Fresh Meats and Poultry
75
of lean meat left on carcass bones is by mechanical means (mechanical deboning). Mechanically
deboned meat (MDM) is removed from bones by machines. The production of MDM began in the
1970s, preceded by chicken meat in the late 1950s, and fish in the late 1940s.
53,58 During the deboning
process, small quantities of bone powder become part of the finished product, and the 1978 U.S.
Department of Agriculture (USDA) regulation limits the amount of bone (based on calcium content)
to no more than 0.75% (the calcium content of meat is 0.01%). MDM must contain a minimum of 14%
protein and no more than 30% fat. The most significant parametrical difference between MDM and
conventionally processed meat relative to microbial growth is the higher pH of the former, typically
6.0–7.0.
53,54 The increased pH is due to the incorporation of marrow in MDM.
Although most studies on the microbiology of MDM have shown these products to be not unlike
those produced by conventional methods, some have found higher counts. The microbiological quality
of deboned poultry was compared to other raw poultry products, and although the counts were comparable, MPN coliform counts of the commercial MDM products ranged from 460 to >1,100/g. Six of
54 samples contained salmonellae, four contained C. perfringens, but none contained S. aureus.
137 The
APC of handboned lamb breasts was found to be 680,000, whereas for mechanically deboned lamb
allowed to age for 1 week, the APC was 650,000/g.
55 Commercial samples of mechanically deboned
fish were found to contain tenfold higher numbers of organisms than conventionally processed fish,
but different methods were used to perform the counts on fish frames and the mechanically deboned
flesh (MDF
146 ). These investigators did not find S. aureus and concluded that the spoilage of MDF was
similar to that for the traditionally processed products. In a later study, MDM was found to support
the more rapid growth of psychrotrophic bacteria than lean ground beef.
149
Several studies have revealed the absence of S. aureus in MDM, reflecting perhaps the fact that these
products are less handled by meat cutters. In general, the mesophilic biota count is a bit higher than
that for psychrotrophs, and fewer Gram negatives tend to be found. Field
53 concluded that with good
manufacturing practices, MDM should present no microbiological problems, and a similar conclusion
was reached by Froning
58 relative to deboned poultry and fish.
Hot-Boned Meats
In the conventional processing of meats (cold boning), carcasses are chilled after slaughter for 24
hours or more and processed in the chilled state (postrigor). Hot boning (hot processing) involves
the processing of meats generally within 1–2 hours after slaughter (prerigor) while the carcass is still
“hot.”
In general, the microbiology of hot-boned meats is comparable to that of cold-boned meats, but
some differences have been reported. One of the earliest studies on hot-boned hams evaluated the
microbiological quality of cured hams made from hot-boned meat (hot-processed hams). These hams
were found to contain a significantly higher APC (at 37
◦ C) than cold-boned hams, and 67% of the
former yielded staphylococci to 47% of the latter.
145 Mesophiles counted at 35
◦ C were significantly
higher on hot-boned prime cuts than comparable cold-boned cuts, both before and after vacuumpackaged storage at 2
◦ C for 20 days.
101 Coliforms, however, were apparently not affected by hot
boning. Another early study is that of Barbe et al.,
9 who evaluated 19 paired hams (hot and cold
boned) and found that the former contained 200 bacteria per gram, whereas 220 per gram were found
in the latter. In a study of hot-boned carcasses held at 16
◦ C and cold-boned bovine carcasses held at
2
◦ C for up to 16 hours postmortem, no significant differences in mesophilic and psychrotrophic counts
were found.
96 Both hot-boned and cold-boned beef initially contained low bacterial counts, but after
a 14-day storage period, the hot-boned meats contained higher numbers than the cold boned.
59 These
75
of lean meat left on carcass bones is by mechanical means (mechanical deboning). Mechanically
deboned meat (MDM) is removed from bones by machines. The production of MDM began in the
1970s, preceded by chicken meat in the late 1950s, and fish in the late 1940s.
53,58 During the deboning
process, small quantities of bone powder become part of the finished product, and the 1978 U.S.
Department of Agriculture (USDA) regulation limits the amount of bone (based on calcium content)
to no more than 0.75% (the calcium content of meat is 0.01%). MDM must contain a minimum of 14%
protein and no more than 30% fat. The most significant parametrical difference between MDM and
conventionally processed meat relative to microbial growth is the higher pH of the former, typically
6.0–7.0.
53,54 The increased pH is due to the incorporation of marrow in MDM.
Although most studies on the microbiology of MDM have shown these products to be not unlike
those produced by conventional methods, some have found higher counts. The microbiological quality
of deboned poultry was compared to other raw poultry products, and although the counts were comparable, MPN coliform counts of the commercial MDM products ranged from 460 to >1,100/g. Six of
54 samples contained salmonellae, four contained C. perfringens, but none contained S. aureus.
137 The
APC of handboned lamb breasts was found to be 680,000, whereas for mechanically deboned lamb
allowed to age for 1 week, the APC was 650,000/g.
55 Commercial samples of mechanically deboned
fish were found to contain tenfold higher numbers of organisms than conventionally processed fish,
but different methods were used to perform the counts on fish frames and the mechanically deboned
flesh (MDF
146 ). These investigators did not find S. aureus and concluded that the spoilage of MDF was
similar to that for the traditionally processed products. In a later study, MDM was found to support
the more rapid growth of psychrotrophic bacteria than lean ground beef.
149
Several studies have revealed the absence of S. aureus in MDM, reflecting perhaps the fact that these
products are less handled by meat cutters. In general, the mesophilic biota count is a bit higher than
that for psychrotrophs, and fewer Gram negatives tend to be found. Field
53 concluded that with good
manufacturing practices, MDM should present no microbiological problems, and a similar conclusion
was reached by Froning
58 relative to deboned poultry and fish.
Hot-Boned Meats
In the conventional processing of meats (cold boning), carcasses are chilled after slaughter for 24
hours or more and processed in the chilled state (postrigor). Hot boning (hot processing) involves
the processing of meats generally within 1–2 hours after slaughter (prerigor) while the carcass is still
“hot.”
In general, the microbiology of hot-boned meats is comparable to that of cold-boned meats, but
some differences have been reported. One of the earliest studies on hot-boned hams evaluated the
microbiological quality of cured hams made from hot-boned meat (hot-processed hams). These hams
were found to contain a significantly higher APC (at 37
◦ C) than cold-boned hams, and 67% of the
former yielded staphylococci to 47% of the latter.
145 Mesophiles counted at 35
◦ C were significantly
higher on hot-boned prime cuts than comparable cold-boned cuts, both before and after vacuumpackaged storage at 2
◦ C for 20 days.
101 Coliforms, however, were apparently not affected by hot
boning. Another early study is that of Barbe et al.,
9 who evaluated 19 paired hams (hot and cold
boned) and found that the former contained 200 bacteria per gram, whereas 220 per gram were found
in the latter. In a study of hot-boned carcasses held at 16
◦ C and cold-boned bovine carcasses held at
2
◦ C for up to 16 hours postmortem, no significant differences in mesophilic and psychrotrophic counts
were found.
96 Both hot-boned and cold-boned beef initially contained low bacterial counts, but after
a 14-day storage period, the hot-boned meats contained higher numbers than the cold boned.
59 These