330 Modern Food Microbiology
of CTC and OTC in delaying bacterial spoilage of not only fish and seafoods but poultry, red meats,
vegetables, raw milk, and other foods (for a review of food applications, see reference 96). CTC
is generally more effective than OTC. The surface treatment of refrigerated meats with 7–10 ppm
typically results in shelf-life extensions of at least 3–5 days and a shift in ultimate spoilage biota
from Gram-negative bacteria to yeasts and molds. When CTC is combined with sorbate to delay the
spoilage of fish, the combination has been shown to be effective for up to 14 days. Rockfish fillets
dipped in a solution of 5 ppm of CTC and 1% sorbate had significantly lower aerobic plate counts
(APCs) after vacuum-package storage at 2
◦ C after 14 days than controls.
128
The tetracyclines are both heat sensitive and storage labile in foods, and these factors were important
in their initial acceptance for food use. They are used to treat diseases in humans and animals and
are used also in feed supplements in the United States. The risks associated with their use as food
preservatives in developed countries seem clearly to outweigh the benefits.
Subtilin
This antibiotic was discovered and developed by scientists at the Western Regional Laboratory of
the USDA, and its properties were described by Dimick et al.
46 It is structurally similar to nisin (Figure
13–6), although it is produced by some strains of Bacillus subtilis. Like nisin, it is effective against
Gram-positive bacteria, is stable to acid, and possesses enough heat resistance to withstand destruction
at 121
◦ C for 30–60 minutes. Subtilin is effective in canned foods at levels of 5–20 ppm in preventing
the outgrowth of germinating endospores, and its site of action is the same as for nisin (Figure 13–1).
Like nisin, it is used neither in the treatment of human or animal infections nor as a feed additive. This
antibiotic may be just as effective as nisin, although it has received little attention since the late 1950s.
Its mode of action is discussed above along with that of nisin, and its development and evaluation have
been reviewed.
96
Tylosin
This antibiotic is a nonpolyene macrolide, as are the clinically useful antibiotics erythromycin, oleandomycin, and others. It is more inhibitory than nisin or subtilin. Denny et al.
41 were apparently the first
to study its possible use in canned foods. When 1 ppm was added to cream-style corn containing flatsour spores and given a “botulinal” cook, no spoilage of product occurred after 30 days with incubation
at 54
◦ C.
41 Similar findings were made by others in the 1960s, and these have been summarized.
41
Unlike nisin, subtilin, and natamycin, tylosin is used in animal feeds and also to treat some diseases
of poultry. As a macrolide, it is most effective against Gram-positive bacteria. It inhibits protein
synthesis by associating with the 50S ribosomal subunit and shows at least partial cross-resistance
with erythromycin.
ANTIFUNGAL AGENTS FOR FRUITS
Listed in Table 13–10 are some compounds applied to fruits after harvest to control fungi, primarily
molds. Benomyl is applied uniformly over the entire surface of fruits (examples are noted in Table
13–10). It is applied at concentrations of 0.5–1.0 g/l. It can penetrate the surface of some vegetables and
is used worldwide to control crown rot and anthracnose of bananas, and stem-end rots of citrus fruits. It
is more effective than thiabendazole and penetrates with greater ease. Both benomyl and thiabendazole
are effective in controlling dry rot caused by Fusarium spp. To prevent the spread of Botrytis from
of CTC and OTC in delaying bacterial spoilage of not only fish and seafoods but poultry, red meats,
vegetables, raw milk, and other foods (for a review of food applications, see reference 96). CTC
is generally more effective than OTC. The surface treatment of refrigerated meats with 7–10 ppm
typically results in shelf-life extensions of at least 3–5 days and a shift in ultimate spoilage biota
from Gram-negative bacteria to yeasts and molds. When CTC is combined with sorbate to delay the
spoilage of fish, the combination has been shown to be effective for up to 14 days. Rockfish fillets
dipped in a solution of 5 ppm of CTC and 1% sorbate had significantly lower aerobic plate counts
(APCs) after vacuum-package storage at 2
◦ C after 14 days than controls.
128
The tetracyclines are both heat sensitive and storage labile in foods, and these factors were important
in their initial acceptance for food use. They are used to treat diseases in humans and animals and
are used also in feed supplements in the United States. The risks associated with their use as food
preservatives in developed countries seem clearly to outweigh the benefits.
Subtilin
This antibiotic was discovered and developed by scientists at the Western Regional Laboratory of
the USDA, and its properties were described by Dimick et al.
46 It is structurally similar to nisin (Figure
13–6), although it is produced by some strains of Bacillus subtilis. Like nisin, it is effective against
Gram-positive bacteria, is stable to acid, and possesses enough heat resistance to withstand destruction
at 121
◦ C for 30–60 minutes. Subtilin is effective in canned foods at levels of 5–20 ppm in preventing
the outgrowth of germinating endospores, and its site of action is the same as for nisin (Figure 13–1).
Like nisin, it is used neither in the treatment of human or animal infections nor as a feed additive. This
antibiotic may be just as effective as nisin, although it has received little attention since the late 1950s.
Its mode of action is discussed above along with that of nisin, and its development and evaluation have
been reviewed.
96
Tylosin
This antibiotic is a nonpolyene macrolide, as are the clinically useful antibiotics erythromycin, oleandomycin, and others. It is more inhibitory than nisin or subtilin. Denny et al.
41 were apparently the first
to study its possible use in canned foods. When 1 ppm was added to cream-style corn containing flatsour spores and given a “botulinal” cook, no spoilage of product occurred after 30 days with incubation
at 54
◦ C.
41 Similar findings were made by others in the 1960s, and these have been summarized.
41
Unlike nisin, subtilin, and natamycin, tylosin is used in animal feeds and also to treat some diseases
of poultry. As a macrolide, it is most effective against Gram-positive bacteria. It inhibits protein
synthesis by associating with the 50S ribosomal subunit and shows at least partial cross-resistance
with erythromycin.
ANTIFUNGAL AGENTS FOR FRUITS
Listed in Table 13–10 are some compounds applied to fruits after harvest to control fungi, primarily
molds. Benomyl is applied uniformly over the entire surface of fruits (examples are noted in Table
13–10). It is applied at concentrations of 0.5–1.0 g/l. It can penetrate the surface of some vegetables and
is used worldwide to control crown rot and anthracnose of bananas, and stem-end rots of citrus fruits. It
is more effective than thiabendazole and penetrates with greater ease. Both benomyl and thiabendazole
are effective in controlling dry rot caused by Fusarium spp. To prevent the spread of Botrytis from