Principles of Food Sanitation

rinse of cold water may be alternated
between the acid and alkaline cleaners.
Cream and ice cream processing equipment.
These products, which contain a higher per-
centage of fat and a lower percentage of
minerals, can be cleaned more effectively if
an alkaline cleaner is first recirculated for
approximately 30 minutes. The concentra-
tion of the alkaline solution may range from
0.5% to 1.5% causticity. The acid is generally
added to produce a pH of 2.0 to 2.5. A prac-
tical rule of thumb is to use a cleaning solu-
tion temperature during the recirculating
period that is adjusted to approximately 5°C
higher than the maximum processing tem-
perature used during the production shift.

Cheesemaking Area and Equipment

The two main types of spoilage of hard and
semihard varieties of cheese are surface
growth of microorganisms (usually molds)
and gas production of microorganisms grow-
ing in the body of cheese.Penicilliumaccounts
for up to 80% of spoilage cases, and other
common spoilage species are Alternaria,
Aspergillus, Candida, Monilia, and Mucor.
Mold spoilage reduction may be accom-
plished through sterile filtration of air, ultra-
violet disinfection of handling surfaces, ozone
treatment, and antimycotic coating of pack-
aging material. The spraying of chemical dis-
infectants in the air is a routine practice for
mold control (Holah et al., 1995).Enterobac-
teriaceae,Bacillus,Clostridium, and Candida

are some common microorganisms responsi-

ble for gas production. According to Varnam

and Sutherland (1994), soft cheeses can be

affected by gram-negative bacteria, such as

Pseudomonas fluorescens, P. putida, and

Enterobacter agglomerans; by diarrheagenic

strains of E. coli, which come from wash

water or added ingredients; and by gram-

positive bacteria, such as L. monocytogenes.

Milk should be stored in tanks con-

structed with materials and designs that are

easy to clean. However, silo tanks that are

large and cannot be cleaned using normal

cleansing methods should be equipped with

CIP methods and cleaned every time that

they are emptied. They should be rinsed with

water to remove gross soils and washed with

detergent solutions, rinsed, and sterilized.

Acid solutions should be incorporated when

tank materials permit their use. Chemical

sterilization is the preferred method, and

steam sterilization should be avoided.

As with other dairy processing plants, pip-

ing should be carefully laid out to prevent

cross-contamination between pasteurized

and unpasteurized milk. Separate CIP

equipment should be provided for both

products. Cleaning and sterilization can be

achieved through circulating materials such

as sodium hydroxide and nitric acid (Varnam

and Sutherland, 1994).

Brine tanks should be lined with a noncor-

rosive material, such as tiles or plastics. Brines

should be maintained at the correct strength

Dairy Processing Plant Sanitation 295

Table 16–3Typical Concentrations for Various Cleaning Applications

Chlorinated Acid/Acid
Cleaning Anionic Chlorine
Cleaning Applications Compounds (ppm) Sanitizers (ppm)

Milk storage and transportation tanks 1,500–2,000 100
Cream, condensed milk, and ice cream storage tanks 2,500–3,000 100–130
Processing vessels for moderate heat treatment 4,000–5,000* 100–200
Heavy “burn-on” 0.75–1.0% Acid wash at pH
(causticity) 2.0–2.5

*An acid rinse after cleaning should be considered.