Control by Antimicrobial Preservatives and Bacteriophages ◾ 499
cloves, allspice, and cinnamon; linalool in coriander; allicin in garlic; limonene from lime; and thymol
in oregano and thyme (see Table 38.3 for more compounds and their antimicrobial spectrum). Their
bacteriostatic and fungistatic properties depend on the active agent. Because of the small amounts used
as spices in foods, they probably do not produce any antimicrobial effects. However, the antimicrobial
components can be used in higher concentrations as oleoresins or essential oils.
The antimicrobial properties of garlic, onion, and ginger, as well as cabbage, Brussels sprouts,
carrots, and others have generated interest for their possible use as natural preservatives. There is
an increased interest in using “natural” or “green” antimicrobial compounds as food preservatives,
such as those from food plants and spices, and further studies are underway to determine their
delivery and efficacy in foods and beverages.
Wood Smoke
Many processed-meat products and fishes are processed with smoke generated by burning hardwood, such as hickory, oak, maple, walnut, and mahogany. As an alternative, liquid smoke,
obtained as a distillate of hardwood smoke, is also used with the ingredients of the products. The
main reason for smoking meat, fish, and cheese is to impart desirable flavor, texture, and color to
the products. The other benefit is the long shelf life of smoked products, especially those exposed
to smoke during heating. The smoke contains several different types of chemicals that deposit on
the food surface, many of which have antibacterial properties. The most important antibacterial
agents are formaldehyde, phenols, and cresols. Depending on the temperature and time of heating, degree of surface drying (A W ), and the concentrations, smoking can be both bacteriostatic
and bactericidal to bacterial cells. Although smoke has a slight antifungal action, it does not have
any adverse effects on the survival or germination of bacterial spores. Liquid smoke, under similar
conditions, is less antimicrobial than wood smoke. Smoke also contains some chemicals that are
carcinogenic, such as benzopyrene and dibenzanthracene. One of the recommendations to reduce
colon cancer is to minimize the consumption of foods treated with smoke.
Bacteriophages 1,11,12
Bacteriophages are viruses that infect bacteria (see Chapter 14). They are highly specific for a
bacterium, multiply inside and either lyse the bacterial cell or are maintained as a prophage. They
are now used to control foodborne bacterial pathogens and spoilage bacteria in live animals, meat,
dairy products, seafoods, and fresh produce. They are the most abundant form of life (10 31 phages)
on the planet. These viruses are very small (20–200 nm) and are categorized based on their shape:
tailed, polyhedral, filamentous, and pleomorphic. A majority of viruses are tailed (96%) virus. A
typical tailed bacteriophage possesses a head, tail, and tail fibers (Figure 38.1). The head contains
the genome, consisting of double-stranded or single-stranded DNA or RNA and protected by
capsid protein. The tail is a hollow tube through which nucleic acids (DNA or RNA) are transferred to the host during infection. Bacteriophages may transfer virulence genes from one bacterial pathogen to others. The tail fiber interacts with the host (bacterium) and provides specificity.
Bacteriophages do not infect humans or animals; thus they are considered suitable, especially the
lytic bacteriophages, for treatment of bacterial infection, to prevent pathogen colonization in meat
animals, and as “biocontrol” for use in the food industry. Historically, bacteriophages had been
used as therapeutic agents to control varieties of bacterial diseases in humans. First, therapeutic
use was reported in 1919 by Felix d’Herell, who used phages to control bacillary dysentery and
cloves, allspice, and cinnamon; linalool in coriander; allicin in garlic; limonene from lime; and thymol
in oregano and thyme (see Table 38.3 for more compounds and their antimicrobial spectrum). Their
bacteriostatic and fungistatic properties depend on the active agent. Because of the small amounts used
as spices in foods, they probably do not produce any antimicrobial effects. However, the antimicrobial
components can be used in higher concentrations as oleoresins or essential oils.
The antimicrobial properties of garlic, onion, and ginger, as well as cabbage, Brussels sprouts,
carrots, and others have generated interest for their possible use as natural preservatives. There is
an increased interest in using “natural” or “green” antimicrobial compounds as food preservatives,
such as those from food plants and spices, and further studies are underway to determine their
delivery and efficacy in foods and beverages.
Wood Smoke
Many processed-meat products and fishes are processed with smoke generated by burning hardwood, such as hickory, oak, maple, walnut, and mahogany. As an alternative, liquid smoke,
obtained as a distillate of hardwood smoke, is also used with the ingredients of the products. The
main reason for smoking meat, fish, and cheese is to impart desirable flavor, texture, and color to
the products. The other benefit is the long shelf life of smoked products, especially those exposed
to smoke during heating. The smoke contains several different types of chemicals that deposit on
the food surface, many of which have antibacterial properties. The most important antibacterial
agents are formaldehyde, phenols, and cresols. Depending on the temperature and time of heating, degree of surface drying (A W ), and the concentrations, smoking can be both bacteriostatic
and bactericidal to bacterial cells. Although smoke has a slight antifungal action, it does not have
any adverse effects on the survival or germination of bacterial spores. Liquid smoke, under similar
conditions, is less antimicrobial than wood smoke. Smoke also contains some chemicals that are
carcinogenic, such as benzopyrene and dibenzanthracene. One of the recommendations to reduce
colon cancer is to minimize the consumption of foods treated with smoke.
Bacteriophages 1,11,12
Bacteriophages are viruses that infect bacteria (see Chapter 14). They are highly specific for a
bacterium, multiply inside and either lyse the bacterial cell or are maintained as a prophage. They
are now used to control foodborne bacterial pathogens and spoilage bacteria in live animals, meat,
dairy products, seafoods, and fresh produce. They are the most abundant form of life (10 31 phages)
on the planet. These viruses are very small (20–200 nm) and are categorized based on their shape:
tailed, polyhedral, filamentous, and pleomorphic. A majority of viruses are tailed (96%) virus. A
typical tailed bacteriophage possesses a head, tail, and tail fibers (Figure 38.1). The head contains
the genome, consisting of double-stranded or single-stranded DNA or RNA and protected by
capsid protein. The tail is a hollow tube through which nucleic acids (DNA or RNA) are transferred to the host during infection. Bacteriophages may transfer virulence genes from one bacterial pathogen to others. The tail fiber interacts with the host (bacterium) and provides specificity.
Bacteriophages do not infect humans or animals; thus they are considered suitable, especially the
lytic bacteriophages, for treatment of bacterial infection, to prevent pathogen colonization in meat
animals, and as “biocontrol” for use in the food industry. Historically, bacteriophages had been
used as therapeutic agents to control varieties of bacterial diseases in humans. First, therapeutic
use was reported in 1919 by Felix d’Herell, who used phages to control bacillary dysentery and