Fundamental Food Microbiology, Third Edition - Fuad Fathir

504 FUNDAMENTAL FOOD MICROBIOLOGY
enhances the thermal inactivation of spores of Bacillus spp. The antimicrobial
property of this lipophilic compound is enhanced with lactate, sorbate, ascorbate,
and nisin, but may be reduced by starchy and proteinaceous compounds. In combination
with monolaurin, the fungistatic activity of several antifungal compounds is
enhanced. The antimicrobial activity of monolaurin is produced through its ability
to destabilize the functions of the membrane. At lower concentrations, it is bacteriostatic
by interfering with the uptake of nutrients. It can be used up to 500 ppm
without affecting the taste of the food.
O. Antibiotics (Tetracyclines, Natamycin, and Tylosin)
Several classical antibiotics that do not include bacteriocins of Gram-positive bacteria
(such as nisin, pediocin, sakacin, and subtilin) were studied as antimicrobial
food preservatives. Tetracyclines (ca. 10 ppm) were approved by the Food and Drug
Administration (FDA) to extend the refrigerated shelf life of seafood and poultry in
the 1950s. However, because of the possible increase in antibiotic-resistant bacteria,
the use of these antibiotics in food was later banned. Natamycin, a microlid produced
by Streptomyces natalensis, is an antifungal agent. Its use as a dip or spray to prevent
growth of molds and formation of mycotoxins on the surface of some cheeses,
sausages, and in raw peanuts has been approved by the Expert Committee of the
World Health Organization (WHO). It is customarily used at 500 ppm, which leaves
detectable but safe levels of the antibiotic on the product surface. Tylosin, a microlid
that inhibits protein synthesis, is a bactericidal antibiotic that is more effective against
Gram-positive than Gram-negative bacteria and also inhibits outgrowth of germinated
endospores. Because of its high heat resistance, it has been studied at a low
concentration (1 ppm) to determine its effectiveness in controlling the growth of
sporeformers in low-acid canned products.
P. 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.