evolution during use. Phosphoric acid is
widely used in the United States. It is rela-
tively low in corrosive properties, compatible
with many surfactants, and is used in manual
and heavy-duty formulations.
Mildly Acid Cleaners
These compounds are mildly corrosive and
may cause allergenic reactions. Some acid
cleaners attack skin and eyes. Examples of
mildly acid cleaning compounds are levulinic,
hydroxyacetic, acetic, and gluconic acids.
Wetting agents and corrosion inhibitors (i.e.,
2-naphtoquinoline, acridine, 9-phenylacri-
dine) may be added. The organic acids, which
are used as manual cleaning products, are
higher in cost than are the other acid cleaning
compounds. These mild compounds can also
function as water softeners.
Cleaners with Active Chlorine
Wyman (1996) reported that cleaners con-
taining active chlorine, such as sodium or
potassium hypochlorite, are effective in the
removal of carbohydrate and/or proteina-
ceous soils because they aggressively attack
such materials and chemically modify them
to render them more susceptible to interac-
tion with the balance of the components.
Active chlorine-containing products are
especially valuable when cleaning a surface
in which the soil is derived from a food
source comprised of some form of starch or
protein. Also, they are effective in removing
molds from surfaces.
Because of a form of chemical bonding
known as cross-linking, many carbohydrates
are such that a large number of the “big” mol-
ecules are bonded together. In this instance,
they cannot dissolve, which makes cleaning
them from a surface very difficult. According
to Wyman (1996), heat, history imparted
whenever carbohydrate-containing materials
are heated, increases the number or cross-
links and complicates cleaning. Active chlo-
rine-containing cleaners have the ability to
break chemical bonds, leading to the forma-
tion of smaller, more soluble molecules and
an increase in cleaning speed and efficacy.
Active chlorine, such as hypochlorite,
attacks the large, complex carbohydrate mol-
ecules and degrades them to smaller, more
soluble and readily removed derivatives.
Because active chlorine acts quickly, only
portions of the molecules need be modified
for the change in ease of removability to
occur. Small amounts of active chlorine give
effective cleaning results.
In the reaction of sodium hypochlorite
with carbohydrates, the former can reduce
the molecular weight of starch and increase
its solubility. As with most cases, the reac-
tion rates increase with elevated temperature.
Because hypochlorite is an effective biocide
at pH values lower than 8.5, the cleaning
reaction rate of this compound is faster at a
pH of 8 than at 10. A lower pH accounts for
more of the hypochlorite in the form of
hypochlorous acid, which diffuses into bac-
teria and carbohydrate residues faster than
the hypochlorite ion, to increase the cleaning
reaction rate.
Proteins are crosslinked by chemical bond-
ing and bonds that tie the large molecules
together. Hydrogen bonding occurs because
certain atoms in the molecule have a stronger
attraction for electrons than do others. This
reaction generates an electrostatic interac-
tion, which complicates the removal of pro-
teins by conventional means. Furthermore,
proteins can interact through hydrogen bond-
ing to decrease their solubility. Active chlo-
rine-containing cleaners react with the
insoluble proteins and render them soluble
and/or readily dispersible through degrada-
tion by rapid oxidation of sulfide crosslinks
that are present. Because the degradation
need not be complete for solubilization to
occur, a small amount of hypochlorite will
remove a relatively large quantity of protein.Cleaning Compounds 151