Longissimus dorsi shear force values for double muscled Belgium Blue bulls were significantly higher than those of the same breed with normal conformation. Calpain I levels at I h and 24 h post mortem were also much lower. It was suggested that the lower background toughness in the double muscle was compensated for by reduced post mortem proteolytic tenderisation Sex of the animal appears to have little or no influence on tenderness. Huff and Parrish compared the tenderness of meat from 14-month-old bulls and s Bos indicus are tropical and semitropical breeds of cattle primarily Brahman and Bos taurus are temperate breeds such as Hereford or Aberdeen Angus
breed, they are slight and currently of no commercial significance to Australian consumers.’ That said, there are substantial differences in the proportion of acceptable tender meat and toughness between Bos indicus* and Bos taurus* cattle. The proportion of acceptable tender meat has been found to decrease from 100% in Hereford Angus crosses, to 96% in Tarentaise, 93% in Pinzgauer, 86% in Brahman and only 80% in Tsahiwal.9 Toughness of meat increases as the proportion of Bos indicus increases.10 3.2.2 Animal to animal variation There is little data on any relationship between animal to animal variation and chilled storage life. However, it is believed to cause wide variations in frozen storage life; differences can be as great as 50% in the freezing of lamb.11, 12 Differences would appear to be caused by genetic, seasonal or nutritional variation between animals, but there is little reported work to confirm this view. Variations were found between the fatty acids and ratio of saturated/unsaturated fatty acids in lambs from New Zealand, America and England.13 Differences related to sex, geographical area and cut were mainly a reflection of fatness, with ewes having a greater percentage of body fat than rams. However, differences between areas were found to produce larger variations between animals than sex differences. A number of other trials have detailed differences between animals. There can also be significant differences in texture within a breed. Longissimus dorsi shear force values for double muscled Belgium Blue bulls were significantly higher than those of the same breed with normal conformation.14 Calpain I levels at 1 h and 24 h post mortem were also much lower. It was suggested that the lower background toughness in the double muscle was compensated for by reduced post mortem proteolytic tenderisation. Sex of the animal appears to have little or no influence on tenderness. Huff and Parrish15 compared the tenderness of meat from 14-month-old bulls and Table 3.3 Drip loss after two days storage at 0ºC from four muscles from two breeds of pig cooled at different rates Drip (as % muscle weight) Cooling Semi- Semi- Adductor Biceps Combined rate tendinosus membranous femoris (4 muscles) Pietrain Quick 2.82 4.40 5.52 2.69 3.86 Slow 3.99 6.47 6.61 4.11 5.30 Large White Quick 1.69 2.01 2.92 1.04 1.92 Slow 1.95 3.50 5.07 2.32 3.21 * Bos indicus are tropical and semitropical breeds of cattle primarily Brahman and Bos taurus are temperate breeds such as Hereford or Aberdeen Angus. Raw material selection: meat and poultry 67