Principles of Food Sanitation

Soil attachment characteristics

Soils deposited in cracks, crevices, and
other uneven areas are difficult to remove,
especially in hard-to-reach areas. Ease of soil
removal from a surface depends on surface
characteristics such as smoothness, hardness,
porosity, and wettability. Soil removal from a
surface consists of three sub-processes.
First is separation of the soil from the sur-
face,material, or equipment to be cleaned.
Soil separation can occur through mechanical
action of high-pressure water, steam, air, and

scrubbing; through alteration of the chemical

nature of soil (e.g., reaction of an alkali with

a fatty acid to form a soap); or without alter-

ation of the chemical nature of the soil (e.g.,

surfactants that reduce surface tension of the

cleaning medium, such as water, to allow

more intimate contact with the soil).

The soil and surface must be thoroughly

wet for a cleaning compound to aid in sepa-

rating the soil from the surface. The cleaning

compound reduces the energy binding the

soil to a surface, permitting the soil to be

loosened and separated. The effectiveness of

energy reduction and reduced binding may

144 PRINCIPLES OFFOODSANITATION

Table 9–4Characteristics of Various Surfaces of Food Processing Plants

Material Characteristics Precautions

Wood Previous to moisture, fats, and oils; Wood should not be used because of
difficult to maintain; soften by its unsanitary features. Stainless
alkali; destroyed by caustics. steel, polyethylene, and rubber
materials should be used instead
of wood.
Black Metals Rust may be promoted by acidic Because these metals are prone to
acid chlorinated detergents. rust, they are often tinned or galva-
nized. Neutral detergents should be
used in cleaning these surfaces.
Tin May be corroded by strong alkaline Tin surfaces should not come in
and acid cleaners. contact with foods.
Concrete May be etched by acid foods and Concrete should be dense, acid-
cleaning compounds. resistant, and nondusting. Acid brick
may be used in place of concrete.
Glass Smooth and impervious; may be Glass should be cleaned with
etched by strong alkaline moderately alkaline or neutral
cleaning compounds. detergents.
Paint Surface quality depends on the Certain edible paints are satisfactory
method of application etched for food plants.
by strong alkaline cleaning
compounds.
Rubber Should be nonporous, nonspongy; Rubber cutting boards can warp, and
not affected by alkaline detergents; their surface dulls knife blades.
is attacked by organic solvents
and strong acids.
Stainless Steel Generally resistant to corrosion; Stainless steel is expensive and may
smooth-surfaced and impervious be less plentiful in the future. Certain
(unless corrosion occurs); resistant varieties are attacked by halogens
to oxidation at high temperatures; (chlorine, iodine, bromine, and
easily cleaned; nonmagnetic). fluorine).