Principles of Food Sanitation

on a cutting board, lubricant deposits on a
moving conveyor belt, and other organic
deposits on processing equipment.
Soils can be classified according to the
method of removal from the object to be
cleaned:
Soils soluble in water (or other solvents)
containing no cleaner: These soils will dissolve
in tap water and in other solvents that do not
contain a cleaning compound. They include
many inorganic salts, sugars, starches, and
minerals. Soils of this type present no techni-
cal problem because their removal is merely a
dissolving action.
Soils soluble in a cleaning solution that con-
tains a solubilizer or detergent:Acid-soluble
soils are soluble in acidic solutions with a pH
below 7.0. Deposits include films of oxidized
iron (rust), zinc carbonates, calcium oxalates,
metal oxides (iron and zinc) on stainless
steel, waterstone (reaction between various
alkaline cleaners and chemical constituents
of water having noncarbonate hardness),
hard-water scale (calcium and magnesium
carbonates), and milkstone (a waterstone
and milk film interaction, precipitated by
heat on a metal surface).Alkali-soluble soils
are basic media with a pH above 7.0. Fatty
acids, blood, proteins, and other organic
deposits are solubilized by an alkaline solu-
tion. Under alkaline conditions, a fat reacts
with the alkali to form soap. This reaction is
calledsaponification. The soap formed from

the reaction is soluble and will act as a solu-

bilizer and dispersant for the remaining soil.

Soils insoluble in the cleaning solution:

These soils are insoluble throughout the

range of normal cleaning solutions. How-

ever, they must be loosened from the surface

on which they are attached and subsequently

suspended in the cleaning media.

A soil that falls into one class for one type

of cleaning compound may fit in another

class if another cleaner is applied. For exam-

ple, sugar is soluble in water when an aqueous

detergent system is used but it is insoluble in

the organic solvents used in the dry-cleaning

industry and, therefore, falls in another class.

It is important to select the appropriate sol-

vent and the correct cleaning compound for

removing a specific soil. Table 9–1 summa-

rizes the solubility characteristics of various

kinds of soil. Soils are further classified as

inorganic soils. An acid-cleaning compound is

most appropriate for the removal of inorganic

deposits. An alkaline cleaner is more effective

in removing organic deposits. If these classes

are subdivided, it is easier to determine the

specific characteristics of each type of soil

and the most effective cleaning compound.

Table 9–2 gives a breakdown of soil sub-

classes, with examples of certain deposits.

Soil deposits are characteristically complex

in nature and are frequently complicated by

organic soils being protected by deposits of

inorganic soils, and vice versa. Therefore, it is

142 PRINCIPLES OFFOODSANITATION

Table 9–1Solubility Characteristics of Various Soils

Solubility Removal Changes Induced by Heating

Type of Salt Characteristics Ease the Surface

Monovalent Water-soluble, Easy to Inter-action with other constituents
Salts acid-soluble difficult with removal difficulty
Sugar Water-soluble Easy Carmelization and removal difficulty
Fat Water-insoluble, Difficult Polymerization and removal
alkali-soluble difficulty
Protein Water-insoluble, slightly Very Denturation and difficulty in
acid-soluble, alkali-soluble Difficult removal