materials and dissolve mineral scale deposits
including those formed from using alkaline
cleaning compounds or other cleaners. A
portion of the minerals found in water may
be deposited when heated to 80 ̊C or higher
and adhere to metal surfaces and appear as a
rusty or whitish scale. Activity of acid clean-
ers is expressed through chemical action with
minerals found in deposits, making them
water soluble and easy to remove.
Organic acids, such as citric, tartaric, sul-
famic, and gluconic acid, are also excellent
water softeners, rinse easily, and are not cor-
rosive or irritating to the skin. Although
inorganic acids are excellent for removing
and controlling mineral deposits, they can be
extremely corrosive and irritating to the skin.
Acid cleaning compounds are a specialized
type of cleaner and are not recognized as
effective, all-purpose cleaning compounds.
They are not nearly as effective against soil
caused by fats, oils, and proteins, which acts
as a binder, as are alkaline cleaning com-
pounds. Alkaline cleaning compounds
chemically attack the binder of organic soils,
which releases the retaining or tenacious
forces. Acid cleaning compounds are not
capable of this function.
Strongly Acid Cleaners
These compounds are corrosive to con-
crete, most metals, and fabrics. Some of
these cleaners, when heated, produce corro-
sive, toxic gases, which can ulcerate lungs.
Strongly acid cleaners are used in cleaning
operations to remove the encrusted surface
matter and mineral scale frequently found on
steam-producing equipment, boilers, and
some processing equipment. When the solu-
tion temperature is too high, the mineral
scale may redeposit and form a tarnish or
whitish film on the equipment being cleaned.
Strongly acid agents used for cleaning
operations in food plants are hydrochloric
(muriatic), hydrofluoric, sulfamic, sulfuric,
and phosphoric acids. Nitric and sulfuric
acids are not used in manual cleaners
because of their corrosive properties. Corro-
sion inhibitors, such as potassium chromate
for nitric acid solutions or butylamine for
hydrochloric acid detergents, may be added.
Phosphoric acid and hydrofluoric acid
both clean and brighten certain metals.
However, hydrofluoric acid is corrosive to
stainless steel and dangerous to handle
because of the tendency toward hydrogen150 PRINCIPLES OFFOODSANITATION
Table 9–5Cleaning Characteristics of Commonly Used Alkaline Cleaning Compounds
pH of 0.5% Emulsifying
Alkaline Detergent Solution Detergency* Corrosiveness* Property*Sodium hydroxide (caustic soda) 12.7 2.5 3.5 2.0
Sodium orthosilicate 12.6 3.0 4.0 3.0
Sodium sesquisilicate 12.6 2.0 3.2 2.5
Sodium metasilicate 12.0 3.8 0.8 4.0
Trisodium phosphate 11.8 3.5 4.0 3.5
Sodium carbonate (Soda ash) 11.3 1.5 4.0 2.8
Tetrasodium pyrophosphate 10.1 3.5 3.0 0.0
Sodium sesquicarbonate 9.7 1.3 3.2 2.5
Sodium tripolyphosphate 8.8 2.0 2.0 0.0
Sodium tetraphosphate 8.4 3.0 1.0 0.0
Sodium bicarbonate 8.2 1.5 2.3 1.5
*Based on a 4.0 scale, where 0 = no property and 4 = excellent property.