Food Protection with Chemicals, and by Biocontrol 309
became toxic after 2 weeks, but when 40 ppm of nitrite was accompanied by 0.9% sucrose and
an inoculum of L. plantarum, none of 30 became toxic. Although this was most likely a direct pH
effect, other factors may have been involved. In later studies, bacon was prepared with 40 or 80 ppm
of NaNO 2 + 0.7% sucrose followed by inoculation with Pediococcus acidilactici. When inoculated
with C. botulinum types A and B spores, vacuum packaged, and incubated up to 56 days at 27
◦ C, the
bacon was found to have greater antibotulinal properties than control bacon prepared with 120 ppm
of NaNO 2 but not sucrose or lactic inoculum.
188 Bacon prepared by the above formulation, called the
Wisconsin process, was preferred by a sensory panel to that prepared by the conventional method.
187
The Wisconsin process employs 550 ppm of sodium ascorbate or sodium erythrobate, as does the
conventional process.
Nitrosamines
When nitrite reacts with secondary amines, nitrosamines are formed, and many are known to be
carcinogenic. The generalized way in which nitrosamines may form is as follows:
R 2 NH 2 + HONO
H +
−→ R 2 N − NO + H 2 O
The amine dimethylamine reacts with nitrite to form N -nitrosodimethylamine:
H 3 C
H 3 C
\
\
N − H + NO 2 → N−N = O
/
/
H 3 C
H 3 C
In addition to secondary amines, tertiary amines and quaternary ammonium compounds also yield
nitrosamines with nitrite under acidic conditions. Nitrosamines have been found in cured meat and
fish products at low levels. Isoascorbate has an inhibitory effect on nitrosamine formation.
It has been shown that lactobacilli, enterococci, clostridia, and other bacteria will nitrosate secondary
amines with nitrite at neutral pH values.
79 The fact that nitrosation occurred at near-neutral pH values
was taken to indicate that the process was enzymatic, although no cell-free enzyme was obtained.
80
Several species of catalase-negative cocci, including E. faecalis, E. faecium, and L. lactis, have been
shown to be capable of forming nitrosamines, but the other lactic acid bacteria and pseudomonads
tested did not.
36 These investigators found no evidence for an enzymatic reaction. S. aureus and
halobacteria obtained from Chinese salted marine fish (previously shown to contain nitrosamines)
produced nitrosamines when inoculated into salted fish homogenates containing 40 ppm of nitrate and
5 ppm of nitrite.
58
Nitrite–Sorbate and Other Nitrite Combinations
In an effort to reduce the potential hazard of N -nitrosamine formation in bacon, the USDA in 1978
reduced the input NO 2 level for bacon to 120 ppm and set a 10-ppb maximum level for nitrosamines.
Although 120 ppm of nitrite along with 550 ppm of sodium ascorbate or sodium erythrobate are
adequate to reduce the botulism hazard, it is desirable to reduce nitrite levels even further if protection
against botulinal toxin production can be achieved. To this end, a proposal to allow the use of 40 ppm of
nitrite in combination with 0.26% potassium sorbate for bacon was made in 1978 but rescinded a year
later when taste panel studies revealed undesirable effects. Meanwhile, many groups of researchers
became toxic after 2 weeks, but when 40 ppm of nitrite was accompanied by 0.9% sucrose and
an inoculum of L. plantarum, none of 30 became toxic. Although this was most likely a direct pH
effect, other factors may have been involved. In later studies, bacon was prepared with 40 or 80 ppm
of NaNO 2 + 0.7% sucrose followed by inoculation with Pediococcus acidilactici. When inoculated
with C. botulinum types A and B spores, vacuum packaged, and incubated up to 56 days at 27
◦ C, the
bacon was found to have greater antibotulinal properties than control bacon prepared with 120 ppm
of NaNO 2 but not sucrose or lactic inoculum.
188 Bacon prepared by the above formulation, called the
Wisconsin process, was preferred by a sensory panel to that prepared by the conventional method.
187
The Wisconsin process employs 550 ppm of sodium ascorbate or sodium erythrobate, as does the
conventional process.
Nitrosamines
When nitrite reacts with secondary amines, nitrosamines are formed, and many are known to be
carcinogenic. The generalized way in which nitrosamines may form is as follows:
R 2 NH 2 + HONO
H +
−→ R 2 N − NO + H 2 O
The amine dimethylamine reacts with nitrite to form N -nitrosodimethylamine:
H 3 C
H 3 C
\
\
N − H + NO 2 → N−N = O
/
/
H 3 C
H 3 C
In addition to secondary amines, tertiary amines and quaternary ammonium compounds also yield
nitrosamines with nitrite under acidic conditions. Nitrosamines have been found in cured meat and
fish products at low levels. Isoascorbate has an inhibitory effect on nitrosamine formation.
It has been shown that lactobacilli, enterococci, clostridia, and other bacteria will nitrosate secondary
amines with nitrite at neutral pH values.
79 The fact that nitrosation occurred at near-neutral pH values
was taken to indicate that the process was enzymatic, although no cell-free enzyme was obtained.
80
Several species of catalase-negative cocci, including E. faecalis, E. faecium, and L. lactis, have been
shown to be capable of forming nitrosamines, but the other lactic acid bacteria and pseudomonads
tested did not.
36 These investigators found no evidence for an enzymatic reaction. S. aureus and
halobacteria obtained from Chinese salted marine fish (previously shown to contain nitrosamines)
produced nitrosamines when inoculated into salted fish homogenates containing 40 ppm of nitrate and
5 ppm of nitrite.
58
Nitrite–Sorbate and Other Nitrite Combinations
In an effort to reduce the potential hazard of N -nitrosamine formation in bacon, the USDA in 1978
reduced the input NO 2 level for bacon to 120 ppm and set a 10-ppb maximum level for nitrosamines.
Although 120 ppm of nitrite along with 550 ppm of sodium ascorbate or sodium erythrobate are
adequate to reduce the botulism hazard, it is desirable to reduce nitrite levels even further if protection
against botulinal toxin production can be achieved. To this end, a proposal to allow the use of 40 ppm of
nitrite in combination with 0.26% potassium sorbate for bacon was made in 1978 but rescinded a year
later when taste panel studies revealed undesirable effects. Meanwhile, many groups of researchers