76
Modern Food Microbiology
investigators found that the temperature control of hot-boned meat during the early hours of chilling
is critical and in a later study found that chilling to 21
◦ C within 3–9 hours was satisfactory.
60
In a study of sausage made from hot-boned pork, significantly higher counts of mesophiles and
lipolytics were found in the product made from hot-boned pork than in the cold-boned product, but
no significant differences in psychrotrophs were found.
114
The effect that delayed chilling might have on the biota of hot-boned beef taken about 1 hour
after slaughter was examined by McMillin et al.
125 Portions were chilled for 1, 2, 4, and 8 hours
after slaughter and subsequently ground, formed into patties, frozen, and examined. No significant
differences were found between this product and a cold-boned product relative to coliforms, staphylococci, psychrotrophs, and mesophiles. A numerical taxonomy study of the biota from hot-boned and
cold-boned beef at both the time of processing and after 14 days of vacuum storage at 2
◦ C revealed
no statistically significant differences in the biota.
108 The predominant organisms, after storage, for
both products were “streptococci” (most likely enterococci) and lactobacilli, whereas in the freshly
prepared hot-boned product (before storage), more staphylococci and bacilli were found. Overall,
though, the two products were comparable.
Restructured lamb roast made from 10% and 30% MDM and hot-boned meat was examined for
microorganisms; overall, the two uncooked products were of good quality.
148 The uncooked products
had counts <3.0 × 10
4 /g, with generally higher numbers in products containing the higher amounts
of MDM. Coliforms and fecal coliforms especially were higher in products with 30% MDM, and
this was thought to be caused by contamination of shanks and pelvic regions during slaughtering and
evisceration. Not detected in either uncooked product (in 0.1 g) were S. aureus and C. perfringens; no
salmonellae, Yersinia enterocolitica, or Campylobacter jejuni, were found in 25-g samples. Cooking
reduced cell counts in all products to <30/g.
A summary of the work of 10 groups of investigators made by Kotula
100 on the effect of hot boning
on the microbiology of meats revealed that six found no effect, three found only limited effects, and
only one found higher counts. Kotula concluded that hot boning per se has no effect on microbial
counts. Hot boning is often accompanied by prerigor pressurization consisting of the application of
around 15,000 psi for 2 minutes. This process improves muscle color and overall shelf appearance
and increases tenderization. It appears not to have any effect on the microbiota.
Effect of Electrical Stimulation
If the temperature of a beef carcass falls to <10
◦ C before carcass pH is <5.9 or so, the meat will “cold
shorten” and thus become tough. Electrical stimulation increases the rate of pH drop by stimulating the
speed of conversion of glycogen to lactic acid and thus eliminating the toughening. By this method, an
electric stunner is attached to a carcass, and repeated pulses of 0.5–1.0 or more seconds are administered
to the product at 400+V potential differences between the electrodes. A summary of the findings of 10
groups of researchers on what effect, if any, electrical stimulation had on the microbiota revealed that
6 found no effect, two found a slight effect, and two found some effect.
100 The meats studied included
beef, lamb, and pork.
Among investigators who found a reduction of APC by electrical stimulation were Ockerman and
Szczawinski
135 who found that the process significantly reduced the APC of samples of beef inoculated before electrical stimulation, but when samples were inoculated immediately after the treatment, no significant reductions occurred. The latter finding suggests that the disruption of lysosomal
membranes and the consequent release of catheptic enzymes, which has been shown to accompany
electrical stimulation,
45 should not affect microorganisms. The tenderization associated with electrical
Modern Food Microbiology
investigators found that the temperature control of hot-boned meat during the early hours of chilling
is critical and in a later study found that chilling to 21
◦ C within 3–9 hours was satisfactory.
60
In a study of sausage made from hot-boned pork, significantly higher counts of mesophiles and
lipolytics were found in the product made from hot-boned pork than in the cold-boned product, but
no significant differences in psychrotrophs were found.
114
The effect that delayed chilling might have on the biota of hot-boned beef taken about 1 hour
after slaughter was examined by McMillin et al.
125 Portions were chilled for 1, 2, 4, and 8 hours
after slaughter and subsequently ground, formed into patties, frozen, and examined. No significant
differences were found between this product and a cold-boned product relative to coliforms, staphylococci, psychrotrophs, and mesophiles. A numerical taxonomy study of the biota from hot-boned and
cold-boned beef at both the time of processing and after 14 days of vacuum storage at 2
◦ C revealed
no statistically significant differences in the biota.
108 The predominant organisms, after storage, for
both products were “streptococci” (most likely enterococci) and lactobacilli, whereas in the freshly
prepared hot-boned product (before storage), more staphylococci and bacilli were found. Overall,
though, the two products were comparable.
Restructured lamb roast made from 10% and 30% MDM and hot-boned meat was examined for
microorganisms; overall, the two uncooked products were of good quality.
148 The uncooked products
had counts <3.0 × 10
4 /g, with generally higher numbers in products containing the higher amounts
of MDM. Coliforms and fecal coliforms especially were higher in products with 30% MDM, and
this was thought to be caused by contamination of shanks and pelvic regions during slaughtering and
evisceration. Not detected in either uncooked product (in 0.1 g) were S. aureus and C. perfringens; no
salmonellae, Yersinia enterocolitica, or Campylobacter jejuni, were found in 25-g samples. Cooking
reduced cell counts in all products to <30/g.
A summary of the work of 10 groups of investigators made by Kotula
100 on the effect of hot boning
on the microbiology of meats revealed that six found no effect, three found only limited effects, and
only one found higher counts. Kotula concluded that hot boning per se has no effect on microbial
counts. Hot boning is often accompanied by prerigor pressurization consisting of the application of
around 15,000 psi for 2 minutes. This process improves muscle color and overall shelf appearance
and increases tenderization. It appears not to have any effect on the microbiota.
Effect of Electrical Stimulation
If the temperature of a beef carcass falls to <10
◦ C before carcass pH is <5.9 or so, the meat will “cold
shorten” and thus become tough. Electrical stimulation increases the rate of pH drop by stimulating the
speed of conversion of glycogen to lactic acid and thus eliminating the toughening. By this method, an
electric stunner is attached to a carcass, and repeated pulses of 0.5–1.0 or more seconds are administered
to the product at 400+V potential differences between the electrodes. A summary of the findings of 10
groups of researchers on what effect, if any, electrical stimulation had on the microbiota revealed that
6 found no effect, two found a slight effect, and two found some effect.
100 The meats studied included
beef, lamb, and pork.
Among investigators who found a reduction of APC by electrical stimulation were Ockerman and
Szczawinski
135 who found that the process significantly reduced the APC of samples of beef inoculated before electrical stimulation, but when samples were inoculated immediately after the treatment, no significant reductions occurred. The latter finding suggests that the disruption of lysosomal
membranes and the consequent release of catheptic enzymes, which has been shown to accompany
electrical stimulation,
45 should not affect microorganisms. The tenderization associated with electrical