charged ion (cation). In these quaternary
ammonium compounds, the organic radical
is the cation, and chlorine is usually the
anion. The mechanism of germicidal action
is not fully understood but may be that the
surface-active nature of the quat surrounds
and covers the cell’s outer membrane, caus-
ing a failure of the wall, which consequently
causes leakage of the internal organs and
enzyme inhibition. The general formula of
the quaternary ammonium compound is:
R 2R 1 N ̈
̈R 3 Cl−or BR−
R 4The quats act against microorganisms dif-
ferently than do chlorine and iodine com-
pounds. They form a residual antimicrobial
film after being applied to surfaces. Although
the film is bacteriostatic, these compounds
are selective in the destruction of various
microorganisms. The quats do not kill bacte-
rial spores but can inhibit their growth. Qua-
ternary ammonium compounds are more
stable in the presence of organic matter than
are chlorine and iodine sanitizers, although
their bactericidal effectiveness is impaired by
the presence of organic matter. Stainless steel
and polycarbonate are more readily sanitized
by the quats than are either the abraded poly-
carbonate or mineral resin surfaces (Frank
and Chmielewski, 1997).
The quaternary ammonium compounds
include alkyldimethylbenzylammonium chlo-
ride and alkyldimethylethylbenzylammo-
nium chloride, both effective in water ranging
from 500 to 1,000 ppm hardness without
added sequestering agents. Diisobutylphen-
oxyethoxyethyl dimethyl benzyl ammonium
chloride and methyldodecylbenzyltrimethyl
ammonium chloride are compounds that
require sodium tripolyphosphate to raise
hard-water levels to a minimum of 500 ppm.
These compounds require high dilution for
germicidal or bacteriostatic action. As with
other quats, these are nonconcorrosive and
nonirritating to the skin, and have no taste or
odor in use dilutions. The concentration of
quat solutions is easy to measure. The quats
are low in toxicity and can be neutralized or
made ineffective by using any anionic deter-
gent. Quat sanitizers are generally more effec-
tive in the alkaline pH range. However the
effect of pH may vary with bacterial species,
with gram-negative bacteria being more sus-
ceptible to quats in the acid pH range and
gram-positive microbes in the alkaline range.
Quats have surfactants that cause them to
foam (Carsberg, 1996). They can be
“foamed” on, which provides a medium for
them to cling to vertical and radial surfaces.
When formulated with a specified detergent,
they can be used as a cleaner-sanitizer. How-
ever, this application requires rinsing,
although it is satisfactory for bathrooms,
toilets, locker rooms, and other non-food-
contact surfaces. These cleaner-sanitizers
are not recommended for use in the food
plant environment because there are insuffi-
cient detergent properties and pH or alka-
linity levels to thoroughly clean. Because
rinsing of this cleaner-sanitizer is required,
there is no residual antibacterial activity on
the surface.
The quaternary ammonium compounds
should not be combined with cleaning com-
pounds for subsequent cleaning and sanitiz-
ing because they are inactivated through
detergent ingredients such as anionic wetting
agents (see Chapter 9). However, an increase
in alkalinity through formulation with com-
patible detergents may enhance the bacterici-
dal activity of the quats.
The quats have the following major advan-
tages (Anon., 1997):●Colorless and odorless
●Stable against reaction with organic
matterSanitizers 177